WorldWideScience

Sample records for low-energy electron emitters

  1. Low-energy, high-current, ion source with cold electron emitter

    Energy Technology Data Exchange (ETDEWEB)

    Vizir, A. V.; Oks, E. M. [High Current Electronics Institute, Russian Academy of Sciences, Tomsk 634055 (Russian Federation); State University of Control Systems and Radioelectronics, Tomsk 634050 (Russian Federation); Shandrikov, M. V.; Yushkov, G. Yu. [High Current Electronics Institute, Russian Academy of Sciences, Tomsk 634055 (Russian Federation)

    2012-02-15

    An ion source based on a two-stage discharge with electron injection from a cold emitter is presented. The first stage is the emitter itself, and the second stage provides acceleration of injected electrons for gas ionization and formation of ion flow (<20 eV, 5 A dc). The ion accelerating system is gridless; acceleration is accomplished by an electric field in the discharge plasma within an axially symmetric, diverging, magnetic field. The hollow cathode electron emitter utilizes an arc discharge with cathode spots hidden inside the cathode cavity. Selection of the appropriate emitter material provides a very low erosion rate and long lifetime.

  2. Monochromatic gamma emitter for low energy quanta

    CERN Document Server

    Tomova, Z R; Mironova, S A

    2004-01-01

    The possibility of creating of a monochromatic gamma emitter of low energy quanta is analyzed. The idea is based on Daning's scheme. Except for purely scientific problems the monochromator is actual for therapy of wide range of diseases.

  3. Space Charge Correction on Emittance Measurement of Low Energy Electron Beams

    Energy Technology Data Exchange (ETDEWEB)

    Treado, Colleen J.; /Massachusetts U., Amherst

    2012-09-07

    The goal of any particle accelerator is to optimize the transport of a charged particle beam along a set path by confining the beam to a small region close to the design trajectory and directing it accurately along the beamline. To do so in the simplest fashion, accelerators use a system of magnets that exert approximately linear electromagnetic forces on the charged beam. These electromagnets bend the beam along the desired path, in the case of bending magnets, and constrain the beam to the desired area through alternating focusing and defocusing effects, in the case of quadrupole magnets. We can model the transport of such a beam through transfer matrices representing the actions of the various beamline elements. However, space charge effects, produced from self electric fields within the beam, defocus the beam and must be accounted for in the calculation of beam emittance. We present below the preliminary results of a MATLAB code built to model the transport of a charged particle beam through an accelerator and measure the emittance under the influence of space charge effects. We demonstrate the method of correctly calculating the emittance of a beam under space charge effects using a least square fit to determine the initial properties of the beam given the beam size measured at a specific point after transport.

  4. Obtaining the high-current low-energy electron beams in the systems with a plasma emitter

    CERN Document Server

    Devyatkov, V N; Shchanin, P M

    2001-01-01

    Using gas filled diodes with arc and glow-discharge base plasma emitters one investigated into generation and transfer of high-current electron beams. Using a diode with arc discharge base plasma emitter at 15 kV accelerating voltage one obtained a space charge compensated with up to 1 kA current compressed by proper magnetic field from 8 cm diameter up to 1 cm and transported at over 20 cm distance with 70% efficiency. Using a diode with a glow-discharge one obtained a 80 A current and up to 100 A/cm current density beam. In a weak axial magnetic field with B=0.015 T induction such a beam is transported at 30 cm distance

  5. Low-energy electron beams through ultra-thin foils, applications for electron microscopy

    NARCIS (Netherlands)

    Van Aken, R.H.

    2005-01-01

    This thesis has discussed two electron microscopy applications that make use of ultra-thin foils: the tunnel junction emitter and the low-energy foil corrector. Both applications have in common that the electron beam is sent through the thin foil at low energy. Part of the electrons will scatter in

  6. Single track nanodosimetry of low energy electrons

    Energy Technology Data Exchange (ETDEWEB)

    Bantsar, A. [Soltan Institute for Nuclear Studies, 05-400 Otwock-Swierk (Poland); Grosswendt, B. [Physikalisch-Technische Bundesanstalt, 38116 Braunschweig (Germany); Pszona, S. [Soltan Institute for Nuclear Studies, 05-400 Otwock-Swierk (Poland)], E-mail: pszona@ipj.gov; Kula, J. [Soltan Institute for Nuclear Studies, 05-400 Otwock-Swierk (Poland)

    2009-02-11

    Auger-electron-emitting radionuclides (for instance, {sup 125}I) with a predominant energy spectrum below 3 keV are an active area of research towards the clinical application of radiopharmaceuticals. Hence, the necessity for an adequate description of the effects of radiation by low-energy electrons on nanometric biological targets seems to be unquestionable. Experimental nanodosimetry for low-energy electrons has been accomplished with a device named JET COUNTER. The present paper describes, for the first time, nanodosimetric experiments in nanometer-sized cavities of nitrogen using low energy electrons ranging from 100 eV to 2 keV.

  7. Single track nanodosimetry of low energy electrons

    Science.gov (United States)

    Bantsar, A.; Grosswendt, B.; Pszona, S.; Kula, J.

    2009-02-01

    Auger-electron-emitting radionuclides (for instance, 125I) with a predominant energy spectrum below 3 keV are an active area of research towards the clinical application of radiopharmaceuticals. Hence, the necessity for an adequate description of the effects of radiation by low-energy electrons on nanometric biological targets seems to be unquestionable. Experimental nanodosimetry for low-energy electrons has been accomplished with a device named JET COUNTER. The present paper describes, for the first time, nanodosimetric experiments in nanometer-sized cavities of nitrogen using low energy electrons ranging from 100 eV to 2 keV.

  8. Emittance Scanner Optimization for Low Energy Ion Beams

    CERN Document Server

    Stockli, Martin P

    2005-01-01

    Ion beam emittances are normally measured as two-dimensional distributions of the beam current fraction within a window dx centered at position coordinate x and a window dx' centered at trajectory angle x'. Unthresholded rms emittances evaluated from experimental data are very sensitive to noise, bias, and other undesired signals. Undesired signals occur when particles from outside the measured window dx*dx' contribute to the signal from the particles within the measured window. Increasing the window size increases the desired signal while most undesired contributions remain unchanged. However, the decreasing resolution causes an error in the emittance results, especially in the rms emittance. Using theoretical distributions we will present the tradeoff between resolution and accuracy.

  9. Gas Electron multipliers for low energy beams

    CERN Document Server

    Arnold, F; Ropelewski, L; Spanggaard, J; Tranquille, G

    2010-01-01

    Gas Electron Multipliers (GEM) find their way to more and more applications in beam instrumentation. Gas Electron Multiplication uses a very similar physical phenomenon to that of Multi Wire Proportional Chambers (MWPC) but for small profile monitors they are much more cost efficient both to produce and to maintain. This paper presents the new GEM profile monitors intended to replace the MWPCs currently used at CERN’s low energy Antiproton Decelerator (AD). It will be shown how GEMs overcome the documented problems of profile measurements with MWPCs for low energy beams, where the interaction of the beam with the detector has a large influence on the measured profile. Results will be shown of profile measurements performed at 5 MeV using four different GEM prototypes, with discussion on the possible use of GEMs at even lower energies needed at the AD in 2013.

  10. Low energy electron scattering from fuels

    Energy Technology Data Exchange (ETDEWEB)

    Lopes, M. Cristina A.; Silva, Daniel G.M.; Coelho, Rafael F.; Duque, Humberto V.; Santos, Rodrigo R. dos; Ribeiro, Thiago M. [Universidade Federal de Juiz de Fora (UFJF), MG (Brazil). Dept. de Fisica; Yates, Brent; Hong, Ling; Khakoo, Murtadha A. [California State University at Fullerton, CA (US). Physics Department; Bettega, Marcio H.F. [Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil). Dept. de Fisica; Costa, Romarly F. da [Universidade Federal do ABC (UFABC), Santo Andre, SP (Brazil). Centro de Ciencias Naturais e Humanas; Lima, Marco A.P. [Laboratorio Nacional de Ciencia e Tecnologia do Bioetanol (CTBE/CNPEM), Campinas, SP (Brazil)

    2011-07-01

    Full text. Accurate and precise values of absolute total cross section (TCS) represent important information in many scientific and technological applications. In our case, for example, we are motivated to provide such information for electron-fuel collision processes which are specifically relevant to modeling spark ignition in alcohol-fuelled internal combustion engines. Many electron scattering TCS measurements are presently available for a diverse range of atomic and molecular targets. However, lack of data for important bio-molecular targets still remains. Disagreements between the available TCS data for the alcohols have prompted several studies of electron scattering collision of slow electrons with these molecules which are currently important in applications as bio- fuels. This relevance, which has attracted much attention, has been one of the subjects of a recent collaboration between experimental and theoretical groups in the USA and Brazil. Recently this collaboration reported first measurements and calculations of differential cross sections for elastic low-energy (rotationally unresolved) electron scattering by several primary alcohols. In this work we address methanol and ethanol TCSs at low energy range and report additional studies of resonant structure in ethanol using the detection of metastable states produced by electron impact excitation with high energy resolution. We have recently constructed a TCS apparatus in our laboratory at Universidade Federal de Juiz de Fora, Brazil, based on the well-known linear transmission technique. The experimental setup is based on the measurement of the attenuation of a collimated electron beam through a gas cell containing the atoms or molecules to be studied at a given pressure. It consists essentially of an electron gun, a gas cell and an electron energy analyzer composed of an array of decelerating electrostatic lenses, a cylindrical dispersive 127o analyzer and a Faraday cup. To our knowledge, there exist

  11. Low-energy electron scattering from cyanamide

    Science.gov (United States)

    Wang, Kedong; Guo, Shuangcheng; Meng, Ju; Huang, Xiaotian; Wang, Yongfeng

    2016-09-01

    The low-energy electron collisions with cyanamide molecule are investigated by using the UK molecular R -matrix codes for electron energies ranging from 0.01 eV to 10 eV. Three models including static-exchange, static-exchange plus polarization, and close-coupling (CC) approximations are employed to reveal the dynamic interaction. Elastic (integrated and differential), momentum-transfer, and excitation cross sections from the ground state to the three low-lying electron excited states have been presented. Two shape resonances, two core-excited resonances, and two Feshbach resonances are detected in the CC approximation. The role of active space in the target and scattering problem including the resonances is discussed. The precise resonance parameters are found to be sensitive to the treatment of polarization effects employed. These resonances may be responsible for the fragments observed in a recent experiment of the dissociative electron attachments to cyanamide. Since the cyanamide molecule has a large permanent dipole moment, a Born closure procedure is used to account for the contribution of partial waves higher than l =4 to obtain converged cross sections.

  12. Low energy electron transport in furfural

    Science.gov (United States)

    Lozano, Ana I.; Krupa, Kateryna; Ferreira da Silva, Filipe; Limão-Vieira, Paulo; Blanco, Francisco; Muñoz, Antonio; Jones, Darryl B.; Brunger, Michael J.; García, Gustavo

    2017-09-01

    We report on an initial investigation into the transport of electrons through a gas cell containing 1 mTorr of gaseous furfural. Results from our Monte Carlo simulation are implicitly checked against those from a corresponding electron transmission measurement. To enable this simulation a self-consistent cross section data base was constructed. This data base is benchmarked through new total cross section measurements which are also described here. In addition, again to facilitate the simulation, our preferred energy loss distribution function is presented and discussed.

  13. Electric field distribution of electron emitter surfaces

    Science.gov (United States)

    Tagawa, M.; Takenobu, S.; Ohmae, N.; Umeno, M.

    1987-03-01

    The electric field distribution of a tungsten field emitter surface and a LaB6 thermionic emitter surface has been studied. The computer simulation of electric field distribution on the emitter surface was carried out with a charge simulation method. The electric field distribution of the LaB6 thermionic emitter was experimentally evaluated by the Schottky plot. Two independent equations are necessary for obtaining local electric field and work function; the Fowler-Nordheim equation and the equation of total energy distribution of emitted electron being used to evaluate the electric field distribution of the tungsten field emitter. The experimental results agreed with the computer simulation.

  14. Low energy electron microscopy imaging using Medipix2 detector

    NARCIS (Netherlands)

    Sikharulidze, I.; Gastel, van R.; Schramm, S.; Abrahams, J.P.; Poelsema, B.; Tromp, R.M.; Molen, van der S.J.

    2011-01-01

    Low Energy Electron Microscopy (LEEM) and Photo-Emission Electron Microscopy (PEEM) predominantly use a combination of microchannel plate (MCP), phosphor screen and optical camera to record images formed by 10–20 keV electrons. We have tested the performance of a LEEM/PEEM instrument with a Medipix2

  15. Low Emittance Electron Beam Studies

    Energy Technology Data Exchange (ETDEWEB)

    Tikhoplav, Rodion [Univ. of Rochester, NY (United States)

    2006-01-01

    We have studied the properties of a low emittance electron beam produced by laser pulses incident onto an rf gun photocathode. The experiments were carried out at the A0 photoinjector at Fermilab. Such beam studies are necessary for fixing the design of new Linear Colliders as well as for the development of Free Electron Lasers. An overview of the A0 photoinjector is given in Chapter 1. In Chapter 2 we describe the A0 photoinjector laser system. A stable laser system is imperative for reliable photoinjector operation. After the recent upgrade, we have been able to reach a new level of stability in the pulse-to-pulse fluctuations of the pulse amplitude, and of the temporal and transverse profiles. In Chapter 3 we present a study of transverse emittance versus the shape of the photo-cathode drive-laser pulse. For that purpose a special temporal profile laser shaping device called a pulse-stacker was developed. In Chapter 4 we discuss longitudinal beam dynamics studies using a two macro-particle bunch; this technique is helpful in analyzing pulse compression in the magnetic chicane, as well as velocity bunching effects in the rf-gun and the 9-cell accelerating cavity. In Chapter 5 we introduce a proposal for laser acceleration of electrons. We have developed a laser functioning on the TEM*01 mode, a mode with a longitudinal electric field component which is suitable for such a process. Using this technique at energies above 40 MeV, one would be able to observe laser-based acceleration.

  16. Electron polarimetry at low energies in Hall C at JLab

    Energy Technology Data Exchange (ETDEWEB)

    Gaskell, D. [Thomas Jefferson National Accelerator Facility, Newport News, Virginia, 23606 (United States)

    2013-11-07

    Although the majority of Jefferson Lab experiments require multi-GeV electron beams, there have been a few opportunities to make electron beam polarization measurements at rather low energies. This proceedings will discuss some of the practical difficulties encountered in performing electron polarimetry via Mo/ller scattering at energies on the order of a few hundred MeV. Prospects for Compton polarimetry at very low energies will also be discussed. While Mo/ller scattering is likely the preferred method for electron polarimetry at energies below 500 MeV, there are certain aspects of the polarimeter and experiment design that must be carefully considered.

  17. Electronic excitation of molecular hydrogen by low-energy electrons

    Science.gov (United States)

    Hargreaves, Leigh

    2016-09-01

    Molecular hydrogen is the most abundant element in the universe, particularly in interstellar plasmas such as atmospheres of gas giant planets and stars. Electron collision data for hydrogen is critical to interpreting the spectroscopy of interstellar objects, as well as being of applied value for modelling technological plasmas. Hydrogen is also fundamentally interesting, as while highly accurate wave functions for this simple molecule are available, providing an accurate, ab initio, treatment the collision dynamics has proven challenging, on account of the need to have a complete description of channel coupling and polarization effects. To date, no single theoretical approach has been able to replicate experimental results across all transitions and incident energies, while the experimental database that is available is far from complete and not all available measurements are in satisfactory agreement. In this talk, we present differential and integral cross section measurements for electronic excitation cross sections for molecular hydrogen by low-energy electron impact. The data were measured at incident energies below 20eV, using a well-tested crossed beam apparatus and employing a moveable gas source approach to ensure that background contributions to the scattering are accurately accounted for. These measurements are compared with new theoretical results employing the convergent close coupling approach.

  18. Medipix 2 detector applied to low energy electron microscopy

    NARCIS (Netherlands)

    Gastel, van R.; Sikharulidze, I.; Schramm, S.; Abrahams, J.P.; Poelsema, B.; Tromp, R.M.; Molen, van der S.J.

    2009-01-01

    Low energy electron microscopy (LEEM) and photo-emission electron microscopy (PEEM) traditionally use microchannel plates (MCPs), a phosphor screen and a CCD-camera to record images and diffraction patterns. In recent years, however, MCPs have become a limiting factor for these types of microscopy.

  19. Catalogue of Radionuclide Low-Energy Electron Spectra (LEES)

    CERN Document Server

    Vylov, T D; Kovalik, A; Yakushev, E A; Mahmoud, M; Novgorodov, A F; Lebedev, N A; Filossofov, D V; Briançon, C; Walen, R J; Coursol, N F; Minkova, A; Petev, P; Dragoun, O; Brabec, V; Inoyatov, A

    2003-01-01

    More than 100 of apparatus low-energy electron spectra from radionuclides with Z=24-95 are collected in the presented LEES Catalogue. These spectra have been recorded in systematical investigations of Auger and internal conversion electrons with the ESA-50 electrostatic spectrometer during past 20 years.

  20. Utilization of low-energy electron accelerators in Korea

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Byung Cheol [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    2003-02-01

    There are more than 20 electron accelerators in Korea. Most of those are installed in factories for heat-resistant cables, heat-shrinkable cables, radial tires, foams, tube/ films, curing, etc. Four low-energy electron accelerators are in operation for research purposes such as polymer modification, purification of flue gas, waste water treatment, modification of semiconductor characteristics, etc. (author)

  1. Specification of a new electron cooler for the low energy ion accumulator ring, LEIR

    CERN Document Server

    Tranquille, Gerard

    2004-01-01

    For the cooling of Pb**5**4**+ ions in the future low-energy ion ring machine a new electron cooling device needs to be constructed. This new cooler will take advantage of all the recent developments in electron cooling in order to balance efficient and fast cooling with a sufficiently long ion beam lifetime for beam accumulation. This paper will present the special features of the device and how their combination will be used to obtain low emittance beams for transfer to the LHC.

  2. A transverse emittance and acceptance measurement system in a low-energy beam transport line

    Energy Technology Data Exchange (ETDEWEB)

    Kashiwagi, H., E-mail: kashiwagi.hirotsugu@jaea.go.jp; Miyawaki, N.; Kurashima, S.; Okumura, S. [Department of Advanced Radiation Technology, Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan)

    2014-02-15

    A transverse beam emittance and acceptance measurement system has been developed to visualize the relationship between the injected beam emittance and the acceptance of a cyclotron. The system is composed of a steering magnet, two pairs of slits to limit the horizontal and vertical phase-space, a beam intensity detector just behind the slits for the emittance measurement, and a beam intensity detector in the cyclotron for the acceptance measurement. The emittance is obtained by scanning the slits and measuring the beam intensity distribution. The acceptance is obtained by measuring the distribution of relative beam transmission by injecting small emittance beams at various positions in a transverse phase-space using the slits. In the acceptance measurement, the beam from an ion source is deflected to the defined region by the slits using the steering magnet so that measurable acceptance area covers a region outside the injection beam emittance. Measurement tests were carried out under the condition of accelerating a beam of {sup 16}O{sup 6+} from 50.2 keV to 160 MeV. The emittance of the injected beam and the acceptance for accelerating and transporting the beam to the entrance of the extraction deflector were successfully measured. The relationship between the emittance and acceptance is visualized by displaying the results in the same phase-plane.

  3. Modelling low energy electron interactions for biomedical uses of radiation

    Energy Technology Data Exchange (ETDEWEB)

    Fuss, M; Garcia, G [Instituto de Fisica Fundamental, Consejo Superior de Investigaciones CientIficas (CSIC), Serrano 113-bis, 28006 Madrid (Spain); Munoz, A; Oller, J C [Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas (CIEMAT), Avenida Complutense 22, 28040 Madrid (Spain); Blanco, F [Departamento de Fisica Atomica, Molecular y Nuclear, Universidad Complutense de Madrid, Avenida Complutense s.n., 28040 Madrid (Spain); Limao-Vieira, P [Departamento de Fisica, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Huerga, C; Tellez, M [Hospital Universitario La Paz, paseo de la Castellana 261, 28046 Madrid (Spain); Hubin-Fraskin, M J [Department of Chemistry, University of Liege, 4000 Liege 1 (Belgium); Nixon, K; Brunger, M, E-mail: g.garcia@imaff.cfmac.csic.e [School of Chemistry, Physics and Earth Sciences, Flinders University, GPO Box 2100, Adelaide, SA 5001 (Australia)

    2009-11-15

    Current radiation based medical applications in the field of radiotherapy, radio-diagnostic and radiation protection require modelling single particle interactions at the molecular level. Due to their relevance in radiation damage to biological systems, special attention should be paid to include the effect of low energy secondary electrons. In this study we present a single track simulation procedure for photons and electrons which is based on reliable experimental and theoretical cross section data and the energy loss distribution functions derived from our experiments. The effect of including secondary electron interactions in this model will be discussed.

  4. Double aberration correction in a low-energy electron microscope

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Th., E-mail: schmidtt@fhi-berlin.mpg.de [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 6-8, D-14195 Berlin (Germany); Universitaet Wuerzburg, Experimentelle Physik II, Am Hubland, D-97074 Wuerzburg (Germany); Marchetto, H.; Levesque, P.L. [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 6-8, D-14195 Berlin (Germany); Groh, U.; Maier, F. [Universitaet Wuerzburg, Experimentelle Physik II, Am Hubland, D-97074 Wuerzburg (Germany); Preikszas, D. [Technische Universitaet Darmstadt, Angewandte Physik, Hochschulstrasse 6, D-64289 Darmstadt (Germany); Carl Zeiss NTS GmbH, Carl-Zeiss-Strasse 56, D-73447 Oberkochen (Germany); Hartel, P.; Spehr, R. [Technische Universitaet Darmstadt, Angewandte Physik, Hochschulstrasse 6, D-64289 Darmstadt (Germany); Lilienkamp, G. [Technische Universitaet Clausthal, Physikalisches Institut, Leibnizstrasse 4, D-38678 (Germany); Engel, W. [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 6-8, D-14195 Berlin (Germany); Fink, R. [Universitaet Erlangen-Nuernberg, Physikalische Chemie II, Egerlandstrasse 3, D-91058 Erlangen (Germany); Bauer, E. [Technische Universitaet Clausthal, Physikalisches Institut, Leibnizstrasse 4, D-38678 (Germany); Arizona State University, Department of Physics, Tempe, AZ 85287 (United States); Rose, H. [Technische Universitaet Darmstadt, Angewandte Physik, Hochschulstrasse 6, D-64289 Darmstadt (Germany); Umbach, E. [Universitaet Wuerzburg, Experimentelle Physik II, Am Hubland, D-97074 Wuerzburg (Germany); Freund, H.-J. [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 6-8, D-14195 Berlin (Germany)

    2010-10-15

    The lateral resolution of a surface sensitive low-energy electron microscope (LEEM) has been improved below 4 nm for the first time. This breakthrough has only been possible by simultaneously correcting the unavoidable spherical and chromatic aberrations of the lens system. We present an experimental criterion to quantify the aberration correction and to optimize the electron optical system. The obtained lateral resolution of 2.6 nm in LEEM enables the first surface sensitive, electron microscopic observation of the herringbone reconstruction on the Au(1 1 1) surface.

  5. Low-Energy Electron Beam Direct Writing Equipment

    Science.gov (United States)

    Fuse, Takashi; Ando, Atsushi; Kotsugi, Tadashi; Kinoshita, Hidetoshi; Sugihara, Kazuyoshi

    2007-09-01

    We proposed an electron beam direct writing (EBDW) system capable of high throughput and maskless operation based on a novel concept of using both low-energy electron beam (EB) and character projection (CP) system. We fabricated an EB optical column of low-energy EBDW equipment and obtained a resist pattern. We also investigated the beam blur and line width roughness (LWR) of lines and spaces (L/S) formed on a resist to change various EB current densities and convergence half angles. The obtained results show that a Coulomb interaction effect markedly affects the beam blur in our EB optical column. Thus, we reduce the number of sources caused by LWR and developed photoresists to obtain small LWR L/S patterns for achieving a high throughput.

  6. An ultracold low emittance electron source

    CERN Document Server

    Xia, G; Murray, A J; Bellan, L; Bertsche, W; Appleby, R B; Mete, O; Chattopadhyay, S

    2014-01-01

    Ultracold atom-based electron sources have recently been proposed as an alternative to the conventional photo-injectors or thermionic electron guns widely used in modern particle accelerators. The advantages of ultracold atom-based electron sources lie in the fact that the electrons extracted from the plasma (created from near threshold photo-ionization of ultracold atoms) have a very low temperature, i.e. down to tens of Kelvin. Extraction of these electrons has the potential for producing very low emittance electron bunches. These features are crucial for the next generation of particle accelerators, including free electron lasers, plasma-based accelerators and future linear colliders. The source also has many potential direct applications, including ultrafast electron diffraction (UED) and electron microscopy, due to its intrinsically high coherence. In this paper, the basic mechanism of ultracold electron beam production is discussed and our new research facility for an ultracold, low emittance electron s...

  7. Low energy electron beams for industrial and environmental applications

    CERN Document Server

    Skarda, Vlad

    2017-01-01

    EuCARD-2 Workshop, 8-9 December 2016, Warsaw, Poland. Organizers: Science and Technology Facilities Council, UK CERN - The European Organization for Nuclear Research, Switzerland, Institute of Nuclear Chemistry and Technology, Poland, Fraunhofer Institute for Electron Beam and Plasma Technology, Germany, Warsaw University of Technology, Poland. An article presents short information about EuCARD-2 Workshop “Low energy electron beams for industrial and environmental applications”, which was held in December 2016 in Warsaw. Objectives, main topics and expected output of meeting are described. List of organizers is included.

  8. Low-energy electron scattering from molecules, biomolecules and surfaces

    CERN Document Server

    Carsky, Petr

    2011-01-01

    Since the turn of the 21st century, the field of electron molecule collisions has undergone a renaissance. The importance of such collisions in applications from radiation chemistry to astrochemistry has flowered, and their role in industrial processes such as plasma technology and lighting are vital to the advancement of next generation devices. Furthermore, the development of the scanning tunneling microscope highlights the role of such collisions in the condensed phase, in surface processing, and in the development of nanotechnology.Low-Energy Electron Scattering from Molecules, Biomolecule

  9. Radiation processing of liquid with low energy electron accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Makuuchi, Keizo [Japan Atomic Energy Research Inst., Takasaki, Gunma (Japan). Takasaki Radiation Chemistry Research Establishment

    2003-02-01

    Radiation induced emulsion polymerization, radiation vulcanization of NR latex (RVNRL) and radiation degradation of natural polymers were selected and reviewed as the radiation processing of liquid. The characteristic of high dose rate emulsion polymerization is the occurrence of cationic polymerization. Thus, it can be used for the production of new materials that cannot be obtained by radical polymerization. A potential application will be production of polymer emulsion that can be used as water-borne UV/EB curing resins. The technology of RVNRL by {gamma}-ray has been commercialized. RVNRL with low energy electron accelerator is under development for further vulcanization cost reduction. Vessel type irradiator will be favorable for industrial application. Radiation degradation of polysaccharides is an emerging and promising area of radiation processing. However, strict cost comparison between liquid irradiation with low energy EB and state irradiation with {gamma}-ray should be carried out. (author)

  10. Low-Energy Electron Scattering by Sugarcane Lignocellulosic Biomass Molecules

    Science.gov (United States)

    Oliveira, Eliane; Sanchez, Sergio; Bettega, Marcio; Lima, Marco; Varella, Marcio

    2012-06-01

    The use of second generation (SG) bioethanol instead of fossil fuels could be a good strategy to reduce greenhouse gas emissions. However, the efficient production of SG bioethanol has being a challenge to researchers around the world. The main barrier one must overcome is the pretreatment, a very important step in SG bioethanol aimed at breaking down the biomass and facilitates the extraction of sugars from the biomass. Plasma-based treatment, which can generate reactive species, could be an interesting possibility since involves low-cost atmospheric-pressure plasma. In order to offer theoretical support to this technique, the interaction of low-energy electrons from the plasma with biomass is investigated. This study was motived by several works developed by Sanche et al., in which they understood that DNA damage arises from dissociative electron attachment, a mechanism in which electrons are resonantly trapped by DNA subunits. We will present elastic cross sections for low-energy electron scattering by sugarcane biomass molecules, obtained with the Schwinger multichannel method. Our calculations indicate the formation of π* shape resonances in the lignin subunits, while a series of broad and overlapping σ* resonances are found in cellulose and hemicellulose subunits. The presence of π* and σ* resonances could give rise to direct and indirect dissociation pathways in biomass. Then, theoretical resonance energies can be useful to guide the plasma-based pretreatment to break down specific linkages of interest in biomass.

  11. Low energy electron point source microscopy: beyond imaging.

    Science.gov (United States)

    Beyer, André; Gölzhäuser, Armin

    2010-09-01

    Low energy electron point source (LEEPS) microscopy has the capability to record in-line holograms at very high magnifications with a fairly simple set-up. After the holograms are numerically reconstructed, structural features with the size of about 2 nm can be resolved. The achievement of an even higher resolution has been predicted. However, a number of obstacles are known to impede the realization of this goal, for example the presence of electric fields around the imaged object, electrostatic charging or radiation induced processes. This topical review gives an overview of the achievements as well as the difficulties in the efforts to shift the resolution limit of LEEPS microscopy towards the atomic level. A special emphasis is laid on the high sensitivity of low energy electrons to electrical fields, which limits the structural determination of the imaged objects. On the other hand, the investigation of the electrical field around objects of known structure is very useful for other tasks and LEEPS microscopy can be extended beyond the task of imaging. The determination of the electrical resistance of individual nanowires can be achieved by a proper analysis of the corresponding LEEPS micrographs. This conductivity imaging may be a very useful application for LEEPS microscopes.

  12. Detectors for low energy electron cooling in RHIC

    Energy Technology Data Exchange (ETDEWEB)

    Carlier, F. S. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2016-02-15

    Low energy operation of RHIC is of particular interest to study the location of a possible critical point in the QCD phase diagram. The performance of RHIC at energies equal to or lower than 10 GV/nucleon is limited by nonlinearities, Intra-BeamScattering (IBS) processes and space-charge effects. To successfully address the luminosity and ion store lifetime limitations imposed by IBS the method of electron cooling has been envisaged. During electron cooling processes electrons are injected along with the ion beam at the nominal ion bunch velocities. The velocity spread of the ion beam is reduced in all planes through Coulomb interactions between the cold electron beam and the ion beam. The electron cooling system proposed for RHIC will be the first of its kind to use bunched beams for the delivery of the electron bunches, and will therefore be accompanied by the necessary challenges. The designed electron cooler will be located in IP2. The electron bunches will be accelerated by a linac before being injected along side the ion beams. Thirty consecutive electron bunches will be injected to overlap with a single ion bunch. They will first cool the yellow beam before being extracted turned by 180-degrees and reinjected into the blue beam for cooling. As such, both the yellow and blue beams will be cooled by the same ion bunches. This will pose considerable challenges to ensure proper electron beam quality to cool the second ion beam. Furthermore, no ondulator will be used in the electron cooler so radiative recombination between the ions and the electrons will occur.

  13. Emittance growth from electron beam modulation

    Energy Technology Data Exchange (ETDEWEB)

    Blaskiewicz, M.

    2009-12-01

    In linac ring colliders like MeRHIC and eRHIC a modulation of the electron bunch can lead to a modulation of the beam beam tune shift and steering errors. These modulations can lead to emittance growth. This note presents simple formulas to estimate these effects which generalize some previous results.

  14. Low energy electron interactions with complex biological targets

    Science.gov (United States)

    Orlando, Thomas

    2012-10-01

    The low energy (1-25 eV) electron-induced damage of DNA oligomers have been examined both theoretically and experimentally. Specifically, elastic scattering of 5-30 eV electrons within B-DNA 5'-CCGGCGCCGG-3' and A-DNA 5'-CGCGAATTCGCG-3' sequences has been calculated using the separable representation of a free-space electron propagator and a curved wave multiple scattering formalism. The disorder brought about by the surrounding water and helical base stacking leads to featureless amplitude build-up of elastically scattered electrons on the sugars and phosphate groups for all energies between 5-30 eV. However, some constructive interference features arising from diffraction were revealed when examining the structural waters within the major groove. We correlated these scattering features with measured DNA single and double strand breaks. Compound resonance states involving interfacial water and excitation energies > 5 eV seem to be required for lethal double strand breaks. We have recently extended this work to excitation energies below 5 eV by examining the damage using Raman-microscopy and scanning electrostatic force microscopy. Very efficient damage via single strand breaks is observed below 5 eV excitation energies. This involves π* negative ion resonances that are initially localized on the bases but transferred to the σ* states of the sugar-phosphate bond. The efficacies of these channels depend upon the base-pair sequences as well as the presence of water.

  15. Wettability Modification of Nanomaterials by Low-Energy Electron Flux

    Directory of Open Access Journals (Sweden)

    Torchinsky I

    2009-01-01

    Full Text Available Abstract Controllable modification of surface free energy and related properties (wettability, hygroscopicity, agglomeration, etc. of powders allows both understanding of fine physical mechanism acting on nanoparticle surfaces and improvement of their key characteristics in a number of nanotechnology applications. In this work, we report on the method we developed for electron-induced surface energy and modification of basic, related properties of powders of quite different physical origins such as diamond and ZnO. The applied technique has afforded gradual tuning of the surface free energy, resulting in a wide range of wettability modulation. In ZnO nanomaterial, the wettability has been strongly modified, while for the diamond particles identical electron treatment leads to a weak variation of the same property. Detailed investigation into electron-modified wettability properties has been performed by the use of capillary rise method using a few probing liquids. Basic thermodynamic approaches have been applied to calculations of components of solid–liquid interaction energy. We show that defect-free, low-energy electron treatment technique strongly varies elementary interface interactions and may be used for the development of new technology in the field of nanomaterials.

  16. Very Low Energy Electron Scattering from Ozone and Chlorine Dioxide

    Science.gov (United States)

    Gulley, R. J.; Field, T. A.; Steer, W. A.; Mason, N. J.; Ziesel, J. P.; Lunt, S. L.; Field, D.

    1998-10-01

    Total cross-sections are reported for the scattering of electrons from ozone (O_3) and chlorine dioxide (OClO) for energies in the range of 9 meV to 10 eV. The measurements were made in transmission experiments using a synchrotron photoionization apparatus with an energy resolution in the incident electron beam of ~ 3.5 meV (FWHM). The cross section for O3 shows strong rotational scattering at low energy, through the presence of the permanent dipole moment of O_3. Superposed on this strong scattering signal, there is evidence of a weak structure around 50 meV associated with dissociative attachment. A shape resonance, known from earlier work at ~ 4 meV, is also observed. Electron scattering from OClO is dominated by rotationally inelastic scattering decreasing from a peak at essentially zero eV to an energy of 40 meV, where p-wave attachment becomes more important, peaking at 50--60 meV and extending to several hundred meV.

  17. A new method of emittance measurement for electron beams from the Micro-emitter

    Energy Technology Data Exchange (ETDEWEB)

    Ishizuka, Hiroshi [Fukuoka Inst. of Technology (Japan); Nakahara, Yuriko; Kawasaki, Sunao; Musyoki, Stephen; Shimizu, Hiroshi; Watanabe, Akihiko; Shiho, Makoto

    1994-03-01

    Recently a new type of cathode called Micro-emitter is in progress. This cathode is micro fabricated field emitter having the characteristics of very low emittance and high brightness. We can not measure the emittance of the cathode with conventional method like pepper-pot method. The reasons are ; 1. The angle between the electron orbit and the axis is very small. ; and 2. We can not focus the electron beam in the vacuum or on the surface of the material since the current density of the cathode is extremely high. For the emittance measurement for such low emittance and high brightness cathode, we need to expand the beam, and measure the beam cross section without any slits or apertures. We study and propose a new emittance measurement method for the Micro-emitter. (author).

  18. Large-area lanthanum hexaboride electron emitter

    Science.gov (United States)

    Goebel, D. M.; Hirooka, Y.; Sketchley, T. A.

    1985-09-01

    The characteristics of lanthanum-boron thermionic electron emitters are discussed, and a large-area, continuously operating cathode assembly and heater are described. Impurity production and structural problems involving the support of the LaB6 have been eliminated in the presented configuration. The performance of the cathode in a plasma discharge, where surface modification occurs by ion sputtering, is presented. Problem areas which affect lifetime and emission current capability are discussed.

  19. High-Resolution Measurements of Low-Energy Conversion Electrons

    CERN Multimedia

    Gizon, A; Putaux, J

    2002-01-01

    Measurements of low-energy internal conversion electrons have been performed with high energy resolution in some N = 105 odd and odd-odd nuclei using a semi-circular spectrograph associated to a specific tape transport system. These experiments aimed to answer the following questions~: \\begin{itemize} \\item Do M3 isomeric transitions exist in $^{183}$Pt and $^{181}$Os, isotones of $^{184}$Au~? \\item Are the neutron configurations proposed to describe the isomeric and ground states of $^{184}$Au right or wrong~? \\item Does it exist an isomeric state in $^{182}$Ir, isotone of $^{181}$Os, $^{183}$Pt and $^{184}$Au~? \\item What are the spin and parity values of the excited states of $^{182}$Ir~? \\end{itemize} In $^{183}$Pt, the 35.0 keV M3 isomeric transition has been clearly observed and the reduced transition probability has been determined. The deduced hindrance factor is close to that observed in the neighbouring odd-odd $^{184}$Au nucleus. This confirms the neutron configurations previously proposed for the ...

  20. Predicted emittance and brightness of the pseudospark electron-beam

    Energy Technology Data Exchange (ETDEWEB)

    Pitchford, L.C. [Univ. Paul Sabatier, Toulouse (France). Centre de Physique Atomique

    1995-06-01

    The emittance /and brightness of the electron beam generated during the hollow cathode phase of pseudospark operation are calculated using the two-dimensional hybrid fluid-particle model previously developed to study the time and space development of the plasma in a pseudospark discharge. Two distinct energy components exist in the electron beam; a high-energy component with an energy equivalent to the full discharge voltage and another, broad, low-energy component. In the 100 ns following breakdown and for the conditions of the calculations, the emittance of the high energy component decreases by an order of magnitude and the brightness of the high energy component reaches almost 10{sup 10} A/m{sup 2} rad{sub 2}. This work demonstrates the feasibility of using the model to guide the optimization of the pseudospark electron beam properties and shows that the optimum beam properties are achieved after the plasma has filled the hollow cathode and begun to expand radially in the main gap.

  1. Low Energy Electrons as Probing Tool for Astrochemical Reaction Mechanisms

    Science.gov (United States)

    Hendrik Bredehöft, Jan; Swiderek, Petra; Hamann, Thorben

    hitting anything solid, they will create secondary electrons. These electrons are in fact the energy source needed to run interstellar chemistry. Slow electrons can in principle trigger three different primary processes in a molecule. The first is ionisation by electron impact (EI), which is used to create ions in mass spectrometry. In this process an electron hits a molecule M and knocks an outer shell electron to create a cation. This occurs whenever the electron energy is above the ionisation threshold of the target molecule. Another possibility is the attachment of a slow electron to a molecule to create an anion. This can occur at sharply defined resonance energies specific to the molecule M. A third possibility is to excite the molecule M to a neutral state M∗ .[9] M + e- -> M+ + 2 e- (Electron impact ionisation) M + e- -> M- (Electron attachment) M + e- -> M∗ + e- (Neutral excitation) The created states M+ , M- and M∗ are usually not stable states so they very often dissociate into ions and radicals, which can then further react with neighbouring molecules to form new chemical species. In these chemical reactions some products can be formed even at very low temperatures that would otherwise require a lot of thermal energy and/or special catalysts. The formation of ethylamine from ethylene and ammonia by hydroamination is one such example. The reaction is characterized by a high activation barrier caused by the electronic repulsion between the electron density rich C=C double bound and the lone pair electrons of ammo-nia. The reaction also has a highly negative entropy, so it becomes less favourable at higher temperatures, ruling out heat as a means to facilitate the reaction. In classical chemistry this problem is overcome by the use of catalysts. Unfortunately there still is no general catalyst for this kind of reaction. Recently it was shown that the reaction can efficiently be induced by low energy electron radiation.[10] One of the reaction partners is

  2. The role of low-energy (≤ 20 eV) electrons in astrochemistry

    Science.gov (United States)

    Boyer, Michael C.; Rivas, Nathalie; Tran, Audrey A.; Verish, Clarissa A.; Arumainayagam, Christopher R.

    2016-10-01

    UV photon-driven condensed phase cosmic ice reactions have been the main focus in understanding the extraterrestrial synthesis of complex organic molecules. Low-energy (≤ 20 eV) electron-induced reactions, on the other hand, have been largely ignored. In this article, we review studies employing surface science techniques to study low-energy electron-induced condensed phase reactions relevant to astrochemistry. In particular, we show that low-energy electron irradiation of methanol ices leads to the synthesis of many of the same complex molecules formed through UV irradiation. Moreover, our results are qualitatively consistent with the hypothesis that high-energy condensed phase radiolysis is mediated by low-energy electron-induced reactions. In addition, due to the numbers of available low-energy secondary electrons resulting from the interaction of high-energy radiation with matter as well as differences between electron- and photon-induced processes, low-energy electron-induced reactions are perhaps as, or even more, effective than photon-induced reactions in initiating condensed-phase chemical reactions in the interstellar medium. Consequently, we illustrate a need for astrochemical models to include the details of electron-induced reactions in addition to those driven by UV photons. Finally, we show that low-energy electron-induced reactions may lead to the production of unique molecular species that could serve as tracer molecules for electron-induced condensed phase reactions in the interstellar medium.

  3. Design and performance simulations of the bunch compressor for the Advanced Photon Source Low-Energy Undulator Test Line free-electron laser

    Directory of Open Access Journals (Sweden)

    M. Borland

    2001-07-01

    Full Text Available A magnetic bunch compressor was designed and commissioned to provide higher peak current for the Advanced Photon Source's Low-Energy Undulator Test Line free-electron laser [S. V. Milton et al., Phys. Rev. Lett. 85, 988 (2000]. Of great concern is limiting emittance growth due to coherent synchrotron radiation. Tolerances must also be carefully evaluated to find stable operating conditions and ensure that the system can meet operational goals. Automated matching and tolerance simulations allowed consideration of numerous configurations, pinpointing those with reduced error sensitivity. Simulations indicate significant emittance growth up to 600 A peak current, for which the normalized emittance will increase from 5 to about 8.5 μm. The simulations also provide predictions of emittance variation with chicane parameters and precompressor linac phase, which we hope to verify experimentally.

  4. Evaluations of carbon nanotube field emitters for electron microscopy

    Science.gov (United States)

    Nakahara, Hitoshi; Kusano, Yoshikazu; Kono, Takumi; Saito, Yahachi

    2009-11-01

    Brightness of carbon nanotube (CNT) emitters was already reported elsewhere. However, brightness of electron emitter is affected by a virtual source size of the emitter, which strongly depends on electron optical configuration around the emitter. In this work, I- V characteristics and brightness of a CNT emitter are measured under a practical field emission electron gun (e-gun) configuration to investigate availability of CNT for electron microscopy. As a result, it is obtained that an emission area of MWNT is smaller than its tip surface area, and the emission area corresponds to a five-membered-ring with 2nd nearest six-membered-rings on the MWNT cap surface. Reduced brightness of MWNT is measured as at least 2.6×109 A/m 2 sr V. It is concluded that even a thick MWNT has enough brightness under a practical e-gun electrode configuration and suitable for electron microscopy.

  5. Evaluations of carbon nanotube field emitters for electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Nakahara, Hitoshi, E-mail: nakahara@nagoya-u.jp [Department of Quantum Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Kusano, Yoshikazu; Kono, Takumi; Saito, Yahachi [Department of Quantum Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan)

    2009-11-30

    Brightness of carbon nanotube (CNT) emitters was already reported elsewhere. However, brightness of electron emitter is affected by a virtual source size of the emitter, which strongly depends on electron optical configuration around the emitter. In this work, I-V characteristics and brightness of a CNT emitter are measured under a practical field emission electron gun (e-gun) configuration to investigate availability of CNT for electron microscopy. As a result, it is obtained that an emission area of MWNT is smaller than its tip surface area, and the emission area corresponds to a five-membered-ring with 2nd nearest six-membered-rings on the MWNT cap surface. Reduced brightness of MWNT is measured as at least 2.6x10{sup 9} A/m{sup 2} sr V. It is concluded that even a thick MWNT has enough brightness under a practical e-gun electrode configuration and suitable for electron microscopy.

  6. Emittance measurements of the CLIO electron beam

    Science.gov (United States)

    Chaput, R.; Devanz, G.; Joly, P.; Kergosien, B.; Lesrel, J.

    1997-02-01

    We have designed a setup to measure the transverse emittance at the CLIO accelerator exit, based on the "3 gradients" method. The beam transverse size is measured simply by scanning it with a steering coil across a fixed jaw and recording the transmitted current, at various quadrupole strengths. A code then performs a complete calculation of the emittance using the transfer matrix of the quadrupole instead of the usual classical lens approximation. We have studied the influence of various parameters on the emittance: Magnetic field on the e-gun and the peak current. We have also improved a little the emittance by replacing a mismatched pipe between the buncher and accelerating section to avoid wake-field effects; The resulting improvements of the emittance have led to an increase in the FEL emitted power.

  7. Low Energy X-Ray and Electron Interactions within Matter.

    Science.gov (United States)

    1980-03-01

    Microscopy at Pomona College," Norelco Reporter, VII, 137 (1960). b."Isolation of Selected Elements with an Electron Microscope ," Norelco Reporter...38. "Measurement of Primary Electron Interaction Coefficients (500 to 1500 eV Region," Colloque International du C.N.R.S., Processus Electroniques

  8. Treatment of surfaces with low-energy electrons

    Science.gov (United States)

    Frank, L.; Mikmeková, E.; Lejeune, M.

    2017-06-01

    Electron-beam-induced deposition of various materials from suitable precursors has represented an established branch of nanotechnology for more than a decade. A specific alternative is carbon deposition on the basis of hydrocarbons as precursors that has been applied to grow various nanostructures including masks for subsequent technological steps. Our area of study was unintentional electron-beam-induced carbon deposition from spontaneously adsorbed hydrocarbon molecules. This process traditionally constitutes a challenge for scanning electron microscopy practice preventing one from performing any true surface studies outside an ultrahigh vacuum and without in-situ cleaning of samples, and also jeopardising other electron-optical devices such as electron beam lithographs. Here we show that when reducing the energy of irradiating electrons sufficiently, the e-beam-induced deposition can be converted to e-beam-induced release causing desorption of hydrocarbons and ultimate cleaning of surfaces in both an ultrahigh and a standard high vacuum. Using series of experiments with graphene samples, we demonstrate fundamental features of e-beam-induced desorption and present results of checks for possible radiation damage using Raman spectroscopy that led to optimisation of the electron energy for damage-free cleaning. The method of preventing carbon contamination described here paves the way for greatly enhanced surface sensitivity of imaging and substantially reduced demands on vacuum systems for nanotechnological applications.

  9. Can low energy electrons affect high energy physics accelerators?

    CERN Document Server

    Cimino, R; Furman, M A; Pivi, M; Ruggiero, F; Rumolo, Giovanni; Zimmermann, Frank

    2004-01-01

    The properties of the electrons participating in the build up of an electron cloud (EC) inside the beam-pipe have become an increasingly important issue for present and future accelerators whose performance may be limited by this effect. The EC formation and evolution are determined by the wall-surface properties of the accelerator vacuum chamber. Thus, the accurate modeling of these surface properties is an indispensible input to simulation codes aimed at the correct prediction of build-up thresholds, electron-induced instability or EC heat load. In this letter, we present the results of surface measurements performed on a prototype of the beam screen adopted for the Large Hadron Collider (LHC), which presently is under construction at CERN. We have measured the total secondary electron yield (SEY) as well as the related energy distribution curves (EDC) of the secondary electrons as a function of incident electron energy. Attention has been paid, for the first time in this context, to the probability at whic...

  10. A New Method of Measuring Electron Emission Induced by Low Energy Ions from Solids

    Institute of Scientific and Technical Information of China (English)

    ZHANG Heng-Da; A. Breskin; R. Chechik; S. Shckemelinin; E. Cheifetz

    2005-01-01

    @@ A new mathematical method of measuring electron emission induced by low energy ions from solids is described and used to calculate secondary electron emission according to the recorded pulse-height spectra of ions and ultraviolet (UV) photons. Using the UV single secondary electron spectra, we predict the shape of many secondary electron distributions under consideration of detection efficiency of MCP detector. These calculated distributions allow us to characterize the secondary electrons yield, and to give a secondary electron distribution for measured data. It seems rather feasible to determine secondary electron yield emitted by low energy ions at very low ion fluxes.

  11. Bunch transverse emittance increase in electron storage rings

    Institute of Scientific and Technical Information of China (English)

    GAO Jie

    2009-01-01

    In this paper a theoretical framework to estimate the bunch transverse emittance growing in electron storage rings due to short range transverse wakefield of the machine is established. New equilibrium emittance equations are derived and applied to explain the experimentally obtained results in ATF damping ring. This equation will be useful for linear collider damping ring design.

  12. Electronic Warfare:Issues and Challenges for Emitter Classification

    Directory of Open Access Journals (Sweden)

    Manish Gupta

    2011-04-01

    Full Text Available Electronic warfare (EW is an important capability that provides advantage to defence forces over their adversaries. Defence forces gather tactical intelligence through EW sensors, which provide the means to counter hostile actions of enemy forces. Functions of an EW system is threat detection and the area surveillance so as to determine the identity of surrounding emitters. Emitter classification system identifies possible threats by analysing intercepted signals. Problem of identifying emitters based on its intercepted signal characteristics is a challenging problem in electronic warfare studies. Major issues and challenges for emitter classification such as drifting of emitter parameters due to aging, operational characteristic of an emitter, i.e., same emitter can operate on multiple bands and multiple pulse repetition frequencies (PRFs are highlighted. A novel approach based on some well-known statistical methods, e.g., regression analysis, hypothesis testing, and discriminent analysis is proposed. The effectiveness of the proposed approach has been tested over ELINT (Electronic Intelligence data and illustrated using simulation data. The proposed approach can play a solution for wide variety of problems in emitter classification in electronic warfare studies.Defence Science Journal, 2011, 61(3, pp.228-234, DOI:http://dx.doi.org/10.14429/dsj.61.529

  13. Low-energy electron transmission through high aspect ratio Al O nanocapillaries

    DEFF Research Database (Denmark)

    Milosavljević, A.R.; Jureta, J.; Víkor, G.;

    2009-01-01

    Electron transmission through insulating AlO nanocapillaries of different diameters (40 and 270 nm) and 15 μm length has been investigated for low-energy electrons (2-120 V). The total intensity of transmitted current weakly depends on the incident electron energy and tilt angle defined with resp......Electron transmission through insulating AlO nanocapillaries of different diameters (40 and 270 nm) and 15 μm length has been investigated for low-energy electrons (2-120 V). The total intensity of transmitted current weakly depends on the incident electron energy and tilt angle defined...

  14. Innovative energy efficient low-voltage electron beam emitters

    Science.gov (United States)

    Felis, Kenneth P.; Avnery, Tovi; Berejka, Anthony J.

    2002-03-01

    Advanced electron beams (AEB) has developed a modular, low voltage (80-125 keV), high beam current (up to 40 ma), electron emitter with typically 25 cm of beam width, that is housed in an evacuated, returnable chamber that is easy to plug in and connect. The latest in nanofabrication enables AEB to use an ultra-thin beam window. The power supply for AEB's emitter is based on solid-state electronics. This combination of features results in a remarkable electrical efficiency. AEB's electron emitter relies on a touch screen, computer control system. With 80 μm of unit density beam penetration, AEB's electron emitter has gained market acceptance in the curing of opaque, pigmented inks and coatings used on flexible substrates, metals and fiber composites and in the curing of adhesives in foil based laminates.

  15. Precision shape modification of nanodevices with a low-energy electron beam

    Science.gov (United States)

    Zettl, Alex; Yuzvinsky, Thomas David; Fennimore, Adam

    2010-03-09

    Methods of shape modifying a nanodevice by contacting it with a low-energy focused electron beam are disclosed here. In one embodiment, a nanodevice may be permanently reformed to a different geometry through an application of a deforming force and a low-energy focused electron beam. With the addition of an assist gas, material may be removed from the nanodevice through application of the low-energy focused electron beam. The independent methods of shape modification and material removal may be used either individually or simultaneously. Precision cuts with accuracies as high as 10 nm may be achieved through the use of precision low-energy Scanning Electron Microscope scan beams. These methods may be used in an automated system to produce nanodevices of very precise dimensions. These methods may be used to produce nanodevices of carbon-based, silicon-based, or other compositions by varying the assist gas.

  16. Electron Emission from Ultra-Large Area MOS Electron Emitters

    DEFF Research Database (Denmark)

    Thomsen, Lasse Bjørchmar; Nielsen, Gunver; Vendelbo, Søren Bastholm;

    2009-01-01

    Ultralarge metal-oxide-semiconductor (MOS) devices with an active oxide area of 1 cm2 have been fabricated for use as electron emitters. The MOS structures consist of a Si substrate, a SiO2 tunnel barrier (~5 nm), a Ti wetting layer (3–10 Å), and a Au top layer (5–60 nm). Electron emission from...... layer is varied from 3 to 10 Å which changes the emission efficiency by more than one order of magnitude. The apparent mean free path of ~5 eV electrons in Au is found to be 52 Å. Deposition of Cs on the Au film increased the electron emission efficiency to 4.3% at 4 V by lowering the work function....... Electron emission under high pressures (up to 2 bars) of Ar was observed. ©2009 American Vacuum Society...

  17. Coherent diffraction and holographic imaging of individual biomolecules using low-energy electrons

    CERN Document Server

    Latychevskaia, Tatiana; Escher, Conrad; Fink, Hans-Werner

    2013-01-01

    Modern microscopy techniques are aimed at imaging an individual molecule at atomic resolution. Here we show that low-energy electrons with kinetic energies of 50-250 eV offer a possibility of overcome the problem of radiation damage, and obtaining images of individual biomolecules. Two experimental schemes for obtaining images of individual molecules, holography and coherent diffraction imaging, are discussed and compared. Images of individual molecules obtained by both techniques, using low-energy electrons, are shown.

  18. Energy-Filtered Tunnel Transistor: A New Device Concept Toward Extremely-Low Energy Consumption Electronics

    Science.gov (United States)

    2015-12-17

    New Device Concept Toward Extremely-Low Energy Consumption Electronics 5a. CONTRACT NUMBER 5b. GRANT NUMBER N00014-12-1-0492 5c. PROGRAM... energy consumption transistors. We have experimentally demonstrated, for the first time, that a quantum well energy level can filter out energetic...Concept Toward Extremely-Low Energy Consumption Electronics (Grant No: N00014-12-1-0492) PI: Seong Jin Koh Department of Materials Science and

  19. LDRD project 151362 : low energy electron-photon transport.

    Energy Technology Data Exchange (ETDEWEB)

    Kensek, Ronald Patrick; Hjalmarson, Harold Paul; Magyar, Rudolph J.; Bondi, Robert James; Crawford, Martin James

    2013-09-01

    At sufficiently high energies, the wavelengths of electrons and photons are short enough to only interact with one atom at time, leading to the popular %E2%80%9Cindependent-atom approximation%E2%80%9D. We attempted to incorporate atomic structure in the generation of cross sections (which embody the modeled physics) to improve transport at lower energies. We document our successes and failures. This was a three-year LDRD project. The core team consisted of a radiation-transport expert, a solid-state physicist, and two DFT experts.

  20. Precision control of intense electron beams in a low-energy ring

    Science.gov (United States)

    Wu, Chao

    Many applications of particle accelerators require beams with high intensity and low emittance in a stable fashion. An important research area involves the study of space-charge forces in beams, which are significant at low energy. Research reported in this dissertation was done on the University of Maryland Electron Ring (UMER), a particle accelerator designed for research on space-charge-dominated beams. High-precision control of space-charge-dominated beams is very challenging. However, standard beam control approaches do not work well on UMER. This is due to UMER's unique structure, in which there are fewer beam position monitors than beam position correctors and a complex coupling between the horizontal and vertical kicker magnets. In this work, a novel beam control algorithm was developed based on the closed-orbit response matrix, and this algorithm was applied to UMER. The algorithm markedly improves UMER's multi-turn operation while reducing closed orbit distortion. Using the orbit response matrix, a diagnosis method was developed that expeditiously detected malfunctions in components such as beam position monitors and magnets. Space-charge forces can greatly affect the resonant properties of rings. With the electrostatic particle-in-cell code WARP, ring resonances were analyzed under a variety of conditions. This resulted in an improved understanding of and capability to predict beam losses and improve machine performance. Simulation results using WARP were obtained for several magnet models and compared with results from other simulation codes. Experimental results on resonance analysis were also given using wall current monitor signals.

  1. Advanced transmission electron microscopy studies in low-energy ion implanted Si Semiconductors; Junctions; Silicon

    CERN Document Server

    Wang, T S

    2002-01-01

    As the dimensions of semiconductor devices shrink down to 0.1 mu m and beyond, low energy ion implantation is required to introduce shallower junctions to match such small devices. In this work, transmission electron microscopy (TEM) is employed to analyse low energy implanted junctions with both structural and chemical analyses. High resolution transmission electron microscopy (HRTEM) has been employed to observe Si crystal damage and amorphization due to low energy B sup + /As sup + ion implantations, and also, defect formation/annihilation during rapid thermal annealing (RTA). The damage effects due to different implant temperatures between 300 deg C and -150 deg C are also discussed. Since knowledge of the distribution of low energy ion implanted dopants in Si is extremely important for semiconductor device processing, energy filtered transmission electron microscopy (EFTEM) has been employed to determine implanted B distributions in Si while Z-contrast imaging and X-ray analytical mapping techniques are ...

  2. Low-energy electron microscopy on two-dimensional systems : : growth, potentiometry and band structure mapping

    NARCIS (Netherlands)

    Kautz, Jaap

    2015-01-01

    Low Energy Electron Microscopy (LEEM) is a microscopy technique typically used to study surface processes. The sample is illuminated with a parallel beam of electrons under normal incidence and the reflected electrons are projected onto a pixelated detector, where an image is formed. In the first

  3. Electron Polarimetry at Low Energies in Hall C at Jefferson Lab

    Energy Technology Data Exchange (ETDEWEB)

    Gaskell, David J. [JLAB

    2013-11-01

    Although the majority of Jefferson Lab experiments require multi-GeV electron beams, there have been a few opportunities to make electron beam polarization measurements at rather low energies. This proceedings will discuss some of the practical difficulties encountered in performing electron polarimetry via Mo/ller scattering at energies on the order of a few hundred MeV. Prospects for Compton polarimetry at very low energies will also be discussed. While Mo/ller scattering is likely the preferred method for electron polarimetry at energies below 500 MeV, there are certain aspects of the polarimeter and experiment design that must be carefully considered.

  4. Coherent femtosecond low-energy single-electron pulses for time-resolved diffraction and imaging: A numerical study

    Energy Technology Data Exchange (ETDEWEB)

    Paarmann, A.; Mueller, M.; Ernstorfer, R. [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin (Germany); Gulde, M.; Schaefer, S.; Schweda, S.; Maiti, M.; Ropers, C. [Courant Research Center Physics and Material Physics Institute, University of Goettingen, Friedrich-Hund-Platz 1, 37077 Goettingen (Germany); Xu, C. [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin (Germany); Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Science, 390, Qinghe Road, Jiading, Shanghai 201800 (China); Hohage, T. [Institute of Numerical and Applied Mathematics, University of Goettingen, Lotzestr. 16-18, 37083 Goettingen (Germany); Schenk, F. [Courant Research Center Physics and Material Physics Institute, University of Goettingen, Friedrich-Hund-Platz 1, 37077 Goettingen (Germany); Institute of Numerical and Applied Mathematics, University of Goettingen, Lotzestr. 16-18, 37083 Goettingen (Germany)

    2012-12-01

    We numerically investigate the properties of coherent femtosecond single electron wave packets photoemitted from nanotips in view of their application in ultrafast electron diffraction and non-destructive imaging with low-energy electrons. For two different geometries, we analyze the temporal and spatial broadening during propagation from the needle emitter to an anode, identifying the experimental parameters and challenges for realizing femtosecond time resolution. The simple tip-anode geometry is most versatile and allows for electron pulses of several ten of femtosecond duration using a very compact experimental design, however, providing very limited control over the electron beam collimation. A more sophisticated geometry comprising a suppressor-extractor electrostatic unit and a lens, similar to typical field emission electron microscope optics, is also investigated, allowing full control over the beam parameters. Using such a design, we find {approx}230 fs pulses feasible in a focused electron beam. The main limitation to achieve sub-hundred femtosecond time resolution is the typical size of such a device, and we suggest the implementation of more compact electron optics for optimal performance.

  5. Excitation of the lowest electronic transitions in ethanol by low-energy electrons

    Science.gov (United States)

    Hargreaves, L. R.; Khakoo, M. A.; Winstead, C.; McKoy, V.

    2016-09-01

    We report absolute differential and integral cross sections for electronic excitation of ethanol, by low-energy electron impact. Cross sections for low-lying excited states were measured at incident electron energies from 9 to 20 eV and at scattering angles from {5}\\circ through {130}\\circ . Our results include cross sections for excitation of the 1{}3A\\prime \\prime and 1{}1A\\prime \\prime states as well as for the 2{}3A\\prime \\prime + 1{}3A\\prime and 2{}1A\\prime \\prime + 2{}1A\\prime cross section sums. Corresponding calculations were also performed using the Schwinger multichannel method, within an 11-channel close-coupling scheme.

  6. Low-emittance tuning at the Cornell Electron Storage Ring

    CERN Document Server

    Shanks, James; Sagan, David

    2013-01-01

    In 2008 the Cornell Electron/Positron Storage Ring (CESR) was reconfigured from an electron/positron collider to serve as a testbed for the International Linear Collider (ILC) damping rings. One of the primary goals of the CESR Test Accelerator (CesrTA) project is to develop low emittance tuning techniques to achieve sub-10pm geometric vertical emittance at 2.085 GeV. This paper discusses the tuning methods used at CesrTA to achieve low-emittance conditions. A minimum vertical emittance of 8.7 +2.9/-3.4(sys) +/-0.2(stat) pm has been achieved at 2.085 GeV. In various configurations and beam energies the correction technique routinely achieves vertical emittance <15 pm after correction. Beam-based measurement and correction requires about 15 minutes. Simulations modeling the effects of magnet misalignments, BPM errors, and emittance correction algorithm suggest the residual vertical emittance measured at the conclusion of the tuning procedure is dominated by sources other than optics errors and misalignments...

  7. Emittance measurements for the Illinois/CEBAF polarized electron source

    Energy Technology Data Exchange (ETDEWEB)

    Dunham, B.M.; Cardman, L.S. [Illinois Univ., Urbana, IL (United States); Sinclair, C.K. [Continuous Electron Beam Accelerator Facility, Newport News, VA (United States)

    1995-01-01

    The transverse thermal properties of the electrons photoemitted from GaAs determine the intrinsic beam emittance, an important quantity in applications such as polarized electron sources and high-brightness sources. In this paper, emittance measurements using the Illinois/CEBAF polarized electron source are described. The emittance was measured as a function of both the laser beam spot size and laser wavelength at low currents. The data was used to infer the transverse thermal energy of the electrons photoemitted from GaAs for wavelengths between 514 and 840 nm. Near the bandgap the transverse energy is {approximately}34 meV, a factor of 3 lower than that of the beam from a typical thermionic electron gun. 8 refs., 2 figs.

  8. Measurement of Low Energy Electronic Recoil Response and Electronic/Nuclear Recoils Discrimination in XENON100

    Science.gov (United States)

    Ye, Jingqiang; Xenon Collaboration

    2017-01-01

    The XENON100 detector uses liquid xenon time projection chamber to search for nuclear recoils(NR) caused by hypothetical Weakly Interacting Massive Particles (WIMPs). The backgrounds are mostly electronic recoils(ER), thus it's crucial to distinguish NR from ER. Using high statistical calibration data from tritiated methane, AmBe and other sources in XENON100, the ER/NR discrimination under different electric fields are measured. The Photon yield and recombination fluctuation of low energy electronic recoils under different fields will also be presented and compared to results from NEST and other experiments, which is crucial to understanding the response of liquid xenon detectors in the energy regime of searching dark matter.

  9. A comparison of the microbicidal effectiveness of gamma rays and high and low energy electron radiations

    DEFF Research Database (Denmark)

    Tallentire, A.; Miller, Arne; Helt-Hansen, Jakob

    2010-01-01

    The radiation response of spores of Bacillus pumilus were examined for irradiation with cobalt 60 photons, 10 MeV electrons and low energy electrons at 100 and 80 keV. The responses were found to be the same for all types of radiation within the measurement uncertainties and were also in agreement...

  10. The surface magnetization study of Cr2O3 by spin polarized low energy electron microscopy

    Science.gov (United States)

    Cao, Shi; Wu, Ning; Zhang, Xin; N'diaye, Alpha; Chen, Gong; Schmid, Andreas; Echtenkamp, Will; Lauter, Valeria; Binek, Christian; Dowben, Peter

    2014-03-01

    The boundary magnetization at the surface of a Cr2O3 single crystal has been demonstrated by using spin-polarized low-energy electron microscopy (SPLEEM), indicating net surface spin polarization. This work shows that the placement of Cr2O3 single crystal in the single domain state, will result in net Cr2O3 spin polarization at the boundary, even in the presence of a gold overlayer. There are indications that the spin-polarized low-energy electron microscopy (SPLEEM) contrast for the two polarizations states is different. In addition, the boundary magnetization protected by the symmetry exists despite of the surface roughness/softness which was studied by the non-spin neutron reflectometry and low energy electron diffraction. Unoccupied surface oxygen sites and chromium sites are possible mechanism contributing to the surface ``softness,'' which will be discussed.

  11. Revealing the Mechanism of Low-Energy Electron Yield Enhancement from Sensitizing Nanoparticles

    CERN Document Server

    Verkhovtsev, Alexey V; Solov'yov, Andrey V

    2014-01-01

    We provide a physical explanation for enhancement of the low-energy electron production by sensitizing nanoparticles due to irradiation by fast ions. It is demonstrated that a significant increase in the number of emitted electrons arises from the collective electron excitations in the nanoparticle. We predict a new mechanism of the yield enhancement due to the plasmon excitations and quantitatively estimate its contribution to the electron production. Revealing the nanoscale mechanism of the electron yield enhancement, we provide an efficient tool for evaluating the yield of emitted electron from various sensitizers. It is shown that the number of low-energy electrons generated by the gold and platinum nanoparticles of a given size exceeds that produced by the equivalent volume of water and by other metallic (e.g., gadolinium) nanoparticles by an order of magnitude. This observation emphasizes the sensitization effect of the noble metal nanoparticles and endorses their application in novel technologies of ca...

  12. Emittance minimization at the ELBE superconducting electron gun

    Energy Technology Data Exchange (ETDEWEB)

    Moeller, K.; Arnold, A.; Lu, P.; Murcek, P.; Teichert, J.; Vennekate, H.; Xiang, R.

    2014-07-01

    The transverse emittance is one of the most important quantities which characterize the quality of an electron source. For high quality experiments low beam emittance is required. By means of theoretical considerations and simulation calculations we have studied how the emittance of the Rossendorf superconducting radio-frequency photoelectron source (SRF gun) can be minimized. It turned out that neither a solenoid magnet nor the effect of space charge forces is needed to create a pronounced emittance minimum. The minimum appears by just adjusting the starting phase of the electron bunch with respect to the RF phase of the gun in a suitable way. Investigation of various correlations between the properties of the beam particles led to an explanation on how the minimum comes about. It is shown that the basic mechanism of minimization is the fact that the longitudinal properties of the particles (energy) are strongly influenced by the starting phase. Due to the coupling of the longitudinal and transverse degrees of freedom by the relativistic equation of motion the transverse degrees of freedom and thereby the emittance can be strongly influenced by the starting phase as well. The results obtained in this study will be applied to minimize the emittance in the commissioning phase of the SRF gun.

  13. Imaging the potential distribution of charged adsorbates on graphene by low-energy electron holography

    CERN Document Server

    Latychevskaia, Tatiana; Escher, Conrad; Fink, Hans-Werner

    2016-01-01

    While imaging individual atoms can routinely be achieved in high resolution transmission electron microscopy, visualizing the potential distribution of individually charged adsorbates leading to a phase shift of the probing electron wave is still a challenging task. Since low-energy electrons are sensitive to localized potential gradients, we employed this tool in the 30 eV kinetic energy range to visualize the potential distribution of localized charged adsorbates present on free-standing graphene.

  14. A microwave chip-based beam splitter for low-energy guided electrons

    OpenAIRE

    Hammer, Jakob; Thomas, Sebastian; Weber, Philipp; Hommelhoff, Peter

    2014-01-01

    We demonstrate the splitting of a low-energy electron beam by means of a microwave pseudopotential formed above a planar chip substrate. Beam splitting arises from smoothly transforming the transverse guiding potential for an electron beam from a single-well harmonic confinement into a double-well, thereby generating two separated output beams with $5\\,$mm lateral spacing. Efficient beam splitting is observed for electron kinetic energies up to $3\\,$eV, in excellent agreement with particle tr...

  15. Enhancement of low-energy electron emission in 2D radioactive films

    Science.gov (United States)

    Pronschinske, Alex; Pedevilla, Philipp; Murphy, Colin J.; Lewis, Emily A.; Lucci, Felicia R.; Brown, Garth; Pappas, George; Michaelides, Angelos; Sykes, E. Charles H.

    2015-09-01

    High-energy radiation has been used for decades; however, the role of low-energy electrons created during irradiation has only recently begun to be appreciated. Low-energy electrons are the most important component of radiation damage in biological environments because they have subcellular ranges, interact destructively with chemical bonds, and are the most abundant product of ionizing particles in tissue. However, methods for generating them locally without external stimulation do not exist. Here, we synthesize one-atom-thick films of the radioactive isotope 125I on gold that are stable under ambient conditions. Scanning tunnelling microscopy, supported by electronic structure simulations, allows us to directly observe nuclear transmutation of individual 125I atoms into 125Te, and explain the surprising stability of the 2D film as it underwent radioactive decay. The metal interface geometry induces a 600% amplification of low-energy electron emission (<10 eV; ref. ) compared with atomic 125I. This enhancement of biologically active low-energy electrons might offer a new direction for highly targeted nanoparticle therapies.

  16. Low energy electron generator design and depth dose prediction for micro-superficies tumors treatment purposes

    Science.gov (United States)

    Khorshidi, Abdollah; Rajaee, Azimeh; Ahmadinejad, Marjan; Ghoranneviss, Mahmood; Ettelaee, Mehdi

    2014-09-01

    We investigate deposited energy and linear energy transfer (LET) of low energy ejection electrons in air and water layers of a generator design via a plasma source. A structured model of a concave cold cathode electron generator was designed and simulated by using Monte Carlo n-particle version X 2.7.0 (MCNPX) code. A negative dc high voltage was applied to a concave cathode up to -12 kV to determine electron energy activity. Results determined that the geometric dimensions of field size toward the anode increased in relation to the angle of the conic beam, widening the accumulated bulks. The increased field size increased the anode current, which also resulted in an increase of electron energy, a reduction in LET, a stretched build-up area and a dose curve that shifted to a higher depth. The biological effect of low energy electron radiation can be increased with an increase of LET; as the depth dose decreased, the electron energy increased at the same time. The study of electron irradiation as a conic beam from an electron generator may provide an accurate investigation of the indirect effect of low energy electrons on bystander cells.

  17. Industrial application of electron sources with plasma emitters

    CERN Document Server

    Belyuk, S I; Rempe, N G

    2001-01-01

    Paper contains a description, operation, design and parameters of electron sources with plasma emitters. One presents examples of application of these sources as part of automated electron-beam welding lines. Paper describes application of such sources for electron-beam deposition of composite powders. Electron-beam deposition is used to rebuild worn out part and to increase strength of new parts of machines and tools. Paper presents some examples of rebuilding part and the advantages gained in this case

  18. XPS STUDY ON DNA DAMAGE BY LOW-ENERGY ELECTRON IRRADIATION

    Energy Technology Data Exchange (ETDEWEB)

    Noh, Hyung Ah; Cho, Hyuck [Chungnam National University, Physics Department, Daejeon (Korea, Republic of)

    2011-12-15

    After the first report that electrons with sub-ionization energy of DNA could cause single strand breaks or double strand breaks to DNA, there have been various studies to investigate the mechanisms of DNA damage by low-energy electrons. In this paper, we examined the possibility of using X-ray photoelectron spectroscopy (XPS) to analyze the dissociation patterns of the molecular bonds by electron irradiation on DNA thin films and tried to establish the method as a general tool for studying the radiation damage of biomolecules by low energy electrons. For the experiment, pBR322 plasmid DNA solution was formed into the films on tantalum plates by lyophilization and was irradiated by 5-eV electrons. Un-irradiated and irradiated DNA films were compared and analyzed using the XPS technique.

  19. Low-Energy Electron-Induced Transformations in Organolead Halide Perovskite.

    Science.gov (United States)

    Milosavljević, Aleksandar R; Huang, Weixin; Sadhu, Subha; Ptasinska, Sylwia

    2016-08-16

    Methylammonium lead iodide perovskite (MAPbI3 ), a prototype material for potentially high-efficient and low-cost organic-inorganic hybrid perovskite solar cells, has been investigated intensively in recent years. A study of low-energy electron-induced transformations in MAPbI3 is presented, performed by combining controlled electron-impact irradiation with X-ray photoelectron spectroscopy and scanning electron microscopy. Changes were observed in both the elemental composition and the morphology of irradiated MAPbI3 thin films as a function of the electron fluence for incident energies from 4.5 to 60 eV. The results show that low-energy electrons can affect structural and chemical properties of MAPbI3 . It is proposed that the transformations are triggered by the interactions with the organic part of the material (methylammonium), resulting in the MAPbI3 decomposition and aggregation of the hydrocarbon layer.

  20. The EIGER detector for low-energy electron microscopy and photoemission electron microscopy.

    Science.gov (United States)

    Tinti, G; Marchetto, H; Vaz, C A F; Kleibert, A; Andrä, M; Barten, R; Bergamaschi, A; Brückner, M; Cartier, S; Dinapoli, R; Franz, T; Fröjdh, E; Greiffenberg, D; Lopez-Cuenca, C; Mezza, D; Mozzanica, A; Nolting, F; Ramilli, M; Redford, S; Ruat, M; Ruder, Ch; Schädler, L; Schmidt, Th; Schmitt, B; Schütz, F; Shi, X; Thattil, D; Vetter, S; Zhang, J

    2017-09-01

    EIGER is a single-photon-counting hybrid pixel detector developed at the Paul Scherrer Institut, Switzerland. It is designed for applications at synchrotron light sources with photon energies above 5 keV. Features of EIGER include a small pixel size (75 µm × 75 µm), a high frame rate (up to 23 kHz), a small dead-time between frames (down to 3 µs) and a dynamic range up to 32-bit. In this article, the use of EIGER as a detector for electrons in low-energy electron microscopy (LEEM) and photoemission electron microscopy (PEEM) is reported. It is demonstrated that, with only a minimal modification to the sensitive part of the detector, EIGER is able to detect electrons emitted or reflected by the sample and accelerated to 8-20 keV. The imaging capabilities are shown to be superior to the standard microchannel plate detector for these types of applications. This is due to the much higher signal-to-noise ratio, better homogeneity and improved dynamic range. In addition, the operation of the EIGER detector is not affected by radiation damage from electrons in the present energy range and guarantees more stable performance over time. To benchmark the detector capabilities, LEEM experiments are performed on selected surfaces and the magnetic and electronic properties of individual iron nanoparticles with sizes ranging from 8 to 22 nm are detected using the PEEM endstation at the Surface/Interface Microscopy (SIM) beamline of the Swiss Light Source.

  1. Low-energy electron irradiation induced top-surface nanocrystallization of amorphous carbon film

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Cheng [Institute of Nanosurface Science and Engineering (INSE), Shenzhen University, Shenzhen 518060 (China); Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060 (China); Fan, Xue, E-mail: fanx@szu.edu.cn [Institute of Nanosurface Science and Engineering (INSE), Shenzhen University, Shenzhen 518060 (China); Diao, Dongfeng, E-mail: dfdiao@szu.edu.cn [Institute of Nanosurface Science and Engineering (INSE), Shenzhen University, Shenzhen 518060 (China)

    2016-10-30

    Graphical abstract: Low-energy electron irradiation was proposed to nanocrystallize the top-surface of the as-deposited amorphous carbon film, and sp{sup 2} nanocrystallites formed in the film top-surface within 4 nm thickness. Display Omitted - Abstract: We report a low-energy electron irradiation method to nanocrystallize the top-surface of amorphous carbon film in electron cyclotron resonance plasma system. The nanostructure evolution of the carbon film as a function of electron irradiation density and time was examined by transmission electron microscope (TEM) and Raman spectroscopy. The results showed that the electron irradiation gave rise to the formation of sp{sup 2} nanocrystallites in the film top-surface within 4 nm thickness. The formation of sp{sup 2} nanocrystallite was ascribed to the inelastic electron scattering in the top-surface of carbon film. The frictional property of low-energy electron irradiated film was measured by a pin-on-disk tribometer. The sp{sup 2} nanocrystallized top-surface induced a lower friction coefficient than that of the original pure amorphous film. This method enables a convenient nanocrystallization of amorphous surface.

  2. An ion guide for the production of a low energy ion beam of daughter products of {alpha}-emitters

    Energy Technology Data Exchange (ETDEWEB)

    Tordoff, B. [Nuclear Physics Group, Schuster Laboratory, Brunswick Street, University of Manchester, Manchester M13 9PL (United Kingdom)]. E-mail: bwt@phys.jyu.fi; Eronen, T. [Department of Physics, University of Jyvaeskylae, P.O. Box 35, 40014 Jyvaeskylae (Finland); Elomaa, V.V. [Department of Physics, University of Jyvaeskylae, P.O. Box 35, 40014 Jyvaeskylae (Finland); Gulick, S. [Ernest Rutherford Physics Building, McGill University, 3600 rue University, Montreal, QC, H3A 2T8 (Canada); Hager, U. [Department of Physics, University of Jyvaeskylae, P.O. Box 35, 40014 Jyvaeskylae (Finland); Karvonen, P. [Department of Physics, University of Jyvaeskylae, P.O. Box 35, 40014 Jyvaeskylae (Finland); Kessler, T. [Department of Physics, University of Jyvaeskylae, P.O. Box 35, 40014 Jyvaeskylae (Finland); Lee, J. [Ernest Rutherford Physics Building, McGill University, 3600 rue University, Montreal, QC, Canada H3A 2T8 (Canada); Moore, I. [Department of Physics, University of Jyvaeskylae, P.O. Box 35, 40014 Jyvaeskylae (Finland); Popov, A. [Petersburg Nuclear Physics Institute, Gatchina, St. Petersburg 188350 (Russian Federation); Rahaman, S. [Department of Physics, University of Jyvaeskylae, P.O. Box 35, 40014 Jyvaeskylae (Finland); Rinta-Antila, S. [Department of Physics, University of Jyvaeskylae, P.O. Box 35, 40014 Jyvaeskylae (Finland); Sonoda, T. [Department of Physics, University of Jyvaeskylae, P.O. Box 35, 40014 Jyvaeskylae (Finland); Aystoe, J. [Department of Physics, University of Jyvaeskylae, P.O. Box 35, 40014 Jyvaeskylae (Finland)

    2006-11-15

    A new ion guide has been modeled and tested for the production of a low energy ({approx}40 kV) ion beam of daughter products of alpha-emitting isotopes. The guide is designed to evacuate daughter recoils originating from the {alpha}-decay of a {sup 233}U source. The source is electroplated onto stainless steel strips and mounted along the inner walls of an ion guide chamber. A combination of electric fields and helium gas flow transport the ions through an exit hole for injection into a mass separator. Ion guide efficiencies for the extraction of {sup 229}Th{sup +} (0.06%), {sup 221}Fr{sup +} (6%) and {sup 217}At{sup +} (6%) beams have been measured. A detailed study of the electric field and gas flow influence on the ion guide efficiency is described for two differing electric field configurations.

  3. An Ion Guide for the Production of a Low Energy Ion Beam of Daughter Products of $\\alpha$-Emitters

    CERN Document Server

    Tordoff, B; Elomaa, V V; Gulick, S; Hager, U; Karvonen, P; Kessler, T; Lee, J; Moore, I; Popov, A; Rahaman, S; Rinta-Antila, S; Sonoda, T; Äystö, J

    2006-01-01

    A new ion guide has been modeled and tested for the production of a low energy ($\\approx$ 40 kV) ion beam of daughter products of alpha-emitting isotopes. The guide is designed to evacuate daughter recoils originating from the $\\alpha$-decay of a $^{233}$U source. The source is electroplated onto stainless steel strips and mounted along the inner walls of an ion guide chamber. A combination of electric fields and helium gas flow transport the ions through an exit hole for injection into a mass separator. Ion guide efficiencies for the extraction of $^{229}$Th$^{+}$ (0.06%), $^{221}$Fr$^{+}$ (6%), and $^{217}$At$^{+}$ (6%) beams have been measured. A detailed study of the electric field and gas flow influence on the ion guide efficiency is described for two differing electric field configurations.

  4. Growing oxide thin films in a low-energy electron microscope

    NARCIS (Netherlands)

    Torren, van der A.J.H.

    2016-01-01

    By combining low-energy electron microscopy (LEEM) with pulsed laser deposition (PLD), we have created a unique set-up to study the first stages of growth of complex metal oxides. We demonstrate this by investigating the growth of SrTiO3 (STO) and LaAlO3 (LAO) on STO in real-time. We follow growth b

  5. Guiding of low-energy electrons by highly ordered Al2 O3 nanocapillaries

    DEFF Research Database (Denmark)

    Milosavljević, A.R.; Víkor, G.; Pešić, Z.D.;

    2007-01-01

    We report an experimental study of guided transmission of low-energy (200-350 eV) electrons through highly ordered Al2 O3 nanocapillaries with large aspect ratio (140 nm diameter and 15 μm length). The nanochannel array was prepared using self-ordering phenomena during a two-step anodization proc...

  6. Low energy high current pulsed electron beam treatment for improving surface microstructure and properties

    Energy Technology Data Exchange (ETDEWEB)

    Wu, J; Allain-Bonasso, N; Zhang, X D; Hao, S Z; Grosdider, T; Dong, C [Laboratoire d' Etude des Textures et Applications aux Materiaux (LETAM, UMR-CNRS 3143), Universite Paul Verlaine-Metz, Ile du Saulcy, 57045 Metz (France); Zou, J X, E-mail: jiang.wu@univ-metz.fr, E-mail: thierry.grosdidier@univ-metz.fr [National Engineering Research Center of Light Alloy Net Forming, Shanghai Jiao Tong University, Shanghai 200240 (China)

    2010-06-15

    Low energy high current pulsed electron beam (LEHCPEB) is a fairly new technique for surface modifications authorizing improvement in wear and corrosion properties as well as texture changes and hardening. This contribution highlights some microstructure modifications encountered at the surface of HCPEB treated steels and bulk metallic glasses taking into account the effects of surface melting and the effects of the induced stress.

  7. Development of a pepper-pot emittance meter for diagnostics of low-energy multiply charged heavy ion beams extracted from an ECR ion source

    Energy Technology Data Exchange (ETDEWEB)

    Nagatomo, T., E-mail: nagatomo@riken.jp; Kase, M.; Kamigaito, O.; Nakagawa, T. [Nishina Center for Accelerator Based Science, RIKEN, Wako, Saitama 351-0198 (Japan); Tzoganis, V. [Nishina Center for Accelerator Based Science, RIKEN, Wako, Saitama 351-0198 (Japan); Cockcroft Institute, Daresbury, Warrington WA4 4AD (United Kingdom); Department of Physics, University of Liverpool, Liverpool, Merseyside L69 3BX (United Kingdom)

    2016-02-15

    Several fluorescent materials were tested for use in the imaging screen of a pepper-pot emittance meter that is suitable for investigating the beam dynamics of multiply charged heavy ions extracted from an ECR ion source. SiO{sub 2} (quartz), KBr, Eu-doped CaF{sub 2}, and Tl-doped CsI crystals were first irradiated with 6.52-keV protons to determine the effects of radiation damage on their fluorescence emission properties. For such a low-energy proton beam, only the quartz was found to be a suitable fluorescent material, since the other materials suffered a decay in fluorescence intensity with irradiation time. Subsequently, quartz was irradiated with heavy {sup 12}C{sup 4+}, {sup 16}O{sup 4+}, and {sup 40}Ar{sup 11+} ions, but it was found that the fluorescence intensity decreased too rapidly to measure the emittance of these heavy-ion beams. These results suggest that a different energy loss mechanism occurs for heavier ions and for protons.

  8. Development of a pepper-pot emittance meter for diagnostics of low-energy multiply charged heavy ion beams extracted from an ECR ion source

    Science.gov (United States)

    Nagatomo, T.; Tzoganis, V.; Kase, M.; Kamigaito, O.; Nakagawa, T.

    2016-02-01

    Several fluorescent materials were tested for use in the imaging screen of a pepper-pot emittance meter that is suitable for investigating the beam dynamics of multiply charged heavy ions extracted from an ECR ion source. SiO2 (quartz), KBr, Eu-doped CaF2, and Tl-doped CsI crystals were first irradiated with 6.52-keV protons to determine the effects of radiation damage on their fluorescence emission properties. For such a low-energy proton beam, only the quartz was found to be a suitable fluorescent material, since the other materials suffered a decay in fluorescence intensity with irradiation time. Subsequently, quartz was irradiated with heavy 12C4+, 16O4+, and 40Ar11+ ions, but it was found that the fluorescence intensity decreased too rapidly to measure the emittance of these heavy-ion beams. These results suggest that a different energy loss mechanism occurs for heavier ions and for protons.

  9. Guide on the use of low energy electron beams for microbiological decontamination of surfaces

    DEFF Research Database (Denmark)

    Miller, Arne; Helt-Hansen, Jakob; Gondim, Ondina

    This Guide describes the validation and routine monitoring of microbiological decontamination of surfaces by low energy electron beams (100-200 keV). The Guide is mainly based on experience gained in connection with installation of electron beam systems for surface decontamination of pre-steriliz......This Guide describes the validation and routine monitoring of microbiological decontamination of surfaces by low energy electron beams (100-200 keV). The Guide is mainly based on experience gained in connection with installation of electron beam systems for surface decontamination of pre......-sterilized containers at several aseptic filling lines at pharmaceutical manufacturers. Its main emphasis is on the dosimetric measurements that should be carried out for the validation of the decontamination process and on establishing the appropriate effective dose. Other aspects such as use of measurement...... uncertainties and formation of radiation induced by-products are also addressed....

  10. Low energy electron loss peaks of CuInTe/sub 2/

    Energy Technology Data Exchange (ETDEWEB)

    Kleint, C. (Karl-Marx-Universitaet, Leipzig (German Democratic Republic). Sektion Physik); Schulze, S. (Technische Hochschule, Karl-Marx-Stadt (German Democratic Republic). Sektion Physik/Elektronische Bauelemente); Tomlinson, R.D. (Salford Univ. (UK). Dept. of Electrical Engineering)

    1982-09-01

    Reflection low energy electron loss spectra were observed from CuInTe/sub 2/ monocrystals. The spectra were taken with a LEED system to obtain the first derivative of the scattered electron energy distribution using primary energies of 50, 90, and 190 eV. The second derivative and the loss maxima energies have been determined after a smoothing procedure. The loss peaks are coordinated to plasmon features, surfaces states, and interband transitions.

  11. Low-energy electron holographic imaging of gold nanorods supported by ultraclean graphene

    Energy Technology Data Exchange (ETDEWEB)

    Longchamp, Jean-Nicolas, E-mail: longchamp@physik.uzh.ch; Escher, Conrad; Latychevskaia, Tatiana; Fink, Hans-Werner

    2014-10-15

    An ideal support for an electron microscopy should be as thin as possible and be able to interact as little as possible with the primary electrons. Since graphene is atomically thin and made up of carbon atoms arranged in a honeycomb lattice, the potential to use graphene as a substrate in electron microscopy is enormous. Until now graphene has hardly ever been used for this purpose because the cleanliness of freestanding graphene before or after deposition of the objects of interest was insufficient. We demonstrate here by means of low-energy electron holographic imaging that freestanding graphene prepared with a platinum-metal catalysis method remains ultraclean even after re-exposure to ambient conditions and deposition of gold nanorods from the liquid phase. In the holographic reconstruction of gold particles the organic shell surrounding the objects is apparent while it is not detectable in SEM images of the very same sample, demonstrating the tremendous potential of low-energy electron holography for imaging of graphene-supported single biomolecules. - Highlights: • Deposition of nanometre-sized objects onto ultraclean freestanding graphene. • TEM imaging of ultraclean freestanding graphene. • Low-energy electron imaging of gold-nanorods deposited onto freestanding graphene.

  12. Overview of Alternative Bunching and Current-shaping Techniques for Low-Energy Electron Beams

    Energy Technology Data Exchange (ETDEWEB)

    Piot, Philippe [Northern Illinois U.

    2015-12-01

    Techniques to bunch or shape an electron beam at low energies (E <15 MeV) have important implications toward the realization of table-top radiation sources [1] or to the design of compact multi-user free-electron lasers[2]. This paper provides an overview of alternative methods recently developed including techniques such as wakefield-based bunching, space-charge-driven microbunching via wave-breaking [3], ab-initio shaping of the electron-emission process [4], and phase space exchangers. Practical applications of some of these methods to foreseen free-electron-laser configurations are also briefly discussed [5].

  13. Microwave Chip-Based Beam Splitter for Low-Energy Guided Electrons.

    Science.gov (United States)

    Hammer, Jakob; Thomas, Sebastian; Weber, Philipp; Hommelhoff, Peter

    2015-06-26

    We present a novel beam splitter for low-energy electrons using a micro-structured guiding potential created above the surface of a planar microwave chip. Beam splitting arises from smoothly transforming the transverse guiding potential for an electron beam from a single-well harmonic confinement into a double well, thereby generating two separated output beams with 5 mm lateral spacing. Efficient beam splitting is observed for electron kinetic energies up to 3 eV, in excellent agreement with particle tracking simulations. We discuss prospects of this novel beam splitter approach for electron-based quantum matter-wave optics experiments.

  14. D-mu-A new concept in industrial low-energy electron dosimetry

    DEFF Research Database (Denmark)

    Helt-Hansen, Jakob; Miller, Arne; Sharpe, Peter

    2010-01-01

    Irradiation with low-energy electrons (100–300 keV) results in dose gradients across the thickness of the dosimeters that are typically used for dose measurement at these energies. This leads to different doses being measured with different thickness dosimeters irradiated at the same electron beam...... it is therefore possible to calibrate and measure doses from low-energy electron irradiations with measurement traceability to national standards......., resulting in difficulties in providing traceable dose measurements using reference dosimeters. In order to overcome these problems a new concept is introduced of correcting all measured doses to the average dose in the first micrometer—Dμ. We have applied this concept to dose measurements with dosimeters...

  15. Transparency of graphene for low-energy electrons measured in a vacuum-triode setup

    Directory of Open Access Journals (Sweden)

    G. Hassink

    2015-07-01

    Full Text Available Graphene, being an atomically thin conducting sheet, is a candidate material for gate electrodes in vacuum electronic devices, as it may be traversed by low-energy electrons. The transparency of graphene to electrons with energies between 2 and 40 eV has been measured by using an optimized vacuum-triode setup. The measured graphene transparency equals ∼60% in most of this energy range. Based on these results, nano-patterned sheets of graphene or of related two-dimensional materials are proposed as gate electrodes for ambipolar vacuum devices.

  16. Emittance Measurements from a Laser Driven Electron Injector

    Energy Technology Data Exchange (ETDEWEB)

    Reis, David A

    2003-07-28

    The Gun Test Facility (GTF) at the Stanford Linear Accelerator Center was constructed to develop an appropriate electron beam suitable for driving a short wavelength free electron laser (FEL) such as the proposed Linac Coherent Light Source (LCLS). For operation at a wavelength of 1.5 {angstrom}, the LCLS requires an electron injector that can produce an electron beam with approximately 1 {pi} mm-mrad normalized rms emittance with at least 1 nC of charge in a 10 ps or shorter bunch. The GTF consists of a photocathode rf gun, emittance-compensation solenoid, 3 m linear accelerator (linac), drive laser, and diagnostics to measure the beam. The rf gun is a symmetrized 1.6 cell, s-band high gradient, room temperature, photocathode structure. Simulations show that this gun when driven by a temporally and spatially shaped drive laser, appropriately focused with the solenoid, and further accelerated in linac can produce a beam that meets the LCLS requirements. This thesis describes the initial characterization of the laser and electron beam at the GTF. A convolved measurement of the relative timing between the laser and the rf phase in the gun shows that the jitter is less than 2.5 ps rms. Emittance measurements of the electron beam at 35 MeV are reported as a function of the (Gaussian) pulse length and transverse profile of the laser as well as the charge of the electron beam at constant phase and gradient in both the gun and linac. At 1 nC the emittance was found to be {approx} 13 {pi} mm-mrad for 5 ps and 8 ps long laser pulses. At 0.5 nC the measured emittance decreased approximately 20% in the 5 ps case and 40% in the 8 ps case. These measurements are between 40-80% higher than simulations for similar experimental conditions. In addition, the thermal emittance of the electron beam was measured to be 0.5 {pi} mm-mrad.

  17. Micromagnetism in (001) magnetite by spin-polarized low-energy electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Figuera, Juan de la, E-mail: juan.delafiguera@iqfr.csic.es [Instituto de Química-Física “Rocasolano”, CSIC, Madrid 28006 (Spain); Vergara, Lucía [Instituto de Química-Física “Rocasolano”, CSIC, Madrid 28006 (Spain); N' Diaye, Alpha T. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Quesada, Adrian [Instituto de Cerámica y Vidrio, CSIC, Calle Kelsen 5, 28049, Madrid (Spain); Schmid, Andreas K. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

    2013-07-15

    Spin-polarized low-energy electron microscopy was used to image a magnetite crystal with (001) surface orientation. Sets of spin-dependent images of magnetic domain patterns observed in this surface were used to map the direction of the magnetization vector with high spatial and angular resolution. We find that domains are magnetized along the surface <110> directions, and domain wall structures include 90° and 180° walls. A type of unusually curved domain walls are interpreted as Néel-capped surface terminations of 180° Bloch walls. - Highlights: ► The (001) surface of magnetite is imaged by spin-polarized low-energy electron microscopy. ► The magnetic domain microstructure is resolved. ► Magnetic easy axes in this surface are found to be along <110> directions. ► Magnetic domain wall structures include wide Néel-caps.

  18. Low-energy electronic states of carbon nanocones in an electric field

    Institute of Scientific and Technical Information of China (English)

    Jun-Liang Chen; Ming-Horng Su; Chi-Chuan Hwang; Jian-Ming Lu; Chia-Chang Tsai

    2010-01-01

    The low-energy electronic states and energy gaps of carbon nanocones in an electric field are studied using a single-p-band tight-binding model. The analysis considers five perfect carbon nanocones with disclination angles of 60°, 120°, 180°, 240°and 300°, respectively. The numerical results reveal that the low-energy electronic states and energy gaps of a carbon nanocones are highly sensitive to its geometric shape (i.e. the disclination angle and height), and to the direction and magnitude of an electric field. The electric field causes a strong modulation of the state energies and energy gaps of the nanocones, changes their Fermi levels, and induces zero-gap transitions. The energy-gap modulation effect becomes particularly pronounced at higher strength of the applied electric field, and is strongly related to the geometric structure of the nanocone.

  19. Electronic structure of nitinol surfaces oxidized by low-energy ion bombardment

    Energy Technology Data Exchange (ETDEWEB)

    Petravic, M., E-mail: mpetravic@phy.uniri.hr; Varasanec, M.; Peter, R.; Kavre, I. [Department of Physics and Center for Micro and Nano Sciences and Technologies, University of Rijeka, 51000 Rijeka (Croatia); Metikos-Hukovic, M. [Department of Electrochemistry, Faculty of Chemical Engineering and Technology, University of Zagreb, 10000 Zagreb (Croatia); Yang, Y.-W. [National Synchrotron Radiation Research Center, Hsinchu 30077, Taiwan (China)

    2014-06-28

    We have studied the electronic structure of nitinol exposed to low-energy oxygen-ion bombardment, using x-ray photoemission spectroscopy (XPS) and near-edge x-ray absorption fine structure (NEXAFS) spectroscopy. XPS spectra reveal a gradual transformation of nitinol surfaces into TiO{sub 2} with increased dose of implanted oxygen. No oxidation of Ni atoms has been detected. NEXAFS spectra around O K-edge and Ti L{sub 2,3}-edge, reflecting the element-specific partial density of empty electronic states, exhibit features, which can be attributed to the creation of molecular orbitals, crystal field splitting, and the absence of long-range order, characteristic of the amorphous TiO{sub 2}. Based on these results, we discuss the oxidation kinetics of nitinol under low-energy oxygen-ion bombardment.

  20. Electronic structure of nitinol surfaces oxidized by low-energy ion bombardment

    Science.gov (United States)

    Petravic, M.; Varasanec, M.; Peter, R.; Kavre, I.; Metikos-Hukovic, M.; Yang, Y.-W.

    2014-06-01

    We have studied the electronic structure of nitinol exposed to low-energy oxygen-ion bombardment, using x-ray photoemission spectroscopy (XPS) and near-edge x-ray absorption fine structure (NEXAFS) spectroscopy. XPS spectra reveal a gradual transformation of nitinol surfaces into TiO2 with increased dose of implanted oxygen. No oxidation of Ni atoms has been detected. NEXAFS spectra around O K-edge and Ti L2,3-edge, reflecting the element-specific partial density of empty electronic states, exhibit features, which can be attributed to the creation of molecular orbitals, crystal field splitting, and the absence of long-range order, characteristic of the amorphous TiO2. Based on these results, we discuss the oxidation kinetics of nitinol under low-energy oxygen-ion bombardment.

  1. Using a CCD for the direct detection of electrons in a low energy space plasma spectrometer

    Science.gov (United States)

    Bedington, R.; Kataria, D.; Walton, D.

    2012-01-01

    An E2V CCD64 back-illuminated, ion-implanted CCD (charge-coupled device) has been used as a direct electron imaging detector with CATS (Conceptual And Tiny Spectrometer), a highly miniaturised prototype plasma analyser head. This is in place of an MCP (microchannel plate) with a position sensing anode which would more conventionally be used as a detector in traditional low energy space plasma analyser instruments. The small size of CATS however makes it well matched to the size of the CCD, and the ion implants reduce the depth of the CCD backside electron potential well making it more sensitive to lower energy electrons than standard untreated silicon. Despite ionisation damage from prolonged exposure to excessively energetic electrons, the CCD has been able to detect electrons with energies above 500eV, at temperatures around room temperature. Using both a long integration 'current measuring' mode and a short integration `electron counting' mode it has been used to image the low energy electrons exiting the analyser, enhancing our understanding of the CATS electrostatic optics. The CCD has been selected as the detector for use with CATS for an instrument on a low-altitude student sounding rocket flight. Although it cannot detect the lowest energy electrons that an MCP can detect, and it is more sensitive to stray light, the low voltages required, the lack of vacuum requirements and its novelty and availability made it the most attractive candidate detector.

  2. Electron capture collisions involving low-energy highly-stripped projectiles

    Energy Technology Data Exchange (ETDEWEB)

    Cocke, C.L.; Gray, T.J.; Justiniano, E.; Can, C.; Waggoner, B.; Varghese, S.L.; Mann, R. (Kansas State Univ., Manhattan (USA). Dept. of Physics)

    1983-01-01

    Recoil ions produced by fast-ion bombardment of dilute gases are in use at Kansas State University as a source of low-energy highly-charged ions to study electron capture by these projectiles on neutral targets in the 10/sup 6/-10/sup 7/ cm s/sup -1/ velocity range. A progress report on several phases of this program is summarized.

  3. Intrinsic normalized emittance growth in laser-driven electron accelerators

    Science.gov (United States)

    Migliorati, M.; Bacci, A.; Benedetti, C.; Chiadroni, E.; Ferrario, M.; Mostacci, A.; Palumbo, L.; Rossi, A. R.; Serafini, L.; Antici, P.

    2013-01-01

    Laser-based electron sources are attracting strong interest from the conventional accelerator community due to their unique characteristics in terms of high initial energy, low emittance, and significant beam current. Extremely strong electric fields (up to hundreds of GV/m) generated in the plasma allow accelerating gradients much higher than in conventional accelerators and set the basis for achieving very high final energies in a compact space. Generating laser-driven high-energy electron beam lines therefore represents an attractive challenge for novel particle accelerators. In this paper we show that laser-driven electrons generated by the nowadays consolidated TW laser systems, when leaving the interaction region, are subject to a very strong, normalized emittance worsening which makes them quickly unusable for any beam transport. Furthermore, due to their intrinsic beam characteristics, controlling and capturing the full beam current can only be achieved improving the source parameters.

  4. Electron Cloud at Low Emittance in CesrTA

    CERN Document Server

    Palmer, Mark; Billing, Michael; Calvey, Joseph; Conolly, Christopher; Crittenden, James; Dobbins, John; Dugan, Gerald; Eggert, Nicholas; Fontes, Ernest; Forster, Michael; Gallagher, Richard; Gray, Steven; Greenwald, Shlomo; Hartill, Donald; Hopkins, Walter; Kreinick, David; Kreis, Benjamin; Leong, Zhidong; Li, Yulin; Liu, Xianghong; Livezey, Jesse; Lyndaker, Aaron; Makita, Junki; McDonald, Michael; Medjidzade, Valeri; Meller, Robert; O'Connell, Tim; Peck, Stuart; Peterson, Daniel; Ramirez, Gabriel; Rendina, Matthew; Revesz, Peter; Rider, Nate; Rice, David; Rubin, David; Sagan, David; Savino, James; Schwartz, Robert; Seeley, Robert; Sexton, James; Shanks, James; Sikora, John; Smith, Eric; Strohman, Charles; Williams, Heather; Antoniou, Fanouria; Calatroni, Sergio; Gasior, Marek; Jones, Owain Rhodri; Papaphilippou, Yannis; Pfingstner, Juergen; Rumolo, Giovanni; Schmickler, Hermann; Taborelli, Mauro; Asner, David; Boon, Laura; Garfinkel, Arthur; Byrd, John; Celata, Christine; Corlett, John; De Santis, Stefano; Furman, Miguel; Jackson, Alan; Kraft, Rick; Munson, Dawn; Penn, Gregory; Plate, David; Venturini, Marco; Carlson, Benjamin; Demma, Theo; Dowd, Rohan; Flanagan, John; Jain, Puneet; Kanazawa, Ken-ichi; Kubo, Kiyoshi; Ohmi, Kazuhito; Sakai, Hiroshi; Shibata, Kyo; Suetsugu, Yusuke; Tobiyama, Makoto; Gonnella, Daniel; Guo, Weiming; Harkay, Katherine; Holtzapple, Robert; Jones, James; Wolski, Andrzej; Kharakh, David; Ng, Johnny; Pivi, Mauro; Wang, Lanfa; Ross, Marc; Tan, Cheng-Yang; Zwaska, Robert; Schachter, Levi; Wilkinson, Eric

    2010-01-01

    The Cornell Electron Storage Ring (CESR) has been reconfigured as a test accelerator (CesrTA) for a program of electron cloud (EC) research at ultra low emittance. The instrumentation in the ring has been upgraded with local diagnostics for measurement of cloud density and with improved beam diagnostics for the characterization of both the low emittance performance and the beam dynamics of high intensity bunch trains interacting with the cloud. A range of EC mitigation methods have been deployed and tested and their effectiveness is discussed. Measurements of the electron cloud’s effect on the beam under a range of conditions are discussed along with the simulations being used to quantitatively understand these results

  5. Electron Cloud at Low Emittance in CesrTA

    Energy Technology Data Exchange (ETDEWEB)

    Palmer, Mark; /Cornell U., CLASSE; Alexander, James; /Cornell U., CLASSE; Billing, Michael; /Cornell U., CLASSE; Calvey, Joseph; /Cornell U., CLASSE; Conolly, Christopher; /Cornell U., CLASSE; Crittenden, James; /Cornell U., CLASSE; Dobbins, John; /Cornell U., CLASSE; Dugan, Gerald; /Cornell U., CLASSE; Eggert, Nicholas; /Cornell U., CLASSE; Fontes, Ernest; /Cornell U., CLASSE; Forster, Michael; /Cornell U., CLASSE; Gallagher, Richard; /Cornell U., CLASSE; Gray, Steven; /Cornell U., CLASSE; Greenwald, Shlomo; /Cornell U., CLASSE; Hartill, Donald; /Cornell U., CLASSE; Hopkins, Walter; /Cornell U., CLASSE; Kreinick, David; /Cornell U., CLASSE; Kreis, Benjamin; /Cornell U., CLASSE; Leong, Zhidong; /Cornell U., CLASSE; Li, Yulin; /Cornell U., CLASSE; Liu, Xianghong; /Cornell U., CLASSE /Cornell U., CLASSE /Cornell U., CLASSE /Cornell U., CLASSE /Cornell U., CLASSE /Cornell U., CLASSE /Cornell U., CLASSE /Cornell U., CLASSE /Cornell U., CLASSE /Cornell U., CLASSE /Cornell U., CLASSE /Cornell U., CLASSE /Cornell U., CLASSE /Cornell U., CLASSE /Cornell U., CLASSE /Cornell U., CLASSE /Cornell U., CLASSE /Cornell U., CLASSE /Cornell U., CLASSE /Cornell U., CLASSE /Cornell U., CLASSE /Cornell U., CLASSE /Cornell U., CLASSE /Cornell U., CLASSE /Cornell U., CLASSE /Cornell U., CLASSE /CERN /CERN /CERN /CERN /CERN /CERN; /more authors..

    2012-07-06

    The Cornell Electron Storage Ring (CESR) has been reconfigured as a test accelerator (CesrTA) for a program of electron cloud (EC) research at ultra low emittance. The instrumentation in the ring has been upgraded with local diagnostics for measurement of cloud density and with improved beam diagnostics for the characterization of both the low emittance performance and the beam dynamics of high intensity bunch trains interacting with the cloud. A range of EC mitigation methods have been deployed and tested and their effectiveness is discussed. Measurements of the electron cloud's effect on the beam under a range of conditions are discussed along with the simulations being used to quantitatively understand these results.

  6. Electron Cloud at Low Emittance in CesrTA

    Energy Technology Data Exchange (ETDEWEB)

    Alexander, J. P.; Billing, M. G.; Calvey, J.; Crittenden, J. A.; Dugan, G.; Eggert, N.; Forster, M.; Greenwald, S.; Hartill, D. L.; Hopkins, W. H.; Kreinick, D. L.; Li, Y.; Liu, X.; Livezey, J. A.; Meller, R.; Peck, S.; Peterson, D. P.; Rice, D.; Rider, N.; Rubin, D.; Sagan, D.; Schwartz, R.; Shanks, J. P.; Sikora, J.; Harkay, K. C.; Antoniou, F.; Calatroni, S.; Gasior, M.; Papaphilippou, Y.; Pfingstner, J.; Rumolo, G.; Schmickler, H.; Taborelli, M.; Holtzapple, R.; Jones, J.; Wolski, A.; Tan, C.Y.; Zwaska, R. M; Flanagan, J. W.; Kanazawa, K.I.; Sakai, H.; Shibata, K.; Suetsugu, Y.; Byrd, J.; Corlett, J.; De Santis, S.; Furman, M.; Kraft, R.; Munson, D. V.; Penn, G.; Plate, D.; Venturini, M.; Pivi, M. T. F.; Wang, L.; Schachter, L.

    2010-05-23

    The Cornell Electron Storage Ring (CESR) has been reconfigured as a test accelerator (CesrTA) for a program of electron cloud (EC) research at ultra low emittance. The instrumentation in the ring has been upgraded with local diagnostics for measurement of cloud density and with improved beam diagnostics for the characterization of both the low emittance performance and the beam dynamics of high intensity bunch trains interacting with the cloud. A range of EC mitigation methods have been deployed and tested and their effectiveness is discussed. Measurements of the electron cloud's effect on the beam under a range of conditions are discussed along with the simulations being used to quantitatively understand these results.

  7. Probing low-energy hyperbolic polaritons in van der Waals crystals with an electron microscope

    KAUST Repository

    Govyadinov, Alexander A.

    2017-07-14

    Van der Waals materials exhibit intriguing structural, electronic, and photonic properties. Electron energy loss spectroscopy within scanning transmission electron microscopy allows for nanoscale mapping of such properties. However, its detection is typically limited to energy losses in the eV range-too large for probing low-energy excitations such as phonons or mid-infrared plasmons. Here, we adapt a conventional instrument to probe energy loss down to 100 meV, and map phononic states in hexagonal boron nitride, a representative van der Waals material. The boron nitride spectra depend on the flake thickness and on the distance of the electron beam to the flake edges. To explain these observations, we developed a classical response theory that describes the interaction of fast electrons with (anisotropic) van der Waals slabs, revealing that the electron energy loss is dominated by excitation of hyperbolic phonon polaritons, and not of bulk phonons as often reported. Thus, our work is of fundamental importance for interpreting future low-energy loss spectra of van der Waals materials.Here the authors adapt a STEM-EELS system to probe energy loss down to 100 meV, and apply it to map phononic states in hexagonal boron nitride, revealing that the electron loss is dominated by hyperbolic phonon polaritons.

  8. Nano-structural Modification of Amorphous Carbon Thin Films by Low-energy Electron Beam Irradiation

    Institute of Scientific and Technical Information of China (English)

    EijiIwamura; MasanoriYamaguchi

    2004-01-01

    A new approach using a low-energy electron beam radiation system was investigated to synthesize carbon hybrid structures in amorphous carbon thin films. Two types of amorphous carbon films, which were 15at% iron containing film and with column/inter-column structures, were deposited onto Si substrates by a sputtering technique and subsequently exposed to an electron shower of which the energy and dose rate were much smaller compared to an intense electron beam used in a transmission electron microscopy. As a result of the low-energy and low-dose electron irradiation process, graphitic structures formed in amorphous matrix at a relatively low temperature up to 450 K. Hybrid carbon thin films containing onion-like structures in an amorphous carbon matrix were synthesized by dynamic structural modification of iron containing amorphous carbon thin films. It was found that the graphitization progressed more in the electron irradiation than in annealing at 773K, and it was attributed to thermal and catalytic effects which are strongly related to grain growth of metal clusters. On the other hand, a reversal of TEM image contrast was observed in a-C films with column/inter-column structures. It is presumed that preferable graphitization occurred in the inter-column regions induced by electron irradiation.

  9. Nano-structural Modification of Amorphous Carbon Thin Films by Low-energy Electron Beam Irradiation

    Institute of Scientific and Technical Information of China (English)

    Eiji Iwamura; Masanori Yamaguchi

    2004-01-01

    A new approach using a low-energy electron beam radiation system was investigated to synthesize carbon hybrid structures in amorphous carbon thin films. Two types of amorphous carbon films, which were 15at% iron containing film and with column/inter-column structures, were deposited onto Si substrates by a sputtering technique and subsequently exposed to an electron shower of which the energy and dose rate were much smaller compared to an intense electron beam used in a transmission electron microscopy. As a result of the low-energy and low-dose electron irradiation process,graphitic structures formed in amorphous matrix at a relatively low temperature up to 450 K. Hybrid carbon thin films containing onion-like structures in an amorphous carbon matrix were synthesized by dynamic structural modification of iron containing amorphous carbon thin films. It was found that the graphitization progressed more in the electron irradiation than in annealing at 773K, and it was attributed to thermal and catalytic effects which are strongly related to grain growth of metal clusters. On the other hand, a reversal of TEM image contrast was observed in a-C films with column/inter-column structures. It is presumed that preferable graphitization occurred in the inter-column regions induced by electron irradiation.

  10. The Role of Low-Energy Electrons in Astrochemistry: A Tale of Two Molecules

    Science.gov (United States)

    Arumainayagam, Chris; Cambell, Jyoti; Leon Sanche, Michael Boyer, and Petra Swiderek.

    2016-06-01

    In the interstellar medium, UV photolysis of ice mantles encasing dust grains is thought to be the mechanism that drives the synthesis of “complex” molecules. The source of this reaction-initiating UV light is assumed to be local because externally-sourced UV radiation cannot pass through the ice-containing dark, dense molecular clouds. Externally sourced cosmic rays (Emax ~ 1020 eV), in addition to producing UV light within these clouds, also produce large numbers of low-energy (≤ 20 eV) secondary electrons. The goal of our studies is to understand the low-energy electron-induced processes that occur when high-energy cosmic rays interact with interstellar ices. Using electron stimulated desorption (ESD), post-irradiation temperature-programmed desorption (TPD), and infrared reflection absorption spectroscopy (IRAS), we have investigated the radiolysis initiated by electrons in condensed methanol and ammonia at ~ 90 K under ultrahigh vacuum (1×10-9 Torr) conditions. We have identified fifteen low-energy (≤ 20 eV) electron-induced methanol radiolysis products, many of which have been previously identified as being formed by methanol UV photolysis in the interstellar medium. We have also found evidence for the electron-induced formation from ammonia of hydrazine (N2H4), diazene (N2H2), cyclotriazane/triazene (N3H3) and triazane (N3H5). We have investigated the reaction yields’ dependence on film thickness, irradiation time, incident current, electron energy, and metal substrate. These results provide a basis from which we can begin to understand the mechanisms by which methanol and ammonia can form more complex species in cosmic ices. Studies such as ours may ultimately help us better understand the initial stages of the genesis of life.

  11. Correlated electric field and low-energy electron measurements in the low-altitude polar cusp

    Science.gov (United States)

    Kintner, P. M.; Ackerson, K. L.; Gurnett, D. A.; Frank, L. A.

    1978-01-01

    Correlated electric field and low-energy electron measurements are presented for two passes of Hawkeye 1 through the south polar cusp at 2000-km altitude during local morning. In one case the electric field reversal coincides with the boundary of detectable 5.2keV electron intensities and the equatorward boundary of the cusp. In the other case the electric field reversal and the 5.2 keV electron trapping boundary coincide, but the equatorward edge of the cusp as determined from the presence of 180 eV electron intensities is 5 degrees invariant latitude equatorward of the electric field reversal. It is concluded that in the second case, electron intensities associated with the polar cusp populate closed dayside field lines, and hence the corresponding equatorward edge of these electron intensities is not always an indicator of the boundary between closed dayside field lines and polar cap field lines.

  12. Low-Energy Electron Diffraction Determination of the Structure of the Zeta Phase of Oxygen Physisorbed on Graphite

    DEFF Research Database (Denmark)

    Toney, Michael; Fain, S.C.

    1984-01-01

    Low-energy electron diffraction measurements on the ζ phase of diatomic oxygen physisorbed on the basal plane of graphite single crystals are reported for 12......Low-energy electron diffraction measurements on the ζ phase of diatomic oxygen physisorbed on the basal plane of graphite single crystals are reported for 12...

  13. Low-energy run of Fermilab Electron Cooler's beam generation system

    Energy Technology Data Exchange (ETDEWEB)

    Prost, Lionel; Shemyakin, Alexander; /Fermilab; Fedotov, Alexei; Kewisch, Jorg; /Brookhaven

    2010-08-01

    As a part of a feasibility study of using the Fermilab Electron Cooler for a low-energy Relativistic Heavy Ion Collider (RHIC) run at Brookhaven National Laboratory (BNL), the cooler operation at 1.6 MeV electron beam energy was tested in a short beam line configuration. The main result of the study is that the cooler beam generation system is suitable for BNL needs. In a striking difference with running 4.3 MeV beam, no unprovoked beam recirculation interruptions were observed.

  14. Theory of Carbon Nanotube (CNT-Based Electron Field Emitters

    Directory of Open Access Journals (Sweden)

    Alexander V. Eletskii

    2013-07-01

    Full Text Available Theoretical problems arising in connection with development and operation of electron field emitters on the basis of carbon nanotubes are reviewed. The physical aspects of electron field emission that underlie the unique emission properties of carbon nanotubes (CNTs are considered. Physical effects and phenomena affecting the emission characteristics of CNT cathodes are analyzed. Effects given particular attention include: the electric field amplification near a CNT tip with taking into account the shape of the tip, the deviation from the vertical orientation of nanotubes and electrical field-induced alignment of those; electric field screening by neighboring nanotubes; statistical spread of the parameters of the individual CNTs comprising the cathode; the thermal effects resulting in degradation of nanotubes during emission. Simultaneous consideration of the above-listed effects permitted the development of the optimization procedure for CNT array in terms of the maximum reachable emission current density. In accordance with this procedure, the optimum inter-tube distance in the array depends on the region of the external voltage applied. The phenomenon of self-misalignment of nanotubes in an array has been predicted and analyzed in terms of the recent experiments performed. A mechanism of degradation of CNT-based electron field emitters has been analyzed consisting of the bombardment of the emitters by ions formed as a result of electron impact ionization of the residual gas molecules.

  15. Theory of Carbon Nanotube (CNT)-Based Electron Field Emitters.

    Science.gov (United States)

    Bocharov, Grigory S; Eletskii, Alexander V

    2013-07-17

    Theoretical problems arising in connection with development and operation of electron field emitters on the basis of carbon nanotubes are reviewed. The physical aspects of electron field emission that underlie the unique emission properties of carbon nanotubes (CNTs) are considered. Physical effects and phenomena affecting the emission characteristics of CNT cathodes are analyzed. Effects given particular attention include: the electric field amplification near a CNT tip with taking into account the shape of the tip, the deviation from the vertical orientation of nanotubes and electrical field-induced alignment of those; electric field screening by neighboring nanotubes; statistical spread of the parameters of the individual CNTs comprising the cathode; the thermal effects resulting in degradation of nanotubes during emission. Simultaneous consideration of the above-listed effects permitted the development of the optimization procedure for CNT array in terms of the maximum reachable emission current density. In accordance with this procedure, the optimum inter-tube distance in the array depends on the region of the external voltage applied. The phenomenon of self-misalignment of nanotubes in an array has been predicted and analyzed in terms of the recent experiments performed. A mechanism of degradation of CNT-based electron field emitters has been analyzed consisting of the bombardment of the emitters by ions formed as a result of electron impact ionization of the residual gas molecules.

  16. Theory of Carbon Nanotube (CNT)-Based Electron Field Emitters

    Science.gov (United States)

    Bocharov, Grigory S.; Eletskii, Alexander V.

    2013-01-01

    Theoretical problems arising in connection with development and operation of electron field emitters on the basis of carbon nanotubes are reviewed. The physical aspects of electron field emission that underlie the unique emission properties of carbon nanotubes (CNTs) are considered. Physical effects and phenomena affecting the emission characteristics of CNT cathodes are analyzed. Effects given particular attention include: the electric field amplification near a CNT tip with taking into account the shape of the tip, the deviation from the vertical orientation of nanotubes and electrical field-induced alignment of those; electric field screening by neighboring nanotubes; statistical spread of the parameters of the individual CNTs comprising the cathode; the thermal effects resulting in degradation of nanotubes during emission. Simultaneous consideration of the above-listed effects permitted the development of the optimization procedure for CNT array in terms of the maximum reachable emission current density. In accordance with this procedure, the optimum inter-tube distance in the array depends on the region of the external voltage applied. The phenomenon of self-misalignment of nanotubes in an array has been predicted and analyzed in terms of the recent experiments performed. A mechanism of degradation of CNT-based electron field emitters has been analyzed consisting of the bombardment of the emitters by ions formed as a result of electron impact ionization of the residual gas molecules. PMID:28348342

  17. Low-Energy Plasma Focus Device as an Electron Beam Source

    Science.gov (United States)

    Seong Ling, Yap; Naresh Kumar, Nitturi; Lian Kuang, Lim; Chiow San, Wong

    2014-01-01

    A low-energy plasma focus device was used as an electron beam source. A technique was developed to simultaneously measure the electron beam intensity and energy. The system was operated in Argon filling at an optimum pressure of 1.7 mbar. A Faraday cup was used together with an array of filtered PIN diodes. The beam-target X-rays were registered through X-ray spectrometry. Copper and lead line radiations were registered upon usage as targets. The maximum electron beam charge and density were estimated to be 0.31 μC and 13.5 × 1016/m3, respectively. The average energy of the electron beam was 500 keV. The high flux of the electron beam can be potentially applicable in material sciences. PMID:25544952

  18. Double-electron capture by highly-ionized atoms isolated at very low energy

    Science.gov (United States)

    Fogwell Hoogerheide, Shannon; Dreiling, Joan M.; Sahiner, Arda; Tan, Joseph N.

    2016-05-01

    Charge exchange with background gases, also known as electron capture processes, is important in the study of comets, controlled fusion energy, anti-matter atoms, and proposed one-electron ions in Rydberg states. However, there are few experiments in the very low energy regime that could be useful for further theoretical development. At NIST, highly-charged ions extracted from an electron-beam ion trap can be isolated with energy state. Analysis using a system of rate equations yields information about the ion cloud expansion and single-electron capture rates. A substantial amount of double-electron capture is also observed. We present the relative rates and discuss the error budget. SFH and JMD were funded by National Research Council Research Associateship Awards during some of this work.

  19. Low-Energy Plasma Focus Device as an Electron Beam Source

    Directory of Open Access Journals (Sweden)

    Muhammad Zubair Khan

    2014-01-01

    Full Text Available A low-energy plasma focus device was used as an electron beam source. A technique was developed to simultaneously measure the electron beam intensity and energy. The system was operated in Argon filling at an optimum pressure of 1.7 mbar. A Faraday cup was used together with an array of filtered PIN diodes. The beam-target X-rays were registered through X-ray spectrometry. Copper and lead line radiations were registered upon usage as targets. The maximum electron beam charge and density were estimated to be 0.31 μC and 13.5×1016/m3, respectively. The average energy of the electron beam was 500 keV. The high flux of the electron beam can be potentially applicable in material sciences.

  20. Emission of Low-Energy Photons by Electrons at Electron-Positron and Electron-Ion Colliders with Dense Bunches

    CERN Document Server

    Jentschura, U D; Serbo, V G; 10.1103/PhysRevSTAB.12.011003

    2009-01-01

    Usually, the emission of low-energy photons in electron-positron (or electron-ion) bunch collisions is calculated with the same approach as for synchrotron radiation (beamstrahlung). However, for soft photons (E_gamma < E_c where E_c is a critical photon energy), when the coherence length of the radiation becomes comparable to the bunch length, the beamstrahlung approximation becomes invalid. In this paper, we present results of our calculation for this region based on approximation of classical currents. We consider several colliders with dense bunches. The number of low-energy photons dN_gamma emitted by N_e electrons per bunch crossing in the energy interval dE_gamma is dN_gamma = alpha g N_e dE_gamma/E_gamma, where alpha is the fine-structure constant, and the function g, which depends on the bunch parameters, typically is of order unity for modern colliders. In particular, for the ILC, we find that E_c = 83 keV and g=5.5 at a vanishing beam axis displacement, and g=0.88, E_c=0.24 keV for KEKB. We also...

  1. Measurements of the Electron Cloud Density in the PEP-II Low Energy Ring

    CERN Document Server

    Byrd, J; Sonnad, K; Caspers, Friedhelm; Kroyer, T; Krasnykh, A; Pivi, M

    2009-01-01

    Clouds of low energy electrons in the vacuum beam pipes of accelerators of positively charged particle beams present a serious limitation for operation of these machines at high currents. Because of the size of these accelerators, it is difficult to probe the low energy electron clouds over substantial lengths of the beam pipe. We have developed a novel technique to directly measure the electron cloud density via the phase shift induced in a TE wave that is independently excited and transmitted over a section of the accelerator. We infer the absolute phase shift with relatively high accuracy from the phase modulation of the transmission due to the modulation of the electron cloud density from a gap in the positively charged beam. We have used this technique for the first time to measure the average electron cloud density over a 50 m straight section in the positron ring of the PEP-II collider at the Stanford Linear Accelerator Center. We have also measured the variation of the density by using low field solen...

  2. Low-energy electron holographic imaging of individual tobacco mosaic virions

    Energy Technology Data Exchange (ETDEWEB)

    Longchamp, Jean-Nicolas, E-mail: longchamp@physik.uzh.ch; Latychevskaia, Tatiana; Escher, Conrad; Fink, Hans-Werner [Physics Department, University of Zurich, Winterthurerstrasse 190, 8057 Zurich (Switzerland)

    2015-09-28

    Modern structural biology relies on Nuclear Magnetic Resonance (NMR), X-ray crystallography, and cryo-electron microscopy for gaining information on biomolecules at nanometer, sub-nanometer, or atomic resolution. All these methods, however, require averaging over a vast ensemble of entities, and hence knowledge on the conformational landscape of an individual particle is lost. Unfortunately, there are now strong indications that even X-ray free electron lasers will not be able to image individual molecules but will require nanocrystal samples. Here, we show that non-destructive structural biology of single particles has now become possible by means of low-energy electron holography. As an example, individual tobacco mosaic virions deposited on ultraclean freestanding graphene are imaged at 1 nm resolution revealing structural details arising from the helical arrangement of the outer protein shell of the virus. Since low-energy electron holography is a lens-less technique and since electrons with a deBroglie wavelength of approximately 1 Å do not impose radiation damage to biomolecules, the method has the potential for Angstrom resolution imaging of single biomolecules.

  3. Low Emittance Guns for the ILC Polarized Electron Beam

    Science.gov (United States)

    Clendenin, J. E.; Brachmann, A.; Ioakeimidi, K.; Kirby, R. E.; Maruyama, T.; Miller, R. H.; Wang, J. W.; Zhou, F.

    2007-06-01

    Polarized electron beams generated by DC guns are routinely available at several accelerators including JLAB, Mainz and SLAC. These guns operate with a cathode bias on the order of -100 kV. To minimize space charge effects, relatively long bunches are generated at the gun and then compressed longitudinally external to the gun just before and during initial acceleration. For linear colliders, this compression is accomplished using a combination of rf bunchers. For the basic design of the International Linear Collider (ILC), a 120 kV DC photocathode gun is used to produce a series of nanosecond bunches that are each compressed by two sub-harmonic bunchers (SHBs) followed by an L-band buncher and capture section. The longitudinal bunching process results in a significantly higher emittance than produced by the gun alone. While high-energy experiments using polarized beams are not generally sensitive to the source emittance, there are several benefits to a lower source emittance including a simpler more efficient injector system and a lower radiation load during transport especially at bends as at the damping ring. For the ILC, the SHBs could be eliminated if the voltage of the gun is raised sufficiently. Simulations using the General Particle Tracer (GPT) package indicate that a cathode bias voltage of ⩾200 kV should allow both SHBs to be operated at 433 or even 650 MHz, while ⩾500 kV would be required to eliminate the SHBs altogether. Simulations can be used to determine the minimum emittance possible if the injector is designed for a given increased voltage. A possible alternative to the DC gun is an rf gun. Emittance compensation, routinely used with rf guns, is discussed for higher-voltage DC guns.

  4. Development of the techniques for food processing with low-energy electron beam

    Energy Technology Data Exchange (ETDEWEB)

    Todoroki, Setsuko; Hayashi, Toru [National Food Research Inst., Tsukuba, Ibaraki (Japan)

    1999-02-01

    This study aimed to construct a new electron beam irradiation apparatus which allows to perform homogeneous irradiation up to a certain depth of a spherical or granular material through rotating it. And the sterilizing effects of this apparatus on various kinds of spices such as black and white peppers (grains), turmeric (root), coriander (seed), basil (leaves) were investigated to compare with the effects of {gamma}-ray irradiation. Electron beam irradiation was made changing the energy form 200 keV for 15 min to 500 keV for 5 min and a dose-depth curve was drawn for each electron energy. Indicator balls were used to examine the radiation effects. It became possible to make homogeneous irradiation onto a spherical surface of food by using the rotary system of the apparatus. It was demonstrated that satisfactory sterilizing effects as much as those of {gamma}-ray were obtainable by superficial treatments with low-energy electron. (M.N.)

  5. Low Energy Scanned Electron-Beam Dose Distribution in Thin Layers

    DEFF Research Database (Denmark)

    McLaughlin, W. L.; Hjortenberg, P. E.; Pedersen, Walther Batsberg

    1975-01-01

    Thin radiochromic dye film dosimeters, calibrated by means of calorimetry, make possible the determination of absorbed-dose distributions due to low-energy scanned electron beam penetrations in moderately thin coatings and laminar media. For electrons of a few hundred keV, calibrated dosimeters...... of about 30–60 μm thickness may be used in stacks or interleaved between layers of materials of interest and supply a sufficient number of experimental data points throughout the depth of penetration of electrons to provide a depth-dose curve. Depth doses may be resolved in various polymer layers...... on different backings (wood, aluminum, and iron) for scanned electron beams (Emax = 400 keV) having a broad energy spectrum and diffuse incidence, such as those used in radiation curing of coatings, textiles, plastics, etc. Theoretical calculations of such distributions of energy depositions are relatively...

  6. eV-TEM: Transmission electron microscopy in a low energy cathode lens instrument

    Energy Technology Data Exchange (ETDEWEB)

    Geelen, Daniël, E-mail: geelen@physics.leidenuniv.nl [Huygens-Kamerlingh Onnes Laboratory, Leiden Institute of Physics, Leiden University, P.O. Box 9504, 2300 RA Leiden (Netherlands); Thete, Aniket [Huygens-Kamerlingh Onnes Laboratory, Leiden Institute of Physics, Leiden University, P.O. Box 9504, 2300 RA Leiden (Netherlands); Schaff, Oliver; Kaiser, Alexander [SPECS GmbH, Voltastrasse 5, D-13355 Berlin (Germany); Molen, Sense Jan van der [Huygens-Kamerlingh Onnes Laboratory, Leiden Institute of Physics, Leiden University, P.O. Box 9504, 2300 RA Leiden (Netherlands); Tromp, Rudolf [IBM T.J. Watson Research Center, 1101 Kitchawan Road, P.O. Box 218, Yorktown Heights, NY 10598 (United States)

    2015-12-15

    We are developing a transmission electron microscope that operates at extremely low electron energies, 0–40 eV. We call this technique eV-TEM. Its feasibility is based on the fact that at very low electron energies the number of energy loss pathways decreases. Hence, the electron inelastic mean free path increases dramatically. eV-TEM will enable us to study elastic and inelastic interactions of electrons with thin samples. With the recent development of aberration correction in cathode lens instruments, a spatial resolution of a few nm appears within range, even for these very low electron energies. Such resolution will be highly relevant to study biological samples such as proteins and cell membranes. The low electron energies minimize adverse effects due to radiation damage. - Highlights: • We present a new way of performing low energy transmission electron microscopy in an aberration corrected LEEM/PEEM instrument. • We show a proof of principle where we measure transmitted electrons through a suspended graphene monolayer with a preliminary setup. • We present an improved setup design that provides better control of the incident electron beam.

  7. Low-energy elastic electron scattering form chloroethane, C2H5Cl

    Science.gov (United States)

    Sakaamini, A.; Navarro, C.; Cross, J.; Hargreaves, L. R.; Khakoo, M. A.; Fedus, Kamil; Winstead, C.; McKoy, V.

    2015-10-01

    We report theoretical as well as (normalized) experimental differential and integral cross sections for vibrationally elastic scattering of low-energy electrons from chloroethane, C2H5Cl, also known as ethyl chloride. The theoretical cross sections were computed using the Schwinger multichannel variational method in the single-channel approximation, with polarization effects included via virtual excitations. Cross section measurements were made at incident energies ranging from 1 to 30 eV and at scattering angles from {10}\\circ to {125}\\circ . We compare our data to previous results for C2H5Cl and for the related molecule chloromethane.

  8. Low-energy elastic electron scattering from chloromethane, CH3Cl

    Science.gov (United States)

    Navarro, C.; Sakaamini, A.; Cross, J.; Hargreaves, L. R.; Khakoo, M. A.; Fedus, Kamil; Winstead, C.; McKoy, V.

    2015-10-01

    We report theoretical as well as (normalized) experimental differential and integral cross sections for vibrationally elastic scattering of low-energy electrons from chloromethane, CH3Cl, also known as methyl chloride. The theoretical cross sections were computed using the Schwinger multichannel variational method in the single-channel approximation, with polarization effects included via virtual excitations. Cross section measurements were made at incident energies ranging from 0.5 to 100 eV and at scattering angles from {5}\\circ to {125}\\circ . We compare our data to earlier previous results for this molecule.

  9. Vibrational excitation differential cross sections of low-energy electron scattering from N2 molecule

    Institute of Scientific and Technical Information of China (English)

    孙卫国; Michael; A.Morrison

    1999-01-01

    The vibrational excitation differential cross sections (DCS) of low-energy electron-N2 scattering are studied using vibrational close-coupling (VCC) scattering method and quantum scattering potentials which include static, exchange, and polarization contributions based on ab initio calculations. By including the contributions of 11 partial waves (up to l=21), 15 vibrational states, and 16 molecular symmetries (up to Λ=7), the converged vibrational excitation (0→2, 0→3, 0→4) DCSs, the scattering resonance, and the vibrational multi-peak structure agree well with experimental results.

  10. Modified Bethe formula for low-energy electron stopping power without fitting parameters.

    Science.gov (United States)

    Nguyen-Truong, Hieu T

    2015-02-01

    We propose a modified Bethe formula for low-energy electron stopping power without fitting parameters for a wide range of elements and compounds. This formula maintains the generality of the Bethe formula and gives reasonable agreement in comparing the predicted stopping powers for 15 elements and 6 compounds with the experimental data and those calculated within dielectric theory including the exchange effect. Use of the stopping power obtained from this formula for hydrogen silsesquioxane in Monte Carlo simulation gives the energy deposition distribution in consistent with the experimental data.

  11. A dressing of zero-range potentials and electron-molecule scattering problem at low energies

    CERN Document Server

    Leble, S B

    2002-01-01

    A dressing of a nonspherical potential, which includes $n$ zero range potentials, is considered. The dressing technique is used to improve ZRP model. Concepts of the partial waves and partial phases for non-spherical potential are used in order to perform Darboux transformation. The problem of scattering on the regular $\\hbox{X}_n$ and $\\hbox{YX}_n$ structures is studied. The possibilities of dressed ZRP are illustrated by model calculation of the low-energy electron-Silane ($\\hbox{SiH}_4$) scattering. The results are discussed. Key words: multiple scattering, silane, zero range potential.

  12. Low-energy electron reflectivity from graphene: First-principles computations and approximate models

    Energy Technology Data Exchange (ETDEWEB)

    Feenstra, R.M., E-mail: feenstra@cmu.edu [Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213 (United States); Widom, M. [Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213 (United States)

    2013-07-15

    A computational method is developed whereby the reflectivity of low-energy electrons from a surface can be obtained from a first-principles solution of the electronic structure of the system. The method is applied to multilayer graphene. Two bands of reflectivity minima are found, one at 0–8 eV and the other at 14–22 eV above the vacuum level. For a free-standing slab with n layers of graphene, each band contains n−1 zeroes in the reflectivity. Two additional image-potential type states form at the ends of the graphene slab, with energies just below the vacuum level, hence producing a total of 2n states. A tight-binding model is developed, with basis functions localized in the spaces between the graphene planes (and at the ends of the slab). The spectrum of states produced by the tight-binding model is found to be in good agreement with the zeros of reflectivity (i.e. transmission resonances) of the first-principles results. - Highlights: ► Developed method for simulation of low-energy electron reflectivity spectra. ► Reflectivity spectra of graphene are computed by a first-principles method. ► Comparison is made between results from first-principles and from a tight-binding model.

  13. Electronic stopping power of hydrogen in KCl at the stopping maximum and at very low energies

    Science.gov (United States)

    Primetzhofer, D.; Markin, S. N.; Bauer, P.

    2011-10-01

    The electronic energy loss of hydrogen ions in KCl was investigated in a wide energy range. Thin films of KCl were evaporated on an Au/Si substrate. Rutherford Backscattering Spectrometry (RBS) was performed with protons and deuterons at energies from 30 to 400 keV/nucleon. At lower energies experiments were performed by Time-Of-Flight Low energy ion scattering (TOF-LEIS) again with proton and deuteron projectiles. Experimental results are compared to calculated/tabulated values for the electronic energy loss. Whereas at energies beyond the stopping maximum very good agreement is found, at lower ion energies discrepancies between experiment and calculations increase. At very low ion velocities the extrapolated stopping cross section ɛ predicts vanishing electronic energy loss at energies below 100 eV/nucleon.

  14. Electron-positron pair creation in low-energy collisions of heavy bare nuclei

    CERN Document Server

    Maltsev, I A; Tupitsyn, I I; Bondarev, A I; Kozhedub, Y S; Plunien, G; Stoehlker, Th

    2014-01-01

    A new method for calculations of electron-positron pair-creation probabilities in low-energy heavy-ion collisions is developed. The approach is based on the propagation of all one-electron states via the numerical solving of the time-dependent Dirac equation in the monopole approximation. The electron wave functions are represented as finite sums of basis functions constructed from B-splines using the dual-kinetic-balance technique. The calculations of the created particle numbers and the positron energy spectra are performed for the collisions of bare nuclei at the energies near the Coulomb barrier with the Rutherford trajectory and for different values of the nuclear charge and the impact parameter. To examine the role of the spontaneous pair creation the collisions with a modified velocity and with a time delay are also considered. The obtained results are compared with the previous calculations and the possibility of observation of the spontaneous pair creation is discussed.

  15. Detector and Electronic Developments for Low Energy Multi Particle Break-up Studies.

    Science.gov (United States)

    Tengblad, Olof

    2007-11-01

    The study of excited states of unbound light nuclei includes the simultaneous detection of several charge particles emitted with very low energy. This puts several constrains on the detection system to be used. For the detectors, high segmentation is needed to be able to detect several coincident particles without an exponential drop in efficiency. The high segmentation of the detectors leads to experiments with an increased amount of electronic channels. For very dedicated experiment integrated electronic chips can be prepared, but in many cases where the detector set-up are frequently being changed, one still have to rely on more traditional analogue electronic circuits. News in the field of charge particle detection will be discussed.

  16. Shaping the electron beams with submicrosecond pulse duration in sources and electron accelerators with plasma emitters

    CERN Document Server

    Gushenets, V I

    2001-01-01

    One studies the techniques in use to shape submicrosecond electron beams and the physical processes associated with extraction of electrons from plasma in plasma emitters. Plasma emitter base sources and accelerators enable to generate pulse beams with currents varying from tens of amperes up to 10 sup 3 A, with current densities up to several amperes per a square centimeter, with pulse duration constituting hundreds of nanoseconds and with high frequencies of repetition

  17. Study of energy delivery and mean free path of low energy electrons in EUV resists

    Science.gov (United States)

    Bhattarai, Suchit; Neureuther, Andrew R.; Naulleau, Patrick P.

    2016-03-01

    The relative importance of secondary electrons in delivering energy in photoresist films was assessed by performing large area exposures and by quantifying the inelastic mean free path of electrons in a leading chemically amplified positive tone EUV resist. A low energy electron microscope was used to directly pattern large (~15μm x 20μm) features with 15-80 eV electrons followed by analyzing the resulting dissolution rate contrast curve data. In the 40 to 80 eV regime the energy delivery was found to scale roughly proportionally with electron energy. In 15 to 30 eV regime however, this energy scaling did not explain the resist thickness loss data. The dose required to lower the resist thickness down to 20 nm was found to be 2-5X larger for 15 eV electrons than for 20, 25 and 30 eV electrons. Using scattering models from the literature including phonon scattering and optical data deduced electron energy loss spectroscopy and optical reflectometry, the inelastic mean free path values at energies between 10 eV and 92 eV range between about 2.8 and 0.6 nm respectively.

  18. Emittance growth induced by electron cloud in proton storage rings

    CERN Document Server

    Benedetto, Elena; Coppa, G

    2006-01-01

    In proton and positron storage rings with many closely spaced bunches, a large number of electrons can accumulate in the beam pipe due to various mechanisms (photoemission, residual gas ionization, beam-induced multipacting). The so-formed electron cloud interacts with the positively charged bunches, giving rise to instabilities, emittance growth and losses. This phenomenon has been observed in several existing machines such as the CERN Super Proton Synchrotron (SPS), whose operation has been constrained by the electron-cloud problem, and it is a concern for the Large Hadron Collider (LHC), under construction at CERN. The interaction between the beam and the electron cloud has features which cannot be fully taken into account by the conventional and known theories from accelerators and plasma physics. Computer simulations are indispensable for a proper prediction and understanding of the instability dynamics. The main feature which renders the beam-cloud interactions so peculiar is that the the electron cloud...

  19. Will climate change increase ozone depletion from low-energy-electron precipitation?

    Directory of Open Access Journals (Sweden)

    A. J. G. Baumgaertner

    2010-04-01

    Full Text Available We investigate the effects of a strengthened Brewer-Dobson circulation on the transport of nitric oxide (NO produced by energetic particle precipitation. During periods of high geomagnetic activity, low-energy-electron precipitation is responsible for winter time ozone loss in the polar middle atmosphere between 1 and 6 hPa. However, as climate change is expected to increase the strength of the Brewer-Dobson circulation, the enhancements of NOx concentrations are expected to be transported to lower altitudes in extra-tropical regions, becoming even more significant in the ozone budget. We use simulations with the chemistry climate model system ECHAM5/MESSy to compare present day effects of low-energy-electron precipitation with expected effects in a climate change scenario for the year 2100. In years of strong geomagnetic activity, similar to that observed in 2003, an additional polar ozone loss of up to 0.5 μmol/mol at 5 hPa is found. However, this would be approximately compensated by an ozone enhancement originating from a stronger poleward transport of ozone from lower latitudes caused by a strengthened Brewer-Dobson circulation, as well as by slower photochemical ozone loss reactions in a stratosphere cooled by risen greenhouse gas concentrations.

  20. Simulations of slow positron production using a low energy electron accelerator

    CERN Document Server

    O'Rourke, B E; Kinomura, A; Kuroda, R; Minehara, E; Ohdaira, T; Oshima, N; Suzuki, R

    2011-01-01

    Monte Carlo simulations of slow positron production via energetic electron interaction with a solid target have been performed. The aim of the simulations was to determine the expected slow positron beam intensity from a low energy, high current electron accelerator. By simulating (a) the fast positron production from a tantalum electron-positron converter and (b) the positron depth deposition profile in a tungsten moderator, the slow positron production probability per incident electron was estimated. Normalizing the calculated result to the measured slow positron yield at the present AIST LINAC the expected slow positron yield as a function of energy was determined. For an electron beam energy of 5 MeV (10 MeV) and current 240 $\\mu$A (30 $\\mu$A) production of a slow positron beam of intensity 5 $\\times$ 10$^{6}$ s$^{-1}$ is predicted. The simulation also calculates the average energy deposited in the converter per electron, allowing an estimate of the beam heating at a given electron energy and current. For...

  1. Field Emitter Arrays for a Free Electron Laser Application

    CERN Document Server

    Shing-Bruce-Li, Kevin; Ganter, Romain; Gobrecht, Jens; Raguin, Jean Yves; Rivkin, Leonid; Wrulich, Albin F

    2004-01-01

    The development of a new electron gun with the lowest possible emittance would help reducing the total length and cost of a free electron laser. Field emitter arrays (FEAs) are an attractive technology for electron sources of ultra high brightness. Indeed, several thousands of microscopic tips can be deposited on a 1 mm diameter area. Electrons are then extracted by applying voltage to a first grid layer close to the tip apexes, the so called gate layer, and focused by a second grid layer one micrometer above the tips. The typical aperture diameter of the gate and the focusing layer is in the range of one micrometer. One challenge for such cathodes is to produce peak currents in the ampere range since the usual applications of FEAs require less than milliampere. Encouraging peak current performances have been obtained by applying voltage pulses at low frequency between gate and tips. In this paper we report on different tip materials available on the market: diamond FEAs from Extreme Devices Inc., ZrC single ...

  2. Emittance Measurements from a Laser Driven Electron Injector

    CERN Document Server

    Reis, D

    2003-01-01

    The Gun Test Facility (GTF) at the Stanford Linear Accelerator Center was constructed to develop an appropriate electron beam suitable for driving a short wavelength free electron laser (FEL) such as the proposed Linac Coherent Light Source (LCLS). For operation at a wavelength of 1.5 (angstrom), the LCLS requires an electron injector that can produce an electron beam with approximately 1 pi mm-mrad normalized rms emittance with at least 1 nC of charge in a 10 ps or shorter bunch. The GTF consists of a photocathode rf gun, emittance-compensation solenoid, 3 m linear accelerator (linac), drive laser, and diagnostics to measure the beam. The rf gun is a symmetrized 1.6 cell, s-band high gradient, room temperature, photocathode structure. Simulations show that this gun when driven by a temporally and spatially shaped drive laser, appropriately focused with the solenoid, and further accelerated in linac can produce a beam that meets the LCLS requirements. This thesis describes the initial characterization of the ...

  3. SURVIVAL DEPTH OF ORGANICS IN ICES UNDER LOW-ENERGY ELECTRON RADIATION ({<=}2 keV)

    Energy Technology Data Exchange (ETDEWEB)

    Barnett, Irene Li; Lignell, Antti; Gudipati, Murthy S., E-mail: gudipati@jpl.nasa.gov [Jet Propulsion Laboratory, California Institute of Technology, Mail Stop 183-301, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States)

    2012-03-01

    Icy surfaces in our solar system are continually modified and sputtered with electrons, ions, and photons from solar wind, cosmic rays, and local magnetospheres in the cases of Jovian and Saturnian satellites. In addition to their prevalence, electrons specifically are expected to be a principal radiolytic agent on these satellites. Among energetic particles (electrons and ions), electrons penetrate by far the deepest into the ice and could cause damage to organic material of possible prebiotic and even biological importance. To determine if organic matter could survive and be detected through remote sensing or in situ explorations on these surfaces, such as water ice-rich Europa, it is important to obtain accurate data quantifying electron-induced chemistry and damage depths of organics at varying incident electron energies. Experiments reported here address the quantification issue at lower electron energies (100 eV-2 keV) through rigorous laboratory data analysis obtained using a novel methodology. A polycyclic aromatic hydrocarbon molecule, pyrene, embedded in amorphous water ice films of controlled thicknesses served as an organic probe. UV-VIS spectroscopic measurements enabled quantitative assessment of organic matter survival depths in water ice. Eight ices of various thicknesses were studied to determine damage depths more accurately. The electron damage depths were found to be linear, approximately 110 nm keV{sup -1}, in the tested range which is noticeably higher than predictions by Monte Carlo simulations by up to 100%. We conclude that computational simulations underestimate electron damage depths in the energy region {<=}2 keV. If this trend holds at higher electron energies as well, present models utilizing radiation-induced organic chemistry in icy solar system bodies need to be revisited. For interstellar ices of a few micron thicknesses, we conclude that low-energy electrons generated through photoionization processes in the interstellar medium

  4. Low-energy electron impact cross-sections and rate constants of $NH_2$

    Indian Academy of Sciences (India)

    ANAND BHARADVAJA; SAVINDER KAUR; K L BALUJA

    2017-08-01

    This systematic study reports various electron impact cross-sections, rate constants and transport properties of $NH_2$ radical in the low-energy limit. The collision study is based on $R$-matrix formalism and involves the use of various scattering models employing different active spaces. Both electron excited inelasticcross-sections and resonances are found influenced by correlation and polarization effects. The non-relativistic molecular bremsstrahlung radiation cross-section for soft photons, binary encounter Bethe model-based ionization cross-sections and a few molecular properties of the target radical are also reported. The present calculations are found to be in agreement with the available results. This theoretical study provides a pathway to understand collision dynamics and generates data required in various fields of applied physics.

  5. Observation of MWCNTs with low-energy electron point source microscope

    Institute of Scientific and Technical Information of China (English)

    Yu Jie; Bai Xin; Zhang Zhao-Xiang; Zhang Geng-Min; Guo Deng-Zhu; Xue Zeng-Quan

    2006-01-01

    The low-energy electron point source (LEEPS) microscope, which creates enlarged projection images with lowenergy field emission electron beams, can be used to observe the projection image of nano-scale samples and to characterize the coherence of the field emission beam. In this paper we report the design and test operation performance of a home-made LEEPS microscope. Multi-walled carbon nanotubes (MWCNTs) synthesized by the CVD method were observed by LEEPS microscope using a conventional tungsten tip, and projection images with the magnification of up to 104 was obtained. The resolution of the acquired images is ~10 nm. A higher resolution and a larger magnification can be expected when the AC magnetic field inside the equipment is shielded and the vibration of the instrument reduced.

  6. Atomic structure of "multilayer silicene" grown on Ag(111): Dynamical low energy electron diffraction analysis

    Science.gov (United States)

    Kawahara, Kazuaki; Shirasawa, Tetsuroh; Lin, Chun-Liang; Nagao, Ryo; Tsukahara, Noriyuki; Takahashi, Toshio; Arafune, Ryuichi; Kawai, Maki; Takagi, Noriaki

    2016-09-01

    We have investigated the atomic structure of the "multilayer silicene" grown on the Ag(111) single crystal surface by using low energy electron diffraction (LEED) and scanning tunneling microscopy (STM). We measured the intensity of the LEED spot as a function of the incident electron energy (I-V curve) and analyzed the I-V curve using a dynamical LEED theory. We have found that the Si(111)(√{ 3} ×√{ 3})-Ag model well reproduces the I-V curve whereas the models consisting of the honeycomb structure of Si do not. The bias dependence of the STM image of multilayer silicene agrees with that of the Si(111)(√{ 3} ×√{ 3})-Ag reconstructed surface. Consequently, we have concluded that the multilayer silicene grown on Ag(111) is identical to the Si(111)(√{ 3} ×√{ 3})-Ag reconstructed structure.

  7. Electrical and optoelectrical modification of cadmium sulfide nanobelts by low-energy electron beam irradiation

    Science.gov (United States)

    Zhang, Lijie; Liu, Manman; Zhao, Mei; Dong, Youqing; Zou, Chao; Yang, Keqin; Yang, Yun; Huang, Shaoming; Zhu, Da-Ming

    2016-09-01

    In this report, we describe a method for modifying electrical and optoelectrical properties of CdS nanobelts using low-energy (lower than 10 keV) e-beam irradiation in a scanning electron microscope. The electrical conductivity of the nanobelts was dramatically improved via the irradiation of e-beams. The modified conductivity of the nanobelts depends on the energy of the e-beam; it exhibits a larger photocurrent and higher external quantum efficiency but slower time-response than that before the modification. A possible mechanism about the modification is the increase of electron accumulation (injected electrons) in the nanobelts due to e-beam irradiation. In addition, the optoelectrical modification could be caused by the trapped electrons in the nanobelts and the decrease of contact resistance between the nanobelts and metal electrodes induced by e-beam irradiation. The results of this work are significant for the in situ study of semiconductor nanostructures in the electron microscope. Besides, the method of electrical and optoelectrical modification presented here has potential application in electronics and optoelectronics.

  8. Low-energy electron attachment and detachment in vibrationally excited oxygen

    Science.gov (United States)

    Aleksandrov, N. L.; Anokhin, E. M.

    2009-11-01

    Three-body electron attachment to O2 molecules and electron detachment from O_{2}^{-} ions have been theoretically studied in vibrationally excited oxygen and O2-containing mixtures. Assuming that electron attachment and detachment proceed via the formation of vibrationally excited temporary O_{2}^{-} ions, the rates of these processes were determined on the basis of the statistical approach for the vibrational transfer and relaxation in collisions between O_{2}^{-} ions and O2 molecules. The calculated attachment and detachment rate constants turned out to agree well with available measurements in unexcited oxygen. This method was extended to calculate attachment and detachment rates in vibrationally excited oxygen. It was shown that the effect of vibrational excitation on electron detachment is profound, whereas attachment of low-energy electrons to vibrationally excited O2 is inefficient. The calculated vibrational distribution of stable O_{2}^{-} ions turned out to be non-equilibrium in an excited gas and the effective vibrational temperature of the ions was much lower than the vibrational temperature of molecules. An analytical method was suggested to determine this distribution and the effective vibrational temperature. The calculated rate constants were used to simulate the formation and decay of an electron-beam-generated plasma in N2 : O2 mixtures at elevated vibrational temperatures. The calculations showed that vibrational excitation of molecules leads to orders of magnitude increase in the plasma density and in the plasma lifetime, in agreement with available observations.

  9. The low-energy electron cooler for the Cryogenic Storage Ring

    Energy Technology Data Exchange (ETDEWEB)

    Vogel, Stephen; Blaum, Klaus; Krantz, Claude; Wolf, Andreas [Max-Planck-Institut fuer Kernphysik, 69117 Heidelberg (Germany)

    2014-07-01

    The Cryogenic Storage Ring (CSR) at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany, is being commissioned. CSR will be an ideal tool for preparing and studying cold atomic and molecular ions using ion beams of 20-300 keV kinetic energy (per ion charge unit). As a first important upgrade CSR will be equipped with an electron cooler. Latter is designed for cooling beams with a charge-to-mass ratio q/m of 1 to 1/160 e/aμ. This corresponds to an electron beam energy range of 1 to 163 eV. The beam will be produced by a cryogenic photocathode and electron temperatures in the co-moving frame reach down to 10 K. The cooler can also be used as an electron target by detuning the electrons' kinetic energy. This allows precision experiments on low-energy collisions between cold electrons and stored atomic and molecular ions using counting and imaging detectors. The design and the status of the setup are presented.

  10. Development of maskless electron-beam lithography using nc-Si electron-emitter array

    Science.gov (United States)

    Kojima, A.; Ikegami, N.; Yoshida, T.; Miyaguchi, H.; Muroyama, M.; Nishino, H.; Yoshida, S.; Sugata, M.; Cakir, S.; Ohyi, H.; Koshida, N.; Esashi, M.

    2013-03-01

    This study demonstrated our prototyped Micro Electro Mechanical System (MEMS) electron emitter which is a nc-Si (nanocrystalline silicon) ballistic electron emitter array integrated with an active-matrix driving LSI for high-speed Massively Parallel Electron Beam Direct Writing (MPEBDW) system. The MPEBDW system consists of the multi-column, and each column provides multi-beam. Each column consists of emitter array, a MEMS condenser lens array, an MEMS anode array, a stigmator, three-stage deflectors to align and to scan the multi beams, and a reduction lens as an objective lens. The emitter array generates 100x100 electron beams with binary patterns. The pattern exposed on a target is stored in one of the duplicate memories in the active matrix LSI. After the emission, each electron beam is condensed into narrow beam in parallel to the axis of electron optics of the system with the condenser lens array. The electrons of the beams are accelerated and pass through the anode array. The stigmator and deflectors make fine adjustments to the position of the beams. The reduction lens in the final stage focuses all parallel beams on the surface of the target wafer. The lens reduces the electron image to 1%-10% in size. Electron source in this system is nc-Si ballistic surface electron emitter. The characteristics of the emitter of 1:1 projection of e-beam have been demonstrated in our previous work. We developed a Crestec Surface Electron emission Lithography (CSEL) for mass production of semiconductor devices. CSEL system is 1:1 electron projection lithography using surface electron emitter. In first report, we confirmed that a test bench of CSEL resolved below 30 nm pattern over 0.2 um square area. Practical resolution of the system is limited by the chromatic aberration. We also demonstrated the CSEL system exposed deep sub-micron pattern over full-field for practical use. As an interim report of our development of MPEBDW system, we evaluated characteristics of the

  11. An electron/ion spectrometer with the ability of low energy electron measurement for fast ignition experiments

    Energy Technology Data Exchange (ETDEWEB)

    Ozaki, T.; Sakagami, H. [National Institute for Fusion Science, 322-6, Oroshi, Toki, Gifu 509-5292 (Japan); Kojima, S.; Arikawa, Y.; Shiraga, H.; Fujioka, S. [Institute of Laser Engineering, Osaka University, 2-6, Yamada-oka, Suita, Osaka 565-0871 (Japan); Kato, R., E-mail: ozaki@nifs.ac.jp [Institute of Scientific and Industrial Research, Osaka University, 8-1, Mihogaoka, Ibaraki, Osaka 567-0047 (Japan)

    2014-11-15

    An electron energy spectrometer (ESM) is one of the most fundamental diagnostics in the fast ignition experiment. It is necessary to observe the spectra down to a low energy range in order to obtain the accurate deposition efficiency toward the core. Here, we realize the suitable ESM by using a ferrite magnet with a moderate magnetic field of 0.3 T and a rectangular magnetic circuit covered with a steel plate in the inlet side.

  12. Z-dependence of thick-target bremsstrahlung produced by monoenergetic low-energy electrons

    Science.gov (United States)

    Czarnecki, S.; Short, A.; Williams, S.

    2016-07-01

    The dependence of thick-target bremsstrahlung emitted by low-energy beams of monoenergetic electrons on the atomic number of the target material has been investigated experimentally for incident electron energies of 4.25 keV and 5.00 keV using thick aluminum, copper, silver, tungsten, and gold targets. Experimental data suggest that the intensity of the thick-target bremsstrahlung emitted is more strongly dependent on the atomic number of the target material for photons with energies that are approximately equal to the energy of the incident electrons than at lower energies, and also that the dependence of thick-target bremsstrahlung on the atomic number of the target material is stronger for incident electrons of higher energies than for incident electrons of lower energies. The results of the experiments are compared to the results of simulations performed using the PENELOPE program (which is commonly used in medical physics) and to thin-target bremsstrahlung theory, as well. Comparisons suggest that the experimental dependence of thick-target bremsstrahlung on the atomic number of the target material may be slightly stronger than the results of the PENELOPE code suggest.

  13. Low energy electron imaging of domains and domain walls in magnesium-doped lithium niobate

    Science.gov (United States)

    Nataf, G. F.; Grysan, P.; Guennou, M.; Kreisel, J.; Martinotti, D.; Rountree, C. L.; Mathieu, C.; Barrett, N.

    2016-09-01

    The understanding of domain structures, specifically domain walls, currently attracts a significant attention in the field of (multi)-ferroic materials. In this article, we analyze contrast formation in full field electron microscopy applied to domains and domain walls in the uniaxial ferroelectric lithium niobate, which presents a large 3.8 eV band gap and for which conductive domain walls have been reported. We show that the transition from Mirror Electron Microscopy (MEM - electrons reflected) to Low Energy Electron Microscopy (LEEM - electrons backscattered) gives rise to a robust contrast between domains with upwards (Pup) and downwards (Pdown) polarization, and provides a measure of the difference in surface potential between the domains. We demonstrate that out-of-focus conditions of imaging produce contrast inversion, due to image distortion induced by charged surfaces, and also carry information on the polarization direction in the domains. Finally, we show that the intensity profile at domain walls provides experimental evidence for a local stray, lateral electric field.

  14. SEM, TEM and SLEEM (scanning low energy electron microscopy) of CB2 steel after creep testing

    Science.gov (United States)

    Kasl, J.; Mikmeková, Š.; Jandová, D.

    2014-03-01

    The demand to produce electrical power with higher efficiency and with lower environmental pollution is leading to the use of new advanced materials in the production of power plant equipment. To understand the processes taking place in parts produced from these materials during their operation under severe conditions (such as high temperature, high stress, and environmental corrosion) requires detailed evaluation of their substructure. It is usually necessary to use transmission electron microscopy (TEM). However, this method is very exacting and time-consuming. So there is an effort to use new scanning electron microscopy techniques instead of TEM. One of them is scanning low energy electron microscopy (SLEEM). This paper deals with an assessment of the possibility to use SLEEM for describing the substructure of creep resistant steel CB2 after long-term creep testing. In the SLEEM images more information is contained about the microstructure of the material in comparison with standard scanning electron microscopy. Study of materials using slow and very slow electrons opens the way to better understanding their microstructures.

  15. Low energy electron imaging of domains and domain walls in magnesium-doped lithium niobate

    Science.gov (United States)

    Nataf, G. F.; Grysan, P.; Guennou, M.; Kreisel, J.; Martinotti, D.; Rountree, C. L.; Mathieu, C.; Barrett, N.

    2016-01-01

    The understanding of domain structures, specifically domain walls, currently attracts a significant attention in the field of (multi)-ferroic materials. In this article, we analyze contrast formation in full field electron microscopy applied to domains and domain walls in the uniaxial ferroelectric lithium niobate, which presents a large 3.8 eV band gap and for which conductive domain walls have been reported. We show that the transition from Mirror Electron Microscopy (MEM – electrons reflected) to Low Energy Electron Microscopy (LEEM – electrons backscattered) gives rise to a robust contrast between domains with upwards (Pup) and downwards (Pdown) polarization, and provides a measure of the difference in surface potential between the domains. We demonstrate that out-of-focus conditions of imaging produce contrast inversion, due to image distortion induced by charged surfaces, and also carry information on the polarization direction in the domains. Finally, we show that the intensity profile at domain walls provides experimental evidence for a local stray, lateral electric field. PMID:27608605

  16. Low-energy electronic recoil in xenon detectors by solar neutrinos

    CERN Document Server

    Chen, Jiunn-Wei; Liu, C -P; Wu, Chih-Pan

    2016-01-01

    Low-energy electronic recoil caused by solar neutrinos in multi-ton xenon detectors is an important subject not only because it is a source of the irreducible background for direct searches of weakly-interacting massive particles (WIMPs), but also because it provides a viable way to measure the solar $pp$ and $^{7}\\textrm{Be}$ neutrinos at the precision level of current standard solar model predictions. In this work we perform $\\textit{ab initio}$ many-body calculations for the structure, photoionization, and neutrino-ionization of xenon. It is found that the atomic binding effect yields a sizable suppression to the neutrino-electron scattering cross section at low recoil energies. Compared with the previous calculation based on the free electron picture, our calculated event rate of electronic recoil in the same detector configuration is reduced by about $25\\%$. We present in this paper the electronic recoil rate spectrum in the energy window of 100 eV - 30 keV with the standard per ton per year normalizatio...

  17. Low energy electrons and ultra-soft X-rays irradiation of plasmid DNA. Technical innovations

    Science.gov (United States)

    Fromm, Michel; Boulanouar, Omar

    2016-11-01

    In this paper we present in a first part the latest results of our group which are in relation with the study of DNA damages inflicted by low energy electrons (0-20 eV) in ultra-high vacuum as well as in air under atmospheric conditions. A short description of the drop-casting technique we developed to produce thin and nanometre-scaled DNA layers onto graphite sheets is given. We provide the absolute cross-section for loss of supercoiled topology of plasmid DNA complexed with 1,3-diaminopropane (Dap) in the vacuum under 10 eV electron impact and suggest a specific pathway for the dissociation of the transient negative ion formed by resonant capture of such a low energy electron (LEE) by the DNA's phosphate group when complexed to Dap. Well-gauged DNA-Dap layers with various nanometre-scaled thicknesses are used to evaluate the effective attenuation length of secondary photo-LEEs in the energy range (0-20 eV). The values of 11-16 nm for DNA kept under atmospheric conditions are in good agreement with the rare literature data available and which are stemming from computer simulations. In a second part, we describe the method we have developed in order to expose liquid samples of plasmid DNA to ultra-soft X-rays (Al Kα line at 1.5 keV) under hydroxyl radical scavenging conditions. We provide an experimentally determined percentage of indirect effects in aqueous medium kept under standard conditions of 94.7±2.1% indirect effects; in satisfactory agreement with the data published by others (i.e. 97.7%) relative to gamma irradiation of frozen solutions (Tomita et al., 1995).

  18. ROLE OF DIAMOND SECONDARY EMITTERS IN HIGH BRIGHTNESS ELECTRON SOURCES.

    Energy Technology Data Exchange (ETDEWEB)

    RAO, T.; BEN-ZVI, I.; BURRILL, A.; CHANG, X.; GRIMES, J.; RANK, J.; SEGALOV, Z.; SMEDLEY, J.

    2005-09-20

    In this paper we explore the possibility of using diamond secondary emitter in a high average current electron injector to amplify the current from the photocathode and to isolate the cathode and the injector from each other to increase the life time of the cathode and preserve the performance of the injector. Secondary electron yield of 225 and current density of 0.8 a/cm{sup 2} have been measured in the transmission mode from type 2 a natural diamond. Although the diamond will be heated during normal operation in the injector, calculations indicate that by cryogenically cooling the diamond, the temperature gradient along the diamond can be maintained within the acceptable range. The electron energy and temporal distributions are expected to be narrow from this device resulting in high brightness beams. Plans are underway to measure the SEY in emission mode, fabricate photocathode-diamond capsule and test diamond and capsule in superconducting RF injector.

  19. Treatment of foods with 'soft-electrons' (low-energy electrons)

    Energy Technology Data Exchange (ETDEWEB)

    Hayashi, Toru [Japan International Research Center for Agricultural Sciences (JIRCAS), Tsukuba, Ibaraki (Japan); Todoriki, Setsuko [National Food Research Institute (NFRI), Tsukuba, Ibaraki (Japan)

    2003-02-01

    Electrons with energies of 300 keV or lower were defined as soft-electrons'. Soft-electrons can eradicate microorganisms residing on the surface of grains, pulses, spices, dehydrated vegetables, tea leaves and seeds, and reduce their microbial loads to levels lower than 10 CFU/g with little quality deterioration. Soft-electrons can inactivate insect pests infesting grains and pulses and inhibit sprouting of potatoes. (author)

  20. Low-Energy Electron Impact Excitation of the (010) Bending Mode of CO2

    Science.gov (United States)

    Huo, Winifred M.; Langhoff, Stephen R. (Technical Monitor)

    1996-01-01

    Low-energy electron impact excitation of the fundamental modes of CO2 has been extensively studied, both experimentally and theoretically. Much attention has been paid to the virtual state feature in the the (100) mode excitation and the (sup 2)II(sub upsilon) resonance feature around 3.8 eV, which is observable in all three fundamental modes. For the excitation of the (010) mode away from the resonance region, the Born dipole approximation was generally considered adequate. The present study employs the Born dipole approximation to treat the long range interaction and the Schwinger multichannel method for the short range interaction. The roles of the two interaction potentials will be compared.

  1. Low-energy electron diffraction experiment, theory and surface structure determination

    CERN Document Server

    Hove, Michel A; Chan, Chi-Ming

    1986-01-01

    Surface crystallography plays the same fundamental role in surface science which bulk crystallography has played so successfully in solid-state physics and chemistry. The atomic-scale structure is one of the most important aspects in the understanding of the behavior of surfaces in such widely diverse fields as heterogeneous catalysis, microelectronics, adhesion, lubrication, cor­ rosion, coatings, and solid-solid and solid-liquid interfaces. Low-Energy Electron Diffraction or LEED has become the prime tech­ nique used to determine atomic locations at surfaces. On one hand, LEED has yielded the most numerous and complete structural results to date (almost 200 structures), while on the other, LEED has been regarded as the "technique to beat" by a variety of other surface crystallographic methods, such as photoemission, SEXAFS, ion scattering and atomic diffraction. Although these other approaches have had impressive successes, LEED has remained the most productive technique and has shown the most versatility...

  2. Low-energy electron attachment to mixed ozone/oxygen clusters

    Science.gov (United States)

    Matejcik, S.; Cicman, P.; Kiendler, A.; Skalny, J. D.; Illenberger, E.; Stamatovic, A.; Märk, T. D.

    1996-10-01

    Electron attachment to a cluster beam formed by adiabatic expansion of a mixture of O 3 (1%) and O 2 (99%) is studied in the energy range 0-4 eV. Despite the initial large excess of oxygen molecules, the dominant attachment products are undissociated cluster ions (O 3) m- including the monomer O 3-, while oxygen cluster ions (O 2) n- appear with comparatively low intensity. This behaviour is explained by an enrichment of ozone in the cluster formation process and the preferential formation of O 3- from mixed clusters. The structured energy dependence of the cross section of O 3- formation is interpreted in terms of three different mechanisms, in the low-energy region by s-wave capture, around 1 eV via Feshbach resonances, and above 1.5 eV by self-scavenging, i.e. inelastic scattering of the primary electron involving low-lying electronic states of neutral ozone and subsequent attachment of the slowed-down electron to another ozone molecule in the same cluster.

  3. Evaluation of low energy electron beam dose application by means of a portable optical device

    Science.gov (United States)

    Reitzig, Manuela; Winkler, Martin; Härtling, Thomas; Röder, Olaf; Opitz, Jörg

    2014-11-01

    We present our recent development concerning the evaluation of a low energy dose application to electron beam responding materials with a simple portable optical device. Electron beam irradiation is a promising option to sterilize sensitive and high performance products or surfaces at a low temperature and without moisture. Especially in the fields of the food industry and medicine, regulations regarding sterility are increasingly tightened. Because of this, a secure proof for electron-beam-assisted sterilization is required. However, no nondestructive and in situ method exists up until now. Our approach to provide a secure proof of sterilization is to place a suitable marker material based on rare-earth-doped phosphors inside or on the top of the packaging material of the respective product. Upon electron irradiation the marker material changes its luminescence properties as a function of the applied energy dose. We verified the energy dependence by means of time-resolved measurements of the luminescence decay of an upconversion phosphor with a portable optical device. In our experimental realization, short laser pulses in the near-infrared range are triggered by a microcontrol unit (MCU) and excite the marker material. The light emitted by the marker is collected in the range between 400 and 1100 nm via a silicon photodiode, processed by the MCU, and analyzed in a Labview program via a single-exponential fit. As a main result, we observe an increasing reduction of the luminescence lifetime with higher dose applications.

  4. Performance Studies of the Vibration Wire Monitor on the Test Stand with Low Energy Electron Beam

    Science.gov (United States)

    Okabe, Kota; Yoshimoto, Masahiro; Kinsho, Michikazu

    In the high intensity proton accelerator as the Japan Proton Accelerator Research Complex (J-PARC) accelerators, serious radiation and residual dose is induced by a small beam loss such a beam halo. Therefore, diagnostics of the beam halo formation is one of the most important issues to control the beam loss. For the beam halo monitor, the vibration wire monitor (VWM) has a potential for investigating the beam halo and weak beam scanning. The VWM has a wide dynamic range, high resolution and the VWM is not susceptible to secondary electrons and electric noises. We have studied the VWM features as a new beam-halo monitor on the test stand with low energy electron gun. The frequency shift of the irradiated vibration wire was confirmed about wire material and the electron beam profile measured by using the VWM was consistent with the results of the Faraday cup measurement. Also we calculated a temperature distribution on the vibration wire which is irradiated by the electron beam with the numerical simulation. The simulations have been fairly successful in reproducing the transient of the irradiated vibration wire frequency measured by test stand experiments. In this paper, we will report a result of performance evaluation for the VWM on the test stands and discuss the VWM for beam halo diagnostic

  5. Measurements of the Electron Cloud Density in the PEP-II Low Energy Ring

    Energy Technology Data Exchange (ETDEWEB)

    Byrd, John; De Santis, Stefano; Sonnad, Kiran; Caspers, Fritz; Kroyer, Tom; Krasnykh, Anatoly; Pivi, Mauro

    2008-06-01

    Clouds of low energy electronsin the vacuum beam pipes of accelerators of positively charged particle beams present a serious limitation for operation of these machines at high currents. Because of the size of these accelerators, it is difficult to probe the low energyelectron clouds over substantial lengths of the beam pipe. We have developed a novel technique to directly measure the electron cloud density via the phase shift induced in a TE wave that is independently excited and transmitted over a section of the accelerator. We infer the absolute phase shift with relatively high accuracy from the phase modulation of the transmission due to the modulation of the electron cloud density from a gap in the positively charged beam. We have used this technique for the first time to measure the average electron cloud density over a 50 m straight section in the positron ring of the PEP-II collider at the Stanford Linear Accelerator Center. We have also measured the variation of the density by using low field solenoid magnets to control the electrons.

  6. Sterilization of foods with low-energy electrons (``soft-electrons'')

    Science.gov (United States)

    Hayashi, Toru; Takahashi, Yoko; Todoriki, Setsuko

    1998-06-01

    Electrons with an energy of 300 keV or lower were defined as "Soft-electrons", which showed several advantages over conventional irradiation with gamma-rays or high-energy electrons in decontamination of grains and spices. Energies of electrons necessary to reduce microbial loads to levels lower than 10 CFU/g were 60 keV for brown rice, 75 keV for wheat, 100 keV for white pepper, coriander and basil, 130 keV for buckwheat, 160 keV for rough rice, and 210 keV for black pepper. Electrons with such energies did not significantly influence the quality.

  7. Sterilization of foods with low-energy electrons ('soft-electrons')

    Energy Technology Data Exchange (ETDEWEB)

    Hayashi, Toru; Takahashi, Yoko; Todoriki, Setsuko

    1998-06-01

    Electrons with an energy of 300 keV or lower were defined as 'Soft-electrons', which showed several advantages over conventional irradiation with gamma-rays or high-energy electrons in decontamination of grains and spices. Energies of electrons necessary to reduce microbial loads to levels lower than 10 CFU/g were 60 keV for brown rice, 75 keV for wheat, 100 keV for white pepper, coriander and basil, 130 keV for buckwheat, 160 keV for rough rice, and 210 keV for black pepper. Electrons with such energies did not significantly influence the quality.

  8. Soft electron (low energy electron) processing of foods for microbial control

    Energy Technology Data Exchange (ETDEWEB)

    Todoriki, Setsuko E-mail: setsuko@nfri.affrc.go.jp; Kikuchi, Olivia Kimiko; Nakaoka, Motoko; Miike, Mika; Hayashi, Toru

    2002-03-01

    'Soft-electron' is a new term we have created referring to electrons with energies of 300 kV or lower. Homogenous irradiation of surfaces with soft electrons can decontaminate dry food ingredients such as gains, pulses, spices, dehydrated vegetables and tealeaves without detrimental effects. Treatment of soybeans with electrons of acceleration voltages at 170 kV reduced their microbial count to an undetectable level. Pre-treatment of soybeans with soft electrons enabled the extension of soymilk without sterilization process at a high temperature (120 deg. C). The gelatinized property of soymilk from soft electron-treated beans was better than that of high-temperature sterilized soymilks. These results indicate that soft-electron sterilization improved the quality of soybeans for the processing of soymilk and Tofu(soymilk curd)

  9. Extra Low ENergy Antiproton

    CERN Multimedia

    To produce dense antiproton beams at very low energies (110 keV), it has been proposed to install a small decelerator ring between the existing AD ring and the experimental area. Phase-space blowup during deceleration is compensated by electron cooling such that the final emittances are comparable to the 5MeV beam presently delivered by the AD. An immediate consequence is a significant increase in the number of trapped antiprotons at the experiments as outlined in the proposal CERN/SPSC-2009-026; SPCS-P-338. This report describes the machine parameters and layout of the proposal ELENA (Extra Low ENergy Antiproton)ring also gives an approximate estimate of cost and manpower needs. Since the initial estimate, published in 2007 (CERN-AB-2007-079), the ELENA design has evolved considerably. This is due to a new location in the AD hall to acommodate for the possibility of another experimental zone, as suggested by the SPCS, and also due to improvements in the ring optics and layout. The cost estimate that is prese...

  10. Low-energy electron attachment and detachment in vibrationally excited oxygen

    Energy Technology Data Exchange (ETDEWEB)

    Aleksandrov, N L; Anokhin, E M, E-mail: nick_aleksandrov@mail.r, E-mail: nick_aleksandrov@hotmail.co [Moscow Institute of Physics and Technology, Dolgoprudny, 141700 (Russian Federation)

    2009-11-21

    Three-body electron attachment to O{sub 2} molecules and electron detachment from O{sub 2}{sup -} ions have been theoretically studied in vibrationally excited oxygen and O{sub 2}-containing mixtures. Assuming that electron attachment and detachment proceed via the formation of vibrationally excited temporary O{sub 2}{sup -} ions, the rates of these processes were determined on the basis of the statistical approach for the vibrational transfer and relaxation in collisions between O{sub 2}{sup -} ions and O{sub 2} molecules. The calculated attachment and detachment rate constants turned out to agree well with available measurements in unexcited oxygen. This method was extended to calculate attachment and detachment rates in vibrationally excited oxygen. It was shown that the effect of vibrational excitation on electron detachment is profound, whereas attachment of low-energy electrons to vibrationally excited O{sub 2} is inefficient. The calculated vibrational distribution of stable O{sub 2}{sup -} ions turned out to be non-equilibrium in an excited gas and the effective vibrational temperature of the ions was much lower than the vibrational temperature of molecules. An analytical method was suggested to determine this distribution and the effective vibrational temperature. The calculated rate constants were used to simulate the formation and decay of an electron-beam-generated plasma in N{sub 2} : O{sub 2} mixtures at elevated vibrational temperatures. The calculations showed that vibrational excitation of molecules leads to orders of magnitude increase in the plasma density and in the plasma lifetime, in agreement with available observations.

  11. Interaction of low energy electrons with DNA: Applications to cancer radiation therapy

    Science.gov (United States)

    Sanche, Léon

    2016-11-01

    Presently, there exists considerable information on the mechanisms involved when low-energy electrons (LEEs) interact with biomolecules, including DNA. Since these electrons are produced in large quantities by ionizing radiation, knowing their mechanisms of action increases our understanding of radiobiological damage and modifications of this damage by morphological or chemical changes introduced in the DNA. In the present article, the results of experiments on LEE-induced damage to DNA modified by radiosensitizers, chemotherapeutic agents and gold nanoparticles are reviewed. DNA strand breaks and multiple lesions become more numerous with such modifications. They are usually due to an increase in the number and probability of forming transient anions of DNA constituents, and their decay into destructive channels, such as dissociative electron attachment. As shown in this review, by invoking the role of LEEs in the processes of radiosensitization, guidelines can be provided for the development of new radiosensitizers and improved protocols in the treatment of cancer patients with radiotherapy alone or in concomitance with chemotherapy.

  12. Low Energy Electron Cooling and Accelerator Physics for the Heidelberg CSR

    Science.gov (United States)

    Fadil, H.; Grieser, M.; von Hahn, R.; Orlov, D.; Schwalm, D.; Wolf, A.; Zajfman, D.

    2006-03-01

    The Cryogenic Storage Ring (CSR) is currently under construction at MPI-K in Heidelberg. The CSR is an electrostatic ring with a total circumference of about 34 m, straight section length of 2.5 m and will store ions in the 20 ˜ 300 keV energy range (E/Q). The cryogenic system in the CSR is expected to cool the inner vacuum chamber down to 2 K. The CSR will be equipped with an electron cooler which has also to serve as an electron target for high resolution recombination experiments. In this paper we present the results of numerical investigations of the CSR lattice with finite element calculations of the deflection and focusing elements of the ring. We also present a layout of the CSR electron cooler which will have to operate in low energy mode to cool 20 keV protons in the CSR, as well as numerical estimations of the cooling times to be expected with this device.

  13. Probing Graphene by Low-Energy Electrons under Non-normal Incidence

    Science.gov (United States)

    Jobst, Johannes; Kautz, Jaap; Geelen, Daniel; Tromp, Rudolf M.; van der Molen, Sense Jan

    2015-03-01

    Low-energy electron microscopy (LEEM) is a powerful surface analysis tool for investigating samples in real and reciprocal space. Moreover, spectroscopic information can be obtained by measuring LEEM-IV, i.e., the energy dependence of the reflected electron intensity. Here, we focus on the study of monolayer and bilayer graphene grown on silicon carbide. Its layered character gives rise to minima in the LEEM-IV, which are used to unambiguously determine the layer thickness as the number of minima is equal to the number of conducting graphene layers. In a typical LEEM experiment it is crucial to align the sample such that the electrons impinge perpendicular on the surface in order to guarantee ideal imaging conditions. In this study we, however, present a systematic analysis of the effect of beam tilt on the LEEM-IV. We find pronounced changes in shape depending on the tilt angle with respect to crystallographic axes. These changes can be related to the band structure of few-layer graphene. This work was supported by the Netherlands Organization for Scientific Research (NWO) via an NWO-Groot Grant (``ESCHER'') and a VIDI Grant (#680-47-502, SJvdM), by the FOM foundation via the ``Physics in 1D'' program.

  14. Effect of low energy electron irradiation on DNA damage by Cu{sup 2+} ion

    Energy Technology Data Exchange (ETDEWEB)

    Noh, Hyung Ah; Cho, Hyuck [Dept. of Physics, Chungnam National University, Daejeon (Korea, Republic of); Park, Yeun Soo [Plasma Technology Research Center, National Fusion Research Institute, Gunsan (Korea, Republic of)

    2017-03-15

    The combined effect of the low energy electron (LEE) irradiation and Cu{sup 2+} ion on DNA damage was investigated. Lyophilized pBR322 plasmid DNA films with various concentrations (1–15 mM) of Cu{sup 2+} ion were independently irradiated by monochromatic LEEs with 5 eV. The types of DNA damage, single strand break (SSB) and double strand break (DSB), were separated and quantified by gel electrophoresis. Without electron irradiation, DNA damage was slightly increased with increasing Cu ion concentration via Fenton reaction. LEE-induced DNA damage, with no Cu ion, was only 6.6% via dissociative electron attachment (DEA) process. However, DNA damage was significantly increased through the combined effect of LEE-irradiation and Cu ion, except around 9 mM Cu ion. The possible pathways of DNA damage for each of these different cases were suggested. The combined effect of LEE-irradiation and Cu ion is likely to cause increasing dissociation after elevated transient negative ion state, resulting in the enhanced DNA damage. For the decrease of DNA damage at around 9-mM Cu ion, it is assumed to be related to the structural stabilization due to DNA inter- and intra-crosslinks via Cu ion.

  15. Low-energy electron elastic scattering from Os atom: New electron affinity

    Science.gov (United States)

    Felfli, Z.; Kiros, F.; Msezane, A. Z.

    2013-05-01

    Bilodeau and Haugan measured the binding energies (BEs) of the ground state and the excited state of the Os- ion to be 1.07780(12) eV and 0.553(3) eV, respectively. These values are consistent with those calculated in. Here our investigation, using the recent complex angular momentum methodology wherein is embedded the crucial electron-electron correlations and the vital core polarization interaction, has found that the near threshold electron-Os elastic scattering total cross section (TCS) is characterized by three stable bound states of the Os- ion formed as resonances during the slow electron collision, with BEs of 1.910 eV, 1.230 eV and 0.224 eV. The new extracted electron affinity (EA) value from the TCS of 1.910 eV for the Os atom is significantly different from that measured in. Our calculated elastic differential cross sections (DCSs) also yield the relevant BEs for the ground and the two excited states of the Os- ion. The complex characteristic resonance structure in the TCS for the Os atom is ideal for catalysis, but makes it difficult to execute the Wigner threshold law in describing the threshold detachment behavior of complex atoms and extracting the reliable attendant EAs. Supported by U.S. DOE, AFOSR and CAU CFNM, NSF-CREST Program.

  16. Model of convection mass transfer in titanium alloy at low energy high current electron beam action

    Science.gov (United States)

    Sarychev, V. D.; Granovskii, A. Yu; Nevskii, S. A.; Konovalov, S. V.; Gromov, V. E.

    2017-01-01

    The convection mixing model is proposed for low-energy high-current electron beam treatment of titanium alloys, pre-processed by heterogeneous plasma flows generated via explosion of carbon tape and powder TiB2. The model is based on the assumption vortices in the molten layer are formed due to the treatment by concentrated energy flows. These vortices evolve as the result of thermocapillary convection, arising because of the temperature gradient. The calculation of temperature gradient and penetration depth required solution of the heat problem with taking into account the surface evaporation. However, instead of the direct heat source the boundary conditions in phase transitions were changed in the thermal conductivity equation, assuming the evaporated material takes part in the heat exchange. The data on the penetration depth and temperature distribution are used for the thermocapillary model. The thermocapillary model embraces Navier-Stocks and convection heat transfer equations, as well as the boundary conditions with the outflow of evaporated material included. The solution of these equations by finite elements methods pointed at formation of a multi-vortices structure when electron-beam treatment and its expansion over new zones of material. As the result, strengthening particles are found at the depth exceeding manifold their penetration depth in terms of the diffusion mechanism.

  17. Monte Carlo Commissioning of Low Energy Electron Radiotherapy Beams using NXEGS Software

    Directory of Open Access Journals (Sweden)

    2004-06-01

    Full Text Available This work is a report on the commissioning of low energy electron beams of a medical linear accelerator for Monte Carlo dose calculation using NXEGS software (NXEGS version 1.0.10.0, NX Medical Software, LLC. A unique feature of NXEGS is automated commissioning, a process whereby a combination of analytic and Monte Carlo methods generates beam models from dosimetric data collected in a water phantom. This study uses NXEGS to commission 6, 9, and 12 MeV electron beams of a Varian Clinac 2100C using three applicators with standard inserts. Central axis depth-dose, primary axis and diagonal beam profiles, and output factors are the measurements necessary for commissioning of the code. We present a comparison of measured dose distributions with the distributions generated by NXEGS, using confidence limits on seven measures of error. We find that confidence limits are typically less than 3% or 3 mm, but increase with increasing source to surface distance (SSD and depth at or beyond R50. We also investigate the dependence of NXEGS' performance on the size and composition of data used to commission the program, finding a weak dependence on number of dose profiles in the data set, but finding also that commissioning data need be measured at only two SSDs.

  18. Experimental investigation of electron cooling and stacking of lead ions in a low energy accumulation ring

    CERN Document Server

    Bosser, Jacques; Chanel, M; Hill, C; Lombardi, A M; MacCaferri, R; Maury, S; Möhl, D; Molinari, G; Rossi, S; Tanke, E; Tranquille, G; Vretenar, Maurizio

    1999-01-01

    This report gives the results of a programme of experimental investigations, which were carried out to test stacking of lead ions in a storage ring (the former Low Energy Antiproton Ring, LEAR) at 4.2 MeV per nucleon. The motivation was to demonstrate the feasibility of gaining the large factor in the phase-space density required for injection into the LHC. In the first part of the report, the layout of the experiments is described, the choice of the parameters of the electron cooling system used for stacking is reported and the multi-turn injection using horizontal- and longitudinal- (and in the final project also vertical-) phase space is discussed. In the second part the experimental results are presented. Factors of vital importance are the stacking efficiency, the beam life-time and the cooling time of the ions. The beam decay owing to charge exchange with the residual gas and to recombination by the capture of cooling electrons was intensively studied. Beam instabilities and space-charge effects in the ...

  19. Pathogens Inactivated by Low-Energy-Electron Irradiation Maintain Antigenic Properties and Induce Protective Immune Responses.

    Science.gov (United States)

    Fertey, Jasmin; Bayer, Lea; Grunwald, Thomas; Pohl, Alexandra; Beckmann, Jana; Gotzmann, Gaby; Casado, Javier Portillo; Schönfelder, Jessy; Rögner, Frank-Holm; Wetzel, Christiane; Thoma, Martin; Bailer, Susanne M; Hiller, Ekkehard; Rupp, Steffen; Ulbert, Sebastian

    2016-11-23

    Inactivated vaccines are commonly produced by incubating pathogens with chemicals such as formaldehyde or β-propiolactone. This is a time-consuming process, the inactivation efficiency displays high variability and extensive downstream procedures are often required. Moreover, application of chemicals alters the antigenic components of the viruses or bacteria, resulting in reduced antibody specificity and therefore stimulation of a less effective immune response. An alternative method for inactivation of pathogens is ionizing radiation. It acts very fast and predominantly damages nucleic acids, conserving most of the antigenic structures. However, currently used irradiation technologies (mostly gamma-rays and high energy electrons) require large and complex shielding constructions to protect the environment from radioactivity or X-rays generated during the process. This excludes them from direct integration into biological production facilities. Here, low-energy electron irradiation (LEEI) is presented as an alternative inactivation method for pathogens in liquid solutions. LEEI can be used in normal laboratories, including good manufacturing practice (GMP)- or high biosafety level (BSL)-environments, as only minor shielding is necessary. We show that LEEI efficiently inactivates different viruses (influenza A (H3N8), porcine reproductive and respiratory syndrome virus (PRRSV), equine herpesvirus 1 (EHV-1)) and bacteria (Escherichia coli) and maintains their antigenicity. Moreover, LEEI-inactivated influenza A viruses elicit protective immune responses in animals, as analyzed by virus neutralization assays and viral load determination upon challenge. These results have implications for novel ways of developing and manufacturing inactivated vaccines with improved efficacy.

  20. Surface Modification of Light Alloys by Low-Energy High-Current Pulsed Electron Beam

    Directory of Open Access Journals (Sweden)

    X. D. Zhang

    2012-01-01

    Full Text Available This paper reviews results obtained by the research groups developing the low-energy high-current pulsed electron beam (LEHCPEB in Dalian (China and Metz (France on the surface treatment of light alloys. The pulsed electron irradiation induces an ultra-fast thermal cycle at the surface combined with the formation of thermal stress and shock waves. As illustrated for Mg alloys and Ti, this results in deep subsurface hardening (over several 100 μm which improves the wear resistance. The analysis of the top surface melted surface of light alloys also often witnesses evaporation and condensation of chemical species. This phenomenon can significantly modify the melt chemistry and was also suggested to lead to the development of specific solidification textures in the rapidly solidified layer. The potential use of the LEHCPEB technique for producing thermomechanical treatments under the so-called heating mode and, thus, modify the surface crystallographic texture, and enhance solid-state diffusion is also demonstrated in the case of the FeAl intermetallic compound.

  1. Pathogens Inactivated by Low-Energy-Electron Irradiation Maintain Antigenic Properties and Induce Protective Immune Responses

    Science.gov (United States)

    Fertey, Jasmin; Bayer, Lea; Grunwald, Thomas; Pohl, Alexandra; Beckmann, Jana; Gotzmann, Gaby; Casado, Javier Portillo; Schönfelder, Jessy; Rögner, Frank-Holm; Wetzel, Christiane; Thoma, Martin; Bailer, Susanne M.; Hiller, Ekkehard; Rupp, Steffen; Ulbert, Sebastian

    2016-01-01

    Inactivated vaccines are commonly produced by incubating pathogens with chemicals such as formaldehyde or β-propiolactone. This is a time-consuming process, the inactivation efficiency displays high variability and extensive downstream procedures are often required. Moreover, application of chemicals alters the antigenic components of the viruses or bacteria, resulting in reduced antibody specificity and therefore stimulation of a less effective immune response. An alternative method for inactivation of pathogens is ionizing radiation. It acts very fast and predominantly damages nucleic acids, conserving most of the antigenic structures. However, currently used irradiation technologies (mostly gamma-rays and high energy electrons) require large and complex shielding constructions to protect the environment from radioactivity or X-rays generated during the process. This excludes them from direct integration into biological production facilities. Here, low-energy electron irradiation (LEEI) is presented as an alternative inactivation method for pathogens in liquid solutions. LEEI can be used in normal laboratories, including good manufacturing practice (GMP)- or high biosafety level (BSL)-environments, as only minor shielding is necessary. We show that LEEI efficiently inactivates different viruses (influenza A (H3N8), porcine reproductive and respiratory syndrome virus (PRRSV), equine herpesvirus 1 (EHV-1)) and bacteria (Escherichia coli) and maintains their antigenicity. Moreover, LEEI-inactivated influenza A viruses elicit protective immune responses in animals, as analyzed by virus neutralization assays and viral load determination upon challenge. These results have implications for novel ways of developing and manufacturing inactivated vaccines with improved efficacy. PMID:27886076

  2. On artefact-free reconstruction of low-energy (30–250 eV) electron holograms

    Energy Technology Data Exchange (ETDEWEB)

    Latychevskaia, Tatiana, E-mail: tatiana@physik.uzh.ch; Longchamp, Jean-Nicolas; Escher, Conrad; Fink, Hans-Werner

    2014-10-15

    Low-energy electrons (30–250 eV) have been successfully employed for imaging individual biomolecules. The most simple and elegant design of a low-energy electron microscope for imaging biomolecules is a lensless setup that operates in the holographic mode. In this work we address the problem associated with the reconstruction from the recorded holograms. We discuss the twin image problem intrinsic to inline holography and the problem of the so-called biprism-like effect specific to low-energy electrons. We demonstrate how the presence of the biprism-like effect can be efficiently identified and circumvented. The presented sideband filtering reconstruction method eliminates the twin image and allows for reconstruction despite the biprism-like effect, which we demonstrate on both, simulated and experimental examples. - Highlights: • Radiation damage-free imaging of individual biomolecules. • Elimination of the twin image in inline holograms. • Circumventing biprism-like effect in low-energy electron holograms. • Artefact-free reconstructions of low-energy electron holograms.

  3. Radiation from Ag and K films bombarded by low energy electrons

    Energy Technology Data Exchange (ETDEWEB)

    Chung, M.S.; Callcott, T.A.; Arakawa, E.T.

    1978-11-01

    Photon spectra from metallic films irradiated by low energy electrons (10-1500 eV) have been investigated. Both radiative and non-radiative plasmon modes have been studied. For silver films two peaks were resolved when the films were very smooth. One, at 3.73 eV the bulk plasmon energy, is thought to be ordinary transition radiation which results from the decay of plasmon modes directly coupled to the external electromagnetic field. The second, at about 3.60 eV, is very sensitive to surface roughness in both position and magnitude and is produced by roughness-coupled radiation from non-radiative surface plasmons. For rough films, this surface plasmon peak dominates the emission and persists to electron energies at least as low as 10 eV. The intensity of the surface-plasmon radiation was measured as a function of the incident electron energy for energies between 100 eV and 1200 eV and found to have a linear dependence. This result is shown to be consistent with theory. For potassium films bulk and surface plasmon radiation peaks were observed at 3.83 eV and 2.82 eV, respectively. The surface plasmon radiation was very sensitive to the temperature of the film and the pressure in the experimental chamber. No surface plasmon radiation peak (2.82 eV) was observed with uncooled potassium films. It is thought that the film was melted by the electron beam and that the resulting smooth film could not couple surface plasmons to the radiation field.

  4. Monte Carlo dose calculation improvements for low energy electron beams using eMC.

    Science.gov (United States)

    Fix, Michael K; Frei, Daniel; Volken, Werner; Neuenschwander, Hans; Born, Ernst J; Manser, Peter

    2010-08-21

    The electron Monte Carlo (eMC) dose calculation algorithm in Eclipse (Varian Medical Systems) is based on the macro MC method and is able to predict dose distributions for high energy electron beams with high accuracy. However, there are limitations for low energy electron beams. This work aims to improve the accuracy of the dose calculation using eMC for 4 and 6 MeV electron beams of Varian linear accelerators. Improvements implemented into the eMC include (1) improved determination of the initial electron energy spectrum by increased resolution of mono-energetic depth dose curves used during beam configuration; (2) inclusion of all the scrapers of the applicator in the beam model; (3) reduction of the maximum size of the sphere to be selected within the macro MC transport when the energy of the incident electron is below certain thresholds. The impact of these changes in eMC is investigated by comparing calculated dose distributions for 4 and 6 MeV electron beams at source to surface distance (SSD) of 100 and 110 cm with applicators ranging from 6 x 6 to 25 x 25 cm(2) of a Varian Clinac 2300C/D with the corresponding measurements. Dose differences between calculated and measured absolute depth dose curves are reduced from 6% to less than 1.5% for both energies and all applicators considered at SSD of 100 cm. Using the original eMC implementation, absolute dose profiles at depths of 1 cm, d(max) and R50 in water lead to dose differences of up to 8% for applicators larger than 15 x 15 cm(2) at SSD 100 cm. Those differences are now reduced to less than 2% for all dose profiles investigated when the improved version of eMC is used. At SSD of 110 cm the dose difference for the original eMC version is even more pronounced and can be larger than 10%. Those differences are reduced to within 2% or 2 mm with the improved version of eMC. In this work several enhancements were made in the eMC algorithm leading to significant improvements in the accuracy of the dose

  5. A novel low energy electron microscope for DNA sequencing and surface analysis

    Energy Technology Data Exchange (ETDEWEB)

    Mankos, M., E-mail: marian@electronoptica.com [Electron Optica Inc., 1000 Elwell Court #110, Palo Alto, CA 94303 (United States); Shadman, K. [Electron Optica Inc., 1000 Elwell Court #110, Palo Alto, CA 94303 (United States); Persson, H.H.J. [Stanford Genome Technology Center, Stanford University School of Medicine, 855 California Avenue, Palo Alto, CA 94304 (United States); N’Diaye, A.T. [Electron Optica Inc., 1000 Elwell Court #110, Palo Alto, CA 94303 (United States); NCEM, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Schmid, A.K. [NCEM, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Davis, R.W. [Stanford Genome Technology Center, Stanford University School of Medicine, 855 California Avenue, Palo Alto, CA 94304 (United States)

    2014-10-15

    Monochromatic, aberration-corrected, dual-beam low energy electron microscopy (MAD-LEEM) is a novel technique that is directed towards imaging nanostructures and surfaces with sub-nanometer resolution. The technique combines a monochromator, a mirror aberration corrector, an energy filter, and dual beam illumination in a single instrument. The monochromator reduces the energy spread of the illuminating electron beam, which significantly improves spectroscopic and spatial resolution. Simulation results predict that the novel aberration corrector design will eliminate the second rank chromatic and third and fifth order spherical aberrations, thereby improving the resolution into the sub-nanometer regime at landing energies as low as one hundred electron-Volts. The energy filter produces a beam that can extract detailed information about the chemical composition and local electronic states of non-periodic objects such as nanoparticles, interfaces, defects, and macromolecules. The dual flood illumination eliminates charging effects that are generated when a conventional LEEM is used to image insulating specimens. A potential application for MAD-LEEM is in DNA sequencing, which requires high resolution to distinguish the individual bases and high speed to reduce the cost. The MAD-LEEM approach images the DNA with low electron impact energies, which provides nucleobase contrast mechanisms without organometallic labels. Furthermore, the micron-size field of view when combined with imaging on the fly provides long read lengths, thereby reducing the demand on assembling the sequence. Experimental results from bulk specimens with immobilized single-base oligonucleotides demonstrate that base specific contrast is available with reflected, photo-emitted, and Auger electrons. Image contrast simulations of model rectangular features mimicking the individual nucleotides in a DNA strand have been developed to translate measurements of contrast on bulk DNA to the detectability of

  6. Influence of Small Impurities on Low-Energy Electron Dynamics in Two-Dimensional Microscopic Bounded Region

    CERN Document Server

    Shigehara, T; Mizoguchi, H; Mishima, T; Cheon, T; Cheon, Taksu

    1998-01-01

    In order to give some insight into a role of small impurities on the electron motion in microscopic devices, we examine from a general viewpoint, the effect of small obstacles on a particle motion at low energy inside microscopic bounded regions. It will be shown that the obstacles disturb the electron motion only if they are weakly attractive.

  7. The role of low-energy electrons in focused electron beam induced deposition: four case studies of representative precursors

    Directory of Open Access Journals (Sweden)

    Rachel M. Thorman

    2015-09-01

    Full Text Available Focused electron beam induced deposition (FEBID is a single-step, direct-write nanofabrication technique capable of writing three-dimensional metal-containing nanoscale structures on surfaces using electron-induced reactions of organometallic precursors. Currently FEBID is, however, limited in resolution due to deposition outside the area of the primary electron beam and in metal purity due to incomplete precursor decomposition. Both limitations are likely in part caused by reactions of precursor molecules with low-energy (3, Pt(PF34, Co(CO3NO, and W(CO6. Through these case studies, it is evident that this combination of studies can provide valuable insight into potential mechanisms governing deposit formation in FEBID. Although further experiments and new approaches are needed, these studies are an important stepping-stone toward better understanding the fundamental physics behind the deposition process and establishing design criteria for optimized FEBID precursors.

  8. 低能离子束横向发射度的测量及分析%Measuring and Analyzing Transverse Low-Energy Ion Beam Emittances

    Institute of Scientific and Technical Information of China (English)

    M.P.Stockli

    2007-01-01

    The transverse emittance of an ion beam describes its transverse size as the particles are transported from a source to a target.It allows for predicting beam losses in limiting apertures and the beam focus size at the target.Various definitions and issues are discussed.The most common and emerging measuring techniques are presented,including their advantages.Several methods of emittance data analysis,their accuracy and trustworthiness,are discussed.

  9. Electron to Muon Conversion in Low-Energy Electron-Nucleus Scattering

    CERN Document Server

    Diener, Kai-Peer O

    2004-01-01

    We present an estimate of the electron to muon conversion cross section in fixed-target elastic electron scattering. The matrix element $$ is calculated analytically in two scenarios introducing suitable approximations. We consider on the one hand side the case of three light Dirac neutrinos with CKM-type leptonic mixing and on the other hand a typical see-saw scenario. We evaluate the coulombic contribution to the scattering cross section in the limit of vanishing energy transfer to the nucleus and, thus, obtain a realistic estimate for the total conversion cross section. Although we find that in the see-saw scenario the cross section can be enhanced by as much as twenty orders of magnitude in comparison to the Dirac case, it is still not experimentally accessible.

  10. On artefact-free reconstruction of low-energy (30-250 eV) electron holograms

    CERN Document Server

    Latychevskaia, Tatiana; Escher, Conrad; Fink, Hans-Werner

    2013-01-01

    Low-energy electrons (30-250 eV) have been successfully employed for imaging individual biomolecules. The most simple and elegant design of a low-energy electron microscope for imaging biomolecules is a lensless setup that operates in the holographic mode. In this work we address the problem associated with the reconstruction from the recorded holograms. We discuss the twin image problem intrinsic to inline holography and the problem of the so-called biprism-like effect specific to low-energy electrons. We demonstrate how the presence of the biprism-like effect can be efficiently identified and circumvented. The presented sideband filtering reconstruction method eliminates the twin image and allows for reconstruction despite the biprism-like effect, which we demonstrate on both, simulated and experimental examples.

  11. Electron Emitter for small-size Electrodynamic Space Tether using MEMS Technology

    DEFF Research Database (Denmark)

    Fleron, René A. W.; Blanke, Mogens

    2004-01-01

    system with focus on electron emitter design and manufacture using micro-electro-mechanical- system (MEMS) technology. The paper addresses the system concepts of a small size electrodynamic tether mission and shows a novel electron emitter for the 1-2 mA range where altitude can be effectively affected...

  12. Interactions between low energy electrons and DNA: a perspective from first-principles simulations

    Science.gov (United States)

    Kohanoff, Jorge; McAllister, Maeve; Tribello, Gareth A.; Gu, Bin

    2017-09-01

    DNA damage caused by irradiation has been studied for many decades. Such studies allow us to better assess the dangers posed by radiation, and to increase the efficiency of the radiotherapies that are used to combat cancer. A full description of the irradiation process involves multiple size and time scales. It starts with the interaction of radiation—either photons or swift ions—and the biological medium, which causes electronic excitation and ionisation. The two main products of ionising radiation are thus electrons and radicals. Both of these species can cause damage to biological molecules, in particular DNA. In the long run, this molecular level damage can prevent cells from replicating and can hence lead to cell death. For a long time it was assumed that the main actors in the damage process were the radicals. However, experiments in a seminal paper by the group of Leon Sanche in 2000 showed that low-energy electrons (LEE), such as those generated when ionising biological targets, can also cause bond breaks in biomolecules, and strand breaks in plasmid DNA in particular (Boudaiffa et al 2000 Science 287 1658-60). These results prompted a significant amount of experimental and theoretical work aimed at elucidating the role played by LEE in DNA damage. In this Topical Review we provide a general overview of the problem. We discuss experimental findings and theoretical results hand in hand with the aim of describing the physics and chemistry that occurs during the process of radiation damage, from the initial stages of electronic excitation, through the inelastic propagation of electrons in the medium, the interaction of electrons with DNA, and the chemical end-point effects on DNA. A very important aspect of this discussion is the consideration of a realistic, physiological environment. The role played by the aqueous solution and the amino acids from the histones in chromatin must be considered. Moreover, thermal fluctuations must be incorporated when

  13. Tunable graphene micro-emitters with fast temporal response and controllable electron emission.

    Science.gov (United States)

    Wu, Gongtao; Wei, Xianlong; Gao, Song; Chen, Qing; Peng, Lianmao

    2016-05-10

    Microfabricated electron emitters have been studied for half a century for their promising applications in vacuum electronics. However, tunable microfabricated electron emitters with fast temporal response and controllable electron emission still proves challenging. Here, we report the scaling down of thermionic emitters to the microscale using microfabrication technologies and a Joule-heated microscale graphene film as the filament. The emission current of the graphene micro-emitters exhibits a tunability of up to six orders by a modest gate voltage. A turn-on/off time of less than 1 μs is demonstrated for the graphene micro-emitters, indicating a switching speed about five orders of magnitude faster than their bulky counterparts. Importantly, emission performances of graphene micro-emitters are controllable and reproducible through engineering graphene dimensions by microfabrication technologies, which enables us to fabricate graphene micro-emitter arrays with uniform emission performances. Graphene micro-emitters offer an opportunity of realizing large-scale addressable micro-emitter arrays for vacuum electronics applications.

  14. On the origin of low-energy electrons in the inner magnetosphere: Fluxes and pitch-angle distributions

    Science.gov (United States)

    Denton, M. H.; Reeves, G. D.; Larsen, B. A.; Friedel, R. F. W.; Thomsen, M. F.; Fernandes, P. A.; Skoug, R. M.; Funsten, H. O.; Sarno-Smith, L. K.

    2017-02-01

    Accurate knowledge of the plasma fluxes in the inner magnetosphere is essential for both scientific and programmatic applications. Knowledge of the low-energy electrons (approximately tens to hundreds of eV) in the inner magnetosphere is particularly important since these electrons are acted upon by various physical processes, accelerating the electrons to higher energies, and also causing their loss. However, measurements of low-energy electrons are challenging, and as a result, this population has been somewhat neglected previously. This study concerns observations of low-energy electrons made by the Helium Oxygen Proton Electron instrument on board the Van Allen Probes satellites and also observations from geosynchronous orbit made by the Magnetospheric Plasma Analyzer on board Los Alamos National Laboratory satellites. The fluxes of electrons from 30 eV to 1 keV are quantified as a function of pitch-angle, McIlwain L parameter, and local time for both quiet and active periods. Results indicate two sources for low-energy electrons in this energy range: the low-energy tail of the electron plasma sheet and the high-energy tail of the dayside ionosphere. These populations are identified primarily as a result of their different pitch-angle distributions. Field-aligned outflows from the dayside ionosphere are observed at all L shells during quiet and active periods. Our results also demonstrate that the dayside electron field-aligned fluxes at 30 eV are particularly strong between L values of 6 and 7, indicating an enhanced source within the polar ionosphere.

  15. CMOS pixel sensor response to low energy electrons in transmission electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Battaglia, Marco [Department of Physics, University of California at Berkeley, CA 94720 (United States); Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)], E-mail: MBattaglia@lbl.gov; Contarato, Devis; Denes, Peter; Doering, Dionisio; Radmilovic, Velimir [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

    2009-07-01

    This letter presents the results of a study of the response of a test CMOS sensor with a radiation tolerant pixel cell design to 80 and 100 keV electrons. The point spread function is measured to be (13.0{+-}1.7){mu}m at 100 keV and (12.1{+-}1.6){mu}m at 80 keV, for 20{mu}m pixels. Results agree well with values predicted by a Geant-4 and dedicated charge collection simulation.

  16. Elastic scattering of low-energy electrons by 1,4-dioxane

    Energy Technology Data Exchange (ETDEWEB)

    Barbosa, Alessandra Souza; Bettega, Márcio H. F., E-mail: bettega@fisica.ufpr.br [Departamento de Física, Universidade Federal do Paraná, Caixa Postal 19044, 81531-990 Curitiba, Paraná (Brazil)

    2014-05-14

    We report calculated cross sections for elastic collisions of low-energy-electrons with 1,4-dioxane. Our calculations employed the Schwinger multichannel method with pseudopotentials and were carried out in the static-exchange and static-exchange plus polarization approximations for energies up to 30 eV. Our results show the presence of three shape resonances belonging to the B{sub u}, A{sub u}, and B{sub g} symmetries and located at 7.0 eV, 8.4 eV, and 9.8 eV, respectively. We also report the presence of a Ramsauer-Townsend minimum located at around 0.05 eV. We compare our calculated cross sections with experimental data and R-matrix and independent atom model along with the additivity rule corrected by using screening coefficients theoretical results for 1,4-dioxane obtained by Palihawadana et al. [J. Chem. Phys. 139, 014308 (2013)]. The agreement between the present and the R-matrix theoretical calculations of Palihawadana et al. is relatively good at energies below 10 eV. Our calculated differential cross sections agree well with the experimental data, showing only some discrepancies at higher energies.

  17. Low-Energy Electron Potentiometry: Contactless Imaging of Charge Transport on the Nanoscale.

    Science.gov (United States)

    Kautz, J; Jobst, J; Sorger, C; Tromp, R M; Weber, H B; van der Molen, S J

    2015-09-04

    Charge transport measurements form an essential tool in condensed matter physics. The usual approach is to contact a sample by two or four probes, measure the resistance and derive the resistivity, assuming homogeneity within the sample. A more thorough understanding, however, requires knowledge of local resistivity variations. Spatially resolved information is particularly important when studying novel materials like topological insulators, where the current is localized at the edges, or quasi-two-dimensional (2D) systems, where small-scale variations can determine global properties. Here, we demonstrate a new method to determine spatially-resolved voltage maps of current-carrying samples. This technique is based on low-energy electron microscopy (LEEM) and is therefore quick and non-invasive. It makes use of resonance-induced contrast, which strongly depends on the local potential. We demonstrate our method using single to triple layer graphene. However, it is straightforwardly extendable to other quasi-2D systems, most prominently to the upcoming class of layered van der Waals materials.

  18. Sub-micron alignment for nuclear emulsion plates using low energy electrons caused by radioactive isotopes

    Science.gov (United States)

    Miyamoto, S.; Ariga, A.; Fukuda, T.; Kazuyama, M.; Komatsu, M.; Nakano, T.; Niwa, K.; Sato, O.; Takahashi, S.

    2007-06-01

    Nuclear emulsion plates are employed in three-dimensional charged particle detectors that have sub-micron position resolution over 1 m2 with no dead space and no dead time. These detectors are suitable for the study of short-lived particle decays, and direct detection of neutrino interactions of all flavors. Typically emulsion plates are used in a stacked structure. Precise alignment between plates is required for physics analysis. The most accurate alignment method is to use tracks passing through the emulsion plates. The accuracy is about 0.2 μm. However, in an experiment with low track density alignment accuracy decreases to 20 μm because of plate distortion and it becomes more difficult to perform the analysis. This paper describes a new alignment method between emulsion plates by using trajectories of low energy electrons originating from environmental radioactive isotopes. As a trial emulsion plates were exposed to β-rays and γ-rays from K40. The trajectories which passed through emulsion layers were detected by a fully automated emulsion readout system. Using this method, the alignment between emulsion plates is demonstrated to be sub-micron. This method can be applied to many nuclear emulsion experiments. For example, the location of neutrino interaction vertices in the OPERA experiment can benefit from this new technique.

  19. Low-energy electron diffraction investigation of epitaxial growth: Pt and Pd on Pd(100)

    Energy Technology Data Exchange (ETDEWEB)

    Flynn-Sanders, D.

    1990-09-21

    We investigate the epitaxial growth of Pt and Pd and Pd(100) via spot profile analysis using conventional low-energy electron diffraction (LEED). We resolve a central-spike and diffuse component in the spot profiles, reflecting the layer-occupations and pair-correlations, respectively. Kinetic limitations inhibit layer-by-layer growth at low temperatures. Our data suggest diffusion switches on at ca. 150 K for Pt and ca. 170 K for Pd indicating activation barriers to surface diffusion of ca. 10 and ca. 13 kcal/mol, respectively. To clarify the role of diffusion in determining the resulting film morphology, we develop a growth model that incorporates the adsorption-site requirement and predicts intensity oscillations. We present a new procedure to experimentally determine out-of-phase scattering conditions. At these energies, ring-structure is evident in the profiles during Pd growth between ca. 200 and 400 K. We report ring intensity oscillations as a function of coverage, which demonstrate the filling of individual layers.

  20. Analysis of the low-energy electron-recoil spectrum of the CDMS experiment

    CERN Document Server

    Ahmed, Z; Arrenberg, S; Bailey, C N; Balakishiyeva, D; Baudis, L; Bauer, D A; Beaty, J; Brink, P L; Bruch, T; Bunker, R; Cabrera, B; Caldwell, D O; Cooley, J; Cushman, P; De Jongh, F; Dragowsky, M R; Duong, L; Figueroa-Feliciano, E; Filippini, J; Fritts, M; Golwala, S R; Grant, D R; Hall, J; Hennings-Yeomans, R; Hertel, S; Holmgren, D; Hsu, L; Huber, M E; Kamaev, O; Kiveni, M; Kos, M; Leman, S W; Mahapatra, R; Mandic, V; Moore, D; McCarthy, K A; Mirabolfathi, N; Nelson, H; Ogburn, R W; Pyle, M; Qiu, X; Ramberg, E; Rau, W; Reisetter, A; Saab, T; Sadoulet, B; Sander, J; Schnee, R W; Seitz, D N; Serfass, B; Sundqvist, K M; Wang, G; Yellin, S; Yoo, J; Young, B A

    2009-01-01

    We report on the analysis of the low-energy electron-recoil spectrum from the CDMS II experiment using data with an exposure of 443.2 kg-days. The analysis provides details on the observed counting rate and possible background sources in the energy range of 2 - 8.5 keV. We find no significant excess in the counting rate above background, and compare this observation to the recent DAMA results. In the framework of a conversion of a dark matter particle into electromagnetic energy, our 90% confidence level upper limit of 0.246 events/kg/day at 3.15 keV is lower than the total rate above background observed by DAMA by 8.9$\\sigma$. In absence of any specific particle physics model to provide the scaling in cross section between NaI and Ge, we assume a Z^2 scaling. With this assumption the observed rate in DAMA differs from the upper limit in CDMS by 6.8$\\sigma$. Under the conservative assumption that the modulation amplitude is 6% of the total rate we obtain upper limits on the modulation amplitude a factor of ~2...

  1. Low-energy electron diffraction study of rare gas adsorption on metal surfaces

    Science.gov (United States)

    Caragiu, Mellita

    2000-10-01

    The method of Low Energy Electron Diffraction (LEED) is applied to the study of rare gas - metal systems. The emphasis is on the adsorption site of the adatoms on the substrate, as a result of controversial opinions on this matter arising both from theoretical approaches and previous experimental data. Contrary to the expectations, it is found that rare gases prefer low coordination sites when adsorbed in commensurate phases for practically all studied structures: Cu111 -3x3 R30°-Xe, Pt111- 3x3 R30°-Xe, Pd111 -3x3 R30° -Xe, Ag111 -7x 7R19.1° -4Ar, Cu110 - 41 02 -5Kran dCu110 - 61 02 -7Xe. Possible explanations for the rare gas behavior on metal substrates are reviewed. Besides the crucial information of the rare gas adsorption site, the LEED analysis provides structural (geometrical) parameters for the systems under study and several non-structural ones (e.g. vibrations of the atoms and inner potential of the crystal).

  2. Low-Energy Electron Potentiometry: Contactless Imaging of Charge Transport on the Nanoscale

    Science.gov (United States)

    Kautz, J.; Jobst, J.; Sorger, C.; Tromp, R. M.; Weber, H. B.; van der Molen, S. J.

    2015-09-01

    Charge transport measurements form an essential tool in condensed matter physics. The usual approach is to contact a sample by two or four probes, measure the resistance and derive the resistivity, assuming homogeneity within the sample. A more thorough understanding, however, requires knowledge of local resistivity variations. Spatially resolved information is particularly important when studying novel materials like topological insulators, where the current is localized at the edges, or quasi-two-dimensional (2D) systems, where small-scale variations can determine global properties. Here, we demonstrate a new method to determine spatially-resolved voltage maps of current-carrying samples. This technique is based on low-energy electron microscopy (LEEM) and is therefore quick and non-invasive. It makes use of resonance-induced contrast, which strongly depends on the local potential. We demonstrate our method using single to triple layer graphene. However, it is straightforwardly extendable to other quasi-2D systems, most prominently to the upcoming class of layered van der Waals materials.

  3. Ion Emittance Growth Due to Focusing Modulation from Slipping Electron Bunch

    Energy Technology Data Exchange (ETDEWEB)

    Wang, G. [Brookhaven National Lab. (BNL), Upton, NY (United States). Collider-Accelerator Dept.

    2015-02-17

    Low energy RHIC operation has to be operated at an energy ranging from γ = 4.1 to γ = 10. The energy variation causes the change of revolution frequency. While the rf system for the circulating ion will operate at an exact harmonic of the revolution frequency (h=60 for 4.5 MHz rf and h=360 for 28 MHz rf.), the superconducting rf system for the cooling electron beam does not have a frequency tuning range that is wide enough to cover the required changes of revolution frequency. As a result, electron bunches will sit at different locations along the ion bunch from turn to turn, i.e. the slipping of the electron bunch with respect to the circulating ion bunch. At cooling section, ions see a coherent focusing force due to the electrons’ space charge, which differs from turn to turn due to the slipping. We will try to estimate how this irregular focusing affects the transverse emittance of the ion bunch.

  4. Nonlinear saturation of wave packets excited by low-energy electron horseshoe distributions.

    Science.gov (United States)

    Krafft, C; Volokitin, A

    2013-05-01

    Horseshoe distributions are shell-like particle distributions that can arise in space and laboratory plasmas when particle beams propagate into increasing magnetic fields. The present paper studies the stability and the dynamics of wave packets interacting resonantly with electrons presenting low-energy horseshoe or shell-type velocity distributions in a magnetized plasma. The linear instability growth rates are determined as a function of the ratio of the plasma to the cyclotron frequencies, of the velocity and the opening angle of the horseshoe, and of the relative thickness of the shell. The nonlinear stage of the instability is investigated numerically using a symplectic code based on a three-dimensional Hamiltonian model. Simulation results show that the dynamics of the system is mainly governed by wave-particle interactions at Landau and normal cyclotron resonances and that the high-order normal cyclotron resonances play an essential role. Specific features of the dynamics of particles interacting simultaneously with two or more waves at resonances of different natures and orders are discussed, showing that such complex processes determine the main characteristics of the wave spectrum's evolution. Simulations with wave packets presenting quasicontinuous spectra provide a full picture of the relaxation of the horseshoe distribution, revealing two main phases of the evolution: an initial stage of wave energy growth, characterized by a fast filling of the shell, and a second phase of slow damping of the wave energy, accompanied by final adjustments of the electron distribution. The influence of the density inhomogeneity along the horseshoe on the wave-particle dynamics is also discussed.

  5. Electron emission from MOS electron emitters with clean and cesium covered gold surface

    DEFF Research Database (Denmark)

    Nielsen, Gunver; Thomsen, Lasse Bjørchmar; Johansson, Martin;

    2009-01-01

    MOS (metal-oxide-semiconductor) electron emitters consisting of a Si substrate, a SiO2 tunnel barrier and a Ti (1 nm)/Au(7 nm) top-electrode, with an active area of 1 cm(2) have been produced and studied with surface science techniques under UHV (ultra high vacuum) conditions and their emission c...

  6. Emittance growth due to static and radiative space charge forces in an electron bunch compressor

    Science.gov (United States)

    Talman, Richard; Malitsky, Nikolay; Stulle, Frank

    2009-01-01

    -21, MOCOS05, available at http://www.JACoW.org], a code with similar capabilities. For this comparison an appropriately new, 50 MeV, “standard chicane” is introduced. Unlike CSRTrack (which neglects vertical forces) the present simulation shows substantial growth of vertical emittance. But “turning off” vertical forces in the UAL code (to match the CSRTrack treatment) brings the two codes into excellent agreement. (iii) Results are also obtained for 5 GeV electrons passing through a previously introduced “standard chicane” [Coherent Synchrotron Radiation, CSR Workshop, Berlin 2002, http://www.desy.de/csr] [of the sort needed for linear colliders and free electron lasers (FEL’s) currently under design or construction]. Relatively little emittance growth is predicted for typical bunch parameters at such high electron energy. Results are obtained for both round beams and ribbon beams (like those actually needed in practice). Little or no excess emittance growth is found for ribbon bunches compared to round bunches of the same charge and bunch width. The UAL string space charge formulation (like TraFic4 and CSRTrack) avoids the regularization step (subtracting the free-space space charge force) which is required (to remove divergence) in some methods. Also, by avoiding the need to calculate a retarded-time, four-dimensional field history, the computation time needed for realistic bunch evolution calculations is modest. Some theories of bunch dilution, because they ascribe emittance growth entirely to CSR, break down at low energy. In the present treatment, as well as CSR, all free-space Coulomb and magnetic space charge forces (but not image forces), and also the centrifugal space charge force (CSCF) are included. Charge-dependent beam steering due to CSCF, as observed recently by Beutner et al. [B. Beutner , in Proceedings of FEL Conference, BESSY, Berlin, Germany, 2006, MOPPH009], is also investigated.

  7. Low-energy electron-induced reactions in thin films of glucose and N-acetyl-glucosamine

    Science.gov (United States)

    Ryzhkova, A.; Swiderek, P.

    2011-05-01

    Reactions induced in thin films of α- D-glucose and N-acetylglucosamine by low-energy electron exposure at incident electron energies ( E0) between 5 eV and 15 eV have been investigated by high-resolution electron energy loss spectroscopy (HREELS). The reactions of α- D-glucose upon electron exposure were also studied in the presence of molecular oxygen. Electron exposure leads to characteristic changes of the vibrational spectra indicating that OH groups are lost with the formation of CC double bonds taking place preferentially above the ionisation threshold of the investigated molecules. At lower E0, OH groups are equally decomposed suggesting that dissociative electron attachment contributes to the reactions but formation of double bonds is not observed. The results show that different reaction channels are effective depending on E0 and that the outcome of electron-driven chemistry in saccharides may be controlled by changing from the subionisation regime to E0 above the ionisation threshold. Generally, low-energy electron exposure in the absence of O 2 produces a material with lower oxygen content, i.e. leads to a reduction of the saccharide. In the case of N-acetylglucosamine, removal of the amide group from the sugar is also important at subionisation energies. In contrast, as shown for α- D-glucose, low-energy electron exposure in the presence of O 2 leads to oxidation of the sugar even at cryogenic temperature.

  8. Structural biology at the single particle level: imaging tobacco mosaic virus by low-energy electron holography

    CERN Document Server

    Longchamp, Jean-Nicolas; Escher, Conrad; Fink, Hans-Werner

    2014-01-01

    Modern structural biology relies on NMR, X-ray crystallography and cryo-electron microscopy for gaining information on biomolecules at nanometer, sub-nanometer or atomic resolution. All these methods, however, require averaging over a vast ensemble of entities and hence knowledge on the conformational landscape of an individual particle is lost. Unfortunately, there are now strong indications that even X-ray free electron lasers will not be able to image individual molecules but will require nanocrystal samples. Here, we show that non-destructive structural biology of single particles has now become possible by means of low-energy electron holography. Individual tobacco mosaic viruses deposited on ultraclean freestanding graphene are imaged at one nanometer resolution revealing structural details arising from the helical arrangement of the outer protein shell of the virus. Since low-energy electron holography is a lens-less technique and since electrons with a deBroglie wavelength of approximately 1 Angstrom ...

  9. Elastic stability and electronic structure of low energy tetragonal and monoclinic PdN2 and PtN2

    Institute of Scientific and Technical Information of China (English)

    Zhao Wen-Jie; Wang Yuan-Xu

    2009-01-01

    This paper studies the elastic and electronic structure properties of two new low-energy structures of PdN2 and PtN2 by first-principles calculations. It finds that tetragonal and monoclinic structures are more stable than a pyrite one. The always positive eigenvalues of the elastic constant matrix confirm that both the tetragonal and monoclinic structures are elastically stable. The origin of the low bulk modulus of the two structures is discussed. The results of the calculated density of states show that both of the two low-energy structures are metallic.

  10. Magnetism of epitaxial Tb films on W(110) studied by spin-polarized low-energy electron microscopy

    Science.gov (United States)

    Prieto, J. E.; Chen, Gong; Schmid, A. K.; de la Figuera, J.

    2016-11-01

    Thin epitaxial films of Tb metal were grown on a clean W(110) substrate in ultrahigh vacuum and studied in situ by low-energy electron microscopy. Annealed films present magnetic contrast in spin-polarized low-energy electron microscopy. The energy dependence of the electron reflectivity was determined and a maximum value of its spin asymmetry of about 1% was measured. The magnetization direction of the Tb films is in-plane. Upon raising the temperature, no change in the domain distribution is observed, while the asymmetry in the electron reflectivity decreases when approaching the critical temperature, following a power law ˜(1-T /TC) β with a critical exponent β of 0.39.

  11. Generation of low-emittance electron beams in electrostatic accelerators for FEL applications

    Science.gov (United States)

    Teng, Chen; Elias, Luis R.

    1995-02-01

    This paper reports results of transverse emittance studies and beam propagation in electrostatic accelerators for free electron laser applications. In particular, we discuss emittance growth analysis of a low current electron beam system consisting of a miniature thermoionic electron gun and a National Electrostatics Accelerator (NEC) tube. The emittance growth phenomenon is discussed in terms of thermal effects in the electron gun cathode and aberrations produced by field gradient changes occurring inside the electron gun and throughout the accelerator tube. A method of reducing aberrations using a magnetic solenoidal field is described. Analysis of electron beam emittance was done with the EGUN code. Beam propagation along the accelerator tube was studied using a cylindrically symmetric beam envelope equation that included beam self-fields and the external accelerator fields which were derived from POISSON simulations.

  12. Damage induced to DNA by low-energy (0-30 eV) electrons under vacuum and atmospheric conditions.

    Science.gov (United States)

    Brun, Emilie; Cloutier, Pierre; Sicard-Roselli, Cécile; Fromm, Michel; Sanche, Léon

    2009-07-23

    In this study, we show that it is possible to obtain data on DNA damage induced by low-energy (0-30 eV) electrons under atmospheric conditions. Five monolayer films of plasmid DNA (3197 base pairs) deposited on glass and gold substrates are irradiated with 1.5 keV X-rays in ultrahigh vacuum and under atmospheric conditions. The total damage is analyzed by agarose gel electrophoresis. The damage produced on the glass substrate is attributed to energy absorption from X-rays, whereas that produced on the gold substrate arises from energy absorption from both the X-ray beam and secondary electrons emitted from the gold surface. By analysis of the energy of these secondary electrons, 96% are found to have energies below 30 eV with a distribution peaking at 1.4 eV. The differences in damage yields recorded with the gold and glass substrates is therefore essentially attributed to the interaction of low-energy electrons with DNA under vacuum and hydrated conditions. From these results, the G values for low-energy electrons are determined to be four and six strand breaks per 100 eV, respectively.

  13. Carbon Nanotube Electron Emitter for X-ray Imaging

    Directory of Open Access Journals (Sweden)

    Jung Su Kang

    2012-11-01

    Full Text Available The carbon nanotube field emitter array was grown on silicon substrate through a resist-assisted patterning (RAP process. The shape of the carbon nanotube array is elliptical with 2.0 × 0.5 mm2 for an isotropic focal spot size at anode target. The field emission properties with triode electrodes show a gate turn-on field of 3 V/µm at an anode emission current of 0.1 mA. The author demonstrated the X-ray source with triode electrode structure utilizing the carbon nanotube emitter, and the transmitted X-ray image was of high resolution.

  14. Characterizing and Optimizing Photocathode Laser Distributions for Ultra-low Emittance Electron Beam Operations

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, F. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Bohler, D. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Ding, Y. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Gilevich, S. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Huang, Z. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Loos, H. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Ratner, D. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Vetter, S. [SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2015-12-07

    Photocathode RF gun has been widely used for generation of high-brightness electron beams for many different applications. We found that the drive laser distributions in such RF guns play important roles in minimizing the electron beam emittance. Characterizing the laser distributions with measurable parameters and optimizing beam emittance versus the laser distribution parameters in both spatial and temporal directions are highly desired for high-brightness electron beam operation. In this paper, we report systematic measurements and simulations of emittance dependence on the measurable parameters represented for spatial and temporal laser distributions at the photocathode RF gun systems of Linac Coherent Light Source. The tolerable parameter ranges for photocathode drive laser distributions in both directions are presented for ultra-low emittance beam operations.

  15. The Role of Low-Energy (less than 20 eV) Electrons in Astrochemistry: A Tale of Two Molecules

    Science.gov (United States)

    Arumainayagam, Chris

    2016-07-01

    In the interstellar medium, UV photolysis of ice mantles encasing dust grains is thought to be the mechanism that drives the synthesis of "complex" molecules. The source of this reaction-initiating UV light is assumed to be local because externally-sourced UV radiation cannot pass through the ice-containing dark, dense molecular clouds. Externally sourced cosmic rays (E_{max} ˜10^{20} eV), in addition to producing UV light within these clouds, also produce large numbers of low-energy (≤ 20 eV) secondary electrons. The goal of our studies is to understand the low-energy electron-induced processes that occur when high-energy cosmic rays interact with interstellar ices. Using electron stimulated desorption (ESD), post-irradiation temperature-programmed desorption (TPD), and infrared reflection absorption spectroscopy (IRAS), we have investigated the radiolysis initiated by electrons in condensed methanol and ammonia at ˜90K under ultrahigh vacuum (1 × 10^{-9} Torr) conditions. We have identified fifteen low-energy electron-induced methanol radiolysis products, many of which have been previously identified as being formed by methanol UV photolysis in the interstellar medium. We have also found evidence for the electron-induced formation from ammonia of hydrazine (N_2 H_4), diazene (N_2 H_2), cyclotriazane/triazene (N_3 H_3) and triazane (N_3 H_5). We have investigated the reaction yields' dependence on film thickness, irradiation time, incident current, electron energy, and metal substrate. These results provide a basis from which we can begin to understand the mechanisms by which methanol and ammonia can form more complex species in cosmic ices. Studies such as ours may ultimately help us better understand the initial stages of the genesis of life.

  16. Effects of base resistor on electron emission from a field emitter

    Energy Technology Data Exchange (ETDEWEB)

    Luginsland, J.W.; Valfells, A.; Lau, Y.Y. [Univ. of Michigan, Ann Arbor, MI (United States)

    1996-12-31

    Field emitters have remained an important, high brightness electron source for display and for generation of coherent radiation. The rapid rise in the emitter current with voltage in these emitters leads to serious implications on the emitter stability (thermal, mechanical, and electrical), and an obvious way to improve the emitter stability is to add a series resistor to the emitters. However, the addition of a series resistor would result in a higher operating voltage, loss in efficiency, and much higher cost. In this paper, the authors use a simple model to provide a quantitative analysis of the effects of a base resistor on the voltage-current (V-I) characteristics of a single field emitter. Two features of the present work are noteworthy. First, they present a set of universal curves, from which the effects of a series resistor can immediately be determined once the Fowler-Nordheim coefficients A, B, and the gap spacing D are specified. Thus, these curves are applicable to a large class of field emitters. Second, the calculations take into account the effects of space charge that is present in the gap. The relative importance of the space charge and of the series resistor will become apparent from these curves. Examples will be given.

  17. A low energy electron microscopy study of the initial growth, structure and thermal stability of BDA-domains on Cu(001)

    NARCIS (Netherlands)

    Khokhar, F.S.; van Gastel, Raoul; Schwarz, Daniel; Schwarz, Daniel; Zandvliet, Henricus J.W.; Poelsema, Bene

    2011-01-01

    The growth of 4,4′-biphenyldicarboxylic acid (BDA) on Cu(001) has been studied using low energy electron microscopy and selective area low energy electron diffraction. The emergence of large islands and hydrogen bonding to perpendicularly oriented, adjacent molecules is confirmed. The two benzene

  18. Surface structure determinations of crystalline ionic thin films grown on transition metal single crystal surfaces by low energy electron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, Joel Glenn [Univ. of California, Berkeley, CA (United States)

    2000-05-01

    The surface structures of NaCl(100), LiF(100) and alpha-MgCl2(0001) adsorbed on various metal single crystals have been determined by low energy electron diffraction (LEED). Thin films of these salts were grown on metal substrates by exposing the heated metal surface to a molecular flux of salt emitted from a Knudsen cell. This method of investigating thin films of insulators (ionic salts) on a conducting substrate (metal) circumvents surface charging problems that plagued bulk studies, thereby allowing the use of electron-based techniques to characterize the surface.

  19. Ionization Cluster Size Distributions Created by Low Energy Electrons and Alpha Particles in Nanometric Track Segment in Gases

    CERN Document Server

    Bantsar, Aliaksandr

    2012-01-01

    The interaction of ionizing radiation with nanometric targets is a field of interest for many branches of science such as: radiology, oncology, radiation protection and nanoelectronics. A new experimental technique known as nanodosimetry has been developed for the qualitative as well as quantitative description of these types of interactions. The work presented here is a contribution to this development, namely by further improvement of the new experimental technique called the Jet Counter, originally developed at the Andrzej So{\\l}tan Institute for Nuclear Studies. The Jet Counter is a unique device in the world for studying the interaction of low energy electrons with nanometer targets in the range 2-10 nm (in unit density). The basic experimental result is the frequency distribution of ionization cluster size produced by ionizing particles in a gaseous (nitrogen or propane) nanometric track segment. The first experimental data on the frequency distribution of ionization cluster size produced by low energy ...

  20. Single shot 3 GeV electron transverse emittance with a pepper-pot

    Science.gov (United States)

    Thomas, Cyrille; Delerue, Nicolas; Bartolini, Riccardo

    2013-11-01

    We present the first measurement of the transverse emittance of an electron bunch at 3 GeV using the pepper-pot technique. The measurements presented in this paper demonstrate the possibility to use such a method for single shot emittance measurement of high energy particles. This measurement presents also the experimental verification of a previous theoretical study, which was predicting in which condition such a measurement can be done. The method may present some technical limitations which are discussed in view of the application to future very small emittance multi-GeV particle accelerators.

  1. Emittance studies at the Los Alamos National Laboratory Free-Electron Laser (FEL)

    Science.gov (United States)

    Carlsten, B. E.; Feldman, D. W.; Lumpkin, A. H.; Stein, W. E.; Warren, R. W.

    Recent emittance studies at the Los Alamos Free-Electron Laser (FEL) have indicated several areas of concern in the linac and beamline feeding the wiggler. Four emittance growth mechanisms of special importance have been studied. First, a rapid growth of the electron beam's emittance immediately after the spherical gridded Pierce gun resulted, in part, from the long time required for our pulsing electronics to ramp the grid voltage up at the start and down at the end of the pulse, which created a pulse with a cosine-like current distribution as a function of time. The growth was compounded by the extremely small radial beam size (almost a waist) leaving the gun. In addition, we saw evidence of electrostatic charging of the insulators in the gun, reducing the quality of the electron beam further. Second, the action of the solenoidal focusing fields in the low-voltage bunching region was studied, and criteria for a minimum emittance growth were established. Third, maximum misalignment angles and displacements for various elements of the beamline were calculated for the desired low emittance growth. Finally, emittance growth in the horizontal dimension through the nonisochronous bend caused by varying energy depression on the particles due to longitudinal wake fields was both calculated and observed. In addition, we measured energy depressions caused by the wake fields generated by various other elements in the beamline. Strategies were developed to relieve the magnitude of these wake-field effects.

  2. A method for extraction of crystallography-related information from a data cube of very-low-energy electron micrographs

    Energy Technology Data Exchange (ETDEWEB)

    Knápek, Alexandr, E-mail: knapek@isibrno.cz; Pokorná, Zuzana

    2015-01-15

    Scanning Low Energy Electron Microscopy (SLEEM) is an imaging technique which uses low energy electrons while providing a very good image resolution. Reflectivity of very slow electrons in the range 0–30 eV can be correlated with the electronic structure of the material, aiming at the determination of the local crystallographic orientation. Since SLEEM is a 2D imaging method, a suitable algorithm is needed to pre-process the image data depending on the beam energy as the third dimension. The crucial task is to detect grain boundaries in polycrystals and evaluate the image signal in connection to the energy of electron impact. Recent algorithms performing the task for the traditional EBSD method are not suitable as they do not address the side-effects of the SLEEM technique. We propose a method that detects the grain boundaries while correcting for image distortion caused by the variation of cathode lens strength, and for several other issues. - Highlights: • Polished polycrystalline copper samples were in situ cleaned in UHV conditions. • A series of SLEEM images was taken at energies 0–30 eV with a step of 0.3 eV. • We developed a fully automated computer method for grain recognition. • Method was adapted to compensate for artefacts inherent to SLEEM. • Method yields grain boundaries and reflectivity curves of each grain.

  3. SU-E-T-489: Quantum versus Classical Trajectory Monte Carlo Simulations of Low Energy Electron Transport.

    Science.gov (United States)

    Thomson, R; Kawrakow, I

    2012-06-01

    Widely-used classical trajectory Monte Carlo simulations of low energy electron transport neglect the quantum nature of electrons; however, at sub-1 keV energies quantum effects have the potential to become significant. This work compares quantum and classical simulations within a simplified model of electron transport in water. Electron transport is modeled in water droplets using quantum mechanical (QM) and classical trajectory Monte Carlo (MC) methods. Water droplets are modeled as collections of point scatterers representing water molecules from which electrons may be isotropically scattered. The role of inelastic scattering is investigated by introducing absorption. QM calculations involve numerically solving a system of coupled equations for the electron wavefield incident on each scatterer. A minimum distance between scatterers is introduced to approximate structured water. The average QM water droplet incoherent cross section is compared with the MC cross section; a relative error (RE) on the MC results is computed. RE varies with electron energy, average and minimum distances between scatterers, and scattering amplitude. The mean free path is generally the relevant length scale for estimating RE. The introduction of a minimum distance between scatterers increases RE substantially (factors of 5 to 10), suggesting that the structure of water must be modeled for accurate simulations. Inelastic scattering does not improve agreement between QM and MC simulations: for the same magnitude of elastic scattering, the introduction of inelastic scattering increases RE. Droplet cross sections are sensitive to droplet size and shape; considerable variations in RE are observed with changing droplet size and shape. At sub-1 keV energies, quantum effects may become non-negligible for electron transport in condensed media. Electron transport is strongly affected by the structure of the medium. Inelastic scatter does not improve agreement between QM and MC simulations of low

  4. P13, the EMBL macromolecular crystallography beamline at the low-emittance PETRA III ring for high- and low-energy phasing with variable beam focusing

    Science.gov (United States)

    Cianci, Michele; Bourenkov, Gleb; Pompidor, Guillaume; Karpics, Ivars; Kallio, Johanna; Bento, Isabel; Roessle, Manfred; Cipriani, Florent; Fiedler, Stefan; Schneider, Thomas R.

    2017-01-01

    The macromolecular crystallography P13 beamline is part of the European Molecular Biology Laboratory Integrated Facility for Structural Biology at PETRA III (DESY, Hamburg, Germany) and has been in user operation since mid-2013. P13 is tunable across the energy range from 4 to 17.5 keV to support crystallographic data acquisition exploiting a wide range of elemental absorption edges for experimental phase determination. An adaptive Kirk­patrick–Baez focusing system provides an X-ray beam with a high photon flux and tunable focus size to adapt to diverse experimental situations. Data collections at energies as low as 4 keV (λ = 3.1 Å) are possible due to a beamline design minimizing background and maximizing photon flux particularly at low energy (up to 1011 photons s−1 at 4 keV), a custom calibration of the PILATUS 6M-F detector for use at low energies, and the availability of a helium path. At high energies, the high photon flux (5.4 × 1011 photons s−1 at 17.5 keV) combined with a large area detector mounted on a 2θ arm allows data collection to sub-atomic resolution (0.55 Å). A peak flux of about 8.0 × 1012 photons s−1 is reached at 11 keV. Automated sample mounting is available by means of the robotic sample changer ‘MARVIN’ with a dewar capacity of 160 samples. In close proximity to the beamline, laboratories have been set up for sample preparation and characterization; a laboratory specifically equipped for on-site heavy atom derivatization with a library of more than 150 compounds is available to beamline users. PMID:28009574

  5. Multislit-Based Emittance Measurement of Electron Beam from a Photocathode Radio-Frequency Gun

    Institute of Scientific and Technical Information of China (English)

    YAN Li-Xin; DU Ying-Chao; XIANG Dao; LI Ren-Kai; QIAN Hou-Jun; HUANG Wen-Hui; TANG Chuan-Xiang; LIN Yu-Zheng; CHENG Jian-Ping

    2008-01-01

    Measurement of emittance for a space-charge dominated electron beam from a photocathode rf gun is performed by employing the multislit-based method at Accelerator Laboratory of Tsinghua University.We present the design considerations on the multislit system and the experimental results,with special attention to the study of space charge induced emittance growth.The experimental results are in reasonable agreement with the PARMELA simulations.

  6. A Low-Energy-Spread Rf Accelerator for a Far-Infrared Free-Electron Laser

    NARCIS (Netherlands)

    van der Geer, C. A. J.; Bakker, R. J.; van der Meer, A. F. G.; van Amersfoort, P. W.; Gillespie, W. A.; Saxon, G.; Poole, M. W.

    1993-01-01

    A high electron current and a small energy spread are essential for the operation of a free electron laser (FEL). In this paper we discuss the design and performance of the accelerator for FELIX, the free electron laser for infrared experiments. The system consists of a thermionic gun, a prebuncher,

  7. Holography and coherent diffraction with low-energy electrons: A route towards structural biology at the single molecule level

    Energy Technology Data Exchange (ETDEWEB)

    Latychevskaia, Tatiana; Longchamp, Jean-Nicolas; Escher, Conrad; Fink, Hans-Werner, E-mail: hwfink@physik.uzh.ch

    2015-12-15

    The current state of the art in structural biology is led by NMR, X-ray crystallography and TEM investigations. These powerful tools however all rely on averaging over a large ensemble of molecules. Here, we present an alternative concept aiming at structural analysis at the single molecule level. We show that by combining electron holography and coherent diffraction imaging estimations concerning the phase of the scattered wave become needless as the phase information is extracted from the data directly and unambiguously. Performed with low-energy electrons the resolution of this lens-less microscope is just limited by the De Broglie wavelength of the electron wave and the numerical aperture, given by detector geometry. In imaging freestanding graphene, a resolution of 2 Å has been achieved revealing the 660.000 unit cells of the graphene sheet from a single data set. Once applied to individual biomolecules the method shall ultimately allow for non-destructive imaging and imports the potential to distinguish between different conformations of proteins with atomic resolution. - Highlights: • Structural biology of single proteins. • Radiation damage-free imaging of individual biomolecules. • Holography. • Low-energy electrons. • Coherent diffraction and phase retrieval.

  8. Theorectical Studies of Excitation in Low-Energy Electron-Polyatomic Molecule Collisions

    Energy Technology Data Exchange (ETDEWEB)

    Rescigno, T N; McCurdy, C W; Isaacs, W A; Orel, A E; Meyer, H D

    2001-08-13

    This paper focuses on the channeling of energy from electronic to nuclear degrees of freedom in electron-polyatomic molecule collisions. We examine the feasibility of attacking the full scattering problem, both the fixed-nuclei electronic problem and the post-collision nuclear dynamics, entirely from first principles. The electron-CO{sub 2} system is presented as an example. We study resonant vibrational excitation, showing how a6 initio, fixed-nuclei electronic cross sections can provide the necessary input for a multi-dimensional treatment of the nuclear vibrational dynamics.

  9. Intersection of low-energy electron-atom scattering and photodetachment of negative ions

    CERN Document Server

    Felfli, Zineb

    2014-01-01

    We propose to use the near-threshold electron scattering data for atoms to guide the reliable experimental determination of their electron affinities (EAs), extracted using the Wigner Threshold Law, from laser photodetachment threshold spectroscopy measurements. Data from the near-threshold electron elastic scattering from W, Te, Rh, Sb and Sn atoms calculated using our complex angular momentum method, wherein is embedded the electron-electron correlations and core polarization interaction, are used as illustrations. We conclude with a remark on the relativistic effects on the EA calculation for the heavy At atom.

  10. Simulation of electron beam formation and transport in a gas-filled electron-optical system with a plasma emitter

    Science.gov (United States)

    Grishkov, A. A.; Kornilov, S. Yu.; Rempe, N. G.; Shidlovskiy, S. V.; Shklyaev, V. A.

    2016-07-01

    The results of computer simulations of the electron-optical system of an electron gun with a plasma emitter are presented. The simulations are performed using the KOBRA3-INP, XOOPIC, and ANSYS codes. The results describe the electron beam formation and transport. The electron trajectories are analyzed. The mechanisms of gas influence on the energy inhomogeneity of the beam and its current in the regions of beam primary formation, acceleration, and transport are described. Recommendations for optimizing the electron-optical system with a plasma emitter are presented.

  11. Simulation of electron beam formation and transport in a gas-filled electron-optical system with a plasma emitter

    Energy Technology Data Exchange (ETDEWEB)

    Grishkov, A. A. [Russian Academy of Sciences, Institute of High Current Electronics, Siberian Branch (Russian Federation); Kornilov, S. Yu., E-mail: kornilovsy@gmail.com; Rempe, N. G. [Tomsk State University of Control Systems and Radioelectronics (Russian Federation); Shidlovskiy, S. V. [Tomsk State University (Russian Federation); Shklyaev, V. A. [Russian Academy of Sciences, Institute of High Current Electronics, Siberian Branch (Russian Federation)

    2016-07-15

    The results of computer simulations of the electron-optical system of an electron gun with a plasma emitter are presented. The simulations are performed using the KOBRA3-INP, XOOPIC, and ANSYS codes. The results describe the electron beam formation and transport. The electron trajectories are analyzed. The mechanisms of gas influence on the energy inhomogeneity of the beam and its current in the regions of beam primary formation, acceleration, and transport are described. Recommendations for optimizing the electron-optical system with a plasma emitter are presented.

  12. First observation of low energy electron neutrinos in a liquid argon time projection chamber

    Energy Technology Data Exchange (ETDEWEB)

    Acciarri, R.; Adams, C.; Asaadi, J.; Baller, B.; Bolton, T.; Bromberg, C.; Cavanna, F.; Church, E.; Edmunds, D.; Ereditato, A.; Farooq, S.; Fitzpatrick, R. S.; Fleming, B.; Hackenburg, A.; Horton-Smith, G.; James, C.; Lang, K.; Luo, X.; Mehdiyev, R.; Page, B.; Palamara, O.; Rebel, B.; Schukraft, A.; Scanavini, G.; Soderberg, M.; Spitz, J.; Szelc, A. M.; Weber, M.; Yang, T.; Zeller, G. P.

    2017-04-01

    The capabilities of liquid argon time projection chambers (LArTPCs) to reconstruct the spatial and calorimetric information of neutrino events have made them the detectors of choice in a number of experiments, specically those looking to observe electron neutrino (e) appearance. The LArTPC promises excellent background rejection capabilities, especially in this \\golden" channel for both short and long baseline neutrino oscillation experiments. We present the rst experimental observation of electron neutrinos and anti-neutrinos in the ArgoNeut LArTPC, in the energy range relevant to DUNE and the Fermilab Short Baseline Neutrino Program. We have selected 37 electron candidate events and 274 gamma candidate events, and measured an 80% purity of electrons based on a topological selection. Additionally, we present a of separation of electrons from gammas using calorimetric energy deposition, demonstrating further separation of electrons from background gammas.

  13. Oxygen Attachment on Alkanethiolate SAMs Induced by Low-Energy Electron Irradiation

    Science.gov (United States)

    Massey, Sylvain; Bass, Andrew D.; Steffenhagen, Marie; Sanche, Léon

    2013-01-01

    Reactions of 18O2 with self-assembled monolayer (SAM) films of 1-dodecanethiol, 1-octadecanethiol, 1-butanethiol, and benzyl mercaptan chemisorbed on gold, were studied by the electron stimulated desorption (ESD) of anionic fragments over the incident electron energy range 2–20 eV. Dosing the SAMs with 18O2 at 50 K, results in the ESD of 18O− and 18OH−. Electron irradiation of samples prior to 18O2 deposition demonstrates that intensity of subsequent 18O− and 18OH− desorption signals increase with electron fluence and that absent electron pre-irradiation, no 18O− and 18OH− ESD signals are observed, since oxygen is unable to bind to the SAMs. A minimum incident electron energy of 6–7 eV is required to initiate the binding of 18O2 to the SAMs. O2 binding is proposed to proceed by the formation of CHx−1• radicals via resonant dissociative electron attachment and non-resonant C–H dissociation processes. The weaker signals of 18O− and 18OH− from short-chain SAMs are related to the latter’s resistance to electron induced damage, due to the charge-image dipole quenching and electron delocalization. Comparison between the present results and those for DNA oligonucleotides self-assembled on Au [Mirsaleh-Kohan, N. et al. J. Chem. Phys. 2012, 136, 235104] indicates that the oxygen binding mechanism is common to both systems. PMID:23537075

  14. Device with foil corrector for electron optical aberrations at low energy

    NARCIS (Netherlands)

    Kruit, P.; Van Aken, R.H.

    2004-01-01

    An electron optical device for, in use, creating negative spherical and chromatic aberration and reducing the energy spread in an electron beam travelling on an optical axis, including: at least one conducting plate substantially perpendicular to the optical axis with a first aperture having a first

  15. Device with foil corrector for electron optical aberrations at low energy

    NARCIS (Netherlands)

    Kruit, P.; Van Aken, R.H.

    2004-01-01

    An electron optical device for, in use, creating negative spherical and chromatic aberration and reducing the energy spread in an electron beam travelling on an optical axis, including: at least one conducting plate substantially perpendicular to the optical axis with a first aperture having a first

  16. Nanocrystal ghosting: Extensive radiation damage in MgO induced by low-energy electrons

    Science.gov (United States)

    Frankenfield, Zackery; Kane, Kenneth; Sawyer, William H.

    2017-03-01

    We report direct evidence of extensive radiation damage in MgO nanocrystals due to intense bombardment (2 × 10 electrons/nm sec) by electrons with beam energies between 60 keV and 120 keV. Based upon a minimum intensity necessary to produce the observed damage, we present an explanation based on the Knotek-Feibelman process.

  17. Contact Resistance and Channel Conductance of Graphene Field-Effect Transistors under Low-Energy Electron Irradiation

    Directory of Open Access Journals (Sweden)

    Filippo Giubileo

    2016-11-01

    Full Text Available We studied the effects of low-energy electron beam irradiation up to 10 keV on graphene-based field effect transistors. We fabricated metallic bilayer electrodes to contact mono- and bi-layer graphene flakes on SiO2, obtaining specific contact resistivity ρ c ≈ 19 k Ω · µ m 2 and carrier mobility as high as 4000 cm2·V−1·s−1. By using a highly doped p-Si/SiO2 substrate as the back gate, we analyzed the transport properties of the device and the dependence on the pressure and on the electron bombardment. We demonstrate herein that low energy irradiation is detrimental to the transistor current capability, resulting in an increase in contact resistance and a reduction in carrier mobility, even at electron doses as low as 30 e−/nm2. We also show that irradiated devices recover their pristine state after few repeated electrical measurements.

  18. Suprathermal plasma analyzer for the measurement of low-energy electron distribution in the ionosphere.

    Science.gov (United States)

    Shimoyama, M; Oyama, K-I; Abe, T; Yau, A W

    2011-07-01

    It is commonly believed that an energy transfer from thermal to suprathermal electrons (thermal to suprathermal energy continuously with high-energy resolution of about 0.15 eV. The measurement principle is based on the combination of a retarding potential analyzer with a channel electron multiplier (CEM) and the Druyvesteyn method, which derives energy distribution from the current-voltage characteristics. The capability of detecting plasma space potential enables absolute calibration of electron energy. The instrument with a small vacuum pump, which is required for the CEM to work in low-vacuum region, was first successfully tested by a sounding rocket S-310-37 in the ionospheric E region. The instrument is expected to provide new opportunities to measure energy distribution of thermal and non-thermal electrons in low-density plasma, where a Langmuir probe cannot measure electron temperature because of low plasma density.

  19. Coincident Auger electron and recoil ion momentum spectroscopy for low-energy ion-atom collisions

    Energy Technology Data Exchange (ETDEWEB)

    Laurent, G. E-mail: glaurent@ganil.fr; Tarisien, M.; Flechard, X.; Jardin, P.; Guillaume, L.; Sobocinski, P.; Adoui, L.; Bordenave-Montesquieu, A.; Bordenave-Montesquieu, D.; Chesnel, J.-Y.; Fremont, F.; Hennecart, D.; Lienard, E.; Maunoury, L.; Moretto-Capelle, P.; Cassimi, A

    2003-05-01

    The recoil ion momentum spectroscopy (RIMS) method combined with the detection of Auger electrons has been used successfully to analyse double electron capture following O{sup 6+} + He collisions at low impact velocities. Although RIMS and Auger spectroscopies are known to be efficient tools to obtain details on the primary processes occurring during the collision, the conjunction of both techniques provides new insights on the electron capture process. In the present experiment, triple coincidence detection of the scattered projectile, the target recoil ion and the Auger electron allows for a precise identification of the doubly excited states O{sup 4+} (1s{sup 2}nln{sup '}l{sup '}) populated after double electron-capture events.

  20. Imperative function of electron beams in low-energy plasma focus device

    Indian Academy of Sciences (India)

    M Z Khan; L K Lim; S L Yap; C S Wong

    2015-12-01

    A 2.2 kJ plasma focus device was analysed as an electron beam and an X-ray source that operates with argon gas refilled at a specific pressure. Time-resolved X-ray signals were observed using an array of PIN diode detectors, and the electron beam energy was detected using a scintillator-assisted photomultiplier tube. The resultant X-rays were investigated by plasma focus discharge for pressures ranging from 1.5 mbar to 2.0 mbar. This range corresponded to the significant values of X-ray yields and electron beam energies from the argon plasma. The electron temperature of argon plasma at an optimum pressure range was achieved by an indirect method using five-channel BPX65 PIN diodes of aluminum foils with different thicknesses. X-ray yield, electron beam energy, and electron temperature of argon plasma were achieved at 1.5–2.0 mbar because of the strong bombardment of the energetic electron beam.

  1. Simple polynomial approximation to modified Bethe formula low-energy electron stopping powers data

    Energy Technology Data Exchange (ETDEWEB)

    Taborda, A., E-mail: ana.taborda@irsn.fr [Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PRP-HOM/SDI/LEDI, BP-17, 92262 Fontenay-aux-Roses (France); Desbrée, A. [Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PRP-HOM/SDI/LEDI, BP-17, 92262 Fontenay-aux-Roses (France); Reis, M.A. [C" 2TN, Campus Tecnológico e Nuclear, Instituto Superior Técnico, Universidade de Lisboa, EN10 km139.7, 2685-066 Bobadela LRS (Portugal)

    2015-08-01

    A recently published detailed and exhaustive paper on cross-sections for ionisation induced by keV electrons clearly shows that electron phenomena occurring in parallel with X-ray processes may have been dramatically overlooked for many years, mainly when low atomic number species are involved since, in these cases, the fluorescence coefficient is smaller than the Auger yield. An immediate problem is encountered while attempting to tackle the issue. Accounting for electron phenomena requires the knowledge of the stopping power of electrons within, at least, a reasonably small error. Still, the Bethe formula for stopping powers is known to not be valid for electron energies below 30 keV, and its use leads to values far off experimental ones. Recently, a few authors have addressed this problem and both detailed tables of electron stopping powers for various atomic species and attempts to simplify the calculations, have emerged. Nevertheless, its implementation in software routines to efficiently calculate keV electron effects in materials quickly becomes a bit cumbersome. Following a procedure already used to establish efficient methods to calculate ionisation cross-sections by protons and alpha particles, it became clear that a simple polynomial approximation could be set, which allows retrieving the electronic stopping powers with errors of less than 20% for energies above 500 eV and less than 50% for energies between 50 eV and 500 eV. In this work, we present this approximation which, based on just six parameters, allows to recover electron stopping power values that are less than 20% different from recently published experimentally validated tabulated data.

  2. Carbon Nanotube Electron Emitter for X-ray Imaging

    OpenAIRE

    Jung Su Kang; Je Hwang Ryu; Kyu Chang Park

    2012-01-01

    The carbon nanotube field emitter array was grown on silicon substrate through a resist-assisted patterning (RAP) process. The shape of the carbon nanotube array is elliptical with 2.0 × 0.5 mm2 for an isotropic focal spot size at anode target. The field emission properties with triode electrodes show a gate turn-on field of 3 V/µm at an anode emission current of 0.1 mA. The author demonstrated the X-ray source with triode electrode structure utilizing the carbon nanotube em...

  3. Emittance growth due to static and radiative space charge forces in an electron bunch compressor

    Directory of Open Access Journals (Sweden)

    Richard Talman

    2009-01-01

    2004 FEL Conference, pp. 18–21, MOCOS05, available at http://www.JACoW.org], a code with similar capabilities. For this comparison an appropriately new, 50 MeV, “standard chicane” is introduced. Unlike CSRTrack (which neglects vertical forces the present simulation shows substantial growth of vertical emittance. But “turning off” vertical forces in the UAL code (to match the CSRTrack treatment brings the two codes into excellent agreement. (iii Results are also obtained for 5 GeV electrons passing through a previously introduced “standard chicane” [Coherent Synchrotron Radiation, CSR Workshop, Berlin 2002, http://www.desy.de/csr] [of the sort needed for linear colliders and free electron lasers (FEL’s currently under design or construction]. Relatively little emittance growth is predicted for typical bunch parameters at such high electron energy. Results are obtained for both round beams and ribbon beams (like those actually needed in practice. Little or no excess emittance growth is found for ribbon bunches compared to round bunches of the same charge and bunch width. The UAL string space charge formulation (like TraFic4 and CSRTrack avoids the regularization step (subtracting the free-space space charge force which is required (to remove divergence in some methods. Also, by avoiding the need to calculate a retarded-time, four-dimensional field history, the computation time needed for realistic bunch evolution calculations is modest. Some theories of bunch dilution, because they ascribe emittance growth entirely to CSR, break down at low energy. In the present treatment, as well as CSR, all free-space Coulomb and magnetic space charge forces (but not image forces, and also the centrifugal space charge force (CSCF are included. Charge-dependent beam steering due to CSCF, as observed recently by Beutner et al. [B. Beutner et al., in Proceedings of FEL Conference, BESSY, Berlin, Germany, 2006, MOPPH009], is also investigated.

  4. Oxygen Attachment on Alkanethiolate SAMs Induced by Low-Energy Electron Irradiation

    OpenAIRE

    Massey, Sylvain; Bass, Andrew D.; Steffenhagen, Marie; Sanche, Léon

    2013-01-01

    Reactions of 18O2 with self-assembled monolayer (SAM) films of 1-dodecanethiol, 1-octadecanethiol, 1-butanethiol, and benzyl mercaptan chemisorbed on gold, were studied by the electron stimulated desorption (ESD) of anionic fragments over the incident electron energy range 2–20 eV. Dosing the SAMs with 18O2 at 50 K, results in the ESD of 18O− and 18OH−. Electron irradiation of samples prior to 18O2 deposition demonstrates that intensity of subsequent 18O− and 18OH− desorption signals increase...

  5. Calculated low-energy electron-impact vibrational excitation cross sections for CO2 molecule

    CERN Document Server

    Laporta, V; Celiberto, R

    2016-01-01

    Vibrational-excitation cross sections of ground electronic state of carbon dioxide molecule by electron-impact through the CO2-(2\\Pi) shape resonance is considered in the separation of the normal modes approximation. Resonance curves and widths are computed for each vibrational mode. The calculations assume decoupling between normal modes and employ the local complex potential model for the treatment of the nuclear dynamics, usually adopted for the electron-scattering involving diatomic molecules. Results are presented for excitation up to 10 vibrational levels in each mode and comparison with data present in the literature is discussed.

  6. R-matrix calculation of low-energy electron collisions with LiH

    Energy Technology Data Exchange (ETDEWEB)

    Antony, B K [Centre of Molecular and Optical Sciences, Open University, Milton Keynes (United Kingdom); Joshipura, K N [Department of Physics, Sardar Patel University, Vallabh Vidyanagar, 388 120 Gujarat (India); Mason, N J [Centre of Molecular and Optical Sciences, Open University, Milton Keynes (United Kingdom); Tennyson, Jonathan [Department of Physics and Astronomy, University College London, Gower St., London WC1E 6BT (United Kingdom)

    2004-04-28

    Calculations are performed for electron scattering from LiH. These show that use of a close-coupled expansion gives results significantly different from calculations performed at the static exchange level employed in all previous calculations. In particular the close-coupled calculations find a Feshbach resonance which follows the first excited, a{sup 3}{sigma}{sup -}, state curve. This resonance could provide a route to dissociative attachment and electron impact vibrational excitation. Elastic scattering cross sections, which are very large, as well as inelastic cross sections for excitation to the four lowest electronically excited states are presented as a function of LiH bond length.

  7. Simulation of the transport of low-energy electrons in various forms of carbon

    Energy Technology Data Exchange (ETDEWEB)

    Terrissol, M.; Combes, M.A.; Patau, J.P. (Centre de Physique Atomique, Toulouse (France))

    1981-10-01

    This work describes a Monte Carlo transport simulation of electrons with energies ranging from 10 eV to 30 keV in homogeneous and porous graphites and amorphous carbon. We have used results of Lindhard theory adapted by Ritchie for the free electron model and by Ashley who takes electron bond into account. In the case of porous graphite we have considered the pore crossing as an interaction with the possibility of surface plasmon creation at interfaces. We compare our results with Jacobi experiments and Ashley calculations.

  8. Accurate model of electron beam profiles with emittance effects for pierce guns

    Science.gov (United States)

    Zeng, Peng; Wang, Guangqiang; Wang, Jianguo; Wang, Dongyang; Li, Shuang

    2016-09-01

    Accurate prediction of electron beam profile is one of the key objectives of electron optics, and the basis for design of the practical electron gun. In this paper, an improved model describing electron beam in Pierce gun with both space charge effects and emittance effects is proposed. The theory developed by Cutler and Hines is still applied for the accelerating region of the Pierce gun, while the motion equations of the electron beams in the anode aperture and drift tunnel are improved by modifying electron optics theory with emittance. As a result, a more universal and accurate formula of the focal length of the lens for the electron beam with both effects is derived for the anode aperture with finite dimension, and a modified universal spread curve considering beam emittance is introduced in drift tunnel region. Based on these improved motion equations of the electron beam, beam profiles with space charge effects and emittance effects can be theoretically predicted, which are subsequently approved to agree well with the experimentally measured ones. The developed model here is helpful to design more applicable Pierce guns at high frequencies.

  9. MIMAC low energy electron-recoil discrimination measured with fast neutrons

    CERN Document Server

    Riffard, Q; Guillaudin, O; Bosson, G; Bourrion, O; Bouvier, J; Descombes, T; Muraz, J -F; Lebreton, L; Maire, D; Colas, P; Giomataris, I; Busto, J; Fouchez, D; Brunner, J; Tao, C

    2016-01-01

    MIMAC (MIcro-TPC MAtrix of Chambers) is a directional WIMP Dark Matter detector project. Direct dark matter experiments need a high level of electron/recoil discrimination to search for nuclear recoils produced by WIMP-nucleus elastic scattering. In this paper, we proposed an original method for electron event rejection based on a multivariate analysis applied to experimental data acquired using monochromatic neutron fields. This analysis shows that a $10^{5}$ rejection power is reachable for electron/recoil discrimination. Moreover, the efficiency was estimated by a Monte-Carlo simulation showing that a $10^{5}$ electron rejection power is reached with a 85.1\\% nuclear recoil efficiency using the same detector gain that on the detectors running at Modane.

  10. Analytical representation of elastic scattering cross sections of low energy electrons by atmospheric gases

    Science.gov (United States)

    Ivanov, V. Y.; Sipov, N. K.; Shneyder, V. A.

    1977-01-01

    Analytical representations of the elastic scattering cross sections of electrons with energies of 0.01-1 keV in atmospheric gases of N2, O2, O are given. These representations are suitable for the Monte Carlo method.

  11. Electron recombination in low-energy nuclear recoils tracks in liquid argon

    CERN Document Server

    Wojcik, Mariusz

    2015-01-01

    This paper presents an analysis of electron-ion recombination processes in ionization tracks of recoiled atoms in liquid argon (LAr) detectors. The analysis is based on the results of computer simulations which use realistic models of electron transport and reactions. The calculations reproduce the recent experimental results of the ionization yield from 6.7 keV nuclear recoils in LAr. The statistical distribution of the number of electrons that escape recombination is found to deviate from the binomial distribution, and estimates of recombination fluctuations for nuclear recoils tracks are obtained. A study of the recombination kinetics shows that a significant part of electrons undergo very fast static recombination, an effect that may be responsible for the weak drift-field dependence of the ionization yield from nuclear recoils in some noble liquids. The obtained results can be useful in the search for hypothetical dark matter particles and in other studies that involve detection of recoiled nuclei.

  12. Rate coefficients for low-energy electron dissociative attachment to molecular hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Horacek, J.; Houfek, K.; Cizek, M. [Charles University, Faculty of Mathematics and Physics, Prague (Czech Republic); Murakami, I.; Kato, T. [National Inst. for Fusion Science, Toki, Gifu (Japan)

    2003-02-01

    Calculation of rate constants for dissociative electron attachment to molecular hydrogen is reported. The calculation is based on an improved nonlocal resonance model of Cizek, Horacek and Domcke which takes fully into account the nonlocality of the resonance dynamics and uses potentials with correct asymptotic forms. The rate constants are calculated for all quantum numbers v and J of the target molecules and for electron temperature in the range 0-30000 K. (author)

  13. Rate coefficients for low-energy electron dissociative attachment to molecular hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Horacek, J.; Houfek, K.; Cizek, M. [Charles University, Faculty of Mathematics and Physics, Prague (Czech Republic); Murakami, I.; Kato, T. [National Inst. for Fusion Science, Toki, Gifu (Japan)

    2003-02-01

    Calculation of rate constants for dissociative electron attachment to molecular hydrogen is reported. The calculation is based on an improved nonlocal resonance model of Cizek, Horacek and Domcke which takes fully into account the nonlocality of the resonance dynamics and uses potentials with correct asymptotic forms. The rate constants are calculated for all quantum numbers v and J of the target molecules and for electron temperature in the range 0-30000 K. (author)

  14. Low emittance electron beam formation with a 17 GHz RF gun

    Directory of Open Access Journals (Sweden)

    W. J. Brown

    2001-08-01

    Full Text Available We report on electron beam quality measurement results from the Massachusetts Institute of Technology 17 GHz RF gun experiment. The 1.5 cell RF gun uses a solenoid for emittance compensation. It has produced bunch charges up to 0.1 nC with beam energies up to 1 MeV. The normalized rms emittance of the beam after 35 cm of transport from the gun has been measured by a slit technique to be 3π mm mrad for a 50 pC bunch. This agrees well with PARMELA simulations at these beam energies. At the exit of the electron gun, we estimate the emittance to be about 1π mm mrad, which corresponds to a beam brightness of about 80 A/(π mm mrad^{2}. Improved beam quality should be possible with a higher energy output electron beam from the gun.

  15. Influence of the electron beam emittance on the polarization of a laser--electron X-ray generator

    CERN Document Server

    Artyukov, I A; Feshchenko, R M

    2016-01-01

    In this paper we analyze the polarization of the X-ray radiation coming from laser--electron X-ray generator (LEXG). We obtain general relations connecting the polarization state of outgoing X-ray radiation to the polarization state of laser beam as well as to the parameters of electron beam. We demonstrate that finite electron beam emittance causes a partial depolarization of initially fully polarized X-ray radiation even when the laser beam is fully polarized. We demonstrate with a number of numerical experiments that finite electron beam emittance can in some cases fundamentally alter the polarization state of X-ray radiation as compared to the polarization state of X-ray radiation scattered by electron beam with a zero emittance. Possible applications of polarized LEXG's radiation are discussed.

  16. Theoretical study of low-energy electron scattering with GeH2

    Science.gov (United States)

    Huang, Xiaotian; Wang, Kedong; Meng, Ju; Guo, Shuangcheng; Xu, Guoliang

    2017-01-01

    We present a comprehensive study of electron collisions with germylene (GeH2 using the UK molecular R-matrix codes for electron energies ranging from 0.01 to 10 eV. The calculations are performed within the static-exchange, static-exchange-polarization, and 17-state close-coupling approximations. The elastic integral, differential, momentum transfer cross sections and the excitation cross sections from the ground state to the six low-lying electron excited states are presented. We found three Feshbach resonances and one Core-excited resonance. These resonances reveal the probability of anion formation by an electron attachment process and further decay to neutral and negative ion fragments. The electronic and rotational excitation cross sections for e-GeH2 scattering are reported for the first time. The cross-section dataset obtained from the present calculations are expected to be sufficiently accurate and comprehensive for most current modeling applications involving neutral GeH2.

  17. Low energy electron induced reactions in fluorinated acetamide - probing negative ions and neutral stable counterparts*

    Science.gov (United States)

    Kopyra, Janina; König-Lehmann, Constanze; Illenberger, Eugen; Warneke, Jonas; Swiderek, Petra

    2016-06-01

    Electron impact to trifluoroacetamide (CF3CONH2, TFAA) in the energy range 0-12 eV leads to a variety of negative fragment ions which are formed via dissociative electron attachment (DEA). The underlying reactions range from single bond cleavages to remarkably complex reactions that lead to loss of the neutral units HF, H2O and HNCO as deduced from their directly observed ionic counterparts (M - H2O)-, (M - HF)- and (M - HNCO)-. Also formed are the pseudo-halogen ions CN- and OCN-. All these reactions proceed dominantly via a resonance located near 1 eV, i.e., electrons at subexcitation energies trigger reactions involving multiple bond cleavages. The electron induced generation of the neutral molecules HF, H2O and HNCO in condensed TFAA films is probed by temperature controlled thermal desorption spectrometry (TDS) which can be viewed as a complementary techniques to gas-phase experiments in DEA to directly probe the neutral counterparts. Contribution to the Topical Issue "Advances in Positron and Electron Scattering", edited by Paulo Limao-Vieira, Gustavo Garcia, E. Krishnakumar, James Sullivan, Hajime Tanuma and Zoran Petrovic.

  18. Cross sections for low-energy electron scattering from adenine in the condensed phase.

    Science.gov (United States)

    Panajotović, Radmila; Michaud, Marc; Sanche, Léon

    2007-01-07

    Measurements of the vibrational and electronic excitation of a sub-monolayer up to a monolayer film of adenine were performed with a high resolution electron energy-loss (HREEL) spectrometer. The integral cross sections (over the half-space angle) for excitation of the normal vibrational modes of the ground electronic state and electronically excited states are calculated from the measured reflectivity EEL spectra. Most cross sections for vibrational excitation are of the order of 10(-17) cm(2), the largest being the out-of-plane wagging of the amino-group and the six-member ring deformations. A wide resonance feature appears in the incident energy dependence of the vibrational cross sections at 3-5 eV, while a weak shoulder is present in this dependence for combined ring deformations and bending of hydrogen atoms. For the five excited electronic states, at 4.7, 5.0, 5.5, 6.1 and 6.6 eV, the cross sections are of the order of 10(-18) cm(2), except in the case of the state at the energy of 6.1 eV, for which it is two to three times higher.

  19. Observation of Strong Reflection of Electron Waves Exiting a Ballistic Channel at Low Energy

    Science.gov (United States)

    Vaz, Canute I.; Liu, Changze; Campbell, Jason P.; Ryan, Jason T.; Southwick, Richard G.; Gundlach, David; Oates, Anthony S.; Huang, Ru; Cheung, Kin. P.

    2016-01-01

    Wave scattering by a potential step is a ubiquitous concept. Thus, it is surprising that theoretical treatments of ballistic transport in nanoscale devices, from quantum point contacts to ballistic transistors, assume no reflection even when the potential step is encountered upon exiting the device. Experiments so far seem to support this even if it is not clear why. Here we report clear evidence of coherent reflection when electron wave exits the channel of a nanoscale transistor and when the electron energy is low. The observed behavior is well described by a simple rectangular potential barrier model which the Schrodinger's equation can be solved exactly. We can explain why reflection is not observed in most situations but cannot be ignored in some important situations. Our experiment also represents a direct measurement of electron injection velocity - a critical quantity in nanoscale transistors that is widely considered not measurable. PMID:27882264

  20. Low-energy internal conversion electrons spectrometry with a silicon diode

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Thiago R. [Universidade de Sao Paulo (USP), Sao Paulo, SP (Brazil). Inst. de Fisica; Camargo, Fabio de; Goncalves, Josemary A.C. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)]. E-mail: fcamargo@ipen.br; josemary@ipen.br; ccbueno@ipen.br; Bueno, Carmen C. [Pontificia Universidade Catolica de Sao Paulo (PUC/SP), Sao Paulo, SP (Brazil). Dept. de Fisica; Fraga, Margarida R.F. [Universidade de Coimbra, Coimbra (Portugal). Dept. de Fisica. Lab. de Instrumentacao e Fisica Experimental de Particulas]. E-mail: margarida@lipc.fis.uc.pt

    2007-07-01

    In this paper the preliminary results obtained with a PIN photodiode (SFH00206) for the detection and spectrometry of internal results from {sup 57}Co, {sup 109}Cd and {sup 133}Ba radioactive sources are described. The effect of the reverse bias on the energy resolution was studied and has shown a value of 2.8 keV (FHWM) for the {sup 57}Co 129.36 keV electron emission, when the diode was biased with 20 V at a temperature of 22 degree C. The obtained energy resolution can be attributed to both the energy loss in the diode dead layer and in the Makrofol covering of the sources, besides the contribution of the preamplifier electronic noise. Nevertheless, the energy resolutions measured are sufficiently good to justify the use of the diode for detection and spectrometry of internal conversion electrons. (author)

  1. Optimal electron, phonon, and magnetic characteristics for low energy thermally induced magnetization switching

    Energy Technology Data Exchange (ETDEWEB)

    Atxitia, U., E-mail: Unai.Atxitia@uni-konstanz.de [Fachbereich Physik, Universität Konstanz, D-78457 Konstanz (Germany); Zukunftskolleg, Universität Konstanz, D-78457 Konstanz (Germany); Ostler, T. A., E-mail: t.ostler@exeter.ac.uk [Department of Physics, University of York, York YO105DD (United Kingdom); College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, Devon EX4 4SB (United Kingdom); Chantrell, R. W. [Department of Physics, University of York, York YO105DD (United Kingdom); Chubykalo-Fesenko, O. [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28049 Madrid (Spain)

    2015-11-09

    Using large-scale computer simulations, we thoroughly study the minimum energy required to thermally induced magnetization switching (TIMS) after the application of a femtosecond heat pulse in transition metal-rare earth ferrimagnetic alloys. We find that for an energy efficient TIMS, a low ferrimagnetic net magnetization with a strong temperature dependence is the relevant factor for the magnetic system. For the lattice and electron systems, the key physics for efficient TIMS is a large electron-phonon relaxation time. Importantly, we show that as the cooling time of the heated electrons is increased, the minimum power required to produce TIMS can be reduced by an order of magnitude. Our results show the way to low power TIMS by appropriate engineering of magnetic heterostructures.

  2. Preparation of {sup 114m}In low energy conversion electron sources

    Energy Technology Data Exchange (ETDEWEB)

    Wrede, C., E-mail: wrede@uw.ed [Center for Experimental Nuclear Physics and Astrophysics, and Department of Physics, University of Washington, Seattle, WA 98195 (United States); Filippone, B.W. [Kellogg Radiation Laboratory, California Institute of Technology, Pasadena, California 91125 (United States); Garcia, A.; Harper, G.C. [Center for Experimental Nuclear Physics and Astrophysics, and Department of Physics, University of Washington, Seattle, WA 98195 (United States); Lassell, S. [Department of Nuclear Engineering, North Carolina State University, Raleigh, North Carolina 27695 (United States); Liu, J. [Kellogg Radiation Laboratory, California Institute of Technology, Pasadena, California 91125 (United States); Department of Physics, Shanghai Jiao Tong University, Shanghai 200240 (China); Mendenhall, M.P. [Kellogg Radiation Laboratory, California Institute of Technology, Pasadena, California 91125 (United States); Palmer, A.S.C. [Center for Experimental Nuclear Physics and Astrophysics, and Department of Physics, University of Washington, Seattle, WA 98195 (United States); Pattie, R.W. [Department of Physics, North Carolina State University, Raleigh, North Carolina 27695 (United States); Will, D.I. [Center for Experimental Nuclear Physics and Astrophysics, and Department of Physics, University of Washington, Seattle, WA 98195 (United States); Young, A.R. [Department of Physics, North Carolina State University, Raleigh, North Carolina 27695 (United States)

    2011-05-15

    Highlights: {yields} Controlled ion implantation of In-113 into thin Al substrate. {yields} Production of In-114m (half life = 50 days) by neutron irradiation. {yields} Use of In-114m as a source of electron lines and continuum for calibrations. {yields} Source reactivation by short neutron irradiation. -- Abstract: The preparation of {sup 114m}In sources of conversion electrons in the energy range 162-190 keV and {beta} continuum with a 1989 keV endpoint via ion implantation of {sup 113}In into Al substrates and subsequent irradiation by thermal and epi-thermal neutrons in a nuclear reactor is described.

  3. Elastic scattering of low energy electrons in partially ionized dense semiclassical plasma

    Energy Technology Data Exchange (ETDEWEB)

    Dzhumagulova, K. N., E-mail: dzhumagulova.karlygash@gmail.com; Shalenov, E. O.; Ramazanov, T. S. [IETP, Al Farabi Kazakh National University, 71al Farabi Street, Almaty 050040 (Kazakhstan)

    2015-08-15

    Elastic scattering of electrons by hydrogen atoms in a dense semiclassical hydrogen plasma for low impact energies has been studied. Differential scattering cross sections were calculated within the effective model of electron-atom interaction taking into account the effect of screening as well as the quantum mechanical effect of diffraction. The calculations were carried out on the basis of the phase-function method. The influence of the diffraction effect on the Ramsauer–Townsend effect was studied on the basis of a comparison with results made within the effective polarization model of the Buckingham type.

  4. Low-energy electron dose-point kernel simulations using new physics models implemented in Geant4-DNA

    Energy Technology Data Exchange (ETDEWEB)

    Bordes, Julien, E-mail: julien.bordes@inserm.fr [CRCT, UMR 1037 INSERM, Université Paul Sabatier, F-31037 Toulouse (France); UMR 1037, CRCT, Université Toulouse III-Paul Sabatier, F-31037 (France); Incerti, Sébastien, E-mail: incerti@cenbg.in2p3.fr [Université de Bordeaux, CENBG, UMR 5797, F-33170 Gradignan (France); CNRS, IN2P3, CENBG, UMR 5797, F-33170 Gradignan (France); Lampe, Nathanael, E-mail: nathanael.lampe@gmail.com [Université de Bordeaux, CENBG, UMR 5797, F-33170 Gradignan (France); CNRS, IN2P3, CENBG, UMR 5797, F-33170 Gradignan (France); Bardiès, Manuel, E-mail: manuel.bardies@inserm.fr [CRCT, UMR 1037 INSERM, Université Paul Sabatier, F-31037 Toulouse (France); UMR 1037, CRCT, Université Toulouse III-Paul Sabatier, F-31037 (France); Bordage, Marie-Claude, E-mail: marie-claude.bordage@inserm.fr [CRCT, UMR 1037 INSERM, Université Paul Sabatier, F-31037 Toulouse (France); UMR 1037, CRCT, Université Toulouse III-Paul Sabatier, F-31037 (France)

    2017-05-01

    When low-energy electrons, such as Auger electrons, interact with liquid water, they induce highly localized ionizing energy depositions over ranges comparable to cell diameters. Monte Carlo track structure (MCTS) codes are suitable tools for performing dosimetry at this level. One of the main MCTS codes, Geant4-DNA, is equipped with only two sets of cross section models for low-energy electron interactions in liquid water (“option 2” and its improved version, “option 4”). To provide Geant4-DNA users with new alternative physics models, a set of cross sections, extracted from CPA100 MCTS code, have been added to Geant4-DNA. This new version is hereafter referred to as “Geant4-DNA-CPA100”. In this study, “Geant4-DNA-CPA100” was used to calculate low-energy electron dose-point kernels (DPKs) between 1 keV and 200 keV. Such kernels represent the radial energy deposited by an isotropic point source, a parameter that is useful for dosimetry calculations in nuclear medicine. In order to assess the influence of different physics models on DPK calculations, DPKs were calculated using the existing Geant4-DNA models (“option 2” and “option 4”), newly integrated CPA100 models, and the PENELOPE Monte Carlo code used in step-by-step mode for monoenergetic electrons. Additionally, a comparison was performed of two sets of DPKs that were simulated with “Geant4-DNA-CPA100” – the first set using Geant4′s default settings, and the second using CPA100′s original code default settings. A maximum difference of 9.4% was found between the Geant4-DNA-CPA100 and PENELOPE DPKs. Between the two Geant4-DNA existing models, slight differences, between 1 keV and 10 keV were observed. It was highlighted that the DPKs simulated with the two Geant4-DNA’s existing models were always broader than those generated with “Geant4-DNA-CPA100”. The discrepancies observed between the DPKs generated using Geant4-DNA’s existing models and “Geant4-DNA-CPA100” were

  5. First Observation of Low Energy Electron Neutrinos in a Liquid Argon Time Projection Chamber

    Energy Technology Data Exchange (ETDEWEB)

    Acciarri, R.; et al.

    2016-10-13

    Liquid argon time projection chambers (LArTPCs) produce remarkable fidelity in the observation of neutrino interactions. The superior capabilities of such detectors to reconstruct the spatial and calorimetric information of neutrino events have made them the detectors of choice in a number of experiments, specifically those looking to observe electron neutrino ($\

  6. A low-energy-spread rf accelerator for a far-infrared free electron laser

    Science.gov (United States)

    van der Geer, C. A. J.; Bakker, R. J.; van der Meer, A. F. G.; van Amersfoort, P. W.; Gillespie, W. A.; Saxon, G.; Poole, M. W.

    1993-10-01

    A high electron current and a small energy spread are essential for the operation of a free electron laser (FEL). In this paper we discuss the design and performance of the accelerator for FELIX, the free electron laser for infrared experiments. The system consists of a thermionic gun, a prebuncher, a buncher and two standard commercial linac sections. The gun is operated with a pulse duration of 280 ps and a bunch charge of 200 pC. After compression to 35 ps by the prebuncher, the bunches are accelerated to 4 MeV in the buncher and simultaneously compressed to 6 ps. The principle of the method is that the order of the electrons is conserved in the buncher, so that the resulting more or less linear energy-phase relationship along each bunch can be compensated effectively against space charge forces and the accelerating field gradient in the linacs, via an appropriate choice of the phase of the rf wave. Behind the linacs an rms energy spread of 0.30% has been measured.

  7. Collisions between low-energy electrons and small polyatomic targets of biological relevance

    Science.gov (United States)

    Hargreaves, Leigh

    2016-05-01

    Over the last decade, cross section measurements and calculations for DNA prototype molecules have received significant attention from the collisions community, due to the potential applications of this data in modelling electron transport through biological matter with a view to improving radiation dosimetry. Such data are additionally interesting from a fundamental aspect, as small carbon-based molecules are ideal targets for considering effects including target conformation, long-range dynamical interactions and coupling effects between the various degrees of freedom on the scattering properties of the target. At the California State University Fullerton, we have made a series of measurements of the elastic, vibrationally inelastic and electronically inelastic cross sections for a variety of small polyatomic targets, including water and the basic alcohols, ethylene, toluene and several fluorinated alkanes. These processes are important in a range of applications, primarily for modelling electron transport and thermalization, and energy deposition to a biological media. The data were obtained using a high resolution electron energy-loss spectrometer, operating in a crossed beam configuration with a moveable aperture gas source. The gas source design facilitates both an expedient and highly accurate method of removing background signal, and removes uncertainties from the data due to uncertainties in the beam profile. We have also performed scattering calculations employing the Schwinger Multichannel method, in collaboration with the California institute of technology, to compare with our measurements. In this talk, I will present an overview of our recent data and future research plans.

  8. First Observation of Low Energy Electron Neutrinos in a Liquid Argon Time Projection Chamber

    CERN Document Server

    Acciarri, R; Asaadi, J; Baller, B; Bolton, T; Bromberg, C; Cavanna, F; Church, E; Edmunds, D; Ereditato, A; Farooq, S; Fitzpatrick, R S; Fleming, B; Hackenburg, A; Horton-Smith, G; James, C; Lang, K; Luo, X; Mehdiyev, R; Page, B; Palamara, O; Rebel, B; Schukraft, A; Scanavini, G; Soderberg, M; Spitz, J; Szelc, A M; Weber, M; Yang, T; Zeller, G P

    2016-01-01

    Liquid argon time projection chambers (LArTPCs) produce remarkable fidelity in the observation of neutrino interactions. The superior capabilities of such detectors to reconstruct the spatial and calorimetric information of neutrino events have made them the detectors of choice in a number of experiments, specifically those looking to observe electron neutrino ($\

  9. AREAL low energy electron beam applications in life and materials sciences

    Energy Technology Data Exchange (ETDEWEB)

    Tsakanov, V.M., E-mail: tsakanov@asls.candle.am [CANDLE Synchrotron Research Institute, 0040 Yerevan (Armenia); Yerevan State University, 0025 Yerevan (Armenia); Aroutiounian, R.M. [Yerevan State University, 0025 Yerevan (Armenia); Amatuni, G.A. [CANDLE Synchrotron Research Institute, 0040 Yerevan (Armenia); Aloyan, L.R.; Aslanyan, L.G. [Yerevan State University, 0025 Yerevan (Armenia); Avagyan, V.Sh. [CANDLE Synchrotron Research Institute, 0040 Yerevan (Armenia); Babayan, N.S. [Yerevan State University, 0025 Yerevan (Armenia); Institute of Molecular Biology NAS, 0014 Yerevan (Armenia); Buniatyan, V.V. [State Engineering University of Armenia, 0009 Yerevan (Armenia); Dalyan, Y.B.; Davtyan, H.D. [CANDLE Synchrotron Research Institute, 0040 Yerevan (Armenia); Derdzyan, M.V. [Institute for Physical Research NAS, 0203 Ashtarak (Armenia); Grigoryan, B.A. [CANDLE Synchrotron Research Institute, 0040 Yerevan (Armenia); Grigoryan, N.E. [A.I. Alikhanyan National Science Laboratory (YerPhi), 0036 Yerevan (Armenia); Hakobyan, L.S. [CANDLE Synchrotron Research Institute, 0040 Yerevan (Armenia); Haroutyunian, S.G. [Yerevan State University, 0025 Yerevan (Armenia); Harutiunyan, V.V. [A.I. Alikhanyan National Science Laboratory (YerPhi), 0036 Yerevan (Armenia); Hovhannesyan, K.L. [Institute for Physical Research NAS, 0203 Ashtarak (Armenia); Khachatryan, V.G. [CANDLE Synchrotron Research Institute, 0040 Yerevan (Armenia); Martirosyan, N.W. [CANDLE Synchrotron Research Institute, 0040 Yerevan (Armenia); State Engineering University of Armenia, 0009 Yerevan (Armenia); Melikyan, G.S. [State Engineering University of Armenia, 0009 Yerevan (Armenia); and others

    2016-09-01

    The AREAL laser-driven RF gun provides 2–5 MeV energy ultrashort electron pulses for experimental study in life and materials sciences. We report the first experimental results of the AREAL beam application in the study of molecular-genetic effects, silicon-dielectric structures, ferroelectric nanofilms, and single crystals for scintillators.

  10. Plasmons in doped finite carbon nanotubes and their interactions with fast electrons and quantum emitters

    Science.gov (United States)

    de Vega, Sandra; Cox, Joel D.; de Abajo, F. Javier García

    2016-08-01

    We study the potential of highly doped finite carbon nanotubes to serve as plasmonic elements that mediate the interaction between quantum emitters. Similar to graphene, nanotubes support intense plasmons that can be modulated by varying their level of electrical doping. These excitations exhibit large interaction with light and electron beams, as revealed upon examination of the corresponding light extinction cross-section and electron energy-loss spectra. We show that quantum emitters experience record-high Purcell factors, while they undergo strong mutual interaction mediated by their coupling to the tube plasmons. Our results show the potential of doped finite nanotubes as tunable plasmonic materials for quantum optics applications.

  11. Imaging pulsed laser deposition growth of homo-epitaxial SrTiO3 by low-energy electron microscopy

    Science.gov (United States)

    van der Torren, A. J. H.; van der Molen, S. J.; Aarts, J.

    2016-12-01

    By combining low-energy electron microscopy with in situ pulsed laser deposition we have developed a new technique for film growth analysis, making use of both diffraction and real-space information. Working at the growth temperature, we can use: the intensity and profile variations of the specular beam to follow the coverage in a layer-by-layer fashion; real-space microscopy to follow e.g. atomic steps at the surface; and electron reflectivity to probe the unoccupied band structure of the grown material. Here, we demonstrate our methodology for homo-epitaxial growth of SrTiO3. Interestingly, the same combination of techniques will also be applicable to hetero-epitaxial oxide growth, largely extending the scope of research possibilities.

  12. Field-modulated low-energy electronic and optical properties of armchair silicene nanoribbons

    Science.gov (United States)

    Shyu, Feng-Lin

    2017-01-01

    The tight-binding model including spin-orbit coupling is used to study electronic and optical properties of armchair silicene nanoribbons (ASiNRs) in electric fields. Perpendicular electric field monotonically increases band-gap, the DOS, and absorption frequency and strength. It does not change spin-degeneracy, edge-states, and optical selection rule. However, parallel electric field strongly modulates energy dispersions resulting in oscillatory band-gaps, shift in edge-states, and destruction of spin-degeneracy. It induces more transition channels and constructs new selection rules that exhibits richer optical spectra. Modulations of electronic and optical properties of ASiNRs have strong dependence on the direction of electric field and nanoribbon's geometry.

  13. Low energy electron stimulated desorption from DNA films dosed with oxygen

    Energy Technology Data Exchange (ETDEWEB)

    Mirsaleh-Kohan, Nasrin; Bass, Andrew D.; Cloutier, Pierre; Massey, Sylvain; Sanche, Leon [Groupe en sciences des radiations, Faculte de medecine et des sciences de la sante, Universite de Sherbrooke, Sherbrooke, Quebec J1H 5N4 (Canada)

    2012-06-21

    Desorption of anions stimulated by 1-18 eV electron impact on self-assembled monolayer (SAM) films of single DNA strands is measured as a function of film temperature (50-250 K). The SAMs, composed of 10 nucleotides, are dosed with O{sub 2}. The OH{sup -} desorption yields increase markedly with exposure to O{sub 2} at 50 K and are further enhanced upon heating. In contrast, the desorption yields of O{sup -}, attributable to dissociative electron attachment to trapped O{sub 2} molecules decrease with heating. Irradiation of the DNA films prior to the deposition of O{sub 2} shows that this surprising increase in OH{sup -} desorption, at elevated temperatures, arises from the reaction of O{sub 2} with damaged DNA sites. These results thus appear to be a manifestation of the so-called 'oxygen fixation' effect, well known in radiobiology.

  14. Rare earth boride electron emitter materials fabrication and evaluation

    Science.gov (United States)

    Swanson, L. W.; Davis, P. R.; Gesley, M. A.

    1982-03-01

    Techniques were developed for routine preparation of single crystal rods of LaB6, CeB6 and PrB6 by arc float zone refining. Single crystal, oriented samples were prepared from these rods and mounted as cathodes for testing. Several mounting systems were used, and flat, pointed cone and truncated cone thermionic cathodes were studied. Pointed field emitters of LaB6(100) were also investigated. Variation of thermionic emitted current density and thermal stability of materials were studied as functions of rare earth element, bulk stoichiometry and crystal orientation. Life tests were performed on several different LaB6(100) cathodes. One such cathode operated for over 3000 hours at approximately 10 A/sq cm emitted current density with no serious physical degradation. Surface properties of the materials were investigated by various surface analysis techniques.

  15. Low-energy electron attachment to the dichlorodifluoromethane (CCl2F2) molecule.

    Science.gov (United States)

    Graupner, K; Haughey, S A; Field, T A; Mayhew, C A; Hoffmann, T H; May, O; Fedor, J; Allan, M; Fabrikant, I I; Illenberger, E; Braun, M; Ruf, M-W; Hotop, H

    2010-01-28

    Results from a joint experimental study of electron attachment to dichlorodifluoromethane (CCl(2)F(2)) molecules in the gas phase are reported. In a high resolution electron beam experiment involving two versions of the laser photoelectron attachment method, the relative cross section for formation of the dominant anion Cl(-) was measured over the energy range 0.001-1.8 eV at the gas temperature T(G) = 300 K. It exhibits cusp structure at thresholds for vibrational excitation of the nu(3)(a(1)) mode due to interaction with the attachment channels. With reference to the thermal attachment rate coefficient k(T = 300 K) = 2.2(8) x 10(-9) cm(3) s(-1) (fitted average from several data), a new highly resolved absolute attachment cross section for T(G) = 300 K was determined. Partial cross sections for formation of the anions Cl(-), Cl(2)(-), F(-), ClF(-), and CCl(2)F(-) were measured over the range 0-12 eV, using three different electron beam experiments of medium energy resolution. The dependence of the attachment rate coefficient k(T(e);T(G) = 300 K) on electron temperature T(e) was calculated over the range 50-15 000 K, based on a newly constructed total cross section for anion formation at T(G) = 300 K. R-matrix calculations for Cl(-) production have been carried out for comparison with the experimental data. The R-matrix results are in line with the main experimental observations and predict the dependence of the DEA cross section on the initial vibrational level nu(3)() and on the vibrational temperature. Furthermore, the cross section for vibrational excitation of the nu(3) mode has been computed.

  16. Low-Energy Rate Enhancement in Recombination Processes of Electrons into Bare Uranium Ions

    Institute of Scientific and Technical Information of China (English)

    WU Yong; ZENG Si-Liang; DUAN Bin; YAN Jun; WANG Jian-Guo; DONG Chen-Zhong; MA Xin-Wen

    2007-01-01

    Based on the Dirac-Fork-Slater method combined with the multichannel quantum defect theory, the recombination processes of electrons into bare uranium ions (U92+) are investigated in the relative energy range close to zero, and the x-ray spectrum emitted in the direct radiative recombination and cascades processes are simulated. Compared with the recent measurement, it is found that the rate enhancement comes from the additional populations on high Rydberg states. These additional populations may be produced by other recombination mechanisms, such as the external electric-magnetic effects and the many-body correlation effects, which still remains an open problem.

  17. Structural analysis of organic films by electron diffraction at high and low energy

    Science.gov (United States)

    Stevens, Michael Richard

    This dissertation concerns the importance of electron diffraction as a structural tool in the analysis of organic crystalline materials, focusing on those specimens for which X-ray analysis is insufficient. It extends the range of knowledge needed for solving common problems that occur in such analysis: sample preparation, damage processes, extraction of crystallographic phases, and specimen irregularities. This research reports the first direct measurement of electron beam damage in transmission for beam energies below the carbon-K edge and in part extends the research of Howie, Isaacson, Fryer, and others. Here, it is confirmed that a correlation exists between the carbon-K shell ionization and the damage cross section by direct measurement of spot fading in transmission at beam energies ranging from 200eV to 1000eV. The threshold in damage was directly measured confirming the hypothesis linking K shell ionization to damage in the aromatic specimens; however, for the aliphatic specimens, the threshold effects were not as significant, indicating the importance of other damage processes which are explained. Calculations based on the experimental data show a region of beam energy which may be utilized to image single molecules, in contradiction to previous theory. Utilizing energy filtering, Kohler mode, cryo-microscopy, and standard low-dose techniques, the structures of two organic specimens which could not be solved by X-ray are solved by electron diffraction. These specimens exhibited high sensitivity to the electron beam and were thought good candidates for the project. The first is a Diacetylene polymer 1,2 bis (10,12 tricosadiynoyl)-sn-glycero-3phosphocholine (DC89PC) with a large unit cell, here only a partial structure solution was possible by Direct Methods (DM) phasing and chemical modeling. The full solution will require new sample preparation techniques. Film bending was observed directly, and the resulting effects to the diffraction data are explained

  18. Dissociative recombination and vibrational excitation of BF+ in low energy electron collisions

    Science.gov (United States)

    Mezei, J. Zs; Colboc, F.; Pop, N.; Ilie, S.; Chakrabarti, K.; Niyonzima, S.; Lepers, M.; Bultel, A.; Dulieu, O.; Motapon, O.; Tennyson, J.; Hassouni, K.; Schneider, I. F.

    2016-10-01

    The latest molecular data—potential energy curves and Rydberg-valence interactions—characterising the super-excited electronic states of BF are reviewed in order to provide the input for the study of their fragmentation dynamics. Starting from this input, the main paths and mechanisms of BF+ dissociative recombination and vibrational excitation are analysed. Their cross sections are computed for the first time using a method based on the multichannel quantum defect theory (MQDT), and Maxwellian rate-coefficients are calculated and displayed in ready-to-be-used format for low temperature plasma kinetics simulations.

  19. Towards a Small Emittance Design of the JLEIC Electron Collider Ring

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Fanglei [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Derbenev, Yaroslav [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Hutton, Andrew M. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Morozov, Vasiliy [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Pilat, Fulvia C. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Zhang, Yuhong [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)

    2016-05-01

    The electron collider ring of the Jefferson Lab Electron-Ion Collider (JLEIC) is designed to provide an electron beam with a small beam size at the IP for collisions with an ion beam in order to reach a desired high luminosity. For a chosen beta-star at the IP, electron beam size is determined by the equilibrium emittance that can be obtained through a linear optics design. This paper briefly describes the baseline design of the electron collider ring reusing PEP-II components and considering their parameters (such as dipole sagitta, magnet field strengths and acceptable synchrotron radiation power) and reports a few approaches to reducing the equilibrium emittance in the electron collider ring.

  20. Validities of three multislice algorithms for quantitative low-energy transmission electron microscopy.

    Science.gov (United States)

    Ming, W Q; Chen, J H

    2013-11-01

    Three different types of multislice algorithms, namely the conventional multislice (CMS) algorithm, the propagator-corrected multislice (PCMS) algorithm and the fully-corrected multislice (FCMS) algorithm, have been evaluated in comparison with respect to the accelerating voltages in transmission electron microscopy. Detailed numerical calculations have been performed to test their validities. The results show that the three algorithms are equivalent for accelerating voltage above 100kV. However, below 100 kV, the CMS algorithm will introduce significant errors, not only for higher-order Laue zone (HOLZ) reflections but also for zero-order Laue zone (ZOLZ) reflections. The differences between the PCMS and FCMS algorithms are negligible and mainly appear in HOLZ reflections. Nonetheless, when the accelerating voltage is further lowered to 20 kV or below, the PCMS algorithm will also yield results deviating from the FCMS results. The present study demonstrates that the propagation of the electron wave from one slice to the next slice is actually cross-correlated with the crystal potential in a complex manner, such that when the accelerating voltage is lowered to 10 kV, the accuracy of the algorithms is dependent of the scattering power of the specimen. © 2013 Elsevier B.V. All rights reserved.

  1. Electrical performance of the InGaP solar cell irradiated with low energy electron beams

    Energy Technology Data Exchange (ETDEWEB)

    Okuno, Yasuki; Okuda, Shuichi; Kojima, Takeo; Oka, Takashi [Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai City, Osaka (Japan); Kawakita, Shirou; Imaizumi, Mitsuru; Kusawake, Hiroaki [Japan Aerospace Exploration Agency (JAXA), 2-1-1 Sengen, Tsukuba, Ibaraki (Japan)

    2015-06-15

    The investigation of the radiation degradation characteristics of InGaP space solar cells is important. In order to understand the mechanism of the degradation by radiation the samples of the InGaP solar cell were irradiated in vacuum and at ambient temperature with electron beams from a Cockcroft-Walton type accelerator at Osaka Prefecture University. The threshold energies for recoil were obtained by theoretical calculation. The energies and the fluences of the electron beams were from 60 to 400 keV and from 3 x 10{sup 14} to 3 x 10{sup 16} cm{sup -2}, respectively. The light-current-voltage measurements were performed. The degradation of Isc caused by the defects related to the phosphorus atoms was observed and the degradation was suppressed by irradiation at an energy higher than the threshold energy for recoiling Indium atoms. At an energy of 60 keV, where the recoil does not occur, the V{sub oc} was degraded. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. Bound-state methods for low-energy electron-ion scattering

    Science.gov (United States)

    Rosenberg, Leonard

    1996-02-01

    An effective-potential formalism, previously developed for electron scattering by a neutral target, is extended to apply to electron-ion scattering, with the requirement of antisymmetrization now accounted for explicitly. A minimum principle for the effective potential is derived, valid for scattering below the ionization threshold and applicable when, as is usually the case, the target wave functions are imprecisely known. The basis for the minimum principle is the Rayleigh-Ritz property that is satisfied by the modified Hamiltonian in terms of which the effective potential is defined. An analysis of single-channel, zero-energy scattering for a particular partial wave is presented; it is based on the effective-potential formalism and leads to an absolute definition of the zero-energy phase shift δ(0) of the form δ(0)=μ(∞)π, where μ(n) is the quantum defect of the nth energy level. This result may be thought of as an extension of Levinson's theorem for scattering by short-range potentials.

  3. Kinetics of low energy electron attachment to some fluorinated alcohols in the gas phase

    Science.gov (United States)

    Wnorowski, K.; Wnorowska, J.; Kopyra, J.; Michalczuk, B.; Szamrej, I.; Barszczewska, W.

    2014-01-01

    Thermal electron attachment processes in the mixtures of CH3CH2OH, CF3CH2OH, CF3CF2CH2OH, (CF3)2CHOH and CH3CH(OH)CF3 with carbon dioxide have been investigated using an electron Pulsed Townsend technique. Measurements were carried out in the temperature range (298-413) K. The obtained rate coefficients depended on temperature in accordance to Arrhenius equation. From the fit to the experimental data points with function ln(k) = ln(A)-Ea/kBT the activation energies (Ea's) were determined. The rate coefficients at 298 K are equal to 3.2 × 10-13 cm3 s-1, 5.1 × 10-11 cm3 s-1, 1.1 × 10-10 cm3 s-1, 3.0 × 10-10 cm3 s-1 and 2.6 × 10-11 cm3 s-1 and activation energies are: 0.37 eV, 0.25 eV, 0.28 eV, 0.20 eV and 0.23 eV, respectively for CH3CH2OH, CF3CH2OH, CF3CF2CH2OH, (CF3)2CHOH and CH3CH(OH)CF3.

  4. Higher lying resonances in low-energy electron scattering with carbon monoxide

    CERN Document Server

    Dora, Amar; Chakrabarti, Kalyan

    2016-01-01

    R-matrix calculations on electron collisions with CO are reported whose aim is to identify any higher-lying resonances above the well-reported and lowest $^2\\Pi$ resonance at about 1.6~eV. Extensive tests with respect to basis sets, target models and scattering models are performed. The final results are reported for the larger cc-pVTZ basis set using a 50 state close-coupling (CC) calculation. The Breit-Wigner eigenphase sum and the time-delay methods are used to detect and fit any resonances. Both these methods find a very narrow $^2\\Sigma^+$ symmetry Feshbach-type resonance very close to the target excitation threshold of the b $^3\\Sigma^+$ state which lies at 12.9 eV in the calculations. This resonance is seen in the CC calculation using cc-pVTZ basis set while a CC calculation using the cc-pVDZ basis set does not produce this feature. The electronic structure of CO$^-$ is analysed in the asymptotic region, 45 molecular states are found to correlate with states dissociating to an anion and an atom. Electr...

  5. Emittance studies at the Los Alamos national laboratory free electron laser

    Science.gov (United States)

    Carlsten, B. E.; Feldman, D. W.; Lumpkin, A. H.; Sollid, J. E.; Stein, W. E.; Warren, R. W.

    1988-10-01

    Recent emittance studies at the Los Alamos FEL have indicated several areas of concern in the linac and beamline feeding the wiggler. These studies included both experimental measurements and computer simulations. The beamline starts with a 5 A micropulse from the thermionic cathode in the gun. After bunching by velocity modulation and acceleration to 20 MeV in a 1300 MHz standing wave accelerator, the beam current is roughly 250 A. Final bunching to 800 A is performed in the nonisochronous bend that rotates the electrons onto the axis of the wiggler and the optical cavity. Four emittance growth mechanisms of special importance have been studied. First, a rapid growth of the electron beam's emittance immediately after the spherical gridded Pierce gun resulted, in part, from the long time required for our pulsing electronics to ramp the grid voltage up at the start and down at the end of the pulse, which created a pulse with a cosine-like current distribution as a function of time. The growth was compounded by the extremely small radial beam size (almost a waist) leaving the gun. In addition, we saw evidence of electrostatic charging of the insulators in the gun, reducing the quality of the electron beam further. Second the action of the solenoidal focusing fields in the low-voltage bunching region was studied, and criteria for a minimum emittance growth were established. Third, maximum misalignment angles and displacements for various elements of the beamline were calculated for the desired low emittance growth. Finally, emittance growth in the horizontal dimensions through the nonisochronous bend caused by varying energy depression on the particles due to longitudinal wake fields was both calculated and observed. In addition, we measured energy depressions caused by the wake fields generated by various other elements in the beamline. Strategies were developed to relieve the magnitude of these wake-field effects.

  6. Low-Energy Electronic Properties of Clean CaRuO3: Elusive Landau Quasiparticles

    Science.gov (United States)

    Schneider, M.; Geiger, D.; Esser, S.; Pracht, U. S.; Stingl, C.; Tokiwa, Y.; Moshnyaga, V.; Sheikin, I.; Mravlje, J.; Scheffler, M.; Gegenwart, P.

    2014-05-01

    We have prepared high-quality epitaxial thin films of CaRuO3 with residual resistivity ratios up to 55. Shubnikov-de Haas oscillations in the magnetoresistance and a T2 temperature dependence in the electrical resistivity only below 1.5 K, the coefficient of which is substantially suppressed in large magnetic fields, establish CaRuO3 as a Fermi liquid (FL) with an anomalously low coherence scale. At T >1.5 K non-Fermi-liquid (NFL) behavior is found in the electrical resistivity. The high sample quality allows access to the intrinsic electronic properties via THz spectroscopy. For frequencies below 0.6 THz, the conductivity is Drude-like and can be modeled by FL concepts; for higher frequencies, non-Drude behavior is found, which is inconsistent with FL predictions. This establishes CaRuO3 as a prime example of optical NFL behavior in the THz range.

  7. Point defects induced in LiF by low energy electrons

    Energy Technology Data Exchange (ETDEWEB)

    Baldacchini, Giuseppe; Montereali, Rosa Maria [ENEA, Centro Ricerche Frascati, Rome (Italy); Scacco, Augusto [Rome, Univ. (Italy). Dipt. di Fisica]|[INFM, Rome (Italy); Cremona, Marco; D`Auria, Giuliano

    1997-09-01

    A systematic study of the coloring of LiF crystals and films irradiated by 3 keV electrons at various temperatures was carried out analysing their absorption and luminescence spectra. The three stage behaviour of the F coloring curve as a function of the irradiation dose was revealed and the saturation of the process was identified for the first time with this kind of radiation. The kinetics of the defect formation confirmed the expectations derived from the most comprehensive theoretical model developed to explain the coloring process. The irradiation temperature was found to have an influence on both the proportion of different defects created and on their stability and the overall coloring efficiency turned out to be higher when the irradiation was performed on films. Various explanations to these observations are put forward and discussed.

  8. Resonant antineutrino induced electron capture with low energy bound-beta beams

    CERN Document Server

    Oldeman, R G C; Saitta, B

    2009-01-01

    Antineutrino induced electron capture is a resonant process that can have a larg e cross-section for beams of monochromatic antineutrinos. We calculate the cross-section of this process and investigate an experimental setup where monochromatic antineutrinos are produced from the bound-beta decay of fully ionized radioactive atoms in a storage ring. If the energy between the source and the target is well matched, the cross-sections can be significantly larger than the cross-sections of commonly used non-resonant processes. The rate that can be achieved at a small distance between the source and two targets of $10^3$ kg is up to one interaction per $8 .3\\cdot10^{18}$ decaying atoms. For a source-target distance corresponding to the first atmospheric neutrino osc illation maximum, the largest rate is one interaction per $3.2\\cdot10^{21}$ decaying atoms.

  9. Test beam results of a low-pressure micro-strip gas chamber with a secondary-electron emitter

    Energy Technology Data Exchange (ETDEWEB)

    Kwan, S.; Anderson, D.F.; Zimmerman, J. [Fermi National Accelerator Lab., Batavia, IL (United States); Sbarra, C. [Istituto Nazionale di Fisica Nucleare, Pisa (Italy); Salomon, M. [TRIUMF, Vancouver, BC (Canada)

    1994-10-01

    We present recent results, from a beam test, on the angular dependence of the efficiency and the distribution of the signals on the anode strips of a low-pressure microstrip gas chamber with a thick CsI layer as a secondary-electron emitter. New results of CVD diamond films as secondary-electron emitters are discussed.

  10. Low-energy electron irradiation of preheated and gas-exposed single-wall carbon nanotubes

    Science.gov (United States)

    Ecton, P. A.; Beatty, J.; Verbeck, G.; Lakshantha, W.; Rout, B.; Perez, J. M.

    2016-11-01

    We investigate the conditions under which electron irradiation at 2 keV of single-wall carbon nanotube (SWCNT) bundles produces an increase in the Raman D peak. We find that irradiation of SWCNTs that are preheated in situ at 600 °C for 1 h in ultrahigh vacuum before irradiation does not result in an increase in the D peak. Irradiation of SWCNTs that are preheated in vacuum and then exposed to air or gases results in an increase in the D peak, suggesting that adsorbates play a role in the increase in the D peak. Small diameter SWCNTs that are not preheated or preheated and then exposed to air show a significant increase in the D and G bands after irradiation. X-ray photoelectron spectroscopy shows no chemical shifts in the C 1s peak of SWCNTs that have been irradiated versus SWCNTs that have not been irradiated, suggesting that chemisorption of adsorbates is not responsible for the increase in the D peak.

  11. Low-energy electron irradiation of preheated and gas-exposed single-wall carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Ecton, P.A. [Department of Physics, University of North Texas, Denton, TX 76203 (United States); Beatty, J.; Verbeck, G. [Department of Chemistry, University of North Texas, Denton, TX 76203 (United States); Lakshantha, W.; Rout, B. [Department of Physics, University of North Texas, Denton, TX 76203 (United States); Perez, J.M., E-mail: jperez@unt.edu [Department of Physics, University of North Texas, Denton, TX 76203 (United States)

    2016-11-30

    Highlights: • Preheating SWCNTs in situ before irradiation prevents an increase in the D peak. • Preheated SWCNTs exposed to air or gases before irradiation show an increase in D peak. • The increase in D peak is not due to irradiation-induced chemisorption of adsorbates. • The effects are more significant for small diameter SWCNTs. • The increase in D peak is attributed to defects that increase inter-tube interactions. - Abstract: We investigate the conditions under which electron irradiation at 2 keV of single-wall carbon nanotube (SWCNT) bundles produces an increase in the Raman D peak. We find that irradiation of SWCNTs that are preheated in situ at 600 °C for 1 h in ultrahigh vacuum before irradiation does not result in an increase in the D peak. Irradiation of SWCNTs that are preheated in vacuum and then exposed to air or gases results in an increase in the D peak, suggesting that adsorbates play a role in the increase in the D peak. Small diameter SWCNTs that are not preheated or preheated and then exposed to air show a significant increase in the D and G bands after irradiation. X-ray photoelectron spectroscopy shows no chemical shifts in the C 1s peak of SWCNTs that have been irradiated versus SWCNTs that have not been irradiated, suggesting that chemisorption of adsorbates is not responsible for the increase in the D peak.

  12. Numerical analysis of the surface-conduction electron-emitter with a new configuration

    Science.gov (United States)

    Shen, Zhihua; Wang, Xiao; Wu, Shengli; Tian, Jinshou

    2016-04-01

    A new kind of surface-conduction electron-emitter (SCE) with a triangular dielectric layer under the conductive film is proposed. The influences of the vertex angle (𝜃) of the triangular dielectric layer and the anode voltage (Ua) on the electron emission efficiency and the focusing capability have been investigated with the finite integration technique (FIT). The numerical simulation results show that SCE with a small vertex angle guarantees higher electron emission efficiency even with a low anode voltage. But the focusing capability of the electron emitter will get worse when the 𝜃 or Ua becomes too small. Take both the electron emission efficiency and focusing capability into consideration, the structure with a vertex angle (𝜃) between 60∘-100∘ and the anode voltage of 1500V is suggested.

  13. Will climate change increase ozone depletion from low-energy-electron precipitation?

    Directory of Open Access Journals (Sweden)

    A. J. G. Baumgaertner

    2010-10-01

    Full Text Available We investigate the effects of a strengthened stratospheric/mesospheric residual circulation on the transport of nitric oxide (NO produced by energetic particle precipitation. During periods of high geomagnetic activity, energetic electron precipitation (EEP is responsible for winter time ozone loss in the polar middle atmosphere between 1 and 6 hPa. However, as climate change is expected to increase the strength of the Brewer-Dobson circulation including extratropical downwelling, the enhancements of EEP NOx concentrations are expected to be transported to lower altitudes in extratropical regions, becoming more significant in the ozone budget. Changes in the mesospheric residual circulation are also considered. We use simulations with the chemistry climate model system EMAC to compare present day effects of EEP NOx with expected effects in a climate change scenario for the year 2100. In years of strong geomagnetic activity, similar to that observed in 2003, an additional polar ozone loss of up to 0.4 μmol/mol at 5 hPa is found in the Southern Hemisphere. However, this would be approximately compensated by an ozone enhancement originating from a stronger poleward transport of ozone from lower latitudes caused by a strengthened Brewer-Dobson circulation, as well as by slower photochemical ozone loss reactions in a stratosphere cooled by risen greenhouse gas concentrations. In the Northern Hemisphere the EEP NOx effect appears to lose importance due to the different nature of the climate-change induced circulation changes.

  14. Study of spatial homogeneity and nitridation of an Al nanopattern template with spectroscopic photoemission and low energy electron microscopy

    Science.gov (United States)

    Qi, B.; Ólafsson, S.; Zakharov, A. A.; Göthelid, M.; Agnarsson, B.; Gislason, H. P.

    2013-01-01

    We report a study on the spatial homogeneity and nitridation of a nanopattern template using a spectroscopic photoemission and low energy electron microscopy. The template was composed of Al nanodots which were patterned into a SiO2/Si(1 1 1) surface using e-beam lithography and reactive ion etching. The template exhibited a global inhomogeneity in terms of the local topography, Al composition and structure of the individual nanopatterns. After nitridation, the individual nanopatterns were diminished, more corrugated and faceted. The nitridated nanopatterns were structurally ordered but differently orientated. The nitridation effectively removed the fluorine contaminants by decomposition of the fluorocarbon sidewalls, resulting in the AlN nanopatterns and partially nitridated Si substrate surface outside the nanopattern domains.

  15. Charge Exchange in Low-Energy H, D + C4+ Collisions with Full Account of Electron Translation

    Directory of Open Access Journals (Sweden)

    N. Vaeck

    2002-03-01

    Full Text Available We report the application of the quantum approach, which takes full account of electron translation at low collisional energies, to the charge exchange process H, D + C4+ → H+, D+ + C3+(3s; 3p; 3d. The partial and the total integral cross sections of the process are calculated in the energy range from 1 till 60 eV/amu. It is shown that the present results are independent from the upper integration limit for numerical solution of the coupled channel equations although nonadiabatic couplings remain nonzero up to infinity. The calculated partial and total cross sections are in agreement with the previous low-energy calculations and the available experimental data. It is shown that for low collisional energies the isotopic effect takes place. The observed effect is explained in terms of the nonadiabatic dynamics.

  16. Low Energy High Brilliance Beam Characterization

    CERN Document Server

    Bähr, J

    2005-01-01

    Low energy high brilliance beam characterization plays an important role for electron sources and injectors of Free Electron Lasers (FELs) and electron linear accelerators as for example the future ILC project. The topic is discussed basing on solutions of the PITZ facility (PhotoInjector Test facility Zeuthen) which are compared with methods applied at other facilities. The properties of an electron beam produced at a laser-driven rf-gun is mainly influenced also by characteristics of the laser beam and the electron gun itself. Therefore aspects of diagnostics will be also discussed for the laser, laser beam line and gun as well. The main properties of the electron beam are transverse and longitudinal phase space and charge as well. The measurement of transverse beam size and position, transverse emittance, charge, beam current, and longitudinal phase space will be discussed in detail. The measurements of the transverse emittance at PITZ is based on a single slit method. The measurement of the longitudinal p...

  17. Surface-conduction electron-emitter characteristics and fabrication based on vertically aligned carbon nanotube arrays

    Science.gov (United States)

    Shih, Yi-Ting; Li, Kuan-Wei; Honda, Shin-ichi; Lin, Pao-Hung; Huang, Ying-Sheng; Lee, Kuei-Yi

    2017-06-01

    The carbon nanotube (CNT) has replaced palladium oxide (PdO) as the electrode material for surface-conduction electron-emitter (SCE) applications. Vertically aligned CNT arrays with a delta-star arrangement were patterned and synthesized onto a quartz substrate using photolithography and thermal chemical vapor deposition. Delta-star shaped VACNT arrays with 20° tips are used as cathodes that easily emit electrons because of their high electrical field gradient. In order to improve the field emission and secondary electrons (SEs) in SCE applications, magnesium oxide (MgO) nanostructures were coated onto the VACNT arrays to promote the surface-conduction electron-emitter display (SED) efficiency (η). According to the definition of η in SCE applications, in this study, the η was stably maintained in the 75-85% range. The proposed design provides a facile new method for developing SED applications.

  18. A first-order matrix approach to the analysis of electron beam emittance growth caused by coherent synchrotron radiation

    CERN Document Server

    Hajima, R

    2003-01-01

    A first-order transform matrix is proposed for calculating electron beam emittance dilution arising from coherent synchrotron radiation (CSR) in a next-generation light source based on an energy-recovery linac. The matrix approach enables us to scan numerous parameters for the design of achromatic cells of minimum emittance dilution. The emittance dilution can be minimized when the envelope of CSR wake dispersion matches the betatron function envelope at the achromatic cell exit. (author)

  19. Holography and coherent diffraction with low-energy electrons: A route towards structural biology at the single molecule level.

    Science.gov (United States)

    Latychevskaia, Tatiana; Longchamp, Jean-Nicolas; Escher, Conrad; Fink, Hans-Werner

    2015-12-01

    The current state of the art in structural biology is led by NMR, X-ray crystallography and TEM investigations. These powerful tools however all rely on averaging over a large ensemble of molecules. Here, we present an alternative concept aiming at structural analysis at the single molecule level. We show that by combining electron holography and coherent diffraction imaging estimations concerning the phase of the scattered wave become needless as the phase information is extracted from the data directly and unambiguously. Performed with low-energy electrons the resolution of this lens-less microscope is just limited by the De Broglie wavelength of the electron wave and the numerical aperture, given by detector geometry. In imaging freestanding graphene, a resolution of 2Å has been achieved revealing the 660.000 unit cells of the graphene sheet from a single data set. Once applied to individual biomolecules the method shall ultimately allow for non-destructive imaging and imports the potential to distinguish between different conformations of proteins with atomic resolution.

  20. Holography and Coherent Diffraction with Low-Energy Electrons: A Route towards Structural Biology at the Single Molecule Level

    CERN Document Server

    Latychevskaia, Tatiana; Escher, Conrad; Fink, Hans-Werner

    2014-01-01

    The current state of the art in structural biology is led by NMR, X-ray crystallography and TEM investigations. These powerful tools however all rely on averaging over a large ensemble of molecules. Here, we present an alternative concept aiming at structural analysis at the single molecule level. We show that by combining electron holography and coherent diffraction imaging estimations concerning the phase of the scattered wave become needless as the phase information is extracted from the data directly and unambiguously. Performed with low-energy electrons the resolution of this lens-less microscope is just limited by the De Broglie wavelength of the electron wave and the numerical aperture, given by detector geometry. In imaging freestanding graphene, a resolution of 2 Angstrom has been achieved revealing the 660.000 unit cells of the graphene sheet from one data set at once. Applied to individual biomolecules the method allows for non-destructive imaging and imports the potential to distinguish between di...

  1. Fabrication and characterization of silver nanoparticles by using a low energy electron accelerator with a flow reactor

    Science.gov (United States)

    Kim, Byungnam; Park, Ji Hyun; Lee, Ho Sang; Kim, Myung Man

    2016-10-01

    The mass production of silver nanoparticles by using a low-energy-electron accelerator with a flow reactor was carried out. The flux of the silver precursor was 55 ml/min, and the electron beam's conditions were a fixed beam energy of 0.2 MeV and a beam current of 1 mA. The irradiation area and time were 8 cm × 2 cm and 9.7 seconds, respectively. The yield of silver nanoparticles was about 26.67% in a flow reactor. On the other hand, the yield of silver nanoparticles was around 9% in a batch reactor. Scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and X-ray photoelectron spectroscopy (XPS) showed a synthesis of pure silver nano particles whose surfaces were not oxidized. The size distribution of the fabricated silver nanoparticles was very uniform with sizes from 40 to 50 nm, and the sheet resistance measured using a four-point probe was lower than 3.5 mΩ/sq.

  2. Efficacy of soft-electron (low-energy electron) treatment for disinfestation of brown rice containing different ages of the maize weevil, Sitophilus zeamais Motschulsky

    Science.gov (United States)

    Imamura, Taro; Todoriki, Setsuko; Miyanoshita, Akihiro; Horigane, Akemi K.; Yoshida, Mitsuru; Hayashi, Toru

    2009-07-01

    Soft electrons (low-energy electrons) have been reported to effectively disinfest grains contaminated with stored-product insects. In this study, brown rice grains infested with different ages of the maize weevil, Sitophilus zeamais Motschulsky, were exposed to soft electrons. Soft electrons at an acceleration voltage of 170 kV effectively inactivated eggs, old larvae and pupae of the maize weevil, but could not completely inactivate young larvae. The locations of young larvae in rice grains were specified by magnetic resonance microimaging. Most of the larvae resided at the periphery of the grains while only a few at the center, which were assumed to get out of inactivation. This indicated that soft electrons with low penetration capacity could reach the most of weevil larvae in grains. Combination of soft-electron treatment and short time-low-dose phosphine fumigation achieved high mortality rate of S. zeamais.

  3. Efficacy of soft-electron (low-energy electron) treatment for disinfestation of brown rice containing different ages of the maize weevil, Sitophilus zeamais Motschulsky

    Energy Technology Data Exchange (ETDEWEB)

    Imamura, Taro [National Food Research Institute, NARO Kannondai, Tsukuba, Ibaraki 305-8642 (Japan)], E-mail: taroi@affrc.go.jp; Todoriki, Setsuko; Miyanoshita, Akihiro; Horigane, Akemi K.; Yoshida, Mitsuru; Hayashi, Toru [National Food Research Institute, NARO Kannondai, Tsukuba, Ibaraki 305-8642 (Japan)

    2009-07-15

    Soft electrons (low-energy electrons) have been reported to effectively disinfest grains contaminated with stored-product insects. In this study, brown rice grains infested with different ages of the maize weevil, Sitophilus zeamais Motschulsky, were exposed to soft electrons. Soft electrons at an acceleration voltage of 170 kV effectively inactivated eggs, old larvae and pupae of the maize weevil, but could not completely inactivate young larvae. The locations of young larvae in rice grains were specified by magnetic resonance microimaging. Most of the larvae resided at the periphery of the grains while only a few at the center, which were assumed to get out of inactivation. This indicated that soft electrons with low penetration capacity could reach the most of weevil larvae in grains. Combination of soft-electron treatment and short time-low-dose phosphine fumigation achieved high mortality rate of S. zeamais.

  4. Temperature effect on the electron emission and charging of BN–SiO{sub 2} under low energy electron irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Belhaj, M., E-mail: Mohamed.Belhaj@onera.fr [The French Aerospace Lab, FR-31055 (France); Guerch, K.; Sarrailh, P. [The French Aerospace Lab, FR-31055 (France); Arcis, N. [CNES, 18 Avenue Édouard Belin, 31400 Toulouse (France)

    2015-11-01

    The BN–SiO{sub 2} is widely used as canal material in Hall Effect Thrusters. The electron emission yield under electron impact is considered as a key material parameter that affects the thrust efficiency. The effect of the temperature on the electron emission yield of BN–SiO{sub 2} was investigated. It is found that, the electron emission drop significantly when the temperature is increased from 22 °C to 800 °C. The aim here is to report our experimental results and to discuss the representativeness of electron emission data measured on ceramics at room temperature.

  5. The comparison of DNA damage induced by micro DBD plasma and low energy electron for curing human diseases

    Science.gov (United States)

    Park, Yeunsoo

    2015-09-01

    It is well known that low energy electrons (LEE, especially below 10 eV) can generate DNA damage via indirect action named dissociative electron attachment (DEA). We can now explain some parts of the exact mechanism on DNA damage by LEE collision with direct ionization effect when cancer patients get the radiotherapy. It is kind of remarkable information in the field of radiation therapy. However, it is practically very difficult to directly apply this finding to human disease cure due to difficulty of LEE therapy actualization and request of further clinical studies. Recently, there is a novel challenge in plasma application, that is, how we can apply plasma technology to diagnosis and treatment of many serious diseases like cancer. Cold atmospheric pressure plasma (CAPP) is a very good source to apply to plasma medicine and bio-applications because of low temperature, low cost, and easy handling. Some scientists have already reported good results related to clinical plasma application. The purposes of this study are to further find out exact mechanisms of DNA damage by LEE at the molecular level, to verify new DNA damage like structural alteration on DNA subunits and to compare DNA damage by LEE and plasma source. We will keep expanding our study to DNA damage by plasma source to develop plasma-based new medical and biological applications. We will show some recent results, DNA damage by LEE and non-thermal plasma.

  6. Sub-5 nm graphene nanopore fabrication by nitrogen ion etching induced by a low-energy electron beam.

    Science.gov (United States)

    Fox, Daniel S; Maguire, Pierce; Zhou, Yangbo; Rodenburg, Cornelia; O'Neill, Arlene; Coleman, Jonathan N; Zhang, Hongzhou

    2016-05-13

    A flexible and efficient method to fabricate nanopores in graphene has been developed. A focused, low-energy (5 keV) electron beam was used to locally activate etching of a graphene surface in a low pressure (0.3 Pa) N2 environment. Nanopores with sub-5 nm diameters were fabricated. The lattice structure of the graphene was observed to recover within 20 nm of the nanopore edge. Nanopore growth rates were investigated systematically. The effects of nitrogen pressure, electron beam dwell time and beam current were characterised in order to understand the etching mechanism and enable optimisation of the etching parameters. A model was developed which describes how the diffusion of ionised nitrogen affects the nanopore growth rate. Etching of other two-dimensional materials was attempted as demonstrated with MoS2. The lack of etching observed supports our model of a chemical reaction-based mechanism. The understanding of the etching mechanism will allow more materials to be etched by selection of an appropriate ion species.

  7. Direct observation of pure one-electron capture from the target inner shell in low-energy p+Na collisions

    NARCIS (Netherlands)

    Knoop, S; Morgenstern, R; Hoekstra, R

    2004-01-01

    One-electron removal in the p+Na collision system has been investigated at low energy (4-25 keV) by means of recoil ion momentum spectroscopy. The focus will be on the contribution of one-electron capture from the Na 2p inner shell into the hydrogen ground state, thereby leaving the Na+ target ion

  8. Ultrafast transmission electron microscopy using a laser-driven field emitter: femtosecond resolution with a high coherence electron beam

    CERN Document Server

    Feist, Armin; da Silva, Nara Rubiano; Danz, Thomas; Möller, Marcel; Priebe, Katharina E; Domröse, Till; Gatzmann, J Gregor; Rost, Stefan; Schauss, Jakob; Strauch, Stefanie; Bormann, Reiner; Sivis, Murat; Schäfer, Sascha; Ropers, Claus

    2016-01-01

    We present the development of the first ultrafast transmission electron microscope (UTEM) driven by localized photoemission from a field emitter cathode. We describe the implementation of the instrument, the photoemitter concept and the quantitative electron beam parameters achieved. Establishing a new source for ultrafast TEM, the G\\"ottingen UTEM employs nano-localized linear photoemission from a Schottky emitter, which enables operation with freely tunable temporal structure, from continuous wave to femtosecond pulsed mode. Using this emission mechanism, we achieve record pulse properties in ultrafast electron microscopy of 9 {\\AA} focused beam diameter, 200 fs pulse duration and 0.6 eV energy width. We illustrate the possibility to conduct ultrafast imaging, diffraction, holography and spectroscopy with this instrument and also discuss opportunities to harness quantum coherent interactions between intense laser fields and free electron beams.

  9. Emission of correlated electron pairs from Au(111) and Cu(111) surfaces under low-energy electron impact: Contribution of surface states, d-states and spin effects

    Energy Technology Data Exchange (ETDEWEB)

    Samarin, S., E-mail: samar@physics.uwa.edu.au [Centre for Atomic, Molecular and Surface Physics, University of Western Australia, Perth, WA 6009 (Australia); Research Institute of Physics, St. Petersburg University, St. Petersburg (Russian Federation); Artamonov, O.M. [Research Institute of Physics, St. Petersburg University, St. Petersburg (Russian Federation); Guagliardo, P. [Centre for Microscopy, Characterisation and Analysis, UWA, Perth (Australia); Pravica, L. [Centre for Atomic, Molecular and Surface Physics, University of Western Australia, Perth, WA 6009 (Australia); Baraban, A. [Research Institute of Physics, St. Petersburg University, St. Petersburg (Russian Federation); Schumann, F.O. [Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle (Germany); Williams, J.F. [Centre for Atomic, Molecular and Surface Physics, University of Western Australia, Perth, WA 6009 (Australia)

    2015-01-15

    Highlights: • Spin-polarized two-electron spectroscopy (e,2e) was applied for studying surface states on Cu(111) and Au(111). • Relative (to d-states) contribution of surface states in the (e,2e) spectrum decreases exponentially when primary electron energy increases from 14 to 30 eV. • Spin asymmetry is readily observed in the spectra of Au(111) whereas in the spectra of Cu(111) the spin effect is negligible. - Abstract: The emission of correlated electron pairs excited from surfaces of Au(111) and Cu(111) by low-energy electrons is measured and analyzed. Energy and momentum conservation allows identification of electron pairs involving excitation of electrons from Shockley surface states and from valence d-states. The relative contributions of surface and d-states to the measured spectra of correlated electron pairs is shown to depend on the primary electron energy and is larger from surface states at relatively small primary energies. The use of a spin-polarized incident electron beam highlights the spin effects in producing an electron pair. Measurements show that spin effects are larger for the pair excitation from the valence d-states than for pairs excited from the surface states.

  10. Suppression of Emittance Growth Using a Shaped Cold Atom Electron and Ion Source

    Science.gov (United States)

    Thompson, D. J.; Murphy, D.; Speirs, R. W.; van Bijnen, R. M. W.; McCulloch, A. J.; Scholten, R. E.; Sparkes, B. M.

    2016-11-01

    We demonstrate precise control of charged particle bunch shape with a cold atom electron and ion source to create bunches with linear and, therefore, reversible Coulomb expansion. Using ultracold charged particles enables detailed observation of space-charge effects without loss of information from thermal diffusion, unambiguously demonstrating that shaping in three dimensions can result in a marked reduction of Coulomb-driven emittance growth. We show that the emittance growth suppression is accompanied by an increase in bunch focusability and brightness, improvements necessary for the development of sources capable of coherent single-shot ultrafast electron diffraction of noncrystalline objects, with applications ranging from femtosecond chemistry to materials science and rational drug design.

  11. Adsorption geometry of glycine on Cu(001) determined with low-energy electron diffraction and scanning tunnelling microscopy

    Institute of Scientific and Technical Information of China (English)

    葛四平; 赵学应; 盖峥; 赵汝光; 杨威生

    2002-01-01

    Using low-energy electron diffraction (LEED) and scanning tunnelling microscopy (STM) it has been found thatglycine molecules adsorbed on Cu(001) can form but only the (2×4) and c(2×4) superstructures. On the basis of themissing LEED spots of the surface, it has been concluded that: each (2 ×4) unit cell consists of two molecules, one beingthe mirror image of the other; the C-C axis of both molecules lies in the mirror plane of the Cu substrate without asignificant shift and twist from the plane; and the two O atoms of the carboxylate group of both molecules locate at thesame height level without significant buckling. According to these conclusions, a structural model has been proposed forthe (2×4) superstructure (a model for the c(2×4) superstructure already exists). We argue that the (2×4) and c(2×4)superstructures must have similar specific surface free energy, that their hydrogen bonds must be of N-H-OⅡ type, andthat their local adsorption geometry must be similar or even the same. The advantage of combining STM with LEEDto determine surface structures is clearly demonstrated.

  12. Modeling and Simulation of Longitudinal Dynamics for Low Energy Ring_High Energy Ring at the Positron-Electron Project

    Energy Technology Data Exchange (ETDEWEB)

    Rivetta, Claudio; Mastorides, T.; Fox, J.D.; Teytelman, D.; Van Winkle, D.; /SLAC

    2007-03-06

    A time domain dynamic modeling and simulation tool for beam-cavity interactions in the Low Energy Ring (LER) and High Energy Ring (HER) at the Positron-Electron Project (PEP-II) is presented. Dynamic simulation results for PEP-II are compared to measurements of the actual machine. The motivation for this tool is to explore the stability margins and performance limits of PEP-II radio-frequency (RF) systems at future higher currents and upgraded RF configurations. It also serves as a test bed for new control algorithms and can define the ultimate limits of the low-level RF (LLRF) architecture. The time domain program captures the dynamic behavior of the beam-cavity-LLRF interaction based on a reduced model. The ring current is represented by macrobunches. Multiple RF stations in the ring are represented via one or two macrocavities. Each macrocavity captures the overall behavior of all the 2 or 4 cavity RF stations. Station models include nonlinear elements in the klystron and signal processing. This enables modeling the principal longitudinal impedance control loops interacting via the longitudinal beam model. The dynamics of the simulation model are validated by comparing the measured growth rates for the LER with simulation results. The simulated behavior of the LER at increased operation currents is presented via low-mode instability growth rates. Different control strategies are compared and the effects of both the imperfections in the LLRF signal processing and the nonlinear drivers and klystrons are explored.

  13. System for transporting an electron beam to the atmosphere for a gun with a plasma emitter

    Science.gov (United States)

    Kornilov, S. Yu.; Rempe, N. G.; Shidlovskiy, S. V.

    2016-06-01

    We report on the results of simulation of the gas flow in a gun with a plasma emitter and in the system for extracting the electron beam to the atmosphere, constructed on the basis of standard gasdynamic windows (GDWs). The design of the gun and GDWs is described. Calculations are performed for a pressure of about 10-3 Torr in the electron beam generation range. It is shown that the pressure drop to the atmospheric pressure in the system of electron beam extraction to the atmosphere can be ensured by two GDW stages evacuated by pumps with optimal performance.

  14. A comparison of the relative biological effectiveness of low energy electronic brachytherapy sources in breast tissue: a Monte Carlo study

    Science.gov (United States)

    White, Shane A.; Reniers, Brigitte; de Jong, Evelyn E. C.; Rusch, Thomas; Verhaegen, Frank

    2016-01-01

    Electronic brachytherapy sources use low energy photons to treat the tumor bed during or after breast-conserving surgery. The relative biological effectiveness of two electronic brachytherapy sources was explored to determine if spectral differences due to source design influenced radiation quality and if radiation quality decreased with distance in the breast. The RBE was calculated through the number of DNA double strand breaks (RBEDSB) using the Monte Carlo damage simulator (MCDS) in combination with other Monte Carlo electron/photon spectrum calculations. 50kVp photons from the Intrabeam (Carl Zeiss Surgical) and Axxent (Xoft) through 40-mm spherical applicators were simulated to account for applicator and tissue attenuation in a variety of breast tissue compositions. 40kVp Axxent photons were also simulated. Secondary electrons (known to be responsible for most DNA damage) spectra at different distance were inputted into MCDS to calculate the RBEDSB. All RBEDSB used a cobalt-60 reference. RBEDSB data was combined with corresponding average photon spectrum energy for the Axxent and applied to model-based average photon energy distributions to produce an RBEDSB map of an accelerated partial breast irradiation (APBI) patient. Both Axxent and Intrabeam 50kVp spectra were shown to have a comparable RBEDSB of between 1.4 and 1.6 at all distances in spite of progressive beam hardening. The Axxent 40kVp also demonstrated a similar RBEDSB at distances. Most RBEDSB variability was dependent on the tissue type as was seen in rib (RBEDSB  ≈  1.4), gland (≈1.55), adipose (≈1.59), skin (≈1.52) and lung (≈1.50). RBEDSB variability between both sources was within 2%. A correlation was shown between RBEDSB and average photon energy and used to produce an RBEDSB map of a dose distribution in an APBI patient dataset. Radiation quality is very similar between electronic brachytherapy sources studied. No significant reductions in RBEDSB were observed with

  15. A low energy electron microscopy study of the initial growth, structure, and thermal stability of 4,4{sup '}-biphenyldicarboxylic acid domains on Cu(001)

    Energy Technology Data Exchange (ETDEWEB)

    Khokhar, Fawad S.; Gastel, Raoul van; Schwarz, Daniel; Zandvliet, Harold J. W.; Poelsema, Bene [Physics of Interfaces and Nanomaterials, MESA Institute for Nanotechnology, University of Twente, P.O. Box 217, NL-7500AE Enschede (Netherlands)

    2011-09-28

    The growth of 4,4{sup '}-biphenyldicarboxylic acid (BDA) on Cu(001) has been studied using low energy electron microscopy and selective area low energy electron diffraction. The emergence of large islands and hydrogen bonding to perpendicularly oriented, adjacent molecules is confirmed. The two benzene rings of adsorbed BDA are twisted along the molecular axis. Unconventional growth of the domains, followed by a second nucleation stage, is observed at room temperature. This unanticipated feature is attributed to the accumulation of stress in the islands. Ostwald ripening in the films and the decay of BDA domains at 448 K exhibits features that are consistent with diffusion limited behavior.

  16. A low energy electron microscopy study of the initial growth, structure, and thermal stability of 4,4'-biphenyldicarboxylic acid domains on Cu(001)

    Science.gov (United States)

    Khokhar, Fawad S.; van Gastel, Raoul; Schwarz, Daniel; Zandvliet, Harold J. W.; Poelsema, Bene

    2011-09-01

    The growth of 4,4'-biphenyldicarboxylic acid (BDA) on Cu(001) has been studied using low energy electron microscopy and selective area low energy electron diffraction. The emergence of large islands and hydrogen bonding to perpendicularly oriented, adjacent molecules is confirmed. The two benzene rings of adsorbed BDA are twisted along the molecular axis. Unconventional growth of the domains, followed by a second nucleation stage, is observed at room temperature. This unanticipated feature is attributed to the accumulation of stress in the islands. Ostwald ripening in the films and the decay of BDA domains at 448 K exhibits features that are consistent with diffusion limited behavior.

  17. Intrinsic beam emittance of laser-accelerated electrons measured by x-ray spectroscopic imaging.

    Science.gov (United States)

    Golovin, G; Banerjee, S; Liu, C; Chen, S; Zhang, J; Zhao, B; Zhang, P; Veale, M; Wilson, M; Seller, P; Umstadter, D

    2016-04-19

    The recent combination of ultra-intense lasers and laser-accelerated electron beams is enabling the development of a new generation of compact x-ray light sources, the coherence of which depends directly on electron beam emittance. Although the emittance of accelerated electron beams can be low, it can grow due to the effects of space charge during free-space propagation. Direct experimental measurement of this important property is complicated by micron-scale beam sizes, and the presence of intense fields at the location where space charge acts. Reported here is a novel, non-destructive, single-shot method that overcame this problem. It employed an intense laser probe pulse, and spectroscopic imaging of the inverse-Compton scattered x-rays, allowing measurement of an ultra-low value for the normalized transverse emittance, 0.15 (±0.06) π mm mrad, as well as study of its subsequent growth upon exiting the accelerator. The technique and results are critical for designing multi-stage laser-wakefield accelerators, and generating high-brightness, spatially coherent x-rays.

  18. Improvement of electron emission characteristics of porous silicon emitter by using cathode reduction and electrochemical oxidation

    Science.gov (United States)

    Li, He; Wenjiang, Wang; Xiaoning, Zhang

    2017-03-01

    A new simple and convenient post-treat technique combined the cathode reduction (CR) and electrochemical oxidation (ECO) was proposed to improve the electron emission properties of the surface-emitting cold cathodes based on the porous silicon (PS). It is demonstrated here that by introducing this new technique combined CR and ECO, the emission properties of the diode have been significantly improved than those as-prepared samples. The experimental results showed that the emission current densities and efficiencies of sample treated by CR were 62 μA/cm2 and 12.10‰, respectively, nearly 2 orders of magnitude higher than those of as-prepared sample. Furthermore, the CR-treated PS emitter shows higher repeatability and stability compared with the as-prepared PS emitter. The scanning electron microscope (SEM), atomic force microscope (AFM), energy dispersive spectrometer (EDS), furier transformed infrared (FTIR) spectroscopy results indicated that the improved mechanism is mainly due to the passivation of the PS, which not only improve the PS morphology by the passivation of the H+ but also improve the uniformity of the oxygen content distribution in the whole PS layer. Therefore, the method combined the CR treatment and ECO is expected to be a valuable technique to enhance the electron emission characteristics of the PS emitter.

  19. Highly reliable field electron emitters produced from reproducible damage-free carbon nanotube composite pastes with optimal inorganic fillers.

    Science.gov (United States)

    Kim, Jae-Woo; Jeong, Jin-Woo; Kang, Jun-Tae; Choi, Sungyoul; Ahn, Seungjoon; Song, Yoon-Ho

    2014-02-14

    Highly reliable field electron emitters were developed using a formulation for reproducible damage-free carbon nanotube (CNT) composite pastes with optimal inorganic fillers and a ball-milling method. We carefully controlled the ball-milling sequence and time to avoid any damage to the CNTs, which incorporated fillers that were fully dispersed as paste constituents. The field electron emitters fabricated by printing the CNT pastes were found to exhibit almost perfect adhesion of the CNT emitters to the cathode, along with good uniformity and reproducibility. A high field enhancement factor of around 10,000 was achieved from the CNT field emitters developed. By selecting nano-sized metal alloys and oxides and using the same formulation sequence, we also developed reliable field emitters that could survive high-temperature post processing. These field emitters had high durability to post vacuum annealing at 950 °C, guaranteeing survival of the brazing process used in the sealing of field emission x-ray tubes. We evaluated the field emitters in a triode configuration in the harsh environment of a tiny vacuum-sealed vessel and observed very reliable operation for 30 h at a high current density of 350 mA cm(-2). The CNT pastes and related field emitters that were developed could be usefully applied in reliable field emission devices.

  20. Highly reliable field electron emitters produced from reproducible damage-free carbon nanotube composite pastes with optimal inorganic fillers

    Science.gov (United States)

    Kim, Jae-Woo; Jeong, Jin-Woo; Kang, Jun-Tae; Choi, Sungyoul; Ahn, Seungjoon; Song, Yoon-Ho

    2014-02-01

    Highly reliable field electron emitters were developed using a formulation for reproducible damage-free carbon nanotube (CNT) composite pastes with optimal inorganic fillers and a ball-milling method. We carefully controlled the ball-milling sequence and time to avoid any damage to the CNTs, which incorporated fillers that were fully dispersed as paste constituents. The field electron emitters fabricated by printing the CNT pastes were found to exhibit almost perfect adhesion of the CNT emitters to the cathode, along with good uniformity and reproducibility. A high field enhancement factor of around 10 000 was achieved from the CNT field emitters developed. By selecting nano-sized metal alloys and oxides and using the same formulation sequence, we also developed reliable field emitters that could survive high-temperature post processing. These field emitters had high durability to post vacuum annealing at 950 °C, guaranteeing survival of the brazing process used in the sealing of field emission x-ray tubes. We evaluated the field emitters in a triode configuration in the harsh environment of a tiny vacuum-sealed vessel and observed very reliable operation for 30 h at a high current density of 350 mA cm-2. The CNT pastes and related field emitters that were developed could be usefully applied in reliable field emission devices.

  1. Correlation between energy deposition and molecular damage from Auger electrons: A case study of ultra-low energy (5–18 eV) electron interactions with DNA

    Energy Technology Data Exchange (ETDEWEB)

    Rezaee, Mohammad, E-mail: Mohammad.Rezaee@USherbrooke.ca; Hunting, Darel J.; Sanche, Léon [Groupe en Sciences des Radiations, Département de Médecine Nucléaire et Radiobiologie, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4 (Canada)

    2014-07-15

    Purpose: The present study introduces a new method to establish a direct correlation between biologically related physical parameters (i.e., stopping and damaging cross sections, respectively) for an Auger-electron emitting radionuclide decaying within a target molecule (e.g., DNA), so as to evaluate the efficacy of the radionuclide at the molecular level. These parameters can be applied to the dosimetry of Auger electrons and the quantification of their biological effects, which are the main criteria to assess the therapeutic efficacy of Auger-electron emitting radionuclides. Methods: Absorbed dose and stopping cross section for the Auger electrons of 5–18 eV emitted by{sup 125}I within DNA were determined by developing a nanodosimetric model. The molecular damages induced by these Auger electrons were investigated by measuring damaging cross section, including that for the formation of DNA single- and double-strand breaks. Nanoscale films of pure plasmid DNA were prepared via the freeze-drying technique and subsequently irradiated with low-energy electrons at various fluences. The damaging cross sections were determined by employing a molecular survival model to the measured exposure–response curves for induction of DNA strand breaks. Results: For a single decay of{sup 125}I within DNA, the Auger electrons of 5–18 eV deposit the energies of 12.1 and 9.1 eV within a 4.2-nm{sup 3} volume of a hydrated or dry DNA, which results in the absorbed doses of 270 and 210 kGy, respectively. DNA bases have a major contribution to the deposited energies. Ten-electronvolt and high linear energy transfer 100-eV electrons have a similar cross section for the formation of DNA double-strand break, while 100-eV electrons are twice as efficient as 10 eV in the induction of single-strand break. Conclusions: Ultra-low-energy electrons (<18 eV) substantially contribute to the absorbed dose and to the molecular damage from Auger-electron emitting radionuclides; hence, they should

  2. Asymmetrical field emitter

    Science.gov (United States)

    Fleming, J.G.; Smith, B.K.

    1995-10-10

    A method is disclosed for providing a field emitter with an asymmetrical emitter structure having a very sharp tip in close proximity to its gate. One preferred embodiment of the present invention includes an asymmetrical emitter and a gate. The emitter having a tip and a side is coupled to a substrate. The gate is connected to a step in the substrate. The step has a top surface and a side wall that is substantially parallel to the side of the emitter. The tip of the emitter is in close proximity to the gate. The emitter is at an emitter potential, and the gate is at a gate potential such that with the two potentials at appropriate values, electrons are emitted from the emitter. In one embodiment, the gate is separated from the emitter by an oxide layer, and the emitter is etched anisotropically to form its tip and its asymmetrical structure. 17 figs.

  3. Surface structures from low energy electron diffraction: Atoms, small molecules and an ordered ice film on metal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Materer, N.F.

    1995-09-01

    We investigated the surface bonding of various adsorbates (0, S, C{sub 2}H{sub 3} and NO) along with the resulting relaxation of the Pt(111) surface using low energy electron diffiraction (LEED). LEED experiments have been performed on these ordered overlayers along with theoretical structural analysis using automated tensor LEED (ATLEED). The resulting surface structures of these ordered overlayers exhibit similar adsorbate-induced relaxations. In all cases the adsorbate occupies the fcc hollow site and induces an approximately 0.1 A buckling of the metal surface. The three metal atoms directly bonded to the adsorbate are ``pulled`` out of the surface and the metal atom that is not bound to the adsorbate is `pushed`` inward. In order to understand the reliability of such details, we have carried out a comprehensive study of various non-structural parameters used in a LEED computation. We also studied the adsorption of water on the Pt(lll) surface. We ordered an ultra thin ice film on this surface. The film`s surface is found to be the (0001) face of hexagonal ice. This surface is apparently terminated by a full-bilayer, in which the uppermost water molecules have large vibrational amplitudes even at temperatures as low as 90 K. We examined two other metal surfaces besides Pt(111): Ni(111) and Fe(lll). On Ni(111), we have studied the surface under a high coverage of NO. On both Ni(111) and Pt(111) NO molecules occupy the hollow sites and the N-0 bond distances are practically identical. The challenging sample preparation of an Fe(111) surface has been investigated and a successful procedure has been obtained. The small interlayer spacing found on Fe(111) required special treatment in the LEED calculations. A new ATLEED program has been developed to handle this surface.

  4. Measurement of transverse emittance and coherence of double-gate field emitter array cathodes

    Science.gov (United States)

    Tsujino, Soichiro; Das Kanungo, Prat; Monshipouri, Mahta; Lee, Chiwon; Miller, R. J. Dwayne

    2016-12-01

    Achieving small transverse beam emittance is important for high brightness cathodes for free electron lasers and electron diffraction and imaging experiments. Double-gate field emitter arrays with on-chip focussing electrode, operating with electrical switching or near infrared laser excitation, have been studied as cathodes that are competitive with photocathodes excited by ultraviolet lasers, but the experimental demonstration of the low emittance has been elusive. Here we demonstrate this for a field emitter array with an optimized double-gate structure by directly measuring the beam characteristics. Further we show the successful application of the double-gate field emitter array to observe the low-energy electron beam diffraction from suspended graphene in minimal setup. The observed low emittance and long coherence length are in good agreement with theory. These results demonstrate that our all-metal double-gate field emitters are highly promising for applications that demand extremely low-electron bunch-phase space volume and large transverse coherence.

  5. Experimental and theoretical triple-differential cross sections for tetrahydrofuran ionized by low-energy 26-eV-electron impact

    Science.gov (United States)

    Ali, Esam; Ren, XueGuang; Dorn, Alexander; Ning, Chuangang; Colgan, James; Madison, Don

    2016-06-01

    We report an experimental and theoretical study of low-energy electron-impact ionization of tetrahydrofuran, which is a molecule of biological interest. The experiments were performed using an advanced reaction microscope specially built for electron-impact ionization studies. The theoretical calculations were performed within the molecular three-body distorted-wave model. Reasonably good agreement is found between experiment and theory.

  6. Electron emission properties of gated silicon field emitter arrays driven by laser pulses

    Science.gov (United States)

    Shimawaki, Hidetaka; Nagao, Masayoshi; Neo, Yoichiro; Mimura, Hidenori; Wakaya, Fujio; Takai, Mikio

    2016-10-01

    We report optically modulated electron emission from gated p-type silicon field emitter arrays (Si-FEAs). The device's "volcano" structure is designed to control the photoexcitation of electrons by transmitting light through the small gate aperture, thereby minimizing the photogeneration of slow diffusion carriers outside the depletion region in the tip. Compared to that in the dark, the emission current was enhanced by more than three orders of magnitude in the high field region when irradiated with blue laser pulses. Results from the time-resolved measurements of photoassisted electron emission showed that these possess the same response as the laser pulse with no discernible delay. These results indicate that the volcano device structure is effective at eliminating the generation of diffusion carriers and that a fully optimized FEA is promising as a photocathode for producing high-speed modulated electron beams.

  7. Surface reconstruction of hexagonal Y-doped HoMnO3 and LuMnO3 studied using low-energy electron diffraction

    Science.gov (United States)

    Vasić, R.; Sadowski, J. T.; Choi, Y. J.; Zhou, H. D.; Wiebe, C. R.; Cheong, S. W.; Rowe, J. E.; Ulrich, M. D.

    2010-04-01

    We have investigated the (0001) surfaces of several hexagonal manganite perovskites by low-energy electron diffraction (LEED) in order to determine if the surface periodicity is different from that of the bulk materials. These LEED studies were conducted using near-normal incidence geometry with a low energy electron microscope (LEEM)/LEED apparatus from room temperature to 1200°C and with an electron energy in the range of 15-50 eV. Diffraction patterns showed features of bulk-terminated periodicity as well as a 2×2 surface reconstruction. Possible origins for this surface reconstruction structure are discussed and comparisons are made with surface studies of other complex oxides.

  8. Surface Reconstruction of Hexagonal Y-doped HoMnO3 and LuMnO3 Studied using Low-energy Electron Diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Vasic, R.; Sadowski, J; Choi, Y; Zhou, H; Wiebe, C; Cheong, S; Rowe, J; Ulrich, M

    2010-01-01

    We have investigated the (0001) surfaces of several hexagonal manganite perovskites by low-energy electron diffraction (LEED) in order to determine if the surface periodicity is different from that of the bulk materials. These LEED studies were conducted using near-normal incidence geometry with a low energy electron microscope (LEEM)/LEED apparatus from room temperature to 1200 C and with an electron energy in the range of 15-50 eV. Diffraction patterns showed features of bulk-terminated periodicity as well as a 2 x 2 surface reconstruction. Possible origins for this surface reconstruction structure are discussed and comparisons are made with surface studies of other complex oxides.

  9. Radiotoxicity induced by Auger electron emitters in human osteosarcoma cell line using comet assay

    Institute of Scientific and Technical Information of China (English)

    XU Yu-Jie; LI Qing-Nuan; ZHU Ran; ZHU Ben-Xing; ZHANG Yong-Ping; ZHANG Xiao-Dong; FAN Wo; HONG Cheng-Jiao; LI Wen-Xin

    2003-01-01

    The comet assay (single cell gel electrophoresis assay) was used to evaluate the radiotoxicity of Augerelectron emitters in the human osteosarcoma cell line (HOS-8603). After internal exposure to 67Ga-EDTMP, the sar-coma cell has been injured severely. The comet length was longer along with the increase of dose, the appearance ofcomet tail was different from that with respect to the 60Co γ-ray irradiation. DNA damage of cell was mainly due tothe radiation effect of Auger electrons. The 67Ga may be a therapeutic radionuclide with good prospect for tumortreatment and palliation of bone pain induced by metastasis.

  10. Measurements and simulations of ultralow emittance and ultrashort electron beams in the linac coherent light source.

    Science.gov (United States)

    Ding, Y; Brachmann, A; Decker, F-J; Dowell, D; Emma, P; Frisch, J; Gilevich, S; Hays, G; Hering, Ph; Huang, Z; Iverson, R; Loos, H; Miahnahri, A; Nuhn, H-D; Ratner, D; Turner, J; Welch, J; White, W; Wu, J

    2009-06-26

    The Linac Coherent Light Source (LCLS) is an x-ray free-electron laser project presently in a commissioning phase at the SLAC National Accelerator Laboratory. We report here on very low-emittance measurements made at low bunch charge, and a few femtosecond bunch length produced by the LCLS bunch compressors. Start-to-end simulations associated with these beam parameters show the possibilities of generating hundreds of GW at 1.5 A x-ray wavelength and nearly a single longitudinally coherent spike at 1.5 nm with 2-fs duration.

  11. On the possibility of generating low-energy positrons on accelerators of electrons with a beam energy of a few MeV and on terawatt lasers

    Science.gov (United States)

    Gorlova, D. A.; Nedorezov, V. G.; Ivanov, K. A.; Savel'ev, A. B.; Turinge, A. A.; Tsymbalov, I. N.

    2017-06-01

    Based on the numerical simulations, we estimate the possibility of generating positrons by low-energy electrons (below 10 MeV) produced by electron accelerators and femtosecond lasers. A review of experimental work reported in the literature is presented. The simulation is carried out using the GEANT-4 software package for the particular conditions of a possible experiment at the terawatt femtosecond laser facility of the International Laser Centre at the Moscow State University and the LUE-8 MeV linear electron accelerator at the Institute for Nuclear Research, Russian Academy of Sciences.

  12. Low-Energy Electron Diffraction (LEED) Study of an Aperiodic Thin Film of Cu on 5-fold i-Al-Pd-Mn

    OpenAIRE

    Pussi, Katariina; Reid, Dennis; Ferralis, Nicola; McGrath, Ronan; Lograsso, Thomas; Ross, Amy; Diehl, Renee

    2008-01-01

    Abstract Thin films of copper grown on 5-fold i-AlPdMn at room temperature consist of domains that are rotationally aligned with the five primary symmetry directions of the substrate and which have one-dimensional aperiodic order. This aperiodic order is evident in scanning tunneling microscopy (STM) images as wide and narrow rows that are spaced according to a Fibonacci sequence. A low-energy electron diffraction (LEED) study of this film indicates that the structure within the ...

  13. Comment on ``Electron-induced bond breaking at low energies in HCOOH and glycine: The role of very short-lived σ∗ anion states''

    Science.gov (United States)

    Rescigno, T. N.; Trevisan, C. S.; Orel, A. E.

    2009-10-01

    Recent model calculations by Gallup [Phys. Rev. A79, 042710 (2009)] suggest that low-energy dissociative electron attachment to formic acid can be explained solely in terms of a very short-lived σ∗ anion state and that no σ∗/π∗ coupling is required. We argue that this interpretation of the experimental data, which is at odds with our earlier study, is flawed.

  14. Nano-modulated electron beams via electron diffraction and emittance exchange for coherent x-ray generation

    CERN Document Server

    Nanni, Emilio A; Moncton, David E

    2015-01-01

    A new method for generation of relativistic electron beams with current modulations at nanometer scale and below is presented. The current modulation is produced by diffracting relativistic electrons in perfect crystal Si, accelerating the diffracted beam and imaging the crystal structure, then transferring the image into the temporal dimension via emittance exchange. The modulation period can be tuned by adjusting electron optics after diffraction. This tunable longitudinal modulation can have a period as short as a few angstroms, enabling production of coherent hard x-rays from a device based on inverse Compton scattering with total length of a few meters. Electron beam simulations from cathode emission through diffraction, acceleration and image formation with variable magnification are presented along with estimates of the coherent x-ray output properties.

  15. Generation and application of channeling X-rays using a novel, low-emittance electron beam—Status and plans

    Energy Technology Data Exchange (ETDEWEB)

    Gabella, W.E., E-mail: b.gabella@vanderbilt.edu [Department of Physics and Astronomy, Vanderbilt University, Nashville, TN (United States); Brau, C.A. [Department of Physics and Astronomy, Vanderbilt University, Nashville, TN (United States); Choi, B.K. [Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, TN (United States); Ivanov, B.; Jarvis, J.D.; Mendenhall, M.H. [Department of Physics and Astronomy, Vanderbilt University, Nashville, TN (United States); Piot, P.; Mihalcea, D. [Department of Physics, Northern Illinois University, Dekalb, IL (United States); Fermi National Accelerator Laboratory, Batavia, IL (United States); Carrigan, R. [Fermi National Accelerator Laboratory, Batavia, IL (United States); Wagner, W. [Helmholtz Zentrum Dresden-Rossendorf, Institute of Radiation Physics, Dresden (Germany)

    2013-08-15

    We plan to use very small emittance electron beams created from our novel, single tip cathodes to make a channeling-radiation X-ray source for X-ray imaging, especially phase contrast imaging. We calculate that we can preserve the electron emittance from the source to the crystal, and focus to a 40 nm spot on the crystal face for 40 MeV electrons. This yields an X-ray source with good coherence properties. We discuss our plan for experiments at Fermilab with 4.5 MeV electrons at the High Brightness Electron Source Laboratory, and with 40 MeV electrons at the Advanced Superconducting Test Accelerator. We also present the state of our art with cathode construction and testing. Electrons come from the cathodes by field-emission, with the electric field enhanced by geometric properties of a very small, robust diamond tip. This can create an electron beam with very small emittance. We estimate that the normalized emittance of such a beam at the cathode is 3 nm rad. We currently test the cathodes in DC, high-voltage test stands. We will begin experiments placing the cathodes in RF guns in early 2013.

  16. Surface Reconstruction of Hexagonal Y-doped HoMnO3 and LuMnO3 Studied Using Low-energy Electron Diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Vasic, R.; Sadowski, J.

    2010-04-15

    We have investigated the (0001) surfaces of several hexagonal manganite perovskites by low-energy electron diffraction (LEED) in order to determine if the surface periodicity is different from that of the bulk materials. These LEED studies were conducted using near-normal incidence geometry with a low energyelectron microscope (LEEM)/LEED apparatus from room temperature to 1200 degrees C and with an electron energy in the range of 15-50 eV. Diffraction patterns showed features of bulk-terminated periodicity as well as a 2 2 surface reconstruction. Possible origins for this surface reconstruction structure are discussed and comparisons are made with surface studies of other complex oxides.

  17. Comparison of TG-43 and TG-186 in breast irradiation using a low energy electronic brachytherapy source

    Energy Technology Data Exchange (ETDEWEB)

    White, Shane A.; Landry, Guillaume; Reniers, Brigitte, E-mail: brigitte.reniers@maastro.nl [Department of Radiation Oncology (MAASTRO), GROW School for Oncology and Developmental Biology, Maastricht University Medical Center (MUMC), Maastricht 6201 BN (Netherlands); Fonseca, Gabriel Paiva [Department of Radiation Oncology (MAASTRO), GROW School for Oncology and Developmental Biology, Maastricht University Medical Center (MUMC), Maastricht 6201 BN, The Netherlands and Instituto de Pesquisas Energéticas e Nucleares – IPEN-CNEN/SP, São Paulo CP 11049, 05422-970 (Brazil); Holt, Randy; Rusch, Thomas [Xoft, A Subsidiary of iCAD, Sunnyvale, California 94085-4115 (United States); Beaulieu, Luc [Centre Hospitalier Universitaire de Québec Université Laval, Radio-Oncologie et Centre de Recherche en Cancérologie de l’Université Laval, Québec, Québec G1R 2J6 Canada (Canada); Verhaegen, Frank [Department of Radiation Oncology (MAASTRO), GROW School for Oncology and Developmental Biology, Maastricht University Medical Center (MUMC), Maastricht 6201 BN, The Netherlands and Department of Oncology, McGill University, Montreal, Quebec H3G 1A4 (Canada)

    2014-06-15

    Purpose: The recently updated guidelines for dosimetry in brachytherapy in TG-186 have recommended the use of model-based dosimetry calculations as a replacement for TG-43. TG-186 highlights shortcomings in the water-based approach in TG-43, particularly for low energy brachytherapy sources. The Xoft Axxent is a low energy (<50 kV) brachytherapy system used in accelerated partial breast irradiation (APBI). Breast tissue is a heterogeneous tissue in terms of density and composition. Dosimetric calculations of seven APBI patients treated with Axxent were made using a model-based Monte Carlo platform for a number of tissue models and dose reporting methods and compared to TG-43 based plans. Methods: A model of the Axxent source, the S700, was created and validated against experimental data. CT scans of the patients were used to create realistic multi-tissue/heterogeneous models with breast tissue segmented using a published technique. Alternative water models were used to isolate the influence of tissue heterogeneity and backscatter on the dose distribution. Dose calculations were performed using Geant4 according to the original treatment parameters. The effect of the Axxent balloon applicator used in APBI which could not be modeled in the CT-based model, was modeled using a novel technique that utilizes CAD-based geometries. These techniques were validated experimentally. Results were calculated using two dose reporting methods, dose to water (D{sub w,m}) and dose to medium (D{sub m,m}), for the heterogeneous simulations. All results were compared against TG-43-based dose distributions and evaluated using dose ratio maps and DVH metrics. Changes in skin and PTV dose were highlighted. Results: All simulated heterogeneous models showed a reduced dose to the DVH metrics that is dependent on the method of dose reporting and patient geometry. Based on a prescription dose of 34 Gy, the average D{sub 90} to PTV was reduced by between ∼4% and ∼40%, depending on the

  18. Flexible control of femtosecond pulse duration and separation using an emittance-spoiling foil in x-ray free-electron lasers

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Y. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Behrens, C. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Coffee, R. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Decker, F. -J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Emma, P. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Field, C. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Helml, W. [Technische Univ. Munchen, Garching (Germany); Huang, Z. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Krejcik, P. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Krzywinski, J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Loos, H. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Lutman, A. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Marinelli, A. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Maxwell, T. J. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Turner, J. [SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2015-06-22

    We report experimental studies of generating and controlling femtosecond x-ray pulses in free-electron lasers (FELs) using an emittance spoiling foil. By selectivity spoiling the transverse emittance of the electron beam, the output pulse duration or double-pulse separation is adjusted with a variable size single or double slotted foil. Measurements were performed with an X-band transverse deflector located downstream of the FEL undulator, from which both the FEL lasing and emittance spoiling effects are observed directly.

  19. Review of rest gas interaction at very low energies applied to the Extra Low Energy Antiproton ring ELENA

    CERN Document Server

    Carli, C; Karamyshev, O; Welsch, C P

    2014-01-01

    The Extremely Low ENergy Antiproton ring (ELENA) is a small synchrotron equipped with an electron cooler, which shall be constructed at CERN to decelerate antiprotons to energies as low as 100 keV. Scattering of beam particles on rest gas molecules may have a detrimental effect at such low energies and leads to stringent vacuum requirements. Within this contribution scattering of the stored beam on rest gas molecules is discussed for very low beam energies. It is important to carefully distinguish between antiprotons scattered out of the acceptance and lost, and those remaining inside the aperture to avoid overestimation of emittance blow-up. Furthermore, many antiprotons do not interact at all during the time they are stored in ELENA and hence this is not a multiple scattering process

  20. Observation of Electron Cloud Instabilities and Emittance Dilution at the Cornell Electron-Positron Storage Ring Test Accelerator

    Science.gov (United States)

    Holtzapple, R. L.; Billing, M. G.; Campbell, R. C.; Dugan, G. F.; Flanagan, J.; McArdle, K. E.; Miller, M. I.; Palmer, M. A.; Ramirez, G. A.; Sonnad, K. G.; Totten, M. M.; Tucker, S. L.; Williams, H. A.

    2016-04-01

    Electron cloud related emittance dilution and instabilities of bunch trains limit the performance of high intensity circular colliders. One of the key goals of the Cornell electron-positron storage ring Test Accelerator (CesrTA) research program is to improve our understanding of how the electron cloud alters the dynamics of bunches within the train. Single bunch beam diagnotics have been developed to measure the beam spectra, vertical beam size, two important dynamical effects of beams interacting with the electron cloud, for bunch trains on a turn-by-turn basis. Experiments have been performed at CesrTA to probe the interaction of the electron cloud with stored positron bunch trains. The purpose of these experiments was to characterize the dependence of beam-electron cloud interactions on the machine parameters such as bunch spacing, vertical chromaticity, and bunch current. The beam dynamics of the stored beam, in the presence of the electron cloud, was quantified using: 1) a gated beam position monitor (BPM) and spectrum analyzer to measure the bunch-by-bunch frequency spectrum of the bunch trains; 2) an x-ray beam size monitor to record the bunch-by-bunch, turn-by-turn vertical size of each bunch within the trains. In this paper we report on the observations from these experiments and analyze the effects of the electron cloud on the stability of bunches in a train under many different operational conditions.

  1. Space Charge Compensation in the Linac4 Low Energy Beam Transport Line with Negative Hydrogen Ions

    CERN Document Server

    Valerio-Lizarraga, C; Leon-Monzon, I; Lettry, J; Midttun, O; Scrivens, R

    2014-01-01

    The space charge effect of low energy, unbunched ion beams can be compensated by the trapping of ions or electrons into the beam potential. This has been studied for the 45 keV negative hydrogen ion beam in the CERN Linac4 Low Energy Beam Tranport (LEBT) using the package IBSimu1, which allows the space charge calculation of the particle trajectories. The results of the beam simulations will be compared to emittance measurements of an H- beam at the CERN Linac4 3 MeV test stand, where the injection of hydrogen gas directly into the beam transport region has been used to modify the space charge compensation degree.

  2. Contribution of the electron-phonon coupling to Lindhard partition at low energy in Ge and Si detectors for astroparticle physics

    CERN Document Server

    Lazanu, Ionel

    2015-01-01

    The influence of the transient thermal effects on the partition of the energy of selfrecoils in germanium and silicon into energy eventually given to electrons and to atomic recoils respectively is studied. The transient effects are treated in the frame of the thermal spike model, which considers the electronic and atomic subsystems coupled through the electron-phonon interaction. For low energies of selfrecoils, we show that the corrections to the energy partition curves due to the energy exchange during the transient processes modify the Lindhard predictions. These effects depend on the initial temperature of the target material, as the energies exchanged between electronic and lattice subsystems have different signs for temperatures lower and higher than about 15 K. More of the experimental data reported in the literature support the model.

  3. Low emittance design of the electron gun and the focusing channel of the Compact Linear Collider drive beam

    Science.gov (United States)

    Dayyani Kelisani, M.; Doebert, S.; Aslaninejad, M.

    2017-04-01

    For the Compact Linear Collider project at CERN, the power for the main linacs is extracted from a drive beam generated from a high current electron source. The design of the electron source and its subsequent focusing channel has a great impact on the beam dynamic considerations of the drive beam. We report the design of a thermionic electron source and the subsequent focusing channels with the goal of production of a high quality beam with a very small emittance.

  4. Low-energy electron diffraction from ferroelectric surfaces: Dead layers and surface dipoles in clean Pb(Zr ,Ti )O 3(001 )

    Science.gov (United States)

    Teodorescu, Cristian M.; Pintilie, Lucian; Apostol, Nicoleta G.; Costescu, Ruxandra M.; Lungu, George A.; Hrib, LuminiÅ£a.; Trupinǎ, Lucian; Tǎnase, Liviu C.; Bucur, Ioana C.; Bocîrnea, Amelia E.

    2017-09-01

    The positions of the low energy electron diffraction (LEED) spots from ferroelectric single crystal films depend on its polarization state, due to electric fields generated outside of the sample. One may derive the surface potential energy, yielding the depth where the mobile charge carriers compensating the depolarization field are located (δ ). On ferroelectric Pb (Zr ,Ti ) O3 (001) samples, surface potential energies are between 6.7 and 10.6 eV, and δ values are unusually low, in the range of 1.8 ±0.4 Å . When δ is introduced in the values of the band bending inside the ferroelectric, a considerably lower value of the dielectric constant and/or of the polarization near the surface than their bulk values is obtained, evidencing either that the intrinsic `dielectric constant' of the material has this lower value or the existence of a `dead layer' at the free surface of clean ferroelectric films. The inwards polarization of these films is explained in the framework of the present considerations by the formation of an electron sheet on the surface. Possible explanations are suggested for discrepancies between the values found for surface potential energies from LEED experiments and those derived from the transition between mirror electron microscopy and low energy electron microscopy.

  5. Low energy ion beam dynamics of NANOGAN ECR ion source

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Sarvesh, E-mail: sarvesh@iuac.res.in; Mandal, A.

    2016-04-01

    A new low energy ion beam facility (LEIBF) has been developed for providing the mass analyzed highly charged intense ion beams of energy ranging from a few tens of keV to a few MeV for atomic, molecular and materials sciences research. The new facility consists of an all permanent magnet 10 GHz electron cyclotron resonance (ECR) ion source (NANOGAN) installed on a high voltage platform (400 kV) which provides large currents of multiply charged ion beams. Higher emittance at low energy of intense ion beam puts a tremendous challenge to the beam optical design of this facility. The beam line consists of mainly the electrostatic quadrupoles, an accelerating section, analyzing cum switching magnet and suitable beam diagnostics including vacuum components. The accelerated ion beam is analyzed for a particular mass to charge (m/q) ratio as well as guided to three different lines along 75°, 90° and 105° using a large acceptance analyzing cum switching magnet. The details of transverse beam optics to all the beam lines with TRANSPORT and GICOSY beam optics codes are being described. Field computation code, OPERA 3D has been utilized to design the magnets and electrostatic quadrupoles. A theoretical estimation of emittance for optimized geometry of ion source is given so as to form the basis of beam optics calculations. The method of quadrupole scan of the beam is used to characterize the emittance of the final beam on the target. The measured beam emittance increases with m/q ratios of various ion beams similar to the trend observed theoretically.

  6. Inelastic scattering and stopping power of low-energy electrons (0.01-10 keV) in toluene.

    Science.gov (United States)

    García, G; Blanco, F; Grau Carles, A; Grau Malonda, A

    2004-01-01

    In this study, the stopping power for electrons in toluene is reported for incident energies ranging from 10 to 10,000 eV. The present results have been obtained by combining the calculated inelastic electron scattering cross-sections with an experimental energy loss procedure. Calculations have been carried out by means of a quasifree absorption model whose reliability has been checked by comparison with empirical electron scattering total cross section data. Results have been compared with the high-energy stopping power data available in the literature. For energies below 1 keV these are the first results of the stopping power for electrons in toluene.

  7. MeV electrons accelerated backward along laser axis from low energy, high intensity laser-water interactions

    CERN Document Server

    Feister, Scott; Morrison, John T; Frische, Kyle D; Orban, Chris; Ngirmang, Gregory; Handler, Abraham; Schillaci, Mark; Chowdhury, Enam A; Freeman, R R; Roquemore, W M

    2015-01-01

    Direct electron spectrum measurements show MeV energy electrons generated backward along the laser axis by a $\\lambda =$ 780 nm, 40 fs, 2.9 mJ short-pulse laser ($1.5 \\cdot 10^{18}$ W/cm$^2$). Electrons pass through a 3 mm hole in the center of the final off-axis paraboloid (OAP) and are characterized by a magnetic spectrometer. The charge collected at the OAP is hundreds of pC per pulse. A mechanism for this super-ponderomotive backward electron acceleration is discussed in the framework of 3D Particle-in-cell simulations.

  8. Emittance exchange results

    Energy Technology Data Exchange (ETDEWEB)

    Fliller, R.P., III; /Brookhaven; Koeth, T.; /Rutgers U., Piscataway

    2009-09-01

    The promise of next-generation light sources depends on the availability of ultra-low emittance electron sources. One method of producing low transverse emittance beams is to generate a low longitudinal emittance beam and exchange it with a large transverse emittance. Experiments are underway at Fermilab's A0 Photoinjector and ANL's Argonne Wakefield Accelerator using the exchange scheme of Kim and Sessler. The experiment at the A0 Photoinjector exchanges a large longitudinal emittance with a small transverse emittance. AWA expects to exchange a large transverse emittance with a small longitudinal emittance. In this paper we discuss recent results at A0 and AWA and future plans for these experiments.

  9. Emittance Exchange Results

    Energy Technology Data Exchange (ETDEWEB)

    Fliller III,R.; Koeth, T.

    2009-05-04

    The promise of next-generation light sources depends on the availability of ultra-low emittance electron sources. One method of producing low transverse emittance beams is to generate a low longitudinal emittance beam and exchange it with a large transverse emittance. Experiments are underway at Fermilab's A0 Photoinjector and ANL's Argonne Wakefield Accelerator using the exchange scheme of Kim and Sessler. The experiment at the A0 Photoinjector exchanges a large longitudinal emittance with a small transverse emittance. AWA expects to exchange a large transverse emittance with a small longitudinal emittance. In this paper we discuss recent results at A0 and AWA and future plans for these experiments.

  10. Evaluation of Yields of γ-Rays Produced by Electrons from Gas Jets Irradiated by Low-Energy Laser Pulses: Towards “Virtual Radioisotopes”

    Science.gov (United States)

    Oishi, Yuji; Nayuki, Takuya; Zhidkov, Alexei; Fujii, Takashi; Nemoto, Koshichi

    2011-04-01

    Electron generation from a gas jet irradiated by low-energy femtosecond laser pulses is studied as a promising source of ˜1 MeV radiation for radioisotope-free γ-ray imaging systems: “virtual radioisotopes”. The yield of γ-rays in the 0.5-2 MeV range produced by low-average-power lasers and gas targets exceeds the yields from solid tape targets up to 2 orders of magnitude; it can be competitive with the yield from conventional radioisotopes used in industrial applications.

  11. Surface structure of Bi2Se3(111) determined by low-energy electron diffraction and surface x-ray diffraction

    DEFF Research Database (Denmark)

    dos Reis, Diogo Duarte; Barreto, Lucas; Bianchi, Marco

    2013-01-01

    The surface structure of the prototypical topological insulator Bi2Se3 is determined by low-energy electron diffraction and surface x-ray diffraction at room temperature. Both approaches show that the crystal is terminated by an intact quintuple layer. Specifically, an alternative termination by ...... by a bismuth bilayer is ruled out. Surface relaxations obtained by both techniques are in good agreement with each other and found to be small. This includes the relaxation of the van der Waals gap between the first two quintuple layers....

  12. Initial observations of high-charge, low-emittance electron beams at HIBAF (High Brightness Accelerator FEL)

    Energy Technology Data Exchange (ETDEWEB)

    Lumpkin, A.H.; Feldman, R.B.; Carsten, B.E.; Feldman, D.W.; Sheffield, R.L.; Stein, W.E.; Johnson, W.J.; Thode, L.E.; Bender, S.C.; Busch, G.E.

    1990-01-01

    We report our initial measurements of bright (high-charge, low-emittance) electron beams generated at the Los Alamos High Brightness Accelerator FEL (HIBAF) Facility. Normalized emittance values of less than 50 {pi} mm-mrad for charges ranging from 0.7 to 8.7 nC were obtained for single micropulses at a y-waist and at an energy of 14.7 MeV. These measurements were part of the commissioning campaign on the HIBAF photoelectric injector. Macropulse measurements have also been performed and are compared with PARMELA simulations. 5 refs., 8 figs., 3 tabs.

  13. Low-energy electron-induced dissociation in condensed-phase L-cysteine II: a comparative study on anion desorption from chemisorbed and physisorbed films

    Science.gov (United States)

    Alizadeh, Elahe; Massey, Sylvain; Sanche, Léon; Rowntree, Paul A.

    2016-04-01

    Due to its multifunctional structure, cysteine is becoming an ideal model molecule for investigating the complex interactions of proteins with metallic surfaces such as gold nanoparticles. We report herein the results of low-energy electron induced degradation of L-cysteine films, chemisorbed on a gold substrate via the thiol group or physisorbed into a clean gold surface. The data were recorded under ultra-high vacuum conditions at room temperature. Anion yields desorbed from these films by the impact of 0.5 to 19 eV electrons provide clear evidence of the efficient decomposition of this amino acid via dissociative electron attachment (i.e., from dissociation of intermediate transient anions located between 5 and 14 eV). The peaks in the desorbed-anion yield functions, associated with DEA, are superimposed on a continuously rising signal attributed to dipolar dissociation. Similar to the results previously observed from physisorbed films, light anionic species, with masses lower than 35 amu, have been detected. In addition, we measured for first time fragments at 14 amu (CH2-) and 15 amu (CH3-) desorbing from physisorbed films, as well as heavier fragments of mass 45 and 46 amu desorbing from chemisorbed films. Contribution to the Topical Issue "Low-Energy Interactions related to Atmospheric and Extreme Conditions", edited by S. Ptasinska, M. Smialek-Telega, A. Milosavljevic, B. Sivaraman.

  14. Emittance and Energy Diagnostics for Electron Beams with Large Momentum Spread

    CERN Document Server

    Olvegård, Maja; Thibaut, Lefevre; Enrico, Bravin

    Olvegård, M. 2013. Emittance and Energy Diagnostics for Electron Beams with Large Momentum Spread. Acta Universitatis Upsaliensis. Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 1036. 75 pp. Uppsala. ISBN 978-91-554-8646-4. Following the discovery of the Higgs-like boson at the Large Hadron Collider, there is demand for precision measurements on recent findings. The Compact Linear Collider, CLIC, is a candidate for a future linear electron-positron collider for such precision measurements. In CLIC, the beams will be brought to collisions in the multi-TeV regime through high gradient acceleration with high frequency RF power. A high intensity electron beam, the so-called drive beam, will serve as the power source for the main beam, as the drive beam is decelerated in special structures, from which power is extracted and transfered to the main beam. When the drive beam is decelerated the beam quality deteriorates and the momentum spread increases, which make...

  15. A novel setup for the determination of absolute cross sections for low-energy electron induced strand breaks in oligonucleotides - The effect of the radiosensitizer 5-fluorouracil*

    Science.gov (United States)

    Rackwitz, Jenny; Ranković, Miloš Lj.; Milosavljević, Aleksandar R.; Bald, Ilko

    2017-02-01

    Low-energy electrons (LEEs) play an important role in DNA radiation damage. Here we present a method to quantify LEE induced strand breakage in well-defined oligonucleotide single strands in terms of absolute cross sections. An LEE irradiation setup covering electron energies Measurements are presented for 10.0 and 5.5 eV for different oligonucleotide targets. The determination of absolute strand break cross sections is performed by atomic force microscopy analysis. An accurate fluence determination ensures small margins of error of the determined absolute single strand break cross sections σ SSB . In this way, the influence of sequence modification with the radiosensitive 5-Fluorouracil (5FU) is studied using an absolute and relative data analysis. We demonstrate an increase in the strand break yields of 5FU containing oligonucleotides by a factor of 1.5 to 1.6 compared with non-modified oligonucleotide sequences when irradiated with 10 eV electrons.

  16. Spin polarized low energy electron microscopy of quantum well resonances in Fe films on the Cu-covered W(110) surface.

    Science.gov (United States)

    Wu, Qiang; Altman, M S

    2013-07-01

    Spin polarized low energy electron microscopy has been used to investigate the quantum size effect (QSE) in electron reflectivity from Fe films grown on a pseudomorphic Cu layer on a W(110) surface. Intensity oscillations caused by the QSE as functions of Fe film thickness and incident electron energy identify quantum well resonance conditions in the film. Evaluation of these intensity oscillations using the phase accumulation model provides information on the unoccupied spin polarized band structure in the Fe film above the vacuum level. We also find evidence that the presence of the non-magnetic Cu layer shifts spin polarized quantum well resonances in the Fe layer uniformly downward in energy by 1.1eV compared to Fe/W(110) films without an interface Cu layer, suggesting that the Cu layer gives a small degree of control over the quantum well resonances.

  17. Electron Temperature Measurement Using PIN Diodes as Detectors to Record the X-ray Pulses from a Low-Energy Mather-Type Plasma Focus

    Institute of Scientific and Technical Information of China (English)

    M. Asif; Amna Ikram

    2004-01-01

    In the experiment to determine the plasma electron temperature, a modified multichannel PIN diodes assembly is used as detectors to record the X-ray pulses from a low-energy Mather-type plasma focus device energized by a 32μF, 15 kV (3.6 k J) single capacitor, with deuterium as a filling gas. The ratio of the integrated bremsstrahlung emission transmitting through foils to the total incident flux as a function of foil thickness at various temperatures is obtained for foil absorbers of material. Using 3μm, 6μm, 9μm,12μm,15μm and 18μm thick aluminium absorbers, the transmitted X-ray flux is detected. By comparing the experimental and theoretical curves through a computer program, the plasma electron temperature is determined. Results show that the deuterium focus plasma electron temperature is about 800 eV.

  18. L-Shell Ionization Cross Section Measurements of Dysprosium and Samarium by Low-Energy Electron Impact

    Institute of Scientific and Technical Information of China (English)

    GOU Cheng-Jun; WU Zhang-Wen; YANG Dai-Lun; HE Fu-Qing; PENG Xiu-Feng; AN Zhu; LUO Zheng-Ming

    2005-01-01

    @@ The Lα, Lβ and Lγ x-ray production cross sections of Dy and Sm by electron impact are measured at energies from near threshold to tens of keV. In the experiments, thin targets with thick substrates are used. Meanwhile,the electron transport bipartition model is used to eliminate the influence of electrons reflected from the thick substrates on measurements. The measured x-ray production cross sections are also compared with the theoretical predictions by Gryzinski and McGuire.

  19. Capture, Electron-Cooling and Compression of Antiprotons in a Large Penning-Trap for Physics Experiments with an Ultra-Low Energy Extracted Antiproton Beam

    CERN Multimedia

    2002-01-01

    % PS200 \\\\ \\\\The availability of ultra-low energy antiprotons is a crucial ingredient for the execution of the gravity measurements PS200. We have developed a method to provide such low energy antiprotons based on a large Penning trap (the PS200 catching trap). This system can accept a fast-extracted pulse from LEAR, reduce the energy of the antiprotons in the pulse from 5.9~MeV to several tens of kilovolts using a degrading foil, and then capture the antiprotons in a large Penning trap. These antiprotons are cooled by electrons previously admitted to the trap and are collected in a small region at the center of the trap. We have demonstrated our capability to capture up to 1~million antiprotons from LEAR in a single shot, electron cool these antiprotons, and transfer up to 95\\% of them into the inner, harmonic region. A storage time in excess of 1 hour was observed. These results have been obtained with the cryogenic trap vacuum coupled to a room temperature vacuum at about l0$ ^- ^{1} ^0 $ Torr, which is an...

  20. Quantum-kinetic modeling of electron release in low-energy surface collisions of atoms and molecules

    Energy Technology Data Exchange (ETDEWEB)

    Marbach, Johannes

    2012-09-20

    In this work we present a theoretical description of electron release in the collision of atomic and molecular projectiles with metallic and especially dielectric surfaces. The associated electron yield, the secondary electron emission coefficient, is an important input parameter for numerical simulations of dielectric barrier discharges and other bounded low-temperature gas discharges. The available reference data for emission coefficients is, however, very sparse and often uncertain, especially for molecular projectiles. With the present work we aim to contribute to the filling of these gaps by providing a flexible and easy-to-use model that allows for a convenient calculation of the emission coefficient and related quantities for a wide range of projectile-surface systems and the most dominant reaction channels.

  1. Planar ultrananocrystalline diamond field emitter in accelerator radio frequency electron injector: Performance metrics

    Energy Technology Data Exchange (ETDEWEB)

    Baryshev, Sergey V., E-mail: sergey.v.baryshev@gmail.com; Antipov, Sergey; Jing, Chunguang; Qiu, Jiaqi [Euclid TechLabs, 365 Remington Blvd., Bolingbrook, Illinois 60440 (United States); High Energy Physics Division, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, Illinois 60439 (United States); Shao, Jiahang; Liu, Wanming; Gai, Wei [High Energy Physics Division, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, Illinois 60439 (United States); Pérez Quintero, Kenneth J.; Sumant, Anirudha V., E-mail: sumant@anl.gov [Center for Nanoscale Materials, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, Illinois 60439 (United States); Kanareykin, Alexei D. [Euclid TechLabs, 365 Remington Blvd., Bolingbrook, Illinois 60440 (United States)

    2014-11-17

    A case performance study of a planar field emission cathode (FEC) based on nitrogen-incorporated ultrananocrystalline diamond, (N)UNCD, was carried out in an RF 1.3 GHz electron gun. The FEC was a 100 nm (N)UNCD film grown on a 20 mm diameter stainless steel disk with a Mo buffer layer. At surface gradients 45–65 MV/m, peak currents of 1–80 mA (equivalent to 0.3–25 mA/cm{sup 2}) were achieved. Imaging with two YAG screens confirmed emission from the (N)UNCD surface with (1) the beam emittance of 1.5 mm × mrad/mm-rms and (2) longitudinal FWHM and rms widths of non-Gaussian energy spread of 0.7% and 11% at an electron energy of 2 MeV. Current stability was tested over the course of 36 × 10{sup 3} RF pulses (equivalent to 288 × 10{sup 6 }GHz oscillations)

  2. Self-modulated field electron emitter: Gated device of integrated Si tip-on-nano-channel

    Science.gov (United States)

    Huang, Zhijun; Huang, Yifeng; Pan, Zhangxu; She, Juncong; Deng, Shaozhi; Chen, Jun; Xu, Ningsheng

    2016-12-01

    We report the featured gated field electron emission devices of Si nano-tips with individually integrated Si nano-channels and the interpretation of the related physics. A rational procedure was developed to fabricate the uniform integrated devices. The electrical and thermal conduction tests demonstrated that the Si nano-channel can limit both the current and heat flows. The integrated devices showed the specialties of self-enhancement and self-regulation. The heat resistance results in the heat accumulation at the tip-apex, inducing the thermally enhanced field electron emission. The self-regulated effect of the electrical resistance is benefit for impeding the current overloading and prevents the emitters from a catastrophic breakdown. The nano-channel-integrated Si nano-tip array exhibited emission current density up to 24.9 mA/cm2 at a gate voltage of 94 V, much higher than that of the Si nano-tip array without an integrated nano-channel.

  3. A new calculation on the stopping power and mean free path for low energy electrons in toluene over energy range of 20-10000 eV.

    Science.gov (United States)

    Tan, Zhenyu; Xia, Yueyuan; Liu, Xiangdong; Zhao, Mingwen; Zhang, Liming

    2009-04-01

    A new calculation of the stopping powers (SP) and inelastic mean free paths (IMFP) for electrons in toluene at energies below 10 keV has been presented. The calculation is based on the dielectric model and on an empirical evaluation approach of optical energy loss function (OELF). The reliability for the evaluated OELFs of several hydrocarbons with available experimental optical data has been systematically checked. For toluene, using the empirical OELF, the evaluated mean ionization potential, is compared with that given by Bragg's rule, and the calculated SP at 10 keV is also compared with the Bethe-Bloch prediction. The present results for SP and IMFP provide an alternative basic data for the study on the energy deposition of low-energy electrons transport through toluene, and also show that the method used in this work may be a good one for evaluating the SP and IMFP for hydrocarbons.

  4. Technical Note: Improvements in GEANT4 energy-loss model and the effect on low-energy electron transport in liquid water

    Energy Technology Data Exchange (ETDEWEB)

    Kyriakou, I., E-mail: ikyriak@cc.uoi.gr [Medical Physics Laboratory, University of Ioannina Medical School, Ioannina 45110 (Greece); Incerti, S. [Centre d’Etudes Nucléaires de Bordeaux-Gradignan, CENBG, Chemin du Solarium, Université de Bordeaux, Gradignan 33175, France and Centre d’Etudes Nucléaires de Bordeaux-Gradignan, CENBG, Chemin du Solarium, CNRS/IN2P3, Gradignan 33175 (France); Francis, Z. [Department of Physics, Faculty of Sciences, Saint Joseph University, Mkalles, Beirut (Lebanon)

    2015-07-15

    Purpose: The GEANT4-DNA physics models are upgraded by a more accurate set of electron cross sections for ionization and excitation in liquid water. The impact of the new developments on low-energy electron transport simulations by the GEANT4 Monte Carlo toolkit is examined for improving its performance in dosimetry applications at the subcellular and nanometer level. Methods: The authors provide an algorithm for an improved implementation of the Emfietzoglou model dielectric response function of liquid water used in the GEANT4-DNA existing model. The algorithm redistributes the imaginary part of the dielectric function to ensure a physically motivated behavior at the binding energies, while retaining all the advantages of the original formulation, e.g., the analytic properties and the fulfillment of the f-sum-rule. In addition, refinements in the exchange and perturbation corrections to the Born approximation used in the GEANT4-DNA existing model are also made. Results: The new ionization and excitation cross sections are significantly different from those of the GEANT4-DNA existing model. In particular, excitations are strongly enhanced relative to ionizations, resulting in higher W-values and less diffusive dose-point-kernels at sub-keV electron energies. Conclusions: An improved energy-loss model for the excitation and ionization of liquid water by low-energy electrons has been implemented in GEANT4-DNA. The suspiciously low W-values and the unphysical long tail in the dose-point-kernel have been corrected owing to a different partitioning of the dielectric function.

  5. Gridless, very low energy, high-current, gaseous ion source

    Energy Technology Data Exchange (ETDEWEB)

    Vizir, A. V.; Oks, E. M. [High Current Electronics Institute, Russian Academy of Sciences, Tomsk 634055 (Russian Federation); State University of Control Systems and Radioelectronics, Tomsk 634050 (Russian Federation); Shandrikov, M. V.; Yushkov, G. Yu. [High Current Electronics Institute, Russian Academy of Sciences, Tomsk 634055 (Russian Federation)

    2010-02-15

    We have made and tested a very low energy gaseous ion source in which the plasma is established by a gaseous discharge with electron injection in an axially diverging magnetic field. A constricted arc with hidden cathode spot is used as the electron emitter (first stage of the discharge). The electron flux so formed is filtered by a judiciously shaped electrode to remove macroparticles (cathode debris from the cathode spot) from the cathode material as well as atoms and ions. The anode of the emitter discharge is a mesh, which also serves as cathode of the second stage of the discharge, providing a high electron current that is injected into the magnetic field region where the operating gas is efficiently ionized. In this discharge configuration, an electric field is formed in the ion generation region, accelerating gas ions to energy of several eV in a direction away from the source, without the use of a gridded acceleration system. Our measurements indicate that an argon ion beam is formed with an energy of several eV and current up to 2.5 A. The discharge voltage is kept at less than 20 V, to keep below ion sputtering threshold for cathode material, a feature which along with filtering of the injected electron flow, results in extremely low contamination of the generated ion flow.

  6. Analytic Elastic Cross Sections for Electron-Atom Scattering from Generalized Fano Profiles of Overlapping Low-Energy Shape Resonances

    CERN Document Server

    Nicoletopoulos, P

    2003-01-01

    The variation with energy of the total cross section for elastic electron scattering from atoms of several elements is caused primarily by shape resonances corresponding to the formation of temporary negative ions. It is shown that such cross sections are expressible analytically in terms of a constant background added to a "generalized Fano profile" [Durand Ph, et al (2001) J. Phys. B: At. Mol. Opt. Phys. 34, 1953, ibid (2002) 35, 469]. In three cases (sodium, magnesium and mercury), a detailed consideration proves that this representation is accurate in a fairly wide energy range. Moreover, the related momentum transfer cross sections are tailor-made for studying "elastic" electron transport in terms of the two-term solution of the Boltzmann equation: Not only are the resulting swarm transport coefficients adjustable to the experimental values, but above all they are calculable very easily because the unnormalized energy distribution is obtainable analytically. The ample saving in computational effort is ex...

  7. Individualized eye shields for use in electron beam therapy as well as low-energy photon irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Asbell, S.O.; Siu, J.; Lightfoot, D.A.; Brady, L.W.

    1980-04-01

    Thin lead eye shields formed with a rubber hammer over smooth wooden mandril and coated with dental acrylic have been used on 25 patients undergoing electron beam treatment for mycosis fungoides or superficial x-ray irradiation with no significant difficulties. The shields may be fabricated in less than two hours and exactly fit the contour and size of the eye. Details of the fabrication process and evaluation of the shielding effectiveness are presented.

  8. Origin of surface electron accumulation and fermi level pinning in low energy ion induced InN/GaN heterostructure

    Energy Technology Data Exchange (ETDEWEB)

    Mishra, Monu; Shibin Krishna, T.C. [Surface Physics and Nanostructure Heteroepitaxy Laboratory, Physics of Energy Harvesting Division, CSIR-National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi 110012 (India); Academy of Scientific and Innovative Research (AcSIR), CSIR-NPL Campus, Dr. K.S. Krishnan Marg, New Delhi 110012 (India); Kumar, Mukesh [Surface Physics and Nanostructure Heteroepitaxy Laboratory, Physics of Energy Harvesting Division, CSIR-National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi 110012 (India); Gupta, Govind, E-mail: govind@nplindia.org [Surface Physics and Nanostructure Heteroepitaxy Laboratory, Physics of Energy Harvesting Division, CSIR-National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi 110012 (India); Academy of Scientific and Innovative Research (AcSIR), CSIR-NPL Campus, Dr. K.S. Krishnan Marg, New Delhi 110012 (India)

    2015-07-15

    InN/GaN heterostructure was fabricated via reactive low energetic Nitrogen ion (LENI at 300 eV) bombardment at lower substrate temperature (350 °C). X-Ray Photoemission spectroscopic (XPS) and Atomic Force Microscopic (AFM) measurements were performed to analyse the electronic structure, surface chemistry, band alignment, and the morphology of the grown heterostructure. XPS analysis revealed the evolution of InN structure with nitridation time, surface electron accumulation, fermi level pinning and the band offset of the grown InN/GaN hetero structure. The valence band and conduction band offsets (VBO & CBO) were calculated to be 0.49 ± 0.19 eV and 2.21 ± 0.1 eV and divulged the formation of a type-I heterojunction. A Fermi Level (FL) pinning of 1.5 ± 0.1 eV above the conduction band minima was perceived and indicated towards strong downward band bending. The analysis of the VB spectra suggested that surface electron accumulation occurred due to the presence of metallic In-adlayer on the surface which resulted in FL pinning and the corresponding downward band bending. Atomic Force Microscopy analysis divulged the formation of smooth surface with granular structure. It was also observed that the growth parameters (e.g. substrate temperature) strongly influence the aforementioned surface and interfacial properties. - Highlights: • A novel technique for the growth of ultrathin InN/GaN heterostructure is reported. • Surface Electron Accumulation and FL Pinning were observed. • A strong downward band bending was also observed in the InN/GaN heterostructure.

  9. A supercell, Bloch wave method for calculating low-energy electron reflectivity with applications to free-standing graphene and molybdenum disulfide

    Science.gov (United States)

    McClain, John

    This dissertation reports on a novel theoretical and computational framework for calculating low-energy electron reflectivities from crystalline surfaces and its application to two layered systems of two-dimensional materials, graphene and molybdenum disulfide. The framework provides a simple and efficient approach through the matching of a small set of Fourier components of Bloch wave solutions to the Schrodinger Equation in a slab-in-supercell geometry to incoming and outgoing plane waves on both sides of the supercell. The implementation of this method is described in detail for the calculation of reflectivities in the lowest energy range, for which only specular reflection is allowed. This implementation includes the calculation of reflectivities from beams with normal or off-normal incidence. Two different algorithms are described in the case of off-normal incidence which differ in their dependence on the existence of a symmetry with a mirror plane parallel to the crystal surface. Applications to model potentials in one, two, and three dimensions display consistent results when using different supercell sizes and convergent results with the density of Fourier grids. The design of the Bloch wave matching also allows for the accurate modeling of crystalline slabs through the use of realistic potentials determined via density functional theory. The application of the method to low-energy electron scattering from free-standing systems of a few layers of graphene, including the use of these realistic potentials, demonstrates this ability of the method to accurately model real systems. It reproduces the layer-dependent oscillations found in experimental, normal incidence reflectivity curves for a few layers of graphene grown on silicon carbide. The normal incidence reflectivity curves calculated for slabs consisting of few-layer graphene on 10 layers of nickel show some qualitative agreement with experiment. General incidence reflectivity spectra for free

  10. Enhanced field emission from compound emitters of carbon nanotubes and ZnO tetrapods by electron beam bombardment.

    Science.gov (United States)

    Wei, Lei; Zhang, Xiaobing; Lou, Chaogang; Zhao, Zhiwei; Jing, Chen; Wang, Baoping

    2011-06-01

    The enhancement of field emission from compound emitters of carbon nanotubes and ZnO tetrapods by the electron beam bombardment is reported. After 20 minutes electron bombardment with 6 keV energy, a few bird-nest micro structures are formed in the compound emitters array. As the simulation results shown, the electric field and field emission current density at the tip of ZnO tetrapod are increased due to the influences of these bird-nest micro structures. From the measurement of the field emission performance, it can be seen that the turn-on electric field and threshold electric field of the field emitter array decrease to 0.4 V/microm and 2.4 V/microm respectively. They have decreased 62% and 15% after the electron bombardment. After the electron bombardment, the emission sites density is increased. The field emission images show that the uniformity of field emission has been improved obviously after the proper electron bombardment. The methodology proposed in this paper has a promising application in the field emission devices.

  11. Results from a 64-pixel PIN-diode detector system for low-energy beta-electrons

    Energy Technology Data Exchange (ETDEWEB)

    Wuestling, Sascha, E-mail: sascha.wuestling@kit.ed [Forschungszentrum Karlsruhe, Institut fuer Prozessdatenverarbeitung und Elektronik, Postfach 3640, 76021 Karlsruhe (Germany); Fraenkle, F.; Habermehl, F.; Renschler, P. [Universitaet Karlsruhe - TH, Institut fuer Experimentelle Kernphysik, Postfach 6980, 76128 Karlsruhe (Germany); Steidl, M [Forschungszentrum Karlsruhe, Institut fuer Kernphysik, Postfach 3640, 76021 Karlsruhe (Germany)

    2010-12-11

    The KATRIN neutrino mass experiment is based on a precise energy measurement ({Delta}E/E=5x10{sup -5}) of electrons emerging from tritium beta decay (E{sub max}=18.6 keV). This is done by a large electrostatic retarding spectrometer (MAC-E Filter), which is followed by an electron detector. Key requirements for this detector are a large sensitive area ({approx}80 cm{sup 2}), a certain energy resolution ({Delta}E=600 eV - 18.6 keV) but also a certain spatial resolution ({approx}3 mm), which leads to a multi-pixel design. As a tentative design on the way to the final detector, but also for operational service on the so-called pre-spectrometer experiment, a detector system with a reduced size (16 cm{sup 2}) and a reduced pixel number (64), making use of a monolithic segmented silicon PIN diode, was designed and built. While the design and very first measurements have been presented in Wuestling et al. , this publication shows the operational performance of the detector system. The robust concept of the electronics allowed adaptation to mechanically different experimental setups. The spacial resolution of the detector system proved to be essential in examining Penning trap induced background and other effects in the pre-spectrometer experiment. The detector performance test runs include energy resolution and calibration, background rates, correlation between pixels (crosstalk), spatially resolved rate analysis, and a dead-layer measurement . The detector allows for background searches with a sensitivity as low as 1.3x10{sup -3} cps/cm{sup 2} in the energy range of 20 keV. This allows the pre-spectrometer to be characterized with e-gun illumination with a signal to background ratio of better than 10{sup 5} and the search for ultra low Penning discharge emissions.

  12. Results from a 64-pixel PIN-diode detector system for low-energy beta-electrons

    Science.gov (United States)

    Wuestling, Sascha; Fraenkle, F.; Habermehl, F.; Renschler, P.; Steidl, M.

    2010-12-01

    The KATRIN neutrino mass experiment is based on a precise energy measurement (Δ E/ E=5×10 -5) of electrons emerging from tritium beta decay ( Emax=18.6 keV). This is done by a large electrostatic retarding spectrometer (MAC-E Filter), which is followed by an electron detector. Key requirements for this detector are a large sensitive area (˜80 cm 2), a certain energy resolution (Δ E=600 eV @ 18.6 keV) but also a certain spatial resolution (˜3 mm), which leads to a multi-pixel design. As a tentative design on the way to the final detector, but also for operational service on the so-called pre-spectrometer experiment, a detector system with a reduced size (16 cm 2) and a reduced pixel number (64), making use of a monolithic segmented silicon PIN diode, was designed and built. While the design and very first measurements have been presented in Wuestling et al. [6], this publication shows the operational performance of the detector system. The robust concept of the electronics allowed adaptation to mechanically different experimental setups. The spacial resolution of the detector system proved to be essential in examining Penning trap induced background and other effects in the pre-spectrometer experiment. The detector performance test runs include energy resolution and calibration, background rates, correlation between pixels (crosstalk), spatially resolved rate analysis, and a dead-layer measurement [7]. The detector allows for background searches with a sensitivity as low as 1.3×10 -3 cps/cm 2 in the energy range of 20 keV. This allows the pre-spectrometer to be characterized with e-gun illumination with a signal to background ratio of better than 10 5 and the search for ultra low Penning discharge emissions.

  13. Free Electron Laser for Gamma-Gamma Collider at a Low-Energy Option of International Linear Collider

    Energy Technology Data Exchange (ETDEWEB)

    Saldin, Evgeny; Schneidmiller, Evgeny; Yurkov, Mikhail; /DESY; Seryi, Andrei; /SLAC

    2009-10-30

    Different scenarios of a start-up with International Linear Collider (ILC) are under discussion at the moment in the framework of the Global Design Effort (GDE). One of them assumes construction of the ILC in stages from some minimum CM energy up to final target of 500 GeV CM energy. Gamma-gamma collider with CM energy of 180GeV is considered as a candidate for the first stage of the facility. In this report we present conceptual design of a free electron laser as a source of primary photons for the first stage of ILC.

  14. Low-energy electron reflection from Au-passivated Ir(0 0 1) for application in imaging spin-filters

    Energy Technology Data Exchange (ETDEWEB)

    Vasilyev, D.; Tusche, C. [Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle (Germany); Giebels, F.; Gollisch, H. [Universität Duisburg-Essen, Fakultät für Physik, Campus Duisburg, Lotharstr. 1, 47048 Duisburg (Germany); Feder, R. [Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle (Germany); Universität Duisburg-Essen, Fakultät für Physik, Campus Duisburg, Lotharstr. 1, 47048 Duisburg (Germany); Kirschner, J., E-mail: sekrki@mpi-halle.mpg.de [Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, 06120 Halle (Germany); Martin-Luther-Universität Halle-Wittenberg, Institut für Physik, 06099 Halle (Germany)

    2015-02-15

    We describe the principle, the preparation, and the calibration of a spin-polarizing electron mirror in multichannel spin polarimetry. We show data obtained by two independent devices (a goniometer-type LEED set-up and a momentum-microscope set-up) and compare them to the results of a relativistic multiple scattering theory. We also discuss the effects of misalignment and mosaic structure of the crystal. For multi-channel detection we find a 5000-fold increase of efficiency over a single-channel spin-detector. The lifetime of the detector is more than 6 months in ultra-high vacuum.

  15. Radiation damage of multipixel Geiger-mode avalanche photodiodes irradiated with low-energy γ's and electrons

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Y.; Yun, Y. B. [Yonsei University, Seoul (Korea, Republic of); Ha, J. M. [Yonsei University, Seoul (Korea, Republic of); Electronics and Telecommunications Research Institute, Daejeon (Korea, Republic of); Lee, J. S.; Yoon, Y. S. [Electronics and Telecommunications Research Institute, Daejeon (Korea, Republic of); Eun, J. W. [Namseoul University, Cheonan (Korea, Republic of)

    2012-05-15

    A few types of multipipixel Geiger-mode avalanche photodiodes (also referred to as silicon photomultipliers SiPMs) are irradiated with 1 to 2.5 MeV γ's and electrons. We characterize radiation damage effects appearing in the reverse bias current, the dark current and count rate, the pixel gain, and the photon detection efficiency of the devices. An interesting observation on the dark current and count rate is made and linked to the specific damage caused by the irradiation.

  16. Charge Exchange in Low-Energy H, D + C4+ Collisions with Full Account of Electron Translation

    Directory of Open Access Journals (Sweden)

    A. Riera

    2002-03-01

    Full Text Available The effect of the anisotropy of the interaction potential on ion-diatom non-adiabatic collisions is analized by considering the influence of the anisotropy on orientation averaged total cross sections for charge transfer in H++H2(X1Σ+g collisions. We discuss the possibility of employing simpli ed methods such as an isotropic approximation, where only the electronic energies and interactions of a single orientation are necessary. The use of several isotropic calculations to evaluate the orientation averaged cross section is analized.

  17. Communication: Low-energy free-electron driven molecular engineering: In situ preparation of intrinsically short-lived carbon-carbon covalent dimer of CO

    Science.gov (United States)

    Davis, Daly; Sajeev, Y.

    2017-02-01

    Molecular modification induced through the resonant attachment of a low energy electron (LEE) is a novel approach for molecular engineering. In this communication, we explore the possibility to use the LEE as a quantum tool for the in situ preparation of short lived molecules. Using ab initio quantum chemical methods, this possibility is best illustrated for the in situ preparation of the intrinsically short-lived carbon-carbon covalent dimer of CO from a glyoxal molecule. The chemical conversion of glyoxal to the covalent dimer of CO is initiated and driven by the resonant capture of a near 11 eV electron by the glyoxal molecule. The resulting two-particle one-hole (2p-1h) negative ion resonant state (NIRS) of the glyoxal molecule undergoes a barrierless radical dehydrogenation reaction and produces the covalent dimer of CO. The autoionization electron spectra from the 2p-1h NIRS at the dissociation limit of the dehydrogenation reaction provides access to the electronic states of the CO dimer. The overall process is an example of a catalytic electron reaction channel.

  18. Simulation study of electron cloud induced instabilities and emittance growth for the CERN Large Hadron Collider proton beam

    Directory of Open Access Journals (Sweden)

    E. Benedetto

    2005-12-01

    Full Text Available The electron cloud may cause transverse single-bunch instabilities of proton beams such as those in the Large Hadron Collider (LHC and the CERN Super Proton Synchrotron (SPS. We simulate these instabilities and the consequent emittance growth with the code HEADTAIL, which models the turn-by-turn interaction between the cloud and the beam. Recently some new features were added to the code, in particular, electric conducting boundary conditions at the chamber wall, transverse feedback, and variable beta functions. The sensitivity to several numerical parameters has been studied by varying the number of interaction points between the bunch and the cloud, the phase advance between them, and the number of macroparticles used to represent the protons and the electrons. We present simulation results for both LHC at injection and SPS with LHC-type beam, for different electron-cloud density levels, chromaticities, and bunch intensities. Two regimes with qualitatively different emittance growth are observed: above the threshold of the transverse mode-coupling (TMC type of instability there is a rapid blowup of the beam, while below this threshold a slow, long-term, emittance growth remains. The rise time of the TMC instability caused by the electron cloud is compared with results obtained using an equivalent broadband resonator impedance model, demonstrating reasonable agreement.

  19. Low Energy Electron and Nuclear Recoil Thresholds in the DRIFT-II Negative Ion TPC for Dark Matter Searches

    CERN Document Server

    Burgos, S; Forbes, J; Ghag, C; Gold, M; Hagemann, C; Kudryavtsev, V A; Lawson, T B; Loomba, D; Majewski, P; Muna, D; Murphy, A St J; Paling, S M; Petkov, A; Plank, S J S; Robinson, M; Sanghi, N; Snowden-Ifft, D P; Spooner, N J C; Turk, J; Tziaferi, E

    2009-01-01

    Understanding the ability to measure and discriminate particle events at the lowest possible energy is an essential requirement in developing new experiments to search for weakly interacting massive particle (WIMP) dark matter. In this paper we detail an assessment of the potential sensitivity below 10 keV in the 1 m^3 DRIFT-II directionally sensitive, low pressure, negative ion time projection chamber (NITPC), based on event-by-event track reconstruction and calorimetry in the multiwire proportional chamber (MWPC) readout. By application of a digital smoothing polynomial it is shown that the detector is sensitive to sulfur and carbon recoils down to 3.5 and 2.2 keV respectively, and 1.2 keV for electron induced tracks. The energy sensitivity is demonstrated through the 5.9 keV gamma spectrum of 55Fe, where the energy resolution is sufficient to identify the escape peak. In addition to recoil direction reconstruction for WIMP searches this sensitivity suggests new prospects for applications also in KK axion s...

  20. Resonant vibrational-excitation cross sections and rate constants for low-energy electron scattering by molecular oxygen

    CERN Document Server

    Laporta, V; Tennyson, J

    2016-01-01

    Resonant vibrational-excitation cross sections and rate constants for electron scattering by molecular oxygen are presented. Transitions between all 42 vibrational levels of O$_2(\\textrm{X}\\ ^3\\Sigma_g^- $) are considered. Molecular rotations are parameterized by the rotational quantum number $J$ which is considered in the range 1 to 151. The lowest four resonant states of O$_2^-$, $^2\\Pi_g$, $^2\\Pi_u$, $^4\\Sigma_u^-$ and $^2\\Sigma_u^-$, are taken into account. The calculations are performed using the fixed-nuclei R-matrix approach to determine the resonance positions and widths, and the boomerang model to characterize the nuclei motion. Two energy regions below and above 4~eV are investigated: the first one is characterized by sharp structures in the cross section, and the second by a broad resonance peaked at 10~eV. The computed cross sections are compared with theoretical and experimental results available in literature for both the energy regions, and are made available for use by modelers. The effect of ...

  1. INVESTIGATION OF THE MONOCAPILLARY THERMIONIC EMITTER AS A DUAL SOURCE OF IONS AND ELECTRONS

    Science.gov (United States)

    potential concept. Several processes for fabricating multicapillary emitters are described, including stacking fine wires, spark machining...of an electromagnetic pump. Finally, the design and fabrication of a closed cycle (gravity feed) multicapillary thermionic converter are discussed. (Author)

  2. Electron field emission characteristics of graphene/carbon nanotubes hybrid field emitter

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Leifeng, E-mail: chlf@hdu.edu.cn [College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); He, Hong; Yu, Hua; Cao, Yiqi [College of Materials and Environmental Engineering, Hangzhou Dianzi University, Hangzhou 310018 (China); Lei, Da, E-mail: leida126@126.com [Ordos College of Inner Mongolia University, Inner Mongolia University, Ordos 017000 (China); Menggen, QiQiGe [Ordos College of Inner Mongolia University, Inner Mongolia University, Ordos 017000 (China); Wu, Chaoxing; Hu, Liqin [College of Physics and Information Engineering, Fuzhou University, Fuzhou 350002 (China)

    2014-10-15

    The graphene (GP) and multi-walled carbon nanotubes (MCNTs) hybrid nanostructure emitter was constructed by a larger scale electrophoretic deposition (EPD) method. The field emission (FE) performance of the hybrid emitter is greatly improved compared with that of only GP or MCNTs emitter. The low turn-on electric field (EF), the low threshold EF and the reliability FE properties are obtained from the hybrid emitter. The better FE properties result from the improved electrical properties. For further enhancement FE of hybrids, Ag Nanoparticles (NPs) were decorated on the hybrids and FE characteristics were also studied. These studies indicate that we can use the hybrid nanostructure to improve conductivity and contact resistance, which results in enhancement of the FE properties.

  3. Current gain above 10 in sub-10 nm base III-Nitride tunneling hot electron transistors with GaN/AlN emitter

    Science.gov (United States)

    Yang, Zhichao; Zhang, Yuewei; Krishnamoorthy, Sriram; Nath, Digbijoy N.; Khurgin, Jacob B.; Rajan, Siddharth

    2016-05-01

    We report on a tunneling hot electron transistor amplifier with common-emitter current gain greater than 10 at a collector current density in excess of 40 kA/cm2. The use of a wide-bandgap GaN/AlN (111 nm/2.5 nm) emitter was found to greatly improve injection efficiency of the emitter and reduce cold electron leakage. With an ultra-thin (8 nm) base, 93% of the injected hot electrons were collected, enabling a common-emitter current gain up to 14.5. This work improves understanding of the quasi-ballistic hot electron transport and may impact the development of high speed devices based on unipolar hot electron transport.

  4. Collisions of electrons with hydrogen atoms II. Low-energy program using the method of the exterior complex scaling

    Science.gov (United States)

    Benda, Jakub; Houfek, Karel

    2014-11-01

    While collisions of electrons with hydrogen atoms pose a well studied and in some sense closed problem, there is still no free computer code ready for “production use”, that would enable applied researchers to generate necessary data for arbitrary impact energies and scattering transitions directly if absent in on-line scattering databases. This is the second article on the Hex program package, which describes a new computer code that is, with a little setup, capable of solving the scattering equations for energies ranging from a fraction of the ionization threshold to approximately 100 eV or more, depending on the available computational resources. The program implements the exterior complex scaling method in the B-spline basis. Catalogue identifier: AETI_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AETI_v1_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 44 440 No. of bytes in distributed program, including test data, etc.: 322 643 Distribution format: tar.gz Programming language: C++11. Computer: Any. Operating system: Any system with a C++11 compiler (e.g. GCC 4.8.1; tested on OpenSUSE 13.1 and Windows 8). Has the code been vectorized or parallelized?: Parallelized by OpenMP and MPI. RAM: Depending on input; 4.9 GiB for the test run. Classification: 2.4. External routines: GSL [1], HDF5 [2], UMFPACK [3], FFTW3 [4], optionally with OpenBLAS [5]. Nature of problem: Solution of the two-particle Schrödinger equation in central field. Solution method: The two-electron states are expanded into angular momentum eigenstates, which gives rise to the coupled bi-radial equations. The bi-radially dependent solution is then represented in a B-spline basis, which transforms the set of equations into a large matrix equation in this basis. The boundary condition

  5. Synthesis of polymer materials by low energy electron beam. IV. EB-polymerized urethane-acrylate, -methacrylate and -acrylamide

    Science.gov (United States)

    Ando, Masayuki; Uryu, Toshiyuki

    The structure and properties before and after electron beam (EB) irradiation were investigated using urethane prepolymers with different terminal groups of 2-hydroxyethyl acrylate (HEA), 2-hydroxyethyl methacrylate (HEMA) and N-hydroxymethyl acrylamide (HMAAm). The prepolymers were synthesized by reaction of HEA, HEMA and HMAAm with the isocyanate-capped intermediate, which was obtained by reaction of poly(butylene adipate)diol (PBAD) with 4,4'-diphenylmethane diisocyanate. The resulting urethane-acrylate (UA-251M), -methacrylate (UMA-251M) and -acrylamide (UNAA-251M) had the crystallinity arising from PBAD moieties, and UA-251M and UMA-251M had higher crystallinity than UNAA-251M. IR results indicated that UNAA-251M was larger in the fraction of free NH stretching absorption than UA-251M and UMA-251M regardless of the number of NH group per a molecule. Accordingly, it was assumed that the difference in crystallinity was attributed to the polarity of terminal group. Hence, the rate of gel formation for UA-251M and UMA-251M was higher than that of UNAA-251M. The crystallinity based on PBAD of the prepolymers was remained also after EB irradiation. Spherulitic texture was observed on the EB-polymerized gel film surfaces for UA-251M and UMA-251M, while it was almost destroyed for UNAA-251M. Mechanical properties of UA-251M and UMA-251M gel films were much superior to those of UNAA-251M gel film according to the phase structure. Especially, UMA-251M gel film represented most excellent mechanical properties. Schematic models of the phase structure for UA-251M, UMA-251M and UNAA-251M were suggested from all experimental results.

  6. He2 (60-100nm) and Ne_2^* (80-90nm) excimer lamps pumped by low energy electron beams

    Science.gov (United States)

    Ulrich, Andreas; Wieser, Jochen; Salvermoser, Manfred; Murnick, Daniel E.

    2001-10-01

    Low energy (10 to 20keV) electron beams transmitted through extremely thin ceramic foils into high pressure rare gases and rare gas mixtures have been demonstrated to produce efficiently excimer radiation [1,2]. In this report, previous work has been extended to the deep UV emission from helium and neon excimers. The localized nature of the excitation allows windowless systems to be used in a rare gas atmosphere transparent to the 60 to 100nm radiation produced. Both pulsed and cw sources can be realized with extremely high brightness possible. Because of the high energy per photon, such systems may be useful for a variety of materials modification applications. [1] J. Wieser et al. Rev. Sci. Instrum 68, 1360 (1997) [2] M. Salvermoser et al., J. Appl. Phys. 88, 453 (2000) [3] A. Ulrich et al. Physikalische Blätter 56, 49 (2000)

  7. Role of competing orders (COs) in the low-energy pseudogap (PG) phenomena and quasiparticle (QP) excitations of hole- and electron-type cuprate superconductors

    Science.gov (United States)

    Beyer, A. D.; Grinolds, M. S.; Teague, M. L.; Yeh, N.-C.; Lee, S.-I.

    2008-03-01

    Our cryogenic scanning tunneling spectroscopic studies of spatially resolved QP density of states (DOS) in hole-type YBa2Cu3Ox and electron-type La0.1Sr0.9CuO2 cuprate superconductors (SC) reveal that the existence of COs in the cuprates can account for many seeming non-universal phenomena. Namely, we analyze the low-energy QP excitation spectra by using a microscopic model of coexisting SC/CO, with density-wave type COs, and find that various spectral characteristics are uniquely determined by the parameters δSC, VCO, Q, η, and γ (δSC: SC gap, VCO: CO gap, Q: CO wave-vector, η: strength of quantum fluctuations, γ: line-width of QP spectral peak). For instance, VCO>δSC (VCOVCO values derived by our analysis.

  8. Low-energy x-ray and electron physics and applications to diagnostics development for laser-produced plasma research. Final report, April 30, 1980-April 29, 1981

    Energy Technology Data Exchange (ETDEWEB)

    Henke, B.L.

    1981-08-01

    This final report describes a collaborative extension of an ongoing research program in low-energy x-ray and electron physics into particular areas of immediate need for the diagnostics of plasmas as involved in laser-produced fusion research. It has been for the continued support for one year of a post-doctoral research associate and for three student research assistants who have been applied to the following specific efforts: (1) the continuation of our research on the absolute characterization of x-ray photocathode systems for the 0.1 to 10 keV photon energy region. The research results were applied collaboratively to the design, construction and calibration of photocathodes for time-resolved detection with the XRD and the streak and framing cameras; (2) the design, construction and absolute calibration of optimized, bolt-on spectrographs for the absolute measurement of laser-produced plasma spectra.

  9. Low-energy solar electrons and ions observed at Ulysses February-April, 1991 - The inner heliosphere as a particle reservoir

    Science.gov (United States)

    Roelof, E. C.; Gold, R. E.; Simnett, G. M.; Tappin, S. J.; Armstrong, T. P.; Lanzerotti, L. J.

    1992-01-01

    Ulysses observations at 2.5 AU of 38-315 keV electrons and 61-4752 keV ions during February-April 1991 suggest in several ways that, during periods of sustained high solar activity, the inner heliosphere serves as a 'reservoir' for low-energy solar particles. Particle increases were not associated one-to-one with large X-ray flares because of their poor magnetic connection, yet intensities in March-April remained well above their February levels. The rise phase of the particle event associated with the great flare of 2245UT March 22 lasted most of two days, while throughout the one-week decay phase, the lowest-energy ion fluxes were nearly equal at Ulysses and earth (IMP-8).

  10. Role of topographical defects in organic film growth of 4,4' -biphenyldicarboxylic acid on graphene: A low-energy electron microscopy study

    Science.gov (United States)

    Khokhar, Fawad S.; van Gastel, Raoul; Poelsema, Bene

    2010-11-01

    We have used low-energy electron microscopy (LEEM) to study the formation of self-assembled molecular networks on graphene sheets. 4,4' -biphenyldicarboxylic acid (BDA) molecular networks were grown using organic molecular beam epitaxy. LEEM images provide direct insight in the growth dynamics and show that defects in the graphene play a crucial role in the final morphology of the molecular film that forms. BDA is demonstrated to form hydrogen bond-stabilized chains on graphene. Dark-field LEEM images reveal that the same defects that determine the morphology of the film, also direct the orientation of the domains, highlighting the importance of understanding the role of defects in epitaxial processes on graphene.

  11. DESORPTION OF Te CAPPING LAYER FROM ZnTe (100: AUGER SPECTROSCOPY, LOW-ENERGY ELECTRON DIFFRACTION AND SCANNING TUNNELING MICROSCOPY

    Directory of Open Access Journals (Sweden)

    K. K. Sossoe

    2016-01-01

    Full Text Available The influence of the annealing temperature to desorb a protective Te capping layer of the zinc telluride (ZnTe (100 surface was investigated. The surface reconstruction of the ZnTe (100 upon the removal of a Te capping layer grown by the molecular beam epitaxy was characterized by different methods. Auger spectroscopy brought out the chemical composition of the surface before and after annealing; the Low-energy electron diffraction (LEED gave information about the crystallographic structure. The surface crystallographic configurations of tellurium Te (c (2x2 and Te (c (2x1 are confirmed by scanning tunneling microscopy (STM. Such a study reveals a phase transition from a rich-Te to a poor-Te surface as the annealing temperature increases. 

  12. Detection of the adsorption of water monolayers through the ion oscillation frequency in the magnesium oxide lattice by means of low energy electron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Guevara-Bertsch, M.; Avendaño, E. [Escuela de Física, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Centro de Investigación en Ciencia e Ingeniería de Materiales, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Ramírez-Hidalgo, G. [Centro de Investigación en Ciencia e Ingeniería de Materiales, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Sección de Física Teórica, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Chavarría-Sibaja, A.; Araya-Pochet, J. A. [Centro de Investigación en Ciencia e Ingeniería de Materiales, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Herrera-Sancho, O. A., E-mail: oscar-andrey.herrera@uibk.ac.at [Escuela de Física, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Centro de Investigación en Ciencia e Ingeniería de Materiales, Universidad de Costa Rica, 2060 San Pedro, San José (Costa Rica); Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, Technikerstr. 21a, 6020 Innsbruck (Austria)

    2016-03-15

    We investigate the variation of the oscillation frequency of the Mg{sup 2+} and O{sup 2−} ions in the magnesium oxide lattice due to the interactions of the surface with water monolayers by means of Low Energy Electron Diffraction. Our key result is a new technique to determine the adsorbate vibrations produced by the water monolayers on the surface lattice as a consequence of their change in the surface Debye temperature and its chemical shift. The latter was systematically investigated for different annealing times and for a constant external thermal perturbation in the range of 110–300 K in order to accomplish adsorption or desorption of water monolayers in the surface lattice.

  13. Detection of the adsorption of water monolayers through the ion oscillation frequency in the magnesium oxide lattice by means of low energy electron diffraction

    Directory of Open Access Journals (Sweden)

    M. Guevara-Bertsch

    2016-03-01

    Full Text Available We investigate the variation of the oscillation frequency of the Mg2+ and O2− ions in the magnesium oxide lattice due to the interactions of the surface with water monolayers by means of Low Energy Electron Diffraction. Our key result is a new technique to determine the adsorbate vibrations produced by the water monolayers on the surface lattice as a consequence of their change in the surface Debye temperature and its chemical shift. The latter was systematically investigated for different annealing times and for a constant external thermal perturbation in the range of 110–300 K in order to accomplish adsorption or desorption of water monolayers in the surface lattice.

  14. Magnetism and the low-energy electronic structure of Mott insulators K{sub 2}CoF{sub 4} and SrMnO{sub 3} perovskites

    Energy Technology Data Exchange (ETDEWEB)

    Nalecz, D.M., E-mail: sfnalecz@cyf-kr.edu.pl [Institute of Physics, Pedagogical University, 30-084, Krakow (Poland); Radwanski, R.J. [Institute of Physics, Pedagogical University, 30-084, Krakow (Poland); Center of Solid State Physics, S" n" t Filip 5, 31-150, Krakow (Poland); Ropka, Z. [Center of Solid State Physics, S" n" t Filip 5, 31-150, Krakow (Poland)

    2016-09-01

    For Mott insulators, K{sub 2}CoF{sub 4} and SrMnO{sub 3}, we have calculated, in the purely ionic model, the low-energy electronic structure both in the paramagnetic and magnetic state as well as zero-temperature magnetic moment, its direction and its temperature dependence. We have calculated the octahedral crystal-field strength 10Dq to be 0.98 and 2.25 eV. We claim that for an adequate theoretical description of magnetic properties even small local distortions and the intra-atomic relativistic spin-orbit coupling have to be taken into account. Our studies have revealed a strong interplay of the magnetism, the orbital moment in particular, with the local crystallographic structure. The calculated orbital moment in K{sub 2}CoF{sub 4} is very large, 1.06 μ{sub B}, giving 30% contribution to the total moment - this result points the necessity to “unquench” the orbital magnetism in 3d compounds. We consistently described magnetic and some optical properties of these compounds, containing atoms with incomplete 3d shell, in agreement with their insulating ground state. - Highlights: • The octahedral crystal-field 10Dq amounts to 0.98 and 2.25 eV in K{sub 2}CoF{sub 4} and SrMnO{sub 3}. • The low-energy electronic structures in the magnetic state is displayed. • There is a strong interplay of the magnetism and the local crystal structure. • Temperature dependence of the Mn{sup 4+}- ion magnetic moment has been described. • Relativistic spin-orbit coupling is indispensable for description of 3d magnetism.

  15. A study of Winston-Lutz test on two different electronic portal imaging devices and with low energy imaging.

    Science.gov (United States)

    Ravindran, Paul B

    2016-09-01

    Stereotactic radiosurgery requires sub-millimetre accuracy in patient positioning and target localization. Therefore, verification of the linear accelerator (linac) isocentre and the laser alignment to the isocentre is performed in some clinics prior to the treatment using the Winston-Lutz (W-L) test with films and more recently with images obtained using the electronic portal imaging devices (EPID). The W-L test is performed by acquiring EPID images of a radio-opaque ball of 6 mm diameter (the W-L phantom) placed at the isocentre of the linac at various gantry and table angles, with a predefined small square or circular radiation beam. In this study, the W-L test was performed on two linacs having EPIDs of different size and resolution, viz, a TrueBeam™ linac with aS1000 EPID of size 40 × 30 cm(2) with 1024 × 768 pixel resolution and an EDGE™ linac having an EPID of size 43 × 43 cm(2) with pixel resolution of 1280 × 1280. In order to determine the displacement of the radio-opaque ball centre from the radiation beam centre of the W-L test, an in-house MATLAB™ image processing code was developed using morphological operations. The displacement in radiation beam centre at each gantry and couch position was obtained by determining the distance between the radiation field centre and the radio-opaque ball centre for every image. Since the MATLAB code was based on image processing that was dependent on the image contrast and resolution, the W-L test was also compared for images obtained with different beam energies. The W-L tests were performed for 6 and 8 MV beams on the TrueBeam™ linac and for 2.5 and 6 MV beams on the EDGE™ linac with a higher resolution EPID. It was observed that the images obtained with the EPID of higher resolution resulted in same accuracy in the determination of the displacement between the centres of the radio-opaque ball and the radiation beam, and significant difference was not observed with images acquired with

  16. Investigation of slice emittance using an energy-chirped electron beam in a dispersive section for photo injector characterization at PITZ

    Energy Technology Data Exchange (ETDEWEB)

    Ivanisenko, Yevgeniy

    2012-06-15

    This work describes a transverse slice emittance diagnostics with an RMS temporal resolution down to 2 ps that was implemented at the Photo Injector Test facility in Zeuthen (PITZ). The measurements were performed for several bunch charges generated by a laser pulse that has a flat-top temporal profile of 21-22 ps FWHM duration. This diagnostics allows to study the beam projected emittance compensation with a solenoid magnetic field experimentally and therefore contributes to the beam emittance optimization for the needs of short wavelength linac-based FELs in particular. The diagnostics is based upon the usage of electron bunches which have a correlation between the longitudinal position and the momentum of the bunch particles. This property allows to convert the bunch longitudinal distribution into a transverse one in a dipole magnet. A slit with a narrow opening at the dipole exit selects a fraction of the particle ensemble, a slice, which emittance is analyzed at a screen downstream. Slit scan and quadrupole scan techniques can be used to measure the emittance of the slices. In the experiments it was found that the slice emittance values are 5-10% lower than the projected emittance values, indicating a good effectivity of the solenoid compensation. The emittance obtained using quadrupole scan technique has shown different results when compared to slit scan technique due to a beam halo. The observed beam halo in phase space contributes up to 40% of the emittance value while having only 10% of the bunch charge.

  17. Amorphous silicon carbonitride diaphragm for environmental-cell transmission electron microscope fabricated by low-energy ion beam induced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Matsutani, Takaomi, E-mail: matutani@ele.kindai.ac.jp [Kindai University, 3-4-1 Kowakae, Higashi-osaka, Osaka 577-8502 (Japan); Yamasaki, Kayo [Kindai University, 3-4-1 Kowakae, Higashi-osaka, Osaka 577-8502 (Japan); Imaeda, Norihiro; Kawasaki, Tadahiro [Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan)

    2015-12-15

    An amorphous silicon carbonitride (a-SiCN) diaphragm for an environmental-cell transmission electron microscope (E-TEM) was fabricated by low-energy ion beam induced chemical vapor deposition (LEIBICVD) with hexamethyldisilazane (HMDSN). The films were prepared by using gaseous HMDSN and N{sub 2}{sup +} ions with energies ranging from 300 to 600 eV. The diaphragms were applied to Si (1 0 0) and a Cu grid with 100-μm-diameter holes. With increasing ion energy, these diaphragms became perfectly smooth surfaces (RMS = 0.43 nm at 600 eV), as confirmed by atomic force microscopy and TEM. The diaphragms were amorphous and transparent to 200 kV electrons, and no charge-up was observed. Fourier transform infrared spectra and X-ray photoelectron spectra revealed that the elimination of organic compounds and formation of Si–N and C–N bonds can be promoted in diaphragms by increasing the ion impact energy. The resistance to electron beams and reaction gases in the E-cell was improved when the diaphragm was formed with high ion energy.

  18. Electronic structure and absorption spectra of biferrocenyl and bisfulvalenide diiron radical cations: detection and assignment of new low-energy transitions.

    Science.gov (United States)

    Warratz, Ralf; Aboulfadl, Hanane; Bally, Thomas; Tuczek, Felix

    2009-01-01

    UV-visible/near-IR (NIR)/mid-IR (MIR) solution, solid-state, and matrix-isolation electronic absorption spectra of the Fe(II)-Fe(III) mixed-valent homobimetallic compounds biferrocenyl triiodide (1) and 1',1'''-diethylbiferrocenyltriiodide (2) reveal the presence of a low-energy transition in the MIR region that has not been reported before. The new absorption feature and the known NIR band are both assigned to intervalence charge-transfer (IVCT) transitions. To obtain insight into the electronic structures of 1 and 2, DFT calculations with the BP86 functionals and different basis sets have been performed. Based on the molecular orbital scheme of cation 1, one band corresponds to the transition between the highest occupied d(x(2)-y(2)) orbitals on the two iron centers, whereas the other one is assigned to a transition from a lower-lying d(z(2)) orbital to the d(x(2)-y(2)) orbital. For comparison, the doubly bridged bisfulvalenide diiron cation (3) has been investigated by optical absorption spectroscopy and DFT calculations. The experimental and theoretical results are discussed with respect to the degree of electron localization/delocalization in these systems.

  19. Studies of the surface structures of molecular crystals and of adsorbed molecular monolayers on the (111) crystal faces of platinum and silver by low-energy electron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Firment, L.E.

    1977-01-01

    The structures of molecular crystal surfaces were investigated for the first time by the use of low-energy electron diffraction (LEED). The experimental results from a variety of molecular crystals were examined and compared as a first step towards understanding the properties of these surfaces on a microscopic level. The method of sample preparation employed, vapor deposition onto metal single-crystal substrates at low temperatures in ultrahigh vacuum, allowed concurrent study of the structures of adsorbed monolayers on metal surfaces and of the growth processes of molecular films on metal substrates. The systems investigated were ice, ammonia, naphthalene, benzene, the n-paraffins (C/sub 3/ to C/sub 8/), cyclohexane, trioxane, acetic acid, propionic acid, methanol, and methylamine adsorbed and condensed on both Pt(111) and Ag(111) surfaces. Electron-beam-induced damage of the molecular surfaces was observed after electron exposures of 10/sup -4/ A sec cm/sup -2/ at 20 eV. Aromatic molecular crystal samples were more resistant to damage than samples of saturated molecules. The quality and orientation of the grown molecular crystal films were influenced by substrate preparation and growth conditions. Forty ordered monolayer structures were observed. 110 figures, 22 tables, 162 references.

  20. Review of Low Energy Neutrinos

    CERN Document Server

    Vergados, J D

    2007-01-01

    Some issues regarding low energy neutrinos are reviewed. We focus on three aspects i)We show that by employing very low energy (a few keV) electron neutrinos, neutrino disappearance oscillations can be investigated by detecting recoiling electrons with low threshold spherical gaseous TPC's. In such an experiment, which is sensitive to the small mixing angle theta13, the novel feature is that the oscillation length is so small that the full oscillation takes place inside the detector. Thus one can determine accurately all the oscillation parameters and, in particular, measure or set a good limit on theta13. ii) Low threshold gaseous TPC detectors can also be used in detecting nuclear recoils by exploiting the neutral current interaction. Thus these robust and stable detectors can be employed in supernova neutrino detection. iii) The lepton violating neutrinoless double decay is investigated focusing on how the absolute neutrino mass can be extracted from the data

  1. Integrated ZnO Nano-Electron-Emitter with Self-Modulated Parasitic Tunneling Field Effect Transistor at the Surface of the p-Si/ZnO Junction

    Science.gov (United States)

    Cao, Tao; Luo, Laitang; Huang, Yifeng; Ye, Bing; She, Juncong; Deng, Shaozhi; Chen, Jun; Xu, Ningsheng

    2016-09-01

    The development of high performance nano-electron-emitter arrays with well reliability still proves challenging. Here, we report a featured integrated nano-electron-emitter. The vertically aligned nano-emitter consists of two segments. The top segment is an intrinsically lightly n-type doped ZnO nano-tip, while the bottom segment is a heavily p-type doped Si nano-pillar (denoted as p-Si/ZnO nano-emitter). The anode voltage not only extracted the electron emission from the emitter apex but also induced the inter-band electron tunneling at the surface of the p-Si/ZnO nano-junction. The designed p-Si/ZnO emitter is equivalent to a ZnO nano-tip individually ballasted by a p-Si/ZnO diode and a parasitic tunneling field effect transistor (TFET) at the surface of the p-Si/ZnO junction. The parasitic TFET provides a channel for the supply of emitting electron, while the p-Si/ZnO diode is benefit for impeding the current overloading and prevent the emitters from a catastrophic breakdown. Well repeatable and stable field emission current were obtained from the p-Si/ZnO nano-emitters. High performance nano-emitters was developed using diamond-like-carbon coated p-Si/ZnO tip array (500 × 500), i.e., 178 μA (4.48 mA/cm2) at 75.7 MV/m.

  2. Integrated ZnO Nano-Electron-Emitter with Self-Modulated Parasitic Tunneling Field Effect Transistor at the Surface of the p-Si/ZnO Junction.

    Science.gov (United States)

    Cao, Tao; Luo, Laitang; Huang, Yifeng; Ye, Bing; She, Juncong; Deng, Shaozhi; Chen, Jun; Xu, Ningsheng

    2016-09-22

    The development of high performance nano-electron-emitter arrays with well reliability still proves challenging. Here, we report a featured integrated nano-electron-emitter. The vertically aligned nano-emitter consists of two segments. The top segment is an intrinsically lightly n-type doped ZnO nano-tip, while the bottom segment is a heavily p-type doped Si nano-pillar (denoted as p-Si/ZnO nano-emitter). The anode voltage not only extracted the electron emission from the emitter apex but also induced the inter-band electron tunneling at the surface of the p-Si/ZnO nano-junction. The designed p-Si/ZnO emitter is equivalent to a ZnO nano-tip individually ballasted by a p-Si/ZnO diode and a parasitic tunneling field effect transistor (TFET) at the surface of the p-Si/ZnO junction. The parasitic TFET provides a channel for the supply of emitting electron, while the p-Si/ZnO diode is benefit for impeding the current overloading and prevent the emitters from a catastrophic breakdown. Well repeatable and stable field emission current were obtained from the p-Si/ZnO nano-emitters. High performance nano-emitters was developed using diamond-like-carbon coated p-Si/ZnO tip array (500 × 500), i.e., 178 μA (4.48 mA/cm(2)) at 75.7 MV/m.

  3. Integrated ZnO Nano-Electron-Emitter with Self-Modulated Parasitic Tunneling Field Effect Transistor at the Surface of the p-Si/ZnO Junction

    Science.gov (United States)

    Cao, Tao; Luo, Laitang; Huang, Yifeng; Ye, Bing; She, Juncong; Deng, Shaozhi; Chen, Jun; Xu, Ningsheng

    2016-01-01

    The development of high performance nano-electron-emitter arrays with well reliability still proves challenging. Here, we report a featured integrated nano-electron-emitter. The vertically aligned nano-emitter consists of two segments. The top segment is an intrinsically lightly n-type doped ZnO nano-tip, while the bottom segment is a heavily p-type doped Si nano-pillar (denoted as p-Si/ZnO nano-emitter). The anode voltage not only extracted the electron emission from the emitter apex but also induced the inter-band electron tunneling at the surface of the p-Si/ZnO nano-junction. The designed p-Si/ZnO emitter is equivalent to a ZnO nano-tip individually ballasted by a p-Si/ZnO diode and a parasitic tunneling field effect transistor (TFET) at the surface of the p-Si/ZnO junction. The parasitic TFET provides a channel for the supply of emitting electron, while the p-Si/ZnO diode is benefit for impeding the current overloading and prevent the emitters from a catastrophic breakdown. Well repeatable and stable field emission current were obtained from the p-Si/ZnO nano-emitters. High performance nano-emitters was developed using diamond-like-carbon coated p-Si/ZnO tip array (500 × 500), i.e., 178 μA (4.48 mA/cm2) at 75.7 MV/m. PMID:27654068

  4. Silicon passivation study under low energy electron irradiation conditions; Etude de la passivation du silicium dans des conditions d'irradiation electronique de faible energie

    Energy Technology Data Exchange (ETDEWEB)

    Cluzel, R.

    2010-11-29

    Backside illuminated thinned CMOS (Complementary Metal Oxide Semiconductor) imaging system is a technology developed to increase the signal to noise ratio and the sensibility of such sensors. This configuration is adapted to the electrons detection from the energy range of [1 - 12 keV]. The impinging electron creates by multiplication several hundreds of secondary electrons close to the surface. A P{sup ++} highly-doped passivation layer of the rear face is required to reduce the secondary electron surface recombination rate. Thanks to the potential barrier induced by the P{sup ++} layer, the passivation layer increases the collected charges number and so the sensor collection gain. The goal of this study is to develop some experimental methods in order to determine the effect of six different passivation processes on the collection gain. Beforehand, the energy profile deposited by an incident electron is studied with the combination of Monte-Carlo simulations and some analytical calculations. The final collection gain model shows that the mirror effect from the passivation layer is a key factor at high energies whereas the passivation layer has to be as thin as possible at low energies. A first experimental setup which consists in irradiating P{sup ++}/N large diodes allows to study the passivation process impacts on the surface recombinations. Thanks to a second setup based on a single event upset directly on thinned CMOS sensor, passivation techniques are discriminated in term of mirror effect and the implied spreading charges. The doping atoms activation laser annealing is turn out to be a multiplication gain inhomogeneity source impacting directly the matrix uniformity. (author)

  5. Double emittance exchanger as a bunch compressor for the MaRIE XFEL electron beam line at 1 GeV

    Science.gov (United States)

    Malyzhenkov, Alexander; Carlsten, Bruce E.; Yampolsky, Nikolai A.

    2017-03-01

    We demonstrate an alternative realization of a bunch compressor (specifically, the second bunch compressor for the MaRIE XFEL beamline, 1GeV electron energy) using a double emittance exchanger (EEX) and a telescope in the transverse phase space. We compare our results with a traditional bunch compressor realized via a chicane, taking into account the nonlinear dynamics, Coherent Synchrotron Radiation (CSR) and Space Charge (SC) effects. In particular, we use the Elegant code for tracking particles through the beamline, and analyze the evolution of the eigen-emittances to separate the influence of the CSR/SC effects from the nonlinear dynamics effects. We optimize the scheme parameters to reach a desirable compression factor and minimize the emittance growth. We observe dominant CSR effects in our scheme, resulting in critical emittance growth, and introduce an alternative version of an emittance exchanger with a reduced number of bending magnets to minimize the impact of CSR effects.

  6. Double Emittance Exchanger as a Bunch Compressor for the MaRIE XFEL electron beam line at 1GeV

    Energy Technology Data Exchange (ETDEWEB)

    Malyzhenkov, Alexander [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Northern Illinois Univ., DeKalb, IL (United States); Yampolsky, Nikolai [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Carlsten, Bruce Eric [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-09-22

    We demonstrate an alternative realization of a bunch compressor (specifically the second bunch compressor for the MaRIE XFEL beamline, 1GeV electron energy) using a double emittance exchanger (EEX) and a telescope in the transverse phase space.We compare our results with a traditional bunch compressor realized via chicane, taking into account the nonlinear dynamics, Coherent Synchrotron Radiation (CSR) and Space Charge (SC) effects. In particular, we use the Elegant code for tracking particles through the beam line and analyze the eigen-emittances evolution to separate the influence of the CSR/SC effects from the nonlinear dynamics effects. We optimize the scheme parameters to reach a desirable compression factor and minimize the emittance growth. We observe dominant CSR-effects in our scheme resulting in critical emittance growth and introduce alternative version of an emittance exchanger with a reduced number of bending magnets to minimize the impact of CSR effects.

  7. Low energy electron diffraction (LEED) and sum frequency generation (SFG) vibrational spectroscopy studies of solid-vacuum, solid-air and solid-liquid interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Hoffer, Saskia [Univ. of California, Berkeley, CA (United States)

    2002-01-01

    Electron based surface probing techniques can provide detailed information about surface structure or chemical composition in vacuum environments. The development of new surface techniques has made possible in situ molecular level studies of solid-gas interfaces and more recently, solid-liquid interfaces. The aim of this dissertation is two-fold. First, by using novel sample preparation, Low Energy Electron Diffraction (LEED) and other traditional ultra high vacuum (UHV) techniques are shown to provide new information on the insulator/vacuum interface. The surface structure of the classic insulator NaCl has been determined using these methods. Second, using sum frequency generation (SFG) surface specific vibrational spectroscopy studies were performed on both the biopolymer/air and electrode/electrolyte interfaces. The surface structure and composition of polyetherurethane-silicone copolymers were determined in air using SFG, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). SFG studies of the electrode (platinum, gold and copper)/electrolyte interface were performed as a function of applied potential in an electrochemical cell.

  8. Low energy electron diffraction (LEED) and sum frequency generation (SFG) vibrational spectroscopy studies of solid-vacuum, solid-air and solid-liquid interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Hoffer, Saskia

    2002-08-19

    Electron based surface probing techniques can provide detailed information about surface structure or chemical composition in vacuum environments. The development of new surface techniques has made possible in situ molecular level studies of solid-gas interfaces and more recently, solid-liquid interfaces. The aim of this dissertation is two-fold. First, by using novel sample preparation, Low Energy Electron Diffraction (LEED) and other traditional ultra high vacuum (UHV) techniques are shown to provide new information on the insulator/vacuum interface. The surface structure of the classic insulator NaCl has been determined using these methods. Second, using sum frequency generation (SFG) surface specific vibrational spectroscopy studies were performed on both the biopolymer/air and electrode/electrolyte interfaces. The surface structure and composition of polyetherurethane-silicone copolymers were determined in air using SFG, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). SFG studies of the electrode (platinum, gold and copper)/electrolyte interface were performed as a function of applied potential in an electrochemical cell.

  9. R-matrix calculation of integral and differential cross sections for low-energy electron impact excitations of N2 molecule

    CERN Document Server

    Tashiro, M; Morokuma, Keiji; Tashiro, Motomichi

    2006-01-01

    Low-energy electron impact excitations of N$_2$ molecules are studied using the fixed-bond R-matrix method based on state-averaged complete active space SCF orbitals. Thirteen target electronic states of N$_2$ are included in the model within a valence configuration interaction representations of the target states. Integrated as well as differential cross sections of the $A^{3} \\Sigma_{u}^{+}$, $B^{3} \\Pi_{g}$, $W^{3} \\Delta_{u}$, ${B'}^{3} \\Sigma_{u}^{-}$, ${a'}^{1} \\Sigma_{u}^{-}$, $a^{1} \\Pi_{g}$, $w^{1} \\Delta_{u}$ and $C^{3} \\Pi_{u}$ states are calculated and compared with the previous experimental measurements. These excitations, especially of the higher four states, have not been studied enough theoretically in the previous literature. In general, good agreements are observed both in the integrated and differential cross sections. However, some discrepancies are seen in the integrated cross sections of the $A^{3} \\Sigma_{u}^{+}$ and $C^{3} \\Pi_{u}$ states, especially around a peak structure.

  10. Searching for cavities of various densities in the Earth's crust with a low-energy electron-antineutrino beta-beam

    CERN Document Server

    Argüelles, C A; Gago, A M

    2012-01-01

    We propose searching for deep underground cavities of different densities in the Earth's crust using a long-baseline electron-antineutrino disappearance experiment, realised through a low-energy beta-beam with highly enhanced luminosity. We focus on four real-world cases: water-filled cavities, iron-banded formations, heavier mineral deposits, and regions of abnormal charge accumulation that, supposedly, appear prior to the occurrence of an intense earthquake. The sensitivity to identify cavities attains confidence levels higher than 3$\\sigma$ and 5$\\sigma$ for exposures times of 3 months and 1.5 years, respectively, and cavity densities below 1 g cm$^{-3}$ or above 5 g cm$^{-3}$, with widths greater than 200 km. We reconstruct the cavity density, width, and position, assuming one of them known while keeping the other two free, in each of the aforementioned cases. Finally, we introduce an observable to quantify the presence of a cavity by changing the orientation of the electron-antineutrino beam.

  11. New Insights into the Mechanism Underlying the Synergistic Action of Ionizing Radiation With Platinum Chemotherapeutic Drugs: The Role of Low-Energy Electrons

    Energy Technology Data Exchange (ETDEWEB)

    Rezaee, Mohammad, E-mail: Mohammad.Rezaee@USherbrooke.ca; Hunting, Darel John; Sanche, Léon

    2013-11-15

    Purpose: To investigate the efficiencies of platinum chemotherapeutic drugs (Pt-drugs) in the sensitization of DNA to the direct effects of ionizing radiation and to determine the role of low-energy electrons (LEEs) in this process. Methods and Materials: Complexes of supercoiled plasmid DNA covalently bound to either cisplatin, carboplatin, or oxaliplatin were prepared in different molar ratios. Solid films of DNA and DNA modified by Pt-drugs were irradiated with either 10-KeV or 10-eV electrons. Damages to DNA were quantified by gel electrophoresis, and the yields for damage formation were obtained from exposure–response curves. Results: The presence of an average of 2 Pt-drug–DNA adducts (Pt-adducts) in 3199-bp plasmid DNA increases the probability of a double-strand break by factors of 3.1, 2.5, and 2.4 for carboplatin, cisplatin, and oxaliplatin, respectively. Electrons with energies of 10 eV and 10 KeV interact with Pt-adducts to preferentially enhance the formation of cluster lesions. The maximum increase in radiosensitivity per Pt-adduct is found at ratios up to 3.1 × 10{sup −4} Pt-adducts per nucleotide, which is equivalent to an average of 2 adducts per plasmid. Carboplatin and oxaliplatin show higher efficiencies than cisplatin in the radiosensitization of DNA. Because carboplatin and cisplatin give rise to identical reactive species that attach to DNA, carboplatin must be considered as a better radiosensitizer for equal numbers of Pt-adducts. Conclusion: Platinum chemotherapeutic drugs preferentially enhance the formation of cluster damage to DNA induced by the direct effect of ionizing radiation, and LEEs are the main species responsible for such an enhancement via the formation of electron resonances.

  12. The X-Ray Beam Imager for Transversal Profiling of Low-Emittance Electron Beam at the SPring-8

    CERN Document Server

    Takano, S; Ohkuma, H

    2005-01-01

    We have developed the X-ray beam imager (XBI) at the accelerator diagnostics beamline I of the SPring-8 to observe transverse profiles of small electron beam of a low-emittance synchrotron light source. The XBI is based on a single Fresnel zone plate (FZP) and an X-ray zooming tube (XZT). The electron beam moving in a bending magnet is imaged by the FZP. Monochromatic X-ray is selected by a double crystal monochromator to avoid the effect of chromatic aberration of the FZP. The X-ray images of the electron beam obtained are converted by the XZT to enlarged images in visible light. The XBI has achieved a superior 1 σ spatial resolution in the micron range, and a fast time resolution of 1 ms. It has also realized a vignetting-free field of view larger than 1.5 mm in diameter on the coordinates of the electron beam, which is not easily obtained by imaging optics using two FZPs. With the XBI, we have successfully measured the profiles of the small electron beam having low vertical emittance in the pm ra...

  13. Determining partial differential cross sections for low-energy electron photodetachment involving conical intersections using the solution of a Lippmann-Schwinger equation constructed with standard electronic structure techniques.

    Science.gov (United States)

    Han, Seungsuk; Yarkony, David R

    2011-05-07

    A method for obtaining partial differential cross sections for low energy electron photodetachment in which the electronic states of the residual molecule are strongly coupled by conical intersections is reported. The method is based on the iterative solution to a Lippmann-Schwinger equation, using a zeroth order Hamiltonian consisting of the bound nonadiabatically coupled residual molecule and a free electron. The solution to the Lippmann-Schwinger equation involves only standard electronic structure techniques and a standard three-dimensional free particle Green's function quadrature for which fast techniques exist. The transition dipole moment for electron photodetachment, is a sum of matrix elements each involving one nonorthogonal orbital obtained from the solution to the Lippmann-Schwinger equation. An expression for the electron photodetachment transition dipole matrix element in terms of Dyson orbitals, which does not make the usual orthogonality assumptions, is derived.

  14. SU-E-T-537: Comparison of Intra-Operative Soft X-Rays to Low Energy Electron Beams for Treatment of Superficial Lesions

    Energy Technology Data Exchange (ETDEWEB)

    Chinsky, B; Diak, A; Gros, S; Sethi [Loyola UniversityMedical Center, Maywood, IL (United States)

    2014-06-01

    Purpose: Superficial soft x-ray applicators have recently been designed for use with existing intra-operative radiotherapy systems. These applicators may be used in treating superficial lesions which are conventionally treated with electron beams. The purpose of this abstract is to compare dose distributions of an intra-operative 50kV x-ray unit with low energy electrons for the treatment of superficial lesions. Methods: Dosimetric parameters for 1 and 3-cm diameter Intrabeam superficial x-ray applicators were measured with EBT3 Gafchromic film in a solid water phantom. Depth dose distributions and profiles (d=2, 5, 10 and 15mm) were obtained by prescribing a dose of 400cGy at 5mm depth below the phantom surface. Corresponding dose profiles for 6-MeV electrons were acquired from a Varian Clinac 21EX at 100 SSD. H and D calibration curves were generated for each modality for 0-800cGy. Results: Dose coverage, penumbra, dose uniformity, surface dose, and dose fall-off were examined. Compared to electrons, Intrabeam lateral dose coverage at 5mm depth was 70% larger with a much sharper (1/4) penumbra. Electron isodose levels bulged with depth, whereas Intrabeam isodose levels exhibited a convex cone shape. The Intrabeam dose profiles demonstrated horns in the dose distribution up to a 5mm depth and an exponential dose fall-off. Relative surface dose was higher for the Intrabeam applicators. Treatment times were comparable for both modalities. Conclusions: The very small penumbra of Intrabeam at shallow depths could be useful in treating superficial lesions adjacent to critical structures. The exponential dose fall-off of Intrabeam makes it appealing in the sparing of structures beyond the lesion. However, for lesions past a depth of 5mm, electrons would be desirable as they penetrate farther and provide skin sparing. Intrabeam may be preferable for sites that are difficult to treat with electrons due to mechanical and physical limitations.

  15. Oscillations at low energies

    CERN Document Server

    Dwyer, D A

    2015-01-01

    A concise summary of the "Oscillation at low energies" parallel session at the 2014 Neutrino Oscillation Workshop is provided. Plans to use man-made neutrinos and antineutrinos to determine the neutrino mass hierarchy, search for sterile neutrinos, and to observe coherent neutrino-nucleus scattering were discussed. Potential measurements of solar neutrinos, supernova neutrinos, and geoneutrinos are also summarized.

  16. The structures and dynamics of atomic and molecular adsorbates on metal surfaces by scanning tunneling microscopy and low energy electron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Hyungsuk Alexander [Univ. of California, Berkeley, CA (United States)

    1996-12-01

    Studies of surface structure and dynamics of atoms and molecules on metal surfaces are presented. My research has focused on understanding the nature of adsorbate-adsorbate and adsorbate-substrate interactions through surface studies of coverage dependency and coadsorption using both scanning tunneling microscopy (STM) and low energy electron diffraction (LEED). The effect of adsorbate coverage on the surface structures of sulfur on Pt(111) and Rh(111) was examined. On Pt(111), sulfur forms p(2x2) at 0.25 ML of sulfur, which transforms into a more compressed (√3x√3)R30° at 0.33 ML. On both structures, it was found that sulfur adsorbs only in fcc sites. When the coverage of sulfur exceeds 0.33 ML, it formed more complex c(√3x7)rect structure with 3 sulfur atoms per unit cell. In this structure, two different adsorption sites for sulfur atoms were observed - two on fcc sites and one on hcp site within the unit cell.

  17. Lateral ordering of PTCDA on the clean and the oxygen pre-covered Cu(100) surface investigated by scanning tunneling microscopy and low energy electron diffraction.

    Science.gov (United States)

    Gärtner, Stefan; Fiedler, Benjamin; Bauer, Oliver; Marele, Antonela; Sokolowski, Moritz M

    2014-01-01

    We have investigated the adsorption of perylene-3,4,9,10-tetracarboxylic acid dianhydride (PTCDA) on the clean and on the oxygen pre-covered Cu(100) surface [referred to as (√2 × 2√2)R45° - 2O/Cu(100)] by scanning tunneling microscopy (STM) and low energy electron diffraction (LEED). Our results confirm the (4√2 × 5√2)R45° superstructure of PTCDA/Cu(100) reported by A. Schmidt et al. [J. Phys. Chem. 1995, 99,11770-11779]. However, contrary to Schmidt et al., we have no indication for a dissociation of the PTCDA upon adsorption, and we propose a detailed structure model with two intact PTCDA molecules within the unit cell. Domains of high lateral order are obtained, if the deposition is performed at 400 K. For deposition at room temperature, a significant density of nucleation defects is found pointing to a strong interaction of PTCDA with Cu(100). Quite differently, after preadsorption of oxygen and formation of the (√2 × 2√2)R45° - 2O/Cu(100) superstructure on Cu(100), PTCDA forms an incommensurate monolayer with a structure that corresponds well to that of PTCDA bulk lattice planes.

  18. Structural investigation of 1,1'-biphenyl-4-thiol self-assembled monolayers on Au(111) by scanning tunneling microscopy and low-energy electron diffraction.

    Science.gov (United States)

    Matei, D G; Muzik, H; Gölzhäuser, A; Turchanin, A

    2012-10-02

    Self-assembled monolayers (SAMs) of 1,1'-biphenyl-4-thiol (H-(C(6)H(4))(2)-SH) on Au(111) were prepared from solution or via vapor deposition in ultrahigh vacuum and characterized by scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), and X-ray photoelectron spectroscopy (XPS). In contrast to the typically observed for densely packed alkane-thiol SAMs on Au(111) (√3 × √3)R30° structure, the densely packed aromatic biphenylthiol SAMs prepared by both methods exhibit an unusual hexagonal (2 × 2) structure. Upon annealing at 100 °C, this structure evolves into the (2 × 7√3) structure resulting in the formation of highly ordered pinstripes oriented along the [1 -1 0] directions. Lower density SAMs, prepared by vapor deposition in vacuum, show mixed structures comprising the hexagonal (2 × 2) structure and two rectangular arrangements with the unit cells of (3√3 × 9) and (2√3 × 8). An extinction of the (3√3 × 9) structure in the favor of the (2√3 × 8) structure is observed upon annealing at temperatures of ~100 °C.

  19. Mechanisms of hardening, wear and corrosion improvement of 316 L stainless steel by low energy high current pulsed electron beam surface treatment

    Energy Technology Data Exchange (ETDEWEB)

    Zou, J.X. [Laboratoire d' Etude des Textures et Applications aux Materiaux (LETAM, UMR-CNRS 7078), Universite Paul Verlaine - Metz, Ile du Saulcy, 57045 Metz (France); Shanghai Engineering Research Center of Mg Materials and Applications and School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China); Key Laboratory of Materials Modification by Laser, Electron and Ion beams, Dalian University of Technology, Dalian 116024 (China); Zhang, K.M. [School of Materials Engineering, Shanghai University of Engineering Science, Shanghai 201620 (China); Hao, S.Z.; Dong, C. [Key Laboratory of Materials Modification by Laser, Electron and Ion beams, Dalian University of Technology, Dalian 116024 (China); Grosdidier, T., E-mail: thierry.grosdidier@univ-metz.f [Laboratoire d' Etude des Textures et Applications aux Materiaux (LETAM, UMR-CNRS 7078), Universite Paul Verlaine - Metz, Ile du Saulcy, 57045 Metz (France); Key Laboratory of Materials Modification by Laser, Electron and Ion beams, Dalian University of Technology, Dalian 116024 (China)

    2010-12-01

    The mechanisms of corrosion and wear improvements by low energy high current pulsed electron beam (LEHCPEB) have been investigated for an AISI 316 L steel. Selective purification followed by epitaxial growth occurred in the top surface melted layer (2-3 {mu}m thick) that was softened by tensile stresses and, to a much lower extent, by lower efficiency of MnS precipitation hardening. Electrochemical impedance spectroscopy and potentiodynamic polarization analyses used to model the corrosion behavior revealed that, while craters initiated at MnS inclusions initially served as pitting sites, the resistance was increased by 3 orders of magnitude after sufficient number of pulses by the formation of a homogeneous covering layer. The wear resistance was effectively improved by sub-surface (over 100 {mu}m) work hardening associated with the combine effect of the quasi-static thermal stress and the thermal stress waves. The overall results demonstrate the potential of the LEHCPEB technique for improving concomitantly the corrosion and wear performances of metallic materials.

  20. Formation of microcraters and hierarchically-organized surface structures in TiNi shape memory alloy irradiated with a low-energy, high-current electron beam

    Energy Technology Data Exchange (ETDEWEB)

    Meisner, L. L., E-mail: llm@ispms.tsc.ru; Meisner, S. N., E-mail: myp@ispms.tsc.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); National Research Tomsk State University, Tomsk, 634050 (Russian Federation); Markov, A. B., E-mail: a.markov@hq.tsc.ru; Ozur, G. E., E-mail: vrotshtein@yahoo.com; Yakovlev, E. V., E-mail: msn@ispms.tsc.ru [Institute of High Current Electronics SB RAS, Tomsk, 634055 (Russian Federation); Rotshtein, V. P., E-mail: yakovev@lve.hcei.tsc.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation); Tomsk State Pedagogical University, Tomsk, 634050 (Russian Federation); Gudimova, E. Yu., E-mail: ozur@lve.hcei.tsc.ru [Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation)

    2015-10-27

    The regularities of surface cratering in TiNi alloy irradiated with a low-energy, high-current electron beam (LEHCEB) in dependence on energy density and number of pulses are studied. LEHCEB processing of TiNi samples was carried out using RITM-SP facility. Energy density E{sub s} was varied from 1 to 5 J/cm{sup 2}, pulse duration was 2.5–3.0 μs, the number of pulses n = 1–128. The dominant role of non-metallic inclusions [mainly, TiC(O)] in the nucleation of microcraters was found. It was revealed that at small number of pulses (n = 2), an increase in energy density leads both to increasing average diameter and density of microcraters. An increase in the number of pulses leads to a monotonic decrease in density of microcraters, and, therefore, that of the proportion of the area occupied by microcraters, as well as a decrease in the surface roughness. The multiple LEHCEB melting of TiNi alloy in crater-free modes enables to form quasi-periodical, hierarchically-organized microsized surface structures.

  1. Lateral ordering of PTCDA on the clean and the oxygen pre-covered Cu(100 surface investigated by scanning tunneling microscopy and low energy electron diffraction

    Directory of Open Access Journals (Sweden)

    Stefan Gärtner

    2014-09-01

    Full Text Available We have investigated the adsorption of perylene-3,4,9,10-tetracarboxylic acid dianhydride (PTCDA on the clean and on the oxygen pre-covered Cu(100 surface [referred to as (√2 × 2√2R45° – 2O/Cu(100] by scanning tunneling microscopy (STM and low energy electron diffraction (LEED. Our results confirm the (4√2 × 5√2R45° superstructure of PTCDA/Cu(100 reported by A. Schmidt et al. [J. Phys. Chem. 1995, 99,11770–11779]. However, contrary to Schmidt et al., we have no indication for a dissociation of the PTCDA upon adsorption, and we propose a detailed structure model with two intact PTCDA molecules within the unit cell. Domains of high lateral order are obtained, if the deposition is performed at 400 K. For deposition at room temperature, a significant density of nucleation defects is found pointing to a strong interaction of PTCDA with Cu(100. Quite differently, after preadsorption of oxygen and formation of the (√2 × 2√2R45° – 2O/Cu(100 superstructure on Cu(100, PTCDA forms an incommensurate monolayer with a structure that corresponds well to that of PTCDA bulk lattice planes.

  2. Four-electron, three-orbital model for the low-energy electronic structure of cationic diarylmethanes: notes on a "Pauling Point".

    Science.gov (United States)

    Olsen, Seth

    2012-02-09

    We examine a four-electron, three-orbital complete active space self-consistent field (SA-CASSCF) and multistate multireference perturbation theory (MS-MRPT2) model of the electronic structure associated with the two lowest-lying electronic excitations of a series of cationic diarylmethanes related to Michler's Hydrol Blue. These dyes are of interest because of the sensitivity of their excited-state dynamics to environmental influence in biological and other condensed phases. We show that the model corresponds to an easily understandable physical approximation where the dye electronic structure is mapped onto the π-electron system of an allyl anion. We show that reported trends in solution-state absorbance bands and transition dipole moments associated with the first two electronic excitations can be described within reasonable accuracy by the model. We also show, for Michler's Hydrol Blue, that the four-electron, three-orbital model provides a more balanced description of the electronic difference densities associated with electronic excitation calculated with the full π-electron space than can be achieved with active space models intermediate between these limits. The valence excitation energies predicted by the model are not sensitive to the underlying basis set, so that considerable computational savings may be possible by using split-valence basis sets with a limited number of polarization functions. We conclude that the model meets the criteria for a "Pauling Point": a point where the cancellation of large errors leads to physically balanced model, and where further elaboration degrades, rather than improves, the quality of description. We advocate that this Pauling Point be exploited in condensed-phase dynamical models where the computational overhead associated with the electronic structure must kept to a minimum (for example, nonadiabatic dynamics simulations coupled to QM/MM environmental models).

  3. Structure of the hydrogen stabilized MgO(1 1 1)-(1 × 1) surface from low energy electron diffraction (LEED)

    Science.gov (United States)

    Poon, H. C.; Hu, X. F.; Chamberlin, S. E.; Saldin, D. K.; Hirschmugl, C. J.

    2006-06-01

    A structural study has been performed on the MgO(1 1 1)-(1 × 1) surface by low energy electron diffraction (LEED) using experimental data obtained with a delay-line-detector LEED (DLD-LEED) system to minimize electron damage. It was found that the surface is terminated by a hydroxide layer with the top O-Mg interlayer spacing equal to 1.02 Å, which is close to the spacings between Mg and O planes in bulk brucite crystals (Mg(OH) 2). This is in good agreement with a recent study using photoelectron diffraction (PhD) spectroscopy and density functional theory calculation (DFT) [V.K. Lazarov, R. Plass, H.-C. Poon, D.K. Saldin, M. Weinert, S.A. Chambers, M. Gajdardziska-Josifovska, Phys. Rev. B 71 (2005) 115434]. The second interlayer spacing shows a small expansion of 3% and the third is bulk-like, while the DFT calculation predicted that the spacings below the top one are all bulk-like. This result clearly favors hydroxylation [K. Refson, R.A. Wogelius, D.G. Fraser, M.C. Payne, M.H. Lee, V. Milman, Phys. Rev. B 52 (1995) 10823] as a way of stabilizing the MgO(1 1 1) surface at low temperature over metallization, which has a top layer spacing of 0.86 Å for O termination and 1.25 Å for Mg termination [Lazarov et al. 2005; T. Tsukada, T. Hoshino, Phys. Soc. Jpn. 51 (1982) 2562, J. Goniakowski, C. Noguera, Phys. Rev. B 60 (1999) 16120].

  4. To tilt or not to tilt: Correction of the distortion caused by inclined sample surfaces in low-energy electron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Sojka, Falko, E-mail: falko.sojka@uni-jena.de [Friedrich Schiller University Jena, Institute of Solid State Physics, Helmholtzweg 5, 07743 Jena (Germany); Meissner, Matthias; Zwick, Christian; Forker, Roman [Friedrich Schiller University Jena, Institute of Solid State Physics, Helmholtzweg 5, 07743 Jena (Germany); Vyshnepolsky, Michael; Klein, Claudius; Horn-von Hoegen, Michael [University of Duisburg-Essen, Department of Physics, Lotharstr. 1, 47057 Duisburg (Germany); Fritz, Torsten, E-mail: torsten.fritz@uni-jena.de [Friedrich Schiller University Jena, Institute of Solid State Physics, Helmholtzweg 5, 07743 Jena (Germany)

    2013-10-15

    Low-energy electron diffraction (LEED) is a widely employed technique for the structural characterization of crystalline surfaces and epitaxial adsorbates. For technical reasons the accessible reciprocal space is limited at a given primary electron energy E. This limitation may be overcome by sweeping E to observe higher diffraction orders decisively enhancing the quantitative examination. Yet, in many cases, such as molecular films with rather large unit cells, the adsorbate reflexes become less pronounced at energies high enough to observe substrate reflexes. One possibility to overcome this problem is an intentional inclination of the sample surface during the measurement at the expense of the quantitative interpretability of then severely distorted diffraction patterns. Here, we introduce a correction method for the axially symmetric distortion in LEED images of tilted samples. We provide experimental confirmation for micro-channel plate LEED and spot-profile analysis LEED instruments using the (7×7) reconstructed surface of a Si(111) single crystal as a reference sample. Finally, we demonstrate that the correction of this distortion considerably improves the quantitative analysis of diffraction patterns of adsorbates since substrate and adsorbate reflexes can be evaluated simultaneously. As an illustrative example we have chosen an epitaxial monolayer of 3,4,9,10-perylenetetracarboxylic dianhydride on Ag(111) that is known to form a commensurate superstructure. - Highlights: • We introduce a method to correct distortions in LEED patterns of tilted surfaces. • Higher diffraction orders unobservable at higher beam energies can be evaluated. • Our procedure makes LEED patterns of tilted samples quantitatively analyzable. • Experimental confirmation with SPA-LEED and MCP-LEED is presented. • The method is applied to PTCDA on Ag(111) confirming earlier literature values.

  5. Extension of the T{sub z} = {minus}3/2, A = 4n + 1 series of beta-delayed proton emitters to {sup 65}Se and {sup 73}Sr, and low energy beta-delayed proton emission from the T{sub z} = {minus}3/2, A = 4n + 3 nucleus {sup 23}Al

    Energy Technology Data Exchange (ETDEWEB)

    Batchelder, J.C.

    1993-12-01

    The series of known Tz = {minus}3/2, A = 4n + 1 nuclei has been extended to include the previously undiscovered isotopes {sup 65}Se and {sup 73}Sr, through the observation of beta-delayed proton emission via the isobaric analog state (IAS) of the beta-daughter (emitter). Due to the relatively large proton energies involved, these experiments were conducted using standard Si-Si {Delta}E-E telescopes. Beta-delayed protons arising from {sup 65}Se have been observed at an energy (laboratory) of 3.55 {plus_minus} 0.03 MeV, corresponding to the decay of the T = 3/2 isobaric analog state in {sup 65}As to the ground state of {sup 64}Ge. Similarly, beta-delayed protons from {sup 73}Sr at an energy of 3.75 {plus_minus} 0.04 MeV have been observed, corresponding to decay of the T = 3/2 isobaric analog state in {sup 73}Rb to the ground state of {sup 72}Kr. From the energies of these proton transitions, an improved prediction of the mass excesses of the two parent nuclei ({sup 65}Se and {sup 73}Sr) is made through the use of a Coulomb displacement formula. These predictions are {minus}33.41 {plus_minus} 0.26 and {minus}31.87 {plus_minus} 0.24 MeV for {sup 65}Se and {sup 73}Sr, respectively. Studies of low energy (down to {approximately}200 keV) beta-delayed protons from {sup 23}Al necessitated that a particle identification telescope with a low energy threshold for observation and identification of protons be developed. {sup 23}Al is of interest because of its role in the breakout of the hot CNO cycle leading to the astrophysical rp process.

  6. R-matrix calculation of differential cross sections for low-energy electron collisions with ground and electronically excited state O2 molecules

    CERN Document Server

    Tashiro, M; Tennyson, J; Tashiro, Motomichi; Morokuma, Keiji; Tennyson, Jonathan

    2006-01-01

    Differential cross sections for electron collisions with the O$_2$ molecule in its ground ${X}^{3}\\Sigma_g^-$ state, as well as excited ${a}^{1}\\Delta_g$ and ${b}^{1}\\Sigma_g^+$ states are calculated. As previously, the fixed-bond R-matrix method based on state-averaged complete active space SCF orbitals is employed. In additions to elastic scattering of electron with the O$_2$ ${X}^{3}\\Sigma_g^-$, ${a}^{1}\\Delta_g$ and ${b}^{1}\\Sigma_g^+$ states, electron impact excitation from the ${X}^{3}\\Sigma_g^-$ state to the ${a}^{1}\\Delta_g$ and ${b}^{1}\\Sigma_g^+$ states as well as '6 eV states' of ${c}^{1}\\Sigma_u^{-}$, ${A'}^{3}\\Delta_u$ and ${A}^{3}\\Sigma_u^{+}$ states is studied. Differential cross sections for excitation to the '6 eV states' have not been calculated previously. Electron impact excitation to the ${b}^{1}\\Sigma_g^+$ state from the metastable ${a}^{1}\\Delta_g$ state is also studied. For electron impact excitation from the O$_2$ ${X}^{3}\\Sigma_g^-$ state to the ${b}^{1}\\Sigma_g^+$ state, our results...

  7. Energetic particle precipitation in ECHAM5/MESSy1 – Part 1: Downward transport of upper atmospheric NOx produced by low energy electrons

    Directory of Open Access Journals (Sweden)

    C. Brühl

    2008-12-01

    Full Text Available The atmospheric chemistry general circulation model ECHAM5/MESSy1 has been extended by processes that parameterize particle precipitation. Several types of particle precipitation that directly affect NOy and HOx concentrations in the middle atmosphere are accounted for and discussed in a series of papers. In the companion paper, the ECHAM5/MESSy1 solar proton event parameterization is discussed, while in the current paper we focus on low energy electrons (LEE that produce NOx in the upper atmosphere. For the flux of LEE NOx into the top of the model domain a novel technique which can be applied to most atmospheric chemistry general circulation models has been developed and is presented here. The technique is particularly useful for models with an upper boundary between the stratopause and mesopause and therefore cannot directly incorporate upper atmospheric NOx production. The additional NOx source parametrization is based on a measure of geomagnetic activity, the Ap index, which has been shown to be a good proxy for LEE NOx interannual variations. HALOE measurements of LEE NOx that has been transported into the stratosphere are used to develop a scaling function which yields a flux of NOx that is applied to the model top. We describe the implementation of the parameterization as the submodel SPACENOX in ECHAM5/MESSy1 and discuss the results from test simulations. The NOx enhancements and associated effects on ozone are shown to be in good agreement with independent measurements. Ap index data is available for almost one century, thus the parameterization is suitable for simulations of the recent climate.

  8. Energetic particle precipitation in ECHAM5/MESSy1 – Part 1: Downward transport of upper atmospheric NOx produced by low energy electrons

    Directory of Open Access Journals (Sweden)

    C. Brühl

    2009-04-01

    Full Text Available The atmospheric chemistry general circulation model ECHAM5/MESSy1 has been extended by processes that parameterise particle precipitation. Several types of particle precipitation that directly affect NOy and HOx concentrations in the middle atmosphere are accounted for and discussed in a series of papers. In the companion paper, the ECHAM5/MESSy1 solar proton event parametrisation is discussed, while in the current paper we focus on low energy electrons (LEE that produce NOx in the upper atmosphere. For the flux of LEE NOx into the top of the model domain a novel technique which can be applied to most atmospheric chemistry general circulation models has been developed and is presented here. The technique is particularly useful for models with an upper boundary between the stratopause and mesopause and therefore cannot directly incorporate upper atmospheric NOx production. The additional NOx source parametrisation is based on a measure of geomagnetic activity, the Ap index, which has been shown to be a good proxy for LEE NOx interannual variations. HALOE measurements of LEE NOx that has been transported into the stratosphere are used to develop a scaling function which yields a flux of NOx that is applied to the model top. We describe the implementation of the parametrisation as the submodel SPACENOX in ECHAM5/MESSy1 and discuss the results from test simulations. The NOx enhancements are shown to be in good agreement with independent measurements. Ap index data is available for almost one century, thus the parametrisation is suitable for simulations of the recent climate.

  9. High Stability Electron Field Emitters Synthesized via the Combination of Carbon Nanotubes and N₂-Plasma Grown Ultrananocrystalline Diamond Films.

    Science.gov (United States)

    Chang, Ting-Hsun; Hsieh, Ping-Yen; Kunuku, Srinivasu; Lou, Shiu-Cheng; Manoharan, Divinah; Leou, Keh-Chyang; Lin, I-Nan; Tai, Nyan-Hwa

    2015-12-16

    An electron field emitter with superior electron field emission (EFE) properties and improved lifetime stability is being demonstrated via the combination of carbon nanotubes and the CH4/N2 plasma grown ultrananocrystalline diamond (N-UNCD) films. The resistance of the carbon nanotubes to plasma ion bombardment is improved by the formation of carbon nanocones on the side walls of the carbon nanotubes, thus forming strengthened carbon nanotubes (s-CNTs). The N-UNCD films can thus be grown on s-CNTs, forming N-UNCD/s-CNTs carbon nanocomposite materials. The N-UNCD/s-CNTs films possess good conductivity of σ = 237 S/cm and marvelous EFE properties, such as low turn-on field of (E0) = 3.58 V/μm with large EFE current density of (J(e)) = 1.86 mA/cm(2) at an applied field of 6.0 V/μm. Moreover, the EFE emitters can be operated under 0.19 mA/cm(2) for more than 350 min without showing any sign of degradation. Such a superior EFE property along with high robustness characteristic of these combination of materials are not attainable with neither N-UNCD films nor s-CNTs films alone. Transmission electron microscopic investigations indicated that the N-UNCD films contain needle-like diamond grains encased in a few layers of nanographitic phase, which enhanced markedly the transport of electrons in the N-UNCD films. Moreover, the needle-like diamond grains were nucleated from the s-CNTs without the necessity of forming the interlayer that facilitate the transport of electrons crossing the diamond-to-Si interface. Both these factors contributed to the enhanced EFE behavior of the N-UNCD/s-CNTs films.

  10. Low-energy neutrinos

    CERN Document Server

    Ludhova, Livia

    2016-01-01

    There exist several kinds of sources emitting neutrinos in the MeV energy range. These low-energy neutrinos from different sources can be often detected by the same multipurpose detectors. The status-of-art of the feld of solar neutrinos, geoneutrinos, and the search for sterile neutrino with artifcial neutrino sources is provided here; other neutrino sources, as for example reactor or high-energy neutrinos, are described elsewhere. For each of these three felds, the present-day motivation and open questions, as well as the latest experimental results and future perspectives are discussed.

  11. Low Energy Hadron Physics

    CERN Document Server

    Pennington, Michael R

    2000-01-01

    Ask a group of particle theorists about low energy hadron physics and they will say that this is a subject that belongs to the age of the dinosaurs. However, it is GeV physics that controls the outcome of every hadronic interaction at almost every energy. Confinement of quarks and gluons (and any other super-constituents) means that it is the femto-universe that determines what experiments detect. What we have to learn at the start of the 21st century is discussed.

  12. Low Energy Nuclear Reactions?

    CERN Document Server

    CERN. Geneva; Faccini, R.

    2014-01-01

    After an introduction to the controversial problem of Low Energy Nuclear Reactions (LENR) catalyzed by neutrons on metallic hydride surfaces we present the results of an experiment, made in collaboration with ENEA Labs in Frascati, to search neutrons from plasma discharges in electrolytic cells. The negative outcome of our experiment goes in the direction of ruling out those theoretical models expecting LENR to occur in condensed matter systems under specific conditions. Our criticism on the theoretical foundations of such models will also be presented.

  13. Generating femtosecond X-ray pulses using an emittance-spoiling foil in free-electron lasers

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Y., E-mail: ding@slac.stanford.edu; Coffee, R.; Decker, F.-J.; Emma, P.; Field, C.; Huang, Z.; Krejcik, P.; Krzywinski, J.; Loos, H.; Lutman, A.; Marinelli, A.; Maxwell, T. J.; Turner, J. [SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Behrens, C. [Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22607 Hamburg (Germany); Helml, W. [Technische Universität München, James-Franck-Straße 1, 85748 Garching (Germany)

    2015-11-09

    Generation of femtosecond to sub-femtosecond pulses is attracting much attention in X-ray free-electron laser user community. One method is to use a slotted, emittance-spoiling foil which was proposed before (P. Emma et al., Phys. Rev. Lett. 92, 074801 (2004)) and has been widely used at the Linac Coherent Light Source. Direct experimental characterization of the slotted-foil performance was previously unfeasible due to a lack of appropriate diagnostics. With a recently installed X-band radio-frequency transverse deflector, we are able to characterize the electron bunch spoiling effect and X-ray pulse when using the slotted foil. We show that few-femtosecond X-ray pulses are generated with flexible control of the single-pulse duration or double-pulse separation with comparison to the theoretical model.

  14. Formation of compressed flat electron beams with high transverse-emittance ratios

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, J. [Fermilab; Institute of Fluid Physics, CAEP, China; Piot, P. [Northern Illinois University; Fermilab; Mihalcea, D. [Northern Illinois University; Prokop, C. R. [Northern Illinois University

    2014-08-01

    Flat beams—beams with asymmetric transverse emittances—have important applications in novel light-source concepts and advanced-acceleration schemes and could possibly alleviate the need for damping rings in lepton colliders. Over the last decade, a flat beam generation technique based on the conversion of an angular-momentum-dominated beam was proposed and experimentally tested. In this paper we explore the production of compressed flat beams. We especially investigate and optimize the flat beam transformation for beams with substantial fractional energy spread. We use as a simulation example the photoinjector of Fermilab’s Advanced Superconducting Test Accelerator. The optimizations of the flat beam generation and compression at Advanced Superconducting Test Accelerator were done via start-to-end numerical simulations for bunch charges of 3.2 nC, 1.0 nC, and 20 pC at ~37 MeV. The optimized emittances of flat beams with different bunch charges were found to be 0.25 μm (emittance ratio is ~400), 0.13 μm, 15 nm before compression, and 0.41 μm, 0.20 μm, 16 nm after full compression, respectively, with peak currents as high as 5.5 kA for a 3.2-nC flat beam. These parameters are consistent with requirements needed to excite wakefields in asymmetric dielectric-lined waveguides or produce significant photon flux using small-gap micro-undulators.

  15. Compact Measurement Station for Low Energy Proton Beams

    CERN Document Server

    Yildiz, H.

    2017-01-01

    A compact, remote controlled, cost efficient diagnostic station has been developed to measure the charge, the profile and the emittance for low energy proton beams. It has been installed and tested in the proton beam line of the Project Prometheus at SANAEM of the Turkish Atomic Energy Authority.

  16. Space charge compensation in the Linac4 low energy beam transport line with negative hydrogen ions

    Energy Technology Data Exchange (ETDEWEB)

    Valerio-Lizarraga, Cristhian A., E-mail: cristhian.alfonso.valerio.lizarraga@cern.ch [CERN, Geneva (Switzerland); Departamento de Investigación en Física, Universidad de Sonora, Hermosillo (Mexico); Lallement, Jean-Baptiste; Lettry, Jacques; Scrivens, Richard [CERN, Geneva (Switzerland); Leon-Monzon, Ildefonso [Facultad de Ciencias Fisico-Matematicas, Universidad Autónoma de Sinaloa, Culiacan (Mexico); Midttun, Øystein [CERN, Geneva (Switzerland); University of Oslo, Oslo (Norway)

    2014-02-15

    The space charge effect of low energy, unbunched ion beams can be compensated by the trapping of ions or electrons into the beam potential. This has been studied for the 45 keV negative hydrogen ion beam in the CERN Linac4 Low Energy Beam Transport using the package IBSimu [T. Kalvas et al., Rev. Sci. Instrum. 81, 02B703 (2010)], which allows the space charge calculation of the particle trajectories. The results of the beam simulations will be compared to emittance measurements of an H{sup −} beam at the CERN Linac4 3 MeV test stand, where the injection of hydrogen gas directly into the beam transport region has been used to modify the space charge compensation degree.

  17. Space charge compensation in the Linac4 low energy beam transport line with negative hydrogen ions.

    Science.gov (United States)

    Valerio-Lizarraga, Cristhian A; Lallement, Jean-Baptiste; Leon-Monzon, Ildefonso; Lettry, Jacques; Midttun, Øystein; Scrivens, Richard

    2014-02-01

    The space charge effect of low energy, unbunched ion beams can be compensated by the trapping of ions or electrons into the beam potential. This has been studied for the 45 keV negative hydrogen ion beam in the CERN Linac4 Low Energy Beam Transport using the package IBSimu [T. Kalvas et al., Rev. Sci. Instrum. 81, 02B703 (2010)], which allows the space charge calculation of the particle trajectories. The results of the beam simulations will be compared to emittance measurements of an H(-) beam at the CERN Linac4 3 MeV test stand, where the injection of hydrogen gas directly into the beam transport region has been used to modify the space charge compensation degree.

  18. Space charge compensation in the Linac4 low energy beam transport line with negative hydrogen ions

    Science.gov (United States)

    Valerio-Lizarraga, Cristhian A.; Lallement, Jean-Baptiste; Leon-Monzon, Ildefonso; Lettry, Jacques; Midttun, Øystein; Scrivens, Richard

    2014-02-01

    The space charge effect of low energy, unbunched ion beams can be compensated by the trapping of ions or electrons into the beam potential. This has been studied for the 45 keV negative hydrogen ion beam in the CERN Linac4 Low Energy Beam Transport using the package IBSimu [T. Kalvas et al., Rev. Sci. Instrum. 81, 02B703 (2010)], which allows the space charge calculation of the particle trajectories. The results of the beam simulations will be compared to emittance measurements of an H- beam at the CERN Linac4 3 MeV test stand, where the injection of hydrogen gas directly into the beam transport region has been used to modify the space charge compensation degree.

  19. Non-Gaussian beam dynamics in low energy antiproton storage rings

    Science.gov (United States)

    Resta-López, J.; Hunt, J. R.; Welsch, C. P.

    2016-10-01

    In low energy antiproton facilities, where electron cooling is fundamental, the cooling forces together with heating phenomena causing emittance blow-up, such as Intra Beam Scattering (IBS), result in highly non-Gaussian beam distributions. In these cases, a precise simulation of IBS effects is essential to realistically evaluate the long term beam evolution, taking into account the non-Gaussian characteristics of the beam. Here, we analyse the beam dynamics in the Extra Low ENergy Antiproton ring (ELENA), which is a new small synchrotron currently being constructed at CERN to decelerate antiprotons to energies as low as 100 keV. Simulations are performed using the code BETACOOL, comparing different models of IBS.

  20. High field – low energy muon ionization cooling channel

    Directory of Open Access Journals (Sweden)

    Hisham Kamal Sayed

    2015-09-01

    Full Text Available Muon beams are generated with large transverse and longitudinal emittances. In order to achieve the low emittances required by a muon collider, within the short lifetime of the muons, ionization cooling is required. Cooling schemes have been developed to reduce the muon beam 6D emittances to ≈300  μm-rad in transverse and ≈1–1.5  mm in longitudinal dimensions. The transverse emittance has to be further reduced to ≈50–25  μm-rad with an upper limit on the longitudinal emittance of ≈76  mm in order to meet the high-energy muon collider luminosity requirements. Earlier studies of the transverse cooling of low energy muon beams in high field magnets showed a promising performance, but did not include transverse or longitudinal matching between the stages. In this study we present the first complete design of the high field-low energy ionization cooling channel with transverse and longitudinal matching. The channel design was based on strong focusing solenoids with fields of 25–30 T and low momentum muon beam starting at 135  MeV/c and gradually decreasing. The cooling channel design presented here is the first to reach ≈50 micron scale emittance beam. We present the channel’s optimized design parameters including the focusing solenoid fields, absorber parameters and the transverse and longitudinal matching.

  1. Current gain in sub-10 nm base GaN tunneling hot electron transistors with AlN emitter barrier

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Zhichao, E-mail: zcyang.phys@gmail.com; Zhang, Yuewei; Nath, Digbijoy N.; Rajan, Siddharth [Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Khurgin, Jacob B. [Department of Electrical and Computer Engineering, The Johns Hopkins University, Baltimore, Maryland 21218 (United States)

    2015-01-19

    We report on Gallium Nitride-based tunneling hot electron transistor amplifier with common-emitter current gain greater than 1. Small signal current gain up to 5 and dc current gain of 1.3 were attained in common-emitter configuration with collector current density in excess of 50 kA/cm{sup 2}. The use of a combination of 1 nm GaN/3 nm AlN layers as an emitter tunneling barrier was found to improve the energy collimation of the injected electrons. These results represent demonstration of unipolar vertical transistors in the III-nitride system that can potentially lead to higher frequency and power microwave devices.

  2. Manipulating the Electronic Excited State Energies of Pyrimidine-Based Thermally Activated Delayed Fluorescence Emitters To Realize Efficient Deep-Blue Emission.

    Science.gov (United States)

    Komatsu, Ryutaro; Ohsawa, Tatsuya; Sasabe, Hisahiro; Nakao, Kohei; Hayasaka, Yuya; Kido, Junji

    2017-02-08

    The development of efficient and robust deep-blue emitters is one of the key issues in organic light-emitting devices (OLEDs) for environmentally friendly, large-area displays or general lighting. As a promising technology that realizes 100% conversion from electrons to photons, thermally activated delayed fluorescence (TADF) emitters have attracted considerable attention. However, only a handful of examples of deep-blue TADF emitters have been reported to date, and the emitters generally show large efficiency roll-off at practical luminance over several hundreds to thousands of cd m(-2), most likely because of the long delayed fluorescent lifetime (τd). To overcome this problem, we molecularly manipulated the electronic excited state energies of pyrimidine-based TADF emitters to realize deep-blue emission and reduced τd. We then systematically investigated the relationships among the chemical structure, properties, and device performances. The resultant novel pyrimidine emitters, called Ac-XMHPMs (X = 1, 2, and 3), contain different numbers of bulky methyl substituents at acceptor moieties, increasing the excited singlet (ES) and triplet state (ET) energies. Among them, Ac-3MHPM, with a high ET of 2.95 eV, exhibited a high external quantum efficiency (ηext,max) of 18% and an ηext of 10% at 100 cd m(-2) with Commission Internationale de l'Eclairage chromaticity coordinates of (0.16, 0.15). These efficiencies are among the highest values to date for deep-blue TADF OLEDs. Our molecular design strategy provides fundamental guidance to design novel deep-blue TADF emitters.

  3. Complete-active-space second-order perturbation theory (CASPT2//CASSCF) study of the dissociative electron attachment in canonical DNA nucleobases caused by low-energy electrons (0-3 eV)

    Energy Technology Data Exchange (ETDEWEB)

    Francés-Monerris, Antonio; Segarra-Martí, Javier; Merchán, Manuela; Roca-Sanjuán, Daniel, E-mail: Daniel.Roca@uv.es [Instituto de Ciencia Molecular, Universitat de València, P.O. Box 22085, 46071 València (Spain)

    2015-12-07

    Low-energy (0-3 eV) ballistic electrons originated during the irradiation of biological material can interact with DNA/RNA nucleobases yielding transient-anion species which undergo decompositions. Since the discovery that these reactions can eventually lead to strand breaking of the DNA chains, great efforts have been dedicated to their study. The main fragmentation at the 0-3 eV energy range is the ejection of a hydrogen atom from the specific nitrogen positions. In the present study, the methodological approach introduced in a previous work on uracil [I. González-Ramírez et al., J. Chem. Theory Comput. 8, 2769-2776 (2012)] is employed to study the DNA canonical nucleobases fragmentations of N–H bonds induced by low-energy electrons. The approach is based on minimum energy path and linear interpolation of internal coordinates computations along the N–H dissociation channels carried out at the complete-active-space self-consistent field//complete-active-space second-order perturbation theory level. On the basis of the calculated theoretical quantities, new assignations for the adenine and cytosine anion yield curves are provided. In addition, the π{sub 1}{sup −} and π{sub 2}{sup −} states of the pyrimidine nucleobases are expected to produce the temporary anions at electron energies close to 1 and 2 eV, respectively. Finally, the present theoretical results do not allow to discard neither the dipole-bound nor the valence-bound mechanisms in the range of energies explored, suggesting that both possibilities may coexist in the experiments carried out with the isolated nucleobases.

  4. Complete-active-space second-order perturbation theory (CASPT2//CASSCF) study of the dissociative electron attachment in canonical DNA nucleobases caused by low-energy electrons (0-3 eV)

    Science.gov (United States)

    Francés-Monerris, Antonio; Segarra-Martí, Javier; Merchán, Manuela; Roca-Sanjuán, Daniel

    2015-12-01

    Low-energy (0-3 eV) ballistic electrons originated during the irradiation of biological material can interact with DNA/RNA nucleobases yielding transient-anion species which undergo decompositions. Since the discovery that these reactions can eventually lead to strand breaking of the DNA chains, great efforts have been dedicated to their study. The main fragmentation at the 0-3 eV energy range is the ejection of a hydrogen atom from the specific nitrogen positions. In the present study, the methodological approach introduced in a previous work on uracil [I. González-Ramírez et al., J. Chem. Theory Comput. 8, 2769-2776 (2012)] is employed to study the DNA canonical nucleobases fragmentations of N-H bonds induced by low-energy electrons. The approach is based on minimum energy path and linear interpolation of internal coordinates computations along the N-H dissociation channels carried out at the complete-active-space self-consistent field//complete-active-space second-order perturbation theory level. On the basis of the calculated theoretical quantities, new assignations for the adenine and cytosine anion yield curves are provided. In addition, the π1- and π2- states of the pyrimidine nucleobases are expected to produce the temporary anions at electron energies close to 1 and 2 eV, respectively. Finally, the present theoretical results do not allow to discard neither the dipole-bound nor the valence-bound mechanisms in the range of energies explored, suggesting that both possibilities may coexist in the experiments carried out with the isolated nucleobases.

  5. Inside bluetooth low energy

    CERN Document Server

    Gupta, Naresh

    2013-01-01

    Bluetooth Low Energy (LE) is one of the latest enhancement to Bluetooth technology and, as the name suggests, it is aimed at ultra low power devices, such as heart rate monitors, thermometers, and sensors. Due to very low power consumption, devices compliant with this standard can operate for several years on coin cell batteries without the need for recharging. This cutting-edge book helps you understand the whats , whys , and hows of Bluetooth LE. It includes a broad view of the technology, identifies the various building blocks, and explains how they come together. You also find discussions on Bluetooth basics, providing the background information needed to master Bluetooth LE.The book explains the architecture of Bluetooth LE stack and the functionality provided by each of the layers. You find expert guidance in setting up your own system in a quick and efficient manner with inexpensive, easily available hardware and just a couple of PCs running Linux. This unique volume features two chapters that are dedi...

  6. Carbon and metal nanotube hybrid structures on graphene as efficient electron field emitters

    Science.gov (United States)

    Heo, Kwang; Lee, Byung Yang; Lee, Hyungwoo; Cho, Dong-guk; Arif, Muhammad; Kim, Kyu Young; Choi, Young Jin; Hong, Seunghun

    2016-07-01

    We report a facile and efficient method for the fabrication of highly-flexible field emission devices by forming tubular hybrid structures based on carbon nanotubes (CNTs) and nickel nanotubes (Ni NTs) on graphene-based flexible substrates. By employing an infiltration process in anodic alumina oxide (AAO) templates followed by Ni electrodeposition, we could fabricate CNT-wrapped Ni NT/graphene hybrid structures. During the electrodeposition process, the CNTs served as Ni nucleation sites, resulting in a large-area array of high aspect-ratio field emitters composed of CNT-wrapped Ni NT hybrid structures. As a proof of concepts, we demonstrate that high-quality flexible field emission devices can be simply fabricated using our method. Remarkably, our proto-type field emission devices exhibited a current density higher by two orders of magnitude compared to other devices fabricated by previous methods, while maintaining its structural integrity in various bending deformations. This novel fabrication strategy can be utilized in various applications such as optoelectronic devices, sensors and energy storage devices.

  7. Controlled growth of carbon nanotube-graphene hybrid materials for flexible and transparent conductors and electron field emitters.

    Science.gov (United States)

    Nguyen, Duc Dung; Tai, Nyan-Hwa; Chen, Szu-Ying; Chueh, Yu-Lun

    2012-01-21

    We report a versatile synthetic process based on rapid heating and cooling chemical vapor deposition for the growth of carbon nanotube (CNT)-graphene hybrid materials where the thickness of graphene and density of CNTs are properly controlled. Graphene films are demonstrated as an efficient barrier layer for preventing poisoning of iron nanoparticles, which catalyze the growth of CNTs on copper substrates. Based on this method, the opto-electronic and field emission properties of graphene integrated with CNTs can be remarkably tailored. A graphene film exhibits a sheet resistance of 2.15 kΩ sq(-1) with a transmittance of 85.6% (at 550 nm), while a CNT-graphene hybrid film shows an improved sheet resistance of 420 Ω sq(-1) with an optical transmittance of 72.9%. Moreover, CNT-graphene films are demonstrated as effective electron field emitters with low turn-on and threshold electric fields of 2.9 and 3.3 V μm(-1), respectively. The development of CNT-graphene films with a wide range of tunable properties presented in this study shows promising applications in flexible opto-electronic, energy, and sensor devices.

  8. Emittance Reduction between EBIS LINAC and Booster by Electron Beam Cooling; Is Single Pass Cooling Possible?

    Energy Technology Data Exchange (ETDEWEB)

    Hershcovitch,A.

    2008-04-01

    Electron beam cooling is examined as an option to reduce momentum of gold ions exiting the EBIS LINAC before injection into the booster. Electron beam parameters are based on experimental data (obtained at BNL) of electron beams extracted from a plasma cathode. Preliminary calculations indicate that single pass cooling is feasible; momentum spread can be reduced by more than an order of magnitude in less than one meter.

  9. Uncertainties in electron-absorbed fractions and lung doses from inhaled beta-emitters.

    Science.gov (United States)

    Farfán, Eduardo B; Bolch, Wesley E; Huston, Thomas E; Rajon, Didier A; Huh, Chulhaeng; Bolch, W Emmett

    2005-01-01

    The computer code LUDUC (Lung Dose Uncertainty Code), developed at the University of Florida, was originally used to investigate the range of potential doses from the inhalation of either plutonium or uranium oxides. The code employs the ICRP Publication 66 Human Respiratory Tract model; however, rather than using simple point estimates for each of the model parameters associated with particle deposition, clearance, and lung-tissue dosimetry, probability density functions are ascribed to these parameters based upon detailed literature review. These distributions are subsequently sampled within LUDUC using Latin hypercube sampling techniques to generate multiple (e.g., approximately 1,000) sets of input vectors (i.e., trials), each yielding a unique estimate of lung dose. In the present study, the dosimetry component of the ICRP-66 model within LUDUC has been extended to explicitly consider variations in the beta particle absorbed fraction due to corresponding uncertainties and biological variabilities in both source and target tissue depths and thicknesses within the bronchi and bronchioles of the thoracic airways. Example dose distributions are given for the inhalation of absorption Type S compounds of 90Sr (Tmax = 546 keV) and 90Y (Tmax = 2,284 keV) as a function of particle size. Over the particle size range of 0.001 to 1 microm, estimates of total lung dose vary by a factor of 10 for 90Sr particles and by a factor of 4 to 10 for 90Y particles. As the particle size increases to 10 microm, dose uncertainties reach a factor of 100 for both radionuclides. In comparisons to identical exposures scenarios run by the LUDEP 2.0 code, Reference Man doses for inhaled beta-emitters were shown to provide slightly conservative estimates of lung dose compared to those in this study where uncertainties in lung airway histology are considered.

  10. Space-charge compensation measurements in electron cyclotron resonance ion source low energy beam transport lines with a retarding field analyzer

    Energy Technology Data Exchange (ETDEWEB)

    Winklehner, D.; Leitner, D., E-mail: leitnerd@nscl.msu.edu; Cole, D.; Machicoane, G.; Tobos, L. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824 (United States)

    2014-02-15

    In this paper we describe the first systematic measurement of beam neutralization (space charge compensation) in the ECR low energy transport line with a retarding field analyzer, which can be used to measure the potential of the beam. Expected trends for the space charge compensation levels such as increase with residual gas pressure, beam current, and beam density could be observed. However, the overall levels of neutralization are consistently low (<60%). The results and the processes involved for neutralizing ion beams are discussed for conditions typical for ECR injector beam lines. The results are compared to a simple theoretical beam plasma model as well as simulations.

  11. ET-22CONVECTION-ENHANCED DELIVERY OF THE AUGER-ELECTRON-EMITTER 125I-UdR: A HIGHLY EFFICIENT THERAPY IN AN ORTHOTOPIC GLIOBLASTOMA XENOGRAFT MODEL

    OpenAIRE

    Halle, Bo; Thisgaard, Helge; Aaberg-Jessen, Charlotte; Olsen, Birgitte; Dam, Johan; Langkjær, Niels; Munthe, Sune; Någren, Kjell; Høilund-Carlsen, Poul Flemming; Kristensen, Bjarne

    2014-01-01

    BACKGROUND: Glioblastomas (GBMs), the most common and malignant primary brain tumors, always recur after standard treatment. In order to develop more efficient therapies, we tested a novel therapeutic approach using the radioactive Auger-electron-emitter (AEE) [125I]5-Iodo-2'-deoxyuridine (125I-UdR). This drug incorporates into DNA of dividing cells and upon decay emission of Auger-electrons causes clusters of double strand breaks leading to cell death. METHODS: In vitro, cells from two GBM s...

  12. Real-time simulation of finite-frequency noise from a single-electron emitter

    Science.gov (United States)

    Jonckheere, T.; Stoll, T.; Rech, J.; Martin, T.

    2012-01-01

    We study the real-time emission of single electrons from a quantum dot coupled to a one dimensional conductor, using exact diagonalization on a discrete tight-binding chain. We show that, from the calculation of the time evolution of the one-electron states, we have simple access to all the relevant physical quantities in the system. In particular, we are able to compute accurately the finite-frequency current autocorrelation noise. The method that we use is general and versatile, allowing us to study the impact of many different parameters, such as the dot transparency or level position. Our results can be directly compared with existing experiments, and can also serve as a basis for future calculations including electronic interactions using the time-dependent density-matrix renormalization group and other techniques based on tight-binding models.

  13. Evidence for high-energy and low-emittance electron beams using ionization injection of charge in a plasma wakefield accelerator

    CERN Document Server

    Vafaei-Najafabadi, N; Clayton, C E; Joshi, C; Marsh, K A; Mori, W B; Welch, E C; Lu, W; Adli, E; Allen, J; Clarke, C I; Corde, S; Frederico, J; Gessner, S J; Green, S Z; Hogan, M J; Litos, M D; Yakimenko, V

    2015-01-01

    Ionization injection in a plasma wakefield accelerator was investigated experimentally using two lithium plasma sources of different lengths. The ionization of the helium gas, used to confine the lithium, injects electrons in the wake. After acceleration, these injected electrons were observed as a distinct group from the drive beam on the energy spectrometer. They typically have a charge of tens of pC, an energy spread of a few GeV, and a maximum energy of up to 30 GeV. The emittance of this group of electrons can be many times smaller than the initial emittance of the drive beam. The energy scaling for the trapped charge from one plasma length to the other is consistent with the blowout theory of the plasma wakefield.

  14. Numerical Analysis of the Measurement of Near-Beam Electron Cloud Density in Field-Free Region at KEK B-Factory Low-Energy Ring

    Science.gov (United States)

    Jain, Puneet; Fukuma, Hitoshi; Kanazawa, Ken-ichi; Suetsugu, Yusuke

    2010-11-01

    A large number of electrons in the so-called electron cloud are accumulated in beam chambers in positron storage rings. These electrons interact with the beam and can make the beam unstable. The density information of the electron cloud near the beam is therefore fundamental for studying beam instability and mitigation techniques related to the electron cloud. Recently, a method to measure the density of the electron cloud near the beam has been proposed by Kanazawa et al. The method enables the measurement of high-energy electrons selectively using a retarding field analyzer located on a chamber wall, noting that the electrons near the beam receive a strong kick by the beam. They calculated the density of the electron cloud simply assuming that the electrons that receive a kick are stationary. We examined the measurement technique in detail using a new computer code developed by us. The analysis showed that the volume near the beam occupied by the detected electrons, i.e., the observed volume, was strongly deformed owing to the horizontal velocity of the electrons; nevertheless this volume calculated assuming that the stationary electrons can still be used for calculating the density of the electron cloud in their measurement conditions.

  15. Dosimetry of Low-Energy Beta Radiation

    DEFF Research Database (Denmark)

    Borg, Jette

    Useful techniques and procedures for derermination of absorbed doses from exposure in a low-energy beta radiation were studied and evaluated. The four techniques included were beta spectrometry, extrapolation chamber dosimetry, Monte Carlo (MC) calculations, and exoelectron dosimetry. As a typical...... low-energy beta radiation field a moderated spectrum from a carbon-14 source was used. The measured responce of a Si(Li) detector to photons (bremsstrahlung) showed fine agreemant with the MC calculated photon response, whereas the difference between measured and MC calculated response to electrons...

  16. Dosimetry of Low-Energy Beta Radiation

    DEFF Research Database (Denmark)

    Borg, Jette

    Useful techniques and procedures for derermination of absorbed doses from exposure in a low-energy beta radiation were studied and evaluated. The four techniques included were beta spectrometry, extrapolation chamber dosimetry, Monte Carlo (MC) calculations, and exoelectron dosimetry. As a typical...... low-energy beta radiation field a moderated spectrum from a carbon-14 source was used. The measured responce of a Si(Li) detector to photons (bremsstrahlung) showed fine agreemant with the MC calculated photon response, whereas the difference between measured and MC calculated response to electrons...

  17. Development of ballistic hot electron emitter and its applications to parallel processing: active-matrix massive direct-write lithography in vacuum and thin films deposition in solutions

    Science.gov (United States)

    Koshida, N.; Kojima, A.; Ikegami, N.; Suda, R.; Yagi, M.; Shirakashi, J.; Yoshida, T.; Miyaguchi, H.; Muroyama, M.; Nishino, H.; Yoshida, S.; Sugata, M.; Totsu, K.; Esashi, M.

    2015-03-01

    Making the best use of the characteristic features in nanocrystalline Si (nc-Si) ballistic hot electron source, the alternative lithographic technology is presented based on the two approaches: physical excitation in vacuum and chemical reduction in solutions. The nc-Si cold cathode is a kind of metal-insulator-semiconductor (MIS) diode, composed of a thin metal film, an nc-Si layer, an n+-Si substrate, and an ohmic back contact. Under a biased condition, energetic electrons are uniformly and directionally emitted through the thin surface electrodes. In vacuum, this emitter is available for active-matrix drive massive parallel lithography. Arrayed 100×100 emitters (each size: 10×10 μm2, pitch: 100 μm) are fabricated on silicon substrate by conventional planar process, and then every emitter is bonded with integrated complementary metal-oxide-semiconductor (CMOS) driver using through-silicon-via (TSV) interconnect technology. Electron multi-beams emitted from selected devices are focused by a micro-electro-mechanical system (MEMS) condenser lens array and introduced into an accelerating system with a demagnification factor of 100. The electron accelerating voltage is 5 kV. The designed size of each beam landing on the target is 10×10 nm2 in square. Here we discuss the fabrication process of the emitter array with TSV holes, implementation of integrated ctive-matrix driver circuit, the bonding of these components, the construction of electron optics, and the overall operation in the exposure system including the correction of possible aberrations. The experimental results of this mask-less parallel pattern transfer are shown in terms of simple 1:1 projection and parallel lithography under an active-matrix drive scheme. Another application is the use of this emitter as an active electrode supplying highly reducing electrons into solutions. A very small amount of metal-salt solutions is dripped onto the nc-Si emitter surface, and the emitter is driven without

  18. Low energy beam transport system developments

    Energy Technology Data Exchange (ETDEWEB)

    Dudnikov, V., E-mail: vadim@muonsinc.com [Muons, Inc., Batavia, IL 60510 (United States); Han, B.; Stockli, M.; Welton, R. [ORNL, Oak Ridge, TN 37831 (United States); Dudnikova, G. [University of Maryland, College Park, MD 3261 (United States); Institute of Computational Technologies SBRAS, Novosibirsk (Russian Federation)

    2015-04-08

    For high brightness beam production it is important to preserve the brightness in the low energy beam transport system (LEBT) used to transport and match the ion beams to the next stage of acceleration, usually an RFQ. While electrostatic focusing can be problematic for high current beam transport, reliable electrostatic LEBT operation has been demonstrated with H{sup −} beams up to 60 mA. Now, however, it is commonly accepted that an optimal LEBT for high current accelerator applications consists of focusing solenoids with space charge compensation. Two-solenoid LEBTs are successfully used for high current (>100 mA) proton beam transport. Preservation of low emittances (~0.15 π mm-mrad) requires the addition of a heavy gas (Xe, Kr), which causes ~5% of proton loss in a 1 m long LEBT. Similar Xe densities would be required to preserve low emittances of H{sup −} beams, but such gas densities cause unacceptably high H{sup −} beam losses. A short LEBT with only one short solenoid, movable for RFQ matching, can be used for reduced negative ion stripping. A strong electrostatic-focusing LEBT has been successfully adopted for transport of high current H{sup −} beams in the SNS Front End. Some modifications of such electrostatic LEBTs are expected to improve the reliable transport of intense positive and negative ion beams without greatly degrading their low emittances. We concentrate on processes that determine the beam brightness degradation and on their prevention. Proposed improvements to the SNS electrostatic LEBT are discussed.

  19. Effect of temperature on the low-energy (≲1eV) electron attachment to perfluorocyclobutane ( c-C 4F 8)

    Science.gov (United States)

    Christodoulides, A. A.; Christophorou, L. G.; Mccorkle, D. L.

    1987-08-01

    A large decrease in the total electron attachment rate constant Kfor cC 4F 8 with increasing temperature T (300 to 560 K) has been observed for mean electron energies ≲ 0.8 eV, where the electron attachment is non-dissociative. Possible origins for the observed large negative effect of temperature on Ka() are discussed.

  20. Review of Emittance and Stability Monitoring Using Synchrotron Radiation Monitors

    CERN Document Server

    Holldack, K; Peatman, W B

    2001-01-01

    Different techniques of emittance and stability monitoring using bend magnet and undulator radiation will be reviewed. Besides imaging methods for emittance monitoring , the problem of XBPM's used for the measurement of the centre of mass position of the undulator beams will be treated in detail. The key feature of these monitors is a careful electron optical design to take account of gap dependent changes of the shape and photon energy of the undulator beam as well as spurious signals from dipoles and high heat load. The reason for the fact that these monitors work well on low energy machines like BESSY II but often fail due in high energy machines will be demonstrated by experimental results obtained on different types of BESSY II insertion devices such as undulators, wavelength shifters, multipole wigglers and electromagnetic undulators. Experimental results of global and local orbit monitoring and a proof of principle of a XBPM-based local feedback will be shown.

  1. Experimental Development of Low-emittance Field-emission Electron Sources

    Energy Technology Data Exchange (ETDEWEB)

    Lueangaranwong, A. [Northern Illinois Univ., DeKalb, IL (United States). Northern Illinois Center for Accelerator & Detector Development; Buzzard, C. [Northern Illinois Univ., DeKalb, IL (United States); Divan, R. [Argonne National Lab. (ANL), Argonne, IL (United States). Center for Nanoscale Materials; Korampally, V. [Northern Illinois Univ., DeKalb, IL (United States); Piot, P. [Northern Illinois Univ., DeKalb, IL (United States). Northern Illinois Center for Accelerator & Detector Development; Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)

    2016-10-10

    Field emission electron sources are capable of extreme brightness when excited by static or time-dependent electro- magnetic fields. We are currently developing a cathode test stand operating in DC mode with possibility to trigger the emission using ultra-short (~ 100-fs) laser pulses. This contribution describes the status of an experiment to investigate field-emission using cathodes under development at NIU in collaboration with the Argonne’s Center for Nanoscale Materials.

  2. Developing and using the field emitter as a high intensity electron source

    Science.gov (United States)

    Charbonnier, Francis

    1996-03-01

    In the 1940's, Erwin Müller dominated field emission research. The 50's and 60's saw considerable growth in the number of scientists interested in field emission. While many made important contributions, three persons stood out who had different talents and interests. First and foremost: Erwin Müller, a very innovative, creative and skilled inventor and experimentalist. Second: Robert Gomer, equally adept at theory and experiment, with a unique mastery of fundamental physics concepts. Third: Walter Dyke, who was intrigued by the unique properties of field emission and resolved to develop field emission cathodes as high performance electron sources for a variety of electron beam devices. This paper summarizes Dyke's work at Linfield College, Linfield Research Institute and Field Emission Corporation from 1948 to 1972. However, while Dyke established a solid foundation for useful field emission cathodes and investigated several devices, particularly in microwaves, electron optics and flash radiography, he was unable to complete his work and produce commercial devices, except for flash radiography. Many groups have pursued this work in recent years, sometimes with great success. This paper briefly summarizes current work on field emission cathodes and device applications, as this puts Dyke's work in better perspective and adds to its significance.

  3. SU-E-T-462: Impact of the Radiochromic Film Energy Response On Dose Measurements of Low Energy Electronic Brachytherapy Sources

    Energy Technology Data Exchange (ETDEWEB)

    Liang, L; Bekerat, H; Tomic, N; DeBlois, F; Devic, S [Jewish General Hospital, Medical Physics Unit, McGill University, Montreal, QC (Canada); Morcos, M [Vantage Oncology, Corona, CA (United States); Popovic, M; Watson, P; Seuntjens, J [Montreal General Hospital, Medical Physics Unit, McGill University, Montreal, QC (Canada)

    2015-06-15

    Purpose: We investigated the effect of the EBT3 GafChromicTM film model absorbed dose energy response when used for percent depth dose (PDD) measurements in low-energy photon beams. Methods: We measured PDDs in water from a Xoft 50 kVp source using EBT3 film, and compared them to PDD measurements acquired with a PTW-TN34013 parallel-plate ionization chamber. For the x-ray source, we simulated spectra using the EGSnrc (BEAMnrc) Monte Carlo code, and calculated Half Value Layer (HVL) at different distances from the source in water. Pieces of EBT3 film were irradiated in air and calibration curves were created in terms of air-kerma in air ((Kair)air) for different beam qualities. Pieces of EBT3 film were positioned at distances of 2–6 cm from the Xoft source in a water phantom using a custom-made holder, and irradiated at the same time. As scatter is incorporated in the measured film signal in water, measured (Kair)wat was subsequently converted into absorbed dose to water by the ratio of mass energy absorption coefficients following the AAPM TG-61 dosimetry protocol. Results: Our results show that film calibration curves obtained at beam qualities near the effective energy of the Xoft 50 kVp source in water lead to variation in absorbed dose energy dependence of the response of around 3%. However, if the calibration curve was established at MV beam quality, the error in absorbed dose could be as large as 15%. We observed agreement within 1% between PDD measurements using EBT3 film model (using a calibration curve obtained at 80 kVp, HVL=2.18 mm Al, Eeff=29.5 keV) and the parallel-plate ionization chamber. Conclusion: Accurate dose measurements using radiochromic films at low photon energies require that the radiochromic film dosimetry system be calibrated at corresponding low energies, as large absorbed dose errors are expected for calibrations performed at MV beam qualities.

  4. Emittance growth due to static and radiative space charge forces in an electron bunch compressor

    CERN Document Server

    Talman, Richard; Stulle, Frank

    2009-01-01

    Evolution of short intense electron bunches passing through bunch-compressing beam lines is studied using the UAL (Unified Accelerator Libraries) string space charge formulation [R. Talman, Phys. Rev. ST Accel. Beams 7, 100701 (2004); N. Malitsky and R. Talman, in Proceedings of the 9th European Particle Accelerator Conference, Lucerne, 2004 (EPS-AG, Lucerne, 2004); R. Talman, Accelerator X-Ray Sources (Wiley-VCH, Weinheim, 2006), Chap. 13]. Three major configurations are studied, with the first most important and studied in greatest detail (because actual experimental results are available and the same results have been simulated with other codes): (i) Experimental bunch compression results were obtained at CTF-II, the CERN test facility for the “Compact Linear Collider” using electrons of about 40 MeV. Previous simulations of these results have been performed (using trafic4* [A. Kabel et al., Nucl. Instrum. Methods Phys. Res., Sect. A 455, 185 (2000)] and elegant [M. Borland, Argonne National Laboratory...

  5. Ultra low energy results and their impact to dark matter and low energy neutrino physics

    CERN Document Server

    Bougamont, E; Derre, J; Giomataris, I; Gerbier, G; Gros, M; Magnier, P; Navick, X F; Salin, P; Savvidis, I; Tsiledakis, G; Vergados, J D

    2010-01-01

    We present ultra low energy results taken with the novel Spherical Proportional Counter. The energy threshold has been pushed down to about 25 eV and single electrons are clearly collected and detected. To reach such performance low energy calibration systems have been successfully developed: - A pulsed UV lamp extracting photoelectrons from the inner surface of the detector - Various radioactive sources allowing low energy peaks through fluorescence processes. The bench mark result is the observation of a well resolved peak at 270 eV due to carbon fluorescence which is unique performance for such large-massive detector. It opens a new window in dark matter and low energy neutrino search and may allow detection of neutrinos from a nuclear reactor or from supernova via neutrino-nucleus elastic scattering

  6. Degradation of Cu(In, Ga)Se{sub 2} thin-film solar cells due to the ionization effect of low-energy electrons

    Energy Technology Data Exchange (ETDEWEB)

    Kawakita, Shirou, E-mail: kawakita.shirou@jaxa.jp [Japan Aerospace Exploration Agency (JAXA), Tsukuba, Ibaraki 305-8505 (Japan); Imaizumi, Mitsuru [Japan Aerospace Exploration Agency (JAXA), Tsukuba, Ibaraki 305-8505 (Japan); Ishizuka, Shogo; Shibata, Hajime; Niki, Shigeru [National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568 (Japan); Okuda, Shuichi [Osaka Prefecture University (OPU), Sakai, Osaka 599-8570 (Japan); Kusawake, Hiroaki [Japan Aerospace Exploration Agency (JAXA), Tsukuba, Ibaraki 305-8505 (Japan)

    2015-05-01

    Cu (In, Ga)Se{sub 2} (CIGS) solar cells were irradiated with 100 keV electrons to reveal the characteristics of created radiation defects. 100 keV electrons cannot produce any displacement defects in CIGS. Low-fluence electrons improve the electrical performance of the CIGS solar cells due to the change in the conductive type of donor to acceptor in a metastable defect, which is equivalent to the light-soaking effect. However, high fluence electrons cause the cell performance to decline. From analysis based on changes in carrier density and electroluminescence, defects causing the decline in performance include donor- and non-radiative types. In addition, red-on-bias experiments showed an increase in III{sub Cu} defects due to electron irradiation. Based on these results, the degradation in the electrical performance of the CIGS solar cells irradiated with high electron fluence would be attributable to a change in the conductive type of III{sub Cu} defects. - Highlights: • Cu(In,Ga)Se2 Solar cells were irradiated with 100 and 250 keV electrons at low temperature. • These electrons degraded the electrical performance of Cu(In,Ga)Se2 sola cells. • The electrons induced ⅢCu defects in Cu(In,Ga)Se2.

  7. Measurements of L-shell X-ray production cross-sections of Ag and Sb by low-energy electron impact

    Science.gov (United States)

    Zhao, J. L.; An, Z.; Zhu, J. J.; Tan, W. J.; Liu, M. T.

    2016-05-01

    The total L-shell X-ray production cross-sections of Ag and Sb elements were measured by detecting the characteristic X-rays induced by the electron impact in the energy range of 6-28 keV. In this experiment, the thin films with thick aluminum substrates were used as the targets, and the experimental setup was improved. The influence of multiple scattering of electrons penetrating the targets films, electrons reflected from the thick aluminum substrates and bremsstrahlung photons produced when incident electrons impacted the targets were corrected by using the Monte Carlo method. The experimental results determined in this paper were compared with some theoretical models and other available experimental data in the literature. It was shown that the L-shell X-ray production cross-sections of Ag and Sb elements measured in this paper were in good agreement with the theoretical predictions within the uncertainties.

  8. Low Emittance Growth in a LEBT with Un-Neutralized Section

    Energy Technology Data Exchange (ETDEWEB)

    Prost, Lionel [Fermilab; Carneiro, Jean-Paul [Fermilab; Shemyakin, Alexander [Fermilab

    2016-06-01

    In a Low Energy Beam Transport line (LEBT), the emittance growth due to the beam's own space charge is typically suppressed by way of neutralization from either electrons or ions, which originate from ionization of the background gas. In cases where the beam is chopped, the neutralization pattern changes throughout the beginning of the pulse, causing the Twiss parameters to differ significantly from their steady state values, which, in turn, may result in beam losses downstream. For a modest beam perveance, there is an alternative solution, in which the beam is kept un-neutralized in the portion of the LEBT that contains the chopper. The emittance can be nearly preserved if the transition to the un-neutralized section occurs where the beam exhibits low transverse tails. This report discusses the experimental realization of such a scheme at Fermilab's PXIE, where low beam emittance dilution was demonstrated

  9. Investigations of L-shell x-ray production cross sections of In and Sn by low-energy electron impact

    Science.gov (United States)

    Zhao, J. L.; An, Z.; Zhu, J. J.; Tan, W. J.; Liu, M. T.

    2016-03-01

    Results from the measurements of absolute L-shell x-ray production cross sections of In (Z = 49) and Sn (Z = 50) by the impact of electrons with energies in the range of 6-28 keV are presented. The experimental setup has been improved and thin films with thick aluminum substrates were used as targets in the experiments. The effect of directional and energy spreads of the incident electron beam within the films and the characteristic x-ray enhancement due to backscattered electrons and bremsstrahlung photons generated from the substrates were corrected by means of Monte Carlo simulations. The experimental results of In and Sn elements by electron and positron impacts were compared with the DWBA and PWBA-C-Ex theories. It was shown that the L-shell x-ray production cross sections of In and Sn elements by electron impact measured in this paper were in good agreement with the theoretical predictions within the uncertainties and that the discrepancies existed between the experimental results by positron impact, available in the literature, and the theoretical values. The influence of the atomic relaxation parameters (fluorescence yields and Coster-Kronig coefficients) has also been discussed.

  10. Geant4 Low Energy Electromagnetic Physics

    Institute of Scientific and Technical Information of China (English)

    S.Chauvie; G.Depaola; 等

    2001-01-01

    Geant4 Low Energy Electromagnetic package Provides a precise treatment of electromagnetic interations of particles with matter down to very low energies (250 oV for electrons and photons,<1 keV for hadrons and ions),It includes a veriety of models for the electromagnetic processes of electrons,photons,hadrons and ions,taking into account advance features,such as shell effects and effects due to charge dependence.The comprehensive set of particle types it can handle,the variety of modeling approaches and the extended coverage of energy range make this package a unique tool among Monte Carlo codes on the market,and of relevance to serveral experimental domains in HIEP,astroparticle physics,space science and biomedical studies.

  11. Electron Beam Ion Sources

    OpenAIRE

    Zschornacka, G.; Schmidt, M.; Thorn, A.

    2014-01-01

    Electron beam ion sources (EBISs) are ion sources that work based on the principle of electron impact ionization, allowing the production of very highly charged ions. The ions produced can be extracted as a DC ion beam as well as ion pulses of different time structures. In comparison to most of the other known ion sources, EBISs feature ion beams with very good beam emittances and a low energy spread. Furthermore, EBISs are excellent sources of photons (X-rays, ultraviolet, extreme ultraviole...

  12. The role of electron-emitting radiopharmaceuticals in the palliative treatment of metastatic bone pain and for radiosynovectomy: applications of conversion electron emitter Tin-117m

    Directory of Open Access Journals (Sweden)

    Suresh C. Srivastava

    2007-09-01

    Full Text Available A variety of radionuclides continue to be investigated and/or clinically used for different therapeutic applications in nuclear medicine. The choice of a particular radionuclide with regard to appropriate emissions, linear energy transfer (LET, and physical half-life, etc., is dictated to a large extent by the character of the disease (e.g., solid tumor or metastatic disease, and by the carrier to selectively transport the radionuclide to the desired site. An impressive body of information has appeared in the recent literature that addresses many of these considerations. This article summarizes and discusses the role of high-LET electron emitters and their advantage in the treatment of cancer or for other disorders in specific situations. Areas such as bone pain palliation, bone malignancy therapy, and radiation synovectomy are covered in greater detail. Projections are made as to the future directions and progress in these areas. A discussion of the various issues related to the selection criteria that are useful for choosing the appropriate radionuclide for a particular application is included. Use of high-LET electron emitters is discussed in greater detail, with particular emphasis on the use of conversion electron emitter tin-117m for various therapeutic applications.Uma variedade de radionuclídeos continua a ser investigada e/ou clinicamente utilizada para diferentes aplicações terapêuticas em medicina nuclear. A escolha de um radionuclídeo, considerando-se sua emissão apropriada, transferência linear de energia (LET e meia-vida física é determinada na maior parte pelo caráter da doença (p.ex., tumor sólido ou doença metastática, e pelo carreador que transporta o radionuclídeo seletivamente para o sítio desejado. Um notável conjunto de informações voltadas para essas considerações tem aparecido na literatura recente. Esse trabalho resume e discute o papel de emissores de elétrons de alta-LET e sua vantagem no

  13. Theoretical studies on interactions between low energy electrons and protein-DNA fragments: valence anions of AT-amino acids side chain complexes.

    Science.gov (United States)

    Szyperska, Anna; Gajewicz, Agnieszka; Mazurkiewicz, Kamil; Leszczynski, Jerzy; Rak, Janusz

    2011-11-21

    Electron attachment to trimeric complexes that mimic most frequent hydrogen bonding interactions between an amino acid side chain (AASC) and the Watson-Crick (WC) 9-methyladenine-1-methylthymine (MAMT) base pair has been studied at the B3LYP/6-31++G(d,p) level of theory. Although the neutral trimers will not occur in the gas phase due to unfavorable free energy of stabilization (G(stab)) they should form a protein-DNA complex where entropy changes related to formation of such a complex will more than balance its disadvantageous G(stab). The most stable neutrals possess an identical pattern of hydrogen bonds (HBs). In addition, the proton-acceptor (N7) and proton-donor (N10) atoms of adenine involved in those HBs are located in the main groove of DNA. All neutral structures support the adiabatically stable valence anions in which the excess electron is localized on a π* orbital of thymine. The vertical detachment energies (VDEs) of anions corresponding to the most stable neutrals are substantially smaller than that of the isolated WC MAMT base pair. Hence, electron transfer from the anionic thymine to the phosphate group and as a consequence formation of a single strand break (SSB) should proceed more efficiently in a protein-dsDNA complex than in the naked dsDNA as far as electron attachment to thymine is concerned. This journal is © the Owner Societies 2011

  14. Growth and structure of thin platinum films deposited on Co(0001) studied by low-energy electron diffraction, X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy and scanning tunneling microscopy

    Science.gov (United States)

    Cabeza, G. F.; Légaré, P.; Sadki, A.; Castellani, N. J.

    2000-06-01

    The growth of platinum deposited on Co(0001) at room temperature in the range of submonolayer coverage is described. The evolution of very thin Pt films has been studied using low-energy electron diffraction (LEED), X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy and scanning tunneling microscopy (STM). The LEED patterns suggested a coherent epitaxial growth mode for Pt on Co(0001). Evidence for an island growth mode has been confirmed by STM together with step decoration. However, the second and third monolayers start growing before the completion of the first Pt layer. The electronic structure of the Pt deposits exhibited original properties with low Fermi level density of states and valence-band broadening. This is in agreement with theoretical calculations presented in this work.

  15. Identification and measurement of low energy electrons and the decay $B_{s}^{0} \\to J/\\psi \\phi$ at CMS

    CERN Document Server

    Presland, A

    2001-01-01

    The Compact Muon Solenoid (CMS) is a general purpose detector that will take advantage of the rich physics potential of the Large Hadron Collider (LHC) at the European Centre for Particle Physics (CERN). LHC will provide a copious source of b-quarks and enables a comprehensive b-physics programme. An important aspect of this programme is the ability to reconstruct J/psi resonances from their decay to electrons. This will require measurement of electrons with energies of a few GeV and will be achieved by exploiting the precision electromagnetic calorimetry provided by the CMS lead tungstate crystal calorimeter (ECAL). This thesis examines the performance of a CMS Endcap ECAL prototype calorimeter using beams of high energy (5 GeV to 180 GeV) electrons. A parameterisation of the energy resolution is presented that allows stochastic and constant contributions to be obtained. These are found to have values that meet the design specification. The contribution to the energy resolution that arises from the performan...

  16. Low energy beam transport for HIDIF

    Science.gov (United States)

    Meusel, O.; Pozimski, J.; Jakob, A.; Lakatos, A.

    2001-05-01

    Low energy beam transport (LEBT) for a heavy ion inertial fusion (HIDIF, I. Hofmann and G. Plass, Report of the European Study Group on Heavy Ion Driven Inertial Fusion for the Period 1995-1998) facility suffers from high space charge forces and high ion mass. Space charge compensation reduces the necessary focusing force of the lenses and the radius of the beam in the LEBT, and therefrom the emittance growth due to aberrations and self fields is reduced. Gabor lenses (D. Gabor, Nature 160 (1947)) providing a stable space charge cloud for focusing and combine strong cylinder symmetric focusing with partly space charge compensation and low emittance growth. A high tolerance against source noise and current fluctuations and reduced investment costs could be other possible advantages. The proof of principle has already been demonstrated (J.A. Palkovic, Measurements on a Gabor lens for Neutralizing and Focusing a 30 keV Proton beam, University of Wisconsin, Madison, 1989; J. Pozimski, P. Groß, R. Dölling and T. Weis, First experimental studies of a Gabor plasma-lens in Frankfurt, Proceedings of the 3rd EPAC Conference, Berlin, 1992). To broaden the experiences and to investigate the realisation of a LEBT concept for the HIDIF injector an experimental program using two Gabor lenses for independent variation of beam radius and envelope angel at RFQ injection was started. Therefrom the first experimental results using a double Gabor lens (DGPL) LEBT system for transporting an high perveance Xe + beam are presented and the results of numerical simulations are shown.

  17. Low energy beam transport for HIDIF

    Energy Technology Data Exchange (ETDEWEB)

    Meusel, O. E-mail: o.meusel@iap.uni-frankfurt.de; Pozimski, J.; Jakob, A.; Lakatos, A

    2001-05-21

    Low energy beam transport (LEBT) for a heavy ion inertial fusion (HIDIF, I. Hofmann and G. Plass, Report of the European Study Group on Heavy Ion Driven Inertial Fusion for the Period 1995-1998) facility suffers from high space charge forces and high ion mass. Space charge compensation reduces the necessary focusing force of the lenses and the radius of the beam in the LEBT, and therefrom the emittance growth due to aberrations and self fields is reduced. Gabor lenses (D. Gabor, Nature 160 (1947)) providing a stable space charge cloud for focusing and combine strong cylinder symmetric focusing with partly space charge compensation and low emittance growth. A high tolerance against source noise and current fluctuations and reduced investment costs could be other possible advantages. The proof of principle has already been demonstrated (J.A. Palkovic, Measurements on a Gabor lens for Neutralizing and Focusing a 30 keV Proton beam, University of Wisconsin, Madison, 1989; J. Pozimski, P. Gross, R. Doelling and T. Weis, First experimental studies of a Gabor plasma-lens in Frankfurt, Proceedings of the 3rd EPAC Conference, Berlin, 1992). To broaden the experiences and to investigate the realisation of a LEBT concept for the HIDIF injector an experimental program using two Gabor lenses for independent variation of beam radius and envelope angel at RFQ injection was started. Therefrom the first experimental results using a double Gabor lens (DGPL) LEBT system for transporting an high perveance Xe{sup +} beam are presented and the results of numerical simulations are shown.

  18. The irradiation of pure CH3OH and 1:1 mixture of NH3:CH3OH ices at 30 K using low energy electrons

    Science.gov (United States)

    Jheeta, Sohan; Domaracka, A.; Ptasinska, S.; Sivaraman, B.; Mason, N. J.

    2013-01-01

    The results of an experimental investigation of 1 keV electron irradiation of ices (deposited at 30 K) of (i) pure methanol and (ii) of a 1:1 mixture of NH3:CH3OH are reported. Molecular products formed within the ice were detected and monitored using FTIR spectroscopy. The products observed were methyl formate (H3COHCO), methane (CH4), hydroxymethyl (CH2OH), formamide (HCONH2), formic acid (HCOOH), formaldehyde (H2CO), formyl radical (HCO), cyanate ion (OCN-), isocyanic acid (HNCO), carbon monoxide (CO) and carbon dioxide (CO2). The consequences of these results for prebiotic chemistry in the interstellar medium and star forming regions are discussed.

  19. Iron-centered ten-vertex germanium clusters: the ubiquity of low energy pentagonal prismatic structures with various skeletal electron counts.

    Science.gov (United States)

    Uţă, M M; Cioloboc, D; King, R B

    2012-09-13

    One of the most significant recent developments (in 2009) is the discovery of the clusters M@Ge10(3-) (M = Fe, Co) in which the outer Ge10 polyhedron is a pentagonal prism rather than a deltahedral structure of the type predicted by the Wade-Mingos rules. Consistent with this experimental observation, density functional theory shows the lowest energy structures to be pentagonal prisms for the iron-centered clusters Fe@Ge10(z) in all nine charge states ranging from -5 to +3. This contrasts with the previously studied cobalt-centered germanium clusters Co@Ge10(z) for which the lowest energy structures are pentagonal prisms only for the electron richest systems where z ranges from -3 to -5. The C3v structures derived from the tetracapped trigonal prism found as lowest energy structures of the electron poorer Co@Ge10(z) (z = 0, -1, -2) systems are higher energy structures for the iron-centered germanium clusters Fe@Ge10(z) (z = 0, -1, -2). The strong energetic preference for pentagonal prismatic structures in the Fe@Ge10(z) clusters can be attributed to the need for the larger volume of the pentagonal prism relative to other 10-vertex closed polyhedra to accommodate the interstitial iron atom.

  20. Standard Test Method for Application of Ionization Chambers to Assess the Low Energy Gamma Component of Cobalt-60 Irradiators Used in Radiation-Hardness Testing of Silicon Electronic Devices

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2010-01-01

    1.1 Low energy components in the photon energy spectrum of Co-60 irradiators lead to absorbed dose enhancement effects in the radiation-hardness testing of silicon electronic devices. These low energy components may lead to errors in determining the absorbed dose in a specific device under test. This method covers procedures for the use of a specialized ionization chamber to determine a figure of merit for the relative importance of such effects. It also gives the design and instructions for assembling this chamber. 1.2 This method is applicable to measurements in Co-60 radiation fields where the range of exposure rates is 7 × 10 −6 to 3 × 10−2 C kg −1 s−1 (approximately 100 R/h to 100 R/s). For guidance in applying this method to radiation fields where the exposure rate is >100 R/s, see Appendix X1. Note 1—See Terminology E170 for definition of exposure and its units. 1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information onl...

  1. Stopping power and mean free path for low-energy electrons in ten scintillators over energy range of 20-20,000 eV.

    Science.gov (United States)

    Tan, Zhenyu; Xia, Yueyuan

    2012-01-01

    Systematic calculations of the stopping powers (SP) and inelastic mean free paths (IMFP) for 20-20,000eV electrons in a group of 10 important scintillators have been carried out. The calculations are based on the dielectric model including the Born-Ochkur exchange correction and the optical energy loss functions (OELFs) are empirically evaluated because of the lack of available experimental optical data for the scintillators under consideration. The evaluated OELFs are examined by both the f-sum rule and the calculation of mean ionization potential. The SP and IMFP data presented here are the first results for the 10 scintillators over the energy range of 20-20,000eV, and are of key importance for the investigation of liquid scintillation counting.

  2. Quantum scattering at low energies

    DEFF Research Database (Denmark)

    Derezinski, Jan; Skibsted, Erik

    2009-01-01

    For a class of negative slowly decaying potentials, including V(x):=−γ|x|−μ with 0low-energy regime. Using appropriate modifiers of the Isozaki–Kitada type we show that scattering theory is well behaved on the whole continuous spectrum...

  3. Quantum scattering at low energies

    DEFF Research Database (Denmark)

    Derezinski, Jan; Skibsted, Erik

    For a class of negative slowly decaying potentials, including with , we study the quantum mechanical scattering theory in the low-energy regime. Using modifiers of the Isozaki--Kitada type we show that scattering theory is well behaved on the {\\it whole} continuous spectrum of the Hamiltonian...

  4. Effect of hydrogenation, low energy ion irradiation and annealing on hydrogen bonding to polycrystalline diamond surface studied by high resolution electron energy loss spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Michaelson, S.; Ternyak, O.; Akhvlediani, R.; Hoffman, A. [Schulich Faculty of Chemistry, Technion, Israeli Institute of Technology, Haifa (Israel); Lafosse, A.; Bertin, M.; Azria, R. [Paris-Sud Univ. et CNRS, Lab. des Collisions Atomiques et Moleculaires, 91 - Orsay (France)

    2007-09-15

    The effects of different processes of hydrogenation, thermal treatment and ion irradiation of hydrogenated polycrystalline diamond surface have been investigated by means of high resolution electron energy loss spectroscopy (HR-EELS). Analysis of the different contributions in the CH stretching, overtones and combination modes, as well as changes in relative intensities of the diamond CC and CH{sub x} related vibrations allowed us to identify the CH{sub x} adsorbed species on the diamond surface following the different treatments. Ex-situ hydrogenation of diamond surface by means of exposure to H-MW plasma results in a fully hydrogenated well-ordered diamond surface and etching of the amorphous phase located on the grain boundaries present on the sample after CVD-deposition. Annealing this surface to 600 C results in some subtle changes in the HR-EELS, probably associated with decomposition of CH{sub x} (x=2,3) adsorbed species. Ion irradiation on the surface induces partial desorption of hydrogen from the diamond phase and a large amount of amorphous defects, some of them of sp and the most of them of sp{sup 2} character. Annealing to 600-700 C of the irradiated surface leads to hydrogen desorption. In-situ hydrogenation of the irradiated and annealed sample does not restore the diamond structure, and results in hydrogenated amorphous surface, unstable with thermal annealing above 600-700 C. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. The Silicon photomultiplier as a metasystem with designed electronics as metadevice for a new receiver-emitter in visible light communications

    CERN Document Server

    Gutierrez, R M; Castaneda, L F; Castano, J F

    2015-01-01

    A Silicon Photomultiplier, SiPM, is a metasystem of Avalanche Photodiodes, APDs, which embedded in a specific purpose electronic, becomes a metadevice with unique and useful advanced functionalities to capture, transmit and analyze information with increased efficiency and security. The SiPM is a very small state of the art photo-detector with very high efficiency and sensitivity, with good response to controlled light pulses in the presence of background light without saturation. New results profit of such metadevice to propose a new receiver-emitter system useful for Visible Light Communication, VLC.

  6. Surface structure determination of group 11 metals adsorbed on a rhenium(10 anti 10) surface by low-energy electron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Messahel, Lyria

    2012-11-12

    This thesis deals with the computational surface determination of various long-range ordered phases formed by thin films of copper, silver, and gold adsorbed on the rhenium- (10 anti 10) surface. It is based upon LEED-I,V curves for these phases that were recorded in the course of detailed experimental investigations of the respective films carried out in our group (using techniques such as LEED, MEED, and TPD). In order to solve the intricate puzzle of surface structural analysis, the electron elastic scattering behaviour of the investigated coinage metal phases was calculated using the Erlangen TensErLEED program package. Thereby first a set of theoretical LEED-I,V curves is derived for a guessed reference structure. Subsequently its structural input parameters are varied in a trial-and-error procedure until optimal agreement between experiment and theory is attained. The (1 x 1) phases formed by the deposited metals were tackled first to establish an absolute coverage calibration and to elucidate the respective growth modes on the Re(10 anti 10) surface. In all three cases the (1 x 1) structure is developed best at a coverage {Theta}{sub Cu,Ag,Au}=2 ML=1 BL. Extension of the investigation to experimental I,V curves for higher Cu coverages revealed that this element continues to grow bilayerwise, thereby retaining the Re hcp morphology. Ag, in contrast to Cu and Au, happens not to grow as homogeneously, and the TPD data suggest that Ag films exhibit the so-called simultaneous-multilayer (SM) growth mode. The following analysis of the sub-bilayer coverage range shows that the three systems exhibit considerable differences. While Cu, having a negative lattice misfit compared to Re, shows no long-range ordered superstructures, Ag and Au with a similar positive misfit form a couple of such phases. Ag features both a (1 x 4) phase, stable at ambient temperatures, that upon heating transforms into a c(2 x 2) phase that only exists at elevated temperatures. The

  7. Field electron emission from LaB{sub 6} and TiN emitter arrays fabricated by transfer mold technique

    Energy Technology Data Exchange (ETDEWEB)

    Nakamoto, Masayuki; Fukuda, Katsuyoshi

    2002-12-30

    LaB{sub 6} and TiN field emitter arrays (FEAs) have been developed by the transfer mold technique to fabricate sharp, uniform, and low operation voltage FEAs using low work function materials. Because of the sharpening effect on the tips by thermally oxidized SiO{sub 2} layer of the molds, emitter tip radii are as small as less than 10 nm. The turn-on voltages of LaB{sub 6} and TiN FEA are 110-130 V lower than that of conventional Mo FEA by decreasing the surface barrier heights for field emission, having the same emitter shape. That of the gated LaB{sub 6} FEA is as low as 28 V even without high vacuum baking treatment. Transfer mold technique provides easiness of selecting low work function materials as well as superior uniform sharpness of FEAs. Transfer mold LaB{sub 6} and TiN FEAs are useful for low operation vacuum microelectronic devices.

  8. The low energy signaling network

    Directory of Open Access Journals (Sweden)

    Filipa dos Santos Tomé

    2014-07-01

    Full Text Available Stress impacts negatively on plant growth and crop productivity, causing extensive losses to agricultural production worldwide. Throughout their life, plants are often confronted with multiple types of stress that affect overall cellular energy status and activate energy saving responses. The resulting low energy syndrome (LES includes transcriptional, translational, and metabolic reprogramming and is essential for stress adaptation. The conserved kinases SnRK1 and TOR play central roles in the regulation of LES in response to stress conditions, affecting cellular processes and leading to growth arrest and metabolic reprogramming. We review the current understanding of how TOR and SnRK1 are involved in regulating the response of plants to low energy conditions. The central role in the regulation of cellular processes, the reprogramming of metabolism, and the phenotypic consequences of these two kinases will be discussed in light of current knowledge and potential future developments.

  9. Linac4 low energy beam measurements with negative hydrogen ions.

    Science.gov (United States)

    Scrivens, R; Bellodi, G; Crettiez, O; Dimov, V; Gerard, D; Granemann Souza, E; Guida, R; Hansen, J; Lallement, J-B; Lettry, J; Lombardi, A; Midttun, Ø; Pasquino, C; Raich, U; Riffaud, B; Roncarolo, F; Valerio-Lizarraga, C A; Wallner, J; Yarmohammadi Satri, M; Zickler, T

    2014-02-01

    Linac4, a 160 MeV normal-conducting H(-) linear accelerator, is the first step in the upgrade of the beam intensity available from the LHC proton injectors at CERN. The Linac4 Low Energy Beam Transport (LEBT) line from the pulsed 2 MHz RF driven ion source, to the 352 MHz RFQ (Radiofrequency Quadrupole) has been built and installed at a test stand, and has been used to transport and match to the RFQ a pulsed 14 mA H(-) beam at 45 keV. A temporary slit-and-grid emittance measurement system has been put in place to characterize the beam delivered to the RFQ. In this paper a description of the LEBT and its beam diagnostics is given, and the results of beam emittance measurements and beam transmission measurements through the RFQ are compared with the expectation from simulations.

  10. Linac4 Low Energy Beam Measurements with Negative Hydrogen

    CERN Document Server

    Scrivens, R; Crettiez, O; Dimov, V; Gerard, D; Granemann Souza, E; Guida, R; Hansen, J; Lallement, J B; Lettry, J; Lombardi, A; Midttun, O; Pasquino, C; Raich, U; Riffaud, B; Roncarolo, F; Valerio-Lizarraga, C A; Wallner, J; Yarmohammadi Satri, M; Zickler, T

    2014-01-01

    Linac4, a 160 MeV normal-conducting H- linear accelerator, is the first step in the upgrade of the beam intensity available from the LHC proton injectors at CERN. The Linac4 Low Energy Beam Transport (LEBT) line from the pulsed 2 MHz RF driven ion source, to the 352 MHz RFQ has been built and installed at a test stand, and has been used to transport and match to the RFQ a pulsed 14 mA H- beam at 45 keV. A temporary slit-and-grid emittance measurement system has been put in place to characterize the beam delivered to the RFQ. In this paper a description of the LEBT and its beam diagnostics is given, and the results of beam emittance measurements and beam transmission measurements through the RFQ are compared with the expectation from simulations.

  11. Linac4 low energy beam measurements with negative hydrogen ions

    Energy Technology Data Exchange (ETDEWEB)

    Scrivens, R., E-mail: richard.scrivens@cern.ch; Bellodi, G.; Crettiez, O.; Dimov, V.; Gerard, D.; Granemann Souza, E.; Guida, R.; Hansen, J.; Lallement, J.-B.; Lettry, J.; Lombardi, A.; Midttun, Ø.; Pasquino, C.; Raich, U.; Riffaud, B.; Roncarolo, F.; Valerio-Lizarraga, C. A.; Wallner, J.; Yarmohammadi Satri, M.; Zickler, T. [CERN, 1211 Geneva 23 (Switzerland)

    2014-02-15

    Linac4, a 160 MeV normal-conducting H{sup −} linear accelerator, is the first step in the upgrade of the beam intensity available from the LHC proton injectors at CERN. The Linac4 Low Energy Beam Transport (LEBT) line from the pulsed 2 MHz RF driven ion source, to the 352 MHz RFQ (Radiofrequency Quadrupole) has been built and installed at a test stand, and has been used to transport and match to the RFQ a pulsed 14 mA H{sup −} beam at 45 keV. A temporary slit-and-grid emittance measurement system has been put in place to characterize the beam delivered to the RFQ. In this paper a description of the LEBT and its beam diagnostics is given, and the results of beam emittance measurements and beam transmission measurements through the RFQ are compared with the expectation from simulations.

  12. Emittance investigation of RF photo-injector

    CERN Document Server

    Yang Mao Rong; Li Zheng; Li Ming; Xu Zhou

    2002-01-01

    A high-power laser beam illuminates a photocathode surface placed on an end wall of an RF cavity. The emitted electrons are accelerated immediately to a relativistic energy by the strong RF find in the cavity. But space charge effect induces beam emittance growth especially near the cathode where the electrons are still nonrelativistic. The author analyzes the factors which lead the transverse emittance growth and method how to resolve this problem. After introducing solenoidal focusing near the photocathode, the beam emittance growth is suppressed dramatically. The beam emittance is given also after compensation and simulation results. The measurements show these results are coincident

  13. Brownian Emitters

    Science.gov (United States)

    Tsekov, Roumen

    2016-06-01

    A Brownian harmonic oscillator, which dissipates energy either by friction or via emission of electromagnetic radiation, is considered. This Brownian emitter is driven by the surrounding thermo-quantum fluctuations, which are theoretically described by the fluctuation-dissipation theorem. It is shown how the Abraham-Lorentz force leads to dependence of the half-width on the peak frequency of the oscillator amplitude spectral density. It is found that for the case of a charged particle moving in vacuum at zero temperature, its root-mean-square velocity fluctuation is a universal constant, equal to roughly 1/18 of the speed of light. The relevant Fokker-Planck and Smoluchowski equations are also derived.

  14. State selective electron capture at low energies

    NARCIS (Netherlands)

    Bliek, Frederik Willem

    1997-01-01

    Zolang de mensheid al bestaat, vraagt men zich af hoe de sterren zijn ontstaan die we tijdens een heldere nacht aan de hemel zien staan. Om een antwoord te kunnen geven op deze vraag moeten we ons eerst afvragen hoe we iets kunnen leren over een ster die vaak vele duizenden lichtjaren van ons verwij

  15. State selective electron capture at low energies

    NARCIS (Netherlands)

    Bliek, Frederik Willem

    1997-01-01

    Zolang de mensheid al bestaat, vraagt men zich af hoe de sterren zijn ontstaan die we tijdens een heldere nacht aan de hemel zien staan. Om een antwoord te kunnen geven op deze vraag moeten we ons eerst afvragen hoe we iets kunnen leren over een ster die vaak vele duizenden lichtjaren van ons verwij

  16. Space charge compensation in low energy proton beams

    CERN Document Server

    Ismail, A B; Uriot, D; Pichoff, N

    2004-01-01

    High power accelerators are being studied for several projects including accelerator driven neutron or neutrino sources. The low energy part of these facilities has to be carefully optimized to match the beam requirements of the higher energy parts. In this low energy part, the space charge self force, induced by a high intensity beam, has to be carefully managed. This nonlinear force can generate a high irreversible emittance growth of the beam. To reduce space charge effects, neutralization of the beam charge can be done by capturing some particles of the ionised residual gas in the vacuum chamber. This space charge compensation (SCC) regime complicates the dynamic study. Modelling the beam behaviour in such regime would be a significant contribution to the development of high intensity accelerators. Numerical and experimental study of SCC is in progress on the Saclay High Intensity Proton Injector. Experimental measurements and 2D/3D simulations of proton beam SCC will be presented.

  17. Low-energy neutrino measurements

    Indian Academy of Sciences (India)

    Davide D'angelo

    2012-10-01

    Low-energy solar neutrino detection plays a fundamental role in understanding both solar astrophysics and particle physics. After introducing the open questions on both fields, we review here the major results of the last two years and expectations for the near future from Borexino, Super-Kamiokande, SNO and KamLAND experiments as well as from upcoming (SNO+) and planned (LENA) experiments. Scintillator neutrino detectors are also powerful antineutrino detectors which can detect neutrinos emitted by the Earth crust and mantle. First measurements of geoneutrinos have occurred which can bring fundamental contribution in understanding the geophysics of the planet.

  18. Low-energy mechanical ventilation

    DEFF Research Database (Denmark)

    Andersen, Claus Wessel; Hviid, Christian Anker

    2014-01-01

    and with as little energy consumption as 41.1 kWh/m2/year including heating and all building services with no use of renewable energy such as PVcells or solar heating. One of the key means of reaching the objectives was to implement mechanical ventilation with low pressure loss and therefore low energy consumption....... The project consists of two buildings, building one is 6 stories high, and building two is 4 stories high. The buildings have a gross area of 50,500 m2 including underground parking. The ventilation and indoor climate concept was to use mechanical ventilation together with mechanical cooling and fanassisted...

  19. Dosimetry of low-energy beta radiation

    Energy Technology Data Exchange (ETDEWEB)

    Borg, J.

    1996-08-01

    Useful techniques and procedures for determination of absorbed doses from exposure in a low-energy {beta} radiation field were studied and evaluated in this project. The four different techniques included were {beta} spectrometry, extrapolation chamber dosimetry, Monte Carlo (MC) calculations, and exoelectron dosimetry. As a typical low-energy {beta} radiation field a moderated spectrum from a {sup 14}C source (E{sub {beta}},{sub max} =156 keV) was chosen for the study. The measured response of a Si(Li) detector to photons (bremsstrahlung) showed fine agreement with the MC calculated photon response, whereas the difference between measured and MC calculated responses to electrons indicates an additional dead layer thickness of about 12 {mu}m in the Si(Li) detector. The depth-dose profiles measured with extrapolation chambers at two laboratories agreed very well, and it was confirmed that the fitting procedure previously reported for {sup 147}Pm depth-dose profiles is also suitable for {beta} radiation from {sup 14}C. An increasing difference between measured and MC calculated dose rates for increasing absorber thickness was found, which is explained by limitations of the EGS4 code for transport of very low-energy electrons (below 10-20 keV). Finally a study of the thermally stimulated exoelectron emission (TSEE) response of BeO thin film dosemeters to {beta} radiation for radiation fields with maximum {beta} energies ranging from 67 keV to 2.27 MeV is reported. For maximum {beta} energies below approximately 500 keV, a decrease in the response amounting to about 20% was observed. It is thus concluded that a {beta} dose higher than about 10 {mu}Gy can be measured with these dosemeters to within 0 to -20% independently of the {beta}energy for E{sub {beta}},{sub max} values down to 67 keV. (au) 12 tabs., 38 ills., 71 refs.

  20. Low energy gauge unification theory

    CERN Document Server

    Li Tian Jun

    2002-01-01

    Because of the problems arising from the fermion unification in the traditional Grand Unified Theory and the mass hierarchy between the 4-dimensional Planck scale and weak scale, we suggest the low energy gauge unification theory with low high-dimensional Planck scale. We discuss the non-supersymmetric SU(5) model on M sup 4 xS sup 1 /Z sub 2 xS sup 1 /Z sub 2 and the supersymmetric SU(5) model on M sup 4 xS sup 1 /(Z sub 2 xZ sub 2 ')xS sup 1 /(Z sub 2 xZ sub 2 ')xS sup 1 /(Z sub 2 xZ sub 2 '). The SU(5) gauge symmetry is broken by the orbifold projection for the zero modes, and the gauge unification is accelerated due to the SU(5) asymmetric light KK states. In our models, we forbid the proton decay, still keep the charge quantization, and automatically solve the fermion mass problem. We also comment on the anomaly cancellation and other possible scenarios for low energy gauge unification.