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Sample records for radiation electronic structure

  1. Electromagnetic Radiation of Electrons in Periodic Structures

    Potylitsyn, Alexander Petrovich

    2011-01-01

    Periodic magnetic structures (undulators) are widely used in accelerators to generate monochromatic undulator radiation (UR) in the range from far infrared to the hard X-ray region. Another periodic crystalline structure is used to produce quasimonochromatic polarized photon beams via the coherent bremsstrahlung mechanism (CBS). Due to such characteristics as monochromaticity, polarization and adjustability, these types of radiation is of large interest for applied and basic research of accelerator-emitted radiation. The book provides a detailed overview of the fundamental principles behind electromagnetic radiation emitted from accelerated charged particles (e.g. UR, CBS, radiation of fast electrons in Laser flash fields) as well as a unified description of relatively new radiation mechanisms which attracted great interest in recent years. This are the so-called polarization radiation excited by the Coulomb field of incident particles in periodic structures, parametric X-rays, resonant transition radiation a...

  2. Electromagnetic radiation of electrons in periodic structures

    Potylitsyn, Alexander Petrovich

    2011-01-01

    Periodic magnetic structures (undulators) are widely used in accelerators to generate monochromatic undulator radiation (UR) in the range from far infrared to the hard X-ray region. Another periodic crystalline structure is used to produce quasimonochromatic polarized photon beams via the coherent bremsstrahlung mechanism (CBS). Due to such characteristics as monochromaticity, polarization and adjustability, these types of radiation is of large interest for applied and basic research of accelerator-emitted radiation. The book provides a detailed overview of the fundamental principles behind electromagnetic radiation emitted from accelerated charged particles (e.g. UR, CBS, radiation of fast electrons in Laser flash fields) as well as a unified description of relatively new radiation mechanisms which attracted great interest in recent years. This are the so-called polarization radiation excited by the Coulomb field of incident particles in periodic structures, parametric X-rays, resonant transition radiation and the Smith-Purcell effect. Characteristics of such radiation sources and perspectives of their usage are discussed. The recent experimental results as well as their interpretation are presented. (orig.)

  3. Relationship between chromatin structure and sensitivity to molecularly targeted auger electron radiation therapy.

    Terry, S.Y.A.; Vallis, K.A.

    2012-01-01

    PURPOSE: The open structure of euchromatin renders it susceptible to DNA damage by ionizing radiation (IR) compared with compact heterochromatin. The effect of chromatin configuration on the efficacy of Auger electron radiotherapy was investigated. METHODS AND MATERIALS: Chromatin structure was

  4. Peculiarities of electronic structure of silicon-on-insulator structures and their interaction with synchrotron radiation

    Vladimir A. Terekhov

    2015-09-01

    Full Text Available SOI (silicon-on-insulator structures with strained and unstrained silicon layers were studied by ultrasoft X-ray emission spectroscopy and X-ray absorption near edge structure spectroscopy with the use of synchrotron radiation techniques. Analysis of X-ray data has shown a noticeable transformation of the electron energy spectrum and local partial density of states distribution in valence and conduction bands in the strained silicon layer of the SOI structure. USXES Si L2,3 spectra analysis revealed a decrease of the distance between the L2v′ и L1v points in the valence band of the strained silicon layer as well as a shift of the first two maxima of the XANES first derivation spectra to the higher energies with respect to conduction band bottom Ec. At the same time the X-ray standing waves of synchrotron radiation (λ~12–20 nm are formed in the silicon-on-insulator structure with and without strains of the silicon layer. Moreover changing the synchrotron radiation grazing angle θ by 2° leads to a change of the electromagnetic field phase to the opposite.

  5. Investigating the interaction of x-ray free electron laser radiation with grating structure

    Gaudin, J.; Ozkan, C.; Chalupsky, J.; Bajt, S.; Burian, T.; Vysin, L.; Coppola, N.; Farahani, S. D.; Chapman, H. N.; Galasso, G.; Hajkova, V.; Harmand, M.; Juha, L.; Jurek, M.; Loch, R. A.; Möller, S.; Nagasono, M.; Stormer, M.; Sinn, H.; Saksl, K.; Sobierajski, R.; Schulz, J.; Sovak, P.; Toleikis, S.; Tiedtke, K.; Tschentscher, T.; Krzywinski, J.

    2012-01-01

    The interaction of free electron laser pulses with grating structure is investigated using 4.6 +/- 0.1 nm radiation at the FLASH facility in Hamburg. For fluences above 63.7 +/- 8.7 mJ/cm(2), the interaction triggers a damage process starting at the edge of the grating structure as evidenced by

  6. Electron transport in nanometer GaAs structure under radiation exposure

    Demarina, N V

    2002-01-01

    One investigates into effect of neutron and proton irradiation on electron transport in nanometer GaAs structures. Mathematical model takes account of radiation defects via introduction of additional mechanisms od scattering of carriers at point defects and disordered regions. To investigate experimentally into volt-ampere and volt-farad characteristics one used a structure based on a field-effect transistor with the Schottky gate and a built-in channel. Calculation results of electron mobility, drift rate of electrons, time of energy relaxation and electron pulse are compared with the experimental data

  7. Radiative Recombination and Photoionization Data for Tungsten Ions. Electron Structure of Ions in Plasmas

    Malvina B. Trzhaskovskaya

    2015-05-01

    Full Text Available Theoretical studies of tungsten ions in plasmas are presented. New calculations of the radiative recombination and photoionization cross-sections, as well as radiative recombination and radiated power loss rate coefficients have been performed for 54 tungsten ions for the range W6+–W71+. The data are of importance for fusion investigations at the reactor ITER, as well as devices ASDEX Upgrade and EBIT. Calculations are fully relativistic. Electron wave functions are found by the Dirac–Fock method with proper consideration of the electron exchange. All significant multipoles of the radiative field are taken into account. The radiative recombination rates and the radiated power loss rates are determined provided the continuum electron velocity is described by the relativistic Maxwell–Jüttner distribution. The impact of the core electron polarization on the radiative recombination cross-section is estimated for the Ne-like iron ion and for highly-charged tungsten ions within an analytical approximation using the Dirac–Fock electron wave functions. The effect is shown to enhance the radiative recombination cross-sections by ≲20%. The enhancement depends on the photon energy, the principal quantum number of polarized shells and the ion charge. The influence of plasma temperature and density on the electron structure of ions in local thermodynamic equilibrium plasmas is investigated. Results for the iron and uranium ions in dense plasmas are in good agreement with previous calculations. New calculations were performed for the tungsten ion in dense plasmas on the basis of the average-atom model, as well as for the impurity tungsten ion in fusion plasmas using the non-linear self-consistent field screening model. The temperature and density dependence of the ion charge, level energies and populations are considered.

  8. Kinetics of radiation-induced structural alterations in electron-irradiated polymer-based composites

    Zaikin, Yu.A.; Potanin, A.S.; Koztaeva, U.P.

    2002-01-01

    Complete text of publication follows. In our previous studies measurements of internal friction temperature dependence were used for characterization of thermally activated and radiation-induced structural evolution in different types of polymer-based composites. This paper supplements these measurements with kinetic studies of internal friction (IF) parameters and EPR signals in a glass-cloth epoxy-filled laminate ST-ETF after electron irradiation up to doses of 1-10 MGy. Experiment have shown that the lifetime of free radicals in this composite considerably exceeds the characteristic time of molecular structural rearrangement due to scission and cross-linking after irradiation, as determined from IF measurements. This result is explained by slow proceeding of sterically hindered disproportionation reactions that stabilize the end groups of the macro-chain disrupt during irradiation and finally fix the act of scission. A mathematical model is formulated for description of structural evolution and alterations of IF parameters in polymer-based composites during and after electron irradiation. The description is based on the track model of radiation damage in polymers and phenomenological theory of radiation-induced structural transformations. General description does not give details of radiation-chemical conversion in different structural components of composites but indicates the direction of their structural evolution. In the model considered a composite material was divided into three parts (binder, filler, and a boundary layer). It was supposed that after primary distribution of radiation energy radiation-chemical conversion proceeds independently in each of these regions. It was also suggested that all the radical reactions were of the second order. On the example of glass-cloth laminate ST-ETF it is shown that this model allows to describe alterations in composite structural characteristics during irradiation and in the course of their self-organization after

  9. The quiet time structure of energetic (35--560 keV) radiation belt electrons

    Lyons, L.R.; Williams, D.J.

    1975-01-01

    Detailed Explorer 45 equatorial observations of the quiet time structure of radiation belt electrons (35--560 keV) for 1.7approximately-less-thanLapproximately-less-than5.2 are presented. Throughout the slot region and outer regions of the plasmasphere the observed pitch angle distributions are found to agree with those expected from resonant interactions with the plasmaspheric whistler mode wave band. Coulomb collisions become the dominant loss mechanism within the inner zone. The overall two-zone structure of the observed radial profiles is found to agree with the equilibrium structure expected to result from a balance between pitch angle scattering losses and radial diffusion from an average outer zone source. This agreement suggests that the dominant quiet time source and loss mechanisms have been identified and evaluated for energetic radiation belt electrons within the plasmasphere. In the outer regions of the plasmasphere (Lapprox.5) the equilibrium structure is observed to be modified by daily flux variations associated with changes in the level of magnetic activity that occur even during relatively quiet times. Within the inner region of the plasmasphere (Lapproximately-less-than3.5), electron fluxes are decoupled from these magnetic activity variations by the long time scales (>10 days) required for pitch angle and radial diffusion. Consequently, fluxes of these electrons are observed to remain nearly constant at equilibrium levels throughout the quiet periods examined

  10. Coherent Radiation of Electron Cloud

    Heifets, S.

    2004-01-01

    The electron cloud in positron storage rings is pinched when a bunch passes by. For short bunches, the radiation due to acceleration of electrons of the cloud is coherent. Detection of such radiation can be used to measure the density of the cloud. The estimate of the power and the time structure of the radiated signal is given in this paper

  11. First measurements of subpicosecond electron beam structure by autocorrelation of coherent diffraction radiation

    Lumpkin, Alex H; Rule, D W

    2001-01-01

    We report the initial measurements of subpicosecond electron beam structure using a nonintercepting technique based on the autocorrelation of coherent diffraction radiation (CDR). A far infrared (FIR) Michelson interferometer with a Golay detector was used to obtain the autocorrelation. The radiation was generated by a thermionic rf gun beam at 40 MeV as it passed through a 5-mm-tall slit/aperture in a metal screen whose surface was at 45 deg. to the beam direction. For the observed bunch lengths of about 450 fs (FWHM) with a shorter time spike on the leading edge, peak currents of about 100 A are indicated. Also a model was developed and used to calculate the CDR from the back of two metal strips separated by a 5-mm vertical gap. The demonstrated nonintercepting aspect of this method could allow on-line bunch length characterizations to be done during free-electron laser experiments.

  12. Radiation damage of silicon structures with electrons of 900 MeV

    Rachevskaia, I; Bosisio, L; Dittongo, S; Quai, E; Rizzo, G

    2002-01-01

    We present first results on the irradiation of double-sided silicon microstrip detectors and test structures performed at the Elettra synchrotron radiation facility at Trieste, Italy. The devices were irradiated with 900 MeV electrons. The test structures we used for studying bulk, surface and oxide irradiation damage were guard ring diodes, gated diodes and MOS capacitors. The test structures and the double-sided microstrip detectors were produced by Micron Semiconductor Ltd. (England) and IRST (Trento, Italy). For the first time, bulk-type inversion is observed to occur after high-energy electron irradiation. Current and inter-strip resistance measurements performed on the microstrip detectors show that the devices are still usable after type inversion.

  13. FOREWORD: IX International Symposium on Radiation from Relativistic Electrons in Periodic Structures (RREPS-2011)

    Potylitsyn, Alexander; Karataev, Pavel

    2012-05-01

    This volume contains papers presented at the IX International Symposium on Radiation from Relativistic Electrons in Periodic Structures (RREPS'11) which was held at Royal Holloway, University of London on September 12-16, Egham, United Kingdom. The symposium was organized jointly by Royal Holloway, University of London and Tomsk Polytechnic University, Tomsk, Russia. RREPS is a biennial series of symposia founded in September 1993 as an initiative of the Nuclear Physics Institute at Tomsk Polytechnic University. The intention was to strengthen the basic and applied research focused on radiation from relativistic electrons in condensed media, particularly from natural and artificial periodic structures, and to review the research activity in this area. Since then, the symposium has developed into a forum attracting young scientists from different areas of research and from many countries. Previous successful symposia were held at Tomsk, Russia (1993, 1995, 1997, 2003), Lake Baikal, Russia (1999), Lake Aiya, Altai, Russia (2001), Czech Technical University in Prague, Czech Republic (2007) and Zvenigorod, Moscow region, Russia (2009). As an outcome of the symposia the conference proceedings have been published in Nuclear Instruments and Methods in Physics Research, Section B (Vol. 145 No 1-2, October 1998; Vol. 173 No 1-2, January 2001; Vol. 201 No 1 January 2003; Vol. 227 No 1-2, January 2005; Vol. 266 No 17, September 2008) and Journal of Physics: Conference Series (Vol. 236, June 2010). The purpose of the present RREPS'11 symposium was to review the up-to-date situation in the area of electromagnetic radiation generated by relativistic charged particles in condensed media, and to discuss the research strategy for the near future. Nowadays, electromagnetic radiation studies cover electron energies from a few MeV up to hundreds of GeV in many laboratories throughout the world. The goal is to study the physics of the generation of various kinds of radiation and their

  14. Determination of morphology and electronic structure in solids with 20-1000 eV radiation

    Denley, D.R.

    1979-08-01

    One of the most versatile probes for spectroscopy is the photon because it is readily tuned through a wide range of frequencies, it is chargeless, and because of the additional information available from its vector nature. With the advent of intense radiation light sources a nearly untouched region of the spectrum has become available for a wide range of new experiments. Two of the main techniques in use are those of absorption and photoemission. This thesis uses these techniques on a variety of different materials for the analysis of their morphology and electronic structure. The principles underlying the techniques of soft-x-ray absorption, bulk-, and surface-photoemission are discussed together with some of the experimental methods and instrumentation.

  15. Determination of morphology and electronic structure in solids with 20-1000 eV radiation

    Denley, D.R.

    1979-08-01

    One of the most versatile probes for spectroscopy is the photon because it is readily tuned through a wide range of frequencies, it is chargeless, and because of the additional information available from its vector nature. With the advent of intense radiation light sources a nearly untouched region of the spectrum has become available for a wide range of new experiments. Two of the main techniques in use are those of absorption and photoemission. This thesis uses these techniques on a variety of different materials for the analysis of their morphology and electronic structure. The principles underlying the techniques of soft-x-ray absorption, bulk-, and surface-photoemission are discussed together with some of the experimental methods and instrumentation

  16. Radiative electron capture

    Biggerstaff, J.A.; Appleton, B.R.; Datz, S.; Moak, C.D.; Neelavathi, V.N.; Noggle, T.S.; Ritchie, R.H.; VerBeek, H.

    1975-01-01

    Some data are presented for radiative electron capture by fast moving ions. The radiative electron capture spectrum is shown for O 8+ in Ag, along with the energy dependence of the capture cross-section. A discrepancy between earlier data, theoretical prediction, and the present data is pointed out. (3 figs) (U.S.)

  17. Track structure analysis illustrating the prominent role of low-energy electrons in radiobiological effects of low-LET radiations

    Nikjoo, H.; Goodhead, D.T.

    1991-01-01

    Monte Carlo track structure methods have been used to illustrate the importance of low-energy electrons produced by low-LET radiations. It is shown that these low-energy secondary electrons contribute substantially to the dose in all low-LET irradiations and are particularly efficient at producing highly localized clusters of atomic damage which may be responsible for a major part of the biological effectiveness of low-LET radiations. The data generated by Monte Carlo track structure techniques and by earlier semi-analytical methods based on the LET concept have been compared in terms of cumulative and differential fractions of total dose absorbed as a function of electron energy. The data show that low-energy secondary electrons account for up to nearly 50% of the total dose imparted to a medium when irradiated with electrons or photons. (author)

  18. Effect of the electronic structure of the etched CdTe single crystals on the exciton radiation processes

    Tkachuk, P.M.; Tkachuk, V.Yi.; Mel'nichuk, S.V.; Kurik, M.V.

    2005-01-01

    Under optical excitation the structure of the radiation beyond fundamental absorption of the orientated CdTe single crystals caused by LO-phonon scattering processes of the electron-hole states is observed. Crystals have been doped with impurity of Cl as a result of the surface preparing by etching in Br-methanol. Electronic structure of the single crystals surface layer is identified on the basis of two-phonon radiation absorption investigation. Taking into account the modes selection rules the one and two phonon scattering mechanisms for two crystals surface orientations are determined

  19. Relation of radiation damage of metallic solids to electronic structure. Pt. 5

    Shalaev, A.M.; Adamenko, A.A.

    1977-01-01

    The problem of relating a damage in metal solids to the parameters of radiation fluxes and the physical nature of a target is considered. Basing upon experimental and theoretical investigations into the processes of interaction of particle fluxes with solids, the following conclusions have been reached. Threshold energy of ion displacement in the crystal lattice of a metal solid is dependent on the energy of a bombarding particle, which is due to ionization and electroexcitation stimulated by energy transfer from a fast particle to a system of collectivized electrons. The rate of metal solid damage by radiation depends on the state of the crystal lattice, in particular on its defectness. Variations of local electron density in the vicinity of a defect are related with changing thermodynamic characteristics of radiation-induced defect formation. A type of atomic bond in a solid affects the rate of radiation damage. The greatest damage occurs in materials with a covalent bond

  20. Correlating electronic and geometric structures of organic films and interfaces by means of synchrotron radiation based techniques

    Yamane, Hiroyuki

    2013-01-01

    The electronic structure of organic thin films and interfaces plays a crucial role in the performance of optoelectronic devices using organic semiconductors, and is seriously dominated by the geometric film/interface structure due to the anisotropic spatial distribution of molecular orbitals. This paper briefly reviews the recent progress of the examination of correlating electronic structure and geometric structure of archetypal organic semiconductor thin films and interfaces by using spectroscopic experiments with synchrotron radiation such as angle-resolved photoelectron spectroscopy, x-ray absorption spectroscopy, and x-ray standing wave. (author)

  1. Relationship Between Chromatin Structure and Sensitivity to Molecularly Targeted Auger Electron Radiation Therapy

    Terry, Samantha Y.A.; Vallis, Katherine A.

    2012-01-01

    Purpose: The open structure of euchromatin renders it susceptible to DNA damage by ionizing radiation (IR) compared with compact heterochromatin. The effect of chromatin configuration on the efficacy of Auger electron radiotherapy was investigated. Methods and Materials: Chromatin structure was altered in MDA-MB-468 and 231-H2N human breast cancer cells by suberoylanilide hydroxamic acid (SAHA), 5-aza-2-deoxycytidine, or hypertonic treatment. The extent and duration of chromatin structural changes were evaluated using the micrococcal nuclease assay. DNA damage (γH2AX assay) and clonogenic survival were evaluated after exposure to 111 In-DTPA-hEGF, an Auger electron-emitting radiopharmaceutical, or IR. The intracellular distribution of 111 In-DTPA-hEGF after chromatin modification was investigated in cell fractionation experiments. Results: Chromatin remained condensed for up to 20 minutes after NaCl and in a relaxed state 24 hours after SAHA treatment. The number of γH2AX foci per cell was greater in MDA-MB-468 and 231-H2N cells after IR (0.5 Gy) plus SAHA (1 μM) compared with IR alone (16 ± 0.6 and 14 ± 0.3 vs. 12 ± 0.4 and 11 ± 0.2, respectively). More γH2AX foci were observed in MDA-MB-468 and 231-H2N cells exposed to 111 In-DTPA-hEGF (6 MBq/μg) plus SAHA vs. 111 In-DTPA-hEGF alone (11 ± 0.3 and 12 ± 0.7 vs. 9 ± 0.4 and 7 ± 0.3, respectively). 5-aza-2-deoxycytidine enhanced the DNA damage caused by IR and 111 In-DTPA-hEGF. Clonogenic survival was reduced in MDA-MB-468 and 231-H2N cells after IR (6 Gy) plus SAHA (1 μM) vs. IR alone (0.6% ± 0.01 and 0.3% ± 0.2 vs. 5.8% ± 0.2 and 2% ± 0.1, respectively) and after 111 In-DTPA-hEGF plus SAHA compared to 111 In-DTPA-hEGF alone (21% ± 0.4% and 19% ± 4.6 vs. 33% ± 2.3 and 32% ± 3.7). SAHA did not affect 111 In-DTPA-hEGF nuclear localization. Hypertonic treatment resulted in fewer γH2AX foci per cell after IR and 111 In-DTPA-hEGF compared to controls but did not significantly alter clonogenic

  2. Interfacial electronic structure of Na deposited on rubrene thin film studied by synchrotron radiation photoemission

    Wei, Ching-Hsuan; Cheng, Chiu-Ping; Lin, Hong-Cheu; Pi, Tun-Wen

    2015-01-01

    Graphical abstract: - Highlights: • Na deposited on rubrene had undergone three-stage development process via (1) atomic diffusion, (2) atomic incorporation in the surface region, (3) formation of a metallic film. • High resolution core-level photoemission was used to determine the location of the doped Na atoms, which is affiliated at the end position of the tetracene-like backbone. • Na metal was formed on the rubrene thin film. • Ionization potential of the organic molecule regulated with different Na doping concentration could be controllable and favorable in practical applications. - Abstract: The electronic structure of rubrene doped with various concentrations of Na was studied by synchrotron-radiation photoemission. Three stages of development were found with increasing Na concentration; Na penetrating deep into the organic film, followed by development of gap states, and ended with a metallic Na film. The charge transfer from Na to rubrene resulted in a vacuum-level shift. By doping Na into rubrene, we could control the IP of the organic molecule, which is favorable for application in organic semiconductor devices.

  3. Nuclear resonance scattering of synchrotron radiation as a unique electronic, structural and thermodynamic probe

    Alp, E. Ercan; Sturhahn, Wolfgang; Toellner, Thomas S.; Zhao, Jiyong; Leu, Bogdan M.

    2012-01-01

    Discovery of Moessbauer effect in a nuclear transition was a remarkable development. It revealed how long-lived nuclear states with relatively low energies in the kiloelectron volt (keV) region can be excited without recoil. This new effect had a unique feature involving a coupling between nuclear physics and solid-state physics, both in terms of physics and sociology. Physics coupling originates from the fact that recoilless emission and absorption or resonance is only possible if the requirement that nuclei have to be bound in a lattice with quantized vibrational states is fulfilled, and that the finite electron density on the nucleus couples to nuclear degrees of freedom leading to hyperfine interactions. thus, Moessbauer spectroscopy allows peering into solid-state effects using unique nuclear transitions. Sociological aspects of this coupling had been equally startling and fruitful. The interaction between diverse scientific communities, who learned to use Moessbauer spectroscopy proved to be very valuable. For example, biologists, geologists, chemists, physics, materials scientists, and archeologists, all sharing a common spectroscopic technique, also learned to appreciate the beauty and intricacies of each other's fields. As a laboratory-based technique, Moessbauer spectroscopy matured by the end of the 1970s. Further exciting developments took place when accelerator-based techniques were employed, like synchrotron radiation or 'in-beam'Moessbauer experiments with implanted radioactive ions. More recently, two Moessbauer spectrometers on the surface of the Mars kept the technique vibrant and viable up until present time. In this chapter, the authors look into some of the unique aspects of nuclear resonance excited with synchrotron radiation as a probe of condensed matter, including magnetism, valence, vibrations, and lattice dynamics, and review the development of nuclear resonance inelastic x-ray scattering (NRIXS) and synchrotron Moessbauer spectroscopy

  4. Structural stability of PAN fiber under high electron beam radiation doses

    Pino, Eddy S.; Machado, Luci D.B.; Arruda, Clarissa P. Zelinschi de; Carvalho, Alvaro A. Silva de; Giovedi, Claudia

    2009-01-01

    Fiber-reinforced composite are an important class of engineering material. A relevant task of composite technology in order to produce materials for structures of high mechanical performance is to obtain the best carbon fiber. One of the main ways to produce carbon fibers of high Young's modulus and tensile strength is to use as starting material polyacrylonitrile (PAN) fibers which after a rigorous and carefully thermal process become carbon fibers. Since some chemical modifications produced in the thermal treatment can be induced by ionizing radiation, the aim of this paper is to evaluate the effect of high electron beam (EB) doses on a commercial PAN fiber in order to evaluate the use of this technology as an alternative treatment to improve the properties and characteristics of the produced carbon fiber. The doses applied were: 0.2, 0.4, 0.6, 0.8, 1.0 and 1.2 MGy. The irradiation effects induced on the PAN fiber were evaluated by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and thermogravimetry (TG). FTIR obtained data have shown that the main functional groups remain practically unchanged in the non-irradiated and irradiated samples. The single DSC exothermic peak obtained for non-irradiated sample, becomes a double peak after the irradiation, presenting lower initial and higher final temperatures for exothermic DSC curves. The enthalpy involved in the chemical reaction decreases for irradiated samples as compared with the non-irradiated PAN fiber. TG data have shown that irradiated samples start a decomposition process at lower temperatures compared to the non-irradiated sample. (author)

  5. Structural characterization of annatto seeds (Bixa orellana) by transmission and scanning electron microscopy submitted to gamma radiation for dormancy break

    Harder, Marcia N.C.; Nogueira, Neusa L.; Arthur, Valter; Rossi, Monica L.; Rodriguez, Adriana P.M. [Centro de Energia Nuclear na Agricultura (CENA/USP), Piracicaba, SP (Brazil)]. E-mails: mnharder@cena.usp.br; nogueira@cena.usp.br; arthur@cena.usp.br; mnicalr@cena.usp.br; riana@cena.usp.br

    2007-07-01

    The annatto (Bixa orellana) is the only species of the Bixaceae family. From the seeds an important food colorant is obtained, bixin, for the industry and domestic use. More recently studies have focused more extensively in medicinal purpose of the species. Due to structural and physiologic characteristics, the seeds have low germination rate, around 30 %. The irradiation of seeds with gamma radiation can promote the increase and/or acceleration of germination, better plant development and productivity, among other aspects. The radiation doses used for this purpose should not cause genetic modifications in the organism, hence experimentation is needed to define the appropriate doses. Absence of research done annatto related to the use of the irradiation aiming at the increase of germination rates lead to the structural characterization of the annatto seeds submitted to gamma radiation through transmission (TEM) and scanning electron microscopy (SEM). The objective of this study was to verify the effect of radiation on the seeds structures during the process of dormancy break. Dry seeds and seeds immersed in distilled water for 24 hours were submitted to gamma radiation from source of Co{sup 60} type Gammacell-220 at CENA/USP, at doses 100 Gy. After irradiation the seeds were processed for TEM and SEM. Preliminary results, showed structural modifications in the seeds. (author)

  6. XI International Symposium on Radiation from Relativistic Electrons in Periodic Structures (RREPS2015)

    2016-01-01

    These Proceedings are published as a recollection of contributions presented at the XI International Symposium on “Radiation from Relativistic Electrons in Periodic Structures” (RREPS-15), which was held in Saint Petersburg, September 6-11, 2015, Russian Federation. RREPS-15 was co-organized by Saint-Petersburg State University, National Research Tomsk Polytechnic University, and National Research Nuclear University (MEPhI). The main goal of the symposium was to bring together the scientists from around the world who work on designs of new radiation sources and their applications. There were 108 participants registered from 12 countries. The website of the symposium is available at http://rreps.tpu.ru/. (paper)

  7. Resonant electronic transport through a triple quantum-dot with Λ-type level structure under dual radiation fields

    Guan, Chun; Xing, Yunhui; Zhang, Chao; Ma, Zhongshui

    2014-01-01

    Due to quantum interference, light can transmit through dense atomic media, a phenomenon known as electromagnetically induced transparency (EIT). We propose that EIT is not limited to light transmission and there is an electronic analog where resonant transparency in charge transport in an opaque structure can be induced by electromagnetic radiation. A triple-quantum-dots system with Λ-type level structure is generally opaque due to the level in the center dot being significantly higher and therefore hopping from the left dot to the center dot is almost forbidden. We demonstrate that an electromagnetically induced electron transparency (EIET) in charge of transport can indeed occur in the Λ-type system. The direct evidence of EIET is that an electron can travel from the left dot to the right dot, while the center dot apparently becomes invisible. We analyze EIET and the related shot noise in both the zero and strong Coulomb blockade regimes. It is found that the EIET (position, height, and symmetry) can be tuned by several controllable parameters of the radiation fields, such as the Rabi frequencies and detuning frequencies. The result offers a transparency/opaque tuning technique in charge transport using interfering radiation fields

  8. Electronic structure of radiation damage centre in zinc silicate from ESR hyperfine data

    Prasad, C.; Chakravarty, Sulata

    1979-01-01

    The occurrence of an ESR spectrum with six hyperfine components in X-irradiated zinc silicate, Zn 2 SiO was reported earlier. It is known that by the use of the experimental ESR data it is possible to work out the electronic structure of the paramagnetic damage center. The values of the hyperfine parameters A and B have been utilized to calculate the values of f'sub(s) and fsub(sigma), the fractional occupation of the 3s and 3psub(sigma) orbitals of the metal atom by the unpaired electron. The metal atom is 27 Al (I = 5/2, n.a. = 100%) which is present as an impurity in the lattice and occupies silicon sites. The bonding between the metal atom and each of the surrounding oxygen atom is assumed to be of the sigma-type. The values obtained for the fractional occupation are : f'sub(s) = 0.71 x 10sup(-2), fsub(sigma) = 14.65 x10sup(-2). The unpaired electron appears to belong to the ligand atom and is moderately delocalised on the Al atom where it occupies mainly the 3psup(sigma) orbital and not the 3s orbital. (auth.)

  9. Modeling molecule-plasmon interactions using quantized radiation fields within time-dependent electronic structure theory

    Nascimento, Daniel R.; DePrince, A. Eugene, E-mail: deprince@chem.fsu.edu [Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306-4390 (United States)

    2015-12-07

    We present a combined cavity quantum electrodynamics/ab initio electronic structure approach for simulating plasmon-molecule interactions in the time domain. The simple Jaynes-Cummings-type model Hamiltonian typically utilized in such simulations is replaced with one in which the molecular component of the coupled system is treated in a fully ab initio way, resulting in a computationally efficient description of general plasmon-molecule interactions. Mutual polarization effects are easily incorporated within a standard ground-state Hartree-Fock computation, and time-dependent simulations carry the same formal computational scaling as real-time time-dependent Hartree-Fock theory. As a proof of principle, we apply this generalized method to the emergence of a Fano-like resonance in coupled molecule-plasmon systems; this feature is quite sensitive to the nanoparticle-molecule separation and the orientation of the molecule relative to the polarization of the external electric field.

  10. Electron nature of chemically active state of spiropyran with nitro group. Dependence of efficiency of radiation colouring of spiropyrans on their structure

    Kholmanskij, A.S.; Zubkov, A.V.; Dyumaev, K.M.

    1980-01-01

    Using the theory of solvatochromy it is shown that chemically active state of spiropyran with nitro group is its highly polar electron-excitated state. On the basis of the image on the electron nature of chemically active state of spiropyran the dependence of the values of radiation yield of the coloured forms of spiropyrans upon their structure is explained

  11. Protonated ions as systemic trapping agents for noble gases: From electronic structure to radiative association.

    Ozgurel, O; Pauzat, F; Pilmé, J; Ellinger, Y; Bacchus-Montabonel, M-C; Mousis, O

    2017-10-07

    The deficiencies of argon, krypton, and xenon observed in the atmosphere of Titan as well as anticipated in some comets might be related to a scenario of sequestration by H 3 + in the gas phase at the early evolution of the solar nebula. The chemical process implied is a radiative association, evaluated as rather efficient in the case of H 3 + , especially for krypton and xenon. This mechanism of chemical trapping might not be limited to H 3 + only, considering that the protonated ions produced in the destruction of H 3 + by its main competitors present in the primitive nebula, i.e., H 2 O, CO, and N 2 , might also give stable complexes with the noble gases. However the effective efficiency of such processes is still to be proven. Here, the reactivity of the noble gases Ar, Kr, and Xe, with all protonated ions issued from H 2 O, CO, and N 2 , expected to be present in the nebula with reasonably high abundances, has been studied with quantum simulation method dynamics included. All of them give stable complexes and the rate coefficients of their radiative associations range from 10 -16 to 10 -19 cm 3 s -1 , which is reasonable for such reactions and has to be compared to the rates of 10 -16 to 10 -18 cm 3 s -1 , obtained with H 3 + . We can consider this process as universal for all protonated ions which, if present in the primitive nebula as astrophysical models predict, should act as sequestration agents for all three noble gases with increasing efficiency from Ar to Xe.

  12. Electronics for radiation detection

    2011-01-01

    Addresses the developments in the design of semiconductor detectors and integrated circuits, in the context of medical imaging using ionizing radiation. This book explains how circuits for radiation are built, focusing on practical information about how they are being used, rather than mathematical details.

  13. Multi-scale modelling of radiation damage in Fe-Cr based on ab initio electronic structure calculations

    Olsson, Paer

    2004-04-01

    The efficiency of fast neutron reactors, such as for fusion, breeding and transmutation, depend strongly on the neutron radiation resistance of the materials used in the reactors. The binary Fe-Cr alloy, which has many attractive properties in this regard, is the base for the best steels of today which are, however, still not up to the required standards. Therefore, substantial effort has been devoted to finding new materials that can cope with the demands better. Experimental studies must be complemented with extensive theoretical modelling in order to understand the effects that different alloying elements has on the resistance properties of materials. To this end, the first steps of multi-scale modelling has been taken, starting out with ab initio calculations of the electronic structure of the complete concentration range range of the disordered binary Fe-C alloy. The mixing enthalpy of Fe-Cr has been quantitatively predicted and has, together with data from literature, been used in order to fit two sets of interatomic potentials for the purpose of simulating defect evolution with molecular dynamics and kinetic Monte-Carlo codes. These dedicated Fe-Cr alloy potentials are new and represent important additions to the pure element potentials that can be found in literature

  14. Multi-scale modelling of radiation damage in Fe-Cr based on ab initio electronic structure calculations

    Olsson, Paer

    2004-04-01

    The efficiency of fast neutron reactors, such as for fusion, breeding and transmutation, depend strongly on the neutron radiation resistance of the materials used in the reactors. The binary Fe-Cr alloy, which has many attractive properties in this regard, is the base for the best steels of today which are, however, still not up to the required standards. Therefore, substantial effort has been devoted to finding new materials that can cope with the demands better. Experimental studies must be complemented with extensive theoretical modelling in order to understand the effects that different alloying elements has on the resistance properties of materials. To this end, the first steps of multi-scale modelling has been taken, starting out with ab initio calculations of the electronic structure of the complete concentration range range of the disordered binary Fe-C alloy. The mixing enthalpy of Fe-Cr has been quantitatively predicted and has, together with data from literature, been used in order to fit two sets of interatomic potentials for the purpose of simulating defect evolution with molecular dynamics and kinetic Monte-Carlo codes. These dedicated Fe-Cr alloy potentials are new and represent important additions to the pure element potentials that can be found in literature.

  15. Three-dimensional data assimilation and reanalysis of radiation belt electrons: Observations of a four-zone structure using five spacecraft and the VERB code

    Kellerman, A. C.; Shprits, Y. Y.; Kondrashov, D.; Subbotin, D.; Makarevich, R. A.; Donovan, E.; Nagai, T.

    2014-11-01

    Obtaining the global state of radiation belt electrons through reanalysis is an important step toward validating our current understanding of radiation belt dynamics and for identification of new physical processes. In the current study, reanalysis of radiation belt electrons is achieved through data assimilation of five spacecraft with the 3-D Versatile Electron Radiation Belt (VERB) code using a split-operator Kalman filter technique. The spacecraft data are cleaned for noise, saturation effects, and then intercalibrated on an individual energy channel basis, by considering phase space density conjunctions in the T96 field model. Reanalysis during the CRRES era reveals a never-before-reported four-zone structure in the Earth's radiation belts during the 24 March 1991 shock-induced injection superstorm: (1) an inner belt, (2) the high-energy shock-injection belt, (3) a remnant outer radiation belt, and (4) a second outer radiation belt. The third belt formed near the same time as the second belt and was later enhanced across keV to MeV energies by a second particle injection observed by CRRES and the Northern Solar Terrestrial Array riometer network. During the recovery phase of the storm, the fourth belt was created near L*=4RE, lasting for several days. Evidence is provided that the fourth belt was likely created by a dominant local heating process. This study outlines the necessity to consider all diffusive processes acting simultaneously and the advantage of supporting ground-based data in quantifying the observed radiation belt dynamics. It is demonstrated that 3-D data assimilation can resolve various nondiffusive processes and provides a comprehensive picture of the electron radiation belts.

  16. Radiation induced nano structures

    Ibragimova, E.M.; Kalanov, M.U.; Khakimov, Z.

    2006-01-01

    Full text: Nanometer-size silicon clusters have been attracting much attention due to their technological importance, in particular, as promising building blocks for nano electronic and nano photonic systems. Particularly, silicon wires are of great of interest since they have potential for use in one-dimensional quantum wire high-speed field effect transistors and light-emitting devices with extremely low power consumption. Carbon and metal nano structures are studied very intensely due to wide possible applications. Radiation material sciences have been dealing with sub-micron objects for a long time. Under interaction of high energy particles and ionizing radiation with solids by elastic and inelastic mechanisms, at first point defects are created, then they form clusters, column defects, disordered regions (amorphous colloids) and finally precipitates of another crystal phase in the matrix. Such irradiation induced evolution of structure defects and phase transformations was observed by X-diffraction techniques in dielectric crystals of quartz and corundum, which exist in and crystal modifications. If there is no polymorphism, like in alkali halide crystals, then due to radiolysis halogen atoms are evaporated from the surface that results in non-stoichiometry or accumulated in the pores formed by metal vacancies in the sub-surface layer. Nano-pores are created by intensive high energy particles irradiation at first chaotically and then they are ordered and in part filled by inert gas. It is well-known mechanism of radiation induced swelling and embrittlement of metals and alloys, which is undesirable for construction materials for nuclear reactors. Possible solution of this problem may come from nano-structured materials, where there is neither swelling nor embrittlement at gas absorption due to very low density of the structure, while strength keeps high. This review considers experimental observations of radiation induced nano-inclusions in insulating

  17. Automatic atlas based electron density and structure contouring for MRI-based prostate radiation therapy on the cloud

    Dowling, J A; Burdett, N; Chandra, S; Rivest-Hénault, D; Ghose, S; Salvado, O; Fripp, J; Greer, P B; Sun, J; Parker, J; Pichler, P; Stanwell, P

    2014-01-01

    Our group have been developing methods for MRI-alone prostate cancer radiation therapy treatment planning. To assist with clinical validation of the workflow we are investigating a cloud platform solution for research purposes. Benefits of cloud computing can include increased scalability, performance and extensibility while reducing total cost of ownership. In this paper we demonstrate the generation of DICOM-RT directories containing an automatic average atlas based electron density image and fast pelvic organ contouring from whole pelvis MR scans.

  18. Automatic Atlas Based Electron Density and Structure Contouring for MRI-based Prostate Radiation Therapy on the Cloud

    Dowling, J. A.; Burdett, N.; Greer, P. B.; Sun, J.; Parker, J.; Pichler, P.; Stanwell, P.; Chandra, S.; Rivest-Hénault, D.; Ghose, S.; Salvado, O.; Fripp, J.

    2014-03-01

    Our group have been developing methods for MRI-alone prostate cancer radiation therapy treatment planning. To assist with clinical validation of the workflow we are investigating a cloud platform solution for research purposes. Benefits of cloud computing can include increased scalability, performance and extensibility while reducing total cost of ownership. In this paper we demonstrate the generation of DICOM-RT directories containing an automatic average atlas based electron density image and fast pelvic organ contouring from whole pelvis MR scans.

  19. Radiation hardening of smart electronics

    Mayo, C.W.; Cain, V.R.; Marks, K.A.; Millward, D.G.

    1991-02-01

    Microprocessor based ''smart'' pressure, level, and flow transmitters were tested to determine the radiation hardness of this class of electronic instrumentation for use in reactor building applications. Commercial grade Complementary Metal Oxide Semiconductor (CMOS) integrated circuits used in these transmitters were found to fail at total gamma dose levels between 2500 and 10,000 rad. This results in an unacceptably short lifetime in many reactor building radiation environments. Radiation hardened integrated circuits can, in general, provide satisfactory service life for normal reactor operations when not restricted to the extremely low power budget imposed by standard 4--20 mA two-wire instrument loops. The design of these circuits will require attention to vendor radiation hardness specifications, dose rates, process control with respect to radiation hardness factors, and non-volatile programmable memory technology. 3 refs., 2 figs

  20. Simultaneous Out-of-band Interference Rejection and Radiation Enhancement in an Electronic Product via an EBG Structure

    Ruaro, Andrea; Thaysen, Jesper; Jakobsen, Kaj Bjarne

    2014-01-01

    to achieve simultaneously both the enhancement of the antenna radiation efficiency and the shrinking of its dimensions, while making the device more resilient to out-of-band electromagnetic interference (EMI). The patterning of the ground plane allows, in fact, to effectively suppress higher-order resonances......This work presents an application of a planar electromagnetic band gap (EBG) structure with a perspective product implementation in the back of the mind. The focus is on the integration of such structure under the constraint of space and system coexistence. It is discovered that it is possible...... (alternatively, parallel plate noise) and decrease the radiation efficiency of the structure forbidding higher-order modes to propagate and subsequently be diffracted by the ground plane....

  1. Growth of metastable fcc Mn thin film on GaAs(001) and its electronic structure studied by photoemission with synchrotron radiation

    Chen Yan; Dong Guosheng; Zhang Ming

    1995-01-01

    The epitaxial growth of metastable fcc Mn thin films on GaAs(001) surface has been achieved at a substrate temperature of 400 K. The development of the fcc Mn thin films as a function of coverage is studied by photoemission with synchrotron radiation. The electron density of states below the Fermi edge of the fcc Mn phase is measured. A significant difference of the electronic structures is observed between the metastable fcc Mn phase and the thermodynamically stable α-Mn phase. Possible mechanisms are proposed to interpret the experimental result

  2. Electronic structure in Bi2Sr2CaCu2O8 studied by two dimensional angular correlation of positron annihilation radiations

    Kondo, H.; Kubota, T.; Nakashima, N.; Tanigawa, S.; Minami, F.; Takekawa, S.

    1992-01-01

    Electronic structure in one of high-Tc-sperconducting materials, Bi 2 Sr 2 CaCu 2 O 8 , was studied by two dimensional angular correlation of positron annihilation radiations (2D-ACAR). The measurements were performed for Bi 2 Sr 2 CaCu 2 O 8 at room temperature and 24K; in the normal and superconducting states. The three dimensional electron momentum density ρ(p) has been reconstructed by using the image reconstruction technique based on a direct Fourier transportation. The reconstructed electron momentum density ρ(p) has been reduced into the reduced electron momentum density n(k) by using the LCW folding procedure. They are compared with that for Cu and Si. The difference in the density distributions between both states was observed. This may be attributed to the smearing by the reduced thermal momenta of positrons. But there is a possibility that the difference is due to the phase transition

  3. Analog electronics for radiation detection

    2016-01-01

    Analog Electronics for Radiation Detection showcases the latest advances in readout electronics for particle, or radiation, detectors. Featuring chapters written by international experts in their respective fields, this authoritative text: Defines the main design parameters of front-end circuitry developed in microelectronics technologies Explains the basis for the use of complementary metal oxide semiconductor (CMOS) image sensors for the detection of charged particles and other non-consumer applications Delivers an in-depth review of analog-to-digital converters (ADCs), evaluating the pros and cons of ADCs integrated at the pixel, column, and per-chip levels Describes incremental sigma delta ADCs, time-to-digital converter (TDC) architectures, and digital pulse-processing techniques complementary to analog processing Examines the fundamental parameters and front-end types associated with silicon photomultipliers used for single visible-light photon detection Discusses pixel sensors ...

  4. Radiation shielding wall structure

    Nishimura, Yoshitaka; Oka, Shinji; Kan, Toshihiko; Misato, Takeshi.

    1990-01-01

    A space between a pair of vertical steel plates laterally disposed in parallel at an optional distance has a structure of a plurality of vertically extending tranks partitioned laterally by vertically placed steel plates. Then, cements are grouted to the tranks. Strip-like steel plates each having a thickness greater than the gap between the each of the vertically placed steel plates and the cement are bonded each at the surface for each of the vertically placed steel plates opposing to the cements. A protrusion of a strip width having radiation shielding performance substantially identical with that by the thickness of the cement is disposed in the strip-like steel plates. With such a constitution, a safety radiation shielding wall structure with no worry of radiation intrusion to gaps, if formed, between the steel plates and the grouted cements due to shrinkage of the cements. (I.N.)

  5. Infrared synchrotron radiation from electron storage rings

    Duncan, W.D.; Williams, G.P.

    1983-01-01

    Simple and useful approximations, valid at infrared wavelengths, to the equations for synchrotron radiation are presented and used to quantify the brightness and power advantage of current synchrotron radiation light sources over conventional infrared broadband laboratory sources. The Daresbury Synchrotron Radiation Source (SRS) and the Brookhaven National Synchrotron Light Source (vacuum ultraviolet) [NSLS(VUV)] storage rings are used as examples in the calculation of the properties of infrared synchrotron radiation. The pulsed nature of the emission is also discussed, and potential areas of application for the brightness, power, and time structure advantages are presented. The use of infrared free electron lasers and undulators on the next generation of storage ring light sources is briefly considered

  6. A facility for the analysis of the electronic structures of solids and their surfaces by synchrotron radiation photoelectron spectroscopy

    Hoesch, M.; Kim, T. K.; Dudin, P.; Wang, H.; Scott, S.; Harris, P.; Patel, S.; Matthews, M.; Hawkins, D.; Alcock, S. G.; Richter, T.; Mudd, J. J.; Basham, M.; Pratt, L.; Leicester, P.; Longhi, E. C.; Tamai, A.; Baumberger, F.

    2017-01-01

    A synchrotron radiation beamline in the photon energy range of 18-240 eV and an electron spectroscopy end station have been constructed at the 3 GeV Diamond Light Source storage ring. The instrument features a variable polarisation undulator, a high resolution monochromator, a re-focussing system to form a beam spot of 50 × 50 μm2, and an end station for angle-resolved photoelectron spectroscopy (ARPES) including a 6-degrees-of-freedom cryogenic sample manipulator. The beamline design and its performance allow for a highly productive and precise use of the ARPES technique at an energy resolution of 10-15 meV for fast k-space mapping studies with a photon flux up to 2 ṡ 1013 ph/s and well below 3 meV for high resolution spectra.

  7. Simulation of planar channeling-radiation spectra of relativistic electrons and positrons channeled in a diamond-structure or tungsten single crystal (classical approach)

    Azadegan, B.; Wagner, W.

    2015-01-01

    We present a Mathematica package for simulation of spectral-angular distributions and energy spectra of planar channeling radiation of relativistic electrons and positrons channeled along major crystallographic planes of a diamond-structure or tungsten single crystal. The program is based on the classical theory of channeling radiation which has been successfully applied to study planar channeling of light charged particles at energies higher than 100 MeV. Continuous potentials for different planes of diamond, Si, Ge and W single crystals are calculated using the Doyle–Turner approximation to the atomic scattering factor and taking thermal vibrations of the crystal atoms into account. Numerical methods are applied to solve the classical one-dimensional equation of motion. The code is designed to calculate the trajectories, velocities and accelerations of electrons (positrons) channeled by the planar continuous potential. In the framework of classical electrodynamics, these data allow realistic simulations of spectral-angular distributions and energy spectra of planar channeling radiation. Since the generated output is quantitative, the results of calculation may be useful, e.g., for setup configuration and crystal alignment in channeling experiments, for the study of the dependence of channeling radiation on the input parameters of particle beams with respect to the crystal orientation, but also for the simulation of positron production by means of pair creation what is mandatory for the design of efficient positron sources necessary in high-energy and collider physics. Although the classical theory of channeling is well established for long time, there is no adequate library program for simulation of channeling radiation up to now, which is commonly available, sufficiently simple and effective to employ and, therefore, of benefit as for special investigations as for a quick overview of basic features of this type of radiation

  8. Effect of electron beam radiation on the structure and mechanical properties of ultra high molecular weight polyethylene fibers

    Li Shujun; Sun Weijun; Liu Xiuju; Gao Yongzhong; Li Huisheng

    1998-01-01

    Ultra high molecular weight polyethylene fibers have been crosslinked by electron beam. The structure and mechanical properties of them have been investigated in different irradiation atmospheres. The obtained results show that the gel content and crosslinking density increase with the increase of dose, the swelling ratio and average molecular weight of crosslinked net decrease with the increase of dose, the tensile strength and failure elongation decrease with the increase of dose, the tensile modulus increases with the increase of dose. When the samples are irradiated in air, vacuum and acetylene atmospheres, the effect of irradiation in acetylene atmosphere is best

  9. Electron correlation explored through electron spectrometry using synchrotron radiation

    Caldwell, C.D.; Whitfield, S.B.; Flemming, M.G.

    1991-01-01

    The development of synchrotron radiation facilities as a research tool has made possible experiments which provide new insights into the role which correlation plays in electron dynamics and atomic and molecular structure. Features such as autoionizing resonances, normal and resonant Auger decay modes, and ionization threshold structure have become visible in a wealth of new detail. Some aspects of this information drawn from recent experiments on the alkaline earth metals and the rare gases are presented. The potential for increased flux and resolution inherent in insertion device-based facilities like the Advanced Light Source should advance this understanding even further, and some future directions are suggested. 8 refs., 8 figs

  10. Radiation damage to electronic components

    Battisti, S.; Bossart, R.; Schoenbacher, H.; Van de Voorde, M.

    1975-01-01

    Characteristic properties are presented of some 40 different electronic components (resistors, capacitors, diodes, transistors, and integrated circuits) which were irradiated in a nuclear reactor up to 1015 n/cm 2 (E > 1 MeV). Complete circuits (e.g. RF amplifiers and detectors, mixers, differential amplifiers, voltage-to-frequency converters, oscillators, power supplies) were irradiated near the CERN Intersecting Storage Rings up to 106 rad(RPL) (dose measured with radiophotoluminescent dosimeters) under simulated operational conditions. Representative measured parameters, such as resistance, capacitance, forward voltage, reverse current, toggle frequencies, are given in graphs as a function of radiation dose. The results are discussed in detail and lead to the over-all conclusion that the operation of electronic components and circuits is seriously affected by radiation environments with doses in the order of 10 13 n/cm 2 or 10 4 rad(RPL); some components and circuits fail completely at doses of 10 14 n/cm 2 or 10 5 rad(RPL). (Author)

  11. Electronic structure of silicene

    Voon, L. C. Lew Yan

    2015-01-01

    In this topical review, we discuss the electronic structure of free-standing silicene by comparing results obtained using different theoretical methods. Silicene is a single atomic layer of silicon similar to graphene. The interest in silicene is the same as for graphene, in being two-dimensional and possessing a Dirac cone. One advantage of silicene is due to its compatibility with current silicon electronics. Both empirical and first-principles techniques have been used to study the electronic properties of silicene. We will provide a brief overview of the parameter space for first-principles calculations. However, since the theory is standard, no extensive discussion will be included. Instead, we will emphasize what empirical methods can provide to such investigations and the current state of these theories. Finally, we will review the properties computed using both types of theories for free-standing silicene, with emphasis on areas where we have contributed. Comparisons to graphene is provided throughout. (topical review)

  12. Electronic band structure

    Grosso, G.

    1986-01-01

    The aim of this chapter is to present, in detail, some theoretical methods used to calculate electronic band structures in crystals. The basic strategies employed to attack the problem of electronic-structure calculations are presented. Successive sections present the basic formulations of the tight-binding, orthogonalized-plane-wave, Green'sfunction, and pseudopotential methods with a discussion of their application to perfect solids. Exemplifications in the case of a few selected problems provide further insight by the author into the physical aspects of the different methods and are a guide to the use of their mathematical techniques. A discussion is offered of completely a priori Hartree-Fock calculations and attempts to extend them. Special aspects of the different methods are also discussed in light of recently published related work

  13. Study by electronic structure calculations of the radiation damage in the UO2 nuclear fuel: behaviour of the point defects and fission gases

    Vathonne, Emerson

    2014-01-01

    Uranium dioxide (UO 2 ) is worldwide the most widely used fuel in nuclear plants in the world and in particular in pressurized water reactors (PWR). In-pile the fission of uranium nuclei creates fission products and point defects in the fuel. The understanding of the evolution of these radiation damages requires a multi-scale modelling approach of the nuclear fuel, from the scale of the pellet to the atomic scale. We used an electronic structure calculation method based on the density functional theory (DFT) to model radiation damage in UO 2 at the atomic scale. A Hubbard-type Coulomb interaction term is added to the standard DFT formalism to take into account the strong correlations of the 5f electrons in UO 2 . This method is used to study point defects with various charge states and the incorporation and diffusion of krypton in uranium dioxide. This study allowed us to obtain essential data for higher scale models but also to interpret experimental results. In parallel of this study, three ways to improve the state of the art of electronic structure calculations of UO 2 have been explored: the consideration of the spin-orbit coupling neglected in current point defect calculations, the application of functionals allowing one to take into account the non-local interactions such as van der Waals interactions important for rare gases and the use of the Dynamical Mean Field Theory combined to the DFT method in order to take into account the dynamical effects in the 5f electron correlations. (author) [fr

  14. A Mathematica package for calculation of planar channeling radiation spectra of relativistic electrons channeled in a diamond-structure single crystal (quantum approach)

    Azadegan, B.

    2013-03-01

    The presented Mathematica code is an efficient tool for simulation of planar channeling radiation spectra of relativistic electrons channeled along major crystallographic planes of a diamond-structure single crystal. The program is based on the quantum theory of channeling radiation which has been successfully applied to study planar channeling at electron energies between 10 and 100 MeV. Continuum potentials for different planes of diamond, silicon and germanium single crystals are calculated using the Doyle-Turner approximation to the atomic scattering factor and taking thermal vibrations of the crystal atoms into account. Numerical methods are applied to solve the one-dimensional Schrödinger equation. The code is designed to calculate the electron wave functions, transverse electron states in the planar continuum potential, transition energies, line widths of channeling radiation and depth dependencies of the population of quantum states. Finally the spectral distribution of spontaneously emitted channeling radiation is obtained. The simulation of radiation spectra considerably facilitates the interpretation of experimental data. Catalog identifier: AEOH_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEOH_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.: 446 No. of bytes in distributed program, including test data, etc.: 209805 Distribution format: tar.gz Programming language: Mathematica. Computer: Platforms on which Mathematica is available. Operating system: Operating systems on which Mathematica is available. RAM: 1 MB Classification: 7.10. Nature of problem: Planar channeling radiation is emitted by relativistic charged particles during traversing a single crystal in direction parallel to a crystallographic plane. Channeling is modeled as the motion

  15. The electronic structures of solids

    Coles, B R

    2013-01-01

    The Electronic Structures of Solids aims to provide students of solid state physics with the essential concepts they will need in considering properties of solids that depend on their electronic structures and idea of the electronic character of particular materials and groups of materials. The book first discusses the electronic structure of atoms, including hydrogen atom and many-electron atom. The text also underscores bonding between atoms and electrons in metals. Discussions focus on bonding energies and structures in the solid elements, eigenstates of free-electron gas, and electrical co

  16. Radiation dermatitis following electron beam therapy

    Price, N.M.

    1978-01-01

    Ten patients, who had been treated for mycosis fungoides with electron beam radiation ten or more years previously, were examined for signs of radiation dermatitis. Although most patients had had acute radiation dermatitis, only a few manifested signs of mild chronic changes after having received between 1,000 and 2,800 rads

  17. The structure and properties of free radicals: An electron spin resonance study of radiation damage to nucleic acid and protein components and to some sulfur-substituted derivitives

    Sagstuen, E.

    1979-01-01

    When cellular systems are exposed to ionizing radiation the long-term effects may range from minor disturbances to such dramatic changes as mutations and cell death. The processes leading to these macroscopical injuries are primarily confined at the molecular level. In all models aimed at a description of the action of radiation at the molecular level the formation of free radicals (which are species containing unpaired electrons) is a central concept. The technique of ESR spectroscopy is uniquely suited to study free radicals, as it is based on resonance absorption of energy by unpaired electrons in a magnetic field. ESR spectroscopy makes it possible to detect free radicals and, in some cases, to identify them. In order to study free radicals by ESR it is necessary to build up a sufficient number of unpaired spins in the sample (approximately 10 11 or more, depending on the shape of the resonance). This may be different techniques have been used to trap the induced radicals or to attain a sufficient steady state concentration level. A procedure which seems to contain a large amount of information is to irradiate at low temperatures, and, by subsequent heat-treatment of the sample to study the reactions and fate of the induced radicals. In this thesis single crystal studies of aromatic amino acids and pyrimidine derivitives together with some substituted purine derivitives are presented, and the results are discussed in relation to the present knowledge about radical formation in these classes of compounds. Single crystal studies of some sulfur-containing aromatic compounds have been presented with the purpose of shedding light on the electronic structure of sulfur-centred radicals. (JIW)

  18. Radiation processing with the Messina electron linac

    Auditore, L.; Barna, R.C.; De Pasquale, D.; Emanuele, U.; Loria, D.; Morgana, E.; Trifiro, A.; Trimarchi, M.

    2008-01-01

    In the last decades radiation processing has been more and more applied in several fields of industrial treatments and scientific research as a safe, reliable and economic technique. In order to improve existing industrial techniques and to develop new applications of this technology, at the Physics Department of Messina University a high power 5 MeV electron linac has been studied and set-up. The main features of the accelerating structure will be described together with the distinctive features of the delivered beam and several results obtained by electron beam irradiations, such as improvement of the characteristics of polymers and polymer composite materials, synthesis of new hydrogels for pharmaceutical and biomedical applications, reclaim of culture ground, sterilization of medical devices, development of new dosimeters for very high doses and dose rates required for monitoring of industrial irradiations

  19. Electron beams in radiation therapy

    Bruinvis, I.A.D.

    1987-01-01

    Clinical electron beams in interaction with beam flattening and collimating devices are studied, in order to obtain the means for adequate electron therapy. A treatment planning method for arbitrary field shapes is developed that takes the properties of the collimated electron beams into account. An electron multiple-scattering model is extended to incorporate a model for the loss of electrons with depth, in order to improve electron beam dose planning. A study of ionisation measurements in two different phantom materials yields correction factors for electron beam dosimetry. (Auth.)

  20. Radiation Dose from Reentrant Electrons

    Badhwar, G.D.; Cleghorn, T. E.; Watts, J.

    2003-01-01

    In estimating the crew exposures during an EVA, the contribution of reentrant electrons has always been neglected. Although the flux of these electrons is small compared to the flux of trapped electrons, their energy spectrum extends to several GeV compared to about 7 MeV for trapped electrons. This is also true of splash electrons. Using the measured reentrant electron energy spectra, it is shown that the dose contribution of these electrons to the blood forming organs (BFO) is more than 10 times greater than that from the trapped electrons. The calculations also show that the dose-depth response is a very slowly changing function of depth, and thus adding reasonable amounts of additional shielding would not significantly lower the dose to BFO.

  1. Radiation from systems with relativistic electrons

    Ternov, I.M.; Khalilov, V.R.; Bagrov, V.G.; Nikitin, M.M.

    1980-01-01

    Different methods of generation of electromagnetic radiation in the course of electron motion in external electromagnetic fields are considered. Singularities of ''free electron lasers'' (FEL), synchrotronous, ondulator and Compton radiation sources are discussed. The effect of induced radiation of electrons moving in a magnetic field is studied on the basis of the quantum theory methods. The results obtained are compared with the results of the classical theory. The theoretical and experimental results of the main singularities of the ondulator radiation (OR) are presented. It is shown that when the recoil effects are negligible and nonequidistancy of the energy spectrum of an electron in a magnetic field is of an error character, the results for the dose rate calculated by the quantum and classical theory methods completely coincide in the range of great filling numbers. Both in the quantum and classical theories the effects of the induced radiation of electrons moving in external electromagnetic fields (nonstationary in a general case) of a rather general type depend on two main mechanisms, which are nonequidistancy of the energy spectrum and the recoil effect (the quantum theory); appearance of phase and longitudinal electron bunching under the effect of an alternating radiation field (the classical theory). On the basis of the investigations the conclusion is made that OR can be successfully used for measuring the charged particle beam parameters (dispersion of angular spread and the absolute energy), as well as for measuring the amplitude of the magnetic field intensity in a space-periodic system

  2. Reproducing the observed energy-dependent structure of Earth's electron radiation belts during storm recovery with an event-specific diffusion model

    Ripoll, J.-F.; Reeves, G. D.; Cunningham, G. S.; Loridan, V.; Denton, M.; Santolík, Ondřej; Kurth, W. S.; Kletzing, C. A.; Turner, D. L.; Henderson, M. G.; Ukhorskiy, A. Y.

    2016-01-01

    Roč. 43, č. 11 (2016), s. 5616-5625 ISSN 0094-8276 R&D Projects: GA MŠk(CZ) LH15304 Institutional support: RVO:68378289 Keywords : radiation belts * slot region * electron losses * wave particle interactions * hiss wave s * electron lifetimes Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 4.253, year: 2016 http://onlinelibrary.wiley.com/doi/10.1002/2016GL068869/full

  3. Electronic structure in Nd2-xCexCuO4 and Pr2-xCexCuO4 studied by two dimensional angular correlation of positron annihilation radiations

    Kondo, H.; Kubota, T.; Nakashima, H.; Tanigawa, S.; Hidaka, Y.

    1992-01-01

    The electronic structure in Nd 2-x Ce x CuO 4 and Pr 2-x Ce x CuO 4 , which are high-Tc-superconducting materials, was studied by two dimensional angular correlation of positron annihilation radiations (2D-ACAR). The 2D-ACAR measurements were carried out for the samples with and without the doping in the region of the normal conducting states. The three dimensional momentum density has been reconstructed by the image reconstruction technique based on a direct Fourier transformation. The electron momentum density has been reduced into that in the reduced zone scheme by using the LCW folding procedure. The reduced electron momentum density distributions are almost flat, so the electronic structure seem to be regarded as that in semiconductor or insulator. The differences in the density distributions between with and without the doping were observed. These are thought to represent the change of the electronic structure

  4. Status of Galileo interim radiation electron model

    Garrett, H. B.; Jun, I.; Ratliff, J. M.; Evans, R. W.; Clough, G. A.; McEntire, R. W.

    2003-01-01

    Measurements of the high energy, omni-directional electron environment by the Galileo spacecraft Energetic Particle Detector (EDP) were used to develop a new model of Jupiter's trapped electron radiation in the jovian equatorial plane for the range 8 to 16 Jupiter radii.

  5. Radiation dose effects, hardening of electronic components

    Dupont-Nivet, E.

    1991-01-01

    This course reviews the mechanism of interaction between ionizing radiation and a silicon oxide type dielectric, in particular the effect of electron-hole pairs creation in the material. Then effects of cumulated dose on electronic components and especially in MOS technology are examined. Finally methods hardening of these components are exposed. 93 refs

  6. Electronic structure of superlattices

    Altarelli, M.

    1987-01-01

    Calculations of electronic states in semiconductor superlattices are briefly reviewed, with emphasis on the envelope-function method and on comparison with experiments. The energy levels in presence of external magnetic fields are discussed and compared to magneto-optical experiments. (author) [pt

  7. Electronic structure of alloys

    Ehrenreich, H.; Schwartz, L.M.

    1976-01-01

    The description of electronic properties of binary substitutional alloys within the single particle approximation is reviewed. Emphasis is placed on a didactic exposition of the equilibrium properties of the transport and magnetic properties of such alloys. Topics covered include: multiple scattering theory; the single band alloy; formal extensions of the theory; the alloy potential; realistic model state densities; the s-d model; and the muffin tin model. 43 figures, 3 tables, 151 references

  8. Radiative shocks with electron thermal conduction

    Borkowski, Kazimierz.

    1988-01-01

    The authors studies the influence of electron thermal conduction on radiative shock structure for both one- and two-temperature plasmas. The dimensionless ratio of the conductive length to the cooling length determines whether or not conduction is important, and shock jump conditions with conduction are established for a collisionless shock front. He obtains approximate solutions with the assumptions that the ionization state of the gas is constant and the cooling rate is a function of temperature alone. In the absence of magnetic fields, these solutions indicate that conduction noticeably influences normal-abundance interstellar shocks with velocities 50-100 km s -1 and dramatically affects metal-dominated shocks over a wide range of shock velocities. Magnetic fields inhibit conduction, but the conductive energy flux and the corresponding decrease in the post-shock electron temperature may still be appreciable. He calculates detailed steady-state radiative shock models in gas composed entirely of oxygen, with the purpose of explaining observations of fast-moving knots in Cas A and other oxygen-rich supernova remnants (SNRs). The O III ion, whose forbidden emission usually dominates the observed spectra, is present over a wide range of shock velocities, from 100 to 170 kms -1 . All models with conduction have extensive warm photoionization zones, which provides better agreement with observed optical (O I) line strengths. However, the temperatures in these zones could be lowered by (Si II) 34.8 μm and (Ne II) 12.8 μm cooling if Si and Ne are present in appreciable abundance relative to O. Such low temperatures would be inconsistent with the observed (O I) emission in oxygen-rich SNRs

  9. Radiative cooling of relativistic electron beams

    Huang, Zhirong [Stanford Univ., CA (United States)

    1998-05-01

    Modern high-energy particle accelerators and synchrotron light sources demand smaller and smaller beam emittances in order to achieve higher luminosity or better brightness. For light particles such as electrons and positrons, radiation damping is a natural and effective way to obtain low emittance beams. However, the quantum aspect of radiation introduces random noise into the damped beams, yielding equilibrium emittances which depend upon the design of a specific machine. In this dissertation, the author attempts to make a complete analysis of the process of radiation damping and quantum excitation in various accelerator systems, such as bending magnets, focusing channels and laser fields. Because radiation is formed over a finite time and emitted in quanta of discrete energies, he invokes the quantum mechanical approach whenever the quasiclassical picture of radiation is insufficient. He shows that radiation damping in a focusing system is fundamentally different from that in a bending system. Quantum excitation to the transverse dimensions is absent in a straight, continuous focusing channel, and is exponentially suppressed in a focusing-dominated ring. Thus, the transverse normalized emittances in such systems can in principle be damped to the Compton wavelength of the electron, limited only by the Heisenberg uncertainty principle. In addition, he investigates methods of rapid damping such as radiative laser cooling. He proposes a laser-electron storage ring (LESR) where the electron beam in a compact storage ring repetitively interacts with an intense laser pulse stored in an optical resonator. The laser-electron interaction gives rise to rapid cooling of electron beams and can be used to overcome the space charge effects encountered in a medium energy circular machine. Applications to the designs of low emittance damping rings and compact x-ray sources are also explored.

  10. Radiative cooling of relativistic electron beams

    Huang, Z.

    1998-05-01

    Modern high-energy particle accelerators and synchrotron light sources demand smaller and smaller beam emittances in order to achieve higher luminosity or better brightness. For light particles such as electrons and positrons, radiation damping is a natural and effective way to obtain low emittance beams. However, the quantum aspect of radiation introduces random noise into the damped beams, yielding equilibrium emittances which depend upon the design of a specific machine. In this dissertation, the author attempts to make a complete analysis of the process of radiation damping and quantum excitation in various accelerator systems, such as bending magnets, focusing channels and laser fields. Because radiation is formed over a finite time and emitted in quanta of discrete energies, he invokes the quantum mechanical approach whenever the quasiclassical picture of radiation is insufficient. He shows that radiation damping in a focusing system is fundamentally different from that in a bending system. Quantum excitation to the transverse dimensions is absent in a straight, continuous focusing channel, and is exponentially suppressed in a focusing-dominated ring. Thus, the transverse normalized emittances in such systems can in principle be damped to the Compton wavelength of the electron, limited only by the Heisenberg uncertainty principle. In addition, he investigates methods of rapid damping such as radiative laser cooling. He proposes a laser-electron storage ring (LESR) where the electron beam in a compact storage ring repetitively interacts with an intense laser pulse stored in an optical resonator. The laser-electron interaction gives rise to rapid cooling of electron beams and can be used to overcome the space charge effects encountered in a medium energy circular machine. Applications to the designs of low emittance damping rings and compact x-ray sources are also explored

  11. Investigations of structure, bonding, and reactions of radiation-induced free radicals in the solid state using electron spin resonance spectroscopy

    Hudson, R.L.

    1978-01-01

    Electron spin resonance spectroscopy (ESR) has been used to study the structure, bonding, and reactions of several types of free radicals produced by γ irradiation of solids at 77K. Well-defined spectral patterns and the use of photolysis and annealing treatments assisted the analyses and interpretations. The radical anion BF 3 - was generated and identified unequivocally in a matrix of tetramethylsilane at 77K. Both the ESR data and theoretical calculations support a pyramidal structure with a bond angle of about 110 0 . The present experiments showed that BF 3 - has ESR parameters consistent with those of the isoelectronic radicals CF 3 , NF 3 + , and F 2 NO. γ irradiation of polycrystalline trimethyl borate at 77K gave an ESR spectrum which was assigned to the dimer radical anion [(MeO) 3 B.B(OMe) 3 ] - . Radical anions of dialkyl carbonates were observed for the first time and found to undergo a β-scission reaction to produce alkyl radicals. This free radical reaction is unusual in that it proceeds both thermally and photochemically. For the dimethyl carbonate radical anion, 13 C parameters were obtained from a 13 C enriched sample. The photolysis of trapped radicals in γ irradiated carboxylic esters, RC(O)OR', was studied by ESR spectroscopy and two different reactions were characterized. Two hypervalent silicon radical anions were prepared and examined in SI(OCH 3 ) 4 . The results of the present work thus represent the first complete sets of data on the silicon 3s and 3p spin densities for such species. The first PL 3 - radical anion was prepared by the γ irradiation of crystalline trimethylphosphite, and identified through its photolysis reactions and from the results of radiation chemical experiments

  12. Electronics for Piezoelectric Smart Structures

    Warkentin, D. J.; Tani, J.

    1997-01-01

    This paper briefly presents work addressing some of the basic considerations for the electronic components used in smart structures incorporating piezoelectric elements. After general remarks on the application of piezoelectric elements to the problem of structural vibration control, three main topics are described. Work to date on the development of techniques for embedding electronic components within structural parts is presented, followed by a description of the power flow and dissipation requirements of those components. Finally current work on the development of electronic circuits for use in an 'active wall' for acoustic noise is introduced.

  13. Atomic and electronic structures of novel silicon surface structures

    Terry, J.H. Jr.

    1997-03-01

    The modification of silicon surfaces is presently of great interest to the semiconductor device community. Three distinct areas are the subject of inquiry: first, modification of the silicon electronic structure; second, passivation of the silicon surface; and third, functionalization of the silicon surface. It is believed that surface modification of these types will lead to useful electronic devices by pairing these modified surfaces with traditional silicon device technology. Therefore, silicon wafers with modified electronic structure (light-emitting porous silicon), passivated surfaces (H-Si(111), Cl-Si(111), Alkyl-Si(111)), and functionalized surfaces (Alkyl-Si(111)) have been studied in order to determine the fundamental properties of surface geometry and electronic structure using synchrotron radiation-based techniques.

  14. Electronic Structure of Eu6C60

    WANG Xiao-Xiong; LI Hong-Nian; XU Ya-Bo; WANG Peng; ZHANG Wen-Hua; XU Fa-Qiang

    2009-01-01

    We study the valence band of Eu-intercalated C60 by synchrotron radiation photoelectron spectroscopy to un-derstand the ferromagnetism (FM) and the giant magnetoresistance (GMR) of Eu6C60. The results reveal the semiconducting property and the remarkable 5d6s-π hybridization. Eu-C60 bonding has both ionic and covalent contributions. No more than half the 5d6s electrons transfer from Eu to the LUMO derived band of C60, and the LUMO+1 derived band is not filled. The remaining valence electrons of Eu, together with some π (LUMO, HOMO and HOMO-1) electrons, constitute the covalent bond. The electronic structure implies that the magnetic coupling in Eu6C60 should be through the intra-atomic f-sd exchange and the medium of the π electrons. The possibility of the GMR being tunnelling magnetoresistance is ruled out.

  15. Coupled electron-photon radiation transport

    Lorence, L.; Kensek, R.P.; Valdez, G.D.; Drumm, C.R.; Fan, W.C.; Powell, J.L.

    2000-01-01

    Massively-parallel computers allow detailed 3D radiation transport simulations to be performed to analyze the response of complex systems to radiation. This has been recently been demonstrated with the coupled electron-photon Monte Carlo code, ITS. To enable such calculations, the combinatorial geometry capability of ITS was improved. For greater geometrical flexibility, a version of ITS is under development that can track particles in CAD geometries. Deterministic radiation transport codes that utilize an unstructured spatial mesh are also being devised. For electron transport, the authors are investigating second-order forms of the transport equations which, when discretized, yield symmetric positive definite matrices. A novel parallelization strategy, simultaneously solving for spatial and angular unknowns, has been applied to the even- and odd-parity forms of the transport equation on a 2D unstructured spatial mesh. Another second-order form, the self-adjoint angular flux transport equation, also shows promise for electron transport

  16. Electron collision cross sections and radiation chemistry

    Hatano, Y.

    1983-01-01

    A survey is given of the cross section data needs in radiation chemistry, and of the recent progress in electron impact studies on dissociative excitation of molecules. In the former some of the important target species, processes, and collision energies are presented, while in the latter it is demonstrated that radiation chemistry is a source of new ideas and information in atomic collision research. 37 references, 4 figures

  17. Nonrelativistic electron bunch train for coherently enhanced terahertz radiation sources

    Li Yuelin; Kim, Kwang-Je

    2008-01-01

    We propose to generate a train of prebunched electron beams for producing coherently enhanced Smith-Purcell radiation [S. J. Smith and E. M. Purcell, Phys. Rev. 92, 1069 (1953)] in the terahertz wavelength range. In this scheme, a train of picosecond laser pulses is produced to drive a photoemission gun to generate a train of 50 keV electron pulses. The parameters are chosen so that the space-charge effect does not destroy the pulse time structure. Smith-Purcell radiation from the electron pulse train is enhanced due both to the short length of the individual electron bunch and to the repetitive structure of the beam. Example systems producing coherent terahertz power at about 1 mW are described

  18. Synchrotron radiation and structural proteomics

    Pechkova, Eugenia

    2011-01-01

    This book presents an overview of the current state of research in both synchrotron radiation and structural proteomics from different laboratories worldwide. The book presents recent research results in the most advanced methods of synchrotron radiation analysis, protein micro- and nano crystallography, X-ray scattering and X-ray optics, coherent X-Ray diffraction, and laser cutting and contactless sample manipulation are described in details. The book focuses on biological applications and highlights important aspects such as radiation damage and molecular modeling.

  19. Electron microscopy - principles of radiation protection

    1990-01-01

    This 8 minute programme explains the nature of the possible radiation hazard in Electron Microscopy and outlines the ways in which modern equipment is designed and made so that in normal use the worker is not exposed to radiation. The interlock principle is explained and illustrated by an example from the field of X-ray crystallography. By filming machines while they were dismantled for servicing, details of several internal safety devices have been included. In this way workers who normally use the equipment as a 'black box' get some insight into the principles and practice of radiation protection in the field. (author)

  20. Radiation-induced electron migration along DNA

    Fuciarelli, A.F.; Sisk, E.C.; Miller, J.H.; Zimbrick, J.D.

    1994-04-01

    Radiation-induced electron migration along DNA is a mechanism by which randomly produced stochastic energy deposition events can lead to nonrandom types of damage along DNA manifested distal to the sites of the initial energy deposition. Electron migration along DNA is significantly influenced by the DNA base sequence and DNA conformation. Migration along 7 base pairs in oligonucleotides containing guanine bases was observed for oligonucleotides irradiated in solution which compares to average migration distances of 6 to 10 bases for Escherichia coli DNA irradiated in solution and 5.5 base pairs for Escherichia coli DNA irradiated in cells. Evidence also suggests that electron migration can occur preferentially in the 5' to 3' direction along DNA. Our continued efforts will provide information regarding the contribution of electron transfer along DNA to formation of locally multiply damaged sites created in DNA by exposure to ionizing radiation

  1. Radiation swelling of steels with lath martensite-austenic structure

    Sagaradze, V.V.; Pavlov, V.A.; Alyab'ev, V.M.; Lapin, S.S.; Ermishkin, V.A.; Antonova, O.V.

    1987-01-01

    Influence of electron radiation in the column of the JEM-1000 electron microscope on radiation swelling of austenite as austenitic fields and thin plates surrounded by α-martensite crystals is investigated. Formation of lath structure of alternating dispersive plates of martensite and invert austenite formed as a result of partial inverse martensite transformation α→γ is shown to restrain radiation swelling and formation of vacancy voids in stainless steels

  2. Electron Radiation Belts of the Solar System

    Mauk, Barry; Fox, Nicola

    To address the question of what factors dictate similarities and differences between radiation belts, we present comparisons between the electron radiation belt spectra of all five strongly magnetized planets within the solar system: Earth, Jupiter, Saturn, Uranus, and Neptune. We choose the highest intensity observed electron spectrum within each system (highest specifically near 1 MeV) and compare them against expectations based on the so-called Kennel-Petschek limit (KP; 1966) for each system. For evaluating the KP limit, we begin with the new relativis-tically correct formulation of Summers et al. (2009) but then add several refinements of our own. Specifically, we: 1) utilized a much more flexible analytic spectral shape that allows us to accurately fit observed radiation belt spectra; 2) adopt the point of view that the anisotropy parameter is not a free parameter but must take on a minimal value, as originally proposed by Kennel and Petschek (1966); and 3) examine the differential characteristics of the KP limit along the lines of what Schulz and Davidson (1988) performed for the non-relativistic formula-tion. We find that three factors limit the highest electron radiation belt intensities within solar system planetary magnetospheres: a) whistler mode interactions that limit spectral intensities to a differential Kennel-Petschek limit (3 planets); b) the absence of robust acceleration pro-cesses associated with injection dynamics (1 planet); and c) material interactions between the radiation particles and clouds of gas and dust (1 planet).

  3. Gamma and electron radiation effects on straw

    Leonhardt, J.W.; Baer, M.; Huebner, G.

    1983-01-01

    Gamma and electron radiation effects on wheat straw, oat straw, barley straw and rye straw are reported. In vitro and in vivo studies show that the digestibility of these agricultural rough materials can be increased up to 80% and more at high doses. The increase of the digestibility is connected with a depolymerisation of cellulose and hemicellulose. (author)

  4. The effects of radiation on electronic systems

    Messenger, G.C.; Ash, M.S.

    1986-01-01

    This book is the first unified treatment of the analysis and design methods for protection of principally electronic systems from the deleterious effects of nuclear and electro-magnetic radiation. Coverage spans from a detailed description of the nuclear radiation sources to pertinent semiconductor physics, then to hardness assurance. This work combines the disciplines of solid state physics, semiconductor physics, circuit engineering, nuclear physics, together with electronics and electromagnetic theory into a book that can be used as a text with problems at the end of the majority of the chapters. Written by veterans in the field, the most significant feature of this book is its comprehensive treatment of the phenomena involved. This treatment includes the analysis and design of the effect of nuclear radiation on electronic systems from the experimental, theoretical, and engineering viewpoints. Unique pedagogical attempts are employed to make the material more understandable from the position of an enlightened engineering and scientific readership whose task is the design and analysis of radiation hardened electronic systems

  5. Electronic structure of silicon superlattices

    Krishnamurthy, S.; Moriarty, J.A.

    1984-01-01

    Utilizing a new complex-band-structure technique, the electronic structure of model Si-Si/sub 1-x/Ge/sub x/ and MOS superlattices has been obtained over a wide range of layer thickness d (11 less than or equal to d less than or equal to 110 A). For d greater than or equal to 44 A, it is found that these systems exhibit a direct fundamental band gap. Further calculations of band-edge effective masses and impurity scattering rates suggest the possibility of a band-structure-driven enhancement in electron mobility over bulk silicon

  6. Atomic electron spectrometry with synchrotron radiation

    Sorensen, S.L.

    1989-01-01

    Techniques of atomic electron spectrometry were applied to atoms in the gaseous and solid states to derive information about fundamental atomic properties. A new method was developed to measure Coster-Kronig yields in metals by photoionization with synchrotron radiation. Photon-energy sensitive Si L-VV Auger satellites were investigated via electron spectrometry. The krypton 1s photoionization spectrum was measured in an experiment which was motivated by the need to understand the krypton 1s satellite spectrum for calibration of an experiment to measure the mass of the electron antineutrino

  7. Electron dynamics with radiation and nonlinear wigglers

    Jowett, J.M.

    1986-06-01

    The physics of electron motion in storage rings is described by supplementing the Hamiltonian equations of motion with fluctuating radiation reaction forces to describe the effects of synchrotron radiation. This leads to a description of radiation damping and quantum diffusion in single-particle phase-space by means of Fokker-Planck equations. For practical purposes, most storage rings remain in the regime of linear damping and diffusion; this is discussed in some detail with examples, concentrating on longitudinal phase space. However special devices such as nonlinear wigglers may permit the new generation of very large rings to go beyond this into regimes of nonlinear damping. It is shown how a special combined-function wiggler can be used to modify the energy distribution and current profile of electron bunches

  8. Radiation processing of carrageenan using electron beam

    Abad, L.V.; Aranilla, C.T.; Relleve, L.; Dela Rosa, A.M.

    2005-01-01

    Electron beam accelerator has been widely employed in the modification of natural polymers for the development of materials used in biomedical and agricultural applications. The carrageenans are among these materials that show a vast potential for these types of applications. Previous studies at the Philippine Nuclear Research Institute focused on the utilization of gamma radiation to modify the carrageenans. Radiation degradation of carrageenan found valuable use as plant growth promoter. Hydrogels for burn dressing using blends of carrageenan and synthetic polymers have also been made using gamma radiation. While previous studies have been focused on the use of gamma radiation to modify the carrageenans, recent studies expanded the technology to electron beam. Concretely, researches are along the following two areas: a) Degradation studies of aqueous carrageenan using the LEEB and b) Preparation of blend polysaccharide derivatives such as carboxymethylcellulose (CMC), and hydroxypropylcellulose (HPC) with kappa-carrageenan (KC) by EB radiation. These works were done at the Takasaki Radiation Chemistry Research Establishment (TRCRE) by two PNRI colleagues under the nuclear researcher exchange program of the Japan Ministry of Education, Culture, Sports, Science and Technology (MEXT). The first area had already been reported and discussed in the last project meeting held in Malaysia. (author)

  9. Classical electromagnetic radiation of the Dirac electron

    Lanyi, G.

    1973-01-01

    A wave-function-dependent four-vector potential is added to the Dirac equation in order to achieve conservation of energy and momentum for a Dirac electron and its emitted electromagnetic field. The resultant equation contains solutions which describe transitions between different energy states of the electron. As a consequence it is possible to follow the space-time evolution of such a process. This evolution is shown in the case of the spontaneous emission of an electromagnetic field by an electron bound in a hydrogen-like atom. The intensity of the radiation and the spectral distribution are calculated for transitions between two eigenstates. The theory gives a self-consistent deterministic description of some simple radiation processes without using quantum electrodynamics or the correspondence principle.

  10. Radiative electron capture by channeled ions

    Pitarke, J.M.; Ritchie, R.H.; Tennessee Univ., Knoxville, TN

    1989-01-01

    Considerable experimental data have been accumulated relative to the emission of photons accompanying electron capture by swift, highly stripped atoms penetrating crystalline matter under channeling conditions. Recent data suggest that the photon energies may be less than that expected from simple considerations of transitions from the valence band of the solid to hydrogenic states on the moving ion. We have studied theoretically the impact parameter dependence of the radiative electron capture (REC) process, the effect of the ion's wake and the effect of capture from inner shells of the solid on the photon emission probability, using a statistical approach. Numerical comparisons of our results with experiment are made. 13 refs., 6 figs

  11. Electronic structure and correlation effects in actinides

    Albers, R.C.

    1998-01-01

    This report consists of the vugraphs given at a conference on electronic structure. Topics discussed are electronic structure, f-bonding, crystal structure, and crystal structure stability of the actinides and how they are inter-related

  12. Ballistic transport and electronic structure

    Schep, Kees M.; Kelly, Paul J.; Bauer, Gerrit E.W.

    1998-01-01

    The role of the electronic structure in determining the transport properties of ballistic point contacts is studied. The conductance in the ballistic regime is related to simple geometrical projections of the Fermi surface. The essential physics is first clarified for simple models. For real

  13. The Electronic Structure of Calcium

    Jan, J.-P.; Skriver, Hans Lomholt

    1981-01-01

    The electronic structure of calcium under pressure is re-examined by means of self-consistent energy band calculations based on the local density approximation and using the linear muffin-tin orbitals (LMTO) method with corrections to the atomic sphere approximation included. At zero pressure...

  14. Electronic structure of metal clusters

    Wertheim, G.K.

    1989-01-01

    Photoemission spectra of valence electrons in metal clusters, together with threshold ionization potential measurements, provide a coherent picture of the development of the electronic structure from the isolated atom to the large metallic cluster. An insulator-metal transition occurs at an intermediate cluster size, which serves to define the boundary between small and large clusters. Although the outer electrons may be delocalized over the entire cluster, a small cluster remains insulating until the density of states near the Fermi level exceeds 1/kT. In large clusters, with increasing cluster size, the band structure approaches that of the bulk metal. However, the bands remain significantly narrowed even in a 1000-atom cluster, giving an indication of the importance of long-range order. The core-electron binding-energy shifts of supported metal clusters depend on changes in the band structure in the initial state, as well as on various final-state effects, including changes in core hole screening and the coulomb energy of the final-state charge. For cluster supported on amorphous carbon, this macroscopic coulomb shift is often dominant, as evidenced by the parallel shifts of the core-electron binding energy and the Fermi edge. Auger data confirm that final-state effects dominate in cluster of Sn and some other metals. Surface atom core-level shifts provide a valuable guide to the contributions of initial-state changes in band structure to cluster core-electron binding energy shifts, especially for Au and Pt. The available data indicate that the shift observed in supported, metallic clusters arise largely from the charge left on the cluster by photoemission. As the metal-insulator transition is approached from above, metallic screening is suppressed and the shift is determined by the local environment. (orig.)

  15. The Near-Earth Space Radiation for Electronics Environment

    Stassinopoulos, E. G.; LaBel, K. A.

    2004-01-01

    The earth's space radiation environment is described in terms of: a) charged particles as relevant to effects on spacecraft electronics, b) the nature and distribution of trapped and transiting radiation, and c) their effect on electronic components.

  16. Obwervation of 10 μm Smith-Purcell radiation from 45 MeV electrons

    Fernow, R.C.; Robertson, S.H.; Brownell, J.H.; Walsh, J.E.

    1997-01-01

    Using the high-brightness, high-energy electron beam at the Brookhaven Accelerator Test Facility we observe forward directed Smith-Purcell radiation in the mid-infrared spectral regime. This radiation can prove useful as a source of infrared radiation for other scientific studies as well as a providing a precursor investigation of the inverse process, namely the acceleration of electrons by means of the coupling of laser light with electrons via micro-structures

  17. Electronic radiative capture in solid targets

    Pregliasco, R.; Nemirovsky, I.; Suarez, S.

    1988-01-01

    X-ray spectra originating from electron radiative capture from aluminium target to K shell on F 9+ and F 8+ beams with 115MeV are studied. Using an electrostatic analyzer, it was obtained the charge fractions Fi to aluminiun thicknesses of 39 and 58 micrograms/cm 2 . These thicknesses are determined by the stopping power of alpha particles. (A.C.A.S.) [pt

  18. Radiation to Electronics: Reality or Fata Morgana?

    Brugger, M; Calviani, M; Ferrari, A; Kramer, D; Losito, R; Roeed, K; Roesler, S; Spiezia, G; Thornton, A; Thurel, Y

    2011-01-01

    A first year of successful LHC operation has passed reaching about 50pb-1 of integrated luminosity (1‰ of nominal, 5% of 1fb-1) and more than 1% of peak luminosity, as well as a successful ion run. It is thus time having a first look on the observed radiation levels around LHC critical areas and to compare them to available simulation results. In spite of the still very low integrated intensities and cumulative luminosities, this paper summarizes the failure rate predictions by evaluating the observed radiation levels and early electronics failures, as well as the additional results from 2010 CNRAD radiation tests. Upcoming possibly in early 2011, electron cloud and scrubbing issues and their impact on radiation levels are also briefly discussed. Based on this, updated predictions for 2011 operation and beyond will be deduced, on the base of the envisaged LHC intensity, energy and luminosity reach. Starting from these estimates, priorities for short-term improvements and beam tests are presented, as well as...

  19. Electronic structure of Mo and W investigated with positron annihilation

    Dutschke, Markus [Theoretical Physics III, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg (Germany); Sekania, Michael [Theoretical Physics III, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg (Germany); Andronikashvili Institute of Physics, Tbilisi (Georgia); Benea, Diana [Faculty of Physics, Babes-Bolyai University, Cluj-Napoca (Romania); Department of Chemistry, Ludwig Maximilian University of Munich (Germany); Ceeh, Hubert; Weber, Joseph A.; Hugenschmidt, Christoph [FRM II, Technische Universitaet Muenchen, Garching (Germany); Chioncel, Liviu [Theoretical Physics III, Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg (Germany); Augsburg Center for Innovative Technologies, University of Augsburg (Germany)

    2016-07-01

    We perform electronic structure calculations to analyze the momentum distribution of the transition metals molybdenum and tungsten. We study the influence of positron-electron and the electron-electron interactions on the shape of the two-dimensional angular correlation of positron annihilation radiation (2D-ACAR) spectra. Our analysis is performed within the framework of the combined Density Functional (DFT) and Dynamical Mean-Field Theory (DMFT). Computed spectra are compared with recent experimental investigations.

  20. Photoelectron spectroscopy bulk and surface electronic structures

    Suga, Shigemasa

    2014-01-01

    Photoelectron spectroscopy is now becoming more and more required to investigate electronic structures of various solid materials in the bulk, on surfaces as well as at buried interfaces. The energy resolution was much improved in the last decade down to 1 meV in the low photon energy region. Now this technique is available from a few eV up to 10 keV by use of lasers, electron cyclotron resonance lamps in addition to synchrotron radiation and X-ray tubes. High resolution angle resolved photoelectron spectroscopy (ARPES) is now widely applied to band mapping of materials. It attracts a wide attention from both fundamental science and material engineering. Studies of the dynamics of excited states are feasible by time of flight spectroscopy with fully utilizing the pulse structures of synchrotron radiation as well as lasers including the free electron lasers (FEL). Spin resolved studies also made dramatic progress by using higher efficiency spin detectors and two dimensional spin detectors. Polarization depend...

  1. Cerenkov Radiator Driven by a Superconducting RF Electron Gun

    Poole, B.R.; Harris, J.R.

    2011-01-01

    The Naval Postgraduate School (NPS), Niowave, Inc., and Boeing have recently demonstrated operation of the first superconducting RF electron gun based on a quarter wave resonator structure. In preliminary tests, this gun has produced 10 ps long bunches with charge in excess of 78 pC, and with beam energy up to 396 keV. Initial testing occurred at Niowave's Lansing, MI facility, but the gun and diagnostic beam line are planned for installation in California in the near future. The design of the diagnostic beam line is conducive to the addition of a Cerenkov radiator without interfering with other beam line operations. Design and simulations of a Cerenkov radiator, consisting of a dielectric lined waveguide will be presented. The dispersion relation for the structure is determined and the beam interaction is studied using numerical simulations. The characteristics of the microwave radiation produced in both the short and long bunch regimes will be presented.

  2. Schemes of Superradiant Emission from Electron Beams and "Spin-Flip Emission of Radiation"

    Gover, A

    2005-01-01

    A unified analysis for Superradiant emission from bunched electron beams in various kinds of radiation scheme is presented. Radiation schemes that can be described by the formulation include Pre-bunched FEL (PB-FEL), Coherent Synchrotron Radiation (CSR), Smith-Purcell Radiation, Cerenkov-Radiation, Transition-Radiation and more. The theory is based on mode excitation formulation - either discrete or continuous (the latter - in open structures). The discrete mode formulation permits simple evaluation of the spatially coherent power and spectral power of the source. These figures of merit of the radiation source are useful for characterizing and comparing the performance of different radiation schemes. When the bunched electron beam emits superradiantly, these parameters scale like the square of the number of electrons, orders of magnitude more than spontaneous emission. The formulation applies to emission from single electron bunches, periodically bunched beams, or emission from a finite number of bunches in a...

  3. Radiation shielding structure for concrete structure

    Oya, Hiroshi

    1998-01-01

    Crack inducing members for inducing cracks in a predetermined manner are buried in a concrete structure. Namely, a crack-inducing member comprises integrally a shielding plate and extended plates situated at the center of a wall and inducing plates vertically disposed to the boundary portion between them with the inducing plates being disposed each in a direction perforating the wall. There are disposed integrally a pair of the inducing plate spaced at a predetermined horizontal distance on both sides of the shielding plate so as to form a substantially crank-shaped cross section and extended plates formed in the extending direction of the shielding plate, and the inducing plates are disposed each in a direction perforating the wall. Then, cracks generated when stresses are exerted can be controlled, and generation of cracks passing through the concrete structure can be prevented reliably. The reliability of a radiation shielding effect can be enhanced remarkably. (N.H.)

  4. Radiation damage of structural materials

    Koutsky, Jaroslav

    1994-01-01

    Maintaining the integrity of nuclear power plants is critical in the prevention or control of severe accidents. This monograph deals with both basic groups of structural materials used in the design of light-water nuclear reactors, making the primary safety barriers of NPPs. Emphasis is placed on materials used in VVER-type nuclear reactors: Cr-Mo-V and Cr-Ni-Mo-V steel for RPV and Zr-Nb alloys for fuel element cladding. The book is divided into 7 main chapters, with the exception of the opening one and the chapter providing a phenomenological background for the subject of radiation damage. Ch

  5. Electronic structure of lanthanide scandates

    Mizzi, Christopher A.; Koirala, Pratik; Marks, Laurence D.

    2018-02-01

    X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and density functional theory calculations were used to study the electronic structure of three lanthanide scandates: GdSc O3,TbSc O3 , and DySc O3 . X-ray photoelectron spectra simulated from first-principles calculations using a combination of on-site hybrid and GGA +U methods were found to be in good agreement with experimental x-ray photoelectron spectra. The hybrid method was used to model the ground state electronic structure and the GGA +U method accounted for the shift of valence state energies due to photoelectron emission via a Slater-Janak transition state approach. From these results, the lanthanide scandate valence bands were determined to be composed of Ln 4 f ,O 2 p , and Sc 3 d states, in agreement with previous work. However, contrary to previous work the minority Ln 4 f states were found to be located closer to, and in some cases at, the valence band maximum. This suggests that minority Ln 4 f electrons may play a larger role in lanthanide scandate properties than previously thought.

  6. Galactic structure and gamma radiation

    Casse, Michel; Cesarsky, Catherine; Paul Jacques

    1977-01-01

    A model of spiral structure of the Galaxy is outlined from radiosynchrotron and gamma observations. The most interesting observations in the galactic context, obtained by the SAS II American satellite are concerned with the distribution of the γ photoemission at energies higher than 10 8 eV, along the galactic equator. The model proposed is in quantitative agreement with the present ideas on the spiral structure of the Galaxy, the galactic magnetic field, and the confinement of cosmic rays by the magnetic field and of the magnetic field by matter. Following the American era, the European COS-B satellite opens the European phase towards an identification of the discrete gamma radiation sources [fr

  7. Radiation damage of structural materials

    Koutsky, J.; Kocik, J.

    1994-01-01

    Maintaining the integrity of nuclear power plants (NPP) is critical in the prevention or control of severe accidents. This monograph deals with both basic groups of structural materials used in the design of light-water nuclear reactors, making the primary safety barriers of NPPs. Emphasis is placed on materials used in VVER-type nuclear reactors: Cr-Mo-V and Cr-Ni-Mo-V steel for reactor pressure vessels (RPV) and Zr-Nb alloys for fuel element cladding. The book is divided into seven main chapters, with the exception of the opening one and the chapter providing phenomenological background for the subject of radiation damage. Chapters 3-6 are devoted to RPV steels and chapters 7-9 to zirconium alloys, analyzing their radiation damage structure, changes of mechanical properties due to neutron irradiation as well as factors influencing the degree of their performance degradation. The recovery of damaged materials is also discussed. Considerable attention is paid to a comparison of VVER-type and western-type light-water materials

  8. Electronic cyclotron radiation amplification in thermonuclear plasmas

    Ziebell, L.F.

    1983-01-01

    The amplified emission of electron cyclotron radiation near the fundamental frequency from an inhomogeneous, anisotropic plasma slab is investigated in a linear theory. Plasma polarization effects are consistently included. Expressions are developed in the WKB approximation for emission in the ordinary and the extraordinary modes, for propagation perpendicular to the magnetic field. Numerical results are given for the extraordinary mode, for which effects are strongest. For the case of a loss-cone-type electron momentum distribution, it is shown that the amplification is sensitively dependent on the ratio of parallel-to-perpendicular temperature and on inhomogeneities in the magnetic field. The dependence of the amplification on the distribution is further investigated by considering superpositions of loss-cone and Maxwellian components. It is show that the presence of a Maxwellian component in general reduces the emission relative to the pure loss-cone case, and situations occur in which a layer in the slab very effectively absorbs all the radiation amplified elsewhere. A peculiar behaviour of the refractive index, which occurs in the transition from the pure loss-cone to the pure Maxwellian case, is discussed. (author)

  9. Radiation at planar channeling of relativistic electrons in thick crystals

    Baier, V.N.; Katkov, V.M.; Strakhovenko, V.M.

    1983-01-01

    The distribution kinetics with respect to the transverse energy at electron channeling is discussed. The asymptotic expressions for the radiation intensity into a given collimator at electron channeling in thick crystals are derived. An optimal thickness at which the radiation output is maximal is found. The spectral distribution of the radiation intensity is analysed for the case of a single diamond crystal. (author)

  10. Electron scattering and nuclear structure

    Frois, B.

    1987-01-01

    The search for the appropriate degrees of freedom to describe nuclei is the central focus of nuclear physics today. Therefore the authors explore in this review their current understanding of nuclear structure as defined by electromagnetic data. The precision of the electromagnetic probe allows us to define accurately the limits of present theoretical descriptions. The authors review here a broad range of subjects that have been addressed by recent experiments, from the study of meson exchange currents and single-particle distributions to collective excitations in heavy nuclei. However, they do not discuss elastic magnetic scattering, inelastic excitation of discrete states, or single-nucleon knockout reactions since these reactions were recently reviewed. The principal aim of this review is to offer a fresh perspective on nuclear structure, based on the new generation of electron scattering data presented here and in the above-mentioned articles

  11. Electronic structure of spin systems

    Saha-Dasgupta, Tanusri

    2016-04-15

    Highlights: • We review the theoretical modeling of quantum spin systems. • We apply the Nth order muffin-tin orbital electronic structure method. • The method shows the importance of chemistry in the modeling. • CuTe{sub 2}O{sub 5} showed a 2-dimensional coupled spin dimer behavior. • Ti substituted Zn{sub 2}VO(PO{sub 4}){sub 2} showed spin gap behavior. - Abstract: Low-dimensional quantum spin systems, characterized by their unconventional magnetic properties, have attracted much attention. Synthesis of materials appropriate to various classes within these systems has made this field very attractive and a site of many activities. The experimental results like susceptibility data are fitted with the theoretical model to derive the underlying spin Hamiltonian. However, often such a fitting procedure which requires correct guess of the assumed spin Hamiltonian leads to ambiguity in deciding the representative model. In this review article, we will describe how electronic structure calculation within the framework of Nth order muffin-tin orbital (NMTO) based Wannier function technique can be utilized to identify the underlying spin model for a large number of such compounds. We will show examples from compounds belonging to vanadates and cuprates.

  12. Radiation leakage from linac electron applicator assembly

    Keys, R.A.; Purdy, J.A.

    1984-01-01

    The electron beam applicator system currently in use on the linear accelerator is constructed of light-weight fiberglass and aluminum. With an applicator in place on the accelerator, the photon collimator jaws are automatically set several centimeters greater than the electron field size projected at the patient's surface. To ensure that no regions of high dose levels exist outside the useful beam, ionization and film measurements were made to quantitate the amount of leakage radiation through the 10 cm x 10 cm and 25 cm x 25 cm applicators. In most regions, the ionization levels at the patient's surface were below 5% of the central axis dose. In one area for the 25 cm applicator, the percentage ionization was 8.5%, which could be reduced by the addition of a small piece of 1/8 inch thick lead. However, ionization levels on the outside surface of the applicator were found to be considerably higher at certain locations for the 25 cm applicator. Results for 6, 9, 12 and 20 MeV electrons are reported here

  13. Vacuum electron acceleration by coherent dipole radiation

    Troha, A.L.; Van Meter, J.R.; Landahl, E.C.; Alvis, R.M.; Hartemann, F.V.; Troha, A.L.; Van Meter, J.R.; Landahl, E.C.; Alvis, R.M.; Li, K.; Luhmann, N.C. Jr.; Hartemann, F.V.; Unterberg, Z.A.; Kerman, A.K.

    1999-01-01

    The validity of the concept of laser-driven vacuum acceleration has been questioned, based on an extrapolation of the well-known Lawson-Woodward theorem, which stipulates that plane electromagnetic waves cannot accelerate charged particles in vacuum. To formally demonstrate that electrons can indeed be accelerated in vacuum by focusing or diffracting electromagnetic waves, the interaction between a point charge and coherent dipole radiation is studied in detail. The corresponding four-potential exactly satisfies both Maxwell's equations and the Lorentz gauge condition everywhere, and is analytically tractable. It is found that in the far-field region, where the field distribution closely approximates that of a plane wave, we recover the Lawson-Woodward result, while net acceleration is obtained in the near-field region. The scaling of the energy gain with wave-front curvature and wave amplitude is studied systematically. copyright 1999 The American Physical Society

  14. Transition radiation electron beam diagnostic study at ATF

    Qiu, X.Z.; Wang, X.J.; Batchelor, K.; Ben-Zvi, I.

    1995-01-01

    Recently we have started a program to develop transition radiation based electron beam diagnostics at the Accelerator Test Facility at Brookhaven National Laboratory. In this paper, we will discuss a technique to estimate the lower limit in electron beam divergence measurement with single foil transition radiation and two-foil transition radiation interferometer. Preliminary experimental data from 4.5 MeV electron beam will be presented

  15. Radiation effects on relativistic electrons in strong external fields

    Iqbal, Khalid

    2013-01-01

    The effects of radiation of high energy electron beams are a major issue in almost all types of charged particle accelerators. The objective of this thesis is both the analytical and numerical study of radiation effects. Due to its many applications the study of the self force has become a very active and productive field of research. The main part of this thesis is devoted to the study of radiation effects in laser-based plasma accelerators. Analytical models predict the existence of radiation effects. The investigation of radiation reaction show that in laser-based plasma accelerators, the self force effects lower the energy gain and emittance for moderate energies electron beams and increase the relative energy spread. However, for relatively high energy electron beams, the self radiation and retardation (radiation effects of one electron on the other electron of the system) effects increase the transverse emittance of the beam. The energy gain decreases to even lower value and relative energy spread increases to even higher value due to high radiation losses. The second part of this thesis investigates with radiation reaction in focused laser beams. Radiation effects are very weak even for high energy electrons. The radiation-free acceleration and the simple practical setup make direct acceleration in a focused laser beam very attractive. The results presented in this thesis can be helpful for the optimization of future electron acceleration experiments, in particular in the case of laser-plasma accelerators.

  16. Electron beam radiation effects on recycled polyamide-6

    Evora, Maria Cecilia; Silva, Leonardo G. de Andrade e

    2001-01-01

    Applications of electron beam processing in the treatment of polymers are commonly used. The interaction of high energy radiation with polymers may cause permanent modifications in the polymer's physicochemical structure. The induced modifications may result in degradation of the polymer or in improvement of its properties (crosslinking), which are simultaneous and competing processes, depending on the radiation dose utilized. Crosslinking occurs more readily in the polymer's amorphous content and this process makes the glass transition temperature (Tg) of the polymers to increase. Successive recycling cycles promote changes in polymers properties, such as breaking of structure, molecular weight reduction, melt index increase and mechanical resistance reduction. The polyamide-6 resin was recycled for three successive recycling cycles and thi polyamide-6 specimens were molded by the process of injection molding. These specimens were irradiated at the Nuclear Energetic Research Institute (IPEN) radiation facility, on a JOB 188 model accelerator, with a 1.5 MeV electron beam, doses of 200, 300, 400, 500 and 600 kGy, and dose rate of 22.61 kGy/s. The DMA tests were performed using DMA-983 equipment from TA Instruments and two heatings were adopted in order to eliminate the moisture absorption. The X-ray diffraction analysis wa carried out at the Philips PW 1830 model equipment

  17. Electronic structure of semiconductor interfaces

    Herman, F

    1983-02-01

    The study of semiconductor interfaces is one of the most active and exciting areas of current semiconductor research. Because interfaces play a vital role in modern semiconductor technology (integrated circuits, heterojunction lasers, solar cells, infrared detectors, etc.), there is a strong incentive to understand interface properties at a fundamental level and advance existing technology thereby. At the same time, technological advances such as molecular beam epitaxy have paved the way for the fabrication of semiconductor heterojunctions and superlattices of novel design which exhibit unusual electronic, optical, and magnetic properties and offer unique opportunities for fundamental scientific research. A general perspective on this subject is offered treating such topics as the atomic and electronic structure of semiconductor surfaces and interfaces; oxidation and oxide layers; semiconductor heterojunctions and superlattices; rectifying metal-semiconductor contacts; and interface reactions. Recent progress is emphasized and some future directions are indicated. In addition, the role that large-scale scientific computation has played in furthering our theoretical understanding of semiconductor surfaces and interfaces is discussed. Finally, the nature of theoretical models, and the role they play in describing the physical world is considered.

  18. Electronic structure of semiconductor interfaces

    Herman, F.

    1983-01-01

    The study of semiconductor interfaces is one of the most active and exciting areas of current semiconductor research. Because interfaces play a vital role in modern semiconductor technology (integrated circuits, heterojunction lasers, solar cells, infrared detectors, etc.), there is a strong incentive to understand interface properties at a fundamental level and advance existing technology thereby. At the same time, technological advances such as molecular beam epitaxy have paved the way for the fabrication of semiconductor heterojunctions and superlattices of novel design which exhibit unusual electronic, optical, and magnetic properties and offer unique opportunities for fundamental scientific research. A general perspective on this subject is offered treating such topics as the atomic and electronic structure of semiconductor surfaces and interfaces; oxidation and oxide layers; semiconductor heterojunctions and superlattices; rectifying metal-semiconductor contacts; and interface reactions. Recent progress is emphasized and some future directions are indicated. In addition, the role that large-scale scientific computation has played in furthering our theoretical understanding of semiconductor surfaces and interfaces is discussed. Finally, the nature of theoretical models, and the role they play in describing the physical world is considered. (Author) [pt

  19. Radiation Damage in Electronic Memory Devices

    Fetahović, Irfan; Pejović, Milić; Vujisić, Miloš

    2013-01-01

    This paper investigates the behavior of semiconductor memories exposed to radiation in order to establish their applicability in a radiation environment. The experimental procedure has been used to test radiation hardness of commercial semiconductor memories. Different types of memory chips have been exposed to indirect ionizing radiation by changing radiation dose intensity. The effect of direct ionizing radiation on semiconductor memory behavior has been analyzed by using Monte Carlo simula...

  20. Theory of coherent transition radiation generated by ellipsoidal electron bunches

    Root, op 't W.P.E.M.; Smorenburg, P.W.; Oudheusden, van T.; Wiel, van der M.J.; Luiten, O.J.

    2007-01-01

    We present the theory of coherent transition radiation (CTR) generated by ellipsoidal electron bunches. We calculate analytical expressions for the electric field spectrum, the power spectrum, and the temporal electric field of CTR, generated by cylindrically symmetric ellipsoidal electron bunches

  1. Principles and techniques of radiation hardening. Volume 2. Transient radiation effects in electronics (TREE)

    Rudie, N.J.

    1976-01-01

    The three-volume book is intended to serve as a review of the effects of thermonuclear explosion induced radiation (x-rays, gamma rays, and beta particles) and the resulting electromagnetic pulse (EMP). Volume 2 deals with the following topics: radiation effects on quartz crystals, tantalum capacitors, bipolar semiconductor devices and integrated circuits, field effect transistors, and miscellaneous electronic devices; hardening electronic systems to photon and neutron radiation; nuclear radiation source and/or effects simulation techniques; and radiation dosimetry

  2. Enhanced coherent undulator radiation from bunched electron beams

    Berryman, K.W.; Crosson, E.R.; Ricci, K.N.; Smith, T.I.

    1996-01-01

    When energetic bunches of electrons traverse an undulator field, they can spontaneously emit radiation both coherently and incoherently. Although it has generally been assumed that undulator radiation is incoherent at wavelengths short compared to the longitudinal size of the electron bunch, several recent observations have proved this assumption false. Furthermore, the appearance of coherent radiation is often accompanied by a significant increase in radiated power. Here we report observations of strongly enhanced coherent spontaneous radiation together with direct measurements, using transition radiation techniques, of the electron distributions responsible for the coherent emission. We also report demonstrated enhancements in the predicted spontaneous radiated power by as much as 6x10 4 using electron bunch compression. copyright 1996 American Institute of Physics

  3. Ultrarelativistic electron and positron radiation in planar channeling

    Kalashnikov, N.P.; Olchack, A.S.

    1980-01-01

    The coherent electromagnetic radiation from channeling electrons and positrons is given by similar expression. However for the channeling positrons the close collisions are suppressed due to the fact that the positron wave function is exponentially small near the atoms of the crystal lattice. It follows that the coherent bremsstrahlung decreases for the channeling positrons. We have investigated the ultrarelativistic channeling electron and positron radiations, connected with the electromagnetic transitions from the continuum spectrum states to the quasi-bound spectrum states and between the different quasi-bound spectrum states. The radiation probabilities are calculated by using the model continuum planar potential. It is shown that the radiation from the channeling electrons is several orders of magnitude larger than the positron radiation, while the electron and positron radiation have similar characteristics such as frequency limitation and angular distribution of the radiation. (orig.)

  4. Radiation curable adhesive compositions and composite structures

    Brenner, W.

    1984-01-01

    This disclosure relates to novel adhesive compositions and composite structures utilizing the same, wherein said adhesive compositions contain an elastomer, a chemically compatible ethylenically unsaturated monomer, a tackifier, an adhesion promoter, and optionally, pigments, fillers, thickeners and flow control agents which are converted from the liquid to the solid state by exposure to high energy ionizing radiation such as electron beam. A particularly useful application for such adhesive compositions comprises the assembly of certain composite structures or laminates consisting of, for example, a fiber flocked rubber sheet and a metal base with the adhesive fulfilling the multiple functions of adhering the flocked fiber to the rubber sheet as well as adhering the rubber sheet to the metal base. Optionally, the rubber sheet itself may also be cured at the same time as the adhesive composition with all operations being carried out at ambient temperatures and in the presence of air, with exposure of said assembly to selected dosages of high energy ionizing radiation. These adhesive compositions contain no solvents thereby almost eliminating air pollution or solvent toxicity problems, and offer substantial savings in energy and labor as they are capable of curing in very short time periods without the use of external heat which might damage the substrate

  5. Radiative capture of slow electrons by tungsten surface

    Artamonov, O.M.; Belkina, G.M.; Samarin, S.N.; Yakovlev, I.I.

    1987-01-01

    Isochromatic spectra of radiation capture of slow electrons by the surface of mono- and polycrystal tungsten recorded on 322 and 405 nm wave lengths are presented. The effect of oxygen adsorption on isochromates of the (110) face of tungsten monocrystal is investigated. The obtained isochromatic spectra are compared with energy band structure of tungsten. Based on the analysis of the obtained experimental results it is assumed that optical transition to the final state at the energy of 7.3 eV relatively to Fermi level is conditioned by surface states of the tungsten face (110)

  6. IMPELA electron accelerators for industrial radiation processing

    Hare, G.E.

    1990-01-01

    IMPELA electron accelerators are derived from a common basic design of rf accelerating structure which is capable of handling beams with powers from 20 to 250 kW at 5 to 18 MeV. A prototype has been built which operates at 50 kW and 10 MeV. The paper describes the major elements of the system with particular reference to features which assist in maintaining irradiation quality, simple operation and high reliability. A cost model based on the prototype is used to demonstrate the economies of scale available and the impact of local prices for utilities. (author)

  7. Radiation color and electron-hole centers of serpentines

    Lyutoev, V.P.; Yukhtanov, P.P.

    1999-01-01

    Radiation-induced coloring of serpentine (Mg 3 [Si 2 O 5 ](OH) 4 ), gamma radiation dose being 30 Mrad, is studied by the ESR and absorption spectroscopy methods. It is ascertained that ionizing radiation gives rise to formation of radiation centers on the mineral basic structural elements. paramagnetic centers and coloring centers, relating to radiation centers, stem from the same type of defects - O - oxygen centers, formed as a result of radiation-induced break of OH-bonds [ru

  8. Radiation Damage in Electronic Memory Devices

    Irfan Fetahović

    2013-01-01

    Full Text Available This paper investigates the behavior of semiconductor memories exposed to radiation in order to establish their applicability in a radiation environment. The experimental procedure has been used to test radiation hardness of commercial semiconductor memories. Different types of memory chips have been exposed to indirect ionizing radiation by changing radiation dose intensity. The effect of direct ionizing radiation on semiconductor memory behavior has been analyzed by using Monte Carlo simulation method. Obtained results show that gamma radiation causes decrease in threshold voltage, being proportional to the absorbed dose of radiation. Monte Carlo simulations of radiation interaction with material proved to be significant and can be a good estimation tool in probing semiconductor memory behavior in radiation environment.

  9. On radiation of electrons moving in braking electric fields with distributed potential

    Fedulov, V.I.; Suvorov, V.I.; Umirov, U.R.

    2002-01-01

    The characteristics of radiation of electron moving in flat structures with braking electric field created by an accelerating electrode and another electrode with distributed potential are investigated. The analytical expressions for definition of conditions for complete loss of energy by electron in structure with distributed potential and for arising the electron vibrations are received. Also expressions connecting the electron energy with the point of entry and its fluctuation frequency are received. The mathematical model of irradiation process is offered depending on energy and point of entry of the electron. The connection between a radiation wave length and position of point of entry of electrons in the braking electric field are found. A possibility of emerging the optical radiation in solid environments at passage of charge particles through substance is shown. (author)

  10. Tolerance of retroperitoneal structures to intraoperative radiation

    Sindelar, W.F.; Tepper, J.; Travis, E.L.; Terrill, R.

    1982-01-01

    In conjunction with the clinical development of intraoperative radiotherapy, a study was undertaken in dogs to define the tolerance of normal anatomic structures in the retroperitoneum to radiation delivered during operation. Twenty adult dogs were subjected to laparotomy and intraoperative 11 MeV electron irradiation in single doses ranging from 0.to 5000 rad. Animals were followed regularly with clinical observation, blood count, serum chemistries, pyelography, and angiography. Animals were sacrificed and autopsied at regular intervals up to 12 months following treatment to assess radiation-induced complications or tissue damage. Irradiation field in all dogs consisted of a 4 X 15 cm rectangle extending in the retroperitoneum from the level of the renal vessels to the bifurcation of aorta and vena cava. The field included aorta, vena cava, inferior portion of left kidney, and distal portion of left ureter. No complications or histologic changes occurred in any animal given doses of 2000 rad, with a follow-up in excess of 18 months. A dose of 3000 rad was well tolerated, except for left ureteral occlusion in one animal. Mild vascular fibrosis was present inthe aorta and vena cava, and significant ureteral fibrosis developed by six months after doses of 4000 or 5000 rad. All animals that received 5000 rad died of radiation-related complications, including ureteral obstruction and rectal perforation. It was concluded that major vessels tolerate intraoperative irradiation well up to and including 3000 rad and that no clinically significant vascular problems develop after 4000 and 5000 rad, although some fibrosis does occur. The ureter and kidney appear to be the most radiosensitive structures inthe retroperitoneum, showing progressive changes at 300 rad or greater and showing the potential for serious complications after doses of 4000 rad or more

  11. On electromagnetic radiation of ultrarelativistic electrons in crystals

    Podgoretskij, M.I.

    1977-01-01

    Electromagnetic radiation is considered caused by ultrarelativistic channeling electrons moving inside cylindrical regions formed with nuclear heat oscillations of a crystal lattice. An energy asymmetry is predicted for electrons and positrons, generated by γ-quanta falling to a crystal along the crystallographic axes. A possible connection of the above mentioned radiation with the anomalous multiphoton Schein showers is discussed

  12. Terrestrial radiation effects in ULSI devices and electronic systems

    Ibe, Eishi H

    2014-01-01

    A practical guide on how mathematical approaches can be used to analyze and control radiation effects in semiconductor devices within various environments Covers faults in ULSI devices to failures in electronic systems caused by a wide variety of radiation fields, including electrons, alpha -rays, muons, gamma rays, neutrons and heavy ions. Readers will learn the environmental radiation features at the ground or avionics altitude. Readers will also learn how to make numerical models from physical insight and what kind of mathematical approaches should be implemented to analyze the radiation effects. A wide variety of mitigation techniques against soft-errors are reviewed and discussed. The author shows how to model sophisticated radiation effects in condensed matter in order to quantify and control them. The book provides the reader with the knowledge on a wide variety of radiation fields and their effects on the electronic devices and systems. It explains how electronic systems including servers and rout...

  13. Synchrotron radiation and free electron laser activities in Novosibirsk

    Korchuganov, V.N.; Kulipanov, G.N.; Mezentsev, N.A.; Oreshkov, A.D.; Panchenko, V.E.; Pindyurin, V.F.; Skrinskij, A.N.; Sheromov, M.A.; Vinokurov, N.A.; Zolotarev, K.V.

    1994-01-01

    The results of studies realized in the Siberian synchrotron radiation centre within the frameworks of wide program of synchrotron radiation and free electron laser research are summarized. The technical information on the VEPP-2M, VEPP-3 and VEPP-4M storage rings used as synchrotron radiation sources is given. 10 refs.; 8 figs.; 12 tabs

  14. Transition and synchrotron radiation produced by electrons and particle discrimination

    Merkel, B.; Repellin, J.-P.; Sauvage, G.; Chollet, J.C.; Dialinas, M.; Gaillard, J.-M.; Hrisoho, A.; Jean, P.

    1976-01-01

    Transition radiation from a radiator of 650 lithium foils has been studied in a multiwire proportional chamber filled with a Xenon-CO 2 mixture for two experimental configurations. With the chamber immediately after the radiator, particle discrimination comparable to those reported in the litterature (90% efficiency for electrons, 10% for hadrons) have been observed. With magnetic bending between the radiator and the xenon chamber typical efficiencies of 87% for electrons and less than 0.4% for hadrons have been measured. The discrimination obtained is at least a factor 20 better than for the more conventional configuration. In the latter case, synchrotron radiation has also been observed

  15. DEVELOPMENT OF SHORT UNDULATORS FOR ELECTRON-BEAM-RADIATION INTERACTION STUDIES

    Piot, P. [NICADD, DeKalb; Andorf, M. B. [NICADD, DeKalb; Fagerberg, G. [Northern Illinois U.; Figora, M. [Northern Illinois U.; Sturtz, A. [Northern Illinois U.

    2016-10-19

    Interaction of an electron beam with external field or its own radiation has widespread applications ranging from coherent-radiation generation, phase space cooling or formation of temporally-structured beams. An efficient coupling mechanism between an electron beam and radiation field relies on the use of a magnetic undulator. In this contribution we detail our plans to build short (11-period) undulators with 7-cm period refurbishing parts of the aladdin U3 undulator [1]. Possible use of these undulators at available test facilities to support experiments relevant to cooling techniques and radiation sources are outlined.

  16. ''Atomic'' Bremsstrahlung or polarizational radiation in collision of many-electron ions

    Amusia, M.Ya.; Solov'yov, A.V.

    1991-01-01

    In this work the so-called ''Atomic'' bremsstrahlung (AB) or polarizational radiation, created in collisions of atoms or ions, is discussed. This kind of radiation arises due to the polarization of the electron shell of colliding particles. It is created by the structured projectiles and targets if the constituents are electrically charged. 6 refs, 2 figs

  17. Electron beam instrumentation techniques using coherent radiation

    Wang, D.X.

    1997-01-01

    Much progress has been made on coherent radiation research since coherent synchrotron radiation was first observed in 1989. The use of coherent radiation as a bunch length diagnostic tool has been studied by several groups. In this paper, brief introductions to coherent radiation and far-infrared measurement are given, the progress and status of their beam diagnostic application are reviewed, different techniques are described, and their advantages and limitations are discussed

  18. Coherent electromagnetic radiation of a combined electron-ion beam

    Pankratov, S G; Samoshenkov, Yu K [Vsesoyuznyj Nauchno-Issledovatel' skij Inst. Optiko-Fizicheskikh Izmerenij, Moscow (USSR)

    1977-07-01

    The intensity of coherent electromagnetic radiation due to interaction of a modulated electron beam with a modulated ion beam is calculated. It is shown that the radiation intensity has a sharp maximum at the frequency equal to the difference of the modulation frequency of the electron and ion beams. The results obtained are compared with those corresponding to the scattering of a modulated electron beam on randomly distributed gas ions.

  19. Absorption of resonant electromagnetic radiation in electron-atom collisions

    Arslanbekov, T.U.; Pazdzerskii, V.A.; Usachenko, V.I.

    1986-01-01

    Nonrelativistic quantum theory is used to study the possibility of amplification of electromagnetic radiation in forced braking scattering of an electron beam on atoms. The interaction of the atom with the electromagnetic field is considered in the resonant approximation. Cases of large and small detuning from resonance are considered. It is shown that for any orientation of the electron beam relative to the field polarization vector, absorption of radiation occurs, with the major contribution being produced by atomic electrons

  20. Radiation effects on structural materials

    Ghoniem, N.M.

    1991-01-01

    This report discusses the following topics on the effect radiation has on thermonuclear reactor materials: Atomic Displacements; Microstructure Evolution; Materials Engineering, Mechanics, and Design; Research on Low-Activation Steels; and Research Motivated by Grant Support

  1. PERCEPTION LEVEL EVALUATION OF RADIO ELECTRONIC MEANS TO A PULSE OF ELECTROMAGNETIC RADIATION

    2016-01-01

    Full Text Available The method for evaluating the perception level of electronic means to pulsed electromagnetic radiation is consid- ered in this article. The electromagnetic wave penetration mechanism towards the elements of electronic systems and the impact on them are determined by the intensity of the radiation field on the elements of electronic systems. The impact of electromagnetic radiation pulses to the electronic systems refers to physical and analytical parameters of the relationship between exposure to pulses of electromagnetic radiation and the sample parameters of electronic systems. A physical and mathematical model of evaluating the perception level of electronic means to pulsed electromagnetic radiation is given. The developed model was based on the physics of electronics means failure which represents the description of electro- magnetic, electric and thermal processes that lead to the degradation of the original structure of the apparatus elements. The conditions that lead to the total equation electronic systems functional destruction when exposed to electromagnetic radia- tion pulses are described. The internal characteristics of the component elements that respond to the damaging effects are considered. The ratio for the power failure is determined. A thermal breakdown temperature versus pulse duration of expo- sure at various power levels is obtained. The way of evaluation the reliability of electronic systems when exposed to pulses of electromagnetic radiation as a destructive factor is obtained.

  2. Electron paramagnetic resonance study on the ionizing radiation induced defects of the tooth enamel hydroxyapatite

    Oliveira, Liana Macedo de

    1995-01-01

    Hydroxyapatite is the main constituent of calcified tissues. Defects induced by ionizing radiations in this biomineral can present high stability and then, these are used as biological markers in radiological accidents, irradiated food identifying and geological and archaeological dating. In this work, paramagnetic centers induced on the enamel of the teeth by environmental ionizing radiation, are investigated by electron paramagnetic resonance (EPR). Decay thermal kinetic presents high complexity and shows the formation of different electron ligation energy centers and structures

  3. On the continuous spectrum electromagnetic radiation in electron-fullerene collision

    Amusia, M.Y.

    1995-01-01

    It is demonstrated that the electromagnetic radiation spectrum in electron-fullerene collisions is dominated by a huge maximum of multielectron nature, similar to that already predicted and observed in photoabsorption. Due to coherence, the intensity of this radiation is much stronger than the sum of the intensities of isolated atoms. Experimental detection of such radiation would be of great importance for understanding the mechanism of its formation and for investigating fullerene structures. A paper describing these results was published

  4. Optimization of equipment for electron radiation processing

    Tartz, M.; Hartmann, E.; Lenk, M.; Mehnert, R.

    1999-05-01

    In the course of the last decade, IOM Leipzig has developed low-energy electron accelerators for electron beam curing of polymer coatings and printing inks. In order to optimize the electron irradiation field, electron optical calculations have been carried out using the commercially available EGUN code. The present study outlines the design of the diode-type low-energy electron accelerators LEA and EBOGEN, taking into account the electron optical effects of secondary components such as the retaining rods installed in the cathode assembly.

  5. Optimization of equipment for electron radiation processing

    Tartz, M.; Hartmann, E.; Lenk, M.; Mehnert, R.

    1999-01-01

    In the course of the last decade, IOM Leipzig has developed low-energy electron accelerators for electron beam curing of polymer coatings and printing inks. In order to optimize the electron irradiation field, electron optical calculations have been carried out using the commercially available EGUN code. The present study outlines the design of the diode-type low-energy electron accelerators LEA and EBOGEN, taking into account the electron optical effects of secondary components such as the retaining rods installed in the cathode assembly

  6. Radiation of an electron in an electric field. 1

    Fedosov, N.I.; Flesher, G.I.

    1976-01-01

    The problem of electron radiation in a field of a travelling electric wave is solved by methods of classical electrodynamics. Such a field may serve as a model of a field on the linear accelerator axis. It is shown that the total radiation power, as well as the spectral-angular distribution of the radiation energy of an electron travelling in a longitudinal electric wave coincide with radiation in a stationary uniform electric field with the strength equal to that of the wave at the point where the particle velocity becomes close to the velocity of light [ru

  7. Spin-polarized free electron beam interaction with radiation and superradiant spin-flip radiative emission

    A. Gover

    2006-06-01

    Full Text Available The problems of spin-polarized free-electron beam interaction with electromagnetic wave at electron-spin resonance conditions in a magnetic field and of superradiant spin-flip radiative emission are analyzed in the framework of a comprehensive classical model. The spontaneous emission of spin-flip radiation from electron beams is very weak. We show that the detectivity of electron spin resonant spin-flip and combined spin-flip/cyclotron-resonance-emission radiation can be substantially enhanced by operating with ultrashort spin-polarized electron beam bunches under conditions of superradiant (coherent emission. The proposed radiative spin-state modulation and the spin-flip radiative emission schemes can be used for control and noninvasive diagnostics of polarized electron/positron beams. Such schemes are of relevance in important scattering experiments off nucleons in nuclear physics and off magnetic targets in condensed matter physics.

  8. Electronic structure studies of fullerites and fullerides

    Merkel, M.; Sohmen, E.; Masaki, A.; Romberg, H.; Alexander, M.; Knupfer, M.; Golden, M.S.; Adelmann, P.; Renker, B.; Fink, J.

    1993-01-01

    The electronic structure of fullerites and fullerides has been investigated by high-resolution photoemission and by high-energy electron energy-loss spectroscopy in transmission. Information on the occupied Π and σ bands, on the unoccupied Π * and σ * bands, and on the joint density of states has been obtained. In particular, we report on the changes of the electronic structure of fullerides as a function of dopant concentration. (orig.)

  9. Solvated electron structure in glassy matrices

    Kevan, L.

    1981-01-01

    Current knowledge of the detailed geometrical structure of solvated electrons in aqueous and organic media is summarized. The geometry of solvated electrons in glassy methanol, ethanol, and 2-methyltetrahydrofuran is discussed. Advanced electron magnetic resonance methods and development of new methods of analysis of electron spin echo modulation patterns, second moment line shapes, and forbidden photon spin-flip transitions for paramagnetic species in these disordered systems are discussed. 66 references are cited

  10. Structural modifications of spinels under radiation

    Quentin, A.

    2010-12-01

    This work is devoted to the study of spinel structure materials under radiation. For that purpose, samples of polycrystalline ZnAl 2 O 4 and monocrystalline MgAl 2 O 4 were irradiated by different heavy ions with different energies. Samples of ZnAl 2 O 4 were studied par electron transmission microscopy, and by grazing incidence X-Ray diffraction and Rietveld analysis. Samples of MgAl 2 O 4 were studied by optical spectroscopy. Most of the results concern amorphization and crystalline structure modification of ZnAl 2 O 4 especially the inversion. We were able to determine a stopping power threshold for amorphization, between 11 keV/nm and 12 keV/nm, and also the amorphization process, which is a multiple impacts process. We studied the evolution of the amorphous phase by TEM and showed a nano-patterning phenomenon. Concerning the inversion, we determined that it did happen by a single impact process, and the saturation value did not reach the random cation distribution value. Inversion and amorphization have different, but close, stopping power threshold. However, amorphization seems to be conditioned by a pre-damage of the material which consists in inversion. (author)

  11. Electronic structure and tautomerism of thioamides

    Novak, Igor, E-mail: inovak@csu.edu.au [Charles Sturt University, POB 883, Orange, NSW 2800 (Australia); Klasinc, Leo, E-mail: klasinc@irb.hr [Physical Chemistry Department, Ruđer Bošković Institute, HR-10002 Zagreb (Croatia); McGlynn, Sean P., E-mail: sean.mcglynn@chemgate.chem.lsu.edu [Louisiana State University, Baton Rouge, LA 70803 (United States)

    2016-05-15

    Highlights: • Electronic structure of thioamide group and its relation to Lewis basicity. • Tautomerism of the (thio)amide groups. • Substituent effects on the electronic structure of (thio)amide group. - Abstract: The electronic structures of several thioamides have been studied by UV photoelectron spectroscopy (UPS). The relative stabilities of keto–enol tautomers have been determined using high-level ab initio calculations and the results were used in the analysis of UPS spectra. The main features of electronic structure and tautomerism of thioamide derivatives are discussed. The predominant tautomers in the gas phase are of keto–(thio)keto form. The addition of cyclohexanone moiety to the thioamide group enhances the Lewis base character of the sulfur atom. The addition of phenyl group to the (thio)amide group significantly affects its electronic structure.

  12. Electronic structure of point defects in semiconductors

    Bruneval, Fabien

    2014-01-01

    This 'Habilitation a diriger des Recherches' memoir presents most of my scientific activities during the past 7 years, in the field of electronic structure calculations of defects in solids. Point defects (vacancies, interstitials, impurities) in functional materials are a key parameter to determine if these materials will actually fill the role they have been assigned or not. Indeed, the presence of defects cannot be avoided when the temperature is increased or when the material is subjected to external stresses, such as irradiation in the nuclear reactors and in artificial satellites with solar radiations. However, in many cases, defects are introduced in the materials on purpose to tune the electronic transport, optical or even magnetic properties. This procedure is called the doping of semiconductors, which is the foundation technique for transistors, diodes, or photovoltaic cells. However, doping is not always straightforward and unexpected features may occur, such as doping asymmetry or Fermi level pinning, which can only be explained by complex phenomena involving different types of defects or complexes of defects. In this context, the calculations of electronic structure ab initio is an ideal tool to complement the experimental observations, to gain the understanding of phenomena at the atomic level, and even to predict the properties of defects. The power of the ab initio calculations comes from their ability to describe any system of electrons and nuclei without any specific adjustment. But although there is a strong need for numerical simulations in this field, the ab initio calculations for defects are still under development as of today. The work presented in this memoir summarizes my contributions to methodological developments on this subject. These developments have followed two main tracks. The first topic is the better understanding of the unavoidable finite size effects. Indeed, defects in semiconductors or insulators are generally present in

  13. Radiation effects on and dose enhancement of electronic materials

    Srour, J.R.; Long, D.M.

    1984-01-01

    This book describes radiation effects on and dose enhancement factors for electronic materials. Alteration of the electrical properties of solid-state devices and integrated circuits by impinging radiation is well-known. Such changes may cause an electronic subsystem to fail, thus there is currently great interest in devising methods for avoiding radiation-induced degradation. The development of radiation-hardened devices and circuits is an exciting approach to solving this problem for many applications, since it could minimize the need for shielding or other system hardening techniques. Part 1 describes the basic mechanisms of radiation effects on electronic materials, devices, and integrated circuits. Radiation effects in bulk silicon and in silicon devices are treated. Ionizing radiation effects in silicon dioxide films and silicon MOS devices are discussed. Single event phenomena are considered. Key literature references and a bibliography are provided. Part II provides tabulations of dose enhancement factors for electronic devices in x-ray and gamma-ray environments. The data are applicable to a wide range of semiconductor devices and selected types of capacitors. Radiation environments discussed find application in system design and in radiation test facilities

  14. Electronic-structure studies of metal-hydrogen systems using photoelectron spectroscopy (PES) radiation. Final report, 1 March 1980-31 August 1982

    Weaver, J.H.

    1982-09-01

    Photoelectron spectroscopy studies of hydrogen-bearing metals and alloys have provided fundamental information concerning the electronic interactions of hydrides. Studies of surface oxidation of several hydrogen storage materials (the LaNi 5 -family) evaluated the role of surface oxidation on hydrogen uptake. Collaborative band theory studies were undertaken to support experimental studies of the metal-semiconductor transition in LaH 2 -LaH 3 and of the refractory metal mono- and submonohydrides

  15. Radiation Effects on Spacecraft Structural Materials

    Wang, Jy-An J.; Ellis, Ronald J.; Hunter, Hamilton T.; Singleterry, Robert C. Jr.

    2002-01-01

    Research is being conducted to develop an integrated technology for the prediction of aging behavior for space structural materials during service. This research will utilize state-of-the-art radiation experimental apparatus and analysis, updated codes and databases, and integrated mechanical and radiation testing techniques to investigate the suitability of numerous current and potential spacecraft structural materials. Also included are the effects on structural materials in surface modules and planetary landing craft, with or without fission power supplies. Spacecraft structural materials would also be in hostile radiation environments on the surface of the moon and planets without appreciable atmospheres and moons around planets with large intense magnetic and radiation fields (such as the Jovian moons). The effects of extreme temperature cycles in such locations compounds the effects of radiation on structural materials. This paper describes the integrated methodology in detail and shows that it will provide a significant technological advance for designing advanced spacecraft. This methodology will also allow for the development of advanced spacecraft materials through the understanding of the underlying mechanisms of material degradation in the space radiation environment. Thus, this technology holds a promise for revolutionary advances in material damage prediction and protection of space structural components as, for example, in the development of guidelines for managing surveillance programs regarding the integrity of spacecraft components, and the safety of the aging spacecraft. (authors)

  16. Studies on electronic structure of GaN(0001) surface

    Xie Chang Kun; Xu Fa Qiang; Deng Rui; Liu Feng; Yibulaxin, K

    2002-01-01

    An electronic structure investigation on GaN(0001) is reported. The authors employ a full-potential linearized augmented plane-wave (FPLAPW) approach to calculate the partial density of state, which is in agreement with previous experimental results. The effects of the Ga3d semi-core levels on the electronic structure of GaN are discussed. The valence-electronic structure of the wurtzite GaN(0001) surface is investigated using synchrotron radiation excited angle-resolved photoemission spectroscopy. The bulk bands dispersion along GAMMA A direction in the Brillouin zones is measured using normal-emission spectra by changing photon-energy. The band structure derived from authors' experimental data is compared well with the results of authors' FPLAPW calculation. Furthermore, off-normal emission spectra are also measured along the GAMMA K and GAMMA M directions. Two surface states are identified, and their dispersions are characterized

  17. Soft component of channeled electron radiation in silicon crystals

    Vnukov, I.E.; Kalinin, B.N.; Kiryakov, A.A.; Naumenko, G.A.; Padalko, D.V.; Potylitsyn, A.P.

    2001-01-01

    Radiation spectrum and orientation dependences of photon yield with the energy much lower than characteristic radiation energy during channeling were measured using a crystal-diffraction spectrometer. For electron drop along axis radiation intensity in the spectral range 30 ≤ ω ≤ 360 keV exceeds by nearly an order the intensity of Bremsstrahlung. The shape of radiation spectrum does not coincide with Bremsstrahlung spectrum. Radiation intensity increases gradually with photons energy growth. Bremsstrahlung spectrum from a disoriented crystalline target is described in a satisfactory manner by the currently used theory with phenomenological account of the medium polarization [ru

  18. Atomic and molecular photoelectron and Auger-electron-spectroscopy studies using synchrotron radiation

    Southworth, S.H.

    1982-01-01

    Electron spectroscopy, combined with synchrotron radiation, was used to measure the angular distributions of photoelectrons and Auger electrons from atoms and molecules as functions of photon energy. The branching ratios and partial cross sections were also measured in certain cases. By comparison with theoretical calculations, the experimental results are interpreted in terms of the characteristic electronic structure and ionization dynamics of the atomic or molecular sample. The time structure of the synchrotron radiation source was used to record time-of-flight (TOF) spectra of the ejected electrons. The double-angle-TOF method for the measurement of photoelectron angular distributions is discussed. This technique offers the advantages of increased electron collection efficiency and the elimination of certain systematic errors. An electron spectroscopy study of inner-shell photoexcitation and ionization of Xe, photoelectron angular distributions from H 2 and D 2 , and photoionization cross sections and photoelectron asymmetries of the valence orbitals of NO are reported

  19. Electron Bunch Length Diagnostic With Coherent Smith-Purcell Radiation

    Nguyen, D.C.

    1997-05-12

    The authors have designed a new technique for measuring subpicosecond electron bunch lengths using coherent Smith-Purcell radiation. This new diagnostic technique involves passing the electron beam in close proximity of a grating with a period comparable to the electron bunch length. The emitted Smith-Purcell radiation will have a coherent component whose angular position and distribution are directly related to the electron bunch length and longitudinal profile, respectively. This new diagnostic technique is inherently simple, inexpensive and non-intercepting. The authors show that the new technique is also scaleable to femtosecond regime.

  20. Electron Bunch Length Diagnostic With Coherent Smith-Purcell Radiation

    Nguyen, D.C.

    1997-01-01

    The authors have designed a new technique for measuring subpicosecond electron bunch lengths using coherent Smith-Purcell radiation. This new diagnostic technique involves passing the electron beam in close proximity of a grating with a period comparable to the electron bunch length. The emitted Smith-Purcell radiation will have a coherent component whose angular position and distribution are directly related to the electron bunch length and longitudinal profile, respectively. This new diagnostic technique is inherently simple, inexpensive and non-intercepting. The authors show that the new technique is also scaleable to femtosecond regime

  1. Longitudinal Electron Bunch Diagnostics Using Coherent Transition Radiation

    Mihalcea, Daniel; Happek, Uwe; Regis-Guy Piot, Philippe

    2005-01-01

    The longitudinal charge distribution of electron bunches in the Fermilab A0 photo-injector was determined by using the coherent transition radiation produced by electrons passing through a thin metallic foil. The auto-correlation of the transition radiation signal was measured with a Michelson type interferometer. The response function of the interferometer was determined from measured and simulated power spectra for low electron bunch charge and maximum longitudinal compression. Kramers-Kroning technique was used to determine longitudinal charge distribution. Measurements were performed for electron bunch lengths in the range from 0.3 to 2 ps (rms).

  2. Electron scattering and nuclear structure

    Wolynec, E.

    1985-01-01

    A review of the historical development and the theory necessary to the interpretation of the experimental results is made. Some measurement techniques, experimental results and the technique of analysis of these data are presented. Future perspectives, due to the appearence of continous electron current accelerators, in this field of study are discussed. (L.C.) [pt

  3. Electron gun controlled smart structure

    Martin, Jeffrey W.; Main, John Alan; Redmond, James M.; Henson, Tammy D.; Watson, Robert D.

    2001-01-01

    Disclosed is a method and system for actively controlling the shape of a sheet of electroactive material; the system comprising: one or more electrodes attached to the frontside of the electroactive sheet; a charged particle generator, disposed so as to direct a beam of charged particles (e.g. electrons) onto the electrode; a conductive substrate attached to the backside of the sheet; and a power supply electrically connected to the conductive substrate; whereby the sheet changes its shape in response to an electric field created across the sheet by an accumulation of electric charge within the electrode(s), relative to a potential applied to the conductive substrate. Use of multiple electrodes distributed across on the frontside ensures a uniform distribution of the charge with a single point of e-beam incidence, thereby greatly simplifying the beam scanning algorithm and raster control electronics, and reducing the problems associated with "blooming". By placing a distribution of electrodes over the front surface of a piezoelectric film (or other electroactive material), this arrangement enables improved control over the distribution of surface electric charges (e.g. electrons) by creating uniform (and possibly different) charge distributions within each individual electrode. Removal or deposition of net electric charge can be affected by controlling the secondary electron yield through manipulation of the backside electric potential with the power supply. The system can be used for actively controlling the shape of space-based deployable optics, such as adaptive mirrors and inflatable antennae.

  4. The Theory of Coherent Radiation by Intense Electron Beams

    Buts, Vyacheslav A; Kurilko, V.I

    2006-01-01

    Spurred by the development of high-current, high-energy relativistic electron beams this books delves into the foundations of a device and geometry independent theoretical treatment of a large collection of interacting and radiating electron bunches. Part I deals with the basics of the radiation emission of a single charged particle, paying particular attention to the effect of radiation reaction and dwelling on the corresponding well-known paradoxes. Part II investigates the collective behaviour of a high-density electron bunch where both discrete and continous beam modelling is explored. Part III treats the application to modern systems while still keeping the treatment as general as possible. This book will be mandatory reading for anyone working on the foundations of modern devices such as free electron lasers, plasma accelerators, synchroton sources and other modern sources of bright, coherent radiation with high spectral density.

  5. Electronic Structure of Lithium Tetraborate

    2010-06-01

    and Optical Properties of Li2B4O7 Single Crystals Pure and Doped with Yb, Co and Mn Ions for Nonlinear Applications," Acta Physica Polonica A 107...34Growth and Optical Properties of Li2B4O7 Single Crystals Pure and Doped with Yb, Co and Mn Ions for Nonlinear Applications," Acta Physica ... Polonica A 107, 507 (2005). 22. Y. V. Burak, B. V. Padlyak, and V. M. Shevel, "Radiation-induced centers in the Li2B4O7 single crystals," Nuclear

  6. Electron bunch length measurement with a wakefield radiation decelerator

    Weiwei Li

    2014-03-01

    Full Text Available In this paper, we propose a novel method to measure the electron bunch length with a dielectric wakefield radiation (DWR decelerator which is composed of two dielectric-lined waveguides (DLWs and an electron spectrometer. When an electron beam passes through a DLW, the DWR is excited which leads to an energy loss of the electron beam. The energy loss is found to be largely dependent on the electron bunch length and can be easily measured by an electron spectrometer which is essential for a normal accelerator facility. Our study shows that this method has a high resolution and a great simplicity.

  7. Heat- and radiation-resistant scintillator for electron microscopes

    Kosov, A.V.; Petrov, S.A.; Puzyr', A.P.; Chetvergov, N.A.

    1987-01-01

    The use of a scintillator consisting of a single crystal of bismuth orthogermanate, which has high heat and radiation resistance, in REM-100, REM-200, and REM-100U electron microscopes is described. A study of the heat and radiation stabilities of single crystals of bismuth orthogermanate (Bi 4 Ge 3 O 12 ) has shown that they withstood multiple electron-beam heating redness (T ∼ 800 0 C) without changes in their properties

  8. Radiation-emitting Electronic Product Codes

    U.S. Department of Health & Human Services — This database contains product names and associated information developed by the Center for all products, both medical and non-medical, which emit radiation. It...

  9. Online Simulation of Radiation Track Structure Project

    Plante, Ianik

    2015-01-01

    Space radiation comprises protons, helium and high charged and energy (HZE) particles. High-energy particles are a concern for human space flight, because they are no known options for shielding astronauts from them. When these ions interact with matter, they damage molecules and create radiolytic species. The pattern of energy deposition and positions of the radiolytic species, called radiation track structure, is highly dependent on the charge and energy of the ion. The radiolytic species damage biological molecules, which may lead to several long-term health effects such as cancer. Because of the importance of heavy ions, the radiation community is very interested in the interaction of HZE particles with DNA, notably with regards to the track structure. A desktop program named RITRACKS was developed to simulate radiation track structure. The goal of this project is to create a web interface to allow registered internal users to use RITRACKS remotely.

  10. STRUCTURAL STABILITY AND ELECTRONIC STRUCTURE OF ...

    2012-12-31

    Dec 31, 2012 ... may be applications at high temperature strength and corrosion ... B2 structure, like that found in cesium-chloride (CsCl) and chemical formula RM, where R denotes a rare - earth element and M denotes a late transition metal ...

  11. Effect of electronic radiation in Nb monocrystals

    Otero, M.P.; Lucki, G.

    1984-01-01

    The effect of the electronic irradiation in the Nb monocrystalline samples is studied. The irradiation source were the electrons from the high voltage electronic microscopy from the Argonne National Laboratory operating in 900 KeV. With the irradiation and deformation 'in-situ' experiments, dislocations in the samples were observed and the effect of the electrons in those dislocations during 59m of irradiation was studied. The follow applied deformation, show the differences in the displacements behavior of the non-irradiated and irradiated region. The growth rate of the displacements rings were determined. (E.G.) [pt

  12. Modeling of Jupiter's electron an ion radiation belts

    Sicard, Angelica

    2004-01-01

    In the Fifties, James Van Allen showed the existence of regions of the terrestrial magnetosphere consisted of energetic particles, trapped by the magnetic field: the radiation belts. The radiation belts of the Earth were the subject of many modeling works and are studied since several years at the Departement Environnement Spatial (DESP) of ONERA. In 1998, the DESP decided to adapt the radiation belts model of the Earth, Salammbo, to radiation environment of Jupiter. A first thesis was thus carried out on the subject and a first radiation belts model of electrons of Jupiter was developed [Santos-Costa, 2001]. The aim of this second thesis is to develop a radiation belts model for protons and heavy ions. In order to validate the developed model, the comparisons between Salammbo results and observations are essential. However, the validation is difficult in the case of protons and heavy ions because in-situ measurements of the probes are very few and most of the time contaminated by very energetic electrons. To solve this problem, a very good model of electrons radiation belts is essential to confirm or cancel the contamination of protons and heavy ions measurements. Thus, in parallel to the development of the protons and heavy ions radiation belts model, the electrons models, already existing, has been improved. Then Salammbo results have been compared to the different observations available (in-situ measurements, radio-astronomical observations). The different comparisons show a very good agreement between Salammbo results and observations. (author) [fr

  13. Radiation field mapping using a mechanical-electronic detector

    Czayka, M., E-mail: mczayka@kent.ed [College of Technology, Kent State University-Ashtabula 3300 Lake Road West, Ashtabula, OH 44004 (United States); Program on Electron Beam Technology, Kent State University, P.O. Box 1028, Middlefield, OH 44062 (United States); Fisch, M. [Program on Electron Beam Technology, Kent State University, P.O. Box 1028, Middlefield, OH 44062 (United States); College of Technology, Kent State University, P.O. Box 5190, Kent, OH 44242-0001 (United States)

    2010-04-15

    A method of radiation field mapping of a scanned electron beam using a Faraday-type detector and an electromechanical linear translator is presented. Utilizing this arrangement, fluence and fluence rate measurements can be made at different locations within the radiation field. The Faraday-type detector used in these experiments differs from most as it consists of a hollow stainless steel sphere. Results are presented in two- and three-dimensional views of the radiation field.

  14. Intense synchrotron radiation from a magnetically compressed relativistic electron layer

    Shearer, J.W.; Nowak, D.A.; Garelis, E.; Condit, W.C.

    1975-10-01

    Using a simple model of a relativistic electron layer rotating in an axial magnetic field, energy gain by an increasing magnetic field and energy loss by synchrotron radiation were considered. For a typical example, initial conditions were approximately 8 MeV electron in approximately 14 kG magnetic field, at a layer radius of approximately 20 mm, and final conditions were approximately 4 MG magnetic field approximately 100 MeV electron layer energy at a layer radius of approximately 1.0 mm. In the final state, the intense 1-10 keV synchrotron radiation imposes an electron energy loss time constant of approximately 100 nanoseconds. In order to achieve these conditions in practice, the magnetic field must be compressed by an imploding conducting liner; preferably two flying rings in order to allow the synchrotron radiation to escape through the midplane. The synchrotron radiation loss rate imposes a lower limit to the liner implosion velocity required to achieve a given final electron energy (approximately 1 cm/μsec in the above example). In addition, if the electron ring can be made sufficiently strong (field reversed), the synchrotron radiation would be a unique source of high intensity soft x-radiation

  15. Galileo Measurements of the Jovian Electron Radiation Environment

    Garrett, H. B.; Jun, I.; Ratliff, J. M.; Evans, R. W.; Clough, G. A.; McEntire, R. W.

    2003-12-01

    The Galileo spacecraft Energetic Particle Detector (EPD) has been used to map Jupiter's trapped electron radiation in the jovian equatorial plane for the range 8 to 16 Jupiter radii (1 jovian radius = 71,400 km). The electron count rates from the instrument were averaged into 10-minute intervals over the energy range 0.2 MeV to 11 MeV to form an extensive database of observations of the jovian radiation belts between Jupiter orbit insertion (JOI) in 1995 and end of mission in 2003. These data were then used to provide differential flux estimates in the jovian equatorial plane as a function of radial distance (organized by magnetic L-shell position). These estimates provide the basis for an omni-directional, equatorial model of the jovian electron radiation environment. The comparison of these results with the original Divine model of jovian electron radiation and their implications for missions to Jupiter will be discussed. In particular, it was found that the electron dose predictions for a representative mission to Europa were about a factor of 2 lower than the Divine model estimates over the range of 100 to 1000 mils (2.54 to 25.4 mm) of aluminum shielding, but exceeded the Divine model by about 50% for thicker shielding for the assumed Europa orbiter trajectories. The findings are a significant step forward in understanding jovian electron radiation and represent a valuable tool for estimating the radiation environment to which jovian science and engineering hardware will be exposed.

  16. A radiation-tolerant electronic readout system for portal imaging

    Östling, J.; Brahme, A.; Danielsson, M.; Iacobaeus, C.; Peskov, V.

    2004-06-01

    A new electronic portal imaging device, EPID, is under development at the Karolinska Institutet and the Royal Institute of Technology. Due to considerable demands on radiation tolerance in the radiotherapy environment, a dedicated electronic readout system has been designed. The most interesting aspect of the readout system is that it allows to read out ˜1000 pixels in parallel, with all electronics placed outside the radiation beam—making the detector more radiation resistant. In this work we are presenting the function of a small prototype (6×100 pixels) of the electronic readout board that has been tested. Tests were made with continuous X-rays (10-60 keV) and with α particles. The results show that, without using an optimised gas mixture and with an early prototype only, the electronic readout system still works very well.

  17. Storm-time radiation belt electron dynamics: Repeatability in the outer radiation belt

    Murphy, K. R.; Mann, I. R.; Rae, J.; Watt, C.; Boyd, A. J.; Turner, D. L.; Claudepierre, S. G.; Baker, D. N.; Spence, H. E.; Reeves, G. D.; Blake, J. B.; Fennell, J. F.

    2017-12-01

    During intervals of enhanced solar wind driving the outer radiation belt becomes extremely dynamic leading to geomagnetic storms. During these storms the flux of energetic electrons can vary by over 4 orders of magnitude. Despite recent advances in understanding the nature of competing storm-time electron loss and acceleration processes the dynamic behavior of the outer radiation belt remains poorly understood; the outer radiation belt can exhibit either no change, an enhancement, or depletion in radiation belt electrons. Using a new analysis of the total radiation belt electron content, calculated from the Van Allen probes phase space density (PSD), we statistically analyze the time-dependent and global response of the outer radiation belt during storms. We demonstrate that by removing adiabatic effects there is a clear and repeatable sequence of events in storm-time radiation belt electron dynamics. Namely, the relativistic (μ=1000 MeV/G) and ultra-relativistic (μ=4000 MeV/G) electron populations can be separated into two phases; an initial phase dominated by loss followed by a second phase dominated by acceleration. At lower energies, the radiation belt seed population of electrons (μ=150 MeV/G) shows no evidence of loss but rather a net enhancement during storms. Further, we investigate the dependence of electron dynamics as a function of the second adiabatic invariant, K. These results demonstrate a global coherency in the dynamics of the source, relativistic and ultra-relativistic electron populations as function of the second adiabatic invariant K. This analysis demonstrates two key aspects of storm-time radiation belt electron dynamics. First, the radiation belt responds repeatably to solar wind driving during geomagnetic storms. Second, the response of the radiation belt is energy dependent, relativistic electrons behaving differently than lower energy seed electrons. These results have important implications in radiation belt research. In particular

  18. Electronic structure of metallic glasses

    Oelhafen, P.; Lapka, R.; Gubler, U.; Krieg, J.; DasGupta, A.; Guentherodt, H.J.; Mizoguchi, T.; Hague, C.; Kuebler, J.; Nagel, S.R.

    1981-01-01

    This paper is organized in six sections and deals with (1) the glassy transition metal alloys, their d-band structure, the d-band shifts on alloying and their relation to the alloy heat of formation (ΔH) and the glass forming ability, (2) the glass to crystal phase transition viewed by valence band spectroscopy, (3) band structure calculations, (4) metallic glasses prepared by laser glazing, (5) glassy normal metal alloys, and (6) glassy hydrides

  19. Electronic structure and tautomerism of aryl ketones

    Novak, Igor; Klasinc, Leo; Šket, Boris; McGlynn, S.P.

    2015-01-01

    Graphical abstract: Photoelectron spectroscopy, tautomerism. - Highlights: • UV photoelectron spectroscopy of aryl ketones. • The relative stability of tautomers and their electronic structures. • The factors influencing tautomerism. - Abstract: The electronic structures of several aryl ketones (AK) and their α-halo derivatives have been studied by UV photoelectron spectroscopy (UPS). The relative stabilities of keto–enol tautomers have been determined using high-level ab initio calculations and the results were used in the analysis of UPS spectra. The main features of electronic structure and tautomerism of the AK derivatives are discussed

  20. Phenomenology of the electron structure function

    Slominski, W.; Szwed, J.

    2001-01-01

    The advantages of introducing the electron structure function (ESF) in electron induced processes are demonstrated. Contrary to the photon structure function it is directly measured in such processes. At present energies, a simultaneous analysis of both the electron and the photon structure functions gives an important test of the experimentally applied methods. Estimates of the ESF at LEP momenta are given. At very high momenta contributions from W and Z bosons together with γ-Z interference can be observed. Predictions for the next generation of experiments are given. (orig.)

  1. Electronic structure and tautomerism of aryl ketones

    Novak, Igor, E-mail: inovak@csu.edu.au [Charles Sturt University, POB 883, Orange, NSW 2800 (Australia); Klasinc, Leo, E-mail: klasinc@irb.hr [Physical Chemistry Department, Ruđer Bošković Institute, HR-10002 Zagreb (Croatia); Šket, Boris, E-mail: Boris.Sket@fkkt.uni-lj.si [Faculty of Chemistry and Chemical Technology, University of Ljubljana, SI-1000 (Slovenia); McGlynn, S.P., E-mail: sean.mcglynn@chemgate.chem.lsu.edu [Louisiana State University, Baton Rouge, LA 70803 (United States)

    2015-07-15

    Graphical abstract: Photoelectron spectroscopy, tautomerism. - Highlights: • UV photoelectron spectroscopy of aryl ketones. • The relative stability of tautomers and their electronic structures. • The factors influencing tautomerism. - Abstract: The electronic structures of several aryl ketones (AK) and their α-halo derivatives have been studied by UV photoelectron spectroscopy (UPS). The relative stabilities of keto–enol tautomers have been determined using high-level ab initio calculations and the results were used in the analysis of UPS spectra. The main features of electronic structure and tautomerism of the AK derivatives are discussed.

  2. Electromagnetic Radiation Originating from Unstable Electron Oscillations

    Juul Rasmussen, Jens; Pécseli, Hans

    1975-01-01

    Electromagnetic oscillations in the range 300 – 700 MHz were observed from an unmagnetized argon discharge with an unstable electron velocity distribution function.......Electromagnetic oscillations in the range 300 – 700 MHz were observed from an unmagnetized argon discharge with an unstable electron velocity distribution function....

  3. Changes of the electronic structure of the atoms of nitrogen in nitrogen-doped multiwalled carbon nanotubes under the influence of pulsed ion radiation

    Korusenko, P.M., E-mail: korusenko@obisp.oscsbras.ru [Omsk Scientific Centre, Siberian Branch, Russian Academy of Sciences, Karl Marx Avenue, 15, Omsk 644024 (Russian Federation); Bolotov, V.V.; Nesov, S.N.; Povoroznyuk, S.N. [Omsk Scientific Centre, Siberian Branch, Russian Academy of Sciences, Karl Marx Avenue, 15, Omsk 644024 (Russian Federation); Khailov, I.P. [Tomsk Polytechnic University, Lenin Ave. 2a, Tomsk 634028 (Russian Federation)

    2015-09-01

    With the use of X-ray photoelectron spectroscopy (XPS) there have been investigated the changes of the chemical state of nitrogen atoms in the structure of nitrogen-doped multiwalled carbon nanotubes (CN{sub x}-MWCNTs) resulting from the impact of pulsed ion beam at various parameters of the beam (energy density, number of pulses). It has been established that irradiation with the pulsed ion beam leads to a reduction of the total amount of nitrogen in CN{sub x} nanotubes. It has been shown that a single pulse irradiation of ion beam at the energy densities of 0.5, 1, 1.5 J/cm{sup 2} leads to restructuring of the nitrogen from pyridinic and pyrrolic configuration to graphitic state. Complete removal of nitrogen (pyridinic, pyrrolic, graphitic) embedded in the structure of the walls of CN{sub x} nanotubes occurs at ten pulses and 1.5 J/cm{sup 2}.

  4. Epitaxial graphene electronic structure and transport

    De Heer, Walt A; Berger, Claire; Wu Xiaosong; Sprinkle, Mike; Hu Yike; Ruan Ming; First, Phillip N; Stroscio, Joseph A; Haddon, Robert; Piot, Benjamin; Faugeras, Clement; Potemski, Marek; Moon, Jeong-Sun

    2010-01-01

    Since its inception in 2001, the science and technology of epitaxial graphene on hexagonal silicon carbide has matured into a major international effort and is poised to become the first carbon electronics platform. A historical perspective is presented and the unique electronic properties of single and multilayered epitaxial graphenes on electronics grade silicon carbide are reviewed. Early results on transport and the field effect in Si-face grown graphene monolayers provided proof-of-principle demonstrations. Besides monolayer epitaxial graphene, attention is given to C-face grown multilayer graphene, which consists of electronically decoupled graphene sheets. Production, structure and electronic structure are reviewed. The electronic properties, interrogated using a wide variety of surface, electrical and optical probes, are discussed. An overview is given of recent developments of several device prototypes including resistance standards based on epitaxial graphene quantum Hall devices and new ultrahigh frequency analogue epitaxial graphene amplifiers.

  5. CMOS front-end electronics for radiation sensors

    AUTHOR|(CDS)2071026

    2015-01-01

    This book offers a comprehensive treatment of front-end electronics for radiation detection. It discusses the fundamental principles of signal processing for radiation detectors and describes circuits at the level of functional building blocks, omitting transistor-level implementation. It also covers important system-level topics commonly found in the world of front-end electronics for radiation sensors. The book develops the topics in detail, with a constant focus on practical problems. It also provides real implementation examples that offer insights and stimuli for more experienced engineers already working in the field.

  6. Scattered radiation from applicators in clinical electron beams

    Battum, L J van; Zee, W van der; Huizenga, H

    2003-01-01

    In radiotherapy with high-energy (4-25 MeV) electron beams, scattered radiation from the electron applicator influences the dose distribution in the patient. In most currently available treatment planning systems for radiotherapy this component is not explicitly included and handled only by a slight change of the intensity of the primary beam. The scattered radiation from an applicator changes with the field size and distance from the applicator. The amount of scattered radiation is dependent on the applicator design and on the formation of the electron beam in the treatment head. Electron applicators currently applied in most treatment machines are essentially a set of diaphragms, but still do produce scattered radiation. This paper investigates the present level of scattered dose from electron applicators, and as such provides an extensive set of measured data. The data provided could for instance serve as example input data or benchmark data for advanced treatment planning algorithms which employ a parametrized initial phase space to characterize the clinical electron beam. Central axis depth dose curves of the electron beams have been measured with and without applicators in place, for various applicator sizes and energies, for a Siemens Primus, a Varian 2300 C/D and an Elekta SLi accelerator. Scattered radiation generated by the applicator has been found by subtraction of the central axis depth dose curves, obtained with and without applicator. Scattered radiation from Siemens, Varian and Elekta electron applicators is still significant and cannot be neglected in advanced treatment planning. Scattered radiation at the surface of a water phantom can be as high as 12%. Scattered radiation decreases almost linearly with depth. Scattered radiation from Varian applicators shows clear dependence on beam energy. The Elekta applicators produce less scattered radiation than those of Varian and Siemens, but feature a higher effective angular variance. The scattered

  7. Space electronics: radiation belts set new challenges

    Leray, J.L.; Barillot, C.; Boudenot, J.C.

    1999-01-01

    Telecommunications satellites have been in use since 1962 with the first satellite network (constellation) coming into operation in 1966. GPS systems have been available since the mid seventies. Until now, all these systems have avoided orbits which lie within the radiation belts. The latest constellation projects, offering much wider bandwidths, need to use orbits between 1500 and 2000 km, where the proton density is at its highest. The vulnerability of future generations of components can be predicted by extrapolating the behaviour of current devices. Screening is not a viable option due to cost and weight limitations in satellite applications. As a result, satellite and component manufacturers are seeking new methods of hardening components or making them more radiation tolerant in an environment where the radiation levels are ten times those currently experiences. (authors)

  8. Scattered radiation from applicators in clinical electron beams.

    Battum, L.J. van; Zee, W. van der; Huizenga, H.

    2003-01-01

    In radiotherapy with high-energy (4-25 MeV) electron beams, scattered radiation from the electron applicator influences the dose distribution in the patient. In most currently available treatment planning systems for radiotherapy this component is not explicitly included and handled only by a slight

  9. Resonant Raman scattering in Nd2O3 and the electronic structure of Sr2RuO4 studied by synchrotron radiation excitation

    Ederer, D. L.

    1998-01-01

    This paper is intended to illustrate two points. The first being the extensive growth of resonant Raman soft x-ray scattering due to the emergence of third-generation x-ray sources. With these sources, the ubiquitous presence of Raman scattering near the 3d and 4d ionization thresholds has been used to elucidate the excitation process in a number of rare earth and transition metal compounds. Such scattering can produce dramatic changes in the emission spectrum, as we show in our example of inelastic scattering at the 3d threshold of Nd 2 O 3 . Photon-in photon-out soft x-ray spectroscopy is adding a new dimension to soft x-ray spectroscopy by providing many opportunities for exciting research, especially at third-generation synchrotrons light sources. Second, it is very effective to use theory and experiment to characterize the electronic properties of materials. In particular we confirmed in-plane oxygen-ruthenium bonding in Sr 2 RuO 4 , this first copperless perovskite superconductor, by analyses using calculations, soft x-ray emission spectroscopy (SXE) and photoelectron spectroscopy (PES). Measurements of this type illustrate the importance of combining SXE and PES measurements with theoretical calculations

  10. Structured thermal surface for radiative camouflage.

    Li, Ying; Bai, Xue; Yang, Tianzhi; Luo, Hailu; Qiu, Cheng-Wei

    2018-01-18

    Thermal camouflage has been successful in the conductive regime, where thermal metamaterials embedded in a conductive system can manipulate heat conduction inside the bulk. Most reported approaches are background-dependent and not applicable to radiative heat emitted from the surface of the system. A coating with engineered emissivity is one option for radiative camouflage, but only when the background has uniform temperature. Here, we propose a strategy for radiative camouflage of external objects on a given background using a structured thermal surface. The device is non-invasive and restores arbitrary background temperature distributions on its top. For many practical candidates of the background material with similar emissivity as the device, the object can thereby be radiatively concealed without a priori knowledge of the host conductivity and temperature. We expect this strategy to meet the demands of anti-detection and thermal radiation manipulation in complex unknown environments and to inspire developments in phononic and photonic thermotronics.

  11. Direction selective structural-acoustic coupled radiator

    Seo, Hee-Seon; Kim, Yang-Hann

    2005-04-01

    This paper presents a method of designing a structural-acoustic coupled radiator that can emit sound in the desired direction. The structural-acoustic coupled system is consisted of acoustic spaces and wall. The wall composes two plates and an opening, and the wall separates one space that is highly reverberant and the other that is unbounded without any reflection. An equation is developed that predicts energy distribution and energy flow in the two spaces separated by the wall, and its computational examples are presented including near field acoustic characteristics. To design the directional coupled radiator, Pareto optimization method is adapted. An objective is selected to maximize radiation power on a main axis and minimize a side lobe level and a subjective is selected direction of the main axis and dimensions of the walls geometry. Pressure and intensity distribution of the designed radiator is also presented.

  12. Instructional Approach to Molecular Electronic Structure Theory

    Dykstra, Clifford E.; Schaefer, Henry F.

    1977-01-01

    Describes a graduate quantum mechanics projects in which students write a computer program that performs ab initio calculations on the electronic structure of a simple molecule. Theoretical potential energy curves are produced. (MLH)

  13. Development and qualification of materials and processes for radiation shielding of Galileo spacecraft electronic components

    Hribar, F.; Bauer, J.L.; O'Donnell, T.P.

    1990-01-01

    Several materials and processing methods were evaluated for use on the JPL Galileo spacecraft in the area of radiation shielding for electronics. Development and qualification activities involving an aluminum structural laminate are described. These activities included requirements assessment, design tradeoffs, materials selection, adhesive bonding development, mechanical properties measurements, thermal stability assessment, and nondestructive evaluation. This paper presents evaluation of three adhesives for bonding tantalum to aluminum. The concept of combining a thin sheet of tantalum with two outer aluminum face sheets using adhesive bonding was developed successfully. This radiation shield laminate also provides a structural shear plate for mounting electronic assemblies

  14. FEL radiation power available in electron storage rings

    Miyahara, Yoshikazu

    1994-01-01

    FEL radiation power available in electron storage rings was studied in the small signal regime in considering the increase of the energy spread of the electron beam caused by the FEL interaction and the decrease of the FEL gain with the increase of the energy spread in addition to the radiation damping and the quantum excitation. All these effects were considered separately, and combined with FEL power equations. The radiation power available was expressed explicitly with the parameters of the storage ring, the wiggler and the mirrors. The transient process of FEL lasing is simulated with the power equations. A rough estimation is made of the radiation power available by the FEL at different beam energies, and optimization of FEL parameters for a higher radiation power is discussed. ((orig.))

  15. Silicon radiation detector analysis using back electron beam induced current

    Guye, R.

    1987-01-01

    A new technique for the observation and analysis of defects in silicon radiation detectors is described. This method uses an electron beam from a scanning electron microscope (SEM) impinging on the rear side of the p + n junction of the silicon detector, which itself is active and detects the electron beam induced current (EBIC). It is shown that this current is a sensitive probe of localized trapping centers, either at the junction surface or somewhere in the volume of the silicon crystal. (orig.)

  16. Radiation Testing of Electronics for the CMS Endcap Muon System

    INSPIRE-00070357; Celik, A.; Durkin, L.S.; Gilmore, J.; Haley, J.; Khotilovich, V.; Lakdawala, S.; Liu, J.; Matveev, M.; Padley, B.P.; Roberts, J.; Roe, J.; Safonov, A.; Suarez, I.; Wood, D.; Zawisza, I.

    2013-01-01

    The electronics used in the data readout and triggering system for the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC) particle accelerator at CERN are exposed to high radiation levels. This radiation can cause permanent damage to the electronic circuitry, as well as temporary effects such as data corruption induced by Single Event Upsets. Once the High Luminosity LHC (HL-LHC) accelerator upgrades are completed it will have five times higher instantaneous luminosity than LHC, allowing for detection of rare physics processes, new particles and interactions. Tests have been performed to determine the effects of radiation on the electronic components to be used for the Endcap Muon electronics project currently being designed for installation in the CMS experiment in 2013. During these tests the digital components on the test boards were operating with active data readout while being irradiated with 55 MeV protons. In reactor tests, components were exposed to 30 years equivalent levels o...

  17. Radiation of Electron in the Field of Plane Light Wave

    Zelinsky, A.; Drebot, I.V.; Grigorev, Yu.N.; Zvonareva, O.D.; Tatchyn, R.

    2006-01-01

    Results of integration of a Lorentz equation for a relativistic electron moving in the field of running, plane, linear polarized electromagnetic wave are presented in the paper. It is shown that electron velocities in the field of the wave are almost periodic functions of time. For calculations of angular spectrum of electron radiation intensity expansion of the electromagnetic field in a wave zone into generalized Fourier series was used. Expressions for the radiation intensity spectrum are presented in the paper. Derived results are illustrated for electron and laser beam parameters of NSC KIPT X-ray generator NESTOR. It is shown that for low intensity of the interacting electromagnetic wave the results of energy and angular spectrum calculations in the frame of classical electrodynamics completely coincide with calculation results produced using quantum electrodynamics. Simultaneously, derived expressions give possibilities to investigate dependence of energy and angular Compton radiation spectrum on phase of interaction and the interacting wave intensity

  18. Ionizing radiations in Italian health care structures

    Fizzano, M.R.; Frusteri, L.

    2006-01-01

    The Council of the European Union has completely renewed the framework regarding radiation protection by adopting some directives: Directive 97/43 EURATOM lays down the general principles of the radiation protection of individuals undergoing exposure to ionising radiations related to medical exposures, as a supplement of Directive 96/29 EURATOM laying down the basic safety standards for the protection of the health of workers and the general public against the dangers arising from ionising radiations.The incorporation into Italian legislation of the European Community directives on the improvement of health and safety at work has promoted a vast effort in order to revise the surveillance approach in many facilities, including hospitals. In Italy, safety law is referred to every workplace; anyway the use of ionising radiations is ruled by specific laws. So in the health care structures it is necessary integrating both the laws and this process is often difficult to carry on. The Italian Legislative Decree 230/95, one the main laws that aim to protect workers against ionising radiations, introduced Directive 96/29/EURATOM. This Decree asks that a doctor and a technical expert analyse the workplace and classify area and workers in according to dose of ionising radiation established by law. The Italian Legislative Decree 626/94 asks that risk analysis in general is made by doctor and specialist in risk. So, in case of risk from ionising radiation, all these figures have to cooperate in order to make an evaluation risk document. (N.C.)

  19. Ionizing radiations in Italian health care structures

    Fizzano, M.R.; Frusteri, L. [Technical Advisory Dept. for Risk Assessment and Prevention, Italian Workers Compensation Authority, Rome (Italy)

    2006-07-01

    The Council of the European Union has completely renewed the framework regarding radiation protection by adopting some directives: Directive 97/43 EURATOM lays down the general principles of the radiation protection of individuals undergoing exposure to ionising radiations related to medical exposures, as a supplement of Directive 96/29 EURATOM laying down the basic safety standards for the protection of the health of workers and the general public against the dangers arising from ionising radiations.The incorporation into Italian legislation of the European Community directives on the improvement of health and safety at work has promoted a vast effort in order to revise the surveillance approach in many facilities, including hospitals. In Italy, safety law is referred to every workplace; anyway the use of ionising radiations is ruled by specific laws. So in the health care structures it is necessary integrating both the laws and this process is often difficult to carry on. The Italian Legislative Decree 230/95, one the main laws that aim to protect workers against ionising radiations, introduced Directive 96/29/EURATOM. This Decree asks that a doctor and a technical expert analyse the workplace and classify area and workers in according to dose of ionising radiation established by law. The Italian Legislative Decree 626/94 asks that risk analysis in general is made by doctor and specialist in risk. So, in case of risk from ionising radiation, all these figures have to cooperate in order to make an evaluation risk document. (N.C.)

  20. Electron conductance in curved quantum structures

    Willatzen, Morten; Gravesen, Jens

    2010-01-01

    is computationally fast and provides direct (geometrical) parameter insight as regards the determination of the electron transmission coefficient. We present, as a case study, calculations of the electron conductivity of a helically shaped quantum-wire structure and discuss the influence of the quantum......A differential-geometry analysis is employed to investigate the transmission of electrons through a curved quantum-wire structure. Although the problem is a three-dimensional spatial problem, the Schrodinger equation can be separated into three general coordinates. Hence, the proposed method...

  1. Track structure theory in radiobiology and in radiation detection

    Katz, R.

    1978-01-01

    The response of biological cells, and many physical radiation and track detectors to ionizing radiations and to energetic heavily ionizing particles, results from the secondary and higher generation electrons ejected from the atoms and molecules of the detector by the incident primary radiation. The theory uses a calculation of the radial distribution of local dose deposited by secondary electrons (delta-rays) from an energetic heavy ion as a transfer function, relating the dose-response relation measured (or postulated) for a particular detector in a uniform radiation field (gamma-rays) to obtain the radial distribution in response about the ion's path, and thus the structure of the track of a particle. Subsequent calculations yield the response of the detector to radiation fields of arbitrary quality. The models which have been used for detector response arise from target theory, and are of the form of statistical models called multi-hit or multi-target detectors, in which it is assumed that there are sensitive elements (emulsion grains, or biological cell nuclei) which may require many hits (emulsion grains) or single hits in different targets (say, cellular chromosomes) in order to produce the observed end-point. Recent work has demonstrated that many-hit physical detectors do exist. From both emulsion sensitometry and from the structure of tracks of heavy ions, it can be shown that emulsion-developer combinations exist which yield many-hit response. There is also some evidence that the supralinearity in thermoluminescent dosimeters arises from a mixture of 1-hit and 2-hit response, perhaps of different trap structures within the same TLD crystal. These detectors can be expected to mimic the response of biological cells to radiations of different quality. Their patterns of response may help us to understand better the structure of particle tracks in SSNTD's. (author)

  2. Electromagnetic radiation of electrons in corrugated graphene

    Ktitorov, S. A., E-mail: ktitorov@mail.ioffe.ru; Myhamadiarov, R. I. [Russian Academy of Sciences, Ioffe Physical–Technical Institute (Russian Federation)

    2016-08-15

    Bremsstrahlung in corrugated single-layer graphene in the presence of a ballistic transport current is analyzed. Radiation of a similar nature is observed in undulators and wigglers. Regular and chaotic corrugations (ripples) are considered. It is shown that the quadratic relation between the Monge membrane function and the synthetic calibration field leads to the appearance of a central peak in the radiation spectral density. Possible formation mechanisms of single-layer graphene corrugation are proposed. In one case, the corrugation is considered as an incommensurate superstructure in a two-dimensional crystal, resulting from instability developing in the optical phonon subsystem with the formation of a periodic soliton train. Corrugation results from the interaction of subsystems. Another possible mechanism consists in instability of the membrane flat state due to strong fluctuations characteristic of two-dimensional systems.

  3. Development of methods for determining organic free radical structures by electron spin resonance and application to the radiation chemistry of nucleic acid model compounds

    Fouse, G.W. Jr.

    1977-01-01

    This project was undertaken with the objective of developing more efficient and reliable methods for the analysis of free radicals in organic single crystals. A technique was developed for the rapid calculation of single crystal ESR line positions and intensities. This method, which avoids the time-consuming matrix operations required by conventional methods, has been incorporated into a computer program for determining ESR parameters by the least-squares fitting of digitized ESR spectra. This program has been used to analyze complex spectra arising from a . CH 2 -CH 2 -O-PO 3 H - radical trapped in O-phosphorylethanolamine. A method was developed for the estimation of variance and covariance of eigenvectors and eigenvalues of experimentally-determined tensors. This error analysis is quite general, and may be applied to any tensors which can be determined by the non-linear least-squares fitting of ESR data. Monte-Carlo simulations have been employed to estimate the limitations of the approximation method. This error analysis has been included in the analysis of two phosphite radicals, - O 2 -P-OX, found in single crystals of O-phosphorylethanolamine. To aid in the formulation and evaluation of free radical models, a generalized method for the calculation of theoretically-expected hyperfine coupling tensors for arbitrary radical models was developed. Tensors are calculated for a furan-type radical which may be found in 5' dCMP. These calculated tensors are compared with tensors determined by an ENDOR experiment. Two ENDOR studies were done, one in 5' dCMP, the other in L-asparagine. The observed radical in 5' dCMP is allylic, characterized by coupling to three α-hydrogens. In L-asparagine, the dominant room-temperature radical has the form CO(NH 2 )CHCH(N + H 3 )CO 2 - . In both these studies, a series of molecular orbital calculations were performed as a means of substantiating the postulated radical structures

  4. Radiation processing of liquid with low energy electron accelerator

    Makuuchi, Keizo

    2003-01-01

    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 γ-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 γ-ray should be carried out. (author)

  5. Radiation processing of liquid with low energy electron accelerator

    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)

  6. Radiation testing of electronics for the CMS endcap muon system

    Bylsma, B. [Ohio State University (United States); Cady, D.; Celik, A. [Texas A and M University, College Station, TX 77843 (United States); Durkin, L.S. [Ohio State University (United States); Gilmore, J., E-mail: gilmore@tamu.edu [Texas A and M University, College Station, TX 77843 (United States); Haley, J. [Northeastern University (United States); Khotilovich, V.; Lakdawala, S. [Texas A and M University, College Station, TX 77843 (United States); Liu, J.; Matveev, M.; Padley, B.P.; Roberts, J. [Rice University (United States); Roe, J.; Safonov, A.; Suarez, I. [Texas A and M University, College Station, TX 77843 (United States); Wood, D. [Northeastern University (United States); Zawisza, I. [Texas A and M University, College Station, TX 77843 (United States)

    2013-01-11

    The electronics used in the data readout and triggering system for the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC) particle accelerator at CERN are exposed to high radiation levels. This radiation can cause permanent damage to the electronic circuitry, as well as temporary effects such as data corruption induced by Single Event Upsets. Once the High Luminosity LHC (HL-LHC) accelerator upgrades are completed it will have five times higher instantaneous luminosity than LHC, allowing for detection of rare physics processes, new particles and interactions. Tests have been performed to determine the effects of radiation on the electronic components to be used for the Endcap Muon electronics project currently being designed for installation in the CMS experiment in 2013. During these tests the digital components on the test boards were operating with active data readout while being irradiated with 55 MeV protons. In reactor tests, components were exposed to 30 years equivalent levels of neutron radiation expected at the HL-LHC. The highest total ionizing dose (TID) for the muon system is expected at the innermost portion of the CMS detector, with 8900 rad over 10 years. Our results show that Commercial Off-The-Shelf (COTS) components selected for the new electronics will operate reliably in the CMS radiation environment.

  7. Radiation testing of electronics for the CMS endcap muon system

    Bylsma, B.; Cady, D.; Celik, A.; Durkin, L. S.; Gilmore, J.; Haley, J.; Khotilovich, V.; Lakdawala, S.; Liu, J.; Matveev, M.; Padley, B. P.; Roberts, J.; Roe, J.; Safonov, A.; Suarez, I.; Wood, D.; Zawisza, I.

    2013-01-01

    The electronics used in the data readout and triggering system for the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC) particle accelerator at CERN are exposed to high radiation levels. This radiation can cause permanent damage to the electronic circuitry, as well as temporary effects such as data corruption induced by Single Event Upsets. Once the High Luminosity LHC (HL-LHC) accelerator upgrades are completed it will have five times higher instantaneous luminosity than LHC, allowing for detection of rare physics processes, new particles and interactions. Tests have been performed to determine the effects of radiation on the electronic components to be used for the Endcap Muon electronics project currently being designed for installation in the CMS experiment in 2013. During these tests the digital components on the test boards were operating with active data readout while being irradiated with 55 MeV protons. In reactor tests, components were exposed to 30 years equivalent levels of neutron radiation expected at the HL-LHC. The highest total ionizing dose (TID) for the muon system is expected at the innermost portion of the CMS detector, with 8900 rad over 10 years. Our results show that Commercial Off-The-Shelf (COTS) components selected for the new electronics will operate reliably in the CMS radiation environment.

  8. Electron cascades in sensors for optical detection of ionizing radiation

    London, Richard A.; Lowry, Mark E.; Vernon, Stephen P.; Stewart, Richard E.

    2013-01-01

    A new class of high-speed detectors, called RadOptic detectors, measures ionizing radiation incident on a transparent semiconductor by sensing changes in the refractive index with an optical probe beam. We describe the role of radiation-initiated electron cascades in setting the sensitivity and the spatial and temporal resolution of RadOptic detectors. We model electron cascades with both analytical and Monte Carlo computational methods. We find that the timescale for the development of an electron cascade is less than of order 100 fs and is not expected to affect the time response of a detector. The characteristic size of the electron cloud is typically less than 2 μm, enabling high spatial resolution in imaging systems. The electron-hole pair density created by single x-rays is much smaller than the saturation density and, therefore, single events should not saturate the detector

  9. Effects of radiations on electronic components - Course IN2P3, release 6

    2007-01-01

    As many off-the-shelf electronic components are now present onboard satellites, launchers and planes, this course proposes an overview of effects radiations can have on these components, notably in space applications. A first part proposes an overview of radiative environments, and more particularly presents the space radiative environment (solar wind, solar flares, cosmic radiation, radiation belts). It also presents the atmospheric and Earth radiative environment due to cosmic radiation, the alpha radiation (origin of particles, particle flow), the radiative environment within an accelerator. The second part addresses the effects of these radiative environments on electronic components, and the associated standards and tests. It addresses cumulative effects and proposes a detailed analysis of the effects of an ionizing dose on a MOS transistor, an analysis of the effects of ionising dose rate on a bipolar NPN or PNP vertical or lateral transistor, an analysis of the effects of atomic displacements, and a discussion of structure modifications. The next part describes various single events: the Single Event Upset (SEU) and the Multiple Bit Upset (MBU) in the case of a SRAM, the SEL (Single Event Latch-up) phenomenon, the SEGR (Single Event Gate Rupture) phenomenon in the case of a Power MOSFET, and the SEB (Single Event Burnout) phenomenon in the case of a Power MOSFET

  10. Overview of nuclear structure with electrons

    Geesaman, D. F.

    1999-01-01

    Following a broad summary of the author's view of nuclear structure in 1974, he will discuss the key elements they have learned in the past 25 years from the research at the M.I.T. Bates Linear Accelerator center and its sister electron accelerator laboratories. Electron scattering has provided the essential measurements for most of the progress. The future is bright for nuclear structure research as their ability to realistically calculate nuclear structure observables has dramatically advanced and they are increasingly able to incorporate an understanding of quantum chromodynamics into their picture of the nucleus

  11. Radiative interaction of electrons in a short electron bunch moving in an undulator

    Saldin, E. L.; Schneidmiller, E. A.; Yurkov, M. V.

    1999-01-01

    This paper presents investigations of the longitudinal radiative force in an electron bunch. The model of the electron bunch assumes line density distribution. General formulas are presented for the calculation of the radiative force in the bunch moving along an arbitrary small-angle trajectory. The case of a motion in an undulator (wiggler) has been studied in detail. Analytical solutions are obtained for a rectangular and for a Gaussian bunch shape. It is shown that the rate of the bunch energy loss due to the radiative interaction is equal to the power of the coherent radiation in the far zone. Numerical estimations presented in the paper show that the effects of induced energy spread due to the radiative interaction can be important for free electron lasers operating in the infrared wavelength range

  12. Human enamel structure studied by high resolution electron microscopy

    Wen, S.L.

    1989-01-01

    Human enamel structural features are characterized by high resolution electron microscopy. The human enamel consists of polycrystals with a structure similar to Ca10(PO4)6(OH)2. This article describes the structural features of human enamel crystal at atomic and nanometer level. Besides the structural description, a great number of high resolution images are included. Research into the carious process in human enamel is very important for human beings. This article firstly describes the initiation of caries in enamel crystal at atomic and unit-cell level and secondly describes the further steps of caries with structural and chemical demineralization. The demineralization in fact, is the origin of caries in human enamel. The remineralization of carious areas in human enamel has drawn more and more attention as its potential application is realized. This process has been revealed by high resolution electron microscopy in detail in this article. On the other hand, the radiation effects on the structure of human enamel are also characterized by high resolution electron microscopy. In order to reveal this phenomenon clearly, a great number of electron micrographs have been shown, and a physical mechanism is proposed. 26 references

  13. Chemical structure and radiation stability of solid crystalline antibiotics: thiamphenicol and chloramphenicol

    Varshney, Lalit; Soe Nwe

    1997-01-01

    Antibiotics in solid state show significant radiation resistance and some of them are exposed to gamma or electron beam irradiation for sterilization. Even small radiation degradation in solid state antibiotics is not desirable. Two antibiotics namely thiamphenicol (TPL) and chloramphenicol (CPL) having similar chemical and solid state structure were irradiated at different graded radiation doses to study their stability. Differential scanning calorimetry (DSC) was used to evaluate purity, entropy of radiation processing, heat of fusion and melting point. (author). 3 refs., 1 tab

  14. Spectral and electronic measurements of solar radiation

    Suzuki, Mamoru; Hanyu, Mitsuhiro

    1977-01-01

    The spectral data of solar radiation are necessary if detailed discussion is intended in relation to the utilization of solar energy. Since those data have not been fully prepared so far, a measuring equipment developed in Electro-technical Laboratory to obtain those data is described. The laboratory is now continuing the measurement at the wavelength of 0.3 μm to 1.1 μm. The equipment employs the system to always calibrate with the standard light source, it can measure both the direct light of the sun only and the sun light including sky light, and it enables to obtain the value based on the secondary standard of spectral illumination intensity established by the laboratory. The solar spectral irradiance is determined with the current readings of photomultiplier in the standard light source and the sun-light measurements at a wavelength and with the spectral illumination intensity from the standard light source. In order to practice such measurement many times at various wavelengths, control of the equipment, data collection, computation, drawing and listing are performed by a microcomputer. As an example, the data on Sept. 10, 1976, are shown comparing the graphs at three different hours. It can be well observed that the transmissivity attenuates with shorter wavelength, and the transmissivity in near infra-red region changes greatly due to the absorption of radiation by water vapour. (Wakatsuki, Y.)

  15. Small compact pulsed electron source for radiation technologies

    Korenev, Sergey

    2002-01-01

    The small compact pulsed electron source for radiation technologies is considered in the report. The electron source consists of pulsed high voltage Marx generator and vacuum diode with explosive emission cathode. The main parameters of electron source are next: kinetic energy is 100-150 keV, beam current is 5-200 A and pulse duration is 100-400 nsec. The distribution of absorbed doses in irradiated materials is considered. The physical feasibility of pulsed low energy electron beam for applications is considered

  16. Radiation from silver films bombarded by low-energy electrons

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

    1980-01-01

    Emission spectra from Ag films irradiated by low energy electrons (20-1500 eV) have been measured, and the results compared with theory. For relatively smooth films, two peaks in the spectra are resolved. One at 3.73 eV, the volume plasmon energy, is attributed to transition radiation and/or bremsstrahlung. 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 surface plasmons. For rough films, the roughness-coupled radiation dominates the emission. In addition to spectral shapes, the polarization of the radiation and its intensity as a function of electron energy were measured. The experimental results are compared with new calculations of roughness-coupled emission which account for most of our observations. They indicate that high wavevector roughness components play the dominant role in the emission process. (orig.)

  17. Propagation of synchrotron radiation through nanocapillary structures

    Bjeoumikhov, A.; Bjeoumikhova, S.; Riesemeier, H.; Radtke, M.; Wedell, R.

    2007-01-01

    The propagation of synchrotron radiation through nanocapillary structures with channel sizes of 200 nm and periods in the micrometer size has been studied experimentally. It was shown that the propagation through individual capillary channels has a mode formation character. Furthermore it was shown that during the propagation through capillary channels the coherence of synchrotron radiation is partially conserved. Interference of beams propagating through different capillary channels is observed which leads to a periodically modulated distribution of the radiation intensity in a plane far from the exit of the structure. These investigations are of high relevance for the understanding of X-ray transmission through nanocapillaries and the appearance of wave properties at this size scale

  18. Fiber structural analysis by synchrotron radiation

    Kojima, J I; Kikutani, T

    2003-01-01

    Topics of fiber structural analysis by synchrotron radiation are explained. There are only three synchrotron radiation facilities in the world, SPring-8 (Super Photon ring-8) in Japan, APS (Advanced Photon Source) in U.S.A. and ESRF (European Synchrotron Radiation Facility) in France. Online measurement of melt spinning process of PET and Nylon6 is explained in detail. Polypropylene and PBO (poly-p-phenylenebenzobisoxazole) was measured by WAXD (Wide Angle X-ray Diffraction)/SAXS (Small Angle X-ray Scattering) at the same time. Some examples of measure of drawing process of fiber are described. The structure formation process of spider's thread was measured. Micro beam of X-ray of synchrotron facility was improved and it attained to 65nm small angle resolving power by 10 mu m beamsize. (S.Y.)

  19. Compact Radiative Control Structures for Millimeter Astronomy

    Brown, Ari D.; Chuss, David T.; Chervenak, James A.; Henry, Ross M.; Moseley, s. Harvey; Wollack, Edward J.

    2010-01-01

    We have designed, fabricated, and tested compact radiative control structures, including antireflection coatings and resonant absorbers, for millimeter through submillimeter wave astronomy. The antireflection coatings consist of micromachined single crystal silicon dielectric sub-wavelength honeycombs. The effective dielectric constant of the structures is set by the honeycomb cell geometry. The resonant absorbers consist of pieces of solid single crystal silicon substrate and thin phosphorus implanted regions whose sheet resistance is tailored to maximize absorption by the structure. We present an implantation model that can be used to predict the ion energy and dose required for obtaining a target implant layer sheet resistance. A neutral density filter, a hybrid of a silicon dielectric honeycomb with an implanted region, has also been fabricated with this basic approach. These radiative control structures are scalable and compatible for use large focal plane detector arrays.

  20. Radiation effects on structural ceramics in fusion

    Hopkins, G.R.; Price, R.J.; Trester, P.W.

    1986-01-01

    Ceramics are required to serve in a conventional role as electrical and thermal insulators and dielectrics in fusion power reactors. In addition, certain ceramic materials can play a unique structural role in fusion power reactors by virtue of their very low induced radioactivity from fusion neutron capture. The aspects of safety, long-term radioactive waste management, and personnel access for maintenance and repair can all be significantly improved by applying the low-activation ceramics to the structural materials of the first-wall and blanket regions of a fusion reactor. Achievement of long service life at high structural loads and thermal stresses on the materials exposed to high-radiation doses presents a critical challenge for fusion. In this paper, we discuss radiation effects on structural ceramics for fusion application

  1. Measurement of microwave radiation from electron beam in the atmosphere

    Ohta, I.S.; Akimune, H. [Faculty of Science and Engineering, Konan University, Kobe 658-8501 (Japan); Fukushima, M.; Ikeda, D. [Institute of Cosmic Ray Research, University of Tokyo, Kashiwa, Chiba 277-8582 (Japan); Inome, Y. [Faculty of Science and Engineering, Konan University, Kobe 658-8501 (Japan); Matthews, J.N. [University of Utah, Salt Lake City, UT 4112-0830 (United States); Ogio, S. [Graduate School of Science, Osaka City University, Osaka 558-8585 (Japan); Sagawa, H. [Institute of Cosmic Ray Research, University of Tokyo, Kashiwa, Chiba 277-8582 (Japan); Sako, T. [Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya 464-8601 (Japan); Shibata, T. [High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801 (Japan); Yamamoto, T., E-mail: tokonatu@konan-u.ac.jp [Faculty of Science and Engineering, Konan University, Kobe 658-8501 (Japan)

    2016-02-21

    We report the use of an electron light source (ELS) located at the Telescope Array Observatory in Utah, USA, to measure the isotropic microwave radiation from air showers. To simulate extensive air showers, the ELS emits an electron beam into the atmosphere and a parabola antenna system for the satellite communication is used to measure the microwave radiation from the electron beam. Based on this measurement, an upper limit on the intensity of a 12.5 GHz microwave radiation at 0.5 m from a 10{sup 18} eV air shower was estimated to be 3.96×10{sup −16} W m{sup −2} Hz{sup −1} with a 95% confidence level.

  2. Radiation-Induced Graft Polymerization: Gamma Radiation and Electron Beam Technology for Materials Development

    Madrid, Jordan F.; Cabalar, Patrick Jay; Lopez, Girlie Eunice; Abad, Lucille V.

    2015-01-01

    The formation of functional hybrid materials by attaching polymer chains with advantageous tailored properties to the surface of a base polymer with desirable bulk character is an attractive application of graft copolymerization. Radiation-induced graft polymerization (RIGP) has been a popular approach for surface modification of polymers because of its merits over conventional chemical processes. RIGP, which proceeds primarily via free radical polymerization process, has the advantages such as simplicity, low cost, control over process and adjustment of the materials composition and structure. RIGP can be performed using either electron beam or gamma radiation and it can be applied to both synthetic and natural polymers. These merits make RIGP a popular research topic worldwide. Moreover, the materials synthesized and produced via RIGP has found applications, and were proposed to produce continuous impact, in the fields of medicine, agriculture, pollution remediation, rare earth and valuable metals recovery, fuel cell membrane synthesis and catalysis to name a few. From 2012 our group has performed electron beam and gamma radiation-induced graft polymerization of various monomers onto polymers of natural and synthetic origins (e.g. monomers - glycidyl methacrylate, styrene, acrylonitrile, N,N-dimethylaminoethyl methacrylate; base polymers – polyethylene/polypropylene nonwoven fabric, polypropylene nonwoven fabric pineapple fibers, cellulose nonwoven fabric microcrystalline cellulose). We tested these grafted materials for heavy metals (Pb, Ni, Cu) and organic molecule removal from aqueous solutions and E. coli activity (using reversible addition fragmentation chain transfer RAFT mediated grafting). The results clearly showed the success of materials modified via FIGP in these applications. Currently, we are studying the applications of grafted materials on treatment of waste waters from tanning industry, value addition to abaca nonwoven fabrics cell sheet

  3. Radiation-beam technologies of structural materials treatment

    Kalin, B.A.

    2001-01-01

    Considered in the paper are the most advanced and prospective radiation-beam technologies (RBT) for treatment of structural materials, as applied to modifying the structural-phase state in the surface layers of half-finished products and articles with the purpose to improve their service properties. Ion-beam, plasma, and ion-plasma, as well as the technologies based on the use of concentrated fluxes of energy, generated by laser radiation, high-power pulsed electron and ion beams, and high-temperature pulsed plasma fluxes are analysed. As applied to improvement of the corrosion and erosion resistance, breaking strength, friction and wear resistance, and crack resistance, the directions of the choice and the use of RBT have been considered for changes of the surface layer state by applying covers and films, and by a change of the surface topography (relief), surface structure and defects, and the element composition and phase state of materials [ru

  4. Radiation from planar channeled 5-55 GeV/c positrons and electrons

    Atkinson, M.; Sharp, P.H.; Giddings, D.; Bussey, P.J.

    1982-01-01

    The emission of radiation from 5 to 55 GeV/c planar channeled positrons and electrons passing through a 135 μ thick silicon-crystal has been investigated. The intensity of the channeling-radiation is found to be 10 to 30 times the intensity of normal bremsstrahlung. For channeled electrons no structure is found in the spectrum, whereas strong and sharp peaks are found for positrons. This peak structure is extremely sharp at 5 GeV/c and for momenta above 20 GeV/c the structure disappears. For a classical description of channeling, but using an anharmonic potential, certain energies are found for which the maximum energy of the channeling radiation is practically independent of transverse energy. The possibility of making a monoenergetic γ-source in the range of 10-100 MeV is mentioned. (orig.)

  5. Radiation-induced electron migration in nucleic acids

    Fuciarelli, A.F.; Sisk, E.C.; Miller, J.H.; Zimbrick, J.D.

    1994-01-01

    Radiation-induced electron migration along DNA is a mechanism by which randomly produced stochastic energy deposition events can lead to non-random types of damage along DNA manifested distal to the sites of the initial energy deposition. Radiation-induced electron migration in nucleic acids has been examined using oligonucleotides containing 5-bromouracil (5-BrU). Interaction of 5-BrU with solvated electrons results in release of bromide ions and formation of uracil-5-yl radicals. Monitoring either bromide ion release or uracil formation provides an opportunity to study electron migration processes in model nucleic acid systems. Using this approach we have discovered that electron migration along oligonucleotides is significantly influenced by the base sequence and strandedness. Migration along 7 base pairs in oligonucleotides containing guanine bases was observed for oligonucleotides irradiated in solution, which compares with mean migration distances of 6-10 bp for Escherichia coli DNA irradiated in solution and 5.5 bp for E. coli DNA irradiated in cells. Evidence also suggests that electron migration can occur preferentially in the 5' to 3' direction along a double-stranded oligonucleotide containing a region of purine bases adjacent to the 5-BrU moiety. Our continued efforts will provide information regarding the contribution of electron transfer along DNA to formation of locally multiply damaged sites created in DNA by exposure to ionizing radiation. (Author)

  6. Protonated serotonin: Geometry, electronic structures and photophysical properties

    Omidyan, Reza; Amanollahi, Zohreh; Azimi, Gholamhassan

    2017-07-01

    The geometry and electronic structures of protonated serotonin have been investigated by the aim of MP2 and CC2 methods. The relative stabilities, transition energies and geometry of sixteen different protonated isomers of serotonin have been presented. It has been predicted that protonation does not exhibit essential alteration on the S1 ← S0 electronic transition energy of serotonin. Instead, more complicated photophysical nature in respect to its neutral analogue is suggested for protonated system owing to radiative and non-radiative deactivation pathways. In addition to hydrogen detachment (HD), hydrogen/proton transfer (H/PT) processes from ammonium to indole ring along the NH+⋯ π hydrogen bond have been predicted as the most important photophysical consequences of SERH+ at S1 excited state. The PT processes is suggested to be responsible for fluorescence of SERH+ while the HD driving coordinate is proposed for elucidation of its nonradiative deactivation mechanism.

  7. Orientation acoustic radiation of electrons in silicon thick crystal

    Alejnik, A.N.; Afanas'ev, S.G.; Vorob'ev, S.A.; Zabaev, V.N.; Il'in, S.I.; Kalinin, B.N.; Potylitsyn, A.P.

    1989-01-01

    Results of measuring orientation acoustic radiation of 900 and 500 MeV electrons during their movement along crystallographic axis in thick silicon crystal (h=20 mm thickness) are presented for the first time. Analysis of obtained results shows that dynamic mechanism describes rather completely the main regularities of orientation dependence of the amplitude of acoustic signal occuring under electron motion near crystallographic axis of the crystal. Phenomena of orientation acoustic radiation can be also used for investigation of solid bodies. Orientation both of thin and rather thick monocrystals can be conducted on the basis of dynamic mechanism of elastic wave excitation in crystals

  8. Radiation produced by electrons incident on molecules

    Moehlman, G.R.

    1977-01-01

    The work described in this thesis deals with light intensity measurements of emission spectra (1850-9000 A) produced by a continuous or pulsed beam of monoenergetic electrons (0 - 2000 eV) incident on a variety of molecular gases like H 2 , D 2 , H 2 O, HCl, NH 3 and several hydrocarbons. The emission spectra are dominated by fluorescence from excited fragments produced via dissociative excitation, besides fluorescence from excited parent molecules themselves. The experimental results thus obtained are expressed in terms of emission cross sections and lifetimes

  9. Electronic modulation of infrared radiation in graphene plasmonic resonators.

    Brar, Victor W; Sherrott, Michelle C; Jang, Min Seok; Kim, Seyoon; Kim, Laura; Choi, Mansoo; Sweatlock, Luke A; Atwater, Harry A

    2015-05-07

    All matter at finite temperatures emits electromagnetic radiation due to the thermally induced motion of particles and quasiparticles. Dynamic control of this radiation could enable the design of novel infrared sources; however, the spectral characteristics of the radiated power are dictated by the electromagnetic energy density and emissivity, which are ordinarily fixed properties of the material and temperature. Here we experimentally demonstrate tunable electronic control of blackbody emission from graphene plasmonic resonators on a silicon nitride substrate. It is shown that the graphene resonators produce antenna-coupled blackbody radiation, which manifests as narrow spectral emission peaks in the mid-infrared. By continuously varying the nanoresonator carrier density, the frequency and intensity of these spectral features can be modulated via an electrostatic gate. This work opens the door for future devices that may control blackbody radiation at timescales beyond the limits of conventional thermo-optic modulation.

  10. Coherent synchrotron radiation by an electron linear accelerator

    Nakazato, T.; Oyamada, M.; Niimura, N.

    1990-01-01

    Coherent effects in synchrotron radiation (SR) have been observed for the first time from 180 MeV short electron bunches of 1.7 mm using the Tohoku 300 MeV Linac. The intensity of the coherent SR was about 10 5 times as strong as that of incoherent SR at wavelengths of 0.33 to 2.0 mm. This enhancement factor roughly corresponds to the number of electrons in a bunch. The SR intensity showed a quadratic dependence on the electron beam current. The radiation was mainly polarized in the orbital plane. The possibility of induced rf in a vacuum chamber was excluded experimentally. An electron linear accelerator will be applied to a strong light source from infrared to millimeter wavelengths instead of the storage rings. The bunch length of shorter than 1 mm can be observed by the spectrum measurement of coherent SR. (author)

  11. Simulating Neutron Radiation Damage of Graphite by In-situ Electron Irradiation

    Mironov, Brindusa E; Freeman, H M; Brydson, R M D; Westwood, A V K; Scott, A J

    2014-01-01

    Radiation damage in nuclear grade graphite has been investigated using transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS). Changes in the structure on the atomic scale and chemical bonding, and the relationship between each were of particular interest. TEM was used to study damage in nuclear grade graphite on the atomic scale following 1.92×10 8 electrons nm −2 of electron beam exposure. During these experiments EELS spectra were also collected periodically to record changes in chemical bonding and structural disorder, by analysing the changes of the carbon K-edge. Image analysis software from the 'PyroMaN' research group provides further information, based on (002) fringe analysis. The software was applied to the micrographs of electron irradiated virgin 'Pile Grade A' (PGA) graphite to quantify the extent of damage from electron beam exposure

  12. Study of radiation-thermal effect of electron beam on steel and cast iron

    Machurin, E.S.; Lonchin, G.M.

    1980-01-01

    Studied is the influence of radiation-heat treatment by high energy (3-4.5 MeV) electron beam on the structure and properties of carbon steels (65G, 90KhF) and cast iron. Metallography and electron microscopy methods are used to study microstructure. It is shown that after the treatment by the electron beam there is observed noticeable structure grinding, sample fracture viscosity (even in a quenched state), increase of hardness and impact strength. The mechanism of metal heating process by electron beam is calculated and temperature field is defined in a heating region accounting for electron beam characteristics, medium and geometric factor. Theoretical data are close to experimental ones obtained in a course of determining the microhardness of irradiated samples for the cases of electron treatment duration up to 10 s

  13. Use of synchrotron radiation for electron identification at high luminosity

    Aronson, S.

    1983-01-01

    Synchrotron radiation has been used successfully to identify electrons of 10 to 30 GeV traversing a field length of 30 kG-m. Since comparable field lengths are a feature of many proposed collider detectors, and since this is an electron energy range of interest at √s approx. = 1 TeV, we consider whether such a device could be useful in the L = 10 33 environment

  14. Radiation damage studies of nuclear structural materials

    Barat, P.

    2012-01-01

    Maximum utilization of fuel in nuclear reactors is one of the important aspects for operating them economically. The main hindrance to achieve this higher burnups of nuclear fuel for the nuclear reactors is the possibility of the failure of the metallic core components during their operation. Thus, the study of the cause of the possibility of failure of these metallic structural materials of nuclear reactors during full power operation due to radiation damage, suffered inside the reactor core, is an important field of studies bearing the basic to industrial scientific views.The variation of the microstructure of the metallic core components of the nuclear reactors due to radiation damage causes enormous variation in the structure and mechanical properties. A firm understanding of this variation of the mechanical properties with the variation of microstructure will serve as a guide for creating new, more radiation-tolerant materials. In our centre we have irradiated structural materials of Indian nuclear reactors by charged particles from accelerator to generate radiation damage and studied the some aspects of the variation of microstructure by X-ray diffraction studies. Results achieved in this regards, will be presented. (author)

  15. Structural changes induced by electron irradiation

    Koike, J.; Pedraza, D.F.

    1993-01-01

    Highly oriented pyrolytic graphite was irradiated at room temperature with 300 kV electrons. Transmission electron microscopy and electron energy loss spectroscopy were employed to study the structural changes produced by irradiation. The occurrence of a continuous ring intensity in the selected area diffraction (SAD) pattern obtained on a specimen irradiated with the electron beam parallel to the c-crystallographic axis indicated that microstructural changes had occurred. However, from the SAD pattern obtained for the specimens tilted relative to the irradiation direction, it was found that up to a fluence of 1.1x10 27 e/m 2 graphite remained crystalline. An SAD pattern of a specimen irradiated with the electron beam perpendicular to the c-axis confirmed the persistence of crystalline order. High resolution electron microscopy showed that ordering along the c-axis direction remained. A density reduction of 8.9% due to irradiation was determined from the plasmon frequency shift. A qualitative model is proposed to explain these observations. A new determination of the threshold displacement energy, Ed, of carbon atoms in graphite was done by examining the appearance of a continuous ring in the SAD pattern at various electron energies. A value of 30 eV was obtained whether the incident electron beam was parallel or perpendicular to the c-axis, demonstrating that Ed is independent of the displacement direction

  16. Radiation disinfestation of used packagings: irradiation trials with electron beams

    Ignatowicz, S.; Zaedee, I.

    1994-01-01

    Used bags, sacks and other packagings are often infested with insects and mites - pest of stored products. Such packagings provide a source of infestation of a new lot or unit of agricultural products. Cleaning of repeatedly used packages is the most important preventive method. After using, the bags and sacks should be carefully beaten with a mechanical or hand beater. When pests are found, the packages should be disinfested with hot air or hot water. Larger numbers of bags are usually fumigated in a special fumigation chamber. Disinfestation by radiation processing is potentially a feasible substitute for chemical fumigation. In the present paper trials of radiation disinfestation of used bags are described and discussed. Information about using electron beams for pest disinfestation of jute and polyvinyl chloride bags (plastic bags) is provided. The absorbed dose is the most important irradiation process parameter. The lethal effects equivalent to chemical insecticides are obtained by high doses of ionizing radiation. Control of insect and/or mite infestation of the repeatedly used packagings may be secured by ionizing radiation applied at 2-3 kGy. These doses result in complete mortality of stored product pests within a few days. The radiation must penetrate deeply into the target product at sufficient level. Gamma rays and X-rays penetrate into the treated products easily but electron radiation penetrating is much lower, depending on electron energy applied. The results of this study indicate that bags made of polyvinyl chloride may be disinfested with electron beams when are created as separate units or batches up to 50 bags. Penetrability of jute bags is lower than the plastic bags. Therefore the jute bags should be irradiated with electrons as batches containing no more than 30 bags. (author)

  17. Basic mechanisms of radiation effects on electronic materials and devices

    Winokur, P.S.

    1989-01-01

    Many defense and nuclear reactor systems require complementary metal-oxide semiconductor integrated circuits that are tolerant to high levels of radiation. This radiation can result from space, hostile environments or nuclear reactor and accelerator beam environments. In addition, many techniques used to fabricate today's complex very-large-scale integration circuits expose the circuits to ionizing radiation during the process sequence. Whatever its origin, radiation can cause significant damage to integrated-circuit materials. This damage can lead to circuit performance degradation, logic upset, and even catastrophic circuit failure. This paper provides a brief overview of the basic mechanisms for radiation damage to silicon-based integrated circuits. Primary emphasis is on the effects of total-dose ionizing radiation on metal-oxide-semiconductor (MOS) structures

  18. Structural stability and electronic structure of YCu ductile ...

    We investigate the structural, elastic and electronic properties of cubic YCu intermetallic compound. Which crystallize in the CsCl- B2 type structure, the investigated using the first principle full potential linearized augmented plane wave method (FP-LAPW) within density functional Theory (DFT). We used generalized ...

  19. Track structure theory in radiobiology and in radiation detection

    Katz, R.

    1976-01-01

    The response of biological cells, and many physical radiation and track detectors to ionizing radiations, and to energetic heavily ionizing particles results from the secondary and higher generation electrons ejected from the atoms and molecules of the detector by the incident primary radiation. The models which have been used for detector response arise from target theory, and are of the form of statistical models called multi-hit or multi-target detectors, in which it is assumed that there are sensitive elements (emulsion grains, or biological cell nuclei) which may require many hits (emulsion grains) or single hits in different targets (say, cellular chromosomes) in order to produce the observed endpoint. Physically, a hit is interpreted as a 'registered event' caused by an electron passing through the sensitive site, with an efficiency which depends on the electron's speed. Some knowledge of size of the sensitive volume and of the sensitive target is required to make the transition from gamma-ray response to heavy ion response. Recent work has demonstrated that many-hit physical detectors do exist. From both emulsion sensitometry and from the structure of tracks of heavy ions, we are able to show that emulsion-developer combinations exist which yield many-hit response. There is also some evidence that the supralinearity in thermoluminescent dosimeters arises from a trap structures within the same TLD crystal. These detectors can be expected to mimic the response of biological cells to radiations of different quality. Their patterns of response may help us to understand better the structure of particle tracks in SSNTD's. (orig./ORU) [de

  20. Electron acoustic nonlinear structures in planetary magnetospheres

    Shah, K. H.; Qureshi, M. N. S.; Masood, W.; Shah, H. A.

    2018-04-01

    In this paper, we have studied linear and nonlinear propagation of electron acoustic waves (EAWs) comprising cold and hot populations in which the ions form the neutralizing background. The hot electrons have been assumed to follow the generalized ( r , q ) distribution which has the advantage that it mimics most of the distribution functions observed in space plasmas. Interestingly, it has been found that unlike Maxwellian and kappa distributions, the electron acoustic waves admit not only rarefactive structures but also allow the formation of compressive solitary structures for generalized ( r , q ) distribution. It has been found that the flatness parameter r , tail parameter q , and the nonlinear propagation velocity u affect the propagation characteristics of nonlinear EAWs. Using the plasmas parameters, typically found in Saturn's magnetosphere and the Earth's auroral region, where two populations of electrons and electron acoustic solitary waves (EASWs) have been observed, we have given an estimate of the scale lengths over which these nonlinear waves are expected to form and how the size of these structures would vary with the change in the shape of the distribution function and with the change of the plasma parameters.

  1. Radiation-hardened micro-electronics for nuclear instrumentation

    Van Uffelen, M.

    2007-01-01

    The successful development and deployment of future fission and thermonuclear fusion reactors depends to a large extent on the advances of different enabling technologies. Not only the materials need to be custom engineered but also the instrumentation, the electronics and the communication equipment need to support operation in this harsh environment, with expected radiation levels during maintenance up to several MGy. Indeed, there are yet no commercially available electronic devices available off-the-shelf which demonstrated a satisfying operation at these extremely high radiation levels. The main goal of this task is to identify commercially available radiation tolerant technologies, and to design dedicated and integrated electronic circuits, using radiation hardening techniques, both at the topological and architectural level. Within a stepwise approach, we first design circuits with discrete components and look for an equivalent integrated technology. This will enable us to develop innovative instrumentation and communication tools for the next generation of nuclear reactors, where both radiation hardening and miniaturization play a dominant role

  2. A comparison of outer electron radiation belt dropouts during solar ...

    Utilizing multiple data sources from the year 1997–2007, this study identifies radiation belt electron dropouts which are ultimately triggered when solar wind stream interfaces (SI) arrived at ... Center for Space Research, School for Physical and Chemical Sciences, North–West University, Potchefstroom 2520, South Africa.

  3. Radiation from nitrogen molecule due to electron impact

    Khare, S P; Kumar, A

    1977-01-01

    A review is presented of the experimental results of the collisional cross sections of the nitrogen molecules due to electron impact which give rise to radiations in the 3,000 Angstrom to 10,500 Angstron wavelength region. Calculations of the fluorescence efficiencies are described and are compared with experimental data. (GHT)

  4. Electronic-excitation induced radiation damage in glasses

    Vigouroux, J P

    1985-01-01

    In order to understand the microscopic nature of radiation induced defects in insulators, we have studied localization of negative and positive charges in amorphous and monocrystalline SiO2. The behaviour of these charges is linked to creation of point defects by electronic excitation. The role of intense electric fields under irradiation is pointed out.

  5. Structural and electronic parameters of ferroelectric KWOF

    Atuchin, V. V.; Gavrilova, T. A.; Kesler, V. G.; Molokeev, M. S.; Aleksandrov, K. S.

    2010-11-01

    The low-temperature ferroelectric G2 polymorph of K 3WO 3F 3 oxyfluoride is formed by chemical synthesis. The electronic parameters of G2-K 3WO 3F 3 have been measured by X-ray photoelectron spectroscopy under excitation with Al Kα radiation (1486.6 eV). Detailed spectra have been recorded for all element core levels and Auger lines. The chemical bonding effects in the WO 3F 3 and WO 6 octahedrons are considered by using the binding energy difference ΔBE(O-W)=BE(O 1s)-BE(W 4f).

  6. Acute radiation nephritis. Light and electron microscopic observations

    Kapur, S.; Chandra, R.; Antonovych, T.

    1977-01-01

    Light and electron microscopy were used to observe acute radiation nephritis. By light microscopy the changes were of fibrinoid necrosis of the arteries and arterioles with segmental necrosis of the glomerular tufts. By electron microscopy the endocapillary cells reacted by hypertrophy and hyperplasia with increase in cytoplasmic organelles. In addition, disruption of endothelial and epithelial cells from the basement membranes were seen. It is concluded that the electron microscopic changes were unique and may be helpful in differentiating the necrotizing glomerulitis seen in other conditions, especially malignant hypertension

  7. Pulsed electron accelerator for radiation technologies in the enviromental applications

    Korenev, Sergey

    1997-05-01

    The project of pulsed electron accelerator for radiation technologies in the environmental applications is considered. An accelerator consists of high voltage generator with vacuum insulation and vacuum diode with plasma cathode on the basis discharge on the surface of dielectric of large dimensions. The main parameters of electron accelerators are following: kinetic energy 0.2 - 2.0 MeV, electron beam current 1 - 30 kA and pulse duration 1- 5 microseconds. The main applications of accelerator for decomposition of wastewaters are considered.

  8. Structure of conduction electrons on polysilanes

    Ichikawa, Tsuneki [Hokkaido Univ., Sapporo (Japan); Kumagai, Jun

    1998-10-01

    The orbital structures of conduction electrons on permethylated oligosilane, Si{sub 2n}(CH{sub 3}){sub 2n+2}(n = 2 - 8), and poly(cyclohexylmethylsilane) have been determined by the electron spin-echo envelope modulation signals of the radical anions of these silanes in a deuterated rigid matrix at 77 K. The conduction electron on permethylated oligosilane is delocalized over the entire main chain, whereas that on poly(cyclohexylmethylsilane) is localized on a part of the main chain composed of about six Si atoms. Quantum-chemical calculations suggest that Anderson localization due to fluctuation of {sigma} conjugation by conformational disorder of the main chain is responsible for the localization of both the conduction electron and the hole. (author)

  9. A 600 keV electron radiation accelerator

    Zhou Youyi; Wang Xurong

    1995-01-01

    The authors describe a 600 keV two-body multi-functional electron and positive ion radiation accelerator based on a 400 keV Cockroft-Walton, Which was successfully used to accelerate electron and positive ion. Through test on coating solidification of decoration materials, such as colorful surface plaster plate and relief plate, and researches on metal plate, plastic plate, wood and paper coating decorations and radiation workmanship, as well as experiment of brach-linking by radiation for filling materials of petroleum pipings, it is proved that the device is reliable and stable in operation and reaches the pre-set design indexes and satisfies the requirements called for

  10. Electronic structure of MgB2

    Abstract. Results of ab initio electronic structure calculations on the compound MgB2 using the. FPLAPW method employing GGA for the exchange-correlation energy are presented. Total energy minimization enables us to estimate the equilibrium volume, c/a ratio and the bulk modulus, all of which are in excellent ...

  11. Electronic structure of Fe-based superconductors

    Abstract. Fe-based superconductors have drawn much attention during the last decade due to the presence of superconductivity in materials containing the magnetic element, Fe, and the coexistence of superconductivity and magnetism. Extensive study of the electronic structure of these systems suggested the dominant ...

  12. Electronic structure of Fe-based superconductors

    2015-05-29

    May 29, 2015 ... Fe-based superconductors have drawn much attention during the last decade due to the presence of superconductivity in materials containing the magnetic element, Fe, and the coexistence of superconductivity and magnetism. Extensive study of the electronic structure of these systems suggested the ...

  13. Electronic structure of MgB 2

    Results of ab initio electronic structure calculations on the compound MgB2 using the FPLAPW method employing GGA for the exchange-correlation energy are presented. Total energy minimization enables us to estimate the equilibrium volume, / ratio and the bulk modulus, all of which are in excellent agreement with ...

  14. The electronic structure of antiferromagnetic chromium

    Skriver, Hans Lomholt

    1981-01-01

    The author has used the local spin density formalism to perform self-consistent calculations of the electronic structure of chromium in the non-magnetic and commensurate antiferromagnetic phases, as a function of the lattice parameter. A change of a few per cent in the atomic radius brings...

  15. Electronic structure calculations of calcium silicate hydrates

    Sterne, P.A.; Meike, A.

    1995-11-01

    Many phases in the calcium-silicate-hydrate system can develop in cement exposed over long periods of time to temperatures above 25 C. As a consequence, chemical reactions involving these phases can affect the relative humidity and water chemistry of a radioactive waste repository that contains significant amounts of cement. In order to predict and simulate these chemical reactions, the authors are developing an internally consistent database of crystalline Ca-Si-hydrate structures. The results of first principles electronic structure calculations on two such phases, wollastonite (CaSiO 3 ) and xonotlite (Ca 6 Si 6 O 17 (OH) 2 ), are reported here. The calculated ground state properties are in very good agreement with experiment, providing equilibrium lattice parameters within about 1--1.4% of the experimentally reported values. The roles of the different types of oxygen atoms, which are fundamental to understanding the energetics of crystalline Ca-Si-hydrates are briefly discussed in terms of their electronic state densities. The good agreement with experiment for the lattice parameters and the consistency of the electronic density of states features for the two structures demonstrate the applicability of these electronic structure methods in calculating the fundamental properties of these phases

  16. Status of the Galileo interim radiation electron model

    Garrett, H. B.; Jun, I.; Ratliff, J. M.; Evans, R. W.; Clough, G. A.; McEntire, R. W.

    2003-04-01

    Measurements of the high energy, omni-directional electron environment by the Galileo spacecraft Energetic Particle Detector (EPD) were used to develop a new model of Jupiter's trapped electron radiation in the jovian equatorial plane for the range 8 to 16 Jupiter radii (1 jovian radius = 71,400 km). 10-minute averages of these data formed an extensive database of observations of the jovian radiation belts between Jupiter orbit insertion (JOI) in 1995 and 2002. These data were then averaged to provide a differential flux spectrum at 0.174, 0.304, 0.527, 1.5, 2.0, 11.0, and 31 MeV in the jovian equatorial plane as a function of radial distance. This omni-directional, equatorial model was combined with the original Divine model of jovian electron radiation to yield estimates of the out-of-plane radiation environment. That model, referred to here as the Galileo Interim Radiation Electron (or GIRE) model, was then used to calculate the Europa mission dose for an average and a 1-sigma worst-case situation. The prediction of the GIRE model is about a factor of 2 lower than the Divine model estimate over the range of 100 to 1000 mils (2.54 to 25.4 mm) of aluminum shielding, but exceeds the Divine model by about 50% for thicker shielding. The model, the steps leading to its creation, and relevant issues and concerns are discussed. While work remains to be done, the GIRE model clearly represents a significant step forward in the study of the jovian radiation environment, and it is a useful and valuable tool for estimating that environment for future space missions.

  17. Ionizing radiation changes the electronic properties of melanin and enhances the growth of melanized fungi.

    Dadachova, Ekaterina; Bryan, Ruth A; Huang, Xianchun; Moadel, Tiffany; Schweitzer, Andrew D; Aisen, Philip; Nosanchuk, Joshua D; Casadevall, Arturo

    2007-05-23

    Melanin pigments are ubiquitous in nature. Melanized microorganisms are often the dominating species in certain extreme environments, such as soils contaminated with radionuclides, suggesting that the presence of melanin is beneficial in their life cycle. We hypothesized that ionizing radiation could change the electronic properties of melanin and might enhance the growth of melanized microorganisms. Ionizing irradiation changed the electron spin resonance (ESR) signal of melanin, consistent with changes in electronic structure. Irradiated melanin manifested a 4-fold increase in its capacity to reduce NADH relative to non-irradiated melanin. HPLC analysis of melanin from fungi grown on different substrates revealed chemical complexity, dependence of melanin composition on the growth substrate and possible influence of melanin composition on its interaction with ionizing radiation. XTT/MTT assays showed increased metabolic activity of melanized C. neoformans cells relative to non-melanized cells, and exposure to ionizing radiation enhanced the electron-transfer properties of melanin in melanized cells. Melanized Wangiella dermatitidis and Cryptococcus neoformans cells exposed to ionizing radiation approximately 500 times higher than background grew significantly faster as indicated by higher CFUs, more dry weight biomass and 3-fold greater incorporation of (14)C-acetate than non-irradiated melanized cells or irradiated albino mutants. In addition, radiation enhanced the growth of melanized Cladosporium sphaerospermum cells under limited nutrients conditions. Exposure of melanin to ionizing radiation, and possibly other forms of electromagnetic radiation, changes its electronic properties. Melanized fungal cells manifested increased growth relative to non-melanized cells after exposure to ionizing radiation, raising intriguing questions about a potential role for melanin in energy capture and utilization.

  18. Trapped electronic states in YAG crystal excited by femtosecond radiation

    Zavedeev, E.V.; Kononenko, V.V.; Konov, V.I. [General Physics Institute of RAS, Moscow (Russian Federation); National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow (Russian Federation)

    2017-07-15

    The excitation of an electronic subsystem of an yttrium aluminum garnet by 800 nm femtosecond radiation was studied theoretically and experimentally. The spatio-temporal dynamics of the refractive index (n) inside the beam waist was explored by means of the pump-probe interferometric technique with a submicron resolution. The observed increase in n indicated the formation of bound electronic states relaxed for ∝ 150 ps. We showed that the experimental data agreed with the computational simulation based on the numerical solution of the nonlinear Schroedinger equation only if these transient states were considered to arise from a direct light-induced process but not from the decay of radiatively generated free-electron-hole pairs. (orig.)

  19. Dosimetry of electron and gamma radiation with DL-alanine

    Costa, Z.M. da; Campos, L.L.

    1996-01-01

    A dosimetric method based on the quantitative determination of stabilised free radicals in irradiated crystalline DL-alanine by electron spin resonance (ESR) spectroscopy was proposed as early in 1962. Since then, alanine dosemeters owing to their unique properties have been investigated by many authors and used in dosimetry of various types of radiation, namely gamma rays, electron and neutrons. Alanine is a simple aminoacid, on irradiation at room temperature predominantly free paramagnetic radicals of the type CH 3 -CH-COOH are produced. This paper reports the application of powder DL-alanine/ESR dosemeter for measurement of absorbed dose of gamma radiation from 60 Co sources and reactor nucleus and electron beams from accelerator. The obtained results give useful information about the instrumental care necessary to obtain the needed overall accuracy in determination of absorbed dose. (author)

  20. New developments in radiation protection instrumentation via active electronic methods

    Umbarger, C.J.

    1981-01-01

    New developments in electronics and radiation detectors are improving on real-time data acquisition of radiation exposure and contamination conditions. Recent developments in low power circuit designs, hybrid and integrated circuits, and microcomputers have all contributed to smaller and lighter radiation detection instruments that are, at the same time, more sensitive and provide more information (e.g., radioisotope identification) than previous devices. New developments in radiation detectors, such as cadmium telluride, gas scintillation proportional counters, and imaging counters (both charged particle and photon) promise higher sensitivities and expanded uses over present instruments. These developments are being applied in such areas as health physics, waste management, environmental monitoring, in vivo measurements, and nuclear safeguards

  1. Structural analysis with high brilliance synchrotron radiation

    Ohno, Hideo [Japan Atomic Energy Research Inst., Kamigori, Hyogo (Japan). Kansai Research Establishment

    1997-11-01

    The research subjects in diffraction and scattering of materials with high brilliance synchrotron radiation such as SPring-8 (Super Photon ring 8 GeV) are summarized. The SPring-8 project is going well and 10 public beamlines will be opened for all users in October, 1997. Three JAERI beamlines are also under construction for researches of heavy element science, physical and structural properties under extreme conditions such as high temperature and high pressure. (author)

  2. Crown structure, radiation absorption, photosynthesis and transpiration

    Wang, Yingping

    1988-01-01

    A complex simulation model, MAESTRO, has been developed and validated against field measurements in plantation in both Scotland and Australia. It has been shown that MAESTRO can reasonably predict the daily course of PAR (photosynetically active radiation) transmittance at points below the canopies of radiata pine and Sitka spruce plantations. 1. Four structural properties of the Sitka spruce tree crown have been identified and evaluation in relation to PAR absorption, photosynthesis and ...

  3. Radiation-induced structural changes, (2)

    Ogasawara, M.; Matsuyama, T.

    1992-11-01

    This seminar is aimed at understanding both the physical and chemical aspects of the structural changes of materials induced by photons or ionizing radiation. The seminar was held on December 19th, 1991 and from February 13 to 14th, 1992 in this institute. The most active areas of the material science, in addition to the previous subjects, such as organic superconductors, silicon-based polymers, and fullerenes were included in this seminar. (J.P.N.)

  4. Electronic structure and electron dynamics at Si(100)

    Weinelt, M. [Universitaet Erlangen-Nuernberg, Lehrstuhl fuer Festkoerperphysik, Erlangen (Germany); Max-Born-Institut, Berlin (Germany); Kutschera, M.; Schmidt, R.; Orth, C.; Fauster, T. [Universitaet Erlangen-Nuernberg, Lehrstuhl fuer Festkoerperphysik, Erlangen (Germany); Rohlfing, M. [International University Bremen, School of Engineering and Science, P.O. Box 750 561, Bremen (Germany)

    2005-02-01

    The electronic structure and electron dynamics at a Si(100) surface is studied by two-photon photoemission (2PPE). At 90 K the occupied D{sub up} dangling-bond state is located 150{+-}50 meV below the valence-band maximum (VBM) at the center of the surface Brillouin zone anti {gamma} and exhibits an effective hole mass of (0.5{+-}0.15)m{sub e}. The unoccupied D{sub down} band has a local minimum at anti {gamma} at 650{+-}50 meV above the VBM and shows strong dispersion along the dimer rows of the c(4 x 2) reconstructed surface. At 300 K the D{sub down} position shifts comparable to the Si conduction-band minimum by 40 meV to lower energies but the dispersion of the dangling-bond states is independent of temperature. The surface band bending for p-doped silicon is less than 30 meV, while acceptor-type defects cause significant and preparation-dependent band bending on n-doped samples. 2PPE spectra of Si(100) are dominated by interband transitions between the occupied and unoccupied surface states and emission out of transiently and permanently charged surface defects. Including electron-hole interaction in many-body calculations of the quasi-particle band structure leads us to assign a dangling-bond split-off state to a quasi-one-dimensional surface exciton with a binding energy of 130 meV. Electrons resonantly excited to the unoccupied D{sub down} dangling-bond band with an excess energy of about 350 meV need 1.5{+-}0.2 ps to scatter via phonon emission to the band bottom at anti {gamma} and relax within 5 ps with an excited hole in the occupied surface band to form an exciton living for nanoseconds. (orig.)

  5. Diamond surface: atomic and electronic structure

    Pate, B.B.

    1984-01-01

    Experimental studies of the diamond surface (with primary emphasis on the (111) surface) are presented. Aspects of the diamond surface which are addressed include (1) the electronic structure, (2) the atomic structure, and (3) the effect of termination of the lattice by foreign atoms. Limited studies of graphite are discussed for comparison with the diamond results. Experimental results from valence band and core level photoemission spectroscopy (PES), Auger electron spectroscopy (AES), low energy electron diffraction (LEED), and carbon 1s near edge x-ray absorption fine structure (NEXAFS) spectroscopy (both the total electron yield (TEY) and Auger electron yield (AEY) techniques) are used to study and characterize both the clean and hydrogenated surface. In addition, the interaction of hydrogen with the diamond surface is examined using results from vibrational high resolution low energy electron loss spectroscopy (in collaboration with Waclawski, Pierce, Swanson, and Celotta at the National Bureau of Standards) and photon stimulated ion desorption (PSID) yield at photon energies near the carbon k-edge (hv greater than or equal to 280 eV). Both EELS and PSID verify that the mechanically polished 1 x 1 surface is hydrogen terminated and also that the reconstructed surface is hydrogen free. The (111) 2 x 2/2 x 1 reconstructed surface is obtained from the hydrogenated (111) 1 x 1:H surface by annealing to approx. = 1000 0 C. We observe occupied intrinsic surface states and a surface chemical shift (0.95 +- 0.1 eV) to lower binding energy of the carbon 1s level on the hydrogen-free reconstructed surface. Atomic hydrogen is found to be reactive with the reconstructed surface, while molecular hydrogen is relatively inert. Exposure of the reconstructed surface to atomic hydrogen results in chemisorption of hydrogen and removal of the intrinsic surface state emission in and near the band gap region

  6. Electronic structure and electron momentum density in TiSi

    Ghaleb, A.M. [Department of Physics, College of Science, University of Kirkuk, Kirkuk (Iraq); Mohammad, F.M. [Department of Physics, College of Science, University of Tikreet, Tikreet (Iraq); Sahariya, Jagrati [Department of Physics, University College of Science, M.L. Sukhadia University, Udaipur 313001, Rajasthan (India); Sharma, Mukesh [Physics Division, Forensic Science Laboratory, Jaipur, Rajasthan (India); Ahuja, B.L., E-mail: blahuja@yahoo.com [Department of Physics, University College of Science, M.L. Sukhadia University, Udaipur 313001, Rajasthan (India)

    2013-03-01

    We report the electron momentum density in titanium monosilicide using {sup 241}Am Compton spectrometer. Experimental Compton profile has been compared with the theoretical profiles computed using linear combination of atomic orbitals (LCAO). The energy bands, density of states and Fermi surface structures of TiSi are reported using the LCAO and the full potential linearized augmented plane wave methods. Theoretical anisotropies in directional Compton profiles are interpreted in terms of energy bands. To confirm the conducting behavior, we also report the real space analysis of experimental Compton profile of TiSi.

  7. Modeling of the response under radiation of electronic dosemeters

    Menard, S.

    2003-01-01

    The simulation with with calculation codes the interactions and the transport of primary and secondary radiations in the detectors allows to reduce the number of developed prototypes and the number of experiments under radiation. The simulation makes possible the determination of the response of the instrument for exposure configurations more extended that these ones of references radiations produced in laboratories. The M.C.N.P.X. allows to transport, over the photons, electrons and neutrons, the charged particles heavier than the electrons and to simulate the radiation - matter interactions for a certain number of particles. The present paper aims to present the interest of the use of the M.C.N.P.X. code in the study, research and evaluation phases of the instrumentation necessary to the dosimetry monitoring. To do that the presentation gives the results of the modeling of a prototype of a equivalent tissue proportional counter (C.P.E.T.) and of the C.R.A.M.A.L. ( radiation protection apparatus marketed by the Eurisys Mesures society). (N.C.)

  8. Radiation processing of natural polymers using low energy electron beam

    Kume, Tamikazu

    2004-01-01

    Radiation processing is widely used in Japan and the economic scale of radiation application amounted to about 71 b$ (ratio relative to GDP: 1.7%) in total. It consisted of 60 b$ (85%) in industry, 10 b$ (14%) in medicine and 1 b$ (1%) in agriculture. Irradiation using gamma-ray from 60 Co and electron beam is commercially used for the sterilization and modification of materials. Utilization of natural polymers by radiation has been investigated for recycling the natural resources and reducing the environmental pollution. Polysaccharides such as chitosan, sodium alginate, carrageenan, cellulose, pectin were easily degraded by irradiation and induced various kinds of biological activities, i.e. anti-bacterial activity, elicitor activity, plant growth promotion, suppression of environmental stress on plants. Radiation degraded chitosan was effective to enhance the growth of plants in tissue culture. Low energy electron beam (EB) irradiation has a variety of applications and good safety. A self-shielded low energy electron accelerator system needs an initial investment much lower than a 60 Co facility. It was demonstrated that the liquid sample irradiation system using low energy EB was effective not only for the preparation of degraded polysaccharides but also for radiation vulcanization of natural rubber latex (RVNRL). Some carbohydrate derivatives, carboxymethylcellulose (CMC), carboxymethyl-starch and carboxymethyl-chitin/chitosan, can be crosslinked under certain radiation condition and produced the biodegradable hydrogel for medical and agricultural use. Treatment of soybean seeds by low energy EB enhanced the growth and the number of rhizobia on the root. (author)

  9. Interactions of free electrons with an electromagnetic radiation

    Zel' dovich, Ya B [AN SSSR, Moscow. Inst. Prikladnoj Matematiki

    1975-02-01

    The interaction of a chaotic field of electromagnetic radiation with free electrons in plasma is considered as applied to astrophysical problems, in particular, to the theory of establishing thermodynamic equilibrium of radiation in the hot universe. The kinetic equation describes a change in the spectrum; particular attention is paid to the induced scattering and to the classical interpretation of the induced transfer of energy and momentum. In spectra of radiosources with a high brightness temperature the induced scattering may lead to the Bose condensation of photons, shock wave and appearance of solutions. The scattering of strong low-frequency waves is considered as applied to pulsars and laboratory coherent generators.

  10. Radiation damage relative to transmission electron microscopy of biological specimens at low temperature: a review

    Glaeser, R.M.; Taylor, K.A.

    1978-01-01

    When biological specimens are irradiated by the electron beam in the electron microscope, the specimen structure is damaged as a result of molecular excitation, ionization, and subsequent chemical reactions. The radiation damage that occurs in the normal process of electron microscopy is known to present severe limitations for imaging high resolution detail in biological specimens. The question of radiation damage at low temperatures has therefore been investigated with the view in mind of reducing somewhat the rate at which damage occurs. The radiation damage protection found for small molecule (anhydrous) organic compounds is generally rather limited or even non-existent. However, large molecule, hydrated materials show as much as a 10-fold reduction at low temperature in the rate at which radiation damage occurs, relative to the damage rate at room temperature. In the case of hydrated specimens, therefore, low temperature electron microscopy offers an important advantage as part of the overall effort required in obtaining high resolution images of complex biological structures. (author)

  11. Effect of ionizing radiation on structural and conductive properties of copper nanotubes

    Zdorovets, M. V.; Borgekov, D. B.; Kenzhina, I. E.; Kozlovskiy, A. L.

    2018-01-01

    The use of electron radiation is an effective tool for stimulating a controlled modification of structural and conductive properties of nanomaterials in modern materials science. The paper presents the results of studies of the influence of various types of radiation on structural and conductive properties of copper nanotubes obtained by electrochemical synthesis in pores of templates based on polyethylene terephthalate. Such methods as SEM, X-ray diffraction and EDS show that irradiation with a stream of high-energy electrons with doses of 50-250 kGy makes it possible to modify the crystal structure of nanotubes, increasing their conductivity and decreasing the resistance of nanostructures without destroying the structure.

  12. 3D Printed structural electronics: embedding and connecting electronic components into freeform electronic devices

    Maalderink, H.H.H.; Bruning, F.B.J.; Schipper, M.M.R. de; Werff, J.J.J. van der; Germs, W.W.C.; Remmers, J.J.C.; Meinders, E.R.

    2018-01-01

    The need for personalised and smart products drives the development of structural electronics with mass-customisation capability. A number of challenges need to be overcome in order to address the potential of complete free form manufacturing of electronic devices. One key challenge is the

  13. 3D Printed structural electronics : embedding and connecting electronic components into freeform electronic devices

    Maalderink, H.H.; Bruning, F.B.J.; de Schipper, M.R.; van der Werff, J.J.; Germs, W.C.; Remmers, J.J.C.; Meinders, E.R.

    2018-01-01

    The need for personalised and smart products drives the development of structural electronics with mass-customisation capability. A number of challenges need to be overcome in order to address the potential of complete free form manufacturing of electronic devices. One key challenge is the

  14. Electronic structure of super heavy atoms revisited

    Gitman, D M; Levin, A D; Tyutin, I V; Voronov, B L

    2013-01-01

    The electronic structure of an atom with Z ⩽ Z c = 137 can be described by the Dirac equation with the Coulomb field of a point charge Ze. It was believed that the Dirac equation with Z > Z c poses difficulties because the formula for the lower energy level of the Dirac Hamiltonian formally gives imaginary eigenvalues. But a strict mathematical consideration shows that difficulties with the electronic spectrum for Z > Z c do not arise if the Dirac Hamiltonian is correctly defined as a self-adjoint operator. In this paper, we briefly summarize the main physical results of that consideration in a form suitable for physicists with some additional new details and numerical calculations of the electronic spectra. (comment)

  15. Electronic Structure of Strongly Correlated Materials

    Anisimov, Vladimir

    2010-01-01

    Electronic structure and physical properties of strongly correlated materials containing elements with partially filled 3d, 4d, 4f and 5f electronic shells is analyzed by Dynamical Mean-Field Theory (DMFT). DMFT is the most universal and effective tool used for the theoretical investigation of electronic states with strong correlation effects. In the present book the basics of the method are given and its application to various material classes is shown. The book is aimed at a broad readership: theoretical physicists and experimentalists studying strongly correlated systems. It also serves as a handbook for students and all those who want to be acquainted with fast developing filed of condensed matter physics.

  16. Electronic band structures of binary skutterudites

    Khan, Banaras; Aliabad, H.A. Rahnamaye; Saifullah; Jalali-Asadabadi, S.; Khan, Imad; Ahmad, Iftikhar

    2015-01-01

    The electronic properties of complex binary skutterudites, MX 3 (M = Co, Rh, Ir; X = P, As, Sb) are explored, using various density functional theory (DFT) based theoretical approaches including Green's Function (GW) as well as regular and non-regular Tran Blaha modified Becke Jhonson (TB-mBJ) methods. The wide range of calculated bandgap values for each compound of this skutterudites family confirm that they are theoretically as challenging as their experimental studies. The computationally expensive GW method, which is generally assume to be efficient in the reproduction of the experimental bandgaps, is also not very successful in the calculation of bandgaps. In this article, the issue of the theoretical bandgaps of these compounds is resolved by reproducing the accurate experimental bandgaps, using the recently developed non-regular TB-mBJ approach, based on DFT. The effectiveness of this technique is due to the fact that a large volume of the binary skutterudite crystal is empty and hence quite large proportion of electrons lie outside of the atomic spheres, where unlike LDA and GGA which are poor in the treatment of these electrons, this technique properly treats these electrons and hence reproduces the clear electronic picture of these compounds. - Highlights: • Theoretical and experimental electronic band structures of binary skutterudites are reviewed. • The literature reveals that none of the existing theoretical results are consistent with the experiments. • GW, regular and non-regular TB-mBJ methods are used to reproduce the correct results. • The GW and regular TB-mBJ results are better than the available results in literature. • However, non-regular TB-mBJ reproduces the correct experimental band structures

  17. Electronic band structures of binary skutterudites

    Khan, Banaras [Center for Computational Materials Science, University of Malakand, Chakdara (Pakistan); Department of Physics, University of Malakand, Chakdara (Pakistan); Aliabad, H.A. Rahnamaye [Department of Physics, Hakim Sabzevari University, Sabzevar (Iran, Islamic Republic of); Saifullah [Center for Computational Materials Science, University of Malakand, Chakdara (Pakistan); Department of Physics, University of Malakand, Chakdara (Pakistan); Jalali-Asadabadi, S. [Department of Physics, Faculty of Science, University of Isfahan (UI), 81744 Isfahan (Iran, Islamic Republic of); Khan, Imad [Center for Computational Materials Science, University of Malakand, Chakdara (Pakistan); Department of Physics, University of Malakand, Chakdara (Pakistan); Ahmad, Iftikhar, E-mail: ahma5532@gmail.com [Center for Computational Materials Science, University of Malakand, Chakdara (Pakistan); Department of Physics, University of Malakand, Chakdara (Pakistan)

    2015-10-25

    The electronic properties of complex binary skutterudites, MX{sub 3} (M = Co, Rh, Ir; X = P, As, Sb) are explored, using various density functional theory (DFT) based theoretical approaches including Green's Function (GW) as well as regular and non-regular Tran Blaha modified Becke Jhonson (TB-mBJ) methods. The wide range of calculated bandgap values for each compound of this skutterudites family confirm that they are theoretically as challenging as their experimental studies. The computationally expensive GW method, which is generally assume to be efficient in the reproduction of the experimental bandgaps, is also not very successful in the calculation of bandgaps. In this article, the issue of the theoretical bandgaps of these compounds is resolved by reproducing the accurate experimental bandgaps, using the recently developed non-regular TB-mBJ approach, based on DFT. The effectiveness of this technique is due to the fact that a large volume of the binary skutterudite crystal is empty and hence quite large proportion of electrons lie outside of the atomic spheres, where unlike LDA and GGA which are poor in the treatment of these electrons, this technique properly treats these electrons and hence reproduces the clear electronic picture of these compounds. - Highlights: • Theoretical and experimental electronic band structures of binary skutterudites are reviewed. • The literature reveals that none of the existing theoretical results are consistent with the experiments. • GW, regular and non-regular TB-mBJ methods are used to reproduce the correct results. • The GW and regular TB-mBJ results are better than the available results in literature. • However, non-regular TB-mBJ reproduces the correct experimental band structures.

  18. Electronic structure of Pu carbides: photoelectron spectroscopy

    Gouder, T.; Havela, L.; Shick, Alexander; Huber, F.

    2008-01-01

    Roč. 403, č. 5-9 (2008), s. 852-853 ISSN 0921-4526 R&D Projects: GA AV ČR(CZ) IAA100100530 Grant - others:EU(XE) RITA -CT-2006-026176 Institutional research plan: CEZ:AV0Z10100520 Keywords : photoemission * electronic structure * plutonium Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.822, year: 2008

  19. Structural and electronic properties of thallium compounds

    Paliwal, Neetu; Srivastava, Vipul

    2016-01-01

    The tight binding linear muffin-tin-orbital (TB-LMTO) method within the local density approximation (LDA has been used to calculate structural and electronic properties of thallium pnictides TlX (X=Sb, Bi) at high pressure. As a function of volume, the total energy is evaluated. Apart from this, the lattice parameter (a_0), bulk modulus (B_0), band structure (BS) and density of states (DOS) are calculated. From energy band diagram we observed metallic behaviour in TlSb and TlBi compounds. The values of equilibrium lattice constants and bulk modulus are agreed well with the available data.

  20. Structural and electronic properties of thallium compounds

    Paliwal, Neetu, E-mail: neetumanish@gmail.com [Department of Physics, AISECT University Bhopal, 464993 (India); Srivastava, Vipul [Department of Engineering Physics, NRI Institute of Research & Technology, Raisen Road, Bhopal, 462021 (India)

    2016-05-06

    The tight binding linear muffin-tin-orbital (TB-LMTO) method within the local density approximation (LDA has been used to calculate structural and electronic properties of thallium pnictides TlX (X=Sb, Bi) at high pressure. As a function of volume, the total energy is evaluated. Apart from this, the lattice parameter (a{sub 0}), bulk modulus (B{sub 0}), band structure (BS) and density of states (DOS) are calculated. From energy band diagram we observed metallic behaviour in TlSb and TlBi compounds. The values of equilibrium lattice constants and bulk modulus are agreed well with the available data.

  1. Structural dynamics of electronic and photonic systems

    Suhir, Ephraim; Steinberg, David S

    2011-01-01

    The proposed book will offer comprehensive and versatile methodologies and recommendations on how to determine dynamic characteristics of typical micro- and opto-electronic structural elements (printed circuit boards, solder joints, heavy devices, etc.) and how to design a viable and reliable structure that would be able to withstand high-level dynamic loading. Particular attention will be given to portable devices and systems designed for operation in harsh environments (such as automotive, aerospace, military, etc.)  In-depth discussion from a mechanical engineer's viewpoint will be conducte

  2. Dosimetry study for electron beam irradiation in radiation processing

    Sunaga, Hiromi; Haruyama, Yasuyuki; Takizawa, Haruki; Kojima, Takuji; Yotsumoto, Keiichi

    1995-01-01

    For certain critical applications such as medical device sterilization and food irradiation, accurate calibration of electron energy and absorbed dose is required to assure the quality of irradiated products. To meet this requirement, TRCRE, JAERI has carried out research and development on high dose radiation dosimetry for electron beams in the energy range used in radiation processing (0.15 - 3.0 MeV). JAERI has developed a simultaneous electron beam energy and dosimeter calibration system that consist of a total absorption calorimeter, an electron current density meter, and a stacked thin-film dosimeter set. For low energy electrons, where it is important to measure the depth-dose profile in materials with high depth resolution, we studied the feasibility of a method using Gafchromic film dosimeters. This film, which has an 8-μm thick sensitive layer, is combined with a stepped array of absorber films of the same thickness to produce a high-resolution depth-dose profile on the Gafchromic film. The depth-dose profile obtained in this manner has about five times greater resolution than conventional radiochromic film dosimetry. (author)

  3. Energy and intensity modulated radiation therapy with electrons

    Olofsson, Lennart

    2005-01-01

    In recent years intensity modulated radiation therapy with photons (xIMRT) has gained attention due to its ability to reduce the dose in the tissues close to the tumour volume. However, this technique also results in a large low dose volume. Electron IMRT (eIMRT) has the potential to reduce the integral dose to the patient due to the dose fall off in the electron depth dose curves. This dose fall off makes it possible to modulate the dose distribution in the direction of the beam by selecting...

  4. Radiation degradation of marine polysaccharides by low energy electron beam

    Yoshii, Fumio; Nagasawa, Naotsugu; Kume, Tamikazu

    2003-01-01

    The radiation degradations of marine polysaccharides by both gamma Co-60 and electron beam irradiations are investigated. Polysaccharides and oligosaccharides can be produced by degradation of corresponding polysaccharides including marine polysaccharides such as alginates, chitin chitosan and carrageenan. The viscosity of alginate, chitosan and carrageenan solution decreases markedly with increase of the low energy electron beam irradiation time and the beam current. Furthermore, the viscosity is reduced sharply in short time for polysaccharide solution with low concentration, for instance carrageenan solution of 1%. (author)

  5. Electronic radiation of a plasma in a magnetic field

    Canobbio, E.; Consoli, T.; Ichtchenko, G.; Parlance, F.

    1965-01-01

    The influence on the microwave spectrum of the number of fast electrons, density, pressure and plasma inhomogeneities, has been studied in a hot cathode reflex discharge, operating either in a steady state either in a pulsed regime. Under some conditions a strong emission is observed between the harmonics of the electron gyrofrequency. A theoretical interpretation of the results is advanced by extending a model already proposed by CANOBBIO and CROCI. In particular it is indicated that the transition radiation can be responsible for the emission observed between the harmonics. (authors) [fr

  6. Weak-beam electron microscopy of radiation-induced segregation

    Saka, H.

    1983-01-01

    The segregation of solute atoms to dislocations during irradiation by 1 MeV electrons in a HVEM was studied by measuring the dissociation width of extended dislocations in Cu-5.1 at.%Si, Cu-5.3 at.%Ge, Ag-9.4 at.% In and Ag-9.6 at.%Al alloys. 'Weak-beam' electron microscopy was used. In Cu-Si (oversized solute), Cu-Ge (oversize) and Ag-Al (undersize), solute enrichment was observed near dislocations, while in Ag-In (oversize) solute depletion was observed. The results are discussed in terms of current mechanisms for radiation-induced segregation. (author)

  7. Gelatin/piassava composites treated by Electron Beam Radiation

    Takinami, Patricia Yoko Inamura; Shimazaki, Kleber; Moura, Esperidiana Augusta Barretos de; Mastro, Nelida Lucia del; Colombo, Maria Aparecida

    2010-01-01

    Piassava (Attalea funifera Mart) fiber has been investigated as reinforcement for polymer composites with potential for practical applications. The purpose of the present work was to assess the behavior of specimens of piassava fiber and gelatin irradiated with electron beam at different doses and percentage. The piassava/gelatin specimens were made with 5 and 10% (w/w) piassava fiber, gelatin 25% (w/w), glycerin as plasticizer and acrylamide as copolymer. The samples were irradiated up to 40 kGy using an electron beam accelerator, at room temperature in presence of air. Preliminary results showed mechanical properties enhancement with the increase in radiation dose. (author)

  8. Electron acceleration and radiation signatures in loop coronal transients

    Vlahos, L.; Gergely, T. E.; Papadopoulos, K.

    1982-01-01

    It is proposed that in loop coronal transients an erupting loop moves away from the solar surface, with a velocity exceeding the local Alfven speed, pushing against the overlying magnetic fields and driving a shock in the front of the moving part of the loop. Lower hybrid waves are excited at the shock front and propagate radially toward the center of the loop with phase velocity along the magnetic field that exceeds the thermal velocity. The lower hybrid waves stochastically accelerate the tail of the electron distribution inside the loop. The manner in which the accelerated electrons are trapped in the moving loop are discussed, and their radiation signature is estimated. It is suggested that plasma radiation can explain the power observed in stationary and moving type IV bursts.

  9. Radiation load experiments with electronic components of the SYMPHONIE satellite

    Spencker, A.; Wagemann, H.G.; Braeunig, D.

    1975-09-01

    This report surveys fundamentals, realization and results of irradiation experiments which applied to 36 different electronic components of the Symphonie satellite and which were completed at the HMI Berlin and the C.N.E.T. Lannion in the years 1972/73. In a general section the evaluation of equivalent fluencies concerning 1 MeV electrons as radiation simulating the extraterrestric particle spectra with regard to the well-known semiconductor damage mechanisms is discussed. Then the realization of irradiation testing for the Symphonie satellite is described. Three selected examples demonstrate typical failure modes of semiconductor devices under radiation stress: Finally the main experimental results are shown in a standardized manner; a survey in English is given on p. 44. (orig.) [de

  10. Ultrashort electron bunch length measurement with diffraction radiation deflector

    Xiang, Dao; Huang, Wen-Hui

    2007-01-01

    In this paper, we propose a novel method to measure electron bunch length with a diffraction radiation (DR) deflector which is composed of a DR radiator and three beam position monitors (BPMs). When an electron beam passes through a metallic aperture which is tilted by 45 degrees with respect to its trajectory, backward DR that propagates perpendicular to the beam’s trajectory is generated which adds a transverse deflection to the beam as a result of momentum conservation. The deflection is found to be largely dependent on the bunch length and could be easily observed with a downstream BPM. Detailed investigations show that this method has wide applicability, high temporal resolution, and great simplicity.

  11. Ultrashort electron bunch length measurement with diffraction radiation deflector

    Dao Xiang

    2007-01-01

    Full Text Available In this paper, we propose a novel method to measure electron bunch length with a diffraction radiation (DR deflector which is composed of a DR radiator and three beam position monitors (BPMs. When an electron beam passes through a metallic aperture which is tilted by 45 degrees with respect to its trajectory, backward DR that propagates perpendicular to the beam’s trajectory is generated which adds a transverse deflection to the beam as a result of momentum conservation. The deflection is found to be largely dependent on the bunch length and could be easily observed with a downstream BPM. Detailed investigations show that this method has wide applicability, high temporal resolution, and great simplicity.

  12. Radiation Hardened Electronics Destined For Severe Nuclear Reactor Environments

    Holbert, Keith E. [Arizona State Univ., Tempe, AZ (United States); Clark, Lawrence T. [Arizona State Univ., Tempe, AZ (United States)

    2016-02-19

    Post nuclear accident conditions represent a harsh environment for electronics. The full station blackout experience at Fukushima shows the necessity for emergency sensing capabilities in a radiation-enhanced environment. This NEET (Nuclear Energy Enabling Technologies) research project developed radiation hardened by design (RHBD) electronics using commercially available technology that employs commercial off-the-shelf (COTS) devices and present generation circuit fabrication techniques to improve the total ionizing dose (TID) hardness of electronics. Such technology not only has applicability to severe accident conditions but also to facilities throughout the nuclear fuel cycle in which radiation tolerance is required. For example, with TID tolerance to megarads of dose, electronics could be deployed for long-term monitoring, inspection and decontamination missions. The present work has taken a two-pronged approach, specifically, development of both board and application-specific integrated circuit (ASIC) level RHBD techniques. The former path has focused on TID testing of representative microcontroller ICs with embedded flash (eFlash) memory, as well as standalone flash devices that utilize the same fabrication technologies. The standalone flash devices are less complicated, allowing better understanding of the TID response of the crucial circuits. Our TID experiments utilize biased components that are in-situ tested, and in full operation during irradiation. A potential pitfall in the qualification of memory circuits is the lack of rigorous testing of the possible memory states. For this reason, we employ test patterns that include all ones, all zeros, a checkerboard of zeros and ones, an inverse checkerboard, and random data. With experimental evidence of improved radiation response for unbiased versus biased conditions, a demonstration-level board using the COTS devices was constructed. Through a combination of redundancy and power gating, the demonstration

  13. Time-resolved photoelectron spectroscopy using synchrotron radiation time structure

    Bergeard, N.; Silly, M.G.; Chauvet, C.; Guzzo, M.; Ricaud, J.P.; Izquierdo, M.; Sirotti, F.; Krizmancic, D.; Guzzo, M.; Stebel, L.; Pittana, P.; Sergo, R.; Cautero, G.; Dufour, G.; Rochet, F.

    2011-01-01

    Synchrotron radiation time structure is becoming a common tool for studying dynamic properties of materials. The main limitation is often the wide time domain the user would like to access with pump-probe experiments. In order to perform photoelectron spectroscopy experiments over time scales from milliseconds to picoseconds it is mandatory to measure the time at which each measured photoelectron was created. For this reason the usual CCD camera based two-dimensional detection of electron energy analyzers has been replaced by a new delay-line detector adapted to the time structure of the SOLEIL synchrotron radiation source. The new two-dimensional delay-line detector has a time resolution of 5 ns and was installed on a Scienta SES 2002 electron energy analyzer. The first application has been to characterize the time of flight of the photo emitted electrons as a function of their kinetic energy and the selected pass energy. By repeating the experiment as a function of the available pass energy and of the kinetic energy, a complete characterization of the analyzer behaviour in the time domain has been obtained. Even for kinetic energies as low as 10 eV at 2 eV pass energy, the time spread of the detected electrons is lower than 140 ns. These results and the time structure of the SOLEIL filling modes assure the possibility of performing pump-probe photoelectron spectroscopy experiments with the time resolution given by the SOLEIL pulse width, the best performance of the beamline and of the experimental station. (authors)

  14. Coherent spontaneous radiation from highly bunched electron beams

    Berryman, K.W.; Crosson, E.R.; Ricci, K.N.

    1995-01-01

    Coherent spontaneous radiation has now been observed in several FELs, and is a subject of great importance to the design of self-amplified spontaneous emission (SASE) devices. We report observations of coherent spontaneous radiation in both FIREFLY and the mid-infrared FEL at the Stanford Picosecond FEL Center. Coherent emission has been observed at wavelengths as short as 5 microns, and enhancement over incoherent levels by as much as a factor of 4x10 4 has been observed at longer wavelengths. The latter behavior was observed at 45 microns in FIREFLY with short bunches produced by off-peak acceleration and dispersive compression. We present temporal measurements of the highly bunched electron distributions responsible for the large enhancements, using both transition radiation and energy-phase techniques

  15. Radiation doses inside industrial irradiation installation with linear electron accelerator

    Lima, Alexandre R., E-mail: alexandre.lima@cnen.gov.br [Comissao Nacional de Energia Nuclear (CNEN), Rio de Janeiro, RJ (Brazil); Pelegrineli, Samuel Q.; Alo, Gabriel F., E-mail: samuelfisica@yahoo.com.br, E-mail: gabriel.alo@aceletron.com.br [Aceletron Irradiacao Industrial, Aceletrica Comercio e Representacoes Ltda, Rio de Janeiro, RJ (Brazil); Silva, Francisco C.A. Da, E-mail: dasilva@ird.gov.br [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

    2015-07-01

    Aceletron Industrial Irradiation Company is the unique installation in South America to provide industrial irradiation service using two linear electron accelerators of 18 kW and 10 MeV energy. The electron beam technology allows using electrons to irradiate many goods and materials, such as hospital and medical equipment, cosmetics, herbal products, polymers, peat, gemstones and food. Aceletron Company uses a concrete bunker with 3.66 m of thickness to provide the necessary occupational and environmental radiation protection of X-rays produced. The bunker is divided in main four areas: irradiation room, maze, tower and pit. Inside the irradiation room the x-rays radiation rates are measured in two ways: direct beam and 90 deg C. The rates produced in the conveyor system using 10 MeV energy are 500 Gy/min/mA and 15 Gy/min/mA, respectively. For a 1.8 mA current, the rates produced are 900 Gy/min and 27 Gy/min, respectively. Outside the bunker the radiation rate is at background level, but in the tower door and modulation room the radiation rate is 10 μSv/h. In 2014, during a routine operation, an effective dose of 30.90 mSv was recorded in a monthly individual dosimeter. After the investigation, it was concluded that the dose was only in the dosimeter because it felt inside the irradiation room. As Aceletron Company follows the principles of safety culture, it was decided to perform the radiation isodose curves, inside the four areas of the installation, to know exactly the hotspots positions, exposure times and radiation doses. Five hotspots were chosen taking into account worker's routes and possible operational places. The first experiment was done using a package with three TLD and OSLD dosimeters to obtain better statistical results. The first results for the five hotspots near the accelerator machine showed that the radiation dose rates were between 26 Gy/h and 31 Gy/h. The final measurements were performed using a package with one TLD and one OSLD

  16. Radiation doses inside industrial irradiation installation with linear electron accelerator

    Lima, Alexandre R.; Pelegrineli, Samuel Q.; Alo, Gabriel F.; Silva, Francisco C.A. Da

    2015-01-01

    Aceletron Industrial Irradiation Company is the unique installation in South America to provide industrial irradiation service using two linear electron accelerators of 18 kW and 10 MeV energy. The electron beam technology allows using electrons to irradiate many goods and materials, such as hospital and medical equipment, cosmetics, herbal products, polymers, peat, gemstones and food. Aceletron Company uses a concrete bunker with 3.66 m of thickness to provide the necessary occupational and environmental radiation protection of X-rays produced. The bunker is divided in main four areas: irradiation room, maze, tower and pit. Inside the irradiation room the x-rays radiation rates are measured in two ways: direct beam and 90 deg C. The rates produced in the conveyor system using 10 MeV energy are 500 Gy/min/mA and 15 Gy/min/mA, respectively. For a 1.8 mA current, the rates produced are 900 Gy/min and 27 Gy/min, respectively. Outside the bunker the radiation rate is at background level, but in the tower door and modulation room the radiation rate is 10 μSv/h. In 2014, during a routine operation, an effective dose of 30.90 mSv was recorded in a monthly individual dosimeter. After the investigation, it was concluded that the dose was only in the dosimeter because it felt inside the irradiation room. As Aceletron Company follows the principles of safety culture, it was decided to perform the radiation isodose curves, inside the four areas of the installation, to know exactly the hotspots positions, exposure times and radiation doses. Five hotspots were chosen taking into account worker's routes and possible operational places. The first experiment was done using a package with three TLD and OSLD dosimeters to obtain better statistical results. The first results for the five hotspots near the accelerator machine showed that the radiation dose rates were between 26 Gy/h and 31 Gy/h. The final measurements were performed using a package with one TLD and one OSLD

  17. Estimates for the probability of survival of electrons in passing through a radiator

    Loos, J.

    1977-01-01

    Some calculations on the survival of electrons passing through various radiator thicknesses are tabulated. The results of these calculations should serve as a guide for expected attenuation of electrons in the beam when various Pb radiators are inserted

  18. Dosimetry of ionizing radiations by Electron paramagnetic resonance

    Azorin N, J.

    2005-01-01

    In this work, some historical and theoretical aspects about the Electron Paramagnetic Resonance (EPR), its characteristics, the resonance detection, the paramagnetic species, the radiation effects on inorganic and organic materials, the diagrams of the instrumentation for the EPR detection, the performance of an EPR spectrometer, the coherence among EPR and dosimetry and, practical applications as well as in the food science there are presented. (Author)

  19. Radiation of electrons in an electromagnetic axial trap

    Toropova, A.I.

    1998-01-01

    The version of a trap. wherein particles move in a homogeneous constant magnetic field and electrostatic field, formed by two equipotential planes and rotation axial surface, is proposed. The solution of canonic equations is found. It is shown that interaction of electrons with the radiation field leads to damping parametric resonance. The trap model, accounting for the finite conductivity of the resonator walls and losses by collisions with gas, is studied

  20. Ginzburg's invention of undulators and their role in modern synchrotron radiation sources and free electron lasers

    Kulipanov, Gennadii N

    2007-01-01

    Undulators - periodic magnetic structures that were originally introduced by Vitalii Ginzburg in 1947 for electromagnetic radiation generation using relativistic electrons - are among the key elements of modern synchrotron radiation sources and free electron lasers (FELs). In this talk, the history of three generations of storage ring-based synchrotron X-ray sources using wigglers and undulators is briefly traced. Prospects for two types of next-generation space-coherent X-ray sources are discussed, which use long undulators and energy recovery accelerators or, alternatively, employ linear accelerator-based FELs. The recently developed Novosibirsk terahertz FEL facility, currently the world' s most powerful terahertz source, is described. It was the generation of electromagnetic radiation in this range that Ginzburg discussed in his 1947 work. (oral issue of the journal 'uspekhi fizicheskikh nauk')

  1. Correlated electronic structure of CeN

    Panda, S.K., E-mail: swarup.panda@physics.uu.se [Department of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-751 20 Uppsala (Sweden); Di Marco, I. [Department of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-751 20 Uppsala (Sweden); Delin, A. [Department of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-751 20 Uppsala (Sweden); KTH Royal Institute of Technology, School of Information and Communication Technology, Department of Materials and Nano Physics, Electrum 229, SE-164 40 Kista (Sweden); KTH Royal Institute of Technology, Swedish e-Science Research Center (SeRC), SE-100 44 Stockholm (Sweden); Eriksson, O., E-mail: olle.eriksson@physics.uu.se [Department of Physics and Astronomy, Uppsala University, P.O. Box 516, SE-751 20 Uppsala (Sweden)

    2016-04-15

    Highlights: • The electronic structure of CeN is studied within the GGA+DMFT approach using SPTF and Hubbard I approximation. • 4f spectral functions from SPTF and Hubbard I are coupled to explain the various spectroscopic manifestations of CeN. • The calculated XPS and BIS spectra show good agreement with the corresponding experimental spectra. • The contribution of the various l-states and the importance of cross-sections for the photoemission process are analyzed. - Abstract: We have studied in detail the electronic structure of CeN including spin orbit coupling (SOC) and electron–electron interaction, within the dynamical mean-field theory combined with density-functional theory in generalized gradient approximation (GGA+DMFT). The effective impurity problem has been solved through the spin-polarized T-matrix fluctuation-exchange (SPTF) solver and the Hubbard I approximation (HIA). The calculated l-projected atomic partial densities of states and the converged potential were used to obtain the X-ray-photoemission-spectra (XPS) and Bremstrahlung Isochromat spectra (BIS). Following the spirit of Gunnarsson–Schonhammer model, we have coupled the SPTF and HIA 4f spectral functions to explain the various spectroscopic manifestations of CeN. Our computed spectra in such a coupled scheme explain the experimental data remarkably well, establishing the validity of our theoretical model in analyzing the electronic structure of CeN. The contribution of the various l-states in the total spectra and the importance of cross sections are also analyzed in detail.

  2. Electronic structure theory of the superheavy elements

    Eliav, Ephraim, E-mail: ephraim@tau.ac.il [School of Chemistry, Tel Aviv University, 6997801 Tel Aviv (Israel); Fritzsche, Stephan, E-mail: s.fritzsche@gsi.de [Helmholtz-Institut Jena, Fröbelstieg 3, D-07743 Jena (Germany); Theoretisch-Physikalisches Institut, Friedrich-Schiller-Universität Jena, D-07743 Jena (Germany); Kaldor, Uzi, E-mail: kaldor@tau.ac.il [School of Chemistry, Tel Aviv University, 6997801 Tel Aviv (Israel)

    2015-12-15

    High-accuracy calculations of atomic properties of the superheavy elements (SHE) up to element 122 are reviewed. The properties discussed include ionization potentials, electron affinities and excitation energies, which are associated with the spectroscopic and chemical behavior of these elements, and are therefore of considerable interest. Accurate predictions of these quantities require high-order inclusion of relativity and electron correlation, as well as large, converged basis sets. The Dirac–Coulomb–Breit Hamiltonian, which includes all terms up to second order in the fine-structure constant α, serves as the framework for the treatment; higher-order Lamb shift terms are considered in some selected cases. Electron correlation is treated by either the multiconfiguration self-consistent-field approach or by Fock-space coupled cluster theory. The latter is enhanced by the intermediate Hamiltonian scheme, allowing the use of larger model (P) spaces. The quality of the calculations is assessed by applying the same methods to lighter homologs of the SHEs and comparing with available experimental information. Very good agreement is obtained, within a few hundredths of an eV, and similar accuracy is expected for the SHEs. Many of the properties predicted for the SHEs differ significantly from what may be expected by straightforward extrapolation of lighter homologs, demonstrating that the structure and chemistry of SHEs are strongly affected by relativity. The major scientific challenge of the calculations is to find the electronic structure and basic atomic properties of the SHE and assign its proper place in the periodic table. Significant recent developments include joint experimental–computational studies of the excitation spectrum of Fm and the ionization energy of Lr, with excellent agreement of experiment and theory, auguring well for the future of research in the field.

  3. Spectral-Product Methods for Electronic Structure Calculations (Preprint)

    Langhoff, P. W; Mills, J. E; Boatz, J. A

    2006-01-01

    .... The spectral-product approach to molecular electronic structure avoids the repeated evaluations of the one- and two-electron integrals required in construction of polyatomic Hamiltonian matrices...

  4. Spectral-Product Methods for Electronic Structure Calculations (Postprint)

    Langhoff, P. W; Hinde, R. J; Mills, J. D; Boatz, J. A

    2007-01-01

    .... The spectral-product approach to molecular electronic structure avoids the repeated evaluations of the one- and two-electron integrals required in construction of polyatomic Hamiltonian matrices...

  5. Axial ion-electron emission microscopy of IC radiation hardness

    Doyle, B. L.; Vizkelethy, G.; Walsh, D. S.; Swenson, D.

    2002-05-01

    A new system for performing radiation effects microscopy (REM) has been developed at Sandia National Laboratory in Albuquerque. This system combines two entirely new concepts in accelerator physics and nuclear microscopy. A radio frequency quadrupole (RFQ) linac is used to boost the energy of ions accelerated by a conventional Tandem Van de Graaff-Pelletron to velocities of 1.9 MeV/amu. The electronic stopping power for heavy ions is near a maximum at this velocity, and their range is ˜20 μm in Si. These ions therefore represent the most ionizing form of radiation in nature, and are nearly ideal for performing single event effects testing of integrated circuits. Unfortunately, the energy definition of the RFQ-boosted ions is rather poor (˜ a few %), which makes problematic the focussing of such ions to the submicron spots required for REM. To circumvent this problem, we have invented ion electron emission microscopy (IEEM). One can perform REM with the IEEM system without focussing or scanning the ion beam. This is because the position on the sample where each ion strikes is determined by projecting ion-induced secondary electrons at high magnification onto a single electron position sensitive detector. This position signal is then correlated with each REM event. The IEEM system is now mounted along the beam line in an axial geometry so that the ions pass right through the electron detector (which is annular), and all of the electrostatic lenses used for projection. The beam then strikes the sample at normal incidence which results in maximum ion penetration and removes a parallax problem experienced in an earlier system. Details of both the RFQ-booster and the new axial IEEM system are given together with some of the initial results of performing REM on Sandia-manufactured radiation hardened integrated circuits.

  6. Labeling for Big Data in radiation oncology: The Radiation Oncology Structures ontology.

    Bibault, Jean-Emmanuel; Zapletal, Eric; Rance, Bastien; Giraud, Philippe; Burgun, Anita

    2018-01-01

    Leveraging Electronic Health Records (EHR) and Oncology Information Systems (OIS) has great potential to generate hypotheses for cancer treatment, since they directly provide medical data on a large scale. In order to gather a significant amount of patients with a high level of clinical details, multicenter studies are necessary. A challenge in creating high quality Big Data studies involving several treatment centers is the lack of semantic interoperability between data sources. We present the ontology we developed to address this issue. Radiation Oncology anatomical and target volumes were categorized in anatomical and treatment planning classes. International delineation guidelines specific to radiation oncology were used for lymph nodes areas and target volumes. Hierarchical classes were created to generate The Radiation Oncology Structures (ROS) Ontology. The ROS was then applied to the data from our institution. Four hundred and seventeen classes were created with a maximum of 14 children classes (average = 5). The ontology was then converted into a Web Ontology Language (.owl) format and made available online on Bioportal and GitHub under an Apache 2.0 License. We extracted all structures delineated in our department since the opening in 2001. 20,758 structures were exported from our "record-and-verify" system, demonstrating a significant heterogeneity within a single center. All structures were matched to the ROS ontology before integration into our clinical data warehouse (CDW). In this study we describe a new ontology, specific to radiation oncology, that reports all anatomical and treatment planning structures that can be delineated. This ontology will be used to integrate dosimetric data in the Assistance Publique-Hôpitaux de Paris CDW that stores data from 6.5 million patients (as of February 2017).

  7. Microscopical Studies of Structural and Electronic Properties of Semiconductors

    2002-01-01

    The electronic and structural properties of point defects in semiconductors, e.g. radiation defects, impurities or passivating defects can excellently be studied by the hyperfine technique of Perturbed Angular Correlation (PAC). The serious limitation of this method, the small number of chemically different radioactive PAC probe atoms can be widely overcome by means of ISOLDE. Providing shortliving isotopes, which represent common dopants as well as suitable PAC probe atoms, the ISOLDE facility enables a much broader application of PAC to problems in semiconductor physics.\\\\ Using the probe atom $^{111m}$ Cd , the whole class of III-V compounds becomes accessible for PAC investigations. First successful experiments in GaAs, InP and GaP have been performed, concerning impurity complex formation and plasma induced defects. In Si and Ge, the electronic properties~-~especially their influence on acceptor-donor interaction~-~could be exemplarily st...

  8. Electronic structure characterization and bandgap engineering of solar hydrogen materials

    Guo, Jinghua

    2007-01-01

    Bandgap, band edge positions as well as the overall band structure of semiconductors are of crucial importance in photoelectrochemical and photocatalytic applications. The energy position of the band edge level can be controlled by the electronegativity of the dopants, the pH of the solution (flatband potential variation of 60 mV per pH unit), as well as by quantum confinement effects. Accordingly, band edges and bandgap can be tailored to achieve specific electronic, optical or photocatalytic properties. Synchrotron radiation with photon energy at or below 1 keV is giving new insight into such areas as condensed matter physics and extreme ultraviolet optics technology. In the soft x-ray region, the question tends to be, what are the electrons doing as they migrated between the atoms. In this paper, I will present a number of soft x-ray spectroscopic study of nanostructured 3d metal compounds Fe 2 O 3 and ZnO

  9. Electronic structure and superconductivity of europium

    Nixon, Lane W.; Papaconstantopoulos, D.A.

    2010-01-01

    We have calculated the electronic structure of Eu for the bcc, hcp, and fcc crystal structures for volumes near equilibrium up to a calculated 90 GPa pressure using the augmented-plane-wave method in the local-density approximation. The frozen-core approximation was used with a semi-empirical shift of the f-states energies in the radial Schroedinger equation to move the occupied 4f valence states below the Γ 1 energy and into the core. This shift of the highly localized f-states yields the correct europium phase ordering with lattice parameters and bulk moduli in good agreement with experimental data. The calculated superconductivity properties under pressure for the bcc and hcp structures are also found to agree with and follow a T c trend similar to recent measurement by Debessai et al.

  10. Boson structure functions from inelastic electron scattering

    De Jager, C.W.

    1986-01-01

    The even /sup 104-110/Pd isotopes and /sup 196/Pt have been investigated at NIKHEF-K by high-resolution inelastic electron scattering. A new IBA-2 calculation has been performed for the Pd isotopes, in which the ratio of the proton and neutron coupling constants is taken from pion scattering. One set of boson structure functions sufficed for the description of the first and second E2-excitations in all Pd isotopes. The data showed no sensitivity for different structure functions for proton and neutron bosons. A preliminary analysis of a number of negative parity states (3/sup -/,5/sup -/ and 7/sup -/), observed in /sup 196/Pt, was performed through the introduction of an f-boson. The first E4-excitation in the palladium isotopes can be reasonably described with a β-structure function, but all other E4-excitations require the introduction of g-boson admixtures

  11. Electronic Structures of LNA Phosphorothioate Oligonucleotides

    Henrik G. Bohr

    2017-09-01

    Full Text Available Important oligonucleotides in anti-sense research have been investigated in silico and experimentally. This involves quantum mechanical (QM calculations and chromatography experiments on locked nucleic acid (LNA phosphorothioate (PS oligonucleotides. iso-potential electrostatic surfaces are essential in this study and have been calculated from the wave functions derived from the QM calculations that provide binding information and other properties of these molecules. The QM calculations give details of the electronic structures in terms of e.g., energy and bonding, which make them distinguish or differentiate between the individual PS diastereoisomers determined by the position of sulfur atoms. Rules are derived from the electronic calculations of these molecules and include the effects of the phosphorothioate chirality and formation of electrostatic potential surfaces. Physical and electrochemical descriptors of the PS oligonucleotides are compared to the experiments in which chiral states on these molecules can be distinguished. The calculations demonstrate that electronic structure, electrostatic potential, and topology are highly sensitive to single PS configuration changes and can give a lead to understanding the activity of the molecules. Keywords: LNA phosphorothioate, DNA/LNA oligonucleotide, diastereoisomers, Hartree-Fock calculations, iso-potential surface, anion chromatograms

  12. Electron beam crosslinked PVC : structure property relationships

    Gupta, Neeraj K.; Sabharwal, Sunil

    2001-01-01

    PVC is used extensively for its insulating properties for the manufacture of wires and cables and for other applications. Its gradual degradation, oxidation and even dehydro chlorination restricts use for long lasting period in installations such as high temperature zones, underground cables, communication systems, electro-nuclear facilities, etc. The technological properties and performance characteristics of PVC based insulation can be improved via crosslinking by high-energy electrons. PVC is however a polymer, which on irradiation predominantly undergoes degradation. To avoid degradation, it needs to be compounded with sensitizing agents or multifunctional monomers so that crosslinking is the predominant reaction. Radiation cross linkable formulations are complex mixtures of resin and various additives incorporated for achieving desired technological and performance characteristics, ease of processing and improving quality. The proper choice of additives and sensitizing agents enable low dose requirements for efficient crosslinking and improvements in various technological properties. The purposes of this work was to investigate the effect of using a binary sensitizer blend of a trifunctional monomer and a rubber in PVC, and develop suitable electron beam cross linkable formulations for wire insulation. This paper presents some aspects of the investigations and development of insulation demonstrated at industrial scale

  13. Radiation

    2013-01-01

    The chapter one presents the composition of matter and atomic theory; matter structure; transitions; origin of radiation; radioactivity; nuclear radiation; interactions in decay processes; radiation produced by the interaction of radiation with matter

  14. Radiation-induced processes in the metallic powders after electron and gamma-radiation

    Zajkin, Yu.A.; Aliev, B.A.

    2001-01-01

    In the work the quantitative assessments for conditions both healing and growth of micropores in metal volume and surface layers have been made. Taking into account of these rules is important at a choice of radiation processing conditions for fine-disperse powders characterizing with increased porosity. Numerical evaluation shows, that under irradiation of a metals by electrons with energy 2 MeV and electron current density about 1 μA/cm 2 within 300-400 K temperature range the optimal doses for the micropores healing make up a several Mrad. Further increase of dose could lead to formation of pores in the crystal volume. Principal conclusions about radiation porosity development character of metallic particles surface layers one can make from analysis of the point defects distribution near surface and computing of radiation-induced diffusion coefficients

  15. Electron Beam Induced Radiation Damage of the Semiconductor Radiation Detector based on Silicon

    Kim, Han Soo; Kim, Yong Kyun; Park, Se Hwan; Haa, Jang Ho; Kang, Sang Mook; Chung, Chong Eun; Cho, Seung Yeon; Park, Ji Hyun; Yoon, Tae Hyung

    2005-01-01

    A Silicon Surface Barrier (SSB) semiconductor detector which is generally used to detect a charged particle such as an alpha particle was developed. The performance of the developed SSB semiconductor detector was measured with an I-V curve and an alpha spectrum. The response for an alpha particle was measured by Pu-238 sources. A SSB semiconductor detector was irradiated firstly at 30sec, at 30μA and secondly 40sec, 40μA with a 2MeV pulsed electron beam generator in KAERI. And the electron beam induced radiation damage of a homemade SSB detector and the commercially available PIN photodiode were investigated. An annealing effect of the damaged SSB and PIN diode detector were also investigated using a Rapid Thermal Annealing (RTA). This data may assist in designing the silicon based semiconductor radiation detector when it is operated in a high radiation field such as space or a nuclear power plant

  16. Extraordinary electronic properties in uncommon structure types

    Ali, Mazhar Nawaz

    In this thesis I present the results of explorations into several uncommon structure types. In Chapter 1 I go through the underlying idea of how we search for new compounds with exotic properties in solid state chemistry. The ideas of exploring uncommon structure types, building up from the simple to the complex, using chemical intuition and thinking by analogy are discussed. Also, the history and basic concepts of superconductivity, Dirac semimetals, and magnetoresistance are briefly reviewed. In chapter 2, the 1s-InTaS2 structural family is introduced along with the discovery of a new member of the family, Ag0:79VS2; the synthesis, structure, and physical properties of two different polymorphs of the material are detailed. Also in this chapter, we report the observation of superconductivity in another 1s structure, PbTaSe2. This material is especially interesting due to it being very heavy (resulting in very strong spin orbit coulping (SOC)), layered, and noncentrosymmetric. Electronic structure calculations reveal the presence of a bulk 3D Dirac cone (very similar to graphene) that is gapped by SOC originating from the hexagonal Pb layer. In Chapter 3 we show the re-investigation of the crystal structure of the 3D Dirac semimetal, Cd3As2. It is found to be centrosymmetric, rather than noncentrosymmetric, and as such all bands are spin degenerate and there is a 4-fold degenerate bulk Dirac point at the Fermi level, making Cd3As2 a 3D electronic analog to graphene. Also, for the first time, scanning tunneling microscopy experiments identify a 2x2 surface reconstruction in what we identify as the (112) cleavage plane of single crystals; needle crystals grow with a [110] long axis direction. Lastly, in chapter 4 we report the discovery of "titanic" (sadly dubbed ⪉rge, nonsaturating" by Nature editors and given the acronym XMR) magnetoresistance (MR) in the non-magnetic, noncentrosymmetric, layered transition metal dichalcogenide WTe2; over 13 million% at 0.53 K in

  17. Radiation damage in nonmetallic solids under dense electronic excitation

    Itoh, Noriaki; Tanimura, Katsumi; Nakai, Yasuo

    1992-01-01

    Basic processes of radiation damage of insulators by dense electronic excitation are reviewed. First it is pointed out that electronic excitation of nonmetallic solids produces the self-trapped excitons and defect-related metastable states having relatively long lifetimes, and that the excitation of these metastable states, produces stable defects. The effects of irradiation with heavy ions, including track registration, are surveyed on the basis of the microscopic studies. It is pointed out also that the excitation of the metastable states plays a role in laser-induced damage at relatively low fluences, while the laser damage has been reported to be governed by heating of free electrons produced by multiphoton excitation. Difference in the contributions of the excitation of metastable defects to laser-induced damage of surfaces, or laser ablation, and laser-induced bulk damage is stressed. (orig.)

  18. Projected quasiparticle theory for molecular electronic structure

    Scuseria, Gustavo E.; Jiménez-Hoyos, Carlos A.; Henderson, Thomas M.; Samanta, Kousik; Ellis, Jason K.

    2011-09-01

    We derive and implement symmetry-projected Hartree-Fock-Bogoliubov (HFB) equations and apply them to the molecular electronic structure problem. All symmetries (particle number, spin, spatial, and complex conjugation) are deliberately broken and restored in a self-consistent variation-after-projection approach. We show that the resulting method yields a comprehensive black-box treatment of static correlations with effective one-electron (mean-field) computational cost. The ensuing wave function is of multireference character and permeates the entire Hilbert space of the problem. The energy expression is different from regular HFB theory but remains a functional of an independent quasiparticle density matrix. All reduced density matrices are expressible as an integration of transition density matrices over a gauge grid. We present several proof-of-principle examples demonstrating the compelling power of projected quasiparticle theory for quantum chemistry.

  19. Studies in the electronic structure of matter

    Swarts, C.A.

    1979-01-01

    The results of various theories for the angular distribution of electrons photoemitted from the outermost p-shell of rare gas atoms are compared. The theories compared are the local density theories of Slater (X/sub α/) and of Hohenberg, Kohn and Sham, the pseudopotential method, Hartree-Fock theory as evaluated by Kennedy and Manson, and Amusia's random phase approximation with exchange (RPAE). Extended Huekel theory is applied to GaAs, GaP, and to the nitrogen isoelectronic trap in GaAs and GaP. The computer perfect crystal band structures are found to be in reasonable agreement with those computed with empirical pseudopotentials. Nitrogen impurity levels in GaAs and GaP are calculated using a cluster model. By means of model calculations for an independent electron metal, exact lineshapes are obtained for the photon absorption, emission and photoemission spectra of deep core states. 97 references

  20. Study and impact of fast electrons diagnosed by electron cyclotron radiation on Tore-Supra tokamak

    Gomez, P.

    1999-12-01

    This thesis aims at characterizing the dynamics of fast electrons generated by the Landau absorption of the hybrid wave and studying their effects on electron cyclotron radiation. The different processes involved in the propagation and resonant absorption of the hybrid wave in plasmas are described. A method such as ray-tracing allows the characterization of the dynamics of heating but this method relies on the hypothesis of geometrical optics. Whenever absorption rate is low as it is in Tore-Supra, the hybrid wave undergoes a series of successive reflections on the edge of the plasma before being completely absorbed. These reflections generate an electromagnetic chaos in which geometrical optics hypothesis are no longer valid. A statistical treatment of the Fokker-Planck equation allows the calculation of the mean distribution function of electrons in the plasma submitted to hybrid wave. The electron cyclotron radiation is then deduced and by assuming that plasma behaves like a black body, a theoretical radiative temperature is calculated. The confrontation of this theoretical temperature profile with experimental values allows the validation of this modeling and the estimation of the effects of fast electrons on temperature measurements. (A.C.)

  1. Radiation dosimetry in human bone using electron paramagnetic resonance

    Breen, S.L.

    1995-01-01

    Accurate measurements of dose in bone are required in order to improve the dosimetry of systemic radiotherapy for osseous metastases. Bone is an integrating dosimeter which records the radiation history of the skeleton. During irradiation, electrons become trapped in the crystalline component of bone mineral (hydroxyapatite). The traps are very stable; at room temperature, emptying of the traps occurs with a half-life of many years. The population of trapped unpaired electrons is proportional to the radiation dose administered to the bone and can be measured in excised bone samples using electron paramagnetic resonance (EPR). EPR spectra of synthetic hydroxyapatite, irradiated with Co-60, were obtained at room temperature and at 77 K. At room temperature, the radiation-induced signal, with a g-value of 2.001 ± 0.001 increased linearly with absorbed dose above a lower threshold of 3 Gy, up to doses of 200 Gy. In contrast with pure hydroxyapatite, EPR spectra of excised human bone showed a broad 'native' signal, due to the organic component of bone, which masks the dosimetrically important signal. This native signal is highly variable from sample to sample and precludes the use of EPR as an absolute dosimetry technique. However, after subtraction of the background signal, irradiated human bone showed a linear response with a lower limit of measurement similar to that of synthetic hydroxyapatite. Bone is an in vivo linear dosimeter which can be exploited to develop accurate estimates of the radiation dose delivered during systemic radiotherapy and teletherapy. However, improved sensitivity of the EPR dosimetry technique is necessary before it can be applied reliably in clinical situations. (author)

  2. Repetitive nanosecond electron accelerators type URT-1 for radiation technology

    Sokovnin, S. Yu.; Balezin, M. E.

    2018-03-01

    The electron accelerator URT-1М-300 for mobile installation was created for radiation disinfecting to correct drawbacks that were found the URT-1M electron accelerator operation (the accelerating voltage up to 1 МV, repetition rate up to 300 pps, electron beam size 400 × 100 mm, the pulse width about 100 ns). Accelerator configuration was changed that allowed to reduce significantly by 20% tank volume with oil where is placed the system of formation high-voltage pulses, thus the average power of the accelerator is increased by 6 times at the expense of increase in pulses repetition rate. Was created the system of the computerized monitoring parameters (output parameters and thermal mode) and remote control of the accelerator (charge voltage, pulse repetition rate), its elements and auxiliary systems (heat of the thyratron, vacuum system), the remote control panel is connected to the installation by the fiber-optical channel, what lightens the work for service personnel. For generating an electron beam up to 400 mm wide there are used metal- ceramic] and metal-dielectric cold cathodes of several emission elements (plates) with a non-uniform distribution of the electron beam current density on the output foil ± 15%. It was found that emission drop of both type of cathodes, during the operation at the high repetition rate (100 pps) is substantial at the beginning of the process, and then proceeds rather slowly that allows for continuous operation up to 40 h. Experiments showed that linear dependence of the voltage and a signal from the pin-diode remains within the range of the charge voltage 45-65 kV. Thus, voltage increases from 690 to 950 kV, and the signal from the pin-diode - from (2,8-4,6)*104 Gy/s. It allows to select electron energy quite precisely with consideration of the radiation technology requirements.

  3. Studies in the electronic structure of matter

    Miller, D.L.

    1979-01-01

    KLL Auger transition rates for helium are computed using simple atomic orbital wavefunctions which take into account the difference in average electron--electron repulsion of initial and final states. The results are consistent with transition rates computed by other authors using a variety of many-electron techniques. It is suggested that wavefunctions determined in the manner described provide a useful representation of the autoionizing state within the first Bohr radius. A method for extracting atomic pseudopotentials from photoelectron angular distributions is described and applied photoionization of the outermost p shells of Ar, Kr, and Xe and to the 4d shell of Xe. The pseudopotentials obtained reproduce the data, and also predict accurate cross sections and phase shifts for photoelectron energies up to 100 eV. It is suggested that the pseudopotentials aptly mimic the effects of intrashell electron--electron correlations in the photoionization process. The extended Hueckel theory is applied to the nitrogen trap in GaAs and GaP. Perfect crystal band structures are computed and are shown to be in reasonable agreement with those computed with empirical pseudopotentials. Nitrogen impurity levels in GaAs and GaP are computed using an extended Hueckel cluster model. In each case the model predicts two states within the band gap, in contrast to experiment which detects one impurity state in GaP and none in GaAs. It is suggested that the choice of cluster used unrealistically concentrates states near the conduction band edge on the central atom

  4. Studies in the electronic structure of matter

    Miller, D.L.

    1979-01-01

    KLL Auger transition rates for helium are computed using simple atomic orbital wavefunctions which take into account the difference in average electron-electron repulsion of initial and final states. The results are consistent with transition rates computed by other authors using a variety of many-electron techniques. It is suggested that wavefunctions determined in the manner described provide a useful representation of the autoionizing state within the first Bohr radius. A method for extracting atomic psuedopotentials from photoelectron angular distributions is described and applied photoionization of the outermost p shells of Ar, Kr, and Xe and to the 4d shell of Xe. The pseudopotentials obtained reproduce the data, and also predict accurate cross sections and phase shifts for photoelectron energies up to 100 eV. It is suggested that the pseudopotentials aptly mimic the effects of intrashell electron-electron correlations in the photoionization process. The extended Hueckel theory is applied to the nitrogen trap in GaAs and GaP. Perfect crystal band structures are computed and are shown to be in reasonable agreement with those computed with empirical psuedopotentials. Nitrogen impurity levles in GaAs and GaP are computed using an extended Hueckel cluster model. In each case the model predicts two states within the band gap, in contrast to experiment which detects one impurity state in GaP and none in GaAs. It is suggested that the choice of cluster used unrealistically concentrates states near the conduction band edge on the central atom

  5. Electronic structure of defects in semiconductor heterojunctions

    Haussy, Bernard; Ganghoffer, Jean Francois

    2002-01-01

    Full text.heterojunctions and semiconductors and superlattices are well known and well used by people interested in optoelectronics communications. Components based on the use of heterojunctions are interesting for confinement of light and increase of quantum efficiency. An heterojunction is the contact zone between two different semiconductors, for example GaAs and Ga 1-x Al x As. Superlattices are a succession of heterojunctions (up to 10 or 20). These systems have been the subjects of many experiments ao analyse the contact between semiconductors. They also have been theoretically studied by different types of approach. The main result of those studies is the prediciton of band discontinuities. Defects in heterojunctions are real traps for charge carriers; they can affect the efficiency of the component decreasing the currents and the fluxes in it. the knowledge of their electronic structure is important, a great density of defects deeply modifies the electronic structure of the whole material creating real new bands of energy in the band structure of the component. in the first part of this work, we will describe the heterostructure and the defect in terms of quantum wells and discrete levels. This approach allows us to show the role of the width of the quantum well describing the structure but induces specific behaviours due to the one dimensional modelling. Then a perturbative treatment is proposed using the Green's functions formalism. We build atomic chains with different types of atoms featuring the heterostructure and the defect. Densities of states of a structure with a defect and levels associated to the defect are obtained. Results are comparable with the free electrons work, but the modelling do not induce problems due to a one dimensional approach. To extend our modelling, a three dimensions approach, based on a cavity model, is investigated. The influence of the defect, - of hydrogenoid type - introduced in the structure, is described by a cavity

  6. Atomic Reference Data for Electronic Structure Calculations

    Kotochigova, S; Shirley, E L

    We have generated data for atomic electronic structure calculations, to provide a standard reference for results of specified accuracy under commonly used approximations. Results are presented here for total energies and orbital energy eigenvalues for all atoms from H to U, at microHartree accuracy in the total energy, as computed in the local-density approximation (LDA) the local-spin-density approximation (LSD); the relativistic local-density approximation (RLDA); and scalar-relativistic local-density approximation (ScRLDA).

  7. The electronic structure of impurities in semiconductors

    Nylandsted larsen, A; Svane, A

    2002-01-01

    The electronic structure of isolated substitutional or interstitial impurities in group IV, IV-IV, and III-V compound semiconductors will be studied. Mössbauer spectroscopy will be used to investigate the incorporation of the implanted isotopes on the proper lattice sites. The data can be directly compared to theoretical calculations using the LMTO scheme. Deep level transient spectroscopy will be used to identify the band gap levels introduced by metallic impurities, mainly in Si~and~Si$ _{x}$Ge$_{1-x}$. \\\\ \\\\

  8. Unoccupied surface electronic structure of Gd(0001)

    Li, D.; Dowben, P.A.; Ortega, J.E.; Himpsel, F.J.

    1994-01-01

    The unoccupied surface electronic structure of Gd(0001) was investigated with high-resolution inverse-photoemission spectroscopy. An empty surface state near E F is observed at bar Γ. Two other surface-sensitive features are also revealed at 1.2 and 3.1 eV above the Fermi level. Hydrogen adsorption on Gd surfaces was used to distinguish the surface-sensitive features from the bulk features. The unoccupied bulk-band critical points are determined to be Γ 3 + at 1.9 eV and A 1 at 0.8 eV

  9. Cobalamins uncovered by modern electronic structure calculations

    Kepp, Kasper Planeta; Ryde, Ulf

    2009-01-01

    electronic-structure calculations, in particular density functional methods, the understanding of the molecular mechanism of cobalamins has changed dramatically, going from a dominating view of trans-steric strain effects to a much more complex view involving an arsenal of catalytic strategies. Among...... these are cis-steric distortions, electrostatic stabilization of radical products, the realization that nucleotide units can serve as polar handles, and the careful design of the active sites, with polar residues in the radical enzymes and non-polar residues in the transferases. Together, these strategies...

  10. Electronic golden structure of the periodic chart

    Malinowski, Leonard J. [Interdisciplinary Research Club, Monroeville, PA (United States)], E-mail: LJMalinowski@gmail.com

    2009-11-15

    The golden ratio has been studied since the ancient Greeks due to its inherent symmetry and aesthetic beauty, especially in the five Platonic Solids. The golden mean is now established as a pillar of El Naschie's E infinity where it achieves the physical manifestation of 0.618 034 MeV. The largest atomic electron orbital total energies average to the golden mean energy. This paper examines the golden ratio in order to expand upon a century old attempt to produce a relatively static, visual, geometric model of atomic structure.

  11. Electronic golden structure of the periodic chart

    Malinowski, Leonard J.

    2009-01-01

    The golden ratio has been studied since the ancient Greeks due to its inherent symmetry and aesthetic beauty, especially in the five Platonic Solids. The golden mean is now established as a pillar of El Naschie's E infinity where it achieves the physical manifestation of 0.618 034 MeV. The largest atomic electron orbital total energies average to the golden mean energy. This paper examines the golden ratio in order to expand upon a century old attempt to produce a relatively static, visual, geometric model of atomic structure.

  12. Electronic structure of A15 compounds

    Pickett, W.E.

    1980-01-01

    For the past twenty-five years compounds with the A15 crystal structure have dominated the class of high temperature superconductors. The crystal structure of an A15 compound A 3 B is cubic (space group O/sub h/ 3 ). However, the site symmetry (D/sub 2d/) of the A atoms is much lower than cubic, an unusual occurrence in cubic binary compounds. Variations on this theme have supplied the basis of many theoretical models of the anomalous temperature (T) dependence of normal state properties and the low temperature cubic reversible tetragonal structural transformations which accompany high values of T/sub c/ in A15 compounds. In this paper results of self-consistent pseudopotential band structure calculations are used to assess some important aspects of the unique and unusual behavior in A15 compounds: (1) the role of the B atom in determining the overall electronic structure will be shown to be important; (2) the effect of the low site symmetry of the A atom on the charge density and potential will be assessed; and (3) the bonding will be shown to be metallic-covalent with no significant A-B charge transfer

  13. Statistical studies of energetic electrons in the outer radiation belt

    Johnstone, A.D.; Rodgers, D.J.; Jones, G.H. E-mail: g.h.jones@ic.ac.uk

    1999-10-01

    The medium electron A (MEA) instrument aboard the CRRES spacecraft provided data on terrestrial radiation belt electrons in the energy range from 153 to 1582 keV, during 1990-91. These data have previously been used to produce an empirical model of the radiation belts from L=1.1 to 8.9, ordered according to 17 energy bands, 18 pitch angle bins, and 5 Kp ranges. Empirical models such as this are very valuable, but are prone to statistical fluctuations and gaps in coverage. In this study, in order to smooth the data and make it more easy to interpolate within data gaps, the pitch angle distribution at each energy in the model was fitted with a Bessel function. This provided a way to characterize the pitch angle in terms of only two parameters for each energy. It was not possible to model fluxes reliably within the loss cone because of poor statistics. The fitted distributions give an indication of the way in which pitch angle diffusion varies in the outer radiation belts. The two parameters of the Bessel function were found to vary systematically with L value, energy and Kp. Through the fitting of a simple function to these systematic variations, the number of parameters required to describe the model could be reduced drastically.

  14. Electronic structure of hcp transition metals

    Jepsen, O.; Andersen, O. Krogh; Mackintosh, A. R.

    1975-01-01

    Using the linear muffin-tin-orbital method described in the previous paper, we have calculated the electronic structures of the hcp transition metals, Zr, Hf, Ru, and Os. We show how the band structures of these metals may be synthesized from the sp and d bands, and illustrate the effects...... of hybridization, relativistic band shifts, and spin-orbit coupling by the example of Os. By making use of parameters derived from the muffin-tin potential, we discuss trends in the positions and widths of the energy bands, especially the d bands, as a function of the location in the periodic table. The densities...... of states of the four metals are presented, and the calculated heat capacities compared with experiment. The Fermi surfaces of both Ru and Os are found to be in excellent quantitative agreement with de Haas-van Alphen measurements, indicating that the calculated d-band position is misplaced by less than 10...

  15. Experimental Benchmarking of Pu Electronic Structure

    Tobin, J.G.; Moore, K.T.; Chung, B.W.; Wall, M.A.; Schwartz, A.J.; Ebbinghaus, B.B.; Butterfield, M.T.; Teslich, N.E. Jr.; Bliss, R.A.; Morton, S.A.; Yu, S.W.; Komesu, T.; Waddill, G.D.; van der Laan, G.; Kutepov, A.L.

    2008-01-01

    The standard method to determine the band structure of a condensed phase material is to (1) obtain a single crystal with a well defined surface and (2) map the bands with angle resolved photoelectron spectroscopy (occupied or valence bands) and inverse photoelectron spectroscopy (unoccupied or conduction bands). Unfortunately, in the case of Pu, the single crystals of Pu are either nonexistent, very small and/or having poorly defined surfaces. Furthermore, effects such as electron correlation and a large spin-orbit splitting in the 5f states have further complicated the situation. Thus, we have embarked upon the utilization of unorthodox electron spectroscopies, to circumvent the problems caused by the absence of large single crystals of Pu with well-defined surfaces. Our approach includes the techniques of resonant photoelectron spectroscopy, x-ray absorption spectroscopy, electron energy loss spectroscopy, Fano Effect measurements, and Bremstrahlung Isochromat Spectroscopy, including the utilization of micro-focused beams to probe single-crystallite regions of polycrystalline Pu samples.

  16. Deep learning and the electronic structure problem

    Mills, Kyle; Spanner, Michael; Tamblyn, Isaac

    In the past decade, the fields of artificial intelligence and computer vision have progressed remarkably. Supported by the enthusiasm of large tech companies, as well as significant hardware advances and the utilization of graphical processing units to accelerate computations, deep neural networks (DNN) are gaining momentum as a robust choice for many diverse machine learning applications. We have demonstrated the ability of a DNN to solve a quantum mechanical eigenvalue equation directly, without the need to compute a wavefunction, and without knowledge of the underlying physics. We have trained a convolutional neural network to predict the total energy of an electron in a confining, 2-dimensional electrostatic potential. We numerically solved the one-electron Schrödinger equation for millions of electrostatic potentials, and used this as training data for our neural network. Four classes of potentials were assessed: the canonical cases of the harmonic oscillator and infinite well, and two types of randomly generated potentials for which no analytic solution is known. We compare the performance of the neural network and consider how these results could lead to future advances in electronic structure theory.

  17. Electron acceleration and radiation signatures in loop coronal transients

    Vlahos, L.; Gergely, T.E.; Papadopoulos, K.

    1982-01-01

    A model for electron aceleration in loop coronal transients is suggested. We propose that in these transients an erupting loop moves away from the solar surface, with a velocity greater than the local Alfven speed, pushing against the overlying magnetic fields and driving a shock in the front of the moving part of the loop. We suggest that lower hybrid waves are excited at the shock front and propagate radially toward the center of the loop with phase velocity along the magnetic field which exceeds the thermal velocity. The lower hybrid waves stochastically accelerate the tail of the electron distribution inside the loop. We discuss how the accelerated electrons are trapped in the moving loop and give a rough estimate of their radiation signature. We find that plasma radiation can explain the power observed in stationary and moving type IV bursts. We discuss some of the conditions under which moving or stationary type IV bursts are expected to be associated with loop coronal transients

  18. The surface electronic structure of Y(0001)

    Searle, C.

    1998-12-01

    Yttrium has been grown epitaxially on W(110). The growth was monitored by using photoemission spectroscopy with a synchrotron radiation source. The film thickness has been gauged by the attenuation of the W 4f 7/2 bulk component. The films have been grown reproducibly and show a prominent surface state which is indicative of good order and low contamination. Angle-Resolved Ultra-Violet Photoemission Spectroscopy has been used to examine the valence band of these ultra-thin films. The films show a very different structure to the valence band of a bulk crystal of yttrium. The differences have been investigated by a series of model calculations using the LMASA-46 tight-binding LMTO program. The calculations suggest that the ultra-thin film surface state may be hybridised with a tungsten orbital having (x 2 - y 2 ) character. (author)

  19. Structure and navigation for electronic publishing

    Tillinghast, John; Beretta, Giordano B.

    1998-01-01

    The sudden explosion of the World Wide Web as a new publication medium has given a dramatic boost to the electronic publishing industry, which previously was a limited market centered around CD-ROMs and on-line databases. While the phenomenon has parallels to the advent of the tabloid press in the middle of last century, the electronic nature of the medium brings with it the typical characteristic of 4th wave media, namely the acceleration in its propagation speed and the volume of information. Consequently, e-publications are even flatter than print media; Shakespeare's Romeo and Juliet share the same computer screen with a home-made plagiarized copy of Deep Throat. The most touted tool for locating useful information on the World Wide Web is the search engine. However, due to the medium's flatness, sought information is drowned in a sea of useless information. A better solution is to build tools that allow authors to structure information so that it can easily be navigated. We experimented with the use of ontologies as a tool to formulate structures for information about a specific topic, so that related concepts are placed in adjacent locations and can easily be navigated using simple and ergonomic user models. We describe our effort in building a World Wide Web based photo album that is shared among a small network of people.

  20. Electronic structure and superconductivity of fcc Cr

    Xu, J.; Freeman, A.J.; Jarlborg, T.; Brodsky, M.B.

    1984-01-01

    Results of self-consistent electronic structure calculations are reported for metastable fcc Cr metal. Unlike the case of bcc Cr which has E/sub F/ at a minimum in the density of states (DOS), the DOS at E/sub F/ in fcc Cr is at a peak making this one of the higher-DOS metals with the fcc structure (e.g., comparable with that of Ni and Pt). A calculated Stoner factor of 0.82 indicates that ferromagnetic ordering is not expected. Calculations of the electron-phonon coupling parameter lambda and superconducting transition temperature T/sub c/ were made using the rigid-ion approximation and strong-coupling theory with various estimates of the (unknown) phonon contribution. We conclude that T/sub c/'sroughly-equal2.5 K are reasonable, although they are substantially smaller than the T/sub c/roughly-equal10 K derived from measurements on Au-Cr-Au sandwiches

  1. Response of radiation monitoring labels to gamma rays and electrons

    Rahim, F. Abdel; Miller, Arne; McLaughlin, W.L.

    1985-01-01

    or location has been irradiated to high doses. Among labels available worldwide, a few are suitable for indicating absorbed dose regions of slightly less than 104 Gy (monitoring high dose ranges (i.e., sterilization dose levels of > 104 Gy or > 1 Mrad), and in some cases......, and differences in dose rate and radiation type (gamma rays and electron beams) were made on 15 kinds of labels. The results show that, for many types of indicators, diverse effects may give misleading conclusions unless countermeasures are taken. For example, some of the most commonly used labels, which contain...... permit somewhat more precise discrimination of dose levels, and may sometimes be useful for monitoring differences in local dose distributions or area monitoring of radiation damage probabilities around particle accelerators or large radionuclide sources....

  2. Notification determining technical standards concerning prevention of radiation injuries by electron capture detectors for gas chromatography

    1981-01-01

    This rule is established under the provisions of the law on the prevention of radiation injuries by radioisotopes, the ordinance and the regulation for the execution of the law. This rule is applied to electron capture detectors for gas chromatography under the law. Basic terms are defined, such as detector radiation source, detector container and carrier gas. The detectors shall consist of detector radiation sources and containers, and the containers must be such that the radiation sources can not be easily taken away and never cause the danger to fall off. The induction and discharge mouths of the detector containers shall be shut tightly with caps, etc. The main structures and radiation sources of detectors shall be made of materials, which are difficult to corrode, and do not melt and easily cause chemical change below 800 deg. C. Detector radiation sources shall be made of metals plated with nickel 63 less than 20 milli-curie. The radiation dose rate on the surface of a detector shall be shielded to less than 0.06 milli-rem an hour. The temperature of detectors and carrier gas shall not exceed 350 deg. C. Corrosive gas shall not be used as carrier gas. The period of effective indication is 5 years. The method of washing, and the conditions of leak, heat-resistance and shock-resistance examinations are defined, respectively. (Okada, K.)

  3. Radiation-induced structural changes. 3

    Kondo, Yasuhiro; Matsuyama, Tomochika; Ogasawara, Masaaki

    1993-05-01

    This meeting is the fourth of series meetings on the structural change in materials induced by ionizing radiation. The present meeting was organized to discuss specifically on the x-ray storage phosphors such as BaFBr:Eu 2+ or RbI x Br 1-x :Tl and to get a clear understanding of the present status of the research on the storage mechanisms, nature of the rare earth impurities, and the optical properties of BaFBr. It was also expected that all the participants became aware of unsolved problems in these storage materials and that some of them would start research work on the storage phosphors. Therefore this report was edited mainly to provide basic knowledge correlated with the storage phosphors and related phenomena rather than to report simply on the experimental results. (J.P.N.)

  4. Electronic structure of Ca, Sr, and Ba under pressure.

    Animalu, A. O. E.; Heine, V.; Vasvari, B.

    1967-01-01

    Electronic band structure calculations phase of Ca, Sr and Ba over wide range of atomic volumes under pressure electronic band structure calculations for fcc phase of Ca, Sr and Ba over wide range of atomic volumes under pressure electronic band structure calculations for fcc phase of Ca, Sr and Ba over wide range of atomic volumes under pressure

  5. An Overview of Effects of Space Radiation on the Electronics

    Hwang, Sun Tae; Shin, Dong Kwan; Son, Young Jong; Kim Jin Hong

    2009-01-01

    The first Korean astronaut successfully carried out the scientific experiments at International Space Station (ISS) in April 2008. Due to the government's strong will and support for the field of space, Korea has enhanced its space technology based on the accomplishments in space development. On October 12∼16, 2009 the 60 th International Astronautical Congress (IAC) was held in Daejeon. IAC 2009 must serve as a place for the extensive exchange of global space technology and information in order to speed up the development of space technology in Korea. With regard for space research and development, the radiation effects in space have been reviewed from the viewpoint of electronics

  6. New generation of compact electron accelerators for radiation technologies

    Auslender, V.L.; Balakin, V.E.; Kraynov, G.S.

    1995-01-01

    Compact electron accelerators with energy range 0.25-1.0 MeV and beam power up to 32 kw are described. The feeding high voltage is formed by converter (working frequency 20 khz), coreless step-up transformer and a set of rectifying sections. The rectifying multiplier circuit used in rectifying sections permits to reach voltage gradient along accelerator's axis up to 14 kV/cm. The accelerators with vertical and horizontal position are described. The accelerators can be produced together with local radiation shielding and various underbeam transportation systems for irradiation of different products. Such version can be installed in any room facing general requirements for electric equipment

  7. First observation of Smith-Purcell radiation from relativistic electrons

    Doucas, G.; Mulvey, J.H.; Omori, M.; Walsh, J.; Kimmitt, M.F.

    1992-01-01

    A beam of 3.6 MeV electrons has been used to study the generation of radiation in far infra-red (FIR) by the Smith-Purcell mechanism. The dependence of wavelength on angle of emission, over angles from 56 deg to 150 deg and wavelengths from 350 μm to 1860 μm, is in excellent agreement with the Smith-Purcell dispersion relation. Comparison of the yield with that from a 5000 K source suggests that the spontaneous Smith-Purcell effect offers an easily tunable alternative to the synchrotron as a coherent FIR source, and could form the basis of a cheap, compact Free Electron Laser (FEL). (author) 6 refs.; 5 figs

  8. Challenges in validating radiation sterilization with low energy electron irradiation

    Miller, A.; Helt-Hansen, J.

    2011-01-01

    Complete text of publication follows. Low energy electron irradiation (80-300 keV) is used increasingly for sterilization or decontamination in connection with isolators for aseptic filling lines in the pharmaceutical industry. It is not defined how validation for this process shall be carried out. A method can be derived from the medical device standard for radiation sterilization, ISO 11137, because the principles described in this standard can be applied to almost any industrial irradiation process. The validations elements are: Process definition, concerning specification of the dose required for the process and the maximum acceptable dose for the product. Installation qualification, concerning acceptance the irradiation facility. Operational qualification, concerning characterization of the facility. Performance qualification, concerning setting up the process. Process control, concerning routine monitoring. The limited penetration of the low energy electrons leads to problems with respect to executing these validation steps. This paper discusses these problems, and shows with examples how they can be solved.

  9. Radiation-Hardened Electronics for Advanced Communications Systems

    Whitaker, Sterling

    2015-01-01

    Novel approach enables high-speed special-purpose processors Advanced reconfigurable and reprogrammable communication systems will require sub-130-nanometer electronics. Legacy single event upset (SEU) radiation-tolerant circuits are ineffective at speeds greater than 125 megahertz. In Phase I of this project, ICs, LLC, demonstrated new base-level logic circuits that provide SEU immunity for sub-130-nanometer high-speed circuits. In Phase II, the company developed an innovative self-restoring logic (SRL) circuit and a system approach that provides high-speed, SEU-tolerant solutions that are effective for sub-130-nanometer electronics scalable to at least 22-nanometer processes. The SRL system can be used in the design of NASA's next-generation special-purpose processors, especially reconfigurable communication processors.

  10. Electric radiation mapping of silver/zinc oxide nanoantennas by using electron holography

    Sanchez, J. E.; Mendoza-Santoyo, F.; Cantu-Valle, J.; Velazquez-Salazar, J.; José Yacaman, M.; Ponce, A. [Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio 78249 (United States); González, F. J. [Coordinación para la Innovación y la Aplicación de la Ciencia y la Tecnología, Universidad Autónoma de San Luís Potosí, San Luis Potosí 78210 (Mexico); Diaz de Leon, R. [Instituto Tecnológico de San Luis Potosí, San Luis Potosi 78437 (Mexico)

    2015-01-21

    In this work, we report the fabrication of self-assembled zinc oxide nanorods grown on pentagonal faces of silver nanowires by using microwaves irradiation. The nanostructures resemble a hierarchal nanoantenna and were used to study the far and near field electrical metal-semiconductor behavior from the electrical radiation pattern resulting from the phase map reconstruction obtained using off-axis electron holography. As a comparison, we use electric numerical approximations methods for a finite number of ZnO nanorods on the Ag nanowires and show that the electric radiation intensities maps match closely the experimental results obtained with electron holography. The time evolution of the radiation pattern as generated from the nanostructure was recorded under in-situ radio frequency signal stimulation, in which the generated electrical source amplitude and frequency were varied from 0 to 5 V and from 1 to 10 MHz, respectively. The phase maps obtained from electron holography show the change in the distribution of the electric radiation pattern for individual nanoantennas. The mapping of this electrical behavior is of the utmost importance to gain a complete understanding for the metal-semiconductor (Ag/ZnO) heterojunction that will help to show the mechanism through which these receiving/transmitting structures behave at nanoscale level.

  11. Examining Relativistic Electron Loss in the Outer Radiation Belt

    Green, J. C.; Onsager, T. G.; O'Brien, P.

    2003-12-01

    Since the discovery of earth's radiation belts researchers have sought to identify the mechanisms that dictate the seemingly erratic relativistic electron flux levels in the outer belt. Contrary to intuition, relativistic electron flux levels do not always increase during geomagnetic storms even though these storms signify enhanced energy input from the solar wind to the magnetosphere [Reeves et al., 2003; O'Brien et al., 2001]. The fickle response of the radiation belt electrons to geomagnetic activity suggests that flux levels are determined by the outcome of a continuous competition between acceleration and loss. Some progress has been made developing and testing acceleration mechanisms but little is known about how relativistic electrons are lost. We examine relativistic electron losses in the outer belt focusing our attention on flux decrease events of the type first described by Onsager et al. [2002]. The study showed a sudden decrease of geosynchronous >2MeV electron flux occurring simultaneously with local stretching of the magnetic field. The decrease was first observed near 15:00 MLT and progressed to all local times after a period of ˜10 hours. Expanding on the work of Onsager et al. [2002], we have identified ˜ 51 such flux decrease events in the GOES and LANL data and present the results of a superposed epoch analysis of solar wind data, geomagnetic activity indicators, and locally measured magnetic field and plasma data. The analysis shows that flux decreases occur after 1-2 days of quiet condition. They begin when either the solar wind dynamic pressure increases or Bz turns southward pushing hot dense plasma earthward to form a partial ring current and stretched magnetic field at dusk. Adiabatic electron motion in response to the stretched magnetic field may explain the initial flux reduction; however, often the flux does not recover with the magnetic field recovery, indicating that true loss from the magnetosphere is occurring. Using Polar and

  12. Transition radiation spectra of electrons from 1 to 10 GeV/c in regular and irregular radiators

    Andronic, A.; Appelshaeuser, H.; Bailhache, R.; Baumann, C.; Braun-Munzinger, P.; Bucher, D.; Busch, O.; Catanescu, V.; Chernenko, S.; Christakoglou, P.; Fateev, O.; Freuen, S.; Garabatos, C.; Gottschlag, H.; Gunji, T.; Hamagaki, H.; Herrmann, N.; Hoppe, M.; Lindenstruth, V.; Lippmann, C.; Morino, Y.; Panebratsev, Yu.; Petridis, A.; Petrovici, M.; Rusanov, I.; Sandoval, A.; Saito, S.; Schicker, R.; Soltveit, H.K.; Stachel, J.; Stelzer, H.; Vassiliou, M.; Vulpescu, B.; Wessels, J.P.; Wilk, A.; Yurevich, V.; Zanevsky, Yu.

    2006-01-01

    We present measurements of the spectral distribution of transition radiation generated by electrons of momentum 1-10 GeV/c in different radiator types. We investigate periodic foil radiators and irregular foam and fiber materials. The transition radiation photons are detected by prototypes of the drift chambers to be used in the Transition Radiation Detector (TRD) of the ALICE experiment at CERN, which are filled with a Xe, CO 2 (15%) mixture. The measurements are compared to simulations in order to enhance the quantitative understanding of transition radiation production, in particular the momentum dependence of the transition radiation yield

  13. Electron paramagnetic resonance biophysical radiation dosimetry with tooth enamel

    Khan, Rao F.H.

    2003-01-01

    This thesis deals with the advancements made in the field of Electron Paramagnetic Resonance (EPR) for biophysical dosimetry with tooth enamel for accident, emergency, and retrospective radiation dose reconstruction. A methodology has been developed to measure retrospective radiation exposures in human tooth enamel. This entails novel sample preparation procedures with minimum mechanical treatment to reduce the preparation induced uncertainties, establish optimum measurement conditions inside the EPR cavity, post-process the measured spectrum with functional simulation of dosimetric and other interfering signals, and reconstruct dose. By using this technique, retrospective gamma exposures as low as 80±30 mGy have been successfully deciphered. The notion of dose modifier was introduced in EPR biodosimetry for low dose measurements. It has been demonstrated that by using the modified zero added dose (MZAD) technique for low radiation exposures, doses in 100 mGy ranges can be easily reconstructed in teeth that were previously thought useless for EPR dosimetry. Also, the use of a dose modifier makes robust dose reconstruction possible for higher radiation exposures. The EPR dosimetry technique was also developed for tooth samples extracted from rodents, which represent small tooth sizing. EPR doses in the molars, extracted from the mice irradiated with whole body exposures, were reassessed and shown to be correct within the experimental uncertainty. The sensitivity of human tooth enamel for neutron irradiation, obtained from the 3 MV McMaster K.N. Van de Graaff accelerator, was also studied. For the first time this work has shown that the neutron sensitivity of the tooth enamel is approximately 1/10th of the equivalent gamma sensitivity. Parametric studies for neutron dose rate and neutron energy within the available range of the accelerator, showed no impact on the sensitivity of the tooth enamel. Therefore, tooth enamel can be used as a dosimeter for both neutrons

  14. Electronic structure of MnSi : The role of electron-electron interactions

    Carbone, F; Zangrando, M; Brinkman, A; Nicolaou, A; Bondino, F; Magnano, E; Nugroho, A. A.; Parmigiani, F; Jarlborg, T; van der Marel, D

    We present an experimental study of the electronic structure of MnSi. Using x-ray absorption spectroscopy (XAS), x-ray photoemission, and x-ray fluorescence, we provide experimental evidence that MnSi has a mixed valence ground state. We show that self-consistent local density approximation

  15. Electronic structure of MnSi: The role of electron-electron interactions

    Carbone, F.; Zangrando, M.; Brinkman, Alexander; Nicolaou, A.; Bondino, F.; Magnano, E.; Nugroho, A.A.; Parmigiani, F.; Jarlborg, Th.; van der Marel, D.

    2006-01-01

    We present an experimental study of the electronic structure of MnSi. Using x-ray absorption spectroscopy (XAS), x-ray photoemission, and x-ray fluorescence, we provide experimental evidence that MnSi has a mixed valence ground state. We show that self-consistent local density approximation

  16. Ultra-short coherent terahertz radiation from ultra-short dips in electron bunches circulating in a storage ring

    Yamamoto, N.; Shimada, M.; Adachi, M.; Zen, H.; Tanikawa, T.; Taira, Y.; Kimura, S.; Hosaka, M.; Takashima, Y.; Takahashi, T.; Katoh, M.

    2011-01-01

    Terahertz (THz) coherent synchrotron radiation (CSR) is emitted not only from ultra-short electron bunches, but also from electron bunches with micro-structures. Formation of micro-structures at the sub-picosecond scale in electron bunches by a laser slicing technique is experimentally studied through observation of the THz CSR. The THz CSR spectrum was found to depend strongly on the intensity and the pulse width of the laser. The results agreed qualitatively with a numerical simulation. It was suggested that the evolution of the micro-structure during CSR emission is important under some experimental conditions.

  17. Fingerprint-based structure retrieval using electron density.

    Yin, Shuangye; Dokholyan, Nikolay V

    2011-03-01

    We present a computational approach that can quickly search a large protein structural database to identify structures that fit a given electron density, such as determined by cryo-electron microscopy. We use geometric invariants (fingerprints) constructed using 3D Zernike moments to describe the electron density, and reduce the problem of fitting of the structure to the electron density to simple fingerprint comparison. Using this approach, we are able to screen the entire Protein Data Bank and identify structures that fit two experimental electron densities determined by cryo-electron microscopy. Copyright © 2010 Wiley-Liss, Inc.

  18. Electron Liquids in Semiconductor Quantum Structures

    Pinczuk, Aron

    2009-01-01

    The groups led by Stormer and Pinczuk have focused this project on goals that seek the elucidation of novel many-particle effects that emerge in two-dimensional electron systems (2DES) as the result from fundamental quantum interactions. This experimental research is conducted under extreme conditions of temperature and magnetic field. From the materials point of view, the ultra-high mobility systems in GaAs/AlGaAs quantum structures continue to be at the forefront of this research. The newcomer materials are based on graphene, a single atomic layer of graphite. The graphene research is attracting enormous attention from many communities involved in condensed matter research. The investigated many-particle phenomena include the integer and fractional quantum Hall effect, composite fermions, and Dirac fermions, and a diverse group of electron solid and liquid crystal phases. The Stormer group performed magneto-transport experiments and far-infrared spectroscopy, while the Pinczuk group explores manifestations of such phases in optical spectra.

  19. Electrons and photons in periodic structures

    Pedersen, Jesper Goor

    . In particular, the modulation leads to the emergence of band gaps, which are accompanied by a strongly modified density of states near and within the band gap. The main focus is on two applications of such modified densities of states. Firstly, the intentional introduction of defects in an otherwise perfectly...... periodic modulation of an electron gas leads to the emergence of localized defect states with energies within the band gap, where no propagating modes exist. Secondly, the divergence of the photonic density of states near a photonic band gap leads to strongly modified light-matter interactions, which has...... of the density of states near the band gap edge. Using a perturbative approach, we demonstrate certain limits of the attainable slow down factors due to broadening of electromagnetic modes. We discuss the effect of damping due to a finite conductivity as well as structural disorder, and provide a common...

  20. Electronic structure of single crystal C60

    Wu, J.; Shen, Z.X.; Dessau, D.S.; Cao, R.; Marshall, D.S.; Pianetta, P.; Lindau, I.; Yang, X.; Terry, J.; King, D.M.; Wells, B.O.; Elloway, D.; Wendt, H.R.; Brown, C.A.; Hunziker, H.; Vries, M.S. de

    1992-01-01

    We report angle-resolved photoemission data from single crystals of C 60 cleaved in UHV. Unlike the other forms of pure carbon, the valence band spectrum of C 60 consists of many sharp features that can be essentially accounted for by the quantum chemical calculations describing individual molecules. This suggests that the electronic structure of solid C 60 is mainly determined by the bonding interactions within the individual molecules. We also observe remarkable intensity modulations of the photoemission features as a function of photon energy, suggesting strong final state effects. Finally, we address the issue of the band width of the HOMO state of C 60 . We assert that the width of the photoemission peak of C 60 does not reflect the intrinsic band width because it is broadened by the non 0-0 transitions via the Franck-Condon principle. Our view point provides a possible reconciliation between these photoemission data and those measured by other techniques. (orig.)

  1. Multilevel domain decomposition for electronic structure calculations

    Barrault, M.; Cances, E.; Hager, W.W.; Le Bris, C.

    2007-01-01

    We introduce a new multilevel domain decomposition method (MDD) for electronic structure calculations within semi-empirical and density functional theory (DFT) frameworks. This method iterates between local fine solvers and global coarse solvers, in the spirit of domain decomposition methods. Using this approach, calculations have been successfully performed on several linear polymer chains containing up to 40,000 atoms and 200,000 atomic orbitals. Both the computational cost and the memory requirement scale linearly with the number of atoms. Additional speed-up can easily be obtained by parallelization. We show that this domain decomposition method outperforms the density matrix minimization (DMM) method for poor initial guesses. Our method provides an efficient preconditioner for DMM and other linear scaling methods, variational in nature, such as the orbital minimization (OM) procedure

  2. Undulator commissioning by characterization of radiation in x-ray free electron lasers

    Takashi Tanaka

    2012-11-01

    Full Text Available In x-ray free electron lasers (XFELs where a long undulator composed of many segments is installed, there exist a number of error sources to reduce the FEL gain such as the trajectory error, K value discrepancy, and phase mismatch, which are related to the segmented-undulator structure. Undulator commissioning, which refers to the tuning and alignment processes to eliminate the possible error sources, is thus an important step toward realization of lasing. In the SPring-8 angstrom compact free electron laser (SACLA facility, the undulator commissioning has been carried out by means of characterization of x-ray radiation, i.e., measurements of the spatial and spectral profiles of monochromatized spontaneous undulator radiation as well as by probing the FEL intensity. The achieved tuning and alignment accuracies estimated from the statistics of actual measurements in SACLA show the effectiveness of this commissioning scheme.

  3. The selection of radiation tolerant electrical/electronic components for gamma radiation environments in the nuclear power industry

    Garlick, D.R.

    1984-09-01

    This report briefly describes the mechanisms, units and effects of 1 MeV range gamma radiation on electrical/electronic components and materials. Information is tabulated on the gamma radiation tolerance of a wide range of components and materials. A radiation testing service, based at Harwell, is described. Lists of interested manufacturers and organisations are given. (author)

  4. Possibility of obtaining coherent short wave radiation from a solid state free electron laser

    Bogacz, S.A.; Ketterson, J.B.

    1986-03-01

    The idea of using a crystal lattice or a superlattice as an undulator for a free electron laser is explored. A purely classical treatment of relativistic positrons channeling through the proposed structure involving a self consistent solution of the wave equation for the radiating electromagnetic field and the kinetic equation for the positron distribution function leads to a positive gain coefficient for a forward radiating field. Matching the Kumakhov resonance to the undulator frequency further enhances the gain. This result, combined with a feedback mechanism arising from Bragg diffraction within the basic crystal lattice, leads to an instability of the radiation inside the crystal. Finally a numerical estimate of the Kumakhov-enhanced gain coefficient is made for the (110) planar channeling in a strain modulated Si superlattice. 8 refs., 4 figs

  5. Effects of radiation on MOS structures and silicon devices

    Braeunig, D.; Fahrner, W.

    1983-02-01

    A comprehensive view of radiation effects on MOS structures and silicon devices is given. In the introduction, the interaction of radiation with semiconductor material is presented. In the next section, the electrical degradation of semiconductor devices due to this interaction is discussed. The commonly used hardening techniques are shown. The last section deals with testing of radiation hardness of devices. (orig.) [de

  6. Correlation between auroral kilometric radiation and inverted v electron precipitation

    Green, J.L.; Gurnfti, D.A.; Hoffmans, R.A.

    1979-01-01

    Simultaneous observations of energetic electron precipitations and auroral kilometric radiation (AKR) were obtained from the polar orbiting satellites AE-D and Hawkeye. The Hawkeye observations were restricted to periods when the satellite was in the AKR emission cone in the northern hemisphere an at radial distances > or approx. =7 R/sub E/ to avoid local propagation cutoff effects. In addition, the AE-D measurements were restricted to complete passes across the auroral oval in the evening to midnight local time sector (from 20 to 01 hours magnetic local time). This is the local time region where the most intense bursts of AKR are believed to originate. A qualitative survey of AKR and electron precipitation than with plasma sheet precipitation. Quantitatively, a good correlation is found between the AKR intensity and the peak energy of inverted V events. In addition, in the tail of the most field-aligned portion (approx.O 0 pitch angle) of the distribution functions of the inverted V events,systematic changes are indicated as the associated AKR intensity increases. When the AKR power flux is weak ( -17 W/(m 2 Hz)). From a determination of the simultaneous power in the inverted V events and the AKR bursts, the efficiency of converting the charge particle energy into EM radiation increases to a maximum of about 1% for the most intense AKR bursts. However, conversion efficiencies as low as 10 -5 % are also found. There is some evidence which suggests that the tail temperature, T in F (V) of the inverted V events, may play an important role in the efficient generation or amplification of auroral kilometric radiation

  7. Cherenkov Radiation from a Pseudospark-sourced Electron Beam

    Phelps, A.D.R.; Yin, H.; Cross, A.W.; He, W.; Ronald, K.

    2003-01-01

    Electron beam generation from a multi-gap pseudospark discharge was investigated. A pseudospark-sourced electron beam has two phases, an initial hollow cathode phase (HCP) beam followed by a conductive phase (CP) beam. The beam brightness was measured by a field-free collimator to be 109 and 1011 Am-2rad-2 for the hollow cathode phase (HCP) beam and the conductive phase (CP) beam respectively. The initial HCP beam from an eight-gap pseudospark discharge was applied in a Cherenkov interaction between the electron beam and the TM01 mode of a 60-cm long alumina-lined waveguide. It was found experimentally that significant microwave radiation was generated only when the dielectric was present in the interaction space. If there was no dielectric in the cylindrical waveguide, then a very small background microwave output was detected even when the guide B-field was absent. This demonstrated, in conjunction with the observation that the microwave output signal was independent of the guide magnetic field over the range 0.13 to 0.26 T, that the radiation from the experiment was due to the Cherenkov interaction mechanism. In addition, two components of the microwave pulse were observed corresponding to the two energy components of the electron beam during the pseudospark discharge breakdown. These results demonstrated that the microwave radiation was generated by Cherenkov amplification of the broadband emission from the pseudospark discharge itself. A background signal level of around 100 W was measured in the frequency range 20 - 50 GHz with a percentage of (2.7 ± 0.6)% in the frequency range 25.5 - 28.6 GHz, when the dielectric lining was removed from the maser. The frequency of the microwave output after the Cherenkov maser interaction was measured to be mainly around 25.5 GHz and the dominating mode was identified as being TM01. The duration of the microwave pulse was approximately 80 ns, with a peak power of around 2 ± 0.2 kW. The gain of this amplifier was measured

  8. Electron-spin-resonance study of radiation-induced paramagnetic defects in oxides grown on (100) silicon substrates

    Kim, Y.Y.; Lenahan, P.M.

    1988-01-01

    We have used electron-spin resonance to investigate radiation-induced point defects in Si/SiO 2 structures with (100) silicon substrates. We find that the radiation-induced point defects are quite similar to defects generated in Si/SiO 2 structures grown on (111) silicon substrates. In both cases, an oxygen-deficient silicon center, the E' defect, appears to be responsible for trapped positive charge. In both cases trivalent silicon (P/sub b/ centers) defects are primarily responsible for radiation-induced interface states. In earlier electron-spin-resonance studies of unirradiated (100) substrate capacitors two types of P/sub b/ centers were observed; in oxides prepared in three different ways only one of these centers, the P/sub b/ 0 defect, is generated in large numbers by ionizing radiation

  9. Electronic structure of semiconductor quantum films

    Zhang, S.B.; Yeh, C.; Zunger, A.

    1993-01-01

    The electronic structure of thin (≤30 A) free-standing ideal films of Si(001), Si(110), and GaAs(110) is calculated using a plane-wave pseudopotential description. Unlike the expectation based on the simple effective-mass model, we find the following. (i) The band gaps of (001) quantum films exhibit even-odd oscillation as a function of the number N of monolayers. (ii) In addition to sine-type envelope functions which vanish at the film boundaries, some states have cosine envelope functions with extrema at boundaries. (iii) Even-layer Si(001) films exhibit at the valence-band maximum a state whose energy does not vary with the film thickness. Such zero confinement states have constant envelope throughout the film. (iv) Optical transitions in films exhibit boundary-imposed selection rules. Furthermore, oscillator strengths for pseudodirect transitions in the vicinity of forbidden direct transitions can be enhanced by several orders of magnitude. These findings, obtained in direct supercell calculations, can be explained in terms of a truncated crystal (TC) analysis. In this approach the film's wave functions are expanded in terms of pairs of bulk wave functions exhibiting a destructive interference at the boundaries. This maps the eigenvalue spectra of a film onto the bulk band structure evaluated at special k points which satisfy the boundary conditions. We find that the TC representation reproduces accurately the above-mentioned results of direct diagonalization of the film's Hamiltonian. This provides a simple alternative to the effective-mass model and relates the properties of quantum structures to those of the bulk material

  10. Structural enzymology using X-ray free electron lasers

    Christopher Kupitz

    2017-07-01

    Full Text Available Mix-and-inject serial crystallography (MISC is a technique designed to image enzyme catalyzed reactions in which small protein crystals are mixed with a substrate just prior to being probed by an X-ray pulse. This approach offers several advantages over flow cell studies. It provides (i room temperature structures at near atomic resolution, (ii time resolution ranging from microseconds to seconds, and (iii convenient reaction initiation. It outruns radiation damage by using femtosecond X-ray pulses allowing damage and chemistry to be separated. Here, we demonstrate that MISC is feasible at an X-ray free electron laser by studying the reaction of M. tuberculosis ß-lactamase microcrystals with ceftriaxone antibiotic solution. Electron density maps of the apo-ß-lactamase and of the ceftriaxone bound form were obtained at 2.8 Å and 2.4 Å resolution, respectively. These results pave the way to study cyclic and non-cyclic reactions and represent a new field of time-resolved structural dynamics for numerous substrate-triggered biological reactions.

  11. Study on regeneration of activated carbon by means of electron radiation

    Zhu Guanghua; Arai, H.; Hosono, M.

    1991-01-01

    The results of regeneration of activated carbon adsorbing sodium lauryl sulfate (SLS) by 2 MeV electron radiation, and the dependence of the regeneration rate of activated carbon on the electron current intensity, the temperature of sample and the atmosphere were reported. It is shown that regeneration of activated carbon by electron radiation is full of promise

  12. Electron microscopy study of radiation effects in boron carbide

    Stoto, T.

    1987-03-01

    Boron carbide is a disordered non-stoechiometric material with a strongly microtwinned polycristallyne microstructure. This ceramic is among the candidate materials for the first wall coating in fusion reactor and is used as a neutron absorber in the control rods of fast breeder reactors. The present work deals with the nature of radiation damage in this solid. Because of helium internal production, neutron irradiated boron carbide is affected by swelling and by a strong microcracking which can break up a pellet in fine powder. These processes are rather intensitive to the irradiation parameters (temperature, flux and even neutron spectrum). Transmission electron microscopy of samples irradiated by the fast neutrons of a reactor, the electrons of a high voltage electron microscope and of samples implanted with helium ions was used to understand the respective roles of helium and point defects in the processes of swelling and microcracking. The design of an irradiation chamber for helium implantation at controlled temperature from 600 to 1700 0 C was an important technical part of this work [fr

  13. Radiation safety of gamma and electron irradiation facilities

    1992-01-01

    There are currently some 160 gamma irradiation facilities and over 600 electron beam facilities in operation throughout virtually all Member States of the IAEA. The most widespread uses of these facilities are for the sterilization of medical and pharmaceutical products, the preservation of foodstuffs, polymer synthesis and modification, and the eradication of insect infestation. The safety record of this industry has been very good. Nevertheless, there is a potential for accidents with serious consequences. Gamma and electron beam facilities produce very high dose rates during irradiation, so that a person accidentally present in the irradiation chamber can receive a lethal dose within minutes or seconds. Precautions against uncontrolled entry must therefore be taken. Furthermore, gamma irradiation facilities contain large amounts of radioactivity and if the mechanism for retracting the source is damaged, the source may remain exposed, inhibiting direct access to carry out remedial work. Contamination can result from corroded or damaged sources, and decontamination can be very expensive. These aspects clearly indicate the need to achieve a high degree of safety and reliability in the facilities. This can be accomplished by effective quality control together with careful design, manufacture, installation, operation and decommissioning. The guidance in this Safety Series publication is intended for competent authorities responsible for regulating the use of radiation sources as well as the manufacturers, suppliers, installers and users of gamma and electron beam facilities. 20 refs, 6 figs

  14. Estimation of edge electron temperature profiles via forward modelling of the electron cyclotron radiation transport at ASDEX Upgrade

    Rathgeber, S K; Barrera, L; Eich, T; Fischer, R; Suttrop, W; Wolfrum, E; Nold, B; Willensdorfer, M

    2013-01-01

    We present a method to obtain reliable edge profiles of the electron temperature by forward modelling of the electron cyclotron radiation transport. While for the core of ASDEX Upgrade plasmas, straightforward analysis of electron cyclotron intensity measurements based on the optically thick plasma approximation is usually justified, reasonable analysis of the steep and optically thin plasma edge needs to consider broadened emission and absorption profiles and radiation transport processes. This is carried out in the framework of integrated data analysis which applies Bayesian probability theory for joint analysis of the electron density and temperature with data of different interdependent and complementary diagnostics. By this means, electron cyclotron radiation intensity delivers highly spatially resolved electron temperature data for the plasma edge. In H-mode, the edge gradient of the electron temperature can be several times higher than the one of the radiation temperature. Furthermore, we are able to reproduce the ‘shine-through’ peak—the observation of increased radiation temperatures at frequencies resonant in the optically thin scrape-off layer. This phenomenon is caused by strongly down-shifted radiation of Maxwellian tail electrons located in the H-mode edge region and, therefore, contains valuable information about the electron temperature edge gradient. (paper)

  15. Application of the Electron paramagnetic resonance to the ionizing radiation dosimetry

    Urena N, F.

    2000-01-01

    The Electron Paramagnetic Resonance (EPR) is defined as the resonant absorption of electromagnetic energy in paramagnetic substances by the spin transition of a non-pairing electron between different energy levels in presence of a magnetic field. (Slighter, 1989). One of the more important characteristic of EPR is that the electron spin levels are subdivided by the electron interaction with the magnetic dipoles of the nearby nucleus giving occasion for a spectral structure called hyperfine structure. In this kind of interactions two limit cases are distinguished: 1. when the non-pairing electron is located in a central ion surrounded of atoms belonging to coordinate molecules. 2. When a non-pairing electron interactioning in the same form with a number of equivalent nucleus, which is common in organic radicals, these will give as result spectra. Some EPR spectrometer can be used to dosimetric purposes by free radicals via. In this work, it is presented the application of EPR to dosimetry of ionizing radiations by free radicals via which allows to determinations of high doses. (Author)

  16. Multi-Point Measurements to Characterize Radiation Belt Electron Precipitation Loss

    Blum, L. W.

    2017-12-01

    Multipoint measurements in the inner magnetosphere allow the spatial and temporal evolution of various particle populations and wave modes to be disentangled. To better characterize and quantify radiation belt precipitation loss, we utilize multi-point measurements both to study precipitating electrons directly as well as the potential drivers of this loss process. Magnetically conjugate CubeSat and balloon measurements are combined to estimate of the temporal and spatial characteristics of dusk-side precipitation features and quantify loss due to these events. To then understand the drivers of precipitation events, and what determines their spatial structure, we utilize measurements from the dual Van Allen Probes to estimate spatial and temporal scales of various wave modes in the inner magnetosphere, and compare these to precipitation characteristics. The structure, timing, and spatial extent of waves are compared to those of MeV electron precipitation during a few individual events to determine when and where EMIC waves cause radiation belt electron precipitation. Magnetically conjugate measurements provide observational support of the theoretical picture of duskside interaction of EMIC waves and MeV electrons leading to radiation belt loss. Finally, understanding the drivers controlling the spatial scales of wave activity in the inner magnetosphere is critical for uncovering the underlying physics behind the wave generation as well as for better predicting where and when waves will be present. Again using multipoint measurements from the Van Allen Probes, we estimate the spatial and temporal extents and evolution of plasma structures and their gradients in the inner magnetosphere, to better understand the drivers of magnetospheric wave characteristic scales. In particular, we focus on EMIC waves and the plasma parameters important for their growth, namely cold plasma density and cool and warm ion density, anisotropy, and composition.

  17. Studies in the electronic structure of matter

    Swarts, C.A.

    1979-01-01

    Chapter I: Here the results of various theories for the angular distribution of electrons photoemitted from the outermost p-shell of rare gas atoms are compared. The theories compared are (I) the local density theories of Slater (X/sub α/) and of Hohenberg, Kohn and Sham, (II) the pseudopotential method, (III) Hartree-Fock theory as evaluated by Kennedy and Manson, and (IV) Amusia's Random Phase Approximation with Exchange (RPAE). It is shown that the local density theories, although simple, generally fail to produce reliable cross section; the more complicated Hartree-Fock method is no more reliable; the a priori RPAE method is most reliable, but tedious; and the phenomenological pseudopotential method offers a good combination of reliability and simplicity. The muffin-tin approximation, widely used in molecular and condensed matter physics, is examined and found to be adequate. Chapter II: Extended Hueckel theory is applied to GaAs, GaP and to the nitrogen isoelectronic trap in GaAs and GaP. The computed perfect crystal band structures are found to be in reasonable agreement with those computed with empirical pseudopotentials. Nitrogen impurity levels in GaAs and GaP are calculated using a cluster model. Chapter III: By means of model calculations for an independent electron metal, we obtain exact lineshapes for the photon absorption, emission and photoemission spectra of deep core states. We find in each case an X-ray edge anomaly as pedicted by Nozieres and De Dominicis. Sumrules are used as a general check on the calculations and to explain the deviations of the exact theory from the exciton theory away from threshold

  18. Nonlinearity in structural and electronic materials

    Bishop, A.R.; Beardmore, K.M.; Ben-Naim, E.

    1997-01-01

    This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The project strengthens a nonlinear technology base relevant to a variety of problems arising in condensed matter and materials science, and applies this technology to those problems. In this way the controlled synthesis of, and experiments on, novel electronic and structural materials provide an important focus for nonlinear science, while nonlinear techniques help advance the understanding of the scientific principles underlying the control of microstructure and dynamics in complex materials. This research is primarily focused on four topics: (1) materials microstructure: growth and evolution, and porous media; (2) textures in elastic/martensitic materials; (3) electro- and photo-active polymers; and (4) ultrafast photophysics in complex electronic materials. Accomplishments included the following: organization of a ''Nonlinear Materials'' seminar series and international conferences including ''Fracture, Friction and Deformation,'' ''Nonequilibrium Phase Transitions,'' and ''Landscape Paradigms in Physics and Biology''; invited talks at international conference on ''Synthetic Metals,'' ''Quantum Phase Transitions,'' ''1996 CECAM Euroconference,'' and the 1995 Fall Meeting of the Materials Research Society; large-scale simulations and microscopic modeling of nonlinear coherent energy storage at crack tips and sliding interfaces; large-scale simulation and microscopic elasticity theory for precursor microstructure and dynamics at solid-solid diffusionless phase transformations; large-scale simulation of self-assembling organic thin films on inorganic substrates; analysis and simulation of smoothing of rough atomic surfaces; and modeling and analysis of flux pattern formation in equilibrium and nonequilibrium Josephson junction arrays and layered superconductors

  19. A non-destructive electron beam diagnostic for a SASE FEL using coherent off-axis undulator radiation

    Neuman, C P; Barnett, G A; Madey, J M J; O'Shea, P G

    1999-01-01

    We show that by observing coherent off-axis undulator radiation (COUR) from a short diagnostic wiggler, it may be possible to determine the length and structure of a short electron bunch. Typically the on-axis undulator radiation is incoherent, but at angles of a few degrees, the wavelength of the emitted radiation may be comparable to the length of a short electron bunch, and thus coherence effects emerge. Due to such coherence effects, the intensity of the emitted radiation may change by up to a factor of 10 sup 9 as the angle of observation is increased. The radiation becomes coherent in a way which depends on the length and structure of the electron bunch. Observing COUR disturbs the electron bunch negligibly. Thus, COUR can be used as a non-destructive diagnostic which would allow for optimization of FEL performance while an FEL is operating. Such a diagnostic could be used for proposed SASE FELs, which use short electron bunches. We present two methods to describe the theory for COUR, and we use these m...

  20. A non-destructive electron beam diagnostic for a SASE FEL using coherent off-axis undulator radiation

    Neuman, C.P.; Ponds, M.L.; Barnett, G.A.; Madey, J.M.J.; O'Shea, P.G.

    1999-01-01

    We show that by observing coherent off-axis undulator radiation (COUR) from a short diagnostic wiggler, it may be possible to determine the length and structure of a short electron bunch. Typically the on-axis undulator radiation is incoherent, but at angles of a few degrees, the wavelength of the emitted radiation may be comparable to the length of a short electron bunch, and thus coherence effects emerge. Due to such coherence effects, the intensity of the emitted radiation may change by up to a factor of 10 9 as the angle of observation is increased. The radiation becomes coherent in a way which depends on the length and structure of the electron bunch. Observing COUR disturbs the electron bunch negligibly. Thus, COUR can be used as a non-destructive diagnostic which would allow for optimization of FEL performance while an FEL is operating. Such a diagnostic could be used for proposed SASE FELs, which use short electron bunches. We present two methods to describe the theory for COUR, and we use these methods to calculate the expected outcome of a COUR experiment. We propose an experiment to demonstrate COUR effects and their applications to SASE FELs

  1. Brightness and coherence of synchrotron radiation and high-gain free electron lasers

    Kim, K.J.

    1986-10-01

    The characteristics of synchrotron radiation are reviewed with particular attention to its phase-space properties and coherence. The transition of the simple undulator radiation to more intense, more coherent high-gain free electron lasers, is discussed

  2. Electronic structure of the 3d metals. An investigation by L-shell-photoionisation

    Richter, T.S.

    2007-12-03

    The 3d transition metal elements from Sc to Cu have been investigated by both photo electron emission and photo absorption. Experimental spectra in the 2p energy range are discussed based on atomic multiplet models and Hartree- Fock calculations. The samples have been evaporated from an electron bombardment crucible and excited/ionized by monochromatized synchrotron radiation. Fundamental effects and the main interactions which govern the electronic structure of the 3d metal atoms are covered. Common spectral features and trends in the series are discussed as well as the importance of many body electron correlation effects. (orig.)

  3. Resonant influence of a longitudinal hypersonic field on the radiation from channeled electrons

    Grigoryan, L.Sh.; Mkrtchyan, A.R.; Mkrtchyan, A.H.; Khachatryan, H.F.; Prade, H.; Wagner, W.; Piestrup, M.A.

    2001-01-01

    The wave function of a planar/axially channeled electron with energy 10 MeV≤E<<1 GeV under the influence of a longitudinal hypersonic wave excited in a single crystal is calculated. Conditions for the resonant influence of the hypersonic wave on the quantum state of the channeled electron are deduced. Expressions for the wave function that are applicable in the case of resonance are obtained. Angular and spectral distributions of the radiation intensity from the planar/axially channeled electron are also calculated. The possibility of significant amplification of channeling radiation by a hypersonic wave is substantiated. It is found that the hypersound can excite inverse radiative transitions through which the transversal energy of the channeled electron is increased. These transitions have a resonant nature and can lead to a considerable intensification of the electron channeling radiation. In the case of axial channeling, the resonance radiation is sustained also by direct radiative transitions of the electron

  4. Reliability of high power electron accelerators for radiation processing

    Zimek, Z.

    2011-01-01

    Accelerators applied for radiation processing are installed in industrial facilities where accelerator availability coefficient should be at the level of 95% to fulfill requirements according to industry standards. Usually the exploitation of electron accelerator reviles the number of short and few long lasting failures. Some technical shortages can be overcome by practical implementation the experience gained in accelerator technology development by different accelerator manufactures. The reliability/availability of high power accelerators for application in flue gas treatment process must be dramatically improved to meet industrial standards. Support of accelerator technology dedicated for environment protection should be provided by governmental and international institutions to overcome accelerator reliability/availability problem and high risk and low direct profit in this particular application. (author)

  5. Low-temperature radiative recombination of electrons with bare nuclei

    Omidvar, K.

    1993-01-01

    Aside from empirical formulas, the radiative-recombination cross section and coefficient are usually given in tabulated forms instead of analytic formulas. Here, we give analytic expressions in the form of expansions for the recombination cross section as a function of the electron energy E for low E, and for the recombination coefficient as a function of the temperature T for low T. The expansion coefficients are combinations of confluent hypergeometric functions, and are tabulated for a large number of the final principal and angular-momentum quantum numbers n and l. It is shown that the recombination cross section for arbitrary nuclear charge number Z is independent of Z, while the recombination coefficient for T/Z 2 much-lt 1.58x10 5 K increases as Z 2 . Excellent agreement is found with the published tabulated values

  6. Reliability of high power electron accelerators for radiation processing

    Zimek, Z. [Department of Radiation Chemistry and Technology, Institute of Nuclear Chemistry and Technology, Warsaw (Poland)

    2011-07-01

    Accelerators applied for radiation processing are installed in industrial facilities where accelerator availability coefficient should be at the level of 95% to fulfill requirements according to industry standards. Usually the exploitation of electron accelerator reviles the number of short and few long lasting failures. Some technical shortages can be overcome by practical implementation the experience gained in accelerator technology development by different accelerator manufactures. The reliability/availability of high power accelerators for application in flue gas treatment process must be dramatically improved to meet industrial standards. Support of accelerator technology dedicated for environment protection should be provided by governmental and international institutions to overcome accelerator reliability/availability problem and high risk and low direct profit in this particular application. (author)

  7. Modeling of electron time variations in the radiation belts

    Chan, K.W.; Teague, M.J.; Schofield, N.J.; Vette, J.I.

    1979-01-01

    A review of the temporal variation in the trapped electron population of the inner and outer radiation zones is presented. Techniques presently used for modeling these zones are discussed and their deficiencies identified. An intermediate region is indicated between the zones in which the present modeling techniques are inadequate due to the magnitude and frequency of magnetic storms. Future trends are examined, and it is suggested that modeling of individual magnetic storms may be required in certain L bands. An analysis of seven magnetic storms is presented, establishing the independence of the depletion time of the storm flux and the storm magnitude. Provisional correlation between the storm magnitude and the Dst index is demonstrated

  8. Assembly for the measurement of the most probable energy of directed electron radiation

    Geske, G.

    1987-01-01

    This invention relates to a setup for the measurement of the most probable energy of directed electron radiation up to 50 MeV. The known energy-range relationship with regard to the absorption of electron radiation in matter is utilized by an absorber with two groups of interconnected radiation detectors embedded in it. The most probable electron beam energy is derived from the quotient of both groups' signals

  9. Theoretical study of ultrarelativistic laser-electron interaction with radiation reaction

    Seto K.

    2013-11-01

    Full Text Available When the laser intensity becomes higher than 1022  W/cm2, the motion of an electron becomes relativistic, and emits large amounts of radiation. This radiation energy loss transferred to the kinetic energy loss of the electron, is treated as an external force, the “radiation reaction force”. We show the new equation of motion including this radiation reaction and the simulation method, as well as results of single electron system or dual electrons system with Liénard-Wiechert field interaction.

  10. Electron accelerators for radiation processing: Criterions of selection and exploitation

    Zimek, Zbigniew

    2001-01-01

    The progress in accelerator technology is tightly attached to the continuously advanced development in many branches of technical activity. Although the present level of accelerators development can satisfy most of the commercial requirements, this field continues to expand and improve quality by offering efficient, cheap, reliable, high average beam power commercial units. Accelerator construction must be a compromised between size, efficiency and cost with respect to the field of its application. High power accelerators have been developed to meet specific demands of flue gas treatment and other high throughput to increase the capacity of the progress and reduced unit cost of operation. Automatic control, reliability and reduced maintenance, adequate adoption to process conditions, suitable electron energy and beam power are the basic features of modern accelerator construction. Accelerators have the potential to serve as industrial radiation sources and eventually may replace the isotope sources in future. Electron beam plants can transfer much higher amounts of energy into the irradiated objects than other types of facilities including gamma plants. This provides the opportunity to construct technological lines with high capacity that are more technically and economically suitable with high throughputs, short evidence time and grate versatility

  11. Monte Carlo based treatment planning for modulated electron beam radiation therapy

    Lee, Michael C. [Radiation Physics Division, Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA (United States)]. E-mail: mclee@reyes.stanford.edu; Deng Jun; Li Jinsheng; Jiang, Steve B.; Ma, C.-M. [Radiation Physics Division, Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA (United States)

    2001-08-01

    A Monte Carlo based treatment planning system for modulated electron radiation therapy (MERT) is presented. This new variation of intensity modulated radiation therapy (IMRT) utilizes an electron multileaf collimator (eMLC) to deliver non-uniform intensity maps at several electron energies. In this way, conformal dose distributions are delivered to irregular targets located a few centimetres below the surface while sparing deeper-lying normal anatomy. Planning for MERT begins with Monte Carlo generation of electron beamlets. Electrons are transported with proper in-air scattering and the dose is tallied in the phantom for each beamlet. An optimized beamlet plan may be calculated using inverse-planning methods. Step-and-shoot leaf sequences are generated for the intensity maps and dose distributions recalculated using Monte Carlo simulations. Here, scatter and leakage from the leaves are properly accounted for by transporting electrons through the eMLC geometry. The weights for the segments of the plan are re-optimized with the leaf positions fixed and bremsstrahlung leakage and electron scatter doses included. This optimization gives the final optimized plan. It is shown that a significant portion of the calculation time is spent transporting particles in the leaves. However, this is necessary since optimizing segment weights based on a model in which leaf transport is ignored results in an improperly optimized plan with overdosing of target and critical structures. A method of rapidly calculating the bremsstrahlung contribution is presented and shown to be an efficient solution to this problem. A homogeneous model target and a 2D breast plan are presented. The potential use of this tool in clinical planning is discussed. (author)

  12. Graph-based linear scaling electronic structure theory

    Niklasson, Anders M. N., E-mail: amn@lanl.gov; Negre, Christian F. A.; Cawkwell, Marc J.; Swart, Pieter J.; Germann, Timothy C.; Bock, Nicolas [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Mniszewski, Susan M.; Mohd-Yusof, Jamal; Wall, Michael E.; Djidjev, Hristo [Computer, Computational, and Statistical Sciences Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Rubensson, Emanuel H. [Division of Scientific Computing, Department of Information Technology, Uppsala University, Box 337, SE-751 05 Uppsala (Sweden)

    2016-06-21

    We show how graph theory can be combined with quantum theory to calculate the electronic structure of large complex systems. The graph formalism is general and applicable to a broad range of electronic structure methods and materials, including challenging systems such as biomolecules. The methodology combines well-controlled accuracy, low computational cost, and natural low-communication parallelism. This combination addresses substantial shortcomings of linear scaling electronic structure theory, in particular with respect to quantum-based molecular dynamics simulations.

  13. Radiation levels at CERN's injectors and their impact on electronic equipment

    AUTHOR|(SzGeCERN)649218; Brugger, Markus

    2013-01-01

    Electronic devices operating in hostile radiation environments, such as those found close to high-energy particle accelerators, can suffer from different types of radiation induced failures. At CERN, the mixed particle and energy radiation fields present at the Large Hadron Collider (LHC) and its injector chain can give rise to both stochastic and cumulative effects causing radiation induced failures of exposed electronics and materials, thus directly impacting components and system lifetimes, as well as maintenance requirements. With its original focus on the LHC, the Radiation to Electronics (R2E) project has been successfully implementing mitigation actions in order to avoid accelerator downtime due to radiation induced failures on active electronics. In a next step, the emphasis is put on CERN's injector chain, collecting the respective available information about radiation levels, the definition of additional monitoring requirements and a critical analysis of present and future equipment installations. T...

  14. Electronic structure and chemical properties of superheavy elements

    Pershina, V [Gesellschaft fuer Schwerionenforschung (GSI), Helmholtzzentrum fuer Schwerionenforschung Gmbh (Germany)

    2009-12-31

    Relativistic electronic structure calculations of superheavy elements (Z>=104) are analyzed. Preference is given to those related to experimental research. The role of relativistic effects is discussed.

  15. Electronic structure characterization and bandgap engineeringofsolar hydrogen materials

    Guo, Jinghua

    2007-11-01

    Bandgap, band edge positions as well as the overall band structure of semiconductors are of crucial importance in photoelectrochemical and photocatalytic applications. The energy position of the band edge level can be controlled by the electronegativity of the dopants, the pH of the solution (flatband potential variation of 60 mV per pH unit), as well as by quantum confinement effects. Accordingly, band edges and bandgap can be tailored to achieve specific electronic, optical or photocatalytic properties. Synchrotron radiation with photon energy at or below 1 keV is giving new insight into such areas as condensed matter physics and extreme ultraviolet optics technology. In the soft x-ray region, the question tends to be, what are the electrons doing as they migrated between the atoms. In this paper, I will present a number of soft x-ray spectroscopic study of nanostructured 3d metal compounds Fe{sub 2}O{sub 3} and ZnO.

  16. Radiation performance of AlGaAs concentrator cells and expected performance of cascade structures

    Curtis, H.B.; Swartz, C.K.; Hart, R.E. Jr.

    1987-01-01

    Aluminum gallium arsenide, GaAs, silicon and InGaAs cells have been irradiated with 1 MeV electrons and 37 MeV protons. These cells are candidates for individual cells in a cascade structure. Data is presented for both electron and proton irradiation studies for one sun and a concentration level of 100X AMO. Results of calculations on the radiation resistance of cascade cell structures based on the individual cell data are also presented. Both series connected and separately connected structures are investigated

  17. Structure of a radiate pseudocolony associated with an intrauterine contraceptive device

    O'Brien, P.K.; Lea, P.J.; Roth-Moyo, L.A.

    1985-01-01

    Transmission electron microscopy of a radiate pseudocolony associated with an intrauterine contraceptive device (IUCD) showed central bundles of extracellular fibers averaging 35 nm in diameter, surrounded by layered mantles of electron-dense, amorphous granular material. No bacterial, viral, or fungal structures were present. X-ray microanalysis revealed copper, sulfur, chloride, iron, and phosphorus; no calcium was found. It is postulated that these structures and histologically identical non-IUCD-associated granules from the female genital tract, as well as similar structures from other body locations, including those reported in colloid cysts of the third ventricle, are of lipofuscin origin

  18. Thermal Radiation for Structural Fire Safety Design

    Hertz, Kristian Dahl

    2006-01-01

    The lecture notes give a short introduction of the theory of thermal radiation. The most elementary concepts and methods are presented in order to give a fundamental knowledge for calculation of the load bearing capacities of fire exposed building constructions....

  19. Superconductive tunnel structures as radiation detectors

    Barone, A.; Gray, K.E.

    1985-08-01

    A brief review is given on various aspects of the potential of superconducting tunnel junctions as detectors for atomic and nuclear radiations. On the basis of recent results main advantages and drawbacks are indicated providing a preliminary comparison with the presently used semiconductor detectors. The basic ideas underlying the physics of the interaction of nuclear particles and other radiations with superconducting junctions are outlined. 9 refs., 1 tab

  20. Radiation leakage dose from Elekta electron collimation system.

    Pitcher, Garrett M; Hogstrom, Kenneth R; Carver, Robert L

    2016-09-08

    This study provided baseline data required for a greater project, whose objective was to design a new Elekta electron collimation system having significantly lighter electron applicators with equally low out-of field leakage dose. Specifically, off-axis dose profiles for the electron collimation system of our uniquely configured Elekta Infinity accelerator with the MLCi2 treatment head were measured and calculated for two primary purposes: 1) to evaluate and document the out-of-field leakage dose in the patient plane and 2) to validate the dose distributions calculated using a BEAMnrc Monte Carlo (MC) model for out-of-field dose profiles. Off-axis dose profiles were measured in a water phantom at 100 cm SSD for 1 and 2 cm depths along the in-plane, cross-plane, and both diagonal axes using a cylindrical ionization chamber with the 10 × 10 and 20 × 20 cm2 applicators and 7, 13, and 20 MeV beams. Dose distributions were calculated using a previously developed BEAMnrc MC model of the Elekta Infinity accelerator for the same beam energies and applicator sizes and compared with measurements. Measured results showed that the in-field beam flatness met our acceptance criteria (± 3% on major and ±4% on diagonal axes) and that out-of-field mean and maximum percent leakage doses in the patient plane met acceptance criteria as specified by the International Electrotechnical Commission (IEC). Cross-plane out-of-field dose profiles showed greater leakage dose than in-plane profiles, attributed to the curved edges of the upper X-ray jaws and multileaf collimator. Mean leakage doses increased with beam energy, being 0.93% and 0.85% of maximum central axis dose for the 10 × 10 and 20 × 20 cm2 applicators, respectively, at 20 MeV. MC calculations predicted the measured dose to within 0.1% in most profiles outside the radiation field; however, excluding model-ing of nontrimmer applicator components led to calculations exceeding measured data by as much as 0.2% for some regions

  1. Effect of relativistic electron radiation on Se Zn monocrystal microembrittlement

    Mazilov, A.V.; Stratienko, V.A.; Migal', V.P.; Lugovskaya, E.I.

    2002-01-01

    The influence of 60 MeV electron irradiation (fluences between 10 9 and 10 16 el/sm 2 ) on the mikrobrittleness of n-type sphalerite-structure zinc selenide has been investigated.It was found that irradiation caused the crack lengths to increase under constant load.In the fluence range of 10 9 to 10 13 el/sm 2 , an increase was observed in the critical load, at which cracks were formed. It is shown that the mechanical properties of zinc selenide are dominantly influenced by the defect clusters, for the formation of which an energy over 400 eV is needed

  2. Device for the radiation centering at electron emitters

    Panzer, S.; Ardenne, T. von; Jessat, K.; Bahr, G.

    1985-01-01

    The invention has been directed at a device for a simplified and reliable centering of electron beams at electron emitters in particular for welding and thermal surface modifications. The electron beam has been focussed relatively to an electron-optical lens. A movable masked electron detector has been arranged at the electron beam deflection plane. The electron detector is connected with an electronic data evaluation equipment

  3. Synchrotron radiation: a new perspectives for structure examinations

    Kadyrzhanov, K.K.; Kozhakhmetov, S.K.; Turkebaev, T.Eh.

    2001-01-01

    An important task of radiation material testing is manufacture of multifunctional, stable and cheap materials with designed properties. A materials successful operation in an extemal conditions (high temperatures and pressures, high radiation fluences and charged particles, and etc.) imply an joint decision of physical, chemical, mechanical and other problems. The decision of these problems includes at least examination for structural, phase content, oxidation stability, thermal stability, mechanical strength, thin-film-coverings controlled synthesis (both the passivating and the catalytic) compatible with main matrix, and etc. Synchrotron radiation sources application for these problems are highly perspective. Solution of a set of problems on structural examinations for a materials exposed to high radiation fluences and operating in extemal condition is planning with use of the DELSY third generation synchrotron radiation source constructing at the Joint Institute for Nuclear Research (Dubna). In the paper the principal parameters of the DELSY synchrotron radiation source are given

  4. Electronic structure studies of La2CuO4

    Wachs, A. L.; Turchi, P. E. A.; Jean, Y. C.; Wetzler, K. H.; Howell, R. H.; Fluss, M. J.; Harshman, D. R.; Remeika, J. P.; Cooper, A. S.; Fleming, R. M.

    1988-07-01

    We report results of positron-electron momentum-distribution measurements of single-crystal La2CuO4 using two-dimensional angular correlation of positron-annihilation-radiation techniques. The data contain two components: a large (~85%), isotropic corelike electron contribution and a remaining, anisotropic valence-electron contribution modeled using a linear combination of atomic orbitals-molecular orbital method and a localized ion scheme, within the independent-particle model approximation. This work suggests a ligand-field Hamiltonian to be justified for describing the electronic properties of perovskite materials.

  5. Electronic structure studies of La2CuO4

    Wachs, A.L.; Turchi, P.E.A.; Jean, Y.C.

    1988-01-01

    We report results of positron-electron momentum-distribution measurements of single-crystal La 2 CuO 4 using two-dimensional angular correlation of positron-annihilation-radiation techniques. The data contain two components: a large (∼85%), isotropic corelike electron contribution and a remaining, anisotropic valence-electron contribution modeled using a linear combination of atomic orbitals--molecular orbital method and a localized ion scheme, within the independent-particle model approximation. This work suggests a ligand-field Hamiltonian to be justified for describing the electronic properties of perovskite materials

  6. Electronic structure of shandite Co3Sn2S2

    Dedkov, Y. S.; Holder, M.; Molodtsov, S. L.; Rosner, H.

    2008-03-01

    The electronic structure of shandite Co3Sn2S2 was determined by photoelectron spectroscopy and compared with ab initio band structure calculations. Presented results give evidence that this compound has half-metallic ferromagnetic properties.

  7. Process for hardening an alkyd resin composition using ionizing radiation. [electron beams, gamma radiation

    Watanabe, T; Murata, K; Maruyama, T

    1969-11-27

    In an alkyd resin composition having free hydroxide radicals and containing a conjugated unsaturated fatty acid and/or oil as a component thereof, a process for hardening an alkyd resin composition comprises the steps of dissolving into a vinyl monomer, the product obtained by the semi-esterification reaction of said hydroxide radicals with acid anhydrides having polymerizable radicals and hardening by ionizing radiation to provide a coating with a high degree of cross-linking, with favorable properties such as toughness, hardness, chemical resistance and resistance to weather and with the feasibility of being applied as the ground and finish coat on metals, wood, paper, outdoor construction or the like. Any kind of ionization radiation, particularly accelerated electron beams, ..gamma.. radiation can be used at 50/sup 0/C to -5/sup 0/C for a few seconds or minutes, permitting continuous operation. In one example, 384 parts of phthalic anhydride, 115 parts of pentaerythritol, 233 parts of trimethylol ethane, 288 parts of tung fatty acid and 49 parts of para-tertiary-butyl benzoic acid are mixed and heated with 60 parts of xylene to an acid value of 12. In addition, 271 parts of maleic anhydride and 0.6 parts of hydroquinone are admixed with the content and heated to terminate the reaction. 100 parts of a 50% stylene solution of this alkyd resin are mixed with 1 part of a 60% toluene solution of cobalt naphthenate, and then coated on a glass plate and irradiated with high energy electron beams of 300 kV with a dose of 5 Mrad for 1 sec.

  8. Electronic conductance of quantum wire with serial periodic potential structures

    Fayad, Hisham M.; Shabat, Mohammed M.; Abdus Salam International Centre for Theoretical Physics, Trieste

    2000-08-01

    A theory based on the total transfer matrix is presented to investigate the electronic conductance in a quantum wire with serial periodic potentials. We apply the formalism in computation of the electronic conductance in a wire with different physical parameters of the wire structure. The numerical results could be used in designing some future quantum electronic devices. (author)

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

    Tallentire, Alan; 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 with a previously published value.

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

    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...... with a previously published value....

  11. Coherent radiation from high-current electron beams of linear accelerators and its applications

    Okuda, Shuichi; Takanaka, Makoto; Nakamura, Mitsumi; Kato, Ryukou; Takahashi, Toshiharu; Nam, Soon-Kwon; Taniguchi, Ryouichi; Kojima, Takao

    2006-01-01

    The characteristics of the far-infrared light source using the coherent radiation emitted from a high-energy short electron bunch have been investigated. The coherent radiation has a continuous spectrum in a submillimeter to millimeter wavelength range and the brightness is relatively high. The spectrum of the radiation is determined by the longitudinal form factor of the electron bunch. The operational conditions of a high-current linear accelerator have been optimized using an electron bunch shape monitor. The coherent transition radiation light source has been applied to absorption spectroscopy for liquid water and to an imaging experiment for a leaf of rose

  12. Study of cell cycle and apoptosis after radiation with electron linear accelerator injury

    Xu Lan; Zhou Yinghui; Shi Ning; Peng Miao; Wu Shiliang

    2002-01-01

    Purpose: To determine the cell cycle and apoptosis of the injured cells after radiation with the electron linear accelerator. Methods: NIH 3T3 cells were irradiated by the radiation with the electron linear accelerator. In the experiment the condition of the cell cycle and apoptosis of the injured cells were measured. The expression of p53 was also tested. Results: After exposure to radiation, the number of apoptotic cells as well as the expression of p53 increased. Conclusion: The electron linear accelerator radiation injury can induce cell apoptosis

  13. Electronic structure of nitride-based quantum dots

    Winkelnkemper, Momme

    2008-11-07

    In the present work the electronic and optical properties of In{sub x}Ga{sub 1-x}N/GaN and GaN/AlN QDs are studied by means of eight-band k.p theory. Experimental results are interpreted in detail using the theoretical results. The k.p model for the QD electronicstructure calculations accounts for strain, piezo- and pyroelectric effects, spin-orbit and crystal-field splitting, and is implemented for arbitrarily shaped QDs on a finite differences grid. Few-particle corrections are included using the self-consistent Hartree method. Band parameters for the wurtzite and zinc-blende phases of GaN, AlN, and InN are derived from first-principle G{sub 0}W{sub 0} band-structure calculations. Reliable values are also provided for parameters that have not been determined experimentally yet. The electronic properties of nitride QDs are dominated by the large built-in piezo- and pyroelectric fields, which lead to a pronounced red-shift of excitonic transition energies and extremely long radiative lifetimes in large GaN/AlN QDs. In In{sub x}Ga{sub 1-x}N/GaN QDs these fields induce a pronounced dependence of the radiative excitonic lifetimes on the exact QD shape and composition. It is demonstrated that the resulting variations of the radiative lifetimes in an inhomogeneous QD ensemble are the origin of the multi-exponential luminescence decay frequently observed in time-resolved ensemble measurements on In{sub x}Ga{sub 1-x}N/GaN QDs. A polarization mechanism in nitride QDs based on strain-induced valence-band mixing effects is discovered. Due to the valence-band structure of wurtzite group-III nitrides and the specific strain situation in c-plane QDs, the confined hole states are formed predominantly by the two highest valence bands. In particular, the hole ground state (h{sub 0} {identical_to} h{sub A}) is formed by the A band, and the first excited hole state (h{sub 1} {identical_to} h{sub B}) by the B band. It is shown that the interband transitions involving h{sub A} or h

  14. Radiation belt seed population and its association with the relativistic electron dynamics: A statistical study: Radiation Belt Seed Population

    Tang, C. L.; Wang, Y. X.; Ni, B.; Zhang, J.-C.

    2017-01-01

    Using the Van Allen Probes data, we study the radiation belt seed population and it associated with the relativistic electron dynamics during 74 geomagnetic storm events. Based on the flux changes of 1 MeV electrons before and after the storm peak, these storm events are divided into two groups of “non-preconditioned” and “preconditioned”. The statistical study shows that the storm intensity is of significant importance for the distribution of the seed population (336 keV electrons) in the outer radiation belt. However, substorm intensity can also be important to the evolution of the seed population for some geomagnetic storm events. For non-preconditioned storm events, the correlation between the peak fluxes and their L-shell locations of the seed population and relativistic electrons (592 keV, 1.0 MeV, 1.8 MeV, and 2.1 MeV) is consistent with the energy-dependent dynamic processes in the outer radiation belt. For preconditioned storm events, the correlation between the features of the seed population and relativistic electrons is not fully consistent with the energy-dependent processes. It is suggested that the good correlation between the radiation belt seed population and ≤1.0 MeV electrons contributes to the prediction of the evolution of ≤1.0 MeV electrons in the Earth’s outer radiation belt during periods of geomagnetic storms.

  15. Three-dimensional structural analysis of eukaryotic flagella/cilia by electron cryo-tomography

    Bui, Khanh Huy; Pigino, Gaia; Ishikawa, Takashi

    2011-01-01

    Based on the molecular architecture revealed by electron cryo-tomography, the mechanism of the bending motion of eukaryotic flagella/cilia is discussed. Electron cryo-tomography is a potential approach to analyzing the three-dimensional conformation of frozen hydrated biological macromolecules using electron microscopy. Since projections of each individual object illuminated from different orientations are merged, electron tomography is capable of structural analysis of such heterogeneous environments as in vivo or with polymorphism, although radiation damage and the missing wedge are severe problems. Here, recent results on the structure of eukaryotic flagella, which is an ATP-driven bending organelle, from green algae Chlamydomonas are presented. Tomographic analysis reveals asymmetric molecular arrangements, especially that of the dynein motor proteins, in flagella, giving insight into the mechanism of planar asymmetric bending motion. Methodological challenges to obtaining higher-resolution structures from this technique are also discussed

  16. Structure of liquid alkali metals as electron-ion plasmas

    Chaturvedi, D.K.; Senatore, G.; Tosi, M.P.

    1980-08-01

    The static structure factor of liquid alkali metals near freezing, and its dependence on temperature and pressure, are evaluated in an electron-ion plasma model from an accurate theoretical determination of the structure factor of the one-component classical plasma and electron-screening theory. Very good agreement is obtained with the available experimental data. (author)

  17. Electron equilibrium for parallel plate ionization chambers in gamma radiation fields

    Caldas, L.; Albuquerque, M. da P.P.

    1989-08-01

    Parallel plate ionization chambers, designed and constructed for use in low energy X-radiation fields, were tested in gamma radiation beams ( 6 Co and 137 Cs) of two different Calibration Laboratories, in order to study the electron equilibrium occurrence and to verify the possibility of their use for the detection of the kind of radiation too. (author) [pt

  18. Spectral distribution of radiation on plane and axial channeling of ultrarelativistic electrons

    Bazylev, V.A.; Glebov, V.I.; Zhevago, N.K.

    1980-01-01

    The spectral angular and polarization charactristics of the radiation from channeled ultrarelativistic electrons are calculated. Analytic expressions for the spectral-angular power density of the radiation are obtained for some realistic models of the continuous potential of the crystal planes and axes. A critical analysis is also presented of some existent results of the theory of radiation on channeling

  19. Coherently enhanced radiation reaction effects in laser-vacuum acceleration of electron bunches

    Smorenburg, P.W.; Kamp, L.P.J.; Geloni, G.; Luiten, O.J.

    2010-01-01

    The effects of coherently enhanced radiation reaction on the motion of subwavelength electron bunches in interaction with intense laser pulses are analyzed. The radiation reaction force behaves as a radiation pressure in the laser beam direction, combined with a viscous force in the perpendicular

  20. Electronic structures of elements according to ionization energies.

    Zadeh, Dariush H

    2017-11-28

    The electronic structures of elements in the periodic table were analyzed using available experimental ionization energies. Two new parameters were defined to carry out the study. The first parameter-apparent nuclear charge (ANC)-quantified the overall charge of the nucleus and inner electrons observed by an outer electron during the ionization process. This parameter was utilized to define a second parameter, which presented the shielding ability of an electron against the nuclear charge. This second parameter-electron shielding effect (ESE)-provided an insight into the electronic structure of atoms. This article avoids any sort of approximation, interpolation or extrapolation. First experimental ionization energies were used to obtain the two aforementioned parameters. The second parameter (ESE) was then graphed against the electron number of each element, and was used to read the corresponding electronic structure. The ESE showed spikes/peaks at the end of each electronic shell, providing insight into when an electronic shell closes and a new one starts. The electronic structures of elements in the periodic table were mapped using this methodology. These graphs did not show complete agreement with the previously known "Aufbau" filling rule. A new filling rule was suggested based on the present observations. Finally, a new way to organize elements in the periodic table is suggested. Two earlier topics of effective nuclear charge, and shielding factor were also briefly discussed and compared numerically to demonstrate the capability of the new approach.

  1. Correct Brillouin zone and electronic structure of BiPd

    Yaresko, Alexander; Schnyder, Andreas P.; Benia, Hadj M.; Yim, Chi-Ming; Levy, Giorgio; Damascelli, Andrea; Ast, Christian R.; Peets, Darren C.; Wahl, Peter

    2018-02-01

    A promising route to the realization of Majorana fermions is in noncentrosymmetric superconductors, in which spin-orbit coupling lifts the spin degeneracy of both bulk and surface bands. A detailed assessment of the electronic structure is critical to evaluate their suitability for this through establishing the topological properties of the electronic structure. This requires correct identification of the time-reversal-invariant momenta. One such material is BiPd, a recently rediscovered noncentrosymmetric superconductor which can be grown in large, high-quality single crystals and has been studied by several groups using angular resolved photoemission to establish its surface electronic structure. Many of the published electronic structure studies on this material are based on a reciprocal unit cell which is not the actual Brillouin zone of the material. We show here the consequences of this for the electronic structures and show how the inferred topological nature of the material is affected.

  2. Reliability Analysis of the CERN Radiation Monitoring Electronic System CROME

    AUTHOR|(CDS)2126870

    For the new in-house developed CERN Radiation Monitoring Electronic System (CROME) a reliability analysis is necessary to ensure compliance with the statu-tory requirements regarding the Safety Integrity Level. The required Safety Integrity Level by IEC 60532 standard is SIL 2 (for the Safety Integrated Functions Measurement, Alarm Triggering and Interlock Triggering). The first step of the reliability analysis was a system and functional analysis which served as basis for the implementation of the CROME system in the software “Iso-graph”. In the “Prediction” module of Isograph the failure rates of all components were calculated. Failure rates for passive components were calculated by the Military Standard 217 and failure rates for active components were obtained from lifetime tests by the manufacturers. The FMEA was carried out together with the board designers and implemented in the “FMECA” module of Isograph. The FMEA served as basis for the Fault Tree Analysis and the detection of weak points...

  3. On bolus for megavoltage photon and electron radiation therapy

    Vyas, Vedang; Palmer, Lisa; Mudge, Ray; Jiang, Runqing; Fleck, Andre; Schaly, Bryan; Osei, Ernest; Charland, Paule

    2013-01-01

    Frequently, in radiation therapy one must treat superficial lesions on cancer patients; these are at or adjacent to the skin. Megavoltage photon radiotherapy penetrates through the skin to irradiate deep-seated tumors, with skin-sparing property. Hence, to treat superficial lesions, one must use a layer of scattering material to feign as the skin surface. Although megavoltage electron beams are used for superficial treatments, one occasionally needs to enhance the dose near the surface. Such is the function of a “bolus,” a natural or synthetically developed material that acts as a layer of tissue to provide a more effective treatment to the superficial lesions. Other uses of boluses are to correct for varying surface contours and to add scattering material around the patient's surface. Materials used as bolus vary from simple water to metal and include various mixtures and compounds. Even with the modernization of the technology for external-beam therapy and the emergence of various commercial boluses, the preparation and utilization of a bolus in clinical radiotherapy remains an art. Considering the varying experiences and practices, this paper briefly summarizes available boluses that have been proposed and are employed in clinical radiotherapy. Although this review is not exhaustive, it provides some initial guidance and answers questions that may arise in clinical practice

  4. Free electron laser and coherent radiation. Working group summary

    Gover, A.; Csonka, P.; Deacon, D.

    1984-01-01

    The planned development of a new storage ring at SSRL gives hope for the exciting possibility that an x-ray laser may become available in a users facility. Such a device would certainly be a unique and revolutionary tool for scientific research and industrial applications, which may take advantage of the spatial and temporal coherence, high power and high brightness of this device in a wavelength regime where no alternative coherent radiation sources exist. The feasibility of implementing such a device in the new ring should be examined carefully by the ring designers. If conclusions are positive, the ring design should take into account the special requirements which are set by the x-ray laser design parameters. Our working group made the first step in this examination process. Most of the emphasis was put on the consideration of an X-Ray Free Electron Laser (XR FEL). FEL technology has developed in the last few years and was recently demonstrated to operate successfully in the visible wavelength regime in the ACO storage ring in Orsay

  5. Detailed Characteristics of Radiation Belt Electrons Revealed by CSSWE/REPTile Measurements

    Zhang, K.; Li, X.; Schiller, Q.; Gerhardt, D. T.; Millan, R. M.

    2016-12-01

    The outer radiation belt electrons are highly dynamic. We study the detailed characteristics of the relativistic electrons in the outer belt using measurements from the Colorado Student Space Weather Experiment (CSSWE) mission, a low Earth orbit Cubesat, which transverses the radiation belt four times in one orbit ( 1.5 hr) and has the advantage of measuring the dynamic activities of the electrons including their rapid precipitations. Among the features of the relativistic electrons, we show the measured electron distribution as a function of geomagnetic activities and local magnetic field strength. Moreover, a specific precipitation band, which happened on 19 Jan 2013, is investigated based on the conjunctive measurement of CSSWE and the Balloon Array for Radiation belt Relativistic Electron Losses (BARREL). In this precipitation band event, the net loss of the 0.58 1.63 MeV electrons (L=3.5 6) is estimated to account for 6.84% of the total electron content.

  6. Radiation defects in Te-implanted germanium. Electron microscopy and computer simulation studies

    Kalitzova, M.G.; Karpuzov, D.S.; Pashov, N.K.

    1985-01-01

    Direct observation of radiation damage induced by heavy ion implantation in crystalline germanium by means of high-resolution electron microscopy is reported. The dark-field lattice imaging mode is used, under conditions suitable for object-like imaging. Conventional TEM is used for estimating the efficiency of creating visibly damaged regions. Heavy ion damage clusters with three types of inner structure are observed: with near-perfect crystalline cores, and with metastable and stable amorphous cores. The MARLOWE computer code is used to simulate the atomic collision cascades and to obtain the lateral spread distributions of point defects created. A comparison of high-resolution electron microscopy (HREM) with computer simulation results shows encouraging agreement for the average cluster dimensions and for the lateral spread of vacancies and interstitials. (author)

  7. Radiation-hardened gate-around n-MOSFET structure for radiation-tolerant application-specific integrated circuits

    Lee, Min Su; Lee, Hee Chul

    2012-01-01

    To overcome the total ionizing dose effect on an n-type metal-oxide-semiconductor field-effect transistor (n-MOSFET), we designed a radiation-hardened gate-around n-MOSFET structure and evaluated it through a radiation-exposure experiment. Each test device was fabricated in a commercial 0.35-micron complementary metal-oxide-semiconductor (CMOS) process. The fabricated devices were evaluated under a total dose of 1 Mrad (Si) at a dose rate of 250 krad/h to obtain very high reliability for space electronics. The experimental results showed that the gate-around n-MOSFET structure had very good performance against 1 Mrad (Si) of gamma radiation, while the conventional n-MOSFET experienced a considerable amount of radiation-induced leakage current. Furthermore, a source follower designed with the gate-around transistor worked properly at 1 Mrad (Si) of gamma radiation while a source follower designed with the conventional n-MOSFET lost its functionality.

  8. Electronic structure of hybrid interfaces for polymer-based electronics

    Fahlman, M; Crispin, A; Crispin, X; Henze, S K M; Jong, M P de; Osikowicz, W; Tengstedt, C; Salaneck, W R

    2007-01-01

    The fundamentals of the energy level alignment at anode and cathode electrodes in organic electronics are described. We focus on two different models that treat weakly interacting organic/metal (and organic/organic) interfaces: the induced density of interfacial states model and the so-called integer charge transfer model. The two models are compared and evaluated, mainly using photoelectron spectroscopy data of the energy level alignment of conjugated polymers and molecules at various organic/metal and organic/organic interfaces. We show that two different alignment regimes are generally observed: (i) vacuum level alignment, which corresponds to the lack of vacuum level offsets (Schottky-Mott limit) and hence the lack of charge transfer across the interface, and (ii) Fermi level pinning where the resulting work function of an organic/metal and organic/organic bilayer is independent of the substrate work function and an interface dipole is formed due to charge transfer across the interface. We argue that the experimental results are best described by the integer charge transfer model which predicts the vacuum level alignment when the substrate work function is above the positive charge transfer level and below the negative charge transfer level of the conjugated material. The model further predicts Fermi level pinning to the positive (negative) charge transfer level when the substrate work function is below (above) the positive (negative) charge transfer level. The nature of the integer charge transfer levels depend on the materials system: for conjugated large molecules and polymers, the integer charge transfer states are polarons or bipolarons; for small molecules' highest occupied and lowest unoccupied molecular orbitals and for crystalline systems, the relevant levels are the valence and conduction band edges. Finally, limits and further improvements to the integer charge transfer model are discussed as well as the impact on device design. (topical review)

  9. The electronic structure of core states under extreme compressions

    Straub, G.K.

    1992-01-01

    At normal density and for modest compressions, the electronic structure of a metal can be accurately described by treating the conduction electrons and their interactions with the usual methods of band theory. The core electrons remain essentially the same as for an isolated free atom and do not participate in the bonding forces responsible for creating a condensed phase. As the density increases, the core electrons begin to ''see'' one another as the overlap of the tails of wave functions can no longer be neglected. The electronic structure of the core electrons is responsible for an effective repulsive interaction that eventually becomes free-electron-like at very high compressions. The electronic structure of the interacting core electrons may be treated in a simple manner using the Atomic Surface Method (ASM). The ASM is a first-principles treatment of the electronic structure involving a rigorous integration of the Schroedinger equation within the atomic-sphere approximation. Solid phase wave functions are constructed from isolated atom wave functions and the band width W l and the center of gravity of the band C l are obtained from simple formulas. The ASM can also utilize analytic forms of the atomic wave functions and thus provide direct functional dependence of various aspects of the electronic structure. Of particular use in understanding the behavior of the core electrons, the ASM provides the ability to analytically determine the density dependence of the band widths and positions. The process whereby core states interact with one another is best viewed as the formation of narrow electron bands formed from atomic states. As the core-core overlap increases, the bands increase in width and mean energy. In Sec.3 this picture is further developed and from the ASM one obtains the analytic dependence on density of the relative motion of the different bands. Also in Sec. 3 is a discussion of the transition to free electron bands

  10. [Morphological structure of rat epiphysis exposed to electromagnetic radiation from communication devices].

    Yashchenko, S G; Rybalko, S Yu

    Pineal gland is one of the most important components of homeostasis - the supporting system of the body. It participates in the launch of stress responses, restriction of their development, prevention of adverse effects on the body. There was proved an impact of electromagnetic radiation on the epiphysis. However, morphological changes in the epiphysis under exposure to electromagnetic radiation of modern communication devices are studied not sufficiently. For the time present the population is daily exposed to electromagnetic radiation, including local irradiation on the brain. These date determined the task of this research - the study of the structure of rat pineal gland under the exposure to electromagnetic radiation from personal computers and mobile phones. These date determined the task of this research - the study of the structure of rat pineal gland under the exposure to electromagnetic radiation from personal computers and mobile phones. Performed transmission electron microscopy revealed signs of degeneration of dark and light pinealocytes. These signs were manifested in the development of a complex of general and specific morphological changes. There was revealed the appearance of signs of aging and depletion transmission electron microscopy both in light and dark pinealocytes. These signs were manifested in the accumulation of lipofuscin granules and electron-dense "brain sand", the disappearance of nucleoli, cytoplasm vacuolization and mitochondrial cristae enlightenment.

  11. Rapid flattening of butterfly pitch angle distributions of radiation belt electrons by whistler-mode chorus

    Yang, Chang; Su, Zhenpeng; Xiao, Fuliang; Zheng, Huinan; Wang, Yuming; Wang, Shui; Spence, H. E.; Reeves, G. D.; Baker, D. N.; Blake, J. B.; Funsten, H. O.

    2016-08-01

    Van Allen radiation belt electrons exhibit complex dynamics during geomagnetically active periods. Investigation of electron pitch angle distributions (PADs) can provide important information on the dominant physical mechanisms controlling radiation belt behaviors. Here we report a storm time radiation belt event where energetic electron PADs changed from butterfly distributions to normal or flattop distributions within several hours. Van Allen Probes observations showed that the flattening of butterfly PADs was closely related to the occurrence of whistler-mode chorus waves. Two-dimensional quasi-linear STEERB simulations demonstrate that the observed chorus can resonantly accelerate the near-equatorially trapped electrons and rapidly flatten the corresponding electron butterfly PADs. These results provide a new insight on how chorus waves affect the dynamic evolution of radiation belt electrons.

  12. Rapid flattening of butterfly pitch angle distributions of radiation belt electrons by whistler-mode chorus

    Yang, Chang; Changsha University of Science and Technology, Changsha; Su, Zhenpeng; Xiao, Fuliang; Zheng, Huinan

    2016-01-01

    Van Allen radiation belt electrons exhibit complex dynamics during geomagnetically active periods. Investigation of electron pitch angle distributions (PADs) can provide important information on the dominant physical mechanisms controlling radiation belt behaviors. In this paper, we report a storm time radiation belt event where energetic electron PADs changed from butterfly distributions to normal or flattop distributions within several hours. Van Allen Probes observations showed that the flattening of butterfly PADs was closely related to the occurrence of whistler-mode chorus waves. Two-dimensional quasi-linear STEERB simulations demonstrate that the observed chorus can resonantly accelerate the near-equatorially trapped electrons and rapidly flatten the corresponding electron butterfly PADs. Finally, these results provide a new insight on how chorus waves affect the dynamic evolution of radiation belt electrons.

  13. Basic radiation effects in nuclear power electronics technology

    Gover, J.E.; Srour, J.R.

    1985-05-01

    An overview is presented of the effects of radiation in microelectronics technology. The approach taken throughout these notes is to review microscopic phenomena associated with radiation effects and to show how these lead to macroscopic effects in semiconductor devices and integrated circuits. Bipolar integrated circuits technology is reviewed in Appendix A. Appendix B gives present and future applications of radiation-tolerant microelectronics in nuclear power applications as well as the radiation tolerance requirements of these applications

  14. Transmission electron-microscopic studies of structural changes in polycrystalline graphite after high temperature irradiation

    Platonov, P.A.; Gurovich, B.A.; Shtrombakh, Ya.I.; Karpukhin, V.I.

    1985-01-01

    Transmission electron-microscopic investigation of polycrystalline graphite before and after irradiation is carried out. The direct use of graphite samples after ion thinning, as an inquiry subject is the basic peculiarity of the work. Main structural components of MPG-6 graphite before and after irradiation are revealed, the structural mechanism of the reactor graphite destruction under irradiation is demonstrated. The mean values of L αm and L cm crystallite dimensions are determined. Radiation defects, occuring in some crystallites after irradiation are revealed by the dark-field electron microscopy method

  15. Radiation damage to DNA: The importance of track structure

    Hill, M A

    1999-01-01

    A wide variety of biological effects are induced by ionizing radiation, from cell death to mutations and carcinogenesis. The biological effectiveness is found to vary not only with the absorbed dose but also with the type of radiation and its energy, i.e., with the nature of radiation tracks. An overview is presented of some of the biological experiments using different qualities of radiation, which when compared with Monte Carlo track structure studies, have highlighted the importance of the localized spatial properties of stochastic energy deposition on the nanometer scale at or near DNA. The track structure leads to clustering of damage which may include DNA breaks, base damage etc., the complexity of the cluster and therefore its biological repairability varying with radiation type. The ability of individual tracks to produce clustered damage, and the subsequent biological response are important in the assessment of the risk associated with low-level human exposure. Recent experiments have also shown that...

  16. Application of the equivalent radiator method for radiative corrections to the spectra of elastic electron scattering by nuclei

    I. S. Timchenko

    2015-07-01

    Full Text Available For calculating the radiative tails in the spectra of inelastic electron scattering by nuclei, the approximation, namely, the equivalent radiator method (ERM, is used. However, the applicability of this method for evaluating the radiative tail from the elastic scattering peak has been little investigated, and therefore, it has become the subject of the present study for the case of light nuclei. As a result, spectral regions were found, where a significant discrepancy between the ERM calculation and the exact-formula calculation was observed. A link was established between this phenomenon and the diffraction minimum of the squared form-factor of the nuclear ground state. Varieties of calculations were carried out for different kinematics of electron scattering by nuclei. The analysis of the calculation results has shown the conditions, at which the equivalent radiator method can be applied for adequately evaluating the radiative tail of the elastic scattering peak.

  17. Orbital Models and Electronic Structure Theory

    Linderberg, Jan

    2012-01-01

    This tribute to the work by Carl Johan Ballhausen focuses on the emergence of quantitative means for the study of the electronic properties of complexes and molecules. Development, refinement and application of the orbital picture elucidated electric and magnetic features of ranges of molecules...

  18. Nano structural anodes for radiation detectors

    Cordaro, Joseph V.; Serkiz, Steven M.; McWhorter, Christopher S.; Sexton, Lindsay T.; Retterer, Scott T.

    2015-07-07

    Anodes for proportional radiation counters and a process of making the anodes is provided. The nano-sized anodes when present within an anode array provide: significantly higher detection efficiencies due to the inherently higher electric field, are amenable to miniaturization, have low power requirements, and exhibit a small electromagnetic field signal. The nano-sized anodes with the incorporation of neutron absorbing elements (e.g., .sup.10B) allow the use of neutron detectors that do not use .sup.3He.

  19. Crystal structure from one-electron theory

    Skriver, H. L.

    1985-01-01

    The authors have studied the crystal structure of all the 3d, 4d, and 5d transition metals at zero pressure and temperature by means of the linear muffin-tin orbital method and Andersen's force theorem. They find that, although the structural energy differences seem to be overestimated by the the......The authors have studied the crystal structure of all the 3d, 4d, and 5d transition metals at zero pressure and temperature by means of the linear muffin-tin orbital method and Andersen's force theorem. They find that, although the structural energy differences seem to be overestimated...

  20. Responsibility structure in medical radiation applications

    Beekman, Z.M.

    1989-01-01

    The author discusses the various aspects of the responsibilities of physicians and clinical physicists with regard to radiation protection in medical applications of ionizing radiation. It becomes still clearer that the physician, who carries out the examination or the treatment, also has to bear the responsibility. this holds for the indication assessment as well as for optimization of the quality of the examination or treatment versus radiation burden of the patient, radiologic worker and thirds. Further it is clear that the physician in these will have to delegate specific tasks and responsibilities, whether or not in the elongated-arm construction. The clinical physicist is responsible in particular for the applications of the physical methods and watches the quality of the apparatus and methods used. As such he also is responsible for the technical workers, who take care of the preventive and corrective maintenance. The principal responsibility of the clinical physicist however lies in the field of standardization and calibration of medical-physical instruments. Besides this investigation into and development of new techniques, methods and apparatus come up, while also education and training of various profession groups involved need attention. (author). 6 refs.; 1 tab

  1. Analysis of Proton Radiation Effects on Gallium Nitride High Electron Mobility Transistors

    2017-03-01

    non - ionizing proton radiation damage effects at different energy levels on a GaN-on-silicon high electron mobility transistor...DISTRIBUTION CODE 13. ABSTRACT (maximum 200 words) In this work, a physics-based simulation of non - ionizing proton radiation damage effects at different...Polarization . . . . . . . . . . . . . . 6 2.3 Non - Ionizing Radiation Damage Effects . . . . . . . . . . . . . . . 10 2.4 Non - Ionizing Radiation Damage in

  2. Low-Dimensional Nanomaterials and Molecular Dielectrics for Radiation-Hard Electronics

    McMorrow, Julian

    for SAND deposition, supporting the SAND superlattice structure and its superlative electronic properties on a metal surface. This result is critical for conducting fundamental transport studies when integrating SAND with novel semiconductor materials, as well as enabling complex circuit integration and SAND on flexible substrates. Altogether, these works drive the integration of novel nanoelectronic materials for future electronics while providing an understanding of their varying radiation response mechanisms to enable their adoption in future space-bound applications.

  3. Complex band structure and electronic transmission eigenchannels

    Jensen, Anders; Strange, Mikkel; Smidstrup, Soren

    2017-01-01

    and complex band structure, in this case individual eigenchannel transmissions and different complex bands. We present calculations of decay constants for the two most conductive states as determined by complex band structure and standard DFT Landauer transport calculations for one semi-conductor and two...

  4. Electronic structure in high temperature superconducting oxides

    Howell, R.H.; Sterne, P.; Solal, F.; Fluss, M.J.; Tobin, J.; O'Brien, J.; Radousky, H.B.; Haghighi, H.; Kaiser, J.H.; Rayner, S.L.; West, R.N.; Liu, J.Z.; Shelton, R.; Olsen, C.G.; Gu, C.; Kitazawa, K.; Kojima, H.

    1991-01-01

    We have performed measurements on entwined single crystals of YBCO using both photoemission and positron angular correlation of annihilation radiation and on single crystals of LSCO using only angular correlation. Fermi surface features in good agreement with band theory were found and identified in all of the measurements. In photoemission the Fermi momentum was fixed for several points and the band dispersion below the Fermi energy was mapped. In positron angular correlation measurements the shape of the Fermi surface was mapped for the CuO chains (YBCO) and the CuO planes (LSCO). Demonstration of the existence of Fermi surfaces in the HTSC materials points a direction for future theoretical considerations

  5. Syntheses and electronic structures of decamethylmetallocenes

    Robbins, J.L.

    1981-04-01

    The synthesis of decamethylmanganocene [(eta-C 5 (CH 3 ) 5 ) 2 Mn or (Me 5 Cp) 2 Mn)] is described. Magnetic susceptibility and electron paramagnetic resonance (EPR) studies show that (Me 5 Cp) 2 Mn is a low-spin, 17-electron compound with an orbitally degenerate, 2 E/sub 2g/ [e/sub 2g/ 3 a/sub 1g/ 2 ] ground state. An x-ray crystallographic study of (Me 5 Cp) 2 Mn shows that it is a monomeric, D/sub 5d/ decamethylmetallocene with metal to ring carbon distances that are about 0.3 A shorter than those determined for high-spin manganocenes. The syntheses of new (Me 5 Cp) 2 M (M = Mg,V,Cr,Co, and Ni) and [(Me 5 Cp) 2 M]PF 6 (M = Cr,Co, and Ni) compounds are described. In addition, a preparative route to a novel, dicationic decamethylmetallocene, [(Me 5 Cp) 2 Ni](PF 6 ) 2 is reported. Infrared, nuclear magnetic resonance, magnetic susceptibility, and/or x-ray crystallographic studies indicate that all the above compounds are D/sub 5d/ or D/sub 5h/ decamethylmetallocenes with low-spin electronic configurations. Cyclic voltammetry studies verify the reversibility and the one-electron nature of the (Me 5 Cp) 2 M → [(Me 5 Cp) 2 M] + (M = Cr,Mn,Fe,Co,Ni), [(Me 5 Cp) 2 Mn] - → (Me 5 Cp) 2 Mn and [(Me 5 Cp) 2 Ni] + → [Me 5 Cp) 2 Ni] 2+ redox reactions. These studies reveal that the neutral decamethylmetallocenes are much more easily oxidized than their metallocene counterparts. This result attests to the electron-donating properties of the ten substituent methyl groups. Proton and carbon-13 NMR data are reported for the diamagnetic Mg(II), Mn(I), Fe(II), Co(III), and Ni(IV) decamethylmetallocenes and for [(Me 5 Cp) 2 V(CO) 2 ] + . The uv-visible absorption spectra of the 15-, 18- and 20- electron decamethylmetallocenes are also reported

  6. Syntheses and electronic structures of decamethylmetallocenes

    Robbins, J.L.

    1981-04-01

    The synthesis of decamethylmanganocene ((eta-C/sub 5/(CH/sub 3/)/sub 5/)/sub 2/Mn or (Me/sub 5/Cp)/sub 2/Mn)) is described. Magnetic susceptibility and electron paramagnetic resonance (EPR) studies show that (Me/sub 5/Cp)/sub 2/Mn is a low-spin, 17-electron compound with an orbitally degenerate, /sup 2/E/sub 2g/ (e/sub 2g//sup 3/ a/sub 1g//sup 2/) ground state. An x-ray crystallographic study of (Me/sub 5/Cp)/sub 2/Mn shows that it is a monomeric, D/sub 5d/ decamethylmetallocene with metal to ring carbon distances that are about 0.3 A shorter than those determined for high-spin manganocenes. The syntheses of new (Me/sub 5/Cp)/sub 2/M (M = Mg,V,Cr,Co, and Ni) and ((Me/sub 5/Cp)/sub 2/M)PF/sub 6/ (M = Cr,Co, and Ni) compounds are described. In addition, a preparative route to a novel, dicationic decamethylmetallocene, ((Me/sub 5/Cp)/sub 2/Ni)(PF/sub 6/)/sub 2/ is reported. Infrared, nuclear magnetic resonance, magnetic susceptibility, and/or x-ray crystallographic studies indicate that all the above compounds are D/sub 5d/ or D/sub 5h/ decamethylmetallocenes with low-spin electronic configurations. Cyclic voltammetry studies verify the reversibility and the one-electron nature of the (Me/sub 5/Cp)/sub 2/M ..-->.. ((Me/sub 5/Cp)/sub 2/M)/sup +/ (M = Cr,Mn,Fe,Co,Ni), ((Me/sub 5/Cp)/sub 2/Mn)/sup -/ ..-->.. (Me/sub 5/Cp)/sub 2/Mn and ((Me/sub 5/Cp)/sub 2/Ni)/sup +/ ..-->.. (Me/sub 5/Cp)/sub 2/Ni)/sup 2 +/ redox reactions. These studies reveal that the neutral decamethylmetallocenes are much more easily oxidized than their metallocene counterparts. This result attests to the electron-donating properties of the ten substituent methyl groups. Proton and carbon-13 NMR data are reported for the diamagnetic Mg(II), Mn(I), Fe(II), Co(III), and Ni(IV) decamethylmetallocenes and for ((Me/sub 5/Cp)/sub 2/V(CO)/sub 2/)/sup +/. The uv-visible absorption spectra of the 15-, 18- and 20- electron decamethylmetallocenes are also reported.

  7. Electronic structure and optical properties of solid C60

    Mattesini, M.; Ahuja, R.; Sa, L.; Hugosson, H.W.; Johansson, B.; Eriksson, O.

    2009-01-01

    The electronic structure and the optical properties of face-centered-cubic C 60 have been investigated by using an all-electron full-potential method. Our ab initio results show that the imaginary dielectric function for high-energy values looks very similar to that of graphite, revealing close electronic structure similarities between the two systems. We have also identified the origin of different peaks in the dielectric function of fullerene by means of the calculated electronic density of states. The computed optical spectrum compares fairly well with the available experimental data for the Vis-UV absorption spectrum of solid C 60 .

  8. Radiation-chemical copolymerization of oligoalkylene- maleinants of alicyclic structure

    Bondarenko, P.A.; Videnina, N.G.; Omel'chenko, S.I.

    1982-01-01

    Effect of glycol used in synthesis on the properties of oligoalkylenemaleinates and their copolymers is considered. It is shown that oligoesters during copolymerization with sterol have enough high sensitivity to the effect of gamma radiation and electrons of high energy. The copolymers have a good mechanical-and-physical properties at low absorbed doses

  9. Calculating the radiation characteristics of accelerated electrons in laser-plasma interactions

    Li, X. F.; Yu, Q.; Qu, J. F.; Kong, Q.; Gu, Y. J.; Ma, Y. Y.; Kawata, S.

    2016-01-01

    In this paper, we studied the characteristics of radiation emitted by electrons accelerated in a laser–plasma interaction by using the Lienard–Wiechert field. In the interaction of a laser pulse with a underdense plasma, electrons are accelerated by two mechanisms: direct laser acceleration (DLA) and laser wakefield acceleration (LWFA). At the beginning of the process, the DLA electrons emit most of the radiation, and the DLA electrons emit a much higher peak photon energy than the LWFA electrons. As the laser–plasma interaction progresses, the LWFA electrons become the major radiation emitter; however, even at this stage, the contribution from DLA electrons is significant, especially to the peak photon energy.

  10. Electronic structure of fractionally nuclear charged atoms

    Pavao, Antonio C.; Bastos, Cristiano C.; Ferreira, Joacy V.

    2008-01-01

    Different properties of quark chemistry are studied by performing accurate ab initio Hartree- Fock calculations on fractionally nuclear charged atoms. Ground and first excited states of sodium atoms with quarks attached to the nucleus are obtained using CI calculations. It is suggested that the sodium 2 P -> 2 S electronic transition can be used as a guide in searching for unconfined quarks. Also, the variation of the binding electronic energy with nuclear charge in the isoelectronic series of fractionally nuclear charged atoms A ±2/3 and A ±1/3 (A = H, Li, Na, P and Ca) is analyzed. The present calculations suggest that unconfined colored particles have large appetite for heavy nuclei and that quark-antiquark pairs could be stabilized in presence of the atomic matter. (author)

  11. Tailoring electronic structure of polyazomethines thin films

    J. Weszka; B. Hajduk; M. Domański; M. Chwastek; J. Jurusik; B. Jarząbek; H. Bednarski; P. Jarka

    2010-01-01

    Purpose: The aim of this work is to show how electronic properties of polyazomethine thin films deposited by chemical vapor deposition method (CVD) can be tailored by manipulating technological parameters of pristine films preparation as well as modifying them while the as-prepared films put into iodine atmosphere.Design/methodology/approach: The recent achievements in the field of designing and preparation methods to be used while preparing polymer photovoltaic solar cells or optoelectronic ...

  12. Red Shift and Broadening of Backward Harmonic Radiation from Electron Oscillations Driven by Femtosecond Laser Pulse

    Tian Youwei; Yu Wei; Lu Peixiang; Senecha, Vinod K; Han, Xu; Deng Degang; Li Ruxin; Xu Zhizhan

    2006-01-01

    The characteristics of backward harmonic radiation due to electron oscillations driven by a linearly polarized fs laser pulse are analysed considering a single electron model. The spectral distributions of the electron's backward harmonic radiation are investigated in detail for different parameters of the driver laser pulse. Higher order harmonic radiations are possible for a sufficiently intense driving laser pulse. We have shown that for a realistic pulsed photon beam, the spectrum of the radiation is red shifted as well as broadened because of changes in the longitudinal velocity of the electrons during the laser pulse. These effects are more pronounced at higher laser intensities giving rise to higher order harmonics that eventually leads to a continuous spectrum. Numerical simulations have further shown that by increasing the laser pulse width the broadening of the high harmonic radiations can be controlled

  13. High temperature, radiation hardened electronics for application to nuclear power plants

    Gover, J.E.

    1980-01-01

    Electronic circuits were developed and built at Sandia for many aerospace and energy systems applications. Among recent developments were high temperature electronics for geothermal well logging and radiation hardened electronics for a variety of aerospace applications. Sandia has also been active in technology transfer to commercial industry in both of these areas

  14. Beam structure of Jupiter's decametric radiation

    Maeda, K; Carr, T D

    1984-03-08

    The well-defined zones of central meridian longitude within which the probability of jovian radio emission at frequencies near 22 MHz is relatively high are known as sources A, B and C. Each consists of a component for which the emission probability is strongly correlated with Io's orbital position, and another that is Io-unrelated. The paper presents convincing evidence based on concurrent observations from two Voyager spacecraft and a terrestrial observatory that the component of source A radiation that is not correlated with Io's position is generally emitted in co-rotating searchlight beams of distinctive cross-sectional shape.

  15. Electronic structure and formation energy of a vacancy in aluminum

    Chakraborty, B.; Siegel, R.W.

    1981-11-01

    The electronic structure of a vacancy in Al was calculated self-consistently using norm-conserving ionic pseudopotentials obtained from ab initio atomic calculations. A 27-atom-site supercell containing 1 vacancy and 26 atoms was used to simulate the environment of the vacancy. A vacancy formation energy of 1.5 eV was also calculated (cf. the experimental value of 0.66 eV). The effects of the supercell and the nature of the ionic potential on the resulting electronic structure and formation energy are discussed. Results for the electronic structure of a divacancy are also presented. 3 figures

  16. One-Electron Theory of Metals. Cohesive and Structural Properties

    Skriver, Hans Lomholt

    The work described in the report r.nd the 16 accompanying publications is based upon a one-electron theory obtained within the local approximation to density-functional theory, and deals with the ground state of metals as obtained from selfconsistent electronic-structure calculations performed...... by means of the Linear Muffin-Tin Orbital (LMTO) method. It has been the goal of the work to establish how well this one-electron approach describes physical properties such as the crystal structures of the transition metals, the structural phase transitions in the alkali, alkaline earth, and rare earth...

  17. Structure and electron-ion correlation in liquid Mg

    Tahara, Shuta [Graduate School of Sciences, Kyushu University, 4-2-1 Ropponmatsu Chuo-ku, Fukuoka 810-8560 (Japan); Fujii, Hiroyuki [Graduate School of Sciences, Kyushu University, 4-2-1 Ropponmatsu Chuo-ku, Fukuoka 810-8560 (Japan); Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Yokota, Yukinobu [Graduate School of Sciences, Kyushu University, 4-2-1 Ropponmatsu Chuo-ku, Fukuoka 810-8560 (Japan); Kawakita, Yukinobu [Department of Physics, Faculty of Sciences, Kyushu University, 4-2-1 Ropponmatsu Chuo-ku, Fukuoka 810-8560 (Japan); Kohara, Shinji [Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Takeda, Shin' ichi [Department of Physics, Faculty of Sciences, Kyushu University, 4-2-1 Ropponmatsu Chuo-ku, Fukuoka 810-8560 (Japan)]. E-mail: takeda@rc.kyushu-u.ac.jp

    2006-11-15

    For liquid Mg at 700 deg. C, structure factors were obtained from both neutron and X-ray diffraction measurements. The bond angle and coordination number distributions were derived from the reverse Monte Carlo analysis. By a combination of both structure factors, charge density function and electron-ion partial structure factor were deduced.

  18. High pressure and synchrotron radiation studies of solid state electronic instabilities

    Pifer, J.H.; Croft, M.C.

    1992-04-01

    This report discusses Eu and General Valence Instabilities; Ce Problem: L 3 Spectroscopy Emphasis; Bulk Property Emphasis; Transition Metal Compound Electronic Structure; Electronic Structure-Phonon Coupling Studies; High Temperature Superconductivity and Oxide Materials; and Novel Materials Collaboration with Chemistry

  19. VU-B radiation inhibits the photosynthetic electron transport chain in chlamydomonas reinhardtii

    Cai, W.; Li, X.; Chen, L.

    2016-01-01

    UV radiation of sunlight is one of harmful factors for earth organisms, especially for photoautotrophs because they require light for energy and biomass production. A number of works have already been done regarding the effects of UV-B radiation at biochemical and molecular level, which showed that UV-B radiation could inhibit photosynthesis activity and reduce photosynthetic electron transport. However quite limited information can accurately make out inhibition site of UV-B radiation on photosynthetic electron transport. In this study, this issue was investigated through measuring oxygen evolution activity, chlorophyll a fluorescence and gene expression in a model unicellular green alga Chlamydomonas reinhardtii. Our results indicated that UV-B radiation could evidently decrease photosynthesis activity and inhibit electron transport by blocking electron transfer process from the first plastoquinone electron acceptors QA to second plastoquinone electron acceptors QB, but not impair electron transfer from the water oxidizing complex to QA. The psbA gene expression was also altered by UV-B radiation, where up-regulation occurred at 2, 4 and 6h after exposure and down-regulation happened at 12 and 24 h after exposure. These results suggested that UV-B could affects D1 protein normal turnover, so there was not enough D1 for binding with QB, which may affect photosynthetic electron transport and photosynthesis activity. (author)

  20. Nodal Structure of the Electronic Wigner Function

    Schmider, Hartmut; Dahl, Jens Peder

    1996-01-01

    On the example of several atomic and small molecular systems, the regular behavior of nodal patterns in the electronic one-particle reduced Wigner function is demonstrated. An expression found earlier relates the nodal pattern solely to the dot-product of the position and the momentum vector......, if both arguments are large. An argument analogous to the ``bond-oscillatory principle'' for momentum densities links the nuclear framework in a molecule to an additional oscillatory term in momenta parallel to bonds. It is shown that these are visible in the Wigner function in terms of characteristic...

  1. Electronic structure of the light actinides

    Dunlap, B.D.

    1976-01-01

    In the last few years, considerable advances have been made in our understanding of the properties of the light actinides. Although these are 5f transition elements formally equivalent to the lanthanide (4f) elements, these materials show a much more varied behavior due to the larger spatial extent and ionizability of the 5f electrons. A review is given of some areas of current interest, especially where hyperfine measurements have played an active role. These include studies of a variety of magnetic phenomena, systematics of isomer shift measurements, and studies of paramagnetic relaxation

  2. Radiation modification and interaction mechanism of polypropylene and polyethylene by protons and electrons

    Wang Guanghou

    1988-10-01

    A systematic investigation of radiation effects on isotactic polypropylene (PP) and low-density polyethylene (PE) films by protons and electrons is reported. Electrons can make polyethylene cross-linked and polypropylene crached while protons can improve the PP mechanical properties and deteriorate polyethylene with increasing the irradiation dose. The structural analysis shows that conversion between α and β phases occurs and the crystallinity remains constant in the electron-irradiated polypropylene whereas the network structure is formed by allyl-type radicals in the e - -irradiated polyethylene. The infrared spectra indicate that conformational changes have taken place in the polypropylene under proton bombardment, such as the transition from an ordered to a disordered state in the crystalline region, the formation of double bonds as well as trans-conformations. This leads to the cross-linking between macromolecules of polypropylene at the proper irradiation doses, thus enhancing its mechanical properties. The cross-linking of polypropylene by proton bombardment observed and its properties may have some potential applications

  3. The effect of electron beam radiations on testicular damage in mice, Mus musculus

    Vikram, S.; Nair, Vijay Mala Grover

    2013-01-01

    Adult male Swiss albino mice, Mus musculus (8-10 weeks old) weighing 28±2.5 gm were exposed to varying doses (2-12 Gy) of electron beam radiations and maintained in animal house at 26-28 C. The animals were sacrificed following 35 and 60 days following exposure to electron beam radiations. The LD-50 value, change in the weight and histological details of the testis, sperm count, sperm shape abnormalities and sperm motility were recorded. The data suggests that electron beam radiations is a potential inducer to cause reproductive system dysfunctions which probably may be responsible leading to infertility. (author)

  4. Six-frame picosecond radiation camera based on hydrated electron photoabsorption phenomena

    Coutts, G.W.; Olk, L.B.; Gates, H.A.; St Leger-Barter, G.

    1977-01-01

    To obtain picosecond photographs of nanosecond radiation sources, a six-frame ultra-high speed radiation camera based on hydrated electron absorption phenomena has been developed. A time-dependent opacity pattern is formed in an acidic aqueous cell by a pulsed radiation source. Six time-resolved picosecond images of this changing opacity pattern are transferred to photographic film with the use of a mode-locked dye laser and six electronically gated microchannel plate image intensifiers. Because the lifetime of the hydrated electron absorption centers can be reduced to picoseconds, the opacity patterns represent time-space pulse profile images

  5. System for determining absorbed dose and its distribution for high-energy electron radiation

    Hegewald, H.; Wulff, W.

    1977-01-01

    Taking into account the polarization effect, the dose determination for high-energy electron radiation from particle accelerators depends on the knowledge of the energy dependence of the mass stopping power. Results obtained with thermoluminescent dosemeters agree with theoretical values. For absorbed dose measurements the primary energy of electron radiation has been determined by nuclear photoreactions, and the calculation of the absorbed dose from charge measurements by means of the mass stopping power is described. Thus the calibration of ionization chambers for high-energy electron radiation by absolute measurements with the Faraday cage and chemical dosemeters has become possible. (author)

  6. Electronic structure and isomer shifts of Sn halides

    Terra, J.; Guenzburger, D.

    1988-01-01

    The all-electron first-principles Discrete Variational method was employed to study the electronic structure of SnF 4 , SnCl 4 , SnBr 4 and SnI 4 . Values of the electronic density at the Sn nucleus were derived and related to 119 Sn Isomer Shifts to obtain the nuclear constant Δ 2 >. Differences in values of ρ(o) area discussed in terms of the chemical bonding between Sn and halogen atoms. (author) [pt

  7. Electronic structure of graphene beyond the linear dispersion regime

    POWER, STEPHEN; FERREIRA, MAURO

    2011-01-01

    PUBLISHED Among the many interesting features displayed by graphene, one of the most attractive is the simplicity with which its electronic structure can be described. The study of its physical properties is significantly simplified by the linear dispersion relation of electrons in a narrow range around the Fermi level. Unfortunately, the mathematical simplicity of graphene electrons is limited only to this narrow energy region and is not very practical when dealing with problems that invo...

  8. Phase stability and electronic structure of transition-metal aluminides

    Carlsson, A.E.

    1992-01-01

    This paper will describe the interplay between die electronic structure and structural energetics in simple, complex, and quasicrystalline Al-transition metal (T) intermetallics. The first example is the Ll 2 -DO 22 competition in Al 3 T compounds. Ab-initio electronic total-energy calculations reveal surprisingly large structural-energy differences, and show that the phase stability of both stoichiometric and ternary-substituted compounds correlates closely with a quasigap in the electronic density of states (DOS). Secondly, ab-initio calculations for the structural stability of the icosahedrally based Al 12 W structure reveal similar quasigap effects, and provide a simple physical explanation for the stability of the complex aluminide structures. Finally, parametrized tight-binding model calculations for the Al-Mn quasicrystal reveal a large spread in the local Mn DOS behavior, and support a two-site model for the quasicrystal's magnetic behavior

  9. Electronic structure of filled tetrahedral semiconductors

    Wood, D.M.; Zunger, Alex; Groot, R. de

    1985-01-01

    We discuss the susceptibility of zinc-blende semiconductors to band-structure modification by insertion of small atoms at their tetrahedral interstitial states. GaP is found to become a direct-gap semiconductor with two He atoms present at its interstitial sites; Si does not. Analysis of the factors

  10. Electronic Band Structure of Helical Polyisocyanides.

    Champagne, Benoît; Liégeois, Vincent; Fripiat, Joseph G; Harris, Frank E

    2017-10-19

    Restricted Hartree-Fock computations are reported for a methyl isocyanide polymer (repeating unit -C═N-CH 3 ), whose most stable conformation is expected to be a helical chain. The computations used a standard contracted Gaussian orbital set at the computational levels STO-3G, 3-21G, 6-31G, and 6-31G**, and studies were made for two line-group configurations motivated by earlier work and by studies of space-filling molecular models: (1) A structure of line-group symmetry L9 5 , containing a 9-fold screw axis with atoms displaced in the axial direction by 5/9 times the lattice constant, and (2) a structure of symmetry L4 1 that had been proposed, containing a 4-fold screw axis with translation by 1/4 of the lattice constant. Full use of the line-group symmetry was employed to cause most of the computational complexity to depend only on the size of the asymmetric repeating unit. Data reported include computed bond properties, atomic charge distribution, longitudinal polarizability, band structure, and the convoluted density of states. Most features of the description were found to be insensitive to the level of computational approximation. The work also illustrates the importance of exploiting line-group symmetry to extend the range of polymer structural problems that can be treated computationally.

  11. Electronic structure and ionicity of actinide oxides from first principles

    Petit, Leon; Svane, Axel; Szotek, Z.

    2010-01-01

    The ground-state electronic structures of the actinide oxides AO, A2O3, and AO2 (A=U, Np, Pu, Am, Cm, Bk, and Cf) are determined from first-principles calculations, using the self-interaction corrected local spin-density approximation. Emphasis is put on the degree of f-electron localization, whi...

  12. On the electronic structure of high Tc superconductors

    Fink, J.; Nuecker, N.; Romberg, H.; Alexander, M.; Knupfer, M.; Mante, J.; Claessen, R.; Buslaps, T.; Harm, S.; Manzke, R.; Skibowski, M.

    1992-01-01

    Studies of the electronic structure of high-T c superconductors and related compounds by high-energy spectroscopies are reviewed. In particular, we report on investigations by electron energy-loss, angle-resolved photoemission, and inverse angle-resolved photoemission spectroscopy. Information on the symmetry and the character of states close to the Fermi level has been obtained. 25 refs., 8 figs

  13. Electronic structure and equilibrium properties of hcp titanium

    The electronic structures of hexagonal-close-packed divalent titanium (3-d) and zirconium (4-d) transition metals are studied by using a non-local model potential method. From the present calculation of energy bands, Fermi energy, density of states and the electronic heat capacity of these two metals are determined and ...

  14. Weiss oscillations in the electronic structure of modulated graphene

    Tahir, M; Sabeeh, K; MacKinnon, A

    2007-01-01

    We present a theoretical study of the electronic structure of modulated graphene in the presence of a perpendicular magnetic field. The density of states and the bandwidth for the Dirac electrons in this system are determined. The appearance of unusual Weiss oscillations in the bandwidth and density of states is the main focus of this work

  15. Electronic Structure of Au25 Clusters: Between Discrete and Continuous

    Katsiev, Khabiboulakh

    2016-07-15

    Here, an approach based on synchrotron resonant photoemission is emplyed to explore the transition between quantization and hybridization of the electronic structure in atomically precise ligand-stabilized nanoparticles. While the presence of ligands maintains quantization in Au25 clusters, their removal renders increased hybridization of the electronic states at the vicinity of the Fermi level. These observations are supported by DFT studies.

  16. Electronic Structure of Au25 Clusters: Between Discrete and Continuous

    Katsiev, Khabiboulakh; Lozova, Nataliya; Wang, Lu; Katla, Saikrishna; Li, Ruipeng; Mei, Wai Ning; Skrabalak, Sara; Challa, Challa; Losovyj, Yaroslav

    2016-01-01

    Here, an approach based on synchrotron resonant photoemission is emplyed to explore the transition between quantization and hybridization of the electronic structure in atomically precise ligand-stabilized nanoparticles. While the presence of ligands maintains quantization in Au25 clusters, their removal renders increased hybridization of the electronic states at the vicinity of the Fermi level. These observations are supported by DFT studies.

  17. Electronic Structure of Cdse Nanowires Terminated With Gold ...

    Bheema

    Owing to their unusual electronic and structural properties, SC clusters have received considerable attention ... performing molecular dynamics simulations. A similar .... Analysis of the charge density, gap, corresponding to states with energies ...

  18. Structures and electronics of buried and unburied semiconductor interfaces

    Kamiya, Itaru

    2011-01-01

    The structure of interfaces plays an important role in determining the electronic properties of semiconductor nanostructures. Here, such examples are shown and discussed using semiconductor nanostructures prepared by molecular beam epitaxy and colloidal synthesis.

  19. Manganites in Perovskite Superlattices: Structural and Electronic Properties

    Jiwuer, Jilili

    2016-01-01

    Perovskite manganites are widely investigated compounds due to the discovery of the colossal magnetoresistance effect in 1994. They have a broad range of structural, electronic, magnetic properties and potential device applications in sensors

  20. Structure and electron-ion correlation of liquid germanium

    Kawakita, Y. [Faculty of Sciences, Kyushu University, 4-2-1 Ropponmatsu, Fukuoka 810-8560 (Japan)]. E-mail: kawakita@rc.kyushu-u.ac.jp; Fujita, S. [Graduate School of Sciences, Kyushu University, 4-2-1 Ropponmatsu, Fukuoka 810-8560 (Japan); Kohara, S. [Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto Mikazuki-cho, Hyogo 679-5198 (Japan); Ohshima, K. [Graduate School of Sciences, Kyushu University, 4-2-1 Ropponmatsu, Fukuoka 810-8560 (Japan); Fujii, H. [Graduate School of Sciences, Kyushu University, 4-2-1 Ropponmatsu, Fukuoka 810-8560 (Japan); Yokota, Y. [Graduate School of Sciences, Kyushu University, 4-2-1 Ropponmatsu, Fukuoka 810-8560 (Japan); Takeda, S. [Faculty of Sciences, Kyushu University, 4-2-1 Ropponmatsu, Fukuoka 810-8560 (Japan)

    2005-08-15

    Structure factor of liquid germanium (Ge) has a shoulder at {theta} = 3.2 A{sup -1} in the high-momentum-transfer region of the first peak. To investigate the origin of such a non-simplicity in the structure, high energy X-ray diffraction measurements have been performed using 113.26 keV incident X-ray, at BL04B2 beamline of SPring-8. By a combination of the obtained structure factor with the reported neutron diffraction data, charge density function and electron-ion partial structure factor have been deduced. The peak position of the charge distribution is located at about 1 A, rather smaller r value than the half value of nearest neighbor distance ({approx}2.7 A), which suggests that valence electrons of liquid Ge play a role of screening electrons around a metallic ion rather than covalently bonding electrons.

  1. Structure functions in electron-nucleon deep inelastic scattering

    Saleem, M.; Fazal-E-Aleem (University of the Punjab, Lahore (Pakistan). Dept. of Physics)

    1982-06-26

    The phenomenological expressions for the structure functions in electron-nucleon deep inelastic scattering are proposed and are shown to satisfy the experimental data as well as a number of sum rules.

  2. First-principle calculations of structural, electronic, optical, elastic ...

    S CHEDDADI

    2017-11-28

    Nov 28, 2017 ... First-principle calculations on the structural, electronic, optical, elastic and thermal properties of the chalcopyrite ... The Kohn–Sham equations were solved using the ... RMTKmax = 7 was used for all the investigated systems,.

  3. Anomaly in the Kumakhov radiation temperature dependence at axial channeling of electrons

    Komarov, F.F.; Telegin, V.I.; Khokonov, M.Kh.

    1983-01-01

    The results of numerical solution of a kinetic equation for distribution function of axially channelled electrons obtained by Belostritsky and Kumakhov at different temperatures of crystals and calculated for the determined electron distributions spectral density of radiation are given. Analysis of the obtained dependence of the number of channelled 5 GeV electrons in tungsten along the <111> axis on depth Z has revealed that 2% of incidence beam electrons have anomalously large depths of dechannelling. Ratio of electrons with large by modulus cross section energies grows at decreasing crystal temperature from 293 to 40 K and, therefore, radiation intensity increases. Two-fold increase of radiation intensity can be attained at axial channelling of 1 GeV electrons in tungsten <111> at the temperatures of the crystal equal to 40 and 293 K and its thickness equal to 220 ..mu..m.

  4. Standalone, battery powered radiation monitors for accelerator electronics

    Wijnands, T; Spiezia, G

    2009-01-01

    A technical description of the design of a new type of radiation monitors is given. The key point in the design is the low power consumption inferior to 17 mW in radiation sensing mode and inferior to 0.3 mW in standby mode. The radiation monitors can operate without any external power or signal cabling and measure and store radiation data for a maximum period of 800 days. To read the radiation data, a standard PC can be connected via a USB interface to the device at any time. Only a few seconds are required to read out a single monitor. This makes it possible to survey a large network of monitoring devices in a short period of time, for example during a stop of the accelerator.

  5. Indirect radiation effects related to the environmental structure of targets

    Frankenberg, D.

    1976-01-01

    It is supposed, that in biological systems there are direct as well as indirect radiation effects. Their contributions to lethal effects depend mainly on two different kinds of structures within irradiated systems: the microscopic energy deposition patterns of radiation and the environmental structures of targets. The approach to determine these contributions of the lethal action of ionizing radiation in yeast cells was, to use chemical compounds, which specifically change the radical spectrum of water radiolysis. The efficiency of such chemical compounds in scavenging specifically water radicals was tested in aqueous solutions of thymine molecules, in which indirect radiation effects occur exclusively. The main result is, that the OH'-radical is by far the most effective radical to destroy thymine molecules. The relative contributions of direct and indirect radiation effects to lethal actions of ionizing radiation was investigated in yeast cells. The radical spectrum of water radiolysis was changed by bubbling the cell suspensions with different gases. The main result is, that there are no lethal radiation effects du to the action of water radicals

  6. An analysis of whistler mode radiation from a 100 mA electron beam

    Goerke, R.T.; Kellogg, P.J.; Monson, S.J.

    1990-01-01

    Observations of whistler mode radiation generated by 2-, 4-, and 8-keV electron beams with a current of 100 mA, are analyzed. The electron accelerator was carried to ionospheric heights by a Nike Black Brant V rocket (National Research Council of Canada NVB-06). The instability causing the whistler mode radiation is investigated. Spectral measurements (0.1-13.0 MHz), from a sweeping receiver located on the ejected forward payload, are used to determine the nature of the instability. The sweeping receiver was connected alternatively to an electric or a magnetic dipole antenna. Most of the whistler mode radiation detected was consistent with Cerenkov radiation. The radiation fields observed were too large (cB ∼ 0.1 μV/m Hz 1/2 ) to be explained by incoherent processes. If electrostatic bunching in the beam at the plasma frequency is responsible for the whistler radiation, there would be a correlation between the plasma frequency radiation, and the whistler mode radiation for electron beams that are fired toward the detector. The observed correlation is minimal. Hence no evidence was found to support the hypothesis that electrostatic bunching at the plasma frequency was responsible for the enhancement of the whistler mode radiation produced by the NVB-06 electron beam

  7. Electronic structure of incident carbon ions on a graphite surface

    Kiuchi, Masato; Takeuchi, Takae; Yamamoto, Masao.

    1997-01-01

    The electronic structure of an incident carbon ion on a graphite surface is discussed on the basis of ab initio molecular orbital calculations. A carbon cation forms a covalent bond with the graphite, and a carbon nonion is attracted to the graphite surface through van der Waals interaction. A carbon anion has no stable state on a graphite surface. The charge effects of incident ions become clear upon detailed examination of the electronic structure. (author)

  8. Changes in the chemical structure of polytetrafluoroethylene induced by electron beam irradiation in the molten state

    Lappan, U; Lunkwitz, K

    2000-01-01

    Polytetrafluoroethylene (PTFE) was exposed to electron beam radiation at elevated temperature above the melting point under nitrogen atmosphere and in vacuum for comparison. Fourier-transform infrared (FTIR) spectroscopy was used to study the changes in the chemical structure. The irradiation under nitrogen atmosphere leads to the same structures as described recently for PTFE irradiated in vacuum. Trifluoromethyl branches and double bond structures were detected. The concentrations of terminal and internal double bonds are higher after irradiation under nitrogen than in vacuum. Annealing experiments have shown that the thermal oxidative stability of the radiation-modified PTFE is reduced compared to unirradiated PTFE. The reason are the formation of unstable structures such as double bonds.

  9. Effect of high-energy radiation on the rheological characteristics and structure of liquid rubbers

    Govorkov, A.T.; Zaitseva, V.I.; Muryshkin, D.L.; Safonov, Yu.N.

    1987-01-01

    The effect of high-energy radiation (γ-radiation and accelerated electrons) on liquid polybutadiene and polyisoprene rubbers (SKD, SKD-KTR, SKN) and butyl rubber (BR) was studied by IR and EPR spectroscopy, rheoviscosimetry, and chemical analysis. Newtonian flow was conserved in the rubbers under irradiation. The activation energy of viscous flow was unchanged, evidence of an increase in the contour length of the macromolecules without significant branching and cross-linking at the initial stages of the irradiation. A quantitative relationship was established between the rubber's dynamic viscosity and the absorbed dose, and features of the structure-formation mechanism in the liquid rubbers were determined

  10. Dimensionality and its effects upon the valence electronic structure of ordered metallic systems

    Tobin, J.G.

    1983-07-01

    The system c(10x2)Ag/Cu(001) was investigated with Angle-Resolved Photoemission (ARP), Low Energy Electron Diffraction (LEED) and Auger Electron Spectroscopy (AES). LEED and AES provided the calibration of a quartz microbalance used to measure the amount of silver evaporated onto the copper single crystal and also established the monolayer geometrical structure at one monolayer exposure. An off-normal ARP bandmapping study performed with polarized HeI and NeI radiation demonstrated the electronically two-dimensional nature of the silver d-bands at coverages of near one monolayer. The states at the surface Brillouin Zone center were assigned upon the basis of their polarization dependences and a structural model of hexagonal symmetry. A normal emission ARP experiment was performed at the Stanford Synchrotron Radiation Laboratory (SSRL) over the photon energy range of 6 to 32 eV. Data from it documented the evolution of the valence electronic structure of the silver overlayer from a two-dimensional hexagonal valence to a three-dimensional behavior converging towards that of bulk Ag(111). A structural study was attempted using the ARP technique of Normal Emission Photoelectron Diffraction over the photon energy range of 3.4 to 3.7 keV at SSRL, the results of which are inconclusive

  11. Effect of radiation on microtubule structure in cancer cells

    Tripath, Shambhoo Sharan; Panda, Dulal; Jayakumar, S.; Maikho, Thoh; Sandur, Santosh Kumar

    2017-01-01

    Microtubules (MT) are dynamic structural cellular components. In proliferating cells, they are essential components in cell division through the formation of the mitotic spindle. Radiotherapy is an integral part of cancer treatment for most of the solid cancers. Scanty data exists in the literature related to how ionizing radiation affects microtubule reorganization in tumor cells. In the present study, breast cancer cell line (MCF-7 cells) was exposed to different doses of radiation (2-10Gy). Cells were cultured for 24 h, fixed and stained with antitubulin antibody and subjected to immunofluorescence microscopy. In another experiment, cells were subjected to cold treatment for 5 min or 30 min for studying the disassembly of microtubules after 24 h of irradiation. Further, these cells were incubated at 37°C for 20 min for studying the reassembly of microtubules. Acetylation of microtubule was also examined after exposure of cells to radiation. Experiments were also performed by combining radiation with low concentration of CXI-Benzo 84 (MT destabilizing agent 1 and 2.5 uM). Exposure of MCF-7 cells to radiation lead to destabilization of microtubules. Interestingly, destabilization of microtubule was faster upon cold treatment in irradiated group as compared to control group. These cells failed to re-stabilize at 37°C. Radiation also reduced the acetylation level of microtubule. Combination treatment of CXI-Benzo 84 with radiation exhibited additive effect in terms of depolymerization of MT. Our results suggest that ionizing radiation indeed modulates microtubule dynamics. (author)

  12. High-energy electron irradiation of NdFeB permanent magnets: Dependence of radiation damage on the electron energy

    Bizen, Teruhiko; Asano, Yoshihiro; Marechal, Xavier-Marie; Seike, Takamitsu; Aoki, Tsuyoshi; Fukami, Kenji; Hosoda, Naoyasu; Yonehara, Hiroto; Takagi, Tetsuya; Hara, Toru; Tanaka, Takashi; Kitamura, Hideo

    2007-01-01

    High-energy electron-beam bombardment of Nd 2 Fe 14 B-type permanent magnets induces radiation damage characterized by a drop in the magnetic field. Experiments carried out at the SPring-8 booster synchrotron, with 4, 6, and 8 GeV electrons, show that the drop in magnetic field is energy dependent. Electromagnetic shower simulations suggest that most of the radiation damage happens in a small region around the irradiation axis, and that the contribution of neutrons with large scattering angles or with low energies to the magnetic field change is small

  13. High-energy electron irradiation of NdFeB permanent magnets: Dependence of radiation damage on the electron energy

    Bizen, Teruhiko [JASRI SPring-8, 1-1-1 Kouto Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan)]. E-mail: bizen@spring8.or.jp; Asano, Yoshihiro [JASRI SPring-8, 1-1-1 Kouto Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); RIKEN SPring-8 Center, 1-1-1 Kouto Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); Marechal, Xavier-Marie [JASRI SPring-8, 1-1-1 Kouto Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Seike, Takamitsu [JASRI SPring-8, 1-1-1 Kouto Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Aoki, Tsuyoshi [JASRI SPring-8, 1-1-1 Kouto Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Fukami, Kenji [JASRI SPring-8, 1-1-1 Kouto Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Hosoda, Naoyasu [JASRI SPring-8, 1-1-1 Kouto Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Yonehara, Hiroto [JASRI SPring-8, 1-1-1 Kouto Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Takagi, Tetsuya [JASRI SPring-8, 1-1-1 Kouto Sayo-cho, Sayo-gun, Hyogo 679-5198 (Japan); Hara, Toru [RIKEN SPring-8 Center, 1-1-1 Kouto Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); Tanaka, Takashi [RIKEN SPring-8 Center, 1-1-1 Kouto Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan); Kitamura, Hideo [RIKEN SPring-8 Center, 1-1-1 Kouto Sayo-cho, Sayo-gun, Hyogo 679-5148 (Japan)

    2007-05-11

    High-energy electron-beam bombardment of Nd{sub 2}Fe{sub 14}B-type permanent magnets induces radiation damage characterized by a drop in the magnetic field. Experiments carried out at the SPring-8 booster synchrotron, with 4, 6, and 8 GeV electrons, show that the drop in magnetic field is energy dependent. Electromagnetic shower simulations suggest that most of the radiation damage happens in a small region around the irradiation axis, and that the contribution of neutrons with large scattering angles or with low energies to the magnetic field change is small.

  14. THz and Sub-THz Capabilities of a Table-Top Radiation Source Driven by an RF Thermionic Electron Gun

    Smirnov, Alexei V.; Agustsson, R.; Boucher, S.; Campese, Tara; Chen, Y.C.; Hartzell, Josiah J.; Jocobson, B.T.; Murokh, A.; O' Shea, F.H.; Spranza, E.; Berg, W.; Borland, M.; Dooling, J. C.; Erwin, L.; Lindberg, R. R.; Pasky, S.J.; Sereno, N.; Sun, Y.; Zholents, A.

    2017-06-01

    Design features and experimental results are presented for a sub-mm wave source [1] based on APS RF thermionic electron gun. The setup includes compact alpha-magnet, quadrupoles, sub-mm-wave radiators, and THz optics. The sub-THz radiator is a planar, oversized structure with gratings. Source upgrade for generation frequencies above 1 THz is discussed. The THz radiator will use a short-period undulator having 1 T field amplitude, ~20 cm length, and integrated with a low-loss oversized waveguide. Both radiators are integrated with a miniature horn antenna and a small ~90°-degree in-vacuum bending magnet. The electron beamline is designed to operate different modes including conversion to a flat beam interacting efficiently with the radiator. The source can be used for cancer diagnostics, surface defectoscopy, and non-destructive testing. Sub-THz experiment demonstrated a good potential of a robust, table-top system for generation of a narrow bandwidth THz radiation. This setup can be considered as a prototype of a compact, laser-free, flexible source capable of generation of long trains of Sub-THz and THz pulses with repetition rates not available with laser-driven sources.

  15. Nuclear resonant scattering of synchrotron radiation: Applications in magnetism of layered structures

    Schlage, Kai; Röhlsberger, Ralf

    2013-01-01

    Highlights: •Depth-resolved determination of magnetic spin structures. •Isotopic probe layers allow for probing selected depths in the sample. •High sensitivity to magnetic domain patterns via diffuse scattering. -- Abstract: Nuclear resonant scattering of synchrotron radiation has become an established tool within condensed-matter research. Synchrotron radiation with its outstanding brilliance, transverse coherence and polarization has opened this field for many unique studies, for fundamental research in the field of light-matter interaction as well as for materials science. This applies in particular for the electronic and magnetic structure of very small sample volumes like micro- and nano-structures and samples under extreme conditions of temperature and pressure. This article is devoted to the application of the technique to nanomagnetic systems such as thin films and multilayers. After a basic introduction into the method, a number of our experiments are presented to illustrate how magnetic spin structures within such layer systems can be revealed

  16. Terahertz Coherent Synchrotron Radiation from Femtosecond Laser Modulation of the Electron Beam at the Advanced Light Source

    Byrd, John; Martin, Michael C; Robin, David; Sannibale, Fernando; Schönlein, Robert W; Zholents, Alexander; Zolotorev, Max S

    2005-01-01

    At the Advanced Light Source (ALS), the "femtoslicing" beamline is in operation since 1999 for the production of x-ray synchrotron radiation pulses with femtosecond duration. The mechanism used for generating the short x-ray pulses induces at the same time temporary structures in the electron bunch longitudinal distribution with very short characteristic length. Such structures emit intense coherent synchrotron radiation (CSR) in the terahertz frequency range. This CSR, whose measured intensity is routinely used as a diagnostics for the tune-up of the femtoslicing experiments, represents a potential source of terahertz radiation with very interesting features. Several measurements have been performed for its characterization and in this paper an updated description of the experimental results and of their interpretation is presented.

  17. Radiation self-polarization of electrons moving in a magnetic field. [Vector spin operator, relaxation time

    Bagrov, V G; Dorofeev, O F; Sokolov, A A; Ternov, I M; Khalilov, V R [Moskovskij Gosudarstvennyj Univ. (USSR)

    1975-03-11

    When electrons move in a magnetic field, synchrotron radiation gives rise to transitions accompanied by the electron spin reorientation. In this case, it is essential that the transition probability depends on the spin orientation; as a result electron polarization takes place with the spin orientation being predominantly opposite to the direction of the magnetic field. This effect has been called ''radiative self-polarization of electrons''. The present work is concerned with the question how the choice of the spin operator will affect the self-polarization degree and relaxation time. The problem has been solved for a vector spin operator.

  18. Thermal electron acceleration by electric field spikes in the outer radiation belt: generation of field-aligned pitch angle distributions

    Vasko, I.; Agapitov, O. V.; Mozer, F.; Artemyev, A.

    2015-12-01

    Van Allen Probes observations in the outer radiation belt have demonstrated an abundance non-linear electrostatic stucture called Time Domain Structures (TDS). One of the type of TDS is electrostatic electron-acoustic double layers (DL). Observed DLs are frequently accompanied by field-aligned (bi-directional) pitch angle distributions (PAD) of electrons with energies from hundred eVs up to several keV (rarely up to tens of keV). We perform numerical simulations of the DL interaction with thermal electrons making use of the test particle approach. DL parameters assumed in the simulations are adopted from observations. We show that DLs accelerate thermal electrons parallel to the magnetic field via the electrostatic Fermi mechanism, i.e. due to reflections from DL potential humps. Due to this interaction some fraction of electrons is scattered into the loss cone. The electron energy gain is larger for larger DL scalar potential amplitudes and higher propagation velocities. In addition to the Fermi mechanism electrons can be trapped by DLs in their generation region and accelerated due to transport to higher latitudes. Both mechanisms result in formation of field-aligned PADs for electrons with energies comparable to those found in observations. The Fermi mechanism provides field-aligned PADs for <1 keV electrons, while the trapping mechanism extends field-aligned PADs to higher energy electrons.

  19. Electronic structure of UCl5: A reexamination

    Soule, E.; Edelstein, N.

    1980-01-01

    On the basis of the absorption spectrum of UCl 5 recorded at 4.2 K, Leung and Poon attempted a determination of both the spin-orbit coupling constant and the crystal field parameters. Their parameters, however, led to a calculated g-tensor at variance with the position of the electron paramagnetic resonance line observed by Miyake et al. It was therefore attempted to simultaneously interpret both spectra (absorption and EPR), assuming the validity of the Newman superposition model, and taking the point symmetry group on each uranium of the (UCl 5 ) 2 dimer as C 2 sub(v). We obtain one and only one satisfactory solution, namely a set of parameters that reasonably reproduce the observed absorption peaks, and lead to the following principal values of the g-tensor: gx = 0.226 (unobservable); gy = 1.187; gz = 1.186. Therefore the paradox stemming from the apparent isotropy of the EPR signal for a species of low point symmetry is resolved. (orig.)

  20. Electronic structure of metal overlayers on rhodium

    Feibelman, P.J.; Hamann, D.R.

    1983-01-01

    We have evaluated work functions, surface core-level shifts, and surface band dispersions for clean, Ag-covered, and Pd-covered Rh(100) surfaces, and for clean and Ag-covered Rh(111). The calculations were performed self-consistently, using the surface-linearized augmented-plane-wave method. As expected from the Pauling electronegativities, Ag adsorption lowers the work function from the clean Rh value, by several tenths of an eV, while Pd has an almost negligible effect. The values calculated for the core-level shifts of various films are shown to correspond to expectations based on surface band narrowing and layerwise charge neutrality. Using the core-level shifts, we predict heat-of-adsorption differences (for Ag on Pd vs Ag on Rh, etc.) that are in quite good agreement with the empirical predictions of Miedema and Dorleijn. Finally, the chemical inactivity of the Ag-covered Rh surface is associated with the fact that, for that system, the outer-layer local density of states is essentially that of Ag, with a characteristically low value at the Fermi energy. On the other hand, the Pd-covered Rh surface should behave much like clean Rh with an extra electron per surface atom. The surface band dispersions for the Pd-covered and clean Rh surfaces are closely similar. This result contrasts sharply with the case of Pd-covered Nb, for which, because of the appreciable electronegativity difference, the Pd overlayer is effectively ''noble.''