WorldWideScience

Sample records for beam focusing magnets

  1. Single-Plane Magnetically Focused Elongated Small Field Proton Beams.

    Science.gov (United States)

    McAuley, Grant A; Slater, James M; Wroe, Andrew J

    2015-08-01

    We previously performed Monte Carlo simulations of magnetically focused proton beams shaped by a single quadrapole magnet and thereby created narrow elongated beams with superior dose delivery characteristics (compared to collimated beams) suitable for targets of similar geometry. The present study seeks to experimentally validate these simulations using a focusing magnet consisting of 24 segments of samarium cobalt permanent magnetic material adhered into a hollow cylinder. Proton beams with properties relevant to clinical radiosurgery applications were delivered through the magnet to a water tank containing a diode detector or radiochromic film. Dose profiles were analyzed and compared with analogous Monte Carlo simulations. The focused beams produced elongated beam spots with high elliptical symmetry, indicative of magnet quality. Experimental data showed good agreement with simulations, affirming the utility of Monte Carlo simulations as a tool to model the inherent complexity of a magnetic focusing system. Compared to target-matched unfocused simulations, focused beams showed larger peak to entrance ratios (26% to 38%) and focused simulations showed a two-fold increase in beam delivery efficiency. These advantages can be attributed to the magnetic acceleration of protons in the transverse plane that tends to counteract the particle outscatter that leads to degradation of peak to entrance performance in small field proton beams. Our results have important clinical implications and suggest rare earth focusing magnet assemblies are feasible and could reduce skin dose and beam number while delivering enhanced dose to narrow elongated targets (eg, in and around the spinal cord) in less time compared to collimated beams.

  2. Single-Plane Magnetically Focused Elongated Small Field Proton Beams.

    Science.gov (United States)

    McAuley, Grant A; Slater, James M; Wroe, Andrew J

    2015-08-01

    We previously performed Monte Carlo simulations of magnetically focused proton beams shaped by a single quadrapole magnet and thereby created narrow elongated beams with superior dose delivery characteristics (compared to collimated beams) suitable for targets of similar geometry. The present study seeks to experimentally validate these simulations using a focusing magnet consisting of 24 segments of samarium cobalt permanent magnetic material adhered into a hollow cylinder. Proton beams with properties relevant to clinical radiosurgery applications were delivered through the magnet to a water tank containing a diode detector or radiochromic film. Dose profiles were analyzed and compared with analogous Monte Carlo simulations. The focused beams produced elongated beam spots with high elliptical symmetry, indicative of magnet quality. Experimental data showed good agreement with simulations, affirming the utility of Monte Carlo simulations as a tool to model the inherent complexity of a magnetic focusing system. Compared to target-matched unfocused simulations, focused beams showed larger peak to entrance ratios (26% to 38%) and focused simulations showed a two-fold increase in beam delivery efficiency. These advantages can be attributed to the magnetic acceleration of protons in the transverse plane that tends to counteract the particle outscatter that leads to degradation of peak to entrance performance in small field proton beams. Our results have important clinical implications and suggest rare earth focusing magnet assemblies are feasible and could reduce skin dose and beam number while delivering enhanced dose to narrow elongated targets (eg, in and around the spinal cord) in less time compared to collimated beams. PMID:25414143

  3. Focused electron beam induced deposition of magnetic nanostructures

    Science.gov (United States)

    de Teresa, Jose M.

    2011-03-01

    Nanopatterning strategies of magnetic materials normally rely on standard techniques such as electron-beam lithography using electron-sensitive resists. Focused electron beam induced deposition (FEBID) is currently being investigated as an alternative single-step route to produce functional magnetic nanostructures. Thus, Co-based and Fe-based precursors have been recently investigated for the growth of magnetic nanostructures by FEBID. In the present contribution, I will give an overview of the existing literature on magnetic nanostructures by FEBID and I will focus on the growth of Co nanostructures by FEBID using Co 2 (CO)8 as precursor gas. The Co content in the nanostructures can reach 95%. Magnetotransport experiments indicate that full metallic behaviour is displayed with relatively low residual resistivity and standard anisotropic magnetoresistance (0.8%). The coercive field of nanowires with changing aspect ratio has been determined in nanowires with width down to 150 nm by means of Magneto-optical Kerr Effect and the magnetization reversal has been imaged by means of Magnetic Force Microscopy, Scanning Transmission X-ray Microscopy as well as Lorentz Microscopy experiments. Nano-Hall probes have been grown with remarkable minimum detectable magnetic flux. Noticeably, it has been found that the domain-wall propagation field is lower than the domain-wall nucleation field in L-shaped nanowires, with potential applications in magnetic logic, sensing and storage. The spin polarization of these Co nanodeposits has been determined through Andreev-Reflection experiments in ferromagnetic-superconducting nanocontacts and amounts to 35%. Recent results obtained in Fe-based nanostructures by FEBID using Fe 2 (CO)9 precursor will be also presented. I acknowledge the collaboration in this field with A. Fernandez-Pacheco, R. Cordoba, L. Serrano, S. Sangiao, L.A. Rodriguez, C. Magen, E. Snoeck, L. Morellon, M.R. Ibarra.

  4. Understanding the focusing of charged particle for 2D sheet beam in a cusped magnetic field

    CERN Document Server

    Banerjee, Tusharika S; Reddy, K T V

    2016-01-01

    The requirement of axial magnetic field for focusing and transportation of sheet beam using cusped magnets is less as compared to solenoid magnetic fields which is uniform. There is often some confusion about how a cusped magnetic field focuses high current density sheet beam because it is generally understood that non-uniform magnetic field cannot guide the particle beam along its axis of propagation .In this paper, we perform simple analysis of the dynamics of sheet beam in a cusped magnetic field with single electron model and emphasize an intuitive understanding of interesting features (as beam geometry, positioning of permanent magnets, particle radius,particle velocity,radius of curvature of particle inside cusped magnetic field)

  5. Design, simulation and construction of quadrupole magnets for focusing electron beam in powerful industrial electron accelerator

    Directory of Open Access Journals (Sweden)

    S KH Mousavi

    2015-09-01

    Full Text Available In this paper the design and simulation of quadrupole magnets and electron beam optical of that by CST Studio code has been studied. Based on simulation result the magnetic quadrupole has been done for using in beam line of first Iranian powerful electron accelerator. For making the suitable magnetic field the effects of material and core geometry and coils current variation on quadrupole magnetic field have been studied. For test of quadrupole magnet the 10 MeV beam energy and 0.5 pi mm mrad emittance of input beam has been considered. We see the electron beam through the quadrupole magnet focus in one side and defocus in other side. The optimum of distance between two quadrupole magnets for low emittance have been achieved. The simulation results have good agreement with experimental results

  6. Electron beam focusing system

    Energy Technology Data Exchange (ETDEWEB)

    Dikansky, N.; Nagaitsev, S.; Parkhomchuk, V.

    1997-09-01

    The high energy electron cooling requires a very cold electron beam. Thus, the electron beam focusing system is very important for the performance of electron cooling. A system with and without longitudinal magnetic field is presented for discussion. Interaction of electron beam with the vacuum chamber as well as with the background ions and stored antiprotons can cause the coherent electron beam instabilities. Focusing system requirements needed to suppress these instabilities are presented.

  7. Characteristics for beam focusing of a magnetically insulated diode with a toroidal magnetic field (TMID)

    International Nuclear Information System (INIS)

    For the purpose of focusing intense pulsed ion beams, an ion diode insulated for electrons with a toroidal magnetic field (TMID) has been designed and tested as a preliminary experiment. The annular diode assembly is contained in the toroidal field produced with a toroidal coil. The diode power was supplied from a pulsed power supply ''ERIDATRON-II'' at a stored energy of 5kJ. Ion beams of 10 - 20kA with energies of 250 - 350 keV have been produced with an efficiency of about 10 %. It is suggested from observations of circulating current around the anode in nearly E x B direction, that the diode efficiency will be enhanced by increasing the toroidal field strength much above the critical magnetic field for insulation. The measured ion orbits agree well with the calculated single-particle ion orbits in this field even when the conditions for cross-field propagation are satisfied. The toroidal field was found to act as a magnetic lens as well as the insulating field for electrons in the diode. The features of the TMID appear to be very useful for obtaining a well focused ion beam in a simple device. (author)

  8. Performance Evaluation of Klystron Beam Focusing System with Anisotropic Ferrite Magnet

    CERN Document Server

    Fuwa, Yasuhiro

    2016-01-01

    A klystron beam focusing system using permanent magnets, which increases reliability in comparison with electromagnet focusing system, is reported. A prototype model has been designed and fabricated for a 1.3 GHz, 800 kW klystron for evaluation of the feasibility of the focusing system with permanent magnets. In order to decrease the production cost and to mitigate complex tuning processes of the magnetic field, anisotropic ferrite magnet is adopted as the magnetic material. As the result of a power test, 798 kW peak output power was successfully achieved with the prototype focusing system. Considering a power consumption of the electromagnet focusing system, the required wall-plug power to produce nominal 800 kW output power with the permanent magnet system is less than that with electromagnet. However, the power conversion efficiency of the klystron with the permanent magnet system was found to be limited by transverse multipole magnetic fields. By decreasing transverse multipole magnetic field components, ...

  9. Magnetic focusing of cold atomic beam with a 2D array of current-carrying wires

    Institute of Scientific and Technical Information of China (English)

    Yang Liu; Min Yun; Jianping Yin

    2006-01-01

    @@ A new scheme to realize a two-dimensional (2D) array of magnetic micro-lenses for a cold atomic beam,formed by an array of square current-carrying wires,is proposed.We calculate the spatial distributions of the magnetic fields from the array of current-carrying wires and the magnetic focusing potential for cold rubidium atoms,and study the dynamic focusing processes of cold atoms passing through the magnetic micro-lens array and its focusing properties by using Monte-Carlo simulations and trajectory tracing method.The result shows that the proposed micro-lens array can be used to focus effectively a cold atomic beam,even to load ultracold atoms or a BEC sample into a 2D optical lattice formed by blue detuned hollow beams.

  10. Space-charge limiting currents for magnetically focused intense relativistic electron beams

    Institute of Scientific and Technical Information of China (English)

    Li Jian-Qing; Mo Yuan-Long

    2007-01-01

    The self-consistent differential equations, which describe a laminar-flow equilibrium state in a magnetically focused intense relativistic electron beam propagating inside a conducting waveguide, are presented. The canonical angular momentum, Pθ, defined under the conditions at the source, uniquely determines the possible solutions of these equations.By numerically solving these equations, the space-charge limited current and the externally applied magnetic field are obtained in a solid beam and a hollow beam in two cases of Pθ = 0 (magnetically shielded source) and Pθ = const.(immersed source) separately. It is shown that the hollow beam is more beneficial to the propagation of the intense relativistic beam through a drift tube than the solid beam.

  11. Probing the magnetic moment of FePt micromagnets prepared by focused ion beam milling

    NARCIS (Netherlands)

    Overweg, H.C.; Den Haan, A.M.J.; Eerkens, H.J.; Alkemade, P.F.A.; La Rooij, A.L.; Spreeuw, R.J.C.; Bossoni, L.; Oosterkamp, T.H.

    2015-01-01

    We investigate the degradation of the magnetic moment of a 300 nm thick FePt film induced by Focused Ion Beam (FIB) milling. A 1 μm × 8 μm rod is milled out of a film by a FIB process and is attached to a cantilever by electron beam induced deposition. Its magnetic moment is determined by frequency-

  12. Terahertz generation by two cross focused Gaussian laser beams in magnetized plasma

    International Nuclear Information System (INIS)

    This paper presents a theoretical model for terahertz (THz) radiation generation by two cross-focused Gaussian laser beams in a collisionless magnetoplasma. The plasma is redistributed due to the ponderomotive nonlinearity which leads to the cross focusing of the laser beams. The focusing of the copropagating laser beams increases with increasing the externally applied static magnetic field which is perpendicular to the wave propagation direction. The nonlinear current at THz frequency arises on account of nonlinear ponderomotive force as a result of beating of the two lasers. The generated THz radiation amplitude increases significantly with increasing magnetic field. The cross focusing of two laser beams enhances the THz yield. Optimization of laser-plasma parameters gives the radiated normalized THz power of the order of 10 kW

  13. Probing the magnetic moment of FePt micromagnets prepared by focused ion beam milling

    Energy Technology Data Exchange (ETDEWEB)

    Overweg, H. C.; Haan, A. M. J. den; Eerkens, H. J.; Bossoni, L.; Oosterkamp, T. H., E-mail: oosterkamp@physics.leidenuniv.nl [Huygens-Kamerlingh Onnes Laboratory, Leiden University, Niels Bohrweg 2, 2333CA Leiden (Netherlands); Alkemade, P. F. A. [Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft (Netherlands); La Rooij, A. L.; Spreeuw, R. J. C. [Van der Waals-Zeeman Institute, University of Amsterdam, Science Park 904, 1090 GL Amsterdam (Netherlands)

    2015-08-17

    We investigate the degradation of the magnetic moment of a 300 nm thick FePt film induced by Focused Ion Beam (FIB) milling. A 1 μm × 8 μm rod is milled out of a film by a FIB process and is attached to a cantilever by electron beam induced deposition. Its magnetic moment is determined by frequency-shift cantilever magnetometry. We find that the magnetic moment of the rod is μ = 1.1 ± 0.1 × 10{sup −12} Am{sup 2}, which implies that 70% of the magnetic moment is preserved during the FIB milling process. This result has important implications for atom trapping and magnetic resonance force microscopy, which are addressed in this paper.

  14. Focused Azimuthally E-Polarized Vector Beam and Spatial Magnetic Resolution below the Diffraction Limit

    CERN Document Server

    Veysi, Mehdi; Capolino, Filippo

    2016-01-01

    An azimuthally E-polarized vector beam (AEVB) has a salient feature that it contains a magnetic-dominant region within which electric field has a null and longitudinal magnetic field is maximum. Fresnel diffraction theory and plane-wave spectral (PWS) calculations are applied to quantify the field features of such a beam upon focusing through a lens. The diffraction-limited full width at half maximum (FWHM) of the beams longitudinal magnetic field intensity profile and complementary FWHM (CFWHM) of the beam's annular-shaped total electric field intensity profile are calculated at the lens's focal plane as a function of the lens's paraxial focal distance. Subsequently, we demonstrate, for the first time, that a very high resolution magnetic field at optical frequency with the total magnetic field FWHM of 0.23{\\lambda}(magnetic field spot size of 0.04{\\lambda}^2) can be achieved by placing a subwavelength dense dielectric Mie scatterer in the minimum-waist plane of a self-standing converging AEVB. The theory sh...

  15. A compact broadband ion beam focusing device based on laser-driven megagauss thermoelectric magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Albertazzi, B., E-mail: bruno.albertazzi@polytechnique.edu [LULI, École Polytechnique, CNRS, CEA, UPMC, 91128 Palaiseau (France); INRS-EMT, Varennes, Québec J3X 1S2 (Canada); Graduate School of Engineering, Osaka University, Suita, Osaka 565-087 (Japan); D' Humières, E. [CELIA, Universite de Bordeaux, Talence 33405 (France); Department of Physics, University of Nevada, Reno, Nevada 89557 (United States); Lancia, L.; Antici, P. [Dipartimento SBAI, Universita di Roma “La Sapienza,” Via A. Scarpa 16, 00161 Roma (Italy); Dervieux, V.; Nakatsutsumi, M.; Romagnani, L.; Fuchs, J., E-mail: Julien.fuchs@polytechnique.fr [LULI, École Polytechnique, CNRS, CEA, UPMC, 91128 Palaiseau (France); Böcker, J.; Swantusch, M.; Willi, O. [Institut für Laser- und Plasmaphysik, Heinrich-Heine-Universität, Düsseldorf D-40225 (Germany); Bonlie, J.; Cauble, B.; Shepherd, R. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Breil, J.; Feugeas, J. L.; Nicolaï, P.; Tikhonchuk, V. T. [CELIA, Universite de Bordeaux, Talence 33405 (France); Chen, S. N. [LULI, École Polytechnique, CNRS, CEA, UPMC, 91128 Palaiseau (France); Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Sentoku, Y. [Department of Physics, University of Nevada, Reno, Nevada 89557 (United States); and others

    2015-04-15

    Ultra-intense lasers can nowadays routinely accelerate kiloampere ion beams. These unique sources of particle beams could impact many societal (e.g., proton-therapy or fuel recycling) and fundamental (e.g., neutron probing) domains. However, this requires overcoming the beam angular divergence at the source. This has been attempted, either with large-scale conventional setups or with compact plasma techniques that however have the restriction of short (<1 mm) focusing distances or a chromatic behavior. Here, we show that exploiting laser-triggered, long-lasting (>50 ps), thermoelectric multi-megagauss surface magnetic (B)-fields, compact capturing, and focusing of a diverging laser-driven multi-MeV ion beam can be achieved over a wide range of ion energies in the limit of a 5° acceptance angle.

  16. Review of magnetic nanostructures grown by focused electron beam induced deposition (FEBID)

    Science.gov (United States)

    De Teresa, J. M.; Fernández-Pacheco, A.; Córdoba, R.; Serrano-Ramón, L.; Sangiao, S.; Ibarra, M. R.

    2016-06-01

    We review the current status of the use of focused electron beam induced deposition (FEBID) for the growth of magnetic nanostructures. This technique relies on the local dissociation of a precursor gas by means of an electron beam. The most promising results have been obtained using the Co2(CO)8 precursor, where the Co content in the grown nanodeposited material can be tailored up to more than 95 at.%. Functional behaviour of these Co nanodeposits has been observed in applications such as arrays of magnetic dots for information storage and catalytic growth, magnetic tips for scanning probe microscopes, nano-Hall sensors for bead detection, nano-actuated magnetomechanical systems and nanowires for domain-wall manipulation. The review also covers interesting results observed in Fe-based and alloyed nanodeposits. Advantages and disadvantages of FEBID for the growth of magnetic nanostructures are discussed in the article as well as possible future directions in this field.

  17. Generation of a focused proton beam with a self-magnetically BΘ-insulated ion diode

    International Nuclear Information System (INIS)

    A self-magnetically BΘ -insulated ion diode was investigated and optimized at the pulsed power line KALIF (2 MV, 50 ns, 2 Ω) to produce a focused and pulsed high-intensity proton beam for generation of high-power density in matter. This diode is characterized by an azimuthal insulating magnetic field that is generated by the diode current. The beam is neutralized by electrons from the cathode vanes, so that neither a gas filled drift space nor foils are needed. The beam therefore propagates in vacuum and repeated shots are possible without changing parts. The protons had energies up to 1.8 MeV and the proton content in the ion beam was about 50%. The maximum total diode current was about 800 kA and its efficiency was as high as 70%. The beam microdivergence was determined to be 1.1 degree. The radial dependence of the proton current density was measured and is proportional to r-1.74. This result was confirmed by 2D quasistatic particle-in-cell simulations. The focus was optimized by adjusting the anode shape and the gap geometry and by decreasing the beam divergence. The FWHM diameter of the focus at a distance of 300 mm was about 10 mm and the resulting focused power density was 0.13 TW/cm2. The effect of the gap distance on focusing and impedance was investigated and it was found necessary to adjust the gap to better than 0.1 mm over the total 30-cm-diam anode to obtain the best performance. The electron loss and the corresponding erosion at the posts that hold the anode was reduced. The lifetime is now limited by the plastic anode insert to 10--15 pulses. Based on these results a ''small BΘ diode'' is suggested for which a power density increase of a factor of 3 is estimated

  18. Pulsed neutron-beam focusing by modulating a permanent-magnet sextupole lens

    Science.gov (United States)

    Yamada, Masako; Iwashita, Yoshihisa; Ichikawa, Masahiro; Fuwa, Yasuhiro; Tongu, Hiromu; Shimizu, Hirohiko M.; Mishima, Kenji; Yamada, Norifumi L.; Hirota, Katsuya; Otake, Yoshie; Seki, Yoshichika; Yamagata, Yutaka; Hino, Masahiro; Kitaguchi, Masaaki; Garbe, Ulf; Kennedy, Shane J.; Tung Lee, Wai; Andersen, Ken H.; Guerard, Bruno; Manzin, Giuliana; Geltenbort, Peter

    2015-04-01

    We have developed a compact permanent-magnet sextupole lens for neutrons that can focus a pulsed beam with a wide wavelength range-the maximum wavelength being more than double the minimum-while sufficiently suppressing the effect of chromatic aberration. The bore diameter is #x00F8;15 mm. Three units of a double-ring sextupole with a length of 66 mm are cascaded, resulting in a total length of 198 mm. The dynamic modulation range of the unit-averaged field gradient is 1.06 × 104-5.86 × 104Tm^{-2}. Permanent magnets and newly developed torque-canceling elements make the device compact, its production costs low, and its operation simpler than that of other magnetic lenses. The efficacy of this lens was verified using very cold neutrons. The diameter of the focused beam spots over the wavelength range of 27-55 Å was the same as that of the source aperture (2 mm diameter) when the magnification of the optical arrangement was unity. The total beam flux over this wavelength range was enhanced by a factor of 43. The focusing distance from the source to the detector was 1.84 m. In addition, in a demonstration of neutron image magnification, the image of a sample mask magnified by a factor of 4.1 was observed when the magnification of the optical arrangement was 5.0.

  19. H-mode accelerating structures with permanent-magnet quadrupole beam focusing

    Science.gov (United States)

    Kurennoy, S. S.; Rybarcyk, L. J.; O'Hara, J. F.; Olivas, E. R.; Wangler, T. P.

    2012-09-01

    We have developed high-efficiency normal-conducting rf accelerating structures by combining H-mode resonator cavities and a transverse beam focusing by permanent-magnet quadrupoles (PMQ), for beam velocities in the range of a few percent of the speed of light. The shunt impedance of interdigital H-mode (IH-PMQ) structures is 10-20 times higher than that of a conventional drift-tube linac, while the transverse size is 4-5 times smaller. Results of the combined 3D modeling—electromagnetic computations, multiparticle beam-dynamics simulations with high currents, and thermal-stress analysis—for an IH-PMQ accelerator tank are presented. The accelerating-field profile in the tank is tuned to provide the best propagation of a 50-mA deuteron beam using coupled iterations of electromagnetic and beam-dynamics modeling. Measurements of a cold model of the IH-PMQ tank show a good agreement with the calculations. Examples of cross-bar H-mode structures with PMQ focusing for higher beam velocities are also presented. H-PMQ accelerating structures following a short radio-frequency quadrupole accelerator can be used both in the front end of ion linacs or in stand-alone applications.

  20. Producion of intense focused ion beams in a spherical magnetically insulated diode

    International Nuclear Information System (INIS)

    A magnetically insulated ion diode has been constructed with a spherically focusing geometry. The diode has been operated at voltages of approx.250 and approx.500 kV, with impedances adjusted to 2--3 and 7--10 Ω, respectively. The pulse length was approx.85 ns. Total ion currents were > or =30% of the diode current. In the high-voltage case, a focal current density of 2100 A/cm2 was obtained; this is > or approx. =90 times the anode ion current density. Auxilliary magnetic fields were used to steer the beam, with the beam deflection as calculated for a single proton. The diode design and diagnostic techniques are described, as well as possibilities for improvements suggested by our data

  1. Design, simulation and construction of quadrupole magnets for focusing electron beam in powerful industrial electron accelerator

    OpenAIRE

    S KH Mousavi; A M Poursaleh; S Haseltalab; M Mortazavi; A Behjat; Atefi, M.

    2015-01-01

    In this paper the design and simulation of quadrupole magnets and electron beam optical of that by CST Studio code has been studied. Based on simulation result the magnetic quadrupole has been done for using in beam line of first Iranian powerful electron accelerator. For making the suitable magnetic field the effects of material and core geometry and coils current variation on quadrupole magnetic field have been studied. For test of quadrupole magnet the 10 MeV beam energy and 0.5 pi mm...

  2. Envelope model for passive magnetic focusing of an intense proton or ion beam propagating through thin foils

    Science.gov (United States)

    Lund, Steven M.; Cohen, Ronald H.; Ni, Pavel A.

    2013-04-01

    Ion beams (including protons) with low emittance and high space-charge intensity can be propagated with normal incidence through a sequence of thin metallic foils separated by vacuum gaps of order the characteristic transverse beam extent to transport/collimate the beam or to focus it to a small transverse spot. Energetic ions have sufficient range to pass through a significant number of thin foils with little energy loss or scattering. The foils reduce the (defocusing) radial electric self-field of the beam while not altering the (focusing) azimuthal magnetic self-field of the beam, thereby allowing passive self-beam focusing if the magnetic field is sufficiently strong relative to the residual electric field. Here we present an envelope model developed to predict the strength of this passive (beam generated) focusing effect under a number of simplifying assumptions including relatively long pulse duration. The envelope model provides a simple criterion for the necessary foil spacing for net focusing and clearly illustrates system focusing properties for either beam collimation (such as injecting a laser-produced proton beam into an accelerator) or for magnetic pinch focusing to a small transverse spot (for beam driven heating of materials). An illustrative example is worked for an idealization of a recently performed laser-produced proton-beam experiment to provide guidance on possible beam focusing and collimation systems. It is found that foils spaced on the order of the characteristic transverse beam size desired can be employed and that envelope divergence of the initial beam entering the foil lens must be suppressed to limit the total number of foils required to practical values for pinch focusing. Relatively modest proton-beam current at 10 MeV kinetic energy can clearly demonstrate strong magnetic pinch focusing achieving a transverse rms extent similar to the foil spacing (20-50μm gaps) in beam propagation distances of tens of mm. This is a surprisingly

  3. Fe:O:C grown by focused-electron-beam-induced deposition: magnetic and electric properties

    Energy Technology Data Exchange (ETDEWEB)

    Lavrijsen, R; Schoenaker, F J; Ellis, T H; Barcones, B; Kohlhepp, J T; Swagten, H J M; Koopmans, B [Department of Applied Physics, Center for NanoMaterials and COBRA Research Institute, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven (Netherlands); Cordoba, R; Ibarra, M R [Instituto de Nanociencia de Aragon, Universidad de Zaragoza, E-50009 Zaragoza (Spain); De Teresa, J M; Magen, C [Departamento de Fisica de la Materia Condensada, Universidad de Zaragoza, E-50009 Zaragoza (Spain); Trompenaars, P; Mulders, J J L, E-mail: r.lavrijsen@tue.nl, E-mail: deteresa@unizar.es [FEI Electron Optics, Achtseweg Noord 5, 5651 GG Eindhoven (Netherlands)

    2011-01-14

    We systematically study the effect of oxygen content on the magneto-transport and microstructure of Fe:O:C nanowires deposited by focused-electron-beam-induced (FEBID) deposition. The Fe/O ratio can be varied with an Fe content varying between {approx} 50 and 80 at.% with overall low C content ({approx}16 {+-} 3 at.%) by adding H{sub 2}O during the deposition while keeping the beam parameters constant as measured by energy dispersive x-ray (EDX) spectroscopy. The room-temperature magnetic properties for deposits with an Fe content of 66-71 at.% are investigated using the magneto-optical Kerr effect (MOKE) and electric magneto-transport measurements. The nanostructure of the deposits is investigated through cross-sectional high-resolution transmission electron microscopy (HRTEM) imaging, allowing us to link the observed magneto-resistance and resistivity to the transport mechanism in the deposits. These results demonstrate that functional magnetic nanostructures can be created, paving the way for new magnetic or even spintronics devices.

  4. Focused neutral beams with low chaotic divergence for plasma heating and diagnostics in magnetic fusion devices

    International Nuclear Information System (INIS)

    A series of neutral beam injectors has been developed in the Budker Institute of Nuclear Physics for plasma heating and diagnostics in modern fusion devices. Ion optical system of these injectors is optimized to produce ion beams with low angular divergence. In order to provide beam focusing, the grids are formed to be spherical segments. Such geometrically focused neutral beams are particularly advantageous for plasma diagnostics when high spatial resolution is required. Another application of these beams is plasma heating in the machines with narrow ports through which only small size, high power density beams can be transported. (author)

  5. An adjustable focusing system for a 2 MeV H- ion beam line based on permanent magnet quadrupoles

    CERN Document Server

    Nirkko, M; Ereditato, A; Kreslo, I; Scampoli, P; Weber, M

    2012-01-01

    A compact adjustable focusing system for a 2 MeV H- RFQ Linac is designed, constructed and tested based on four permanent magnet quadrupoles (PMQ). A PMQ model is realised using finite element simulations, providing an integrated field gradient of 2.35 T with a maximal field gradient of 57 T/m. A prototype is constructed and the magnetic field is measured, demonstrating good agreement with the simulation. Particle track simulations provide initial values for the quadrupole positions. Accordingly, four PMQs are constructed and assembled on the beam line, their positions are then tuned to obtain a minimal beam spot size of (1.2 x 2.2) mm^2 on target. This paper describes an adjustable PMQ beam line for an external ion beam. The novel compact design based on commercially available NdFeB magnets allows high flexibility for ion beam applications.

  6. Self focusing of laser beams and its effect in the generation of magnetic field in laser-produced plasma

    International Nuclear Information System (INIS)

    The present work deals with the generation of magnetic field in a plasma due to self focusing effects of laser beam. Spontaneously generated magnetic fields of the order of several kilogauss have been investigated and the cause for the generation of B-field has been attributed to the time dependent ponderomotive force of a self focused inhomogeneous gaussian shaped laser beam. The magnitude of the magnetic field is found to increase with self focusing effect of the laser beam. It can be shown that for high-frequency laser (viz. Nd-glass laser having the wavelength (λ) = 1.06 μm and amplitude of E-field (E00) = 3.9 x 1011 V/m), the magnitude of B-field is found to be in better agreement with the experiment. B-field varies inversely with temperature which has not been taken care in earlier reports. (author)

  7. X-ray magnetic circular dichroism photoemission electron microscopy of focused ion beam-induced magnetic patterns on iron–rhodium surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Tohki, Atsushi; Aikoh, Kazuma; Shinoda, Ryoichi [Department of Materials Science, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531 (Japan); Ohkochi, Takuo [Japan Synchrotron Radiation Research Institute, SPring-8, Sayo, Hyogo 679-5198 (Japan); Kotsugi, Masato [Japan Synchrotron Radiation Research Institute, SPring-8, Sayo, Hyogo 679-5198 (Japan); CREST-JST, Kawaguchi, Saitama 332-0012 (Japan); Nakamura, Tetsuya [Japan Synchrotron Radiation Research Institute, SPring-8, Sayo, Hyogo 679-5198 (Japan); Kinoshita, Toyohiko [Japan Synchrotron Radiation Research Institute, SPring-8, Sayo, Hyogo 679-5198 (Japan); CREST-JST, Kawaguchi, Saitama 332-0012 (Japan); Iwase, Akihiro [Department of Materials Science, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531 (Japan); Matsui, Toshiyuki, E-mail: t-matsui@21c.osakafu-u.ac.jp [Research Organization for the 21st Century, Osaka Prefecture University, 1-1 Gakuen-cho, Sakai, Osaka 599-8531 (Japan)

    2013-05-01

    Iron–rhodium (FeRh) thin films were irradiated with a 30 keV Ga ion beam using a focused ion beam system to produce micrometer scale ferromagnetic square dot arrays. Two-dimensional magnetic square dot arrays with dimensions of 30 × 30, 10 × 10, and 5 × 5 μm were successfully produced on the FeRh surface, which was confirmed by magnetic force microscopy. The results of photoemission electron microscopy combined with X-ray magnetic circular dichroism revealed that the magnetization of the magnetic square dots could be controlled by changing the amount of irradiation. The magnetic domain structure of the magnetic square dots with sides of 5–30 μm was found to be a single domain structure, which was possibly influenced by the interaction between ferromagnetic and antiferromagnetic interfaces.

  8. X-ray magnetic circular dichroism photoemission electron microscopy of focused ion beam-induced magnetic patterns on iron-rhodium surfaces

    Science.gov (United States)

    Tohki, Atsushi; Aikoh, Kazuma; Shinoda, Ryoichi; Ohkochi, Takuo; Kotsugi, Masato; Nakamura, Tetsuya; Kinoshita, Toyohiko; Iwase, Akihiro; Matsui, Toshiyuki

    2013-05-01

    Iron-rhodium (FeRh) thin films were irradiated with a 30 keV Ga ion beam using a focused ion beam system to produce micrometer scale ferromagnetic square dot arrays. Two-dimensional magnetic square dot arrays with dimensions of 30 × 30, 10 × 10, and 5 × 5 μm were successfully produced on the FeRh surface, which was confirmed by magnetic force microscopy. The results of photoemission electron microscopy combined with X-ray magnetic circular dichroism revealed that the magnetization of the magnetic square dots could be controlled by changing the amount of irradiation. The magnetic domain structure of the magnetic square dots with sides of 5-30 μm was found to be a single domain structure, which was possibly influenced by the interaction between ferromagnetic and antiferromagnetic interfaces.

  9. Magnetic focusing of an intense slow positron beam for enhanced depth-resolved analysis of thin films and interfaces

    CERN Document Server

    Falub, C V; Mijnarends, P E; Schut, H; Veen, A V

    2002-01-01

    The intense reactor-based slow positron beam (POSH) at the Delft research reactor has been coupled to a Two-Dimensional Angular Correlation of Annihilation Radiation (2D-ACAR) setup. The design is discussed with a new target chamber for the 2D-ACAR setup based on Monte Carlo simulations of the positron trajectories, beam energy distribution and beam transmission in an increasing magnetic field gradient. Numerical simulations and experiment show that when the slow positron beam with a FWHM of 11.6 mm travels in an increasing axial magnetic field created by a strong NdFeB permanent magnet, the intensity loss is negligible above approx 6 keV and a focusing factor of 5 in diameter is achieved. Monte Carlo simulations and Doppler broadening experiments in the target region show that in this configuration the 2D-ACAR setup can be used to perform depth sensitive studies of defects in thin films with a high resolution. The positron implantation energy can be varied from 0 to 25 keV before entering the non-uniform mag...

  10. Laser Beam Focus Analyser

    DEFF Research Database (Denmark)

    Nielsen, Peter Carøe; Hansen, Hans Nørgaard; Olsen, Flemming Ove;

    2007-01-01

    The quantitative and qualitative description of laser beam characteristics is important for process implementation and optimisation. In particular, a need for quantitative characterisation of beam diameter was identified when using fibre lasers for micro manufacturing. Here the beam diameter limits...... the obtainable features in direct laser machining as well as heat affected zones in welding processes. This paper describes the development of a measuring unit capable of analysing beam shape and diameter of lasers to be used in manufacturing processes. The analyser is based on the principle of a rotating...... mechanical wire being swept through the laser beam at varying Z-heights. The reflected signal is analysed and the resulting beam profile determined. The development comprised the design of a flexible fixture capable of providing both rotation and Z-axis movement, control software including data capture...

  11. Compact electron beam focusing column

    Energy Technology Data Exchange (ETDEWEB)

    Persaud, Arun; Leung, Ka-Ngo; Reijonen, Jani

    2001-07-13

    A novel design for an electron beam focusing column has been developed at LBNL. The design is based on a low-energy spread multicusp plasma source which is used as a cathode for electron beam production. The focusing column is 10 mm in length. The electron beam is focused by means of electrostatic fields. The column is designed for a maximum voltage of 50 kV. Simulations of the electron trajectories have been performed by using the 2-D simulation code IGUN and EGUN. The electron temperature has also been incorporated into the simulations. The electron beam simulations, column design and fabrication will be discussed in this presentation.

  12. Stability of an emittance-dominated sheet-electron beam in planar wiggler and periodic permanent magnet structures with natural focusing

    Science.gov (United States)

    Carlsten, B. E.; Earley, L. M.; Krawczyk, F. L.; Russell, S. J.; Potter, J. M.; Ferguson, P.; Humphries, S.

    2005-06-01

    A sheet-beam traveling-wave amplifier has been proposed as a high-power generator of rf from 95 to 300 GHz, using a microfabricated rf slow-wave structure [Carlsten et al., IEEE Trans. Plasma Sci. 33, 85 (2005), ITPSBD, 0093-3813, 10.1109/TPS.2004.841172], for emerging radar and communications applications. The planar geometry of microfabrication technologies matches well with the nearly planar geometry of a sheet beam, and the greater allowable beam current leads to high-peak power, high-average power, and wide bandwidths. Simulations of nominal designs using a vane-loaded waveguide as the slow-wave structure have indicated gains in excess of 1 dB/mm, with extraction efficiencies greater than 20% at 95 GHz with a 120-kV, 20-A electron beam. We have identified stable sheet-beam formation and transport as the key enabling technology for this type of device. In this paper, we describe sheet-beam transport, for both wiggler and periodic permanent magnet (PPM) magnetic field configurations, with natural (or single-plane) focusing. For emittance-dominated transport, the transverse equation of motion reduces to a Mathieu equation, and to a modified Mathieu equation for a space-charge dominated beam. The space-charge dominated beam has less beam envelope ripple than an emittance-dominated beam, but they have similar stability thresholds (defined by where the beam ripple continues to grow without bound along the transport line), consistent with the threshold predicted by the Mathieu equation. Design limits are derived for an emittance-dominated beam based on the Mathieu stability threshold. The increased beam envelope ripple for emittance-dominated transport may impact these design limits, for some transport requirements. The stability of transport in a wiggler field is additionally compromised by the beam’s increased transverse motion. Stable sheet-beam transport with natural focusing is shown to be achievable for a 120-kV, 20-A, elliptical beam with a cross section of

  13. On the magnetic properties of iron nanostructures fabricated via focused electron beam induced deposition and autocatalytic growth processes.

    Science.gov (United States)

    Tu, F; Drost, M; Vollnhals, F; Späth, A; Carrasco, E; Fink, R H; Marbach, H

    2016-09-01

    We employ Electron beam induced deposition (EBID) in combination with autocatalytic growth (AG) processes to fabricate magnetic nanostructures with controllable shapes and thicknesses. Following this route, different Fe deposits were prepared on silicon nitride membranes under ultra-high vacuum conditions and studied by scanning electron microscopy (SEM) and scanning transmission x-ray microspectroscopy (STXM). The originally deposited Fe nanostructures are composed of pure iron, especially when fabricated via autocatalytic growth processes. Quantitative near-edge x-ray absorption fine structure (NEXAFS) spectroscopy was employed to derive information on the thickness dependent composition. X-ray magnetic circular dichroism (XMCD) in STXM was used to derive the magnetic properties of the EBID prepared structures. STXM and XMCD analysis evinces the existence of a thin iron oxide layer at the deposit-vacuum interface, which is formed during exposure to ambient conditions. We were able to extract magnetic hysteresis loops for individual deposits from XMCD micrographs with varying external magnetic field. Within the investigated thickness range (2-16 nm), the magnetic coercivity, as evaluated from the width of the hysteresis loops, increases with deposit thickness and reaches a maximum value of ∼160 Oe at around 10 nm. In summary, we present a viable technique to fabricate ferromagnetic nanostructures in a controllable way and gain detailed insight into their chemical and magnetic properties. PMID:27454990

  14. On the magnetic properties of iron nanostructures fabricated via focused electron beam induced deposition and autocatalytic growth processes

    Science.gov (United States)

    Tu, F.; Drost, M.; Vollnhals, F.; Späth, A.; Carrasco, E.; Fink, R. H.; Marbach, H.

    2016-09-01

    We employ Electron beam induced deposition (EBID) in combination with autocatalytic growth (AG) processes to fabricate magnetic nanostructures with controllable shapes and thicknesses. Following this route, different Fe deposits were prepared on silicon nitride membranes under ultra-high vacuum conditions and studied by scanning electron microscopy (SEM) and scanning transmission x-ray microspectroscopy (STXM). The originally deposited Fe nanostructures are composed of pure iron, especially when fabricated via autocatalytic growth processes. Quantitative near-edge x-ray absorption fine structure (NEXAFS) spectroscopy was employed to derive information on the thickness dependent composition. X-ray magnetic circular dichroism (XMCD) in STXM was used to derive the magnetic properties of the EBID prepared structures. STXM and XMCD analysis evinces the existence of a thin iron oxide layer at the deposit-vacuum interface, which is formed during exposure to ambient conditions. We were able to extract magnetic hysteresis loops for individual deposits from XMCD micrographs with varying external magnetic field. Within the investigated thickness range (2-16 nm), the magnetic coercivity, as evaluated from the width of the hysteresis loops, increases with deposit thickness and reaches a maximum value of ˜160 Oe at around 10 nm. In summary, we present a viable technique to fabricate ferromagnetic nanostructures in a controllable way and gain detailed insight into their chemical and magnetic properties.

  15. Self-focusing and defocusing of Gaussian laser beams in collisional underdense magnetized plasmas with considering the nonlinear ohmic heating and ponderomotive force effects

    Energy Technology Data Exchange (ETDEWEB)

    Ettehadi Abari, Mehdi; Sedaghat, Mahsa; Shokri, Babak, E-mail: b-shokri@sbu.ac.ir [Physics Department and Laser-Plasma Research Institute of Shahid Beheshti University, G.C., 19839 Evin, Tehran (Iran, Islamic Republic of)

    2015-10-15

    The propagation characteristics of a Gaussian laser beam in collisional magnetized plasma are investigated by considering the ponderomotive and ohmic heating nonlinearities. Here, by taking into account the effect of the external magnetic field, the second order differential equation of the dimensionless beam width parameter is solved numerically. Furthermore, the nonlinear dielectric permittivity of the mentioned plasma medium in the paraxial approximation and its dependence on the propagation characteristics of the Gaussian laser pulse is obtained, and its variation in terms of the dimensionless plasma length is analyzed at different initial normalized plasma and cyclotron frequencies. The results show that the dimensionless beam width parameter is strongly affected by the initial plasma frequency, magnetic strength, and laser pulse intensity. Furthermore, it is found that there exists a certain intensity value below which the laser pulse tends to self focus, while the beam diverges above of this value. In addition, the results confirm that, by increasing the plasma and cyclotron frequencies (plasma density and magnetic strength), the self-focusing effect can occur intensively.

  16. Focused ion beams in biology.

    Science.gov (United States)

    Narayan, Kedar; Subramaniam, Sriram

    2015-11-01

    A quiet revolution is under way in technologies used for nanoscale cellular imaging. Focused ion beams, previously restricted to the materials sciences and semiconductor fields, are rapidly becoming powerful tools for ultrastructural imaging of biological samples. Cell and tissue architecture, as preserved in plastic-embedded resin or in plunge-frozen form, can be investigated in three dimensions by scanning electron microscopy imaging of freshly created surfaces that result from the progressive removal of material using a focused ion beam. The focused ion beam can also be used as a sculpting tool to create specific specimen shapes such as lamellae or needles that can be analyzed further by transmission electron microscopy or by methods that probe chemical composition. Here we provide an in-depth primer to the application of focused ion beams in biology, including a guide to the practical aspects of using the technology, as well as selected examples of its contribution to the generation of new insights into subcellular architecture and mechanisms underlying host-pathogen interactions.

  17. Focusing of truncated Gaussian beams

    Science.gov (United States)

    Horváth, Zoltán L.; Bor, Zsolt

    2003-07-01

    It is shown that the focusing of truncated Gaussian beams can be treated by the same manner as uniform spherical waves, i.e., the diffraction integral can be expressed by the Lommel functions, which offers a very efficient way for the calculation of the three-dimensional light distribution near focus. All the expressions for the uniform spherical waves hold good for Gaussian beams if the first variable in the Lommel functions is extended to the complex domain. The intensity distribution depending on the Fresnel number and the truncation coefficient is calculated. The location of the first few minima and maxima of the intensity in focal plane is given for different values of the truncation coefficient. The phase behavior depending on the truncation coefficient is studied.

  18. Geometrically focused neutral beam accelerators

    International Nuclear Information System (INIS)

    A more reliable 40 kV, 65 A power supply drain at 0.4 A/cm2, neutral-beam accelerator was developed for the Tandem Mirror Experiment (TMX). Multiple slotted aperture grids of 60% transparency are fabricated from refractory metal wires mounted to form a spherical surface. This geometrically focuses the beam by aiming individual beamlets at the center of curvature of the spherical grid (r = 3.2 m). We attain greater reliability and faster conditioning with geometrical focusing than with the previous technique of electrostatically steering beamlets to a common point. Electrostatic steering, accomplished by offsetting grid wires, is satisfactory if the offset of a beamlet is much less than the distance from the beamlet to the grids. It was found that Pierce Angle entrance grids performed better if sharper edged. A redesigned accelerator grid support structure reduced the number of ceramic-to-metal vacuum joints, and eliminated O rings between precisely aligned parts. The suppressor grid feedthrough is required to withstand a maximum voltage of 15 kV occurring during breakdown, greatly exceeding the operating voltage of 1.5 kV. Convenient fabrication and assembly techniques have been developed. Assembly of accelerators and plasma sources in a clean room appears to reduce the conditioning time. Following the successful testing of the prototype, eight 40 kV accelerators were built for TMX. Furthermore, ten 20 kV versions were built that are modifiable to 40 kV by exchanging the entrance grid

  19. Literature in Focus Beta Beams: Neutrino Beams

    CERN Multimedia

    2009-01-01

    By Mats Lindroos (CERN) and Mauro Mezzetto (INFN Padova, Italy) Imperial Press, 2009 The beta-beam concept for the generation of electron neutrino beams was first proposed by Piero Zucchelli in 2002. The idea created quite a stir, challenging the idea that intense neutrino beams only could be produced from the decay of pions or muons in classical neutrino beams facilities or in future neutrino factories. The concept initially struggled to make an impact but the hard work by many machine physicists, phenomenologists and theoreticians over the last five years has won the beta-beam a well-earned position as one of the frontrunners for a possible future world laboratory for high intensity neutrino oscillation physics. This is the first complete monograph on the beta-beam concept. The book describes both technical aspects and experimental aspects of the beta-beam, providing students and scientists with an insight into the possibilities o...

  20. Electron Beam Emission Characteristics from Plasma Focus Devices

    Science.gov (United States)

    Zhang, T.; Patran, A.; Wong, D.; Hassan, S. M.; Springham, S. V.; Tan, T. L.; Lee, P.; Lee, S.; Rawat, R. S.

    2006-01-01

    In this paper we observed the characteristics of the electron beam emission from our plasma focus machine filling neon, argon, helium and hydrogen. Rogowski coil and CCD based magnetic spectrometer were used to obtain temporal and energy distribution of electron emission. And the preliminary results of deposited FeCo thin film using electron beam from our plasma focus device were presented.

  1. Optimal beam focusing through turbulence.

    Science.gov (United States)

    Charnotskii, Mikhail

    2015-11-01

    Beam spread and beam wandering are the most perceptible effects of atmospheric turbulence on propagating laser beams. The width of the mean irradiance profile is typically used to characterize the beam spread. This so-called long-term (LT) statistic allows for a relatively simple theoretical description. However, the LT beam size is not a very practical measure of the beam spread because its measurements are sensitive to the movements of the source and detector, and to the large-scale variations of the refractive index that are not associated with turbulence. The short-term (ST) beam spread is measured relative to the instantaneous position of the beam center and is free of these drawbacks, but has not been studied as thoroughly as the LT spread. We present a theoretical model for the ST beam irradiance that is based on the parabolic equation for the beam wave propagation in random media, and the Markov approximation for calculation of the statistics of the optical field, and discuss an approximation that allows introduction of the isoplanatic ST point spread function (PSF). Unlike the LT PSF, the ST PSF depends on the overall beam geometry. This allows optimization of the initial beam field in terms of minimizing the ST beam size at the observation plane. Calculations supporting this conjecture are presented for the simple case of the coherent Gaussian beam, and Kolmogorov turbulence. PMID:26560908

  2. Optimal beam focusing through turbulence.

    Science.gov (United States)

    Charnotskii, Mikhail

    2015-11-01

    Beam spread and beam wandering are the most perceptible effects of atmospheric turbulence on propagating laser beams. The width of the mean irradiance profile is typically used to characterize the beam spread. This so-called long-term (LT) statistic allows for a relatively simple theoretical description. However, the LT beam size is not a very practical measure of the beam spread because its measurements are sensitive to the movements of the source and detector, and to the large-scale variations of the refractive index that are not associated with turbulence. The short-term (ST) beam spread is measured relative to the instantaneous position of the beam center and is free of these drawbacks, but has not been studied as thoroughly as the LT spread. We present a theoretical model for the ST beam irradiance that is based on the parabolic equation for the beam wave propagation in random media, and the Markov approximation for calculation of the statistics of the optical field, and discuss an approximation that allows introduction of the isoplanatic ST point spread function (PSF). Unlike the LT PSF, the ST PSF depends on the overall beam geometry. This allows optimization of the initial beam field in terms of minimizing the ST beam size at the observation plane. Calculations supporting this conjecture are presented for the simple case of the coherent Gaussian beam, and Kolmogorov turbulence.

  3. Influence of the shape and surface oxidation in the magnetization reversal of thin iron nanowires grown by focused electron beam induced deposition

    Directory of Open Access Journals (Sweden)

    Luis A. Rodríguez

    2015-06-01

    Full Text Available Iron nanostructures grown by focused electron beam induced deposition (FEBID are promising for applications in magnetic sensing, storage and logic. Such applications require a precise design and determination of the coercive field (HC, which depends on the shape of the nanostructure. In the present work, we have used the Fe2(CO9 precursor to grow iron nanowires by FEBID in the thickness range from 10 to 45 nm and width range from 50 to 500 nm. These nanowires exhibit an Fe content between 80 and 85%, thus giving a high ferromagnetic signal. Magneto-optical Kerr characterization indicates that HC decreases for increasing thickness and width, providing a route to control the magnetization reversal field through the modification of the nanowire dimensions. Transmission electron microscopy experiments indicate that these wires have a bell-type shape with a surface oxide layer of about 5 nm. Such features are decisive in the actual value of HC as micromagnetic simulations demonstrate. These results will help to make appropriate designs of magnetic nanowires grown by FEBID.

  4. Precise formation of geometrically focused ion beams

    International Nuclear Information System (INIS)

    Geometrically focused intense neutral beams for plasma diagnostic consist of many elementary beams formed by a multiaperture ion-optical system and aimed at the focal point. In real conditions, some of the elementary beams may have increased angular divergence and/or deviate from the intended direction, thus diminishing the neutral beam density at the focus. Several improvements to the geometrical focusing are considered in the article including flattening of the plasma profile across the emission surface, using of quasi-Pierce electrodes at the beam periphery, and minimizing the deviation of the electrodes from the spherical form. Application of these measures to the neutral beam Russian diagnostic injector developed in Budker Institute of Nuclear Physics allows an increase of neutral beam current density in the focus by ∼50%

  5. Underdense plasma lenses for focusing particle beams

    International Nuclear Information System (INIS)

    Plasma lenses are of interest for providing ultra-strong focusing of particle beams in order to enhance the luminosity of a high-energy linear collider. Previous work has explored the selfpinch of e+ or e- beams as they pass through an overdense slab of passive plasma (i.e., plasma density much greater than the beam density). Here the authors examine the focusing of beams in an underdense plasma through physical and particle simulation models. In this regime the plasma dynamics becomes highly non-linear and differs for e+ and e- beams. For e- beams the plasma electrons are almost completely expelled by the beam's space charge leaving a uniform column of ion charge that provides the focusing force. Compared to the overdense lens, the underdense lens has the advantages that spherical aberrations, longitudinal aberrations, and plasma contribution to background in the detectors are all greatly reduced. 10 refs., 4 figs., 1 tab

  6. Results of final focus test beam

    OpenAIRE

    Alexandrof, V.A.; Balakin, V.; Mikhailichenko, A..; Flottmann, K.; Peters, F.; Voss, G.A.; Bharadwaj, V.; Halling, M.; Buon, J.; Jeanjean, J.; LeDiberder, F.; Lepeltier, V.; Puzo, P.; Heimlinger, G.; Settles, R.

    1995-01-01

    The beam experiments of Final Focus Test Beam (FFTB) started in September 1993 at SLAC, and have produced a 1.7 μm×75 nm spot of 46 GeV electron beam. A number of new techniques involving two nanometer spot-size monitors have been developed. Several beam diagnostic/tuning schemes are applied to achieve and maintain the small spot. This experiment opens the way toward the nanometer world for future linear colliders

  7. Focused electron beam induced deposition: A perspective

    Directory of Open Access Journals (Sweden)

    Michael Huth

    2012-08-01

    Full Text Available Background: Focused electron beam induced deposition (FEBID is a direct-writing technique with nanometer resolution, which has received strongly increasing attention within the last decade. In FEBID a precursor previously adsorbed on a substrate surface is dissociated in the focus of an electron beam. After 20 years of continuous development FEBID has reached a stage at which this technique is now particularly attractive for several areas in both, basic and applied research. The present topical review addresses selected examples that highlight this development in the areas of charge-transport regimes in nanogranular metals close to an insulator-to-metal transition, the use of these materials for strain- and magnetic-field sensing, and the prospect of extending FEBID to multicomponent systems, such as binary alloys and intermetallic compounds with cooperative ground states.Results: After a brief introduction to the technique, recent work concerning FEBID of Pt–Si alloys and (hard-magnetic Co–Pt intermetallic compounds on the nanometer scale is reviewed. The growth process in the presence of two precursors, whose flux is independently controlled, is analyzed within a continuum model of FEBID that employs rate equations. Predictions are made for the tunability of the composition of the Co–Pt system by simply changing the dwell time of the electron beam during the writing process. The charge-transport regimes of nanogranular metals are reviewed next with a focus on recent theoretical advancements in the field. As a case study the transport properties of Pt–C nanogranular FEBID structures are discussed. It is shown that by means of a post-growth electron-irradiation treatment the electronic intergrain-coupling strength can be continuously tuned over a wide range. This provides unique access to the transport properties of this material close to the insulator-to-metal transition. In the last part of the review, recent developments in mechanical

  8. Applications of focused ion beams in microelectronics

    International Nuclear Information System (INIS)

    We present the conclusions of the RSRE programme on the application of focused ion beams in microelectronics and review the literature published in this field. We discuss the design and performance of focused beam implanters and the viability of their application to semiconductor device fabrication. Applications in the areas of lithography, direct implantation and micromachining are discussed in detail. Comparisons are made between the use of focused ion beams and existing techniques for these fabrication processes with a strong emphasis placed on the relative throughputs. We present results on a novel spot size measurement technique and the effect of beam heating on resist. We also present the results of studies into implantation passivation of resist to oxygen plasma attack as basis for a dry development lithography scheme. A novel lithography system employing flood electron exposure from a photocathode which is patterned by a focused ion beam which can also be used to repair mask defects is considered. (author)

  9. Focused Ion Beam Technology for Optoelectronic Devices

    Science.gov (United States)

    Reithmaier, J. P.; Bach, L.; Forchel, A.

    2003-08-01

    High-resolution proximity free lithography was developed using InP as anorganic resist for ion beam exposure. InP is very sensitive on ion beam irradiation and show a highly nonlinear dose dependence with a contrast function comparable to organic electron beam resists. In combination with implantation induced quantum well intermixing this new lithographic technique based on focused ion beams is used to realize high performance nano patterned optoelectronic devices like complex coupled distributed feedback (DFB) and distributed Bragg reflector (DBR) lasers.

  10. Plasma lenses for focusing particle beams

    International Nuclear Information System (INIS)

    The focusing of particles by a thin plasma lens is analyzed with physical, linearized fluid and particle-in-cell computational models. For parameters similar to next-generation linear colliders, the plasma lens strength can exceed 100 MG/cm, and the luminosity can be enhanced by an order of magnitude by passing each beam through an appropriate plasma slab. The plasma electrons affect the focusing by shifting so as to (partially or completely) charge neutralize the beam. Both overdense and underdense plasma lenses are described (plasma density n0 greater or less than beam density nb). The former case applies equally well to e+ and e- beams, while the latter has distinct advantages for e- beams (including smaller aberrations and background). The effects of spherical and longitudinal aberrations, emittance, plasma boundaries, and non-linear-plasma dynamics on the final spot size are discussed

  11. A stand for simulation and test of the magnetic components of the focus beam and transport systems for accelerator LUE-200, installation IREN

    International Nuclear Information System (INIS)

    Technical parameters and physical abilities of the equipment stand for simulation and testing of the dipole electromagnet to focus and transport the beam of the linear accelerator (LUE-200) are described. The overall design of the stand, a description of the magnetometer and the positioning system of Hall sensors are presented. The software of the stand has been developed

  12. The Superconducting Magnets of the ILC Beam Delivery System

    Energy Technology Data Exchange (ETDEWEB)

    Parker, B.; Anerella, M.; Escallier, J.; He, P.; Jain, A.; Marone, A.; /Brookhaven; Nosochkov, Y.; Seryi, Andrei; /SLAC

    2007-09-28

    The ILC Beam Delivery System (BDS) uses a variety of superconducting magnets to maximize luminosity and minimize background. Compact final focus quadrupoles with multifunction correction coils focus incoming beams to few nanometer spot sizes while focusing outgoing disrupted beams into a separate extraction beam line. Anti-solenoids mitigate effects from overlapping focusing and the detector solenoid field. Far from the interaction point (IP) strong octupoles help minimize IP backgrounds. A low-field but very large aperture dipole is integrated with the detector solenoid to reduce backgrounds from beamstrahlung pairs generated at the IP. Physics requirements and magnetic design solutions for the BDS superconducting magnets are reviewed in this paper.

  13. Nanopillar Fabrication with Focused Ion Beam Cutting

    NARCIS (Netherlands)

    Kuzmin, Oleksii V.; Pei, Yutao T.; De Hosson, Jeff T. M.

    2014-01-01

    A versatile method to fabricate taper-free micro-/nanopillars of large aspect ratio was developed with focused ion beam (FIB) cutting. The key features of the fabrication are a FIB with an incident angle of 90 degrees to the long axis of the pillar that enables milling of the pillar sideways avoidin

  14. Optimization of focused ion beam performance

    NARCIS (Netherlands)

    Hagen, C.W.; Kruit, P.

    2009-01-01

    The authors have analyzed how much current can be obtained in the probe of an optimized two-lens focused ion beam (FIB) system. This becomes relevant, as systems become available that have the potential to image and/or fabricate structures smaller than 10 nm. The probe current versus probe size curv

  15. Focused-ion-beam processing for photonics

    NARCIS (Netherlands)

    Ridder, de René M.; Hopman, Wico C.L.; Ay, Feridun

    2007-01-01

    Although focused ion beam (FIB) processing is a well-developed technology for many applications in electronics and physics, it has found limited application to photonics. Due to its very high spatial resolution in the order of 10 nm, and its ability to mill almost any material, it seems to have a go

  16. High Power Hydrogen Injector with Beam Focusing for Plasma Heating

    International Nuclear Information System (INIS)

    High power neutral beam injector has been developed with the atom energy of 25 keV, a current of 60 A, and several milliseconds pulse duration. Six of these injectors will be used for upgrade of the atomic injection system at central cell of a Gas Dynamic Trap (GDT) device and 2 injectors are planned for SHIP experiment.The injector ion source is based on an arc discharge plasma box. The plasma emitter is produced by a 1 kA arc discharge in hydrogen. A multipole magnetic field produced with permanent magnets at the periphery of the plasma box is used to increase its efficiency and improve homogeneity of the plasma emitter. The ion beam is extracted by a 4-electrodes ion optical system (IOS). Initial beam diameter is 200 mm. The grids of the IOS have a spherical curvature for geometrical focusing of the beam. The optimal IOS geometry and grid potentials were found with the numerical simulation to provide precise beam formation. The measured angular divergence of the beam is 0.02 rad, which corresponds to the 2.5 cm Gaussian radius of the beam profile measured at focal point

  17. Electron Beam Focusing in the Linear Accelerator (linac)

    Science.gov (United States)

    Jauregui, Luis

    2015-10-01

    To produce consistent data with an electron accelerator, it is critical to have a well-focused beam. To keep the beam focused, quadrupoles (quads) are employed. Quads are magnets, which focus the beam in one direction (x or y) and defocus in the other. When two or more quads are used in series, a net focusing effect is achieved in both vertical and horizontal directions. At start up there is a 5% calibration error in the linac at Thomas Jefferson National Accelerator Facility. This means that the momentum of particles passing through the quads isn't always what is expected, which affects the focusing of the beam. The objective is to find exactly how sensitive the focusing in the linac is to this 5% error. A linac was simulated, which contained 290 RF Cavities with random electric fields (to simulate the 5% calibration error), and a total momentum kick of 1090 MeV. National Science Foundation, Department of Energy, Jefferson Lab, Old Dominion University.

  18. Metal assisted focused-ion beam nanopatterning

    Science.gov (United States)

    Kannegulla, Akash; Cheng, Li-Jing

    2016-09-01

    Focused-ion beam milling is a versatile technique for maskless nanofabrication. However, the nonuniform ion beam profile and material redeposition tend to disfigure the surface morphology near the milling areas and degrade the fidelity of nanoscale pattern transfer, limiting the applicability of the technique. The ion-beam induced damage can deteriorate the performance of photonic devices and hinders the precision of template fabrication for nanoimprint lithography. To solve the issue, we present a metal assisted focused-ion beam (MAFIB) process in which a removable sacrificial aluminum layer is utilized to protect the working material. The new technique ensures smooth surfaces and fine milling edges; in addition, it permits direct formation of v-shaped grooves with tunable angles on dielectric substrates or metal films, silver for instance, which are rarely achieved by using traditional nanolithography followed by anisotropic etching processes. MAFIB was successfully demonstrated to directly create nanopatterns on different types of substrates with high fidelity and reproducibility. The technique provides the capability and flexibility necessary to fabricate nanophotonic devices and nanoimprint templates.

  19. Metal assisted focused-ion beam nanopatterning.

    Science.gov (United States)

    Kannegulla, Akash; Cheng, Li-Jing

    2016-09-01

    Focused-ion beam milling is a versatile technique for maskless nanofabrication. However, the nonuniform ion beam profile and material redeposition tend to disfigure the surface morphology near the milling areas and degrade the fidelity of nanoscale pattern transfer, limiting the applicability of the technique. The ion-beam induced damage can deteriorate the performance of photonic devices and hinders the precision of template fabrication for nanoimprint lithography. To solve the issue, we present a metal assisted focused-ion beam (MAFIB) process in which a removable sacrificial aluminum layer is utilized to protect the working material. The new technique ensures smooth surfaces and fine milling edges; in addition, it permits direct formation of v-shaped grooves with tunable angles on dielectric substrates or metal films, silver for instance, which are rarely achieved by using traditional nanolithography followed by anisotropic etching processes. MAFIB was successfully demonstrated to directly create nanopatterns on different types of substrates with high fidelity and reproducibility. The technique provides the capability and flexibility necessary to fabricate nanophotonic devices and nanoimprint templates. PMID:27479713

  20. Beam loss caused by edge focusing of injection bump magnets and its mitigation in the 3-GeV rapid cycling synchrotron of the Japan Proton Accelerator Research Complex

    Science.gov (United States)

    Hotchi, H.; Tani, N.; Watanabe, Y.; Harada, H.; Kato, S.; Okabe, K.; Saha, P. K.; Tamura, F.; Yoshimoto, M.

    2016-01-01

    In the 3-GeV rapid cycling synchrotron of the Japan Proton Accelerator Research Complex, transverse injection painting is utilized not only to suppress space-charge induced beam loss in the low energy region but also to mitigate foil scattering beam loss during charge-exchange injection. The space-charge induced beam loss is well minimized by the combination of modest transverse painting and full longitudinal painting. But, for sufficiently mitigating the foil scattering part of beam loss, the transverse painting area has to be further expanded. However, such a wide-ranging transverse painting had not been realized until recently due to beta function beating caused by edge focusing of pulsed injection bump magnets during injection. This beta function beating additionally excites random betatron resonances through a distortion of the lattice superperiodicity, and its resultant deterioration of the betatron motion stability causes significant extra beam loss when expanding the transverse painting area. To solve this issue, we newly installed pulse-type quadrupole correctors to compensate the beta function beating. This paper presents recent experimental results on this correction scheme for suppressing the extra beam loss, while discussing the beam loss and its mitigation mechanisms with the corresponding numerical simulations.

  1. H-Mode Accelerating Structures with PMQ Beam Focusing

    OpenAIRE

    Kurennoy, Sergey S.; Rybarcyk, Lawrence J.; O'Hara, James F.; Olivas, Eric R.; Wangler, Thomas P.

    2011-01-01

    We have developed high-efficiency normal-conducting RF accelerating structures by combining H-mode resonator cavities and a transverse beam focusing by permanent-magnet quadrupoles (PMQ), for beam velocities in the range of a few percent of the speed of light. The shunt impedance of inter-digital H-mode (IH-PMQ) structures is 10-20 times higher than that of a conventional drift-tube linac, while the transverse size is 4-5 times smaller. Results of the combined 3-D modeling - electromagnetic c...

  2. Nanostructuring superconducting vortex matter with focused ion beams

    Energy Technology Data Exchange (ETDEWEB)

    Guillamón, I. [Laboratorio de Bajas Temperaturas, Departamento de Física de la Materia Condensada, Instituto de Ciencia de Materiales Nicolás Cabrera, Facultad de Ciencias, Universidad Autónoma de Madrid, E-28049 Madrid (Spain); Unidad Asociada de Bajas Temperaturas y Altos Campos Magnéticos, UAM, CSIC, Cantoblanco, E-28049 Madrid (Spain); Suderow, H., E-mail: hermann.suderow@uam.es [Laboratorio de Bajas Temperaturas, Departamento de Física de la Materia Condensada, Instituto de Ciencia de Materiales Nicolás Cabrera, Facultad de Ciencias, Universidad Autónoma de Madrid, E-28049 Madrid (Spain); Unidad Asociada de Bajas Temperaturas y Altos Campos Magnéticos, UAM, CSIC, Cantoblanco, E-28049 Madrid (Spain); Kulkarni, P.; Vieira, S. [Laboratorio de Bajas Temperaturas, Departamento de Física de la Materia Condensada, Instituto de Ciencia de Materiales Nicolás Cabrera, Facultad de Ciencias, Universidad Autónoma de Madrid, E-28049 Madrid (Spain); Unidad Asociada de Bajas Temperaturas y Altos Campos Magnéticos, UAM, CSIC, Cantoblanco, E-28049 Madrid (Spain); Córdoba, R.; Sesé, J. [Laboratorio de Microscopías Avanzadas (LMA) – Instituto de Nanociencia de Aragón (INA), Universidad de Zaragoza, Zaragoza 50009 (Spain); Departamento de Física de la Materia Condensada, Universidad de Zaragoza, 50009 Zaragoza (Spain); and others

    2014-08-15

    Highlights: • Nanostructuring vortex matter with focused ion beams. • Nanofabrication produces high vortex density gradients. • Patterning gives nanocrystalline vortex lattice. - Abstract: Focused ion beams provide new opportunities to create small nanofabricated structures. Materials where this technique is successfully applied are different from those that are widely used in e-beam or photolithography processes. Arrays of holes have been fabricated in several layered superconductors, such as the transition metal dichalcogenides. A focused ion beam system can be also used to deposit superconducting material. A Ga beam is used to decompose a precusor W(CO){sub 6} molecule, giving an amorphous mixture of W–C–Ga–O which is superconducting below liquid helium temperatures. The amorphous nature of the deposit gives isotropic superconducting features, and vortex pinning is determined by the surface topography (or film thickness). Here we present vortex lattice images in an amorphous thin film with a nanofabricated array of dots. We find vortex confinement within the dots and inhomogeneous vortex distributions with large magnetic field gradients (around a Tesla in 10–20 nm). We discuss scaling behavior of the vortex lattice after nanofabrication.

  3. Ion Beam Extraction by Discrete Ion Focusing

    DEFF Research Database (Denmark)

    2010-01-01

    An apparatus (900) and methods are disclosed for ion beam extraction. In an implementation, the apparatus includes a plasma source (or plasma) (802) and an ion extractor (804). The plasma source is adapted to generate ions and the ion extractor is immersed in the plasma source to extract a fraction...... of the generated ions. The ion extractor is surrounded by a space charge (810) formed at least in part by the extracted ions. The ion extractor includes a biased electrode (806) forming an interface with an insulator (808). The interface is customized to form a strongly curved potential distribution (812......) in the space-charge surrounding the ion extractor. The strongly curved potential distribution focuses the extracted ions towards an opening (814) on a surface of the biased electrode thereby resulting in an ion beam....

  4. Electron beam final focus system for Thomson scattering at ELBE

    Science.gov (United States)

    Krämer, J. M.; Budde, M.; Bødker, F.; Irman, A.; Jochmann, A.; Kristensen, J. P.; Lehnert, U.; Michel, P.; Schramm, U.

    2016-09-01

    The design of an electron beam final focus system (FFS) aiming for high-flux laser-Thomson backscattering X-ray sources at ELBE is presented. A telescope system consisting of four permanent magnet based quadrupoles was found to have significantly less chromatic aberrations than a quadrupole doublet or triplet as commonly used. Focusing properties like the position of the focal plane and the spot size are retained for electron beam energies between 20 and 30 MeV by adjusting the position of the quadrupoles individually on a motorized stage. The desired ultra-short electron bunches require an increased relative energy spread up to a few percent and, thus, second order chromatic effects must be taken into account. We also present the design and test results of the permanent magnet quadrupoles. Adjustable shunts allow for correction of the field strength and compensation of deviations in the permanent magnet material. For a beam emittance of 13 mm mrad, we predict focal spot sizes of about 40 μm (rms) and divergences of about 10 mrad using the FFS.

  5. Electron beam final focus system for Thomson scattering at ELBE

    CERN Document Server

    Krämer, J.M.; Bødker, F.; Irman, A.; .Jochmann A.; Kristensen, J.P.; Lehnert U., HZDR; Michel, P.; Schrammb, U.; 10.1016/j.nima.2015.10.067

    2016-01-01

    The design of an electron beam final focus system (FFS) aiming for high-flux laser-Thomson backscattering X-ray sources at ELBE is presented. A telescope system consisting of four permanent magnet based quadrupoles was found to have significantly less chromatic aberrations than a quadrupole doublet or triplet as commonly used. Focusing properties like the position of the focal plane and the spot size are retained for electron beam energies between 20 and 30 MeV by adjusting the position of the quadrupoles individually on a motorized stage. The desired ultra-short electron bunches require an increased relative energy spread up to a few percent and, thus, second order chromatic effects must be taken into account. We also present the design and test results of the permanent magnet quadrupoles. Adjustable shunts allow for correction of the field strength and compensation of deviations in the permanent magnet material. For a beam emittance of 13 mm mrad, we predict focal spot sizes of about 40 μm (rms) and diverg...

  6. Electron Beam Final Focus System For Thomson Scattering At Elbe

    CERN Document Server

    Krämer, J.M.; Bødkera, F.; Irman, A.; Jochmann, A.; Kristensena, J.P.; Lehnert, U.; Michel, P.; Schramm, U.; 10.1016/j.nima.2015.10.067

    2016-01-01

    The design of an electron beam final focus system (FFS) aiming for high-flux laser-Thomson backscattering X-ray sources at ELBE is presented. A telescope system consisting of four permanent magnet based quadrupoles was found to have significantly less chromatic aberrations than a quadrupole doublet or triplet as commonly used. Focusing properties like the position of the focal plane and the spot size are retained for electron beam energies between 20 and 30 MeV by adjusting the position of the quadrupoles individually on a motorized stage. The desired ultra-short electron bunches require an increased relative energy spread up to a few percent and, thus, second order chromatic effects must be taken into account. We also present the design and test results of the permanent magnet quadrupoles. Adjustable shunts allow for correction of the field strength and compensation of deviations in the permanent magnet material. For a beam emittance of 13 mm mrad, we predict focal spot sizes of about 40 μm (rms) and diverg...

  7. Neutral beams for magnetic fusion

    International Nuclear Information System (INIS)

    Significant advances in forming energetic beams of neutral hydrogen and deuterium atoms have led to a breakthrough in magnetic fusion: neutral beams are now heating plasmas to thermonuclear temperatures, here at LLL and at other laboratories. For example, in our 2XIIB experiment we have injected a 500-A-equivalent current of neutral deuterium atoms at an average energy of 18 keV, producing a dense plasma (1014 particles/cm3) at thermonuclear energy (14 keV or 160 million kelvins). Currently, LLL and LBL are developing beam energies in the 80- to 120-keV range for our upcoming MFTF experiment, for the TFTR tokamak experiment at Princeton, and for the Doublet III tokamak experiment at General Atomic. These results increase our long-range prospects of producing high-intensity beams of energies in the hundreds or even thousands of kilo-electron-volts, providing us with optimistic extrapolations for realizing power-producing fusion reactors

  8. MTN magnet for the SPS extracted beam.

    CERN Multimedia

    1976-01-01

    This type of dipole magnet was used in the extracted beam lines of the North Area. It shows an opening for three different proton beam lines: a primary extracted proton beam, split by an upstream magnetic beam splitter (see photo 7612017) into three separated beams passes through different parts of its aperture: right, left up, left down. These magnets were designed to be concrete-insulated for radiation resistance. F. Streun stands on the right.

  9. Controllable Magnetic Focusing of Cold Atoms on a Chip

    Institute of Scientific and Technical Information of China (English)

    LIU Yang; YUN Min; YIN Jian-Ping

    2006-01-01

    @@ We propose a new lens scheme to focus cold atoms by using a controllable inhomogeneous magnetic field from a square current-carrying wire fabricated on a chip. The spatial distributions of the magnetic field are calculated, and the results show that the generated magnetic field is a two-dimensional (2D) quadrupole one and can be used to focus cold atoms or a cold atomic beam. The dynamic processes of cold atoms passing through our square wire layout and its focusing properties are studied by using Monte Carlo simulations. Our study shows that the atomic clouds can be focused effectively by our magnetic lens scheme, and the focal lengthof the atomic lens and its radius of focused spot can be continuously changed by adjusting the current in the wires.

  10. H-Mode Accelerating Structures with PMQ Beam Focusing

    CERN Document Server

    Kurennoy, Sergey S; O'Hara, James F; Olivas, Eric R; Wangler, Thomas P

    2011-01-01

    We have developed high-efficiency normal-conducting RF accelerating structures by combining H-mode resonator cavities and a transverse beam focusing by permanent-magnet quadrupoles (PMQ), for beam velocities in the range of a few percent of the speed of light. The shunt impedance of inter-digital H-mode (IH-PMQ) structures is 10-20 times higher than that of a conventional drift-tube linac, while the transverse size is 4-5 times smaller. Results of the combined 3-D modeling - electromagnetic computations, multi-particle beam-dynamics simulations with high currents, and thermal-stress analysis - for an IH-PMQ accelerator tank are presented. The accelerating field profile in the tank is tuned to provide the best propagation of a 50-mA deuteron beam using coupled iterations of electromagnetic and beam-dynamics modeling. Measurements of a cold model of the IH-PMQ tank show a good agreement with the calculations. H-PMQ accelerating structures following a short RFQ can be used both in the front end of ion linacs or ...

  11. Beam self-excited rf cavity driver for a deflector or focusing system

    Energy Technology Data Exchange (ETDEWEB)

    Wadlinger, E.A.

    1996-09-01

    A bunched beam from and accelerator can excite and power an rf cavity which then drives either a deflecting or focusing (including nonlinear focusing) rf cavity with and amplitude related to beam current. Rf power, generated when a bunched beam loses energy to an rf field when traversing an electric field that opposes the particle`s motion, is used to drive a separate (or the same) cavity to either focus or deflect the beam. The deflected beam can be stopped by an apertures or directed to a different area of a target depending on beam current. The beam-generated rf power can drive a radio-frequency quadrupole (RFQ) that can change the focusing properties of a beam channel as a function of beam current (space- charge force compensation or modifying the beam distribution on a target). An rf deflector can offset a beam to a downstream sextupole, effectively producing a position-dependent quadrupole field. The combination of rf deflector plus sextupole will produce a beam current dependent quadropole-focusing force. A static quadrupole magnet plus another rf deflector can place the beam back on the optic axis. This paper describes the concept, derives the appropriate equations for system analysis, and fives examples. A variation on this theme is to use the wake field generated in an rf cavity to cause growth in the beam emittance. The beam current would then be apertured by emittance defining slits.

  12. The Analysis of Quadrupole Magnetic Focusing Effect by Finite Element Method

    International Nuclear Information System (INIS)

    Quadrupole magnets will introduce focusing effect to a beam of the charge particle passing parallel to the magnet faces. The focusing effect is need to control the particle beam, so that it is in accordance with necessity requirement stated. This paper describes the analysis of focusing effect on the quadrupole magnetic by the finite element method. The finite element method in this paper is used for solve the potential distribution of magnetic field. If the potential magnetic field distribution in every node have known, a charge particle trajectory can be traced. This charge particle trajectory will secure the focusing effect of the quadrupole magnets. (author)

  13. Nonlinear Stability of Intense Mismatched Beams in a Uniform Focusing Field

    CERN Document Server

    Pakter, Renato; Simeoni, Wilson

    2005-01-01

    We investigate the nonlinear coupling between axisymmetric and elliptic oscillations in the dynamics of intense beams propagating in a uniform magnetic focusing field. It is shown that finite amplitude mismatched oscillations of an initially round beam may destabilize elliptic oscillations, heavily affecting stability and the shape of the beam. This is a potential mechanics for beam particle loss in such systems. Self consistent simulations are performed to verify the findings.

  14. Induced focusing and conversion of a Gaussian beam into an elliptic Gaussian beam

    Indian Academy of Sciences (India)

    Manoj Mishra; Swapan Konar

    2005-09-01

    We have presented an investigation of the induced focusing in Kerr media of two laser beams, the pump beam and the probe beam, which could be either Gaussian or elliptic Gaussian or a combination of the two. We have used variational formalism to derive relevant beam-width equations. Among several important findings, the finding that a very week probe beam can be guided and focused when power of both beams are well below their individual threshold for self-focusing, is a noteworthy one. It has been found that induced focusing is not possible for laser beams of any wavelength and beam radius. In case both beams are elliptic Gaussian, we have shown that when power of both beams is above a certain threshold value then the effective radius of both beams collapses and collapse distance depends on power. Moreover, it has been found that induced focusing can be employed to convert a circular Gaussian beam into an elliptic Gaussian beam.

  15. A Superconducting Magnet Upgrade of the ATF2 Final Focus

    Energy Technology Data Exchange (ETDEWEB)

    Parker B.; Anerella M.; Escallier J.; He P.; Jain A.; Marone A.; Wanderer P.; Wu K.C.; Hauviller C.; Marin E.; Tomas R.; Zimmermann F.; Bolzon B.; Jeremie A.; Kimura N.; Kubo K.; Kume T.; Kuroda S.; Okugi T.; Tauchi T.; Terunuma N.; Tomaru T.; Tsuchiya K.; Urakawa J.; Yamamoto A.; Bambabe P.; Coe P.; Urner D.; Seryi A.; Spencer C.; White G.

    2010-05-23

    The ATF2 facility at KEK is a proving ground for linear collider technology with a well instrumented extracted beam line and Final Focus (FF). The primary ATF2 goal is to demonstrate the extreme beam demagnification and spot stability needed for a linear collider FF. But the ATF2 FF uses water cooled magnets and the ILC baseline has a superconducting (SC) FF. We plan to upgrade ATF2 and replace some of the warm FF magnets with SC FF magnets. The ATF2 SC magnets, like the ILC FF, will made via direct wind construction. ATF2 coil winding is in progress at BNL and warm magnetic measurements indicate we have achieved good field quality. Studies indicate that having ATF2 FF magnets with larger aperture and better field quality should allow reducing the ATF2 FF beta function for study of focusing regimes relevant to CLIC. The ATF2 magnet cryostat will have laser view ports for directly monitoring cold mass movement. We plan to make stability measurements at BNL and KEK to relate ATF2 FF magnet performance to that of a full length ILC QD0 R and D FF prototype under construction at BNL.

  16. A Superconducting Magnet Upgrade of the ATF2 Final Focus

    Energy Technology Data Exchange (ETDEWEB)

    Parker, Brett; /Brookhaven; Anerella, Michael; /Brookhaven; Escallier, John; /Brookhaven; He, Ping; /Brookhaven; Jain, Animesh; /Brookhaven; Marone, Andrew; /Brookhaven; Wanderer, Peter; /Brookhaven; Wu, Kuo-Chen; /Brookhaven; Bambade, Philip; /Orsay, LAL; Bolzon, Benoit; /Annecy, LAPP; Jeremie, Andrea; /Annecy, LAPP; Coe, Paul; /Oxford U.; Urner, David /Oxford U.; Hauviller, Claude; /CERN; Marin, Eduardo; /CERN; Tomas, Rogelio; /CERN; Zimmermann, Frank; /CERN; Kimura, Nobuhiro; /KEK, Tsukuba; Kubo, Kiyoshi; /KEK, Tsukuba; Kume, Tatsuya /KEK, Tsukuba; Kuroda, Shigeru; /KEK, Tsukuba /KEK, Tsukuba /KEK, Tsukuba /KEK, Tsukuba /KEK, Tsukuba /KEK, Tsukuba /KEK, Tsukuba /KEK, Tsukuba /SLAC /SLAC /SLAC

    2012-07-05

    The ATF2 facility at KEK is a proving ground for linear collider technology with a well instrumented extracted beam line and Final Focus (FF). The primary ATF2 goal is to demonstrate the extreme beam demagnification and spot stability needed for a linear collider FF. But the ATF2 FF uses water cooled magnets and the ILC baseline has a superconducting (SC) FF. We plan to upgrade ATF2 and replace some of the warm FF magnets with SC FF magnets. The ATF2 SC magnets, like the ILC FF, will made via direct wind construction. ATF2 coil winding is in progress at BNL and warm magnetic measurements indicate we have achieved good field quality. Studies indicate that having ATF2 FF magnets with larger aperture and better field quality should allow reducing the ATF2 FF beta function for study of focusing regimes relevant to CLIC. The ATF2 magnet cryostat will have laser view ports for directly monitoring cold mass movement. We plan to make stability measurements at BNL and KEK to relate ATF2 FF magnet performance to that of a full length ILC QD0 R&D FF prototype under construction at BNL.

  17. Solenoidal Fields for Ion Beam Transport and Focusing

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Edward P.; Leitner, Matthaeus

    2007-11-01

    In this report we calculate time-independent fields of solenoidal magnets that are suitable for ion beam transport and focusing. There are many excellent Electricity and Magnetism textbooks that present the formalism for magnetic field calculations and apply it to simple geometries [1-1], but they do not include enough relevant detail to be used for designing a charged particle transport system. This requires accurate estimates of fringe field aberrations, misaligned and tilted fields, peak fields in wire coils and iron, external fields, and more. Specialized books on magnet design, technology, and numerical computations [1-2] provide such information, and some of that is presented here. The AIP Conference Proceedings of the US Particle Accelerator Schools [1-3] contain extensive discussions of design and technology of magnets for ion beams - except for solenoids. This lack may be due to the fact that solenoids have been used primarily to transport and focus particles of relatively low momenta, e.g. electrons of less than 50 MeV and protons or H- of less than 1.0 MeV, although this situation may be changing with the commercial availability of superconducting solenoids with up to 20T bore field [1-4]. Internal reports from federal laboratories and industry treat solenoid design in detail for specific applications. The present report is intended to be a resource for the design of ion beam drivers for Inertial Fusion Energy [1-5] and Warm Dense Matter experiments [1-6], although it should also be useful for a broader range of applications. The field produced by specified currents and material magnetization can always be evaluated by solving Maxwell's equations numerically, but it is also desirable to have reasonably accurate, simple formulas for conceptual system design and fast-running beam dynamics codes, as well as for general understanding. Most of this report is devoted to such formulas, but an introduction to the Tosca{copyright} code [1-7] and some

  18. Transformation of the beam intensity distribution and formation of a uniform ion beam by means of nonlinear focusing

    International Nuclear Information System (INIS)

    Avoiding undesirable thermal stress or damage of a target vessel is an essential subject in high-intensity beam irradiation for accelerator-driven neutron production. A promising method to tailor the transverse beam intensity distribution for uniform beam irradiation on the target is the use of multipole magnets. We, therefore, study the transformation and uniformization of the transverse intensity distribution by means of nonlinear focusing induced from multipole magnets. It is theoretically described how the intensity distribution is transformed and made uniform by the nonlinear focusing force. Large-area uniform proton and heavy-ion beams are experimentally formed using octupole magnets at the azimuthally-varying-field cyclotron in Japan Atomic Energy Agency. (author)

  19. An Atomic Lens Using a Focusing Hollow Beam

    Institute of Scientific and Technical Information of China (English)

    夏勇; 印建平; 王育竹

    2003-01-01

    We propose a new method to generate a focused hollow laser beam by using an azimuthally distributed 2π-phase plate and a convergent thin lens, and calculate the intensity distribution of the focused hollow beam in free propagation space. The relationship between the waist w0 of the incident collimated Gaussian beam and the dark spot size of the focused hollow beam at the focal point, and the relationship between the focal length f of the thin lens and the dark spot size are studied respectively. The optical potential of the blue-detuned focused hollow beam for 85Rb atoms is calculated. Our study shows that when the larger waist w of the incident Gaussian beam and the shorter focal length f of the lens are chosen, we can obtain an extremely small dark spot size of the focused hollow beam, which can be used to form an atomic lens with a resolution of several angstroms.

  20. Surface plasmon polariton beam focusing with parabolic nanoparticle chains

    DEFF Research Database (Denmark)

    Radko, Ilya P.; Bozhevolnyi, Sergey I.; Evlyukhin, Andrey B.;

    2007-01-01

    We report on the focusing of surface plasmon polariton (SPP) beams with parabolic chains of gold nanoparticles fabricated on thin gold films. SPP focusing with different parabolic chains is investigated in the wavelength range of 700–860 nm, both experimentally and theoretically. Mapping of SPP...... for parabolic structures to improve their focusing of slightly divergent SPP beams....

  1. Properties of self-focusing of elliptic beams

    International Nuclear Information System (INIS)

    Stationary self-focusing of collimated elliptic Gaussian beams is studied numerically. It is shown that the critical self-focusing power increases with increasing the axial ratio of the initial elliptic cross section. Self-focusing is accompanied by oscillations of the beam transverse size caused by the competition between the diffraction-limited divergence and nonlinear compression. As the power of the beam with the axial ratio a/b≥3 increases, aberration self-focusing occurs, at which, after the formation and competition of several intensity maxima in the beam cross section, a global maximum appears at the beam centre, which forms a nonlinear focus. The approximation formula for the self-focusing distance is generalised to elliptic beams. (nonlinear optical phenomena)

  2. C. Petrone et al.: "Magnetic measurement of the model magnet QD0 designed for the CLIC final focus beam transport line." CERN TE-MSC Internal Note, EDMS Nr: 1184196

    CERN Document Server

    Arpaia, Pasquale; Petrone, Carlo; Russenschuck, Stephan; Walckiers, Louis

    2012-01-01

    This note presents the results of the magnetic measurements performed on QD0, model magnet for the final focus transport line for CLIC (Fig. 1). This high-gradient, hybrid quadrupole has a yoke length of 0.1 m and an aperture of 8.3 mm. ND2Fe14B Permanent magnet blocks provide a gradient of 150 T/m, which can be further increased to 530 T/m when the four coils are excited to 18.3 A. The request was to measure the strength of the field and the multipole coefficients at different currents. The measurement of the field strength, by means of the single stretched wire system, was done in December 2011 in the I8 laboratory. The measurement of the multipole was done by means of the oscillating wire system [1][2].

  3. Measurements and simulations of focused beam for orthovoltage therapy

    International Nuclear Information System (INIS)

    Purpose: Megavoltage photon beams are typically used for therapy because of their skin-sparing effect. However, a focused low-energy x-ray beam would also be skin sparing, and would have a higher dose concentration at the focal spot. Such a beam can be produced with polycapillary optics. MCNP5 was used to model dose profiles for a scanned focused beam, using measured beam parameters. The potential of low energy focused x-ray beams for radiation therapy was assessed. Methods: A polycapillary optic was used to focus the x-ray beam from a tungsten source. The optic was characterized and measurements were performed at 50 kV. PMMA blocks of varying thicknesses were placed between optic and the focal spot to observe any variation in the focusing of the beam after passing through the tissue-equivalent material. The measured energy spectrum was used to model the focused beam in MCNP5. A source card (SDEF) in MCNP5 was used to simulate the converging x-ray beam. Dose calculations were performed inside a breast tissue phantom. Results: The measured focal spot size for the polycapillary optic was 0.2 mm with a depth of field of 5 mm. The measured focal spot remained unchanged through 40 mm of phantom thickness. The calculated depth dose curve inside the breast tissue showed a dose peak several centimeters below the skin with a sharp dose fall off around the focus. The percent dose falls below 10% within 5 mm of the focus. It was shown that rotating the optic during scanning would preserve the skin-sparing effect of the focused beam. Conclusions: Low energy focused x-ray beams could be used to irradiate tumors inside soft tissue within 5 cm of the surface

  4. Study of electron beam production by a plasma focus

    International Nuclear Information System (INIS)

    A preliminary investigation of the electron beam produced by a plasma focus device using a current charged transmission line is described. Electron beam currents as high as 10 kA were measured. Interaction of the extracted beam and the filling gas was studied using open shutter photography

  5. Plasma focusing and diagnosis of high energy particle beams

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Pisin.

    1990-09-01

    Various novel concepts of focusing and diagnosis of high energy charged particle beams, based on the interaction between the relativistic particle beam and the plasma, are reviewed. This includes overdense thin plasma lenses, and (underdense) adiabatic plasma lens, and two beam size monitor concepts. In addition, we introduce another mechanism for measuring flat beams based on the impulse received by heavy ions in an underdense plasma. Theoretical investigations show promise of focusing and diagnosing beams down to sizes where conventional methods are not possible to provide. 21 refs.

  6. Gabor lens focusing of a negative ion beam

    Energy Technology Data Exchange (ETDEWEB)

    Palkovic, J.A.; Mills, F.E.; Schmidt, C.; Young, D.E.

    1989-05-01

    Gabor or plasma lenses have previously been used to focus intense beams of positive ions at energies from 10 keV to 5 MeV. It is the large electrostatic field of the non-neutral plasma in the Gabor lens which is responsible for the focusing. Focusing an ion beam with a given sign of charge in a Gabor lens requires a non-neutral plasma with the opposite sign of charge as the beam. A Gabor lens constructed at Fermilab has been used to focus a 30 keV proton beam with good optical quality. We discuss studies of the action of a Gabor lens on a beam of negative ions. A Gabor lens has been considered for matching an H/sup /minus// beam into an RFQ in the redesign of the low energy section of the Fermilab linac. 9 refs., 3 figs., 1 tab.

  7. Gabor lens focusing of a negative ion beam

    International Nuclear Information System (INIS)

    Gabor or plasma lenses have previously been used to focus intense beams of positive ions at energies from 10 keV to 5 MeV. It is the large electrostatic field of the non-neutral plasma in the Gabor lens which is responsible for the focusing. Focusing an ion beam with a given sign of charge in a Gabor lens requires a non-neutral plasma with the opposite sign of charge as the beam. A Gabor lens constructed at Fermilab has been used to focus a 30 keV proton beam with good optical quality. We discuss studies of the action of a Gabor lens on a beam of negative ions. A Gabor lens has been considered for matching an H/sup /minus// beam into an RFQ in the redesign of the low energy section of the Fermilab linac. 9 refs., 3 figs., 1 tab

  8. Development of a focused ion beam micromachining system

    Energy Technology Data Exchange (ETDEWEB)

    Pellerin, J.G.; Griffis, D.; Russell, P.E.

    1988-12-01

    Focused ion beams are currently being investigated for many submicron fabrication and analytical purposes. An FIB micromachining system consisting of a UHV vacuum system, a liquid metal ion gun, and a control and data acquisition computer has been constructed. This system is being used to develop nanofabrication and nanomachining techniques involving focused ion beams and scanning tunneling microscopes.

  9. Beam Transport in Toroidal Magnetic Field

    CERN Document Server

    Joshi, N; Meusel, O; Ratzinger, U

    2016-01-01

    The concept of a storage ring with toroidal magnetic field was presented in the two previous EPAC conferences. Here we report the first results of experiments performed with beam transport in toroidal magnetic fields and details of the injection system. The beam transport experiments were carried out with 30 degree toroidal segments with an axial magnetic field of 0.6T. The multi turn injection system relies on a transverse injection coil together with an electric kicker system.

  10. Plasma lens experiments at the Final Focus Test Beam

    Energy Technology Data Exchange (ETDEWEB)

    Barletta, B. [California Univ., Los Angeles, CA (United States)]|[Lawrence Berkeley Lab., CA (United States); Chattopadhyay, S. [Lawrence Berkeley Lab., CA (United States); Chen, P. [Stanford Linear Accelerator Center, Menlo Park, CA (United States)] [and others

    1993-04-01

    We intend to carry out a series of plasma lens experiments at the Final Focus Test Beam facility at SLAC. These experiments will be the first to study the focusing of particle beams by plasma focusing devices in the parameter regime of interest for high energy colliders, and is expected to lead to plasma lens designs capable of unprecedented spot sizes. Plasma focusing of positron beams will be attempted for the first time. We will study the effects of lens aberrations due to various lens imperfections. Several approaches will be applied to create the plasma required including laser ionization and beam ionization of a working gas. At an increased bunch population of 2.5 {times} 10{sup 10}, tunneling ionization of a gas target by an electron beam -- an effect which has never been observed before -- should be significant. The compactness of our device should prove to be of interest for applications at the SLC and the next generation linear colliders.

  11. Beam loss reduction by magnetic shielding using beam pipes and bellows of soft magnetic materials

    Science.gov (United States)

    Kamiya, J.; Ogiwara, N.; Hotchi, H.; Hayashi, N.; Kinsho, M.

    2014-11-01

    One of the main sources of beam loss in high power accelerators is unwanted stray magnetic fields from magnets near the beam line, which can distort the beam orbit. The most effective way to shield such magnetic fields is to perfectly surround the beam region without any gaps with a soft magnetic high permeability material. This leads to the manufacture of vacuum chambers (beam pipes and bellows) with soft magnetic materials. A Ni-Fe alloy (permalloy) was selected for the material of the pipe parts and outer bellows parts, while a ferritic stainless steel was selected for the flanges. An austenitic stainless steel, which is non-magnetic material, was used for the inner bellows for vacuum tightness. To achieve good magnetic shielding and vacuum performances, a heat treatment under high vacuum was applied during the manufacturing process of the vacuum chambers. Using this heat treatment, the ratio of the integrated magnetic flux density along the beam orbit between the inside and outside of the beam pipe and bellows became small enough to suppress beam orbit distortion. The outgassing rate of the materials with this heat treatment was reduced by one order magnitude compared to that without heat treatment. By installing the beam pipes and bellows of soft magnetic materials as part of the Japan Proton Accelerator Research Complex 3 GeV rapid cycling synchrotron beam line, the closed orbit distortion (COD) was reduced by more than 80%. In addition, a 95.5% beam survival ratio was achieved by this COD improvement.

  12. Beam profiling at focus: the search for the Holy Grail

    Science.gov (United States)

    Green, Lawrence I.

    2007-02-01

    Electronic laser beam profiling is now a widely accepted method to measure the mode quality and spatial profile of a laser beam. For the most part, profiling has been limited to the unfocused or 'raw' beam, because the energy density or irradiance in the vicinity of focus is high enough to destroy almost any measurement device. Recent developments in measuring technology now enable users to make beam profiling measurements at and near the focus of many lasers. We discuss two new designs and show examples of how they function.

  13. Study on electron beam in a low energy plasma focus

    International Nuclear Information System (INIS)

    Electron beam emission was investigated in a low energy plasma focus device (2.2 kJ) using copper hollow anode. Faraday cup was used to estimate the energy of the electron beam. XR100CR X-ray spectrometer was used to explore the impact of the electron beam on the target observed from top-on and side-on position. Experiments were carried out at optimized pressure of argon gas. The impact of electron beam is exceptionally notable with two different approaches using lead target inside hollow anode in our plasma focus device

  14. Production of GW electron and ion beams by focused discharges

    International Nuclear Information System (INIS)

    This chapter attempts to determine how magnetized plasma structure and current distribution must vary with time in the pinch region to have a consistent picture. A method is presented to evaluate the total charge of a beam from a single discharge. Discusses the experimental system; an optimized mode of operation; ion beams; electron beams; the beam source; and plasmoid imaging by nuclear tracks in solids. The data support the existence of a fibrous structure for all stages of evolution of the current sheath (CS), from propagation in the interelectrodegap to axial-pinch collapse and at a later time when CS is fragmented

  15. Focused ion beams using a high-brightness plasma source

    Science.gov (United States)

    Guharay, Samar

    2002-10-01

    High-brightness ion beams, with low energy spread, have merits for many new applications in microelectronics, materials science, and biology. Negative ions are especially attractive for the applications that involve beam-solid interactions. When negative ions strike a surface, especially an electrically isolated surface, the surface charging voltage is limited to few volts [1]. This property can be effectively utilized to circumvent problems due to surface charging, such as device damage and beam defocusing. A compact plasma source, with the capability to deliver either positive or negative ion beams, has been developed. H- beams from this pulsed source showed brightness within an order of magnitude of the value for beams from liquid-metal ion sources. The beam angular intensity is > 40 mAsr-1 and the corresponding energy spread is 1 Acm-2 and a spot size of 100 nm. Such characteristics of focused beam parameters, using a dc source, will immediately open up a large area of new applications. [1] P. N. Guzdar, A. S. Sharma, S. K. Guharay, "Charging of substrates irradiated by particle beams" Appl. Phys. Lett. 71, 3302 (1997). [2] S. K. Guharay, E. Sokolovsky, J. Orloff, "Characteristics of ion beams from a Penning source for focused ion beam applications" J. Vac. Sci Technol. B17, 2779 (1999).

  16. SU-D-304-02: Magnetically Focused Proton Irradiation of Small Field Targets

    Energy Technology Data Exchange (ETDEWEB)

    McAuley, GA; Slater, JM [Loma Linda University, Loma Linda, CA (United States); Slater, JD; Wroe, AJ [Loma Linda University Medical Center, Loma Linda, CA (United States)

    2015-06-15

    Purpose: To investigate the use of magnetic focusing for small field proton irradiations. It is hypothesized that magnetic focusing will provide significant dose distribution benefits over standard collimated beams for fields less than 10 mm diameter. Methods: Magnets consisting of 24 segments of radiation hard samarium-cobalt adhered into hollow cylinders were designed and manufactured. Two focusing magnets were placed on a positioning track on our Gantry 1 treatment table. Proton beams with energies of 127 and 157 MeV, 15 and 30 mm modulation, and 8 mm initial diameters were delivered to a water tank using single-stage scattering. Depth dose distributions were measured using a PTW PR60020 diode detector and transverse profiles were measured with Gafchromic EBT3 film. Monte Carlo simulations were also performed - both for comparison with experimental data and to further explore the potential of magnetic focusing in silica. For example, beam spot areas (based on the 90% dose contour) were matched at Bragg depth between simulated 100 MeV collimated beams and simulated beams focused by two 400 T/m gradient magnets. Results: Preliminary experimental results show 23% higher peak to entrance dose ratios and flatter spread out Bragg peak plateaus for 8 mm focused beams compared with uncollimated beams. Monte Carlo simulations showed 21% larger peak to entrance ratios and a ∼9 fold more efficient dose to target delivery compared to spot-sized matched collimated beams. Our latest results will be presented. Conclusion: Our results suggest that rare earth focusing magnet assemblies could reduce skin dose and beam number while delivering dose to nominally spherical radiosurgery targets over a much shorter time compared to unfocused beams. Immediate clinical applications include those associated with proton radiosurgery and functional radiosurgery of the brain and spine, however expanded treatment sites can be also envisaged.

  17. Observations of underdense plasma lens focusing of relativistic electron beams

    International Nuclear Information System (INIS)

    Focusing of a 15 MeV, 19 nC electron bunch by an underdense plasma lens operated just beyond the threshold of the underdense condition has been demonstrated in experiments at the Fermilab NICADD Photoinjector Laboratory (FNPL). The strong 1.9 cm focal-length plasma-lens focused both transverse directions simultaneously and reduced the minimum area of the beam spot by a factor of 23. Analysis of the beam-envelope evolution observed near the beam waist shows that the spherical aberrations of this underdense lens are lower than those of an overdense plasma lens, as predicted by theory. Correlations between the beam charge and the properties of the beam focus corroborate this conclusion

  18. Structuring of silicon with low energy focused ion beams

    Energy Technology Data Exchange (ETDEWEB)

    Nebiker, P.W.; Doebeli, M. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Muehle, R. [Eidgenoessische Technische Hochschule, Zurich (Switzerland)

    1997-09-01

    The defect production in silicon induced by focused ion beam irradiation as a function of energy and projectile mass has been investigated and compared to the measured sputter yield. The aim was to find optimal beam parameters for the structuring of semiconductors with a minimum amount of defects produced per removed atom. (author) 2 figs., 2 refs.

  19. Materials processing with tightly focused femtosecond vortex laser beams

    OpenAIRE

    Hnatovsky, Cyril; Shvedov, Vladlen G.; Krolikowski, Wieslaw; Rode, Andrei V.

    2010-01-01

    This letter is the first demonstration of material modification using tightly focused femtosecond laser vortex beams. Double-charge femtosecond vortices were synthesized with the polarization-singularity beam converter described in Ref [1] and then focused using moderate and high numerical aperture optics (viz., NA = 0.45 and 0.9) to ablate fused silica and soda-lime glasses. By controlling the pulse energy we consistently machine high-quality micron-size ring-shaped structures with less than...

  20. Six beam spherical compression of plasma focus guns

    International Nuclear Information System (INIS)

    A preliminary experiment with a one beam plasma focus is carried out to confirm plasma formation with the lowest input energy of 0.2 kJ for six beam spherical compression of plasma focus guns. The plasma front of this cableless gun can be used for compression and for the coupling of six guns situated along three rectangular axes, providing a good plasma focus pinch instantaneously or many plasma focus pinches continuously. The whole device with the energy bank is mounted on a sphere, and the minimum requirement for the plasma chamber of this sphere is a diameter of ∼ 22 cm. (author). 4 refs, 3 figs

  1. Monte Carlo simulations of nanoscale focused neon ion beam sputtering.

    Science.gov (United States)

    Timilsina, Rajendra; Rack, Philip D

    2013-12-13

    A Monte Carlo simulation is developed to model the physical sputtering of aluminum and tungsten emulating nanoscale focused helium and neon ion beam etching from the gas field ion microscope. Neon beams with different beam energies (0.5-30 keV) and a constant beam diameter (Gaussian with full-width-at-half-maximum of 1 nm) were simulated to elucidate the nanostructure evolution during the physical sputtering of nanoscale high aspect ratio features. The aspect ratio and sputter yield vary with the ion species and beam energy for a constant beam diameter and are related to the distribution of the nuclear energy loss. Neon ions have a larger sputter yield than the helium ions due to their larger mass and consequently larger nuclear energy loss relative to helium. Quantitative information such as the sputtering yields, the energy-dependent aspect ratios and resolution-limiting effects are discussed.

  2. Point focusing of intense ion beam by spherical open-quotes plasma focus diodeclose quotes

    International Nuclear Information System (INIS)

    Three-dimensional focusing of intense ion-beam has been obtained by using spherical open-quotes plasma focus diode.close quotes Experimental data have shown that ion beam was focused into a small cylindrical volume with ∼0.5 mm in diameter and ∼2.5 mm in length, where the ion-beam current density and the power density is estimated to be ∼680 kA/cm2 and ∼0.54 TW/cm2

  3. Three-dimensional, tight focusing of intense pulsed light-ion beam by spherical plasma focus diode

    International Nuclear Information System (INIS)

    A new type of ion-beam diode, self-magnetically insulated, spherica plasma focus diode (SPFD), was developed. With the SPFD, three-dimensional focusing of an intense pulsed light-ion beam was obtained. Experiments and simulations were carried out to study the behavior of the SPFD. In the experiments, diagnostic results of the Rutherford scattering pinhole camera and the shadow-box showed that the ion beam was focused into a small cylindrical area with ∼ 0.5mm in diameter and ∼ 2.5 mm in length. The average ion-beam current density at the anode surface was found to be ∼ 2 kA/cm2. In the simulations, it was observed that most of the diode gap is well insulated by the self-magnetic field induced by the diode current. The electron sheath in the diode gap significantly enhances the ion flow from the anode. As a result, the ion current density is several times higher than the single-species space-charge limited value. (author)

  4. H-mode accelerating structures with PMQ focusing for low-beta ion beams

    Energy Technology Data Exchange (ETDEWEB)

    Kurennoy, Sergey S [Los Alamos National Laboratory; O' Hara, James F [Los Alamos National Laboratory; Olivas, Eric R [Los Alamos National Laboratory; Rybarcyk, Lawrence J [Los Alamos National Laboratory

    2010-01-01

    We are developing high-efficiency normal-conducting RF accelerating structures based on inter-digital H-mode (IH) cavities and the transverse beam focusing with permanent-magnet quadrupoles (PMQ), for beam velocities in the range of a few percent of the speed of light. Such IH-PMQ accelerating structures following a short RFQ can be used in the front end of ion linacs or in stand-alone applications, e.g. a compact deuteron-beam accelerator up to the energy of several MeV. Results of combined 3-D modeling for a full IH-PMQ accelerator tank - electromagnetic computations, beam-dynamics simulations with high currents, and thermal-stress analysis - are presented. The accelerating field profile in the tank is tuned to provide the best beam propagation using coupled iterations of electromagnetic and beam-dynamics modeling. A cold model of the IH-PMQ tank is being manufactured.

  5. Three-dimensional measurement of a tightly focused laser beam

    Directory of Open Access Journals (Sweden)

    Xiangsheng Xie

    2013-02-01

    Full Text Available The spatial structure of a tightly focused light field is measured with a double knife-edge scanning method. The measurement method is based on the use of a high-quality double knife-edge fabricated from a right-angled silicon fragment mounted on a photodetector. The reconstruction of the three-dimensional structures of tightly focused spots is carried out with both uniform and partially obstructed linearly polarized incident light beams. The optical field distribution is found to deviate substantially from the input beam profile in the tightly focused region, which is in good agreement with the results of numerical simulations.

  6. Hybrid laser-beam-shaping system for rotatable dual beams with long depth of focus

    Science.gov (United States)

    Chou, Fu-Lung; Chen, Cheng-Huan; Lin, Yu-Chung; Lin, Mao-Chi

    2016-08-01

    A laser processing system consisting of two diffractive elements and one refractive element is proposed enabling a Gaussian laser beam to be transformed into two beams with a depth of focus of up to 150 µm and focal spot smaller than 5 µm. For specific laser processing, the two beams are rotatable when the beam-splitting diffractive element is rotated. The overall system is versatile for laser cutting and drilling.

  7. Optimal focusing of a beam in a ring vortex

    Science.gov (United States)

    Arrizón, Victor; Ruiz, Ulises; Aguirre-Olivas, Dilia; Mellado-Villaseñor, Gabriel

    2015-12-01

    Conventional light focusing, i.e. concentration of an extended optical field within a small area around a point, is a frequently used process in Optics. An important extension to conventional focusing is the generation of the annular focal field of an optical beam. We discuss a simple optical setup that achieves this kind of focusing employing a phase plate as unique optical component. It is assumed that the annular focal field is modulated by an azimuthal phase of integer order q that converts the field in a ring vortex. We first establish the class of beams that being transmitted through the phase plate can be focused into a ring vortex. Then, for each beam in this class we determine the plate transmittance that generates the vortex with the maximum possible intensity, which is referred to as optimal ring vortex.

  8. Comparison of electric and magnetic quadrupole focusing for the low energy end of an induction-linac-ICF [Inertial-Confinement-Fusion] driver

    International Nuclear Information System (INIS)

    This report compares two physics designs of the low energy end of an induction linac-ICF driver: one using electric quadrupole focusing of many parallel beams followed by transverse combining; the other using magnetic quadrupole focusing of fewer beams without beam combining. Because of larger head-to-tail velocity spread and a consequent rapid current amplification in a magnetic focusing channel, the overall accelerator size of the design using magnetic focusing is comparable to that using electric focusing

  9. Simulation of ion beam extraction and focusing system

    Institute of Scientific and Technical Information of China (English)

    B.A.Soliman; M.M.Abdelrahman; A.G.Helal; F.W.Abdelsalam

    2011-01-01

    The characteristics of ion beam extraction and focused to a volume as small as possible were investigated with the aid of computer code SIMION 3D version 7.This has been used to evaluate the extraction characteristics(accel-decel system)to generate an ion beam with low beam emittance and high brightness.The simulation process can provide a good study for optimizing the extraction and focusing system of the ion beam without any losses and transported to the required target.Also,a study of a simulation model for the extraction system of the ion source was used to describe the possible plasma boundary curvatures during the ion extraction that may be affected by the change in an extraction potential with a constant plasma density meniscus.

  10. Cobalt alloy ion sources for focused ion beam implantation

    Energy Technology Data Exchange (ETDEWEB)

    Muehle, R.; Doebeli, M. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Zimmermann, P. [Eidgenoessische Technische Hochschule, Zurich (Switzerland)

    1997-09-01

    Cobalt alloy ion sources have been developed for silicide formation by focused ion beam implantation. Four eutectic alloys AuCo, CoGe, CoY and AuCoGe were produced by electron beam welding. The AuCo liquid alloy ion source was investigated in detail. We have measured the emission current stability, the current-voltage characteristics, and the mass spectrum as a function of the mission current. (author) 1 fig., 2 refs.

  11. Ring lens for focusing ion beams to uniform densities

    International Nuclear Information System (INIS)

    An electrostatic lens was designed and built to focus a beam of positive ions into uniform density on a target. The lens has two concentric field regions with a grid separating the inner zero field from the outer radial field. For proper operation the incident ions must emanate with axial symmetry and Gaussian or similar divergence from a small source. An appendix is included on the symmetrization of elliptical beams by a quadrupole singlet lens. (U.S.)

  12. Aberrations due to solenoid focusing of a multiply charged high-current ion beam

    CERN Document Server

    Grégoire, G; Lisi, N; Schnuriger, J C; Scrivens, R; Tambini, J

    2000-01-01

    At the output of a laser ion source, a high current of highly charged ions with a large range of charge states is available. The focusing of such a beam by magnetic elements causes a nonlinear space-charge field to develop which can induce large aberrations and emittance growth in the beam. Simulation of the beam from the CERN laser ion source will be presented for an ideal magnetic and electrostatic system using a radially symmetric model. In addition, the three dimensional software KOBRA3 is used for the simulation of the solenoid line. The results of these simulations will be compared with experiments performed on the CERN laser ion source with solenoids (resulting in a hollow beam) and a series of gridded electrostatic lenses. (5 refs).

  13. A compact beam focusing and steering element using quadrupoles with independently excited poles

    Energy Technology Data Exchange (ETDEWEB)

    Grime, Geoffrey W., E-mail: g.grime@surrey.ac.uk [University of Surrey, Ion Beam Centre, Advanced Technology Institute, Guildford GU2 7XH (United Kingdom)

    2013-07-01

    Beam steering elements for accelerator beam transport are conventionally and conveniently incorporated into beamlines by fitting magnetic dipole elements around the vacuum tube of the line. Two steerers in each plane (X and Y) together with a quadrupole doublet constitute a module providing full control of the direction, position and focus of the beam. In some installations however, there may be insufficient space on the beamline to mount separate steerer elements. To provide steering capabilities in such a situation we have used a magnetic quadrupole doublet with the coils of each pole independently excited to synthesise the desired combination of quadrupole, horizontal dipole and vertical dipole fields. This paper describes the quadrupole steerer and its multichannel power supply and presents calculated magnetic field distributions together with raytracing simulation of its performance.

  14. Enabling Nanotechnology with Focused Ion Beams from Laser Cooled Atoms

    Science.gov (United States)

    Steele, A. V.; Knuffman, B.; Orloff, J.; Maazouz, M.; McClelland, J. J.

    2011-05-01

    The Magneto-Optical Trap Ion Source (MOTIS) being developed at NIST has the potential to enable numerous advances in nanoscale science. In a MOTIS, atoms are captured into a MOT, photoionized, and accelerated to an energy of a few hundred eV to a few tens of kV. A beam formed in this way can be brought to a tight focus, competitive with the commercial focused ion beam machines deployed widely today. Additionally, the unique characteristics of this source, coupled with the user's choice of ion from the long and growing list of laser-coolable atomic species suggest that the MOTIS has the potential to advance the state of the art in applications such as imaging, nanofabrication, secondary ion mass spectrometry, and others. I will present high-resolution images from our lithium and chromium MOTIS-based focused ion beams and discuss applications which we will pursue with these new tools.

  15. Photon beam studies of magnetic materials

    Science.gov (United States)

    Lovesey, S. W.

    1994-06-01

    The past decade has seen a surge of activity in the use of photon beam techniques to study magnetic properties of materials. By and large, in this period the experimental work has been accomplished with beams produced by electron synchrotron facilities. To date, it is fair to say that the surge of activity is underpinned by improvements in instrument performance, enjoyed at synchrotron sources, rather than outstanding intellectual advances. In consequence, improvements in the intensity at the sample, and the provision of good beams of polarized photons, which enable polarization induced discrimination effects to be exploited as a means of increasing the signal-to-noise, are particularly significant in the use for magnetic studies of photon beam techniques.

  16. Optimization of a plasma focus device as an electron beam source for thin film deposition

    Science.gov (United States)

    Zhang, T.; Lin, J.; Patran, A.; Wong, D.; Hassan, S. M.; Mahmood, S.; White, T.; Tan, T. L.; Springham, S. V.; Lee, S.; Lee, P.; Rawat, R. S.

    2007-05-01

    Electron beam emission characteristics from neon, argon, hydrogen and helium in an NX2 dense plasma focus (DPF) device were investigated in order to optimize the plasma focus device for deposition of thin films using energetic electron beams. A Rogowski coil and CCD based magnetic spectrometer were used to obtain temporal characteristics, total electron charge and energy distributions of electron emission from the NX2 DPF device. It is found that hydrogen should be the first choice for thin film deposition as it produces the highest electron beam charge and higher energy (from 50 to 200 keV) electrons. Neon is the next best choice as it gives the next highest electron beam charge with mid-energy (from 30 to 70 keV) electrons. The operation of NX2 with helium at voltages above 12 kV produces a mid-energy (from 30 to 70 keV) electron beam with low-electron beam charge, however, argon is not a good electron beam source for our NX2 DPF device. Preliminary results of the first ever thin film deposition using plasma focus assisted pulsed electron deposition using a hydrogen operated NX2 plasma focus device are presented.

  17. Stable two-plane focusing for emittance-dominated sheet-beam transport

    Science.gov (United States)

    Carlsten, B. E.; Earley, L. M.; Krawczyk, F. L.; Russell, S. J.; Potter, J. M.; Ferguson, P.; Humphries, S.

    2005-06-01

    Two-plane focusing of sheet electron beams will be an essential technology for an emerging class of high-power, 100 to 300 GHz rf sources [Carlsten et al., IEEE Trans. Plasma Sci. 33, 85 (2005), ITPSBD, 0093-3813, 10.1109/TPS.2004.841172]. In these devices, the beam has a unique asymmetry in which the transport is emittance dominated in the sheet’s thin dimension and space-charge dominated in the sheet’s wide dimension. Previous work has studied the stability of the transport of beams in the emittance-dominated regime for both wiggler and periodic permanent magnet (PPM) configurations with single-plane focusing, and has found that bigger envelope scalloping occurs for equilibrium transport, as compared to space-charge dominated beams [Carlsten et al., this issue, Phys. Rev. ST Accel. Beams 8, 062001 (2005), PRABFM, 1098-4402]. In this paper, we describe the differences in transport stability when two-plane focusing is included. Two-plane wiggler focusing degrades the transport stability slightly, whereas two-plane PPM focusing greatly compromises the transport. On the other hand, single-plane PPM focusing can be augmented with external quadrupole fields to provide weak focusing in the sheet’s wide dimension, which has stability comparable to two-plane wiggler transport.

  18. Materials processing with tightly focused femtosecond vortex laser beams

    CERN Document Server

    Hnatovsky, Cyril; Krolikowski, Wieslaw; Rode, Andrei V

    2010-01-01

    This letter is the first demonstration of material modification using tightly focused femtosecond laser vortex beams. Double-charge femtosecond vortices were synthesized with the polarization-singularity beam converter described in Ref [1] and then focused using moderate and high numerical aperture optics (viz., NA = 0.45 and 0.9) to ablate fused silica and soda-lime glasses. By controlling the pulse energy we consistently machine high-quality micron-size ring-shaped structures with less than 100 nm uniform groove thickness.

  19. Excitation of radiationless anapole mode of isotropic dielectric nanoparticles with tightly focused radially polarized beam

    CERN Document Server

    Wei, Lei; Bhattacharya, Nandini; Urbach, H Paul

    2016-01-01

    A high index dielectric nano-sphere can be excited and yet remain radiationless. A method to excite the non-radiating anapole mode of a high index isotropic dielectric nanosphere is presented. With tightly focused radially polarized beam illumination, the main-contributing electric dipole mode and magnetic modes can be zero with only a weak electric quadruple contributing to the total scattering. Further, with a standing wave illumination formed by two counter-propagating focused radially polarized beam under $4\\pi$ configuration, the ideal radiationless ananpole can be excited.

  20. Expanded studies of linear collider final focus systems at the Final Focus Test Beam

    Energy Technology Data Exchange (ETDEWEB)

    Tenenbaum, P.G.

    1995-12-01

    In order to meet their luminosity goals, linear colliders operating in the center-of-mass energy range from 3,50 to 1,500 GeV will need to deliver beams which are as small as a few Manometers tall, with x:y aspect ratios as large as 100. The Final Focus Test Beam (FFTB) is a prototype for the final focus demanded by these colliders: its purpose is to provide demagnification equivalent to those in the future linear collider, which corresponds to a focused spot size in the FFTB of 1.7 microns (horizontal) by 60 manometers (vertical). In order to achieve the desired spot sizes, the FFTB beam optics must be tuned to eliminate aberrations and other errors, and to ensure that the optics conform to the desired final conditions and the measured initial conditions of the beam. Using a combination of incoming-beam diagnostics. beam-based local diagnostics, and global tuning algorithms, the FFTB beam size has been reduced to a stable final size of 1.7 microns by 70 manometers. In addition, the chromatic properties of the FFTB have been studied using two techniques and found to be acceptable. Descriptions of the hardware and techniques used in these studies are presented, along with results and suggestions for future research.

  1. Expanded studies of linear collider final focus systems at the Final Focus Test Beam

    International Nuclear Information System (INIS)

    In order to meet their luminosity goals, linear colliders operating in the center-of-mass energy range from 3,50 to 1,500 GeV will need to deliver beams which are as small as a few Manometers tall, with x:y aspect ratios as large as 100. The Final Focus Test Beam (FFTB) is a prototype for the final focus demanded by these colliders: its purpose is to provide demagnification equivalent to those in the future linear collider, which corresponds to a focused spot size in the FFTB of 1.7 microns (horizontal) by 60 manometers (vertical). In order to achieve the desired spot sizes, the FFTB beam optics must be tuned to eliminate aberrations and other errors, and to ensure that the optics conform to the desired final conditions and the measured initial conditions of the beam. Using a combination of incoming-beam diagnostics. beam-based local diagnostics, and global tuning algorithms, the FFTB beam size has been reduced to a stable final size of 1.7 microns by 70 manometers. In addition, the chromatic properties of the FFTB have been studied using two techniques and found to be acceptable. Descriptions of the hardware and techniques used in these studies are presented, along with results and suggestions for future research

  2. Flat-Lens Focusing of Electron Beams in Graphene.

    Science.gov (United States)

    Tang, Yang; Cao, Xiyuan; Guo, Ran; Zhang, Yanyan; Che, Zhiyuan; Yannick, Fouodji T; Zhang, Weiping; Du, Junjie

    2016-01-01

    Coupling electron beams carrying information into electronic units is fundamental in microelectronics. This requires precision manipulation of electron beams through a coupler with a good focusing ability. In graphene, the focusing of wide electron beams has been successfully demonstrated by a circular p-n junction. However, it is not favorable for information coupling since the focal length is so small that the focal spot locates inside the circular gated region, rather than in the background region. Here, we demonstrate that an array of gate-defined quantum dots, which has gradually changing lattice spacing in the direction transverse to propagation, can focus electrons outside itself, providing a possibility to make a coupler in graphene. The focusing effect can be understood as due to the gradient change of effective refractive indices, which are defined by the local energy band in a periodic potential. The strong focusing can be achieved by suitably choosing the lattice gradient and the layer number in the incident direction, offering an effective solution to precision manipulation of electron beams with wide electron energy range and high angular tolerance. PMID:27628099

  3. Flat-Lens Focusing of Electron Beams in Graphene

    Science.gov (United States)

    Tang, Yang; Cao, Xiyuan; Guo, Ran; Zhang, Yanyan; Che, Zhiyuan; Yannick, Fouodji T.; Zhang, Weiping; Du, Junjie

    2016-09-01

    Coupling electron beams carrying information into electronic units is fundamental in microelectronics. This requires precision manipulation of electron beams through a coupler with a good focusing ability. In graphene, the focusing of wide electron beams has been successfully demonstrated by a circular p-n junction. However, it is not favorable for information coupling since the focal length is so small that the focal spot locates inside the circular gated region, rather than in the background region. Here, we demonstrate that an array of gate-defined quantum dots, which has gradually changing lattice spacing in the direction transverse to propagation, can focus electrons outside itself, providing a possibility to make a coupler in graphene. The focusing effect can be understood as due to the gradient change of effective refractive indices, which are defined by the local energy band in a periodic potential. The strong focusing can be achieved by suitably choosing the lattice gradient and the layer number in the incident direction, offering an effective solution to precision manipulation of electron beams with wide electron energy range and high angular tolerance.

  4. Superconducting beam bending magnets at CERN

    CERN Multimedia

    1977-01-01

    The photo shows Gerhard Kesseler with the cyogenic vessels for one of the 10.8 Tesla-metre beam bending magnets. The magnet itself (not visible) is sitting inside the superinsukated helium vessel (white). The next larger shell and the biggest tubular structure (with the largest part behind the person) is the insulation vacuum tank. See CERN Courier 1970 pp. 228-229 CERN Courier 1973 pp. 144-145 Yellow Report CERN 78-03, 1978

  5. On possibility of high frequency electron beam scanning with application of focusing system for x-ray generation

    International Nuclear Information System (INIS)

    The article describes the electron beam scanning system in combination with electromagnetic focusing system. These systems find their application in different vacuum tube devices that provide the generation of X-ray radiation. Similar systems can be utilized in such fields as medicine, industry and defectoscopy. Electron tube system can be based on thermal or field emission cathodes. Scanning system is built up on two pair of electrical deflecting dipoles. The scanning can also be based on magnetic deflecting system. Beam focusing is achieved by the geometrical fea-tures of electrodes structure and electron lenses. Magnetic focusing can also be used for transversal focusing of the beam. The article describes the schemes of the unit with electron beam scanning and different methods of realization. Beam dynamics investigation in electromagnetic fields of the unit is considered

  6. Magnetic fields for transporting charged beams

    International Nuclear Information System (INIS)

    The transport of charged particle beams requires magnetic fields that must be shaped correctly and very accurately. During the last 20 years or so, many studies have been made, both analytically and through the use of computer programs, of various magnetic shapes that have proved to be useful. Many of the results for magnetic field shapes can be applied equally well to electric field shapes. A report is given which gathers together the results that have more general significance and would be useful in designing a configuration to produce a desired magnetic field shape. The field shapes studied include the fields in dipoles, quadrupoles, sextupoles, octupoles, septum magnets, combined-function magnets, and electrostatic septums. Where possible, empirical formulas are proposed, based on computer and analytical studies and on magnetic field measurements. These empirical formulas are often easier to use than analytical formulas and often include effects that are difficult to compute analytically. In addition, results given in the form of tables and graphs serve as illustrative examples. The field shapes studied include uniform fields produced by window-frame magnets, C-magnets, H-magnets, and cosine magnets; linear fields produced by various types of quadrupoles; quadratic and cubic fields produced by sextupoles and octupoles; combinations of uniform and linear fields; and septum fields with sharp boundaries

  7. Simulation of ion beam extraction and focusing system

    Institute of Scientific and Technical Information of China (English)

    B. A. Soliman; M. M. Abdelrahman; A. G. Helal; F. W. Abdelsalam

    2011-01-01

    The characteristics of ion beam extraction and focused to a volume as small as possible were investigated with the aid of computer code SIMION 3D version 7. This has been used to evaluate the extraction characteristics (accel-decel system) to generate an

  8. Design of Extended Depth-of-Focus Laser Beams Using Orthogonal Beam Expansions

    Directory of Open Access Journals (Sweden)

    Leonard Bergstein

    2005-06-01

    Full Text Available Laser beams with extended depth of focus have many practical applications, such as scanning printed bar codes. Previous work has concentrated on synthesizing such beams by approximating the nondiffracting Bessel beam solution to the wave equation. In this paper, we introduce an alternate novel synthesis method that is based on maintaining a minimum MTF value (contrast over the largest possible distance. To achieve this, the coefficients of an orthogonal beam expansion are sequentially optimized to this criterion. One of the main advantages of this method is that it can be easily generalized to noncircularly symmetrical beams by the appropriate choice of the beam expansion basis functions. This approach is found to be very useful for applications that involve scanning of the laser beam.

  9. Research and development of an electron beam focusing system for a high-brightness X-ray generator

    OpenAIRE

    Sakai, Takeshi; Ohsawa, Satoshi; Sakabe, Noriyoshi; Sugimura, Takashi; IKEDA, Mitsuo

    2010-01-01

    A new type of rotating anticathode X-ray generator, where an electron beam of up to 60 keV irradiates the inner surface of a U-shaped Cu anticathode, has achieved a beam brilliance of 130 kW mm−2 (at 2.3 kW). A higher-flux electron beam is expected from simulation by optimizing the geometry of a combined-function-type magnet instead of the fringing field of the bending magnet. In order to minimize the size of the X-ray source the electron beam has been focused over a short distance by a new c...

  10. Nanopillar growth by focused helium ion-beam-induced deposition

    Energy Technology Data Exchange (ETDEWEB)

    Chen Ping; Salemink, Huub W M; Alkemade, Paul F A [Kavli Institute of Nanoscience, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft (Netherlands); Veldhoven, Emile van; Maas, Diederik J [TNO Science and Industry, Stieltjesweg 1, 2628 CK Delft (Netherlands); Sanford, Colin A [Carl Zeiss SMT, Inc., One Corporation Way, Peabody, MA 01960 (United States); Smith, Daryl A; Rack, Philip D, E-mail: p.f.a.alkemade@tudelft.nl [Department of Material Science and Engineering, University of Tennessee, Knoxville, TN 37996-2200 (United States)

    2010-11-12

    A 25 keV focused helium ion beam has been used to grow PtC nanopillars on a silicon substrate by beam-induced decomposition of a (CH{sub 3}){sub 3}Pt(C{sub P}CH{sub 3}) precursor gas. The ion beam diameter was about 1 nm. The observed relatively high growth rates suggest that electronic excitation is the dominant mechanism in helium ion-beam-induced deposition. Pillars grown at low beam currents are narrow and have sharp tips. For a constant dose, the pillar height decreases with increasing current, pointing to depletion of precursor molecules at the beam impact site. Furthermore, the diameter increases rapidly and the total pillar volume decreases slowly with increasing current. Monte Carlo simulations have been performed with realistic values for the fundamental deposition processes. The simulation results are in good agreement with experimental observations. In particular, they reproduce the current dependences of the vertical and lateral growth rates and of the volumetric deposition efficiency. Furthermore, the simulations reveal that the vertical pillar growth is due to type-1 secondary electrons and primary ions, while the lateral outgrowth is due to type-2 secondary electrons and scattered ions.

  11. Nanopillar growth by focused helium ion-beam-induced deposition

    International Nuclear Information System (INIS)

    A 25 keV focused helium ion beam has been used to grow PtC nanopillars on a silicon substrate by beam-induced decomposition of a (CH3)3Pt(CPCH3) precursor gas. The ion beam diameter was about 1 nm. The observed relatively high growth rates suggest that electronic excitation is the dominant mechanism in helium ion-beam-induced deposition. Pillars grown at low beam currents are narrow and have sharp tips. For a constant dose, the pillar height decreases with increasing current, pointing to depletion of precursor molecules at the beam impact site. Furthermore, the diameter increases rapidly and the total pillar volume decreases slowly with increasing current. Monte Carlo simulations have been performed with realistic values for the fundamental deposition processes. The simulation results are in good agreement with experimental observations. In particular, they reproduce the current dependences of the vertical and lateral growth rates and of the volumetric deposition efficiency. Furthermore, the simulations reveal that the vertical pillar growth is due to type-1 secondary electrons and primary ions, while the lateral outgrowth is due to type-2 secondary electrons and scattered ions.

  12. Program Models A Laser Beam Focused In An Aerosol Spray

    Science.gov (United States)

    Barton, J. P.

    1996-01-01

    Monte Carlo analysis performed on packets of light. Program for Analysis of Laser Beam Focused Within Aerosol Spray (FLSPRY) developed for theoretical analysis of propagation of laser pulse optically focused within aerosol spray. Applied for example, to analyze laser ignition arrangement in which focused laser pulse used to ignite liquid aerosol fuel spray. Scattering and absorption of laser light by individual aerosol droplets evaluated by use of electromagnetic Lorenz-Mie theory. Written in FORTRAN 77 for both UNIX-based computers and DEC VAX-series computers. VAX version of program (LEW-16051). UNIX version (LEW-16065).

  13. Beam dynamics of alternating-phase-focused linac

    CERN Document Server

    Iwata, Y; Kapin, V

    2004-01-01

    A simple method to find an array of synchronous phases for alternating-phase-focused (APF) linacs is presented. The phase array is described with a smooth function having free parameters. With a set of the parameters, a simulation on the beam dynamics was made and distributions of the six-dimensional phase spaces were calculated for each set of the parameters. The parameters were varied, and numbers of the simulations have been performed. An optimum set of the parameters were determined so that the simulations of the beam dynamics yield large acceptances and small emittances of the extracted beams. Since the APF linac can provide both axial and radial stability of beams just with the rf acceleration-field, no additional focusing element inside of drift tubes are necessary. Comparing with conventional linacs having focusing elements, it has advantage in construction and operation costs as well as its acceleration rate. Therefore, the APF linacs would be suited for an injector of medical synchrotrons. A practic...

  14. Molecule-by-Molecule Writing Using a Focused Electron Beam

    DEFF Research Database (Denmark)

    Van Dorp, Willem F.; Zhang, Xiaoyan; Feringa, Ben L.;

    2012-01-01

    on graphene can be followed molecule-by-molecule with FEBID. The results show that mechanisms that are inherent to the process inhibit a further increase in control over the process. Hence, our results present the resolution limit of (electron) optical lithography techniques. The writing of isolated...... atoms also be written with an electron beam? We verify this with focused electron-beam-induced deposition (FEBID), a direct-write technique that has the current record for the smallest feature written by (electron) optical lithography. We show that the deposition of an organometallic precursor...

  15. Gaussian laser beam in a magnetized plasma. 2

    International Nuclear Information System (INIS)

    Properties of a laser beam propagating perpendicular to the external magnetic field in a plasma are investigated theoretically. The beam is represented by a Helmholtz equation in almost all plasma parameter space. For the upper hybrid wave region the wave equation turns to a hyperbolic partial differential equation. It is shown that both equations can be exactly solved by using a method of separation of variables and that solutions having Gaussian profiles lateral to the propagation direction are obtained. An appreciable difference between two solutions appears in their phase factors. Owing to the asymmetry of the configuration around the axis of wave propagation the cross sections of beams take shapes of ellipse and each beam has two different focus points. (author)

  16. Research and development of an electron beam focusing system for a high-brightness X-ray generator

    International Nuclear Information System (INIS)

    In order to minimize the size of the X-ray source for a U-shaped rotating anticathode X-ray generator, the electron beam is focused over a short distance by a combined-function bending magnet. Simulation predicts that the beam brightness will reach almost 500 kW mm−2 for a 120 keV/75 mA beam. A new type of rotating anticathode X-ray generator, where an electron beam of up to 60 keV irradiates the inner surface of a U-shaped Cu anticathode, has achieved a beam brilliance of 130 kW mm−2 (at 2.3 kW). A higher-flux electron beam is expected from simulation by optimizing the geometry of a combined-function-type magnet instead of the fringing field of the bending magnet. In order to minimize the size of the X-ray source the electron beam has been focused over a short distance by a new combined-function bending magnet, whose geometrical shape was determined by simulation using the Opera-3D, General Particle Tracer and CST-STUDIO codes. The result of the simulation clearly shows that the role of combined functions in both the bending and the steering magnets is important for focusing the beam to a small size. FWHM sizes of the beam are predicted by simulation to be 0.45 mm (horizontal) and 0.05 mm (vertical) for a 120 keV/75 mA beam, of which the effective brilliance is about 500 kW mm−2 on the supposition of a two-dimensional Gaussian distribution. High-power tests have begun using a high-voltage 120 kV/75 mA power supply for the X-ray generator instead of 60 kV/100 mA. The beam focus size on the target will be verified in the experiments

  17. Microfabricated Ion Beam Drivers for Magnetized Target Fusion

    Science.gov (United States)

    Persaud, Arun; Seidl, Peter; Ji, Qing; Ardanuc, Serhan; Miller, Joseph; Lal, Amit; Schenkel, Thomas

    2015-11-01

    Efficient, low-cost drivers are important for Magnetized Target Fusion (MTF). Ion beams offer a high degree of control to deliver the required mega joules of driver energy for MTF and they can be matched to several types of magnetized fuel targets, including compact toroids and solid targets. We describe an ion beam driver approach based on the MEQALAC concept (Multiple Electrostatic Quadrupole Array Linear Accelerator) with many beamlets in an array of micro-fabricated channels. The channels consist of a lattice of electrostatic quadrupoles (ESQ) for focusing and of radio-frequency (RF) electrodes for ion acceleration. Simulations with particle-in-cell and beam envelope codes predict >10x higher current densities compared to state-of-the-art ion accelerators. This increase results from dividing the total ion beam current up into many beamlets to control space charge forces. Focusing elements can be biased taking advantage of high breakdown electric fields in sub-mm structures formed using MEMS techniques (Micro-Electro-Mechanical Systems). We will present results on ion beam transport and acceleration in MEMS based beamlets. Acknowledgments: This work is supported by the U.S. DOE under Contract No. DE-AC02-05CH11231.

  18. Optimal focusing conditions of lenses using Gaussian beams

    Science.gov (United States)

    Franco, Juan Manuel; Cywiak, Moisés; Cywiak, David; Mourad, Idir

    2016-07-01

    By using the analytical equations of the propagation of Gaussian beams in which truncation exhibits negligible consequences, we describe a method that uses the value of the focal length of a focusing lens to classify its focusing performance. We show that for different distances between a laser and a focusing lens there are different planes where best focusing conditions can be obtained and we demonstrate how the value of the focal length impacts the lens focusing properties. To perform the classification we introduce the term delimiting focal length. As the value of the focal length used in wave propagation theory is nominal and difficult to measure accurately, we describe an experimental approach to calculate its value matching our analytical description. Finally, we describe possible applications of the results for characterizing Gaussian sources, for measuring focal lengths and/or alternatively for characterizing piston-like movements.

  19. Proton beam focusing with a radial applied B-field ion diode on PBFA II

    International Nuclear Information System (INIS)

    Ion beam focusing experiments have been performed on PBFA II using a 15-cm-radius version of an ion diode used on PROTO I. A pair of B-field coils located in the cathodes supply the 2 T axial B-field used to insulate the 1.7 cm anode-cathode gap from electron loss. Anode B-field coils adjust the level of magnetic insulation along the anode surface and control the canonical angular momentum of the bean originating from surface flashover anode sources. The diode uses a cylindrical, 12.5-cm-radius beam current neutralizing gas cell with 2-μm-thick mylar window and 3 torr argon gas fill. Diagnostic measurements presented include the total current, ion current, and voltage at the diode, nuclear activation, witness plate damage, proton beam energy spectrum, and spatial beam profiles at 4 and 0 cm radius

  20. Effects on focused ion beam irradiation on MOS transistors

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, A.N.; Peterson, K.A.; Fleetwood, D.M.; Soden, J.M.

    1997-04-01

    The effects of irradiation from a focused ion beam (FIB) system on MOS transistors are reported systematically for the first time. Three MOS transistor technologies, with 0.5, 1, and 3 {mu}m minimum feature sizes and with gate oxide thicknesses ranging from 11 to 50 nm, were analyzed. Significant shifts in transistor parameters (such as threshold voltage, transconductance, and mobility) were observed following irradiation with a 30 keV Ga{sup +} focused ion beam with ion doses varying by over 5 orders of magnitude. The apparent damage mechanism (which involved the creation of interface traps, oxide trapped charge, or both) and extent of damage were different for each of the three technologies investigated.

  1. Direct deposition of gold on silicon with focused ion beams

    Energy Technology Data Exchange (ETDEWEB)

    Nebiker, P.W.; Doebeli, M. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Muehle, R. [Eidgenoessische Technische Hochschule, Zurich (Switzerland)

    1997-09-01

    Irradiation with ions at very low energies (below 500 eV) no longer induces a removal of substrate material, but the ions are directly deposited on the surface. In this way, gold has been deposited on silicon with focused ion beam exposure and the properties of the film have been investigated with atomic force microscopy and Auger electron spectroscopy. (author) 3 figs., 1 ref.

  2. Surface plasmon interference excited by tightly focused laser beams.

    Energy Technology Data Exchange (ETDEWEB)

    Bouhelier, A.; Ignatovich, F.; Bruyant, A.; Huang, C.; Colas des Francs, G.; Weeber, J.-C.; Dereux, A.; Wiederrecht, G. P.; Novotny, L.; Center for Nanoscale Materials; Univ de Bourgogne; Univ. of Rochester; Univ Technologique de Troyes

    2007-09-01

    We show that interfering surface plasmon polaritons can be excited with a focused laser beam at normal incidence to a plane metal film. No protrusions or holes are needed in this excitation scheme. Depending on the axial position of the focus, the intensity distribution on the metal surface is either dominated by interferences between counterpropagating plasmons or by a two-lobe pattern characteristic of localized surface plasmon excitation. Our experiments can be accurately explained by use of the angular spectrum representation and provide a simple means for locally exciting standing surface plasmon polaritons.

  3. Strong self-focusing of a cosh-Gaussian laser beam in collisionless magneto-plasma under plasma density ramp

    International Nuclear Information System (INIS)

    The effect of plasma density ramp on self-focusing of cosh-Gaussian laser beam considering ponderomotive nonlinearity is analyzed using WKB and paraxial approximation. It is noticed that cosh-Gaussian laser beam focused earlier than Gaussian beam. The focusing and de-focusing nature of the cosh-Gaussian laser beam with decentered parameter, intensity parameter, magnetic field, and relative density parameter has been studied and strong self-focusing is reported. It is investigated that decentered parameter “b” plays a significant role for the self-focusing of the laser beam as for b=2.12, strong self-focusing is seen. Further, it is observed that extraordinary mode is more prominent toward self-focusing rather than ordinary mode of propagation. For b=2.12, with the increase in the value of magnetic field self-focusing effect, in case of extraordinary mode, becomes very strong under plasma density ramp. Present study may be very useful in the applications like the generation of inertial fusion energy driven by lasers, laser driven accelerators, and x-ray lasers. Moreover, plasma density ramp plays a vital role to enhance the self-focusing effect

  4. Strong self-focusing of a cosh-Gaussian laser beam in collisionless magneto-plasma under plasma density ramp

    Energy Technology Data Exchange (ETDEWEB)

    Nanda, Vikas; Kant, Niti, E-mail: nitikant@yahoo.com [Department of Physics, Lovely Professional University, G. T. Road, Phagwara, Punjab 144411 (India)

    2014-07-15

    The effect of plasma density ramp on self-focusing of cosh-Gaussian laser beam considering ponderomotive nonlinearity is analyzed using WKB and paraxial approximation. It is noticed that cosh-Gaussian laser beam focused earlier than Gaussian beam. The focusing and de-focusing nature of the cosh-Gaussian laser beam with decentered parameter, intensity parameter, magnetic field, and relative density parameter has been studied and strong self-focusing is reported. It is investigated that decentered parameter “b” plays a significant role for the self-focusing of the laser beam as for b=2.12, strong self-focusing is seen. Further, it is observed that extraordinary mode is more prominent toward self-focusing rather than ordinary mode of propagation. For b=2.12, with the increase in the value of magnetic field self-focusing effect, in case of extraordinary mode, becomes very strong under plasma density ramp. Present study may be very useful in the applications like the generation of inertial fusion energy driven by lasers, laser driven accelerators, and x-ray lasers. Moreover, plasma density ramp plays a vital role to enhance the self-focusing effect.

  5. A spatially shifted beam approach to subwavelength focusing

    CERN Document Server

    Markley, Loic; Eleftheriades, George V

    2008-01-01

    With the development of negative-refractive-index metamaterials over the last decade, the challenge of subwavelength focusing has received considerable attention. The difficulties associated with image degradation from losses and with scalability to high frequencies led to alternative near-field techniques being explored. In this paper, we propose a slotted metal screen that focuses the near-field above the limit imposed by diffraction and furthermore, is easily scaled from microwave to Terahertz frequencies and beyond. Using subwavelength spaced dipole slots with induced currents of alternating signs, the superposition of shifted beam patterns produces a focus that can be tightened beyond the diffraction limit. An analytical model is developed that agrees very well with full-wave simulations and is corroborated by experimental results at microwave frequencies.

  6. Imaging Nanophotonic Modes of Microresonators using a Focused Ion Beam

    CERN Document Server

    Twedt, Kevin A; Davanco, Marcelo; Srinivasan, Kartik; McClelland, Jabez J; Aksyuk, Vladimir A

    2016-01-01

    Optical microresonators have proven powerful in a wide range of applications, including cavity quantum electrodynamics, biosensing, microfludics, and cavity optomechanics. Their performance depends critically on the exact distribution of optical energy, confined and shaped by the nanoscale device geometry. Near-field optical probes can image this distribution, but the physical probe necessarily perturbs the near field, which is particularly problematic for sensitive high quality factor resonances. We present a new approach to mapping nanophotonic modes that uses a controllably small and local optomechanical perturbation introduced by a focused lithium ion beam. An ion beam (radius about 50 nm) induces a picometer-scale dynamic deformation of the resonator surface, which we detect through a shift in the optical resonance wavelength. We map five modes of a silicon microdisk resonator (Q > 20,000) with both high spatial and spectral resolution. Our technique also enables in-situ observation of ion implantation d...

  7. Transverse centroid oscillations in solenoidially focused beam transport lattices

    International Nuclear Information System (INIS)

    Transverse centroid oscillations are analyzed for a beam in a solenoid transport lattice. Linear equations of motion are derived that describe small-amplitude centroid oscillations induced by displacement and rotational misalignments of the focusing solenoids in the transport lattice, dipole steering elements, and initial centroid offset errors. These equations are analyzed in a local rotating Larmor frame to derive complex-variable 'alignment functions' and 'bending functions' that efficiently describe the characteristics of the centroid oscillations induced by both mechanical misalignments of the solenoids and dipole steering elements. The alignment and bending functions depend only on the properties of the ideal lattice in the absence of errors and steering, and have associated expansion amplitudes set by the misalignments and steering fields, respectively. Applications of this formulation are presented for statistical analysis of centroid oscillations, calculation of actual lattice misalignments from centroid measurements, and optimal beam steering.

  8. Experimental and numerical studies of sheet electron beam propagation through a planar wiggler magnet

    International Nuclear Information System (INIS)

    Detailed experimental studies on sheet relativistic electron beam propagation through a long planar wiggler are reported and compared with numerical simulations. The planar wiggler has 56 periods with a period of 9.6 mm. Typically, the wiggler field peak amplitude is 5 kG. The experimental efforts have been focused on control of the deviation of the beam toward the side edge of the planar wiggler along the wide transverse direction. It is found that a suitably tapered magnetic field configuration at the wiggler entrance can considerably reduce the rate of the deviation. The effects of the following techniques on beam transport efficiency are also discussed: side focusing, beam transverse velocity tuning at the wiggler entrance, and beam spread limiting. High beam transport efficiency (almost 100%) of a 15 A beam has been obtained in some cases. The results are relevant to development of a free electron laser amplifier for application to stabilizing and heating of plasma in magnetic fusion research

  9. Diamond Processing by Focused Ion Beam - Surface Damage and Recovery

    CERN Document Server

    Bayn, Igal; Cytermann, Catherine; Meyler, Boris; Richter, Vladimir; Salzman, Joseph; Kalish, Rafi

    2011-01-01

    The Nitrogen Vacancy color center (NV-) in diamond is of great interest for novel photonic applications. Diamond nano-photonic structures are often implemented using Focused-Ion-Beam (FIB) processing, leaving a damaged surface which has a detrimental effect on the color center luminescence. The FIB processing effect on single crystal diamond surfaces and their photonic properties is studied by Time of Flight Secondary Ion Mass Spectrometry (TOF-SIMS) and photoluminescence (PL). Exposing the processed surface to hydrogen plasma, followed by chemical etching, drastically decreases implanted Ga concentration, resulting in a recovery of the NV- photo-emission and in a significant increase of the NV-/NV0 ratio.

  10. Industrial perspective on focused electron beam-induced processes

    Energy Technology Data Exchange (ETDEWEB)

    Bret, Tristan; Hofmann, Thorsten; Edinger, Klaus [Betriebsstaette Rossdorf, Carl Zeiss SMS GmbH, Rossdorf (Germany)

    2014-12-15

    After a short overview of the historical developments of the technique of gas-assisted focused electron beam-induced processing (mostly deposition and etching), this paper deals with the applications of this technology to photolithographic mask repair. A commented list of results is shown on different mask types, for different types of defects, and at different node generations. The scope of this article is double: summarize the state of the art in a fast-paced highly specific industrial environment driven by ''Moore's law'' and feedback to academic researchers some technologically relevant directions for further investigations. (orig.)

  11. Optical fiber sensors fabricated by the focused ion beam technique

    DEFF Research Database (Denmark)

    Yuan, Scott Wu; Wang, Fei; Bang, Ole

    2012-01-01

    Focused ion beam (FIB) is a highly versatile technique which helps to enable next generation of lab-on-fiber sensor technologies. In this paper, we demonstrate the use application of FIB to precisely mill the fiber taper and end facet of both conventional single mode fiber (SMF) and photonic...... crystal fiber (PCF). Using this technique we fabricate a highly compact fiber-optic Fabry-Pérot (FP) refractive index sensor near the tip of fiber taper, and a highly sensitive in-line temperature sensor in PCF. We also demonstrate the potential of using FIB to selectively fill functional fluid...

  12. Schlieren photography of plasma focus discharges with decreased magnetic insulation

    International Nuclear Information System (INIS)

    The dynamics of 6 kJ plasma focus discharges in deuterium at 5 Torr, with a 10% decrease of the magnetic insulation at the breech was monitored with schlieren photography and other diagnostic methods. The resolution on the schlieren image was of 33 line-pairs per mm, and the probed range of electron density gradients, with integration along the path of the ruby laser beam, was between 5 x 1018 cm-3 and 3 x 1020 cm-3. The duration of the typical Q-switched ruby laser pulse was 10 ns. Double and triple pulse generation made the measurement of the current sheath velocity possible. The average radial velocity was 1.2 x 107 cm/s in the interval (-112 ns, -88 ns), the average axial velocity 5 x 106 cm/s and 8 x 106 cm/s in the intervals (-4 ns, +96 ns) and (+96 ns, +126 ns), respectively. The timing is referred to the sharp peak (t = 0) in the electrode current (1) signal | dI/dt |. The data are compared with those from discharges with normal level (no 10% decrease) of magnetic insulation at the breech. The current sheath fine structure in the region of high density gradient is also monitored

  13. Magnetic focusing in triangular electron billiards

    DEFF Research Database (Denmark)

    Bøggild, Peter; Kristensen, A.; Lindelof, Poul Erik

    1999-01-01

    focusing spectrum compared to the case of a perpendicular injection angle. From numerical and analytical analysis, we confirm that the quenching is a fundamental geometrical effect, and identify two mechanisms responsible for the anomaly. The focusing spectrum of the considered skewed geometry is...

  14. Laser and focused ion beam combined machining for micro dies.

    Science.gov (United States)

    Yoshida, Y; Okazaki, W; Uchida, T

    2012-02-01

    We have developed a laser and focused ion beam (FIB) compound process for press mold dies of a micro lens array (MLA) and a micro needle array (MNA) in a glassy carbon (GC). The press mold die of the MLA was roughly fabricated by UV-YAG laser. After this process, we finished this surface by scanning FIB. As a result, higher accuracy and good roughness of surface profile can be realized. An optical glass is used to confirm the shape of lens. Moreover, we fabricated 6 × 6 through-holes in the GC by the spiral drilling in addition to the focus position movement of the UV laser for press mold die of the MNA. After the FIB process, we were able to make the needle die of surface and hole wall roughness less than 0.9 μm. A silicon rubber is used to confirm the shape of the holes.

  15. Light beams focusing in periodically non-uniform crystalline medium

    Directory of Open Access Journals (Sweden)

    S.N.Kurilkina

    2002-03-01

    Full Text Available In the present paper the peculiarities of propagation and diffraction of optical waves in the crystalline periodically non-uniform media are considered. The dependence of light beam divergence in the crystal on curvatures of wave vector surface is obtained. It is shown, that presence of the periodic non-uniformity of the crystal and natural anisotropy lead to essential deformation of wave vector surface, namely, to the appearance of local regions with negative curvature and, hence, to the effect of light focusing in corresponding directions. The application of uniform electric field may intensify the light focusing. The crystalline diffraction lenses are proposed which are controlled by electric field and variation of incident light polarization.

  16. DESIGN OF BEAM-EXTRACTION SEPTUM MAGNET FOR THE SNS.

    Energy Technology Data Exchange (ETDEWEB)

    TSOUPAS,N.; LEE,Y.Y.; RANK,J.; TUOZZOLO,J.

    2001-06-18

    The beam-extraction process from the SNS accumulator ring [1,2] requires a Lambertson septum magnet. In this paper we discuss the geometrical and magnetic field requirements of the magnet and present results obtained from two and three dimensional magnetic field calculations that shows the field quality in the regions of interest of the septum magnet.

  17. Main Magnetic Focus Ion Source: II. The first investigations at 10 keV

    CERN Document Server

    Ovsyannikov, V P

    2015-01-01

    The basic principles of design for the compact ion source of new generation are presented. The device uses the local ion trap created by the axial electron beam rippled in a thick magnetic lens. In accordance with this feature, the ion source is given the name main magnetic focus ion source. The experimental evidences for the production of Ir$^{59+}$, Xe$^{44+}$, and Ar$^{16+}$ ions are obtained. The control over depth of the local ion trap is shown to be feasible.

  18. Focusing Light Beams To Improve Atomic-Vapor Optical Buffers

    Science.gov (United States)

    Strekalov, Dmitry; Matsko, Andrey; Savchenkov, Anatoliy

    2010-01-01

    Specially designed focusing of light beams has been proposed as a means of improving the performances of optical buffers based on cells containing hot atomic vapors (e.g., rubidium vapor). There is also a companion proposal to improve performance by use of incoherent optical pumping under suitable conditions. Regarding the proposal to use focusing: The utility of atomic-vapor optical buffers as optical storage and processing devices has been severely limited by nonuniform spatial distributions of intensity in optical beams, arising from absorption of the beams as they propagate in atomic-vapor cells. Such nonuniformity makes it impossible to optimize the physical conditions throughout a cell, thereby making it impossible to optimize the performance of the cell as an optical buffer. In practical terms simplified for the sake of brevity, "to optimize" as used here means to design the cell so as to maximize the group delay of an optical pulse while keeping the absorption and distortion of the pulse reasonably small. Regarding the proposal to use incoherent optical pumping: For reasons too complex to describe here, residual absorption of light is one of the main impediments to achievement of desirably long group delays in hot atomic vapors. The present proposal is directed toward suppressing residual absorption of light. The idea of improving the performance of slow-light optical buffers by use of incoherent pumping overlaps somewhat with the basic idea of Raman-based slow-light systems. However, prior studies of those systems did not quantitatively answer the question of whether the performance of an atomic vapor or other medium that exhibits electromagnetically induced transparency (EIT) with Raman gain is superior to that of a medium that exhibits EIT without Raman gain.

  19. EDITORIAL: Focus on Dilute Magnetic Semiconductors FOCUS ON DILUTE MAGNETIC SEMICONDUCTORS

    Science.gov (United States)

    Chambers, Scott A.; Gallagher, Bryan

    2008-05-01

    This focus issue of New Journal of Physics is devoted to the materials science of dilute magnetic semiconductors (DMS). A DMS is traditionally defined as a diamagnetic semiconductor doped with a few to several atomic per cent of some transition metal with unpaired d electrons. Several kinds of dopant-dopant interactions can in principle couple the dopant spins leading to a ferromagnetic ground state in a dilute magnetic system. These include superexchange, which occurs principally in oxides and only between dopants with one intervening oxygen, and double exchange, in which dopants of different formal charges exchange an electron. In both of these mechanisms, the ferromagnetic alignment is not critically dependent on free carriers in the host semiconductor because exchange occurs via bonds. A third mechanism, discovered in the last few years, involves electrons associated with lattice defects that can apparently couple dopant spins. This mechanism is not well understood. Finally, the most desirable mechanism is carrier-mediated exchange interaction in which the dopant spins are coupled by itinerant electrons or holes in the host semiconductor. This mechanism introduces a fundamental link between magnetic and electrical transport properties and offers the possibility of new spintronic functionalities. In particular electrical gate control of ferromagnetism and the use of spin polarized currents to carry signals for analog and digital applications. The spin light emitting diode is a prototypical device of this kind that has been extensively used to characterize the extent of spin polarization in the active light emitting semiconductor heterostructure. The prototypical carrier mediated ferromagnetic DMS is Mn-doped GaAs. This and closely related narrow gap III-V materials have been very extensively studied. Their properties are generally quite well understood and they have led to important insights into fundamental properties of ferromagnetic systems with strong spin

  20. Single-impulse magnetic focusing of launched cold atoms

    CERN Document Server

    Pritchard, M J; Smith, D A; Hughes, I G; Pritchard, Matthew J; Arnold, Aidan S; Smith, David A; Hughes, Ifan G

    2004-01-01

    We have theoretically investigated the focusing of a launched cloud of cold atoms. Time-dependent spatially-varying magnetic fields are used to impart impulses leading to a three-dimensional focus of the launched cloud. We discuss possible coil arrangements for a new focusing regime: isotropic 3D focusing of atoms with a single-impulse magnetic lens. We investigate focusing aberrations and find that, for typical experimental parameters, the widely used assumption of a purely harmonic lens is often inaccurate. The baseball lens offers the best possibility for isotropically focusing a cloud of weak-field-seeking atoms in 3D.

  1. Intense ion beam production in a ballistic focusing diode

    International Nuclear Information System (INIS)

    The results of experimental investigation of intense ion beam (IIB) production in a coaxial magnetic insulated diode are presented. The diode consists of a coaxial external anode of 94-120 mm diameter and internal cathode with longitudinal slits of 12 mm width. Two types of insulating magnetic fields: Bsub(Z)-field created by external solenoid and Bsub(o)-pulse field obtained in the course of current transmission from the external battery along the cathode. In the regime with Bsub(Z)=0,42 T the IID amplitudes for anodes from teflon, copper, lead have reached 3,7, 1, 1,3 kA and densities - 330 A/cm2, 87 A/cm2, 114 A/cm2, respectively. In the regime with Bsub(o)=1 T maximum IIB density on the cathode surface has reached 220 A/cm2, IIB maximum current constitutes 10 and 11 kA for the current getting to the cathode ribs and penetrating into slits, respectively. The production efficiency constitutes 67%

  2. Light ion beams generation in dense plasma focus

    International Nuclear Information System (INIS)

    The high energy deuterons and protons in a Mather type plasma focus device were measured by nuclear activation techniques. The radioactivity induced in graphite, aluminum and copper targets provided the deuteron intensity, energy spectra and angular dependence. High energy protons were measured by cellulose nitrate particle track detectors. The plasma focus device was operated at 30 kV for a stored energy of 18 kJ at 1.5 Torr D2 (low pressure mode), and 5 Torr D2 (high pressure mode). The yield ratio of N-13 and Al-28 showed the mean deuteron energy of 1.55 MeV under low pressure mode and of 1.44 MeV under high pressure mode. The deuteron energy spectra were measured by the stacks of 10 aluminum foils, and consisted of two components as well as the proton energy spectra measured by CN film technique. The angular spread of deuteron beam was within 30 degree under low pressure mode. Under high pressure mode, the distribution showed multi-structure, and two peaks were observed at the angle smaller than 20 degree and at 60 degree. The protons with energy more than 770 keV were directed in the angle of 10 degree. The high energy electron beam was also observed. A three-channel ruby laser holographic interferometry was used to see the spatial and temporal location of the generation of high energy ions. The ion temperature in plasma focus was estimated from D + He3 mixture gas experiment. (Kato, T.)

  3. Focused-electron-beam-induced-deposited cobalt nanopillars for nanomagnetic logic.

    Science.gov (United States)

    Sharma, N; van Mourik, R A; Yin, Y; Koopmans, B; Parkin, S S P

    2016-04-22

    Nanomagnetic logic (NML) intends to alleviate problems of continued miniaturization of CMOS-based electronics, such as energy dissipation through heat, through advantages such as low power operation and non-volatile magnetic elements. In line with recent breakthroughs in NML with perpendicularly magnetized elements formed from thin films, we have fabricated NML inverter chains from Co nanopillars by focused electron beam induced deposition (FEBID) that exhibit shape-induced perpendicular magnetization. The flexibility of FEBID allows optimization of NML structures. Simulations reveal that the choice of nanopillar dimensions is critical to obtain the correct antiferromagnetically coupled configuration. Experiments carrying the array through a clocking cycle using the Oersted field from an integrated Cu wire show that the array responds to the clocking cycle. PMID:26941232

  4. 磁流体薄片中聚焦激光束对交流磁场的相位独立响应%Phase-independent response of a focused laser beam on a ferrofluid slab to A. C. magnetic field

    Institute of Scientific and Technical Information of China (English)

    袁绥华; 李洪杰; 张广溢

    2002-01-01

    报导了磁流体薄片中聚焦激光束在探测50Hz交流磁场时产生与磁场相位无关响应的效应.聚焦于并通过磁流体薄片的633nm激光束的偏转角仅与交流磁场的幅度相关.为了探寻其机理,还研究了磁流体中聚焦激光束对开/关磁场或激光的瞬态响应.提出了基于磁熵守恒的磁流体中磁性粒子密度再分布正反馈模型来解释这一效应.这一模型也可以预见磁流体中一种磁-热失稳现象.%The effect of phase-independent response of a laser beam focused on a ferrofluid slab in sensing the 50 Hz magnetic field was reported.The refraction angles of a laser beam of 633nm wave-length focused on a slab of ferrofluid only respond to the magnitude of the magnetic field. Transient responses of the ferrofluid to switching magnetic field or light on/off were also measured to search the mechanism of the effect. A model of magnetic entropy conservation-based positive feedback in density redistributions of the magnetic particles in the ferrofluid is proposed for explaining this effect. This model also predicts a magneto-thermal instability in the ferrofluid.

  5. Properties of dark solitons under SBS in focused beams

    Science.gov (United States)

    Bel'dyugin, Igor'M.; Erokhin, A. I.; Efimkov, V. F.; Zubarev, I. G.; Mikhailov, S. I.

    2012-12-01

    Using the method of four-wave probing of the waist of the laser beam focused into the bulk of a short active medium (L ll τc, where L is the length of the active medium, τ is the pulse duration, and c is the speed of light), we have studied the dynamics of the behaviour of a dark soliton, appearing upon a jump of the input Stokes signal phase by about π under SBS. The computer simulation has shown that when spontaneous noises with the gain increment Γ, exceeding the self-reflection threshold by 2 - 3 times, are generated, the dark soliton propagates along the interaction region for the time t ≈ T2Γth/2, where T2 is the the lifetime of acoustic phonons, and Γth = 25 - 30 is the stationary threshold gain increment.

  6. Transverse Centroid Oscillations in Solenoidially Focused Beam Transport Lattices

    Energy Technology Data Exchange (ETDEWEB)

    Lund, S M; Wootton, C J; Lee, E P

    2008-08-01

    Linear equations of motion are derived that describe small-amplitude centroid oscillations induced by displacement and rotational misalignments of the focusing solenoids in the transport lattice, dipole steering elements, and initial centroid offset errors. These equations are analyzed in a local rotating Larmor frame to derive complex-variable 'alignment functions' and 'bending functions' that efficiently describe the characteristics of the centroid oscillations induced by mechanical misalignments of the solenoids and dipole steering elements. The alignment and bending functions depend only on properties of the ideal lattice in the absence of errors and steering and have associated expansion amplitudes set by the misalignments and steering fields. Applications of this formulation are presented for statistical analysis of centroid deviations, calculation of actual lattice misalignments from centroid measurements, and optimal beam steering.

  7. Transverse centroid oscillations in solenoidially focused beam transport lattices

    Energy Technology Data Exchange (ETDEWEB)

    Lund, Steven M.; Wootton, Christopher J.; Lee, Edward P.

    2008-08-01

    Linear equations of motion are derived that describe small-amplitude centroid oscillations induced by displacement and rotational misalignments of the focusing solenoids in the transport lattice, dipole steering elements, and initial centroid offset errors. These equations are analyzed in a local rotating Larmor frame to derive complex-variable"alignment functions" and"bending functions" that efficiently describe the characteristics of the centroid oscillations induced by mechanical misalignments of the solenoids and dipole steering elements. The alignment and bending functions depend only on properties of the ideal lattice in the absence of errors and steering and have associated expansion amplitudes set by the misalignments and steering fields. Applications of this formulation are presented for statistical analysis of centroid deviations, calculation of actual lattice misalignments from centroid measurements, and optimal beam steering.

  8. Atomic-scale thermocapillary flow in focused ion beam milling

    Energy Technology Data Exchange (ETDEWEB)

    Das, K.; Johnson, H. T.; Freund, J. B., E-mail: jbfreund@illinois.edu [Mechanical Science and Engineering and Aerospace Engineering, University of Illinois at Urbana–Champaign, 1206 West Green Street MC-244, Urbana, Illinois 61801 (United States)

    2015-05-15

    Focused ion beams provide a means of nanometer-scale manufacturing and material processing, which is used for applications such as forming nanometer-scale pores in thin films for DNA sequencing. We investigate such a configuration with Ga{sup +} bombardment of a Si thin-film target using molecular dynamics simulation. For a range of ion intensities in a realistic configuration, a recirculating melt region develops, which is seen to flow with a symmetrical pattern, counter to how it would flow were it driven by the ion momentum flux. Such flow is potentially important for the shape and composition of the formed structures. Relevant stress scales and estimated physical properties of silicon under these extreme conditions support the importance thermocapillary effects. A flow model with Marangoni forcing, based upon the temperature gradient and geometry from the atomistic simulation, indeed reproduces the flow and thus could be used to anticipate such flows and their influence in applications.

  9. Introduction to focused ion beams instrumentation, theory, techniques and practice

    CERN Document Server

    Giannuzzi, Lucille A

    2005-01-01

    The focused ion beam (FIB) instrument has experienced an intensive period of maturation since its inception. Numerous new techniques and applications have been brought to fruition, and over the past few years, the FIB has gained acceptance as more than just an expensive sample preparation tool. It has taken its place among the suite of other instruments commonly available in analytical and forensic laboratories, universities, geological, medical and biological research institutions, and manufacturing plants. Although the utility of the FIB is not limited to the preparation of specimens for subsequent analysis by other analytical techniques, it has revolutionized the area of TEM specimen preparation. The FIB has also been used to prepare samples for numerous other analytical techniques, and offers a wide range of other capabilities. While the mainstream of FIB usage remains within the semiconductor industry, FIB usage has expanded to applications in metallurgy, ceramics, composites, polymers, geology, art, bio...

  10. Modeling of a focused beam in a semi-infinite highly scattering medium

    DEFF Research Database (Denmark)

    Tycho, Andreas

    1999-01-01

    with confocal microscopy by focusing the probing beam. It istherefore interesting to gauge the performance of the Extended-HuygensFresnel theory for a geometry with a focused gaussian beam against a (fortissue) more well established model such as diffusion theory. A new modelof a focused beam in a semi...

  11. Effect of strong solenoidal focusing on beam emittance of low-energy intense proton beam in the SARAF LEBT

    Science.gov (United States)

    Shor, A.; Weissman, L.

    2016-07-01

    Influence of strong solenoidal beam focusing on beam emittance was studied at the SARAF LEBT beam line using 5 mA 20 keV proton quasi-DC beams. The measurements show that within the experimental uncertainties, emittance does not change over the whole focusing range. Detailed beam dynamics simulations were performed to achieve better understanding of the experimental results. The experimental and simulation results are fully consistent with the assumption of nearly full space charge neutralization for the quasi-DC proton beam.

  12. Focus on Materials Analysis and Processing in Magnetic Fields

    Directory of Open Access Journals (Sweden)

    Yoshio Sakka, Noriyuki Hirota, Shigeru Horii and Tsutomu Ando

    2009-01-01

    Full Text Available Recently, interest in the applications of feeble (diamagnetic and paramagnetic magnetic materials has grown, whereas the popularity of ferromagnetic materials remains steady and high. This trend is due to the progress of superconducting magnet technology, particularly liquid-helium-free superconducting magnets that can generate magnetic fields of 10 T and higher. As the magnetic energy is proportional to the square of the applied magnetic field, the magnetic energy of such 10 T magnets is in excess of 10 000 times that of conventional 0.1 T permanent magnets. Consequently, many interesting phenomena have been observed over the last decade, such as the Moses effect, magnetic levitation and the alignment of feeble magnetic materials. Researchers in this area are widely spread around the world, but their number in Japan is relatively high, which might explain the success of magnetic field science and technology in Japan.Processing in magnetic fields is a rapidly expanding research area with a wide range of promising applications in materials science. The 3rd International Workshop on Materials Analysis and Processing in Magnetic Fields (MAP3, which was held on 14–16 May 2008 at the University of Tokyo, Japan, focused on various topics including magnetic field effects on chemical, physical, biological, electrochemical, thermodynamic and hydrodynamic phenomena; magnetic field effects on the crystal growth and processing of materials; diamagnetic levitation, the magneto-Archimedes effect, spin chemistry, magnetic orientation, control of structure by magnetic fields, magnetic separation and purification, magnetic-field-induced phase transitions, properties of materials in high magnetic fields, the development of NMR and MRI, medical applications of magnetic fields, novel magnetic phenomena, physical property measurement by magnetic fields, and the generation of high magnetic fields.This focus issue compiles 13 key papers selected from the proceedings

  13. Second and third harmonic waves excited by focused Gaussian beams.

    Science.gov (United States)

    Levy, Uri; Silberberg, Yaron

    2015-10-19

    Harmonic generation by tightly-focused Gaussian beams is finding important applications, primarily in nonlinear microscopy. It is often naively assumed that the nonlinear signal is generated predominantly in the focal region. However, the intensity of Gaussian-excited electromagnetic harmonic waves is sensitive to the excitation geometry and to the phase matching condition, and may depend on quite an extended region of the material away from the focal plane. Here we solve analytically the amplitude integral for second harmonic and third harmonic waves and study the generated harmonic intensities vs. focal-plane position within the material. We find that maximum intensity for positive wave-vector mismatch values, for both second harmonic and third harmonic waves, is achieved when the fundamental Gaussian is focused few Rayleigh lengths beyond the front surface. Harmonic-generation theory predicts strong intensity oscillations with thickness if the material is very thin. We reproduced these intensity oscillations in glass slabs pumped at 1550nm. From the oscillations of the 517nm third-harmonic waves with slab thickness we estimate the wave-vector mismatch in a Soda-lime glass as Δk(H)= -0.249μm(-1). PMID:26480441

  14. Simulation on control of beam halo-chaos by power function in the hackle periodic-focusing channel

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The K-V beam through a hackle periodic-focusing magnetic field is studied using the particle-core model. The beam halo-chaos is found, and a power function controller is proposed based on mechanism of halo formation and strategy of controlling halo-chaos. Multiparticle simulation was performed to control the halo by using the power function control method. The results show that the halo-chaos and its regeneration can be eliminated effectively. We also find that the radial particle density evolvement is of uniformity at the beam's centre as long as appropriate paramours are chosen.

  15. FOREWORD: Focus on Materials Analysis and Processing in Magnetic Fields Focus on Materials Analysis and Processing in Magnetic Fields

    Science.gov (United States)

    Sakka, Yoshio; Hirota, Noriyuki; Horii, Shigeru; Ando, Tsutomu

    2009-03-01

    Recently, interest in the applications of feeble (diamagnetic and paramagnetic) magnetic materials has grown, whereas the popularity of ferromagnetic materials remains steady and high. This trend is due to the progress of superconducting magnet technology, particularly liquid-helium-free superconducting magnets that can generate magnetic fields of 10 T and higher. As the magnetic energy is proportional to the square of the applied magnetic field, the magnetic energy of such 10 T magnets is in excess of 10 000 times that of conventional 0.1 T permanent magnets. Consequently, many interesting phenomena have been observed over the last decade, such as the Moses effect, magnetic levitation and the alignment of feeble magnetic materials. Researchers in this area are widely spread around the world, but their number in Japan is relatively high, which might explain the success of magnetic field science and technology in Japan. Processing in magnetic fields is a rapidly expanding research area with a wide range of promising applications in materials science. The 3rd International Workshop on Materials Analysis and Processing in Magnetic Fields (MAP3), which was held on 14-16 May 2008 at the University of Tokyo, Japan, focused on various topics including magnetic field effects on chemical, physical, biological, electrochemical, thermodynamic and hydrodynamic phenomena; magnetic field effects on the crystal growth and processing of materials; diamagnetic levitation, the magneto-Archimedes effect, spin chemistry, magnetic orientation, control of structure by magnetic fields, magnetic separation and purification, magnetic-field-induced phase transitions, properties of materials in high magnetic fields, the development of NMR and MRI, medical applications of magnetic fields, novel magnetic phenomena, physical property measurement by magnetic fields, and the generation of high magnetic fields. This focus issue compiles 13 key papers selected from the proceedings of MAP3. Other

  16. Impact of Dynamic Magnetic fields on the CLIC Main Beam

    CERN Document Server

    Snuverink, J; Jach, C; Jeanneret, JB; Schulte, D; Stulle, F

    2010-01-01

    The Compact Linear Collider (CLIC) accelerator has strong precision requirements on the position of the beam. The beam position will be sensitive to external dynamic magnetic fields (stray fields) in the nanotesla regime. The impact of these fields on the CLIC main beam has been studied by performing simulations on the lattices and tolerances have been determined. Several mitigation techniques will be discussed.

  17. Focused ion beam structuring of low melting polymeric materials

    International Nuclear Information System (INIS)

    This thesis focuses on heating effects during focused ion beam (FIB) processing of low melting polymers. The combined approach using experiments and simulations identifies the in part massive local temperatures as a convolution between intrinsic ion-matter effects and a considerable, technically-induced heating component. While the former is invariable, the latter has been minimized by an alternative process strategy which massively improves the morphological stability and minimizes chemical damage during FIB processing, thus opening new possibilities for application on sensitive, low melting materials. The study starts with systematic experimental investigations which strongly suggested the existence of a technically-induced heating component as a consequence of classically-used serpentine or raster-like patterning strategies. Based on these results, a combined simulation approach of ion trajectories and thermal spike model calculations have been employed to get a deeper insight into spatial and temporal temperature evolution. The results were then combined with the thermodynamic behavior of polymers by means of melting and volatizing temperatures. The comparison of these simulationbased predictions with real FIB experiments revealed very good agreement, proving the applicability of the approach used to describe the temperature evolution from a fundamental point of view. As a next step, these simulations were then applied to the dierent scanning strategies which further con rmed the existence of a technically-induced heating component via classically-used patterning approaches. Due to the deep insight gained via simulations, an alternative patterning strategy was developed, which was expected to minimize these avoidable influences. This new strategy was then evaluated using a multi-technique approach, which revealed strongly reduced chemical damage together with increasing morphological stabilities even for temperature-sensitive polymers. Finally, this alternative

  18. In Situ Characterisation of Permanent Magnetic Quadrupoles for focussing proton beams

    CERN Document Server

    Melone, J J; McCanny, T; Burris-Mog, T; Schramm, U; Grötschel, R; Akhmadaliev, S; Hanf, D; Spohr, K M; Bussmann, M; Cowan, T; Wiggins, S M; Mitchell, M R

    2011-01-01

    High intensity laser driven proton beams are at present receiving much attention. The reasons for this are many but high on the list is the potential to produce compact accelerators. However two of the limitations of this technology is that unlike conventional nuclear RF accelerators lasers produce diverging beams with an exponential energy distribution. A number of different approaches have been attempted to monochromise these beams but it has become obvious that magnetic spectrometer technology developed over many years by nuclear physicists to transport and focus proton beams could play an important role for this purpose. This paper deals with the design and characterisation of a magnetic quadrupole system which will attempt to focus and transport laser-accelerated proton beams.

  19. Properties of dark solitons under SBS in focused beams

    Energy Technology Data Exchange (ETDEWEB)

    Bel' dyugin, Igor' M; Erokhin, A I; Efimkov, V F; Zubarev, I G; Mikhailov, S I [P N Lebedev Physical Institute, Russian Academy of Sciences, Moscow (Russian Federation)

    2012-12-31

    Using the method of four-wave probing of the waist of the laser beam focused into the bulk of a short active medium (L || {tau}c, where L is the length of the active medium, {tau} is the pulse duration, and c is the speed of light), we have studied the dynamics of the behaviour of a dark soliton, appearing upon a jump of the input Stokes signal phase by about {pi} under SBS. The computer simulation has shown that when spontaneous noises with the gain increment {Gamma}, exceeding the self-reflection threshold by 2 - 3 times, are generated, the dark soliton propagates along the interaction region for the time t Almost-Equal-To T{sub 2}{Gamma}{sub th}/2, where T{sub 2} is the the lifetime of acoustic phonons, and {Gamma}{sub th} = 25 - 30 is the stationary threshold gain increment. (special issue devoted to the 90th anniversary of n.g. basov)

  20. Optimization of self-magnetically insulated 'Plasma Focus Diode'

    International Nuclear Information System (INIS)

    The behavior of coaxial type, self-magnetically insulated 'Plasma Focus Diode' (PFD) is analyzed with a one-dimensional calculation model. The calculated results concerning the stability of the electron sheath are used in design of the spherical PFD. Furthermore, the focusability of the spherical PFD is estimated with the calculated results and the experimental results of cylindrical PFD. (author)

  1. H-mode Accelerating Structures with PMQ Focusing for Low-Beta Beams

    Energy Technology Data Exchange (ETDEWEB)

    Kurennoy, Sergey S. [Los Alamos National Laboratory; O' Hara, James F. [Los Alamos National Laboratory; Olivas, Eric R. [Los Alamos National Laboratory; Rybarcyk, Lawrence J. [Los Alamos National Laboratory

    2011-01-01

    We report on results of the project developing high-efficiency normal-conducting RF accelerating structures based on inter-digital H-mode (IH) cavities and the transverse beam focusing with permanent-magnet quadrupoles (PMQ), for beam velocities in the range of a few percent of the speed of light. The shunt impedance of IH-PMQ structures is 10-20 times higher than that of a conventional drift-tube linac, while the transverse size is 4-5 times smaller. The H-PMQ accelerating structures following a short RFQ can be used both in the front end of ion linacs or in stand-alone applications. Results of the combined 3-D modeling -- electromagnetic computations, beam-dynamics simulations with high currents, and thermal-stress analysis -- for a full IH-PMQ accelerator tank are presented. The accelerating field profile in the tank is tuned to provide the best propagation of a 50-mA deuteron beam using coupled iterations of EM and beamdynamics modeling. Multi-particle simulations withParmela and CST Particle Studio have been used to confirm the design. Measurement results of a cold model of the IH-PMQ tank are presented.

  2. Simulation and Field Measurement of Quadrupole Magnets for KOMAC 20MeV Beam line

    Energy Technology Data Exchange (ETDEWEB)

    Chung, B. H.; Kim, H. S.; Song, Y. G.; Kwon, H. J.; Cho, Y. S. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2014-05-15

    In this paper, quadrupole magnets the same as installed at the beam line simulated and analyzed for magnetic fields. Also quadrupole magnets will be measured field stability and evaluated reliability on long time operation. Control system consisted of Labview program and communication method consisted of Ethernet and Rs-232 with optical fiber for devices safety from high voltage and/or high current. As a results the DC power supply is controlled, magnetic fields data is acquired and coil temperature is measured. Magnetic field with hall sensor and temperature with K-type thermo-couple are measured with conversion factor using by voltmeter. Korea Multi-purpose Accelerator Complex (KOMAC) was developed at Gyeongju in Korea in 2012. KOMAC including a 50-keV ion source, a 3-MeV RFQ, and a 100-MeV DTL. And beam line consists of 20-MeV and 100-MeV for user. Proton beam transferred from the linac to the beam line using by dipole magnets and transferred proton beam focused and decreased beam loss and by quadrupole magnets.

  3. Editorial: Focus on Laser- and Beam-Driven Plasma Accelerators

    Science.gov (United States)

    Joshi, Chan; Malka, Victor

    2010-04-01

    The ability of short but intense laser pulses to generate high-energy electrons and ions from gaseous and solid targets has been well known since the early days of the laser fusion program. However, during the past decade there has been an explosion of experimental and theoretical activity in this area of laser-matter interaction, driven by the prospect of realizing table-top plasma accelerators for research, medical and industrial uses, and also relatively small and inexpensive plasma accelerators for high-energy physics at the frontier of particle physics. In this focus issue on laser- and beam-driven plasma accelerators, the latest advances in this field are described. Focus on Laser- and Beam-Driven Plasma Accelerators Contents Slow wave plasma structures for direct electron acceleration B D Layer, J P Palastro, A G York, T M Antonsen and H M Milchberg Cold injection for electron wakefield acceleration X Davoine, A Beck, A Lifschitz, V Malka and E Lefebvre Enhanced proton flux in the MeV range by defocused laser irradiation J S Green, D C Carroll, C Brenner, B Dromey, P S Foster, S Kar, Y T Li, K Markey, P McKenna, D Neely, A P L Robinson, M J V Streeter, M Tolley, C-G Wahlström, M H Xu and M Zepf Dose-dependent biological damage of tumour cells by laser-accelerated proton beams S D Kraft, C Richter, K Zeil, M Baumann, E Beyreuther, S Bock, M Bussmann, T E Cowan, Y Dammene, W Enghardt, U Helbig, L Karsch, T Kluge, L Laschinsky, E Lessmann, J Metzkes, D Naumburger, R Sauerbrey, M. Scḧrer, M Sobiella, J Woithe, U Schramm and J Pawelke The optimum plasma density for plasma wakefield excitation in the blowout regime W Lu, W An, M Zhou, C Joshi, C Huang and W B Mori Plasma wakefield acceleration experiments at FACET M J Hogan, T O Raubenheimer, A Seryi, P Muggli, T Katsouleas, C Huang, W Lu, W An, K A Marsh, W B Mori, C E Clayton and C Joshi Electron trapping and acceleration on a downward density ramp: a two-stage approach R M G M Trines, R Bingham, Z Najmudin

  4. Applications of focused MeV light ion beams for high resolution channeling contrast imaging

    Energy Technology Data Exchange (ETDEWEB)

    Jamieson, D.N.; Breese, M.B.H.; Prawer, S.; Dooley, S.P.; Allen, M.G.; Bettiol, A.A.; Saint, A. [Melbourne Univ., Parkville, VIC (Australia). School of Physics; Ryan, C.G. [Commonwealth Scientific and Industrial Research Organisation (CSIRO), North Ryde, NSW (Australia). Div. of Exploration Geoscience

    1993-12-31

    The technique of Nuclear Microscopy, utilizing a focused ion probe of typically MeV H{sup +} or He{sup +} ions, can produce images where the contrast depends on typical Ion Beam Analysis (lBA) processes. The probe forming lens system usually utilizes strong focusing, precision magnetic quadrupole lenses and the probe is scanned over the target to produce images. Originally, this imaging technique was developed to utilize backscattered particles with incident beam currents typically of a few nA, and the technique became known as Channeling Contrast Microscopy (CCM). Recently, the technique has been developed further to utilize the forward scattering of ions incident along a major crystal axis in thin crystals. This technique is known as Channeling Scanning Transmission Ion Microscopy (CSTIM). Since nearly all incident ions are detected, CSTIM is highly efficient and very low beam currents are sufficient for imaging, typically as low as a few fA. This allows probes as small as 50 nm to be used. In this paper we briefly review the recent applications of these emerging techniques to a variety of single crystal materials (authors). 13 refs., 5 figs.

  5. Time structure of the particle beam source and current sheath filamentation in the plasma focus

    International Nuclear Information System (INIS)

    In previous work the authors have described a method for determining the energy spectrum N(E) of the ion beam emitted from a localized (point) source in the plasma focus pinch. In systematic applications the time structure of the beam source (dN/dt) is assumed to be the same as that of the x-ray localized source recorded from scintillation detector signal with a ≅ 2-5 ns time resolution [the spectrum is derived from the ion time of flight ΔtΓE/sup -1/2/; Δt from the conditions x(t)xMax N/Max x = N(t + Δt) on x-ray signal (x) and particle signal N]. The energy spectrum with a high resolution (ΔE ≤ 0.0 l E) from an alternative method - i.e. from magnetic analyzer data - is essentially the same as that from time of flight. This confirms that the time structure of the ion beam source in the high energy region (E > 0.3 MeV) fits the x-ray (and electron beam) source structure. At any specific time tau (i.e., within a sufficiently small time interval δt during the emission time ≅ 5-50 ns of the beam) the beam is emitted with an amplitude N(E) which is sharply peaked at a specific value of the energy E = E(tau). A correlation of the filamentary structure of the x-ray source with a filamentary structure of the ion source can also be established on a space scale of ≤ 10μm

  6. The prospects of a subnanometer focused neon ion beam.

    Science.gov (United States)

    Rahman, F H M; McVey, Shawn; Farkas, Louis; Notte, John A; Tan, Shida; Livengood, Richard H

    2012-01-01

    The success of the helium ion microscope has encouraged extensions of this technology to produce beams of other ion species. A review of the various candidate ion beams and their technical prospects suggest that a neon beam might be the most readily achieved. Such a neon beam would provide a sputtering yield that exceeds helium by an order of magnitude while still offering a theoretical probe size less than 1-nm. This article outlines the motivation for a neon gas field ion source, the expected performance through simulations, and provides an update of our experimental progress.

  7. Suppression of Space Charge Induced Beam Halo in Nonlinear Focusing Channel

    CERN Document Server

    Batygin, Yuri K; Kurennoy, Sergey; Li, Chao

    2016-01-01

    An intense non-uniform particle beam exhibits strong emittance growth and halo formation in focusing channels due to nonlinear space charge forces of the beam. This phenomenon limits beam brightness and results in particle losses. The problem is connected with irreversible distortion of phase space volume of the beam in conventional focusing structures due to filamentation in phase space. Emittance growth is accompanied by halo formation in real space, which results in inevitable particle losses. A new approach for solving a self-consistent problem for a matched non-uniform beam in two-dimensional geometry is discussed. The resulting solution is applied to the problem of beam transport, while avoiding emittance growth and halo formation by the use of nonlinear focusing field. Conservation of a beam distribution function is demonstrated analytically and by particle-in-cell simulation for a beam with a realistic beam distribution.

  8. Suppression of space charge induced beam halo in nonlinear focusing channel

    Science.gov (United States)

    Batygin, Yuri K.; Scheinker, Alexander; Kurennoy, Sergey; Li, Chao

    2016-04-01

    An intense non-uniform particle beam exhibits strong emittance growth and halo formation in focusing channels due to nonlinear space charge forces of the beam. This phenomenon limits beam brightness and results in particle losses. The problem is connected with irreversible distortion of phase space volume of the beam in conventional focusing structures due to filamentation in phase space. Emittance growth is accompanied by halo formation in real space, which results in inevitable particle losses. A new approach for solving a self-consistent problem for a matched non-uniform beam in two-dimensional geometry is discussed. The resulting solution is applied to the problem of beam transport, while avoiding emittance growth and halo formation by the use of nonlinear focusing field. Conservation of a beam distribution function is demonstrated analytically and by particle-in-cell simulation for a beam with a realistic beam distribution.

  9. Investigation of diluted magnetic semiconductor and nano magnetic material by ion beam technology

    International Nuclear Information System (INIS)

    In this paper, we focus on constitution, magnetism modification and characterization of GaN-based materials using ion beam technology and formation of the nano structure by implanting Mn+ or Co+ ion of different doses into the film samples. SQUID and AGM were used to measure the magnetic properties, such as coercivity and saturation magnetization, for the samples before and after annealing, M-H and M-T curves showed ferromagnetism in the films at both low temperature and room temperature. RBS/C, PIXE and XRD were used to analyze the microstructure, content of doping transition metal and damage. The nano-cluster of ferromagnetism particle was observed under HRTEM. (authors)

  10. Self-Focusing of Hermite-Cosh-Gaussian Laser Beams in Plasma under Density Transition

    OpenAIRE

    Manzoor Ahmad Wani; Niti Kant

    2014-01-01

    Self-focusing of Hermite-Cosh-Gaussian (HChG) laser beam in plasma under density transition has been discussed here. The field distribution in the medium is expressed in terms of beam-width parameters and decentered parameter. The differential equations for the beam-width parameters are established by a parabolic wave equation approach under paraxial approximation. To overcome the defocusing, localized upward plasma density ramp is considered, so that the laser beam is focused on a small spot...

  11. Beam dynamics requirement for proposed booster extraction septum magnet

    International Nuclear Information System (INIS)

    To improve the performance of Indus-2 storage ring, it is planned to operate the booster injector at beam energy of 700 MeV, which is presently being operated at 550 MeV. At higher beam energy the beam size will increase and quality of extracted beam from booster will be deteriorated because of the poor magnetic field homogeneity of existing septum magnet. As a consequence it may reduce the injection efficiency of Indus-2. In this perspective, magnetic field homogeneity and good field region of the extraction septum magnet plays a vital role. Thus it is required to upgrade the technical specification of the booster extraction septum magnet. The same has been evolved and its results are presented. (author)

  12. Beam injection with pulsed multipole magnet at UVSOR-III

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, N., E-mail: naoto@nagoya-u.jp [Synchrotron Radiation Research Center, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aich 464-8603 (Japan); Zen, H. [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Hosaka, M. [Synchrotron Radiation Research Center, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aich 464-8603 (Japan); Konomi, T. [UVSOR, Institute for Molecular Science, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585 (Japan); Adachi, M. [High Energy Accelerator Research Organization, KEK 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Hayashi, K.; Yamazaki, J. [UVSOR, Institute for Molecular Science, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585 (Japan); Takashima, Y. [Synchrotron Radiation Research Center, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aich 464-8603 (Japan); Katoh, M. [UVSOR, Institute for Molecular Science, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585 (Japan)

    2014-12-11

    In this study, we designed and manufactured a pulsed multipole magnet for beam injection into the UVSOR-III ring. A sextupole-like magnetic field could be excited when using the multipole magnet. To compensate for the residual field at the center of the magnet caused by manufacturing imprecisions, thin ferrite sheets were used. The injection experiments at UVSOR-III demonstrated multi-turn injections with the pulsed multipole magnet. The injection efficiency was 23% and the electron beam was stored up to the normal operation current of 300 mA. Moreover, we confirmed that oscillations of stored beams caused by beam injection were drastically suppressed compared with conventional pulsed dipole injection.

  13. Spatial-spectral characterization of focused spatially chirped broadband laser beams.

    Science.gov (United States)

    Greco, Michael J; Block, Erica; Meier, Amanda K; Beaman, Alex; Cooper, Samuel; Iliev, Marin; Squier, Jeff A; Durfee, Charles G

    2015-11-20

    Proper alignment is critical to obtain the desired performance from focused spatially chirped beams, for example in simultaneous spatial and temporal focusing (SSTF). We present a simple technique for inspecting the beam paths and focusing conditions for the spectral components of a broadband beam. We spectrally resolve the light transmitted past a knife edge as it was scanned across the beam at several axial positions. The measurement yields information about spot size, M2, and the propagation paths of different frequency components. We also present calculations to illustrate the effects of defocus aberration on SSTF beams. PMID:26836543

  14. Spatial-spectral characterization of focused spatially chirped broadband laser beams.

    Science.gov (United States)

    Greco, Michael J; Block, Erica; Meier, Amanda K; Beaman, Alex; Cooper, Samuel; Iliev, Marin; Squier, Jeff A; Durfee, Charles G

    2015-11-20

    Proper alignment is critical to obtain the desired performance from focused spatially chirped beams, for example in simultaneous spatial and temporal focusing (SSTF). We present a simple technique for inspecting the beam paths and focusing conditions for the spectral components of a broadband beam. We spectrally resolve the light transmitted past a knife edge as it was scanned across the beam at several axial positions. The measurement yields information about spot size, M2, and the propagation paths of different frequency components. We also present calculations to illustrate the effects of defocus aberration on SSTF beams.

  15. Self-focusing of a Hermite-cosh Gaussian laser beam in a magnetoplasma with ramp density profile

    Energy Technology Data Exchange (ETDEWEB)

    Nanda, Vikas; Kant, Niti; Wani, Manzoor Ahmad [Department of Physics, Lovely Professional University, Phagwara 144411, Punjab (India)

    2013-11-15

    The early and strong self-focusing of a Hermite-cosh-Gaussian laser beam in magnetoplasma in the presence of density ramp has been observed. Focusing and de-focusing nature of the Hermite-cosh-Gaussian laser beam with decentered parameter and magnetic field has been studied, and strong self-focusing is reported. It is investigated that decentered parameter 'b' plays a significant role for the self-focusing of the laser beam and is very sensitive as in case of extraordinary mode. For mode indices, m = 0, 1, 2, and b = 4.00, 3.14, and 2.05, strong self-focusing is observed. Similarly in case of ordinary mode, for m = 0, 1, 2 and b = 4.00, 3.14, 2.049, respectively, strong self-focusing is reported. Further, it is seen that extraordinary mode is more prominent toward self-focusing rather than ordinary mode of propagation. For mode indices m = 0, 1, and 2, diffraction term becomes more dominant over nonlinear term for decentered parameter b=0. For selective higher values of decentered parameter in case of mode indices m=0, 1, and 2, self-focusing effect becomes strong for extraordinary mode. Also increase in the value of magnetic field enhances the self-focusing ability of the laser beam, which is very useful in the applications like the generation of inertial fusion energy driven by lasers, laser driven accelerators, and x-ray lasers.

  16. Literature in focus: Particle beams from theory to practice

    CERN Multimedia

    2003-01-01

    Wednesday 1st October 16 h00 - Central Library CERN's Frank Zimmermann and DESY's Michiko G. Minty had their book 'Measurement and control of charged particle beams' published a few months ago by Springer. Frank Zimmermann, a young but already well established accelerator physicist, was awarded the European Accelerator Prize by the Interdivisional Group on Accelerators of the European Physical Society last year. Mr. Zimmermann was particularly cited for his significant contribution to the understanding of fast ion and electron cloud instabilities. The book is the first comprehensive and systematic review of all methods used for the measurement, correction, and control of the beam dynamics of modern particle accelerators and is intended for graduate students starting research or work in the field of beam physics. Specific techniques and methods for relativistic beams are illustrated by examples from operational accelerators, like CERN, DESY, SLAC, KEK, LBNL, and FNAL. Problems and solutions enhance the book...

  17. Magnetic field extraction of trap-based electron beams using a high-permeability grid

    Energy Technology Data Exchange (ETDEWEB)

    Hurst, N. C.; Danielson, J. R.; Surko, C. M., E-mail: csurko@physics.ucsd.edu [Physics Department, University of California, 9500 Gilman Drive, San Diego, La Jolla, California 92093 (United States)

    2015-07-15

    A method to form high quality electrostatically guided lepton beams is explored. Test electron beams are extracted from tailored plasmas confined in a Penning-Malmberg trap. The particles are then extracted from the confining axial magnetic field by passing them through a high magnetic permeability grid with radial tines (a so-called “magnetic spider”). An Einzel lens is used to focus and analyze the beam properties. Numerical simulations are used to model non-adiabatic effects due to the spider, and the predictions are compared with the experimental results. Improvements in beam quality are discussed relative to the use of a hole in a high permeability shield (i.e., in lieu of the spider), and areas for further improvement are described.

  18. Measurements of fast electron beams and soft X-ray emission from plasma-focus experiments

    Directory of Open Access Journals (Sweden)

    Surała Władysław

    2016-06-01

    Full Text Available The paper reports results of the recent experimental studies of pulsed electron beams and soft X-rays in plasma-focus (PF experiments carried out within a modified PF-360U facility at the NCBJ, Poland. Particular attention was focused on time-resolved measurements of the fast electron beams by means of two different magnetic analyzers, which could record electrons of energy ranging from about 41 keV to about 715 keV in several (6 or 8 measuring channels. For discharges performed with the pure deuterium filling, many strong electron signals were recorded in all the measuring channels. Those signals were well correlated with the first hard X-ray pulse detected by an external scintillation neutron-counter. In some of the analyzer channels, electron spikes (lasting about dozens of nanoseconds and appearing in different instants after the current peculiarity (so-called current dip were also recorded. For several discharges, fast ion beams, which were emitted along the z-axis and recorded with nuclear track detectors, were also investigated. Those measurements confirmed a multibeam character of the ion emission. The time-integrated soft X-ray images, which were taken side-on by means of a pinhole camera and sensitive X-ray films, showed the appearance of some filamentary structures and so-called hot spots. The application of small amounts of admixtures of different heavy noble gases, i.e. of argon (4.8% volumetric, krypton (1.6% volumetric, or xenon (0.8% volumetric, decreased intensity of the recorded electron beams, but increased intensity of the soft X-ray emission and showed more distinct and numerous hot spots. The recorded electron spikes have been explained as signals produced by quasi-mono-energetic microbeams emitted from tiny sources (probably plasma diodes, which can be formed near the observed hot spots.

  19. Testing beam-induced quench levels of LHC superconducting magnets

    Science.gov (United States)

    Auchmann, B.; Baer, T.; Bednarek, M.; Bellodi, G.; Bracco, C.; Bruce, R.; Cerutti, F.; Chetvertkova, V.; Dehning, B.; Granieri, P. P.; Hofle, W.; Holzer, E. B.; Lechner, A.; Nebot Del Busto, E.; Priebe, A.; Redaelli, S.; Salvachua, B.; Sapinski, M.; Schmidt, R.; Shetty, N.; Skordis, E.; Solfaroli, M.; Steckert, J.; Valuch, D.; Verweij, A.; Wenninger, J.; Wollmann, D.; Zerlauth, M.

    2015-06-01

    In the years 2009-2013 the Large Hadron Collider (LHC) has been operated with the top beam energies of 3.5 and 4 TeV per proton (from 2012) instead of the nominal 7 TeV. The currents in the superconducting magnets were reduced accordingly. To date only seventeen beam-induced quenches have occurred; eight of them during specially designed quench tests, the others during injection. There has not been a single beam-induced quench during normal collider operation with stored beam. The conditions, however, are expected to become much more challenging after the long LHC shutdown. The magnets will be operating at near nominal currents, and in the presence of high energy and high intensity beams with a stored energy of up to 362 MJ per beam. In this paper we summarize our efforts to understand the quench levels of LHC superconducting magnets. We describe beam-loss events and dedicated experiments with beam, as well as the simulation methods used to reproduce the observable signals. The simulated energy deposition in the coils is compared to the quench levels predicted by electrothermal models, thus allowing one to validate and improve the models which are used to set beam-dump thresholds on beam-loss monitors for run 2.

  20. Guiding and focusing of fast electron beams produced by ultra-intense laser pulse using a double cone funnel target

    International Nuclear Information System (INIS)

    A novel double cone funnel target design aiming at efficiently guiding and focusing fast electron beams produced in high intensity (>1019 W/cm2) laser-solid interactions is investigated via two-dimensional particle-in-cell simulations. The forward-going fast electron beams are shown to be directed and focused to a smaller size in comparison with the incident laser spot size. This plasma funnel attached on the cone target guides and focuses electrons in a manner akin to the control of liquid by a plastic funnel. Such device has the potential to add substantial design flexibility and prevent inefficiencies for important applications such as fast ignition. Two reasons account for the collimation of fast electron beams. First, the sheath electric fields and quasistatic magnetic fields inside the vacuum gap of the double cone provide confinement of the fast electrons in the laser-plasma interaction region. Second, the interface magnetic fields inside the beam collimator further guide and focus the fast electrons during the transport. The application of this technique to cone-guided fast ignition is considered, and it is shown that it can enhance the laser energy deposition in the compressed fuel plasma by a factor of 2 in comparison with the single cone target case

  1. Two-dimensional simulations of nonlinear beam-plasma interaction in isotropic and magnetized plasmas

    CERN Document Server

    Timofeev, I V

    2012-01-01

    Nonlinear interaction of a low density electron beam with a uniform plasma is studied using two-dimensional particle-in-cell (PIC) simulations. We focus on formation of coherent phase space structures in the case, when a wide two-dimensional wave spectrum is driven unstable, and we also study how nonlinear evolution of these structures is affected by the external magnetic field. In the case of isotropic plasma, nonlinear buildup of filamentation modes due to the combined effects of two-stream and oblique instabilities is found to exist and growth mechanisms of secondary instabilities destroying the BGK--type nonlinear wave are identified. In the weak magnetic field, the energy of beam-excited plasma waves at the nonlinear stage of beam-plasma interaction goes predominantly to the short-wavelength upper-hybrid waves propagating parallel to the magnetic field, whereas in the strong magnetic field the spectral energy is transferred to the electrostatic whistlers with oblique propagation.

  2. Propagation and cross-focusing of hollow Gaussian laser beams in plasma

    International Nuclear Information System (INIS)

    This paper presents the cross focusing of two high power Hollow Gaussian laser beams (HGLB) by considering ponderomotive nonlinearity in a collisionless plasma. On account of the nonlinearity present in the plasma the two laser beams affect the dynamics of each other and cross-focusing takes place. The expressions for the laser beam intensities by using the eikonal method have been derived and the beam width parameter is calculated in the case when only ponderomotive nonlinearity is operative. The numerical appreciation of the cross focusing has been presented graphically by plotting beam-width parameter vs. dimensionless distance of propagation. Theself focusing of one laser beam is affected due to the optical inhomogeneities introduced by another copropagating HGLB in the plasma. It is observed thatthe presence of one HGLB also affects the self focusing of different order's (n) of the other HGLB.

  3. Electron gun for a multiple beam klystron with magnetic compression of the electron beams

    Science.gov (United States)

    Ives, R. Lawrence; Tran, Hien T; Bui, Thuc; Attarian, Adam; Tallis, William; David, John; Forstall, Virginia; Andujar, Cynthia; Blach, Noah T; Brown, David B; Gadson, Sean E; Kiley, Erin M; Read, Michael

    2013-10-01

    A multi-beam electron gun provides a plurality N of cathode assemblies comprising a cathode, anode, and focus electrode, each cathode assembly having a local cathode axis and also a central cathode point defined by the intersection of the local cathode axis with the emitting surface of the cathode. Each cathode is arranged with its central point positioned in a plane orthogonal to a device central axis, with each cathode central point an equal distance from the device axis and with an included angle of 360/N between each cathode central point. The local axis of each cathode has a cathode divergence angle with respect to the central axis which is set such that the diverging magnetic field from a solenoidal coil is less than 5 degrees with respect to the projection of the local cathode axis onto a cathode reference plane formed by the device axis and the central cathode point, and the local axis of each cathode is also set such that the angle formed between the cathode reference plane and the local cathode axis results in minimum spiraling in the path of the electron beams in a homogenous magnetic field region of the solenoidal field generator.

  4. Laser cooling of a magnetically guided ultra cold atom beam

    Energy Technology Data Exchange (ETDEWEB)

    Aghajani-Talesh, Anoush

    2014-07-01

    This thesis examines two complimentary methods for the laser cooling of a magnetically guided ultra-cold atom beam. If combined, these methods could serve as a starting point for high-through put and possibly even continuous production of Bose-Einstein condensates. First, a mechanism is outlined to harvest ultra cold atoms from a magnetically guided atom beam into an optical dipole trap. A continuous loading scheme is described that dissipates the directed kinetic energy of a captured atom via deceleration by a magnetic potential barrier followed by optical pumping to the energetically lowest Zeeman sublevel. The application of this scheme to the transfer of ultra cold chromium atoms from a magnetically guided atom beam into a deep optical dipole trap is investigated via numerical simulations of the loading process. Based on the results of the theoretical studies the feasibility and the efficiency of our loading scheme, including the realisation of a suitable magnetic field configuration, are analysed. Second, experiments were conducted on the transverse laser cooling of a magnetically guided beam of ultra cold chromium atoms. Radial compression by a tapering of the guide is employed to adiabatically heat the beam. Inside the tapered section heat is extracted from the atom beam by a two-dimensional optical molasses perpendicular to it, resulting in a significant increase of atomic phase space density. A magnetic offset field is applied to prevent optical pumping to untrapped states. Our results demonstrate that by a suitable choice of the magnetic offset field, the cooling beam intensity and detuning, atom losses and longitudinal heating can be avoided. Final temperatures below 65 μK have been achieved, corresponding to an increase of phase space density in the guided beam by more than a factor of 30.

  5. Laser cooling of a magnetically guided ultra cold atom beam

    International Nuclear Information System (INIS)

    This thesis examines two complimentary methods for the laser cooling of a magnetically guided ultra-cold atom beam. If combined, these methods could serve as a starting point for high-through put and possibly even continuous production of Bose-Einstein condensates. First, a mechanism is outlined to harvest ultra cold atoms from a magnetically guided atom beam into an optical dipole trap. A continuous loading scheme is described that dissipates the directed kinetic energy of a captured atom via deceleration by a magnetic potential barrier followed by optical pumping to the energetically lowest Zeeman sublevel. The application of this scheme to the transfer of ultra cold chromium atoms from a magnetically guided atom beam into a deep optical dipole trap is investigated via numerical simulations of the loading process. Based on the results of the theoretical studies the feasibility and the efficiency of our loading scheme, including the realisation of a suitable magnetic field configuration, are analysed. Second, experiments were conducted on the transverse laser cooling of a magnetically guided beam of ultra cold chromium atoms. Radial compression by a tapering of the guide is employed to adiabatically heat the beam. Inside the tapered section heat is extracted from the atom beam by a two-dimensional optical molasses perpendicular to it, resulting in a significant increase of atomic phase space density. A magnetic offset field is applied to prevent optical pumping to untrapped states. Our results demonstrate that by a suitable choice of the magnetic offset field, the cooling beam intensity and detuning, atom losses and longitudinal heating can be avoided. Final temperatures below 65 μK have been achieved, corresponding to an increase of phase space density in the guided beam by more than a factor of 30.

  6. Tailoring reflection of graphene plasmons by focused ion beams

    CERN Document Server

    Luo, Weiwei; Wu, Wei; Xiang, Yinxiao; Ren, Mengxin; Zhang, Xinzheng; Xu, Jingjun

    2016-01-01

    Graphene plasmons are of remarkable features that make graphene plasmon elements promising for applications to integrated photonic devices. The fabrication of graphene plasmon components and control over plasmon propagating are of fundamental important. Through near-field plasmon imaging, we demonstrate controllable modifying of the reflection of graphene plasmon at boundaries etched by ion beams. Moreover, by varying ion dose at a proper value, nature like reflection boundary can be obtained. We also investigate the influence of ion beam incident angle on plasmon reflection. To illustrate the application of ion beam etching, a simple graphene wedge-shape plasmon structure is fabricated and performs excellently, proving this technology as a simple and efficient tool for controlling graphene plasmons.

  7. Disruption of geometric focus by self-magnetic fields

    International Nuclear Information System (INIS)

    The perturbation of ballistic ion orbits due to the azimuthal magnetic field associated with incomplete current neutralization is investigated. It is shown that 1% current non-neutralization is sufficient to disrupt the millimeter-radius focus desired for present reactor scenarios. Implications of these results and directions for future research are discussed

  8. A large stroke magnetic fluid deformable mirror for focus control

    Science.gov (United States)

    Min, Ling-kun; Wu, Zhi-zheng; Huang, Ming-shuang; Kong, Xiang-hui

    2016-03-01

    A liquid deformable mirror, which can provide a large stroke deflection more than 100 μm, is proposed for focus control. The deformable mirror utilizes the concept of magnetic fluid deformation shaped with electromagnetic fields to achieve concave or convex surface and to change the optical focus depth of the mirrors. The free surface of the magnetic fluid is coated with a thin layer of metal-liquid-like film (MELLF) prepared from densely packed silver nanoparticles to enhance the reflectance of the deformable mirror. The experimental results on the fabricated prototype magnetic fluid deformable mirror (MFDM) show that the desired concave/convex surface shape can be controlled precisely with a closed-loop adaptive optical system.

  9. Experimental single-impulse magnetic focusing of launched cold atoms

    CERN Document Server

    Smith, D A; Hughes, I G; Pritchard, M J; Arnold, Aidan S.; Hughes, Ifan G.; Pritchard, Matthew J.; Smith, David A.

    2007-01-01

    Three-dimensional magnetic focusing of cold atoms with a single magnetic impulse has been observed for the first time. We load 7x10^7 85-Rb atoms into a magneto-optical trap, precool the atoms with optical molasses, then use moving molasses to launch them vertically through 20.5cm to the apex of flight. In transit the atoms are optically pumped, prior to the single magnetic lens impulse that occurs 16.5cm above the MOT. Fluorescence images at the apex of flight characterise the widths of the focussed cloud. Results were obtained for four different configurations of the baseball lens, which tuned the relationship between the axial and radial frequencies of the lens. Compact focused clouds were seen for all four configurations.

  10. Estimation of the Beam Width in Magnetic Mass Spectrometer

    Directory of Open Access Journals (Sweden)

    O.N. Peregudov

    2010-01-01

    Full Text Available A method for estimation of the beam width in magnetic sector mass spectrometers is proposed. This method consists in the restoration of the initial ion density distribution function in a beam cross-section before the receiving collector slit and can be used for the qualitative estimation of the mass spectrometer ion-optical scheme.

  11. Direct patterning of vortex generators on a fiber tip using a focused ion beam.

    Science.gov (United States)

    Vayalamkuzhi, Pramitha; Bhattacharya, Shanti; Eigenthaler, Ulrike; Keskinbora, Kahraman; Samlan, C T; Hirscher, Michael; Spatz, Joachim P; Viswanathan, Nirmal K

    2016-05-15

    The realization of spiral phase optical elements on the cleaved end of an optical fiber by focused ion beam milling is presented. A focused Ga+ ion beam with an acceleration voltage of 30 keV is used to etch continuous spiral phase plates and fork gratings directly on the tip of the fiber. The phase characteristics of the output beam generated by the fabricated structures measured via an interference experiment confirmed the presence of phase singularity in the output beam. The devices are expected to be promising candidates for all-fiber beam shaping and optical trapping applications.

  12. Direct patterning of vortex generators on a fiber tip using a focused ion beam.

    Science.gov (United States)

    Vayalamkuzhi, Pramitha; Bhattacharya, Shanti; Eigenthaler, Ulrike; Keskinbora, Kahraman; Samlan, C T; Hirscher, Michael; Spatz, Joachim P; Viswanathan, Nirmal K

    2016-05-15

    The realization of spiral phase optical elements on the cleaved end of an optical fiber by focused ion beam milling is presented. A focused Ga+ ion beam with an acceleration voltage of 30 keV is used to etch continuous spiral phase plates and fork gratings directly on the tip of the fiber. The phase characteristics of the output beam generated by the fabricated structures measured via an interference experiment confirmed the presence of phase singularity in the output beam. The devices are expected to be promising candidates for all-fiber beam shaping and optical trapping applications. PMID:27176945

  13. Low-temperature transport in ultra-thin tungsten films grown by focused-ion-beam deposition

    OpenAIRE

    Chiatti, O.; Warburton, P. A.

    2010-01-01

    We have fabricated tungsten-containing films by focused-ion-beam (FIB)-induced chemical vapour deposition. By using ion-beam doses below 50 pC/μm² on a substrate of amorphous silicon, we have grown continuous films with thickness below 20 nm. The low-temperature electron transport properties were investigated by measuring current-voltage characteristics for temperatures down to 400 mK and in magnetic fields up to 8 T. FIB-deposited tungsten films are known to have an enhanced transition tem­p...

  14. Focusing of Gaussian beam passed under small angle to optical axis of uniaxial crystal

    Science.gov (United States)

    Ivanov, M. O.; Shostka, N. V.

    2016-07-01

    We showed both experimentally and analytically, the effect of focusing of a Gaussian beam propagated under small angle ϕ with respect to the optical axis of a uniaxial crystal, on the generation of a bottle beam. At ϕ = 0° two foci that correspond to ordinary and extraordinary parts of a beam form a closed 3D structure of a bottle beam. At this point, the beam, in the foci points, has radially and azimuthally aligned polarizations. Increasing the value of ϕ leads to dramatic changes in the intensity and polarization structure of a bottle beam. Starting from the value of ϕ = ±2° the closed 3D symmetric structure of a bottle beam breaks down. At ϕ = ±5° both beams are focused at the same transverse plane, while its polarization evolves to x- and y-linear. With a further increase in angle ϕ two foci ‘switch’ their spatial positions and move further away.

  15. Sub-10 nm focused electron beam induced deposition

    NARCIS (Netherlands)

    Van Dorp, W.F.

    2008-01-01

    Work started with a critical review of literature from the past 70-odd years. The review shows that the physical processes occurring in EBID are generally well understood. By combining models for electron scattering in a solid and electron beam induced heating and knowledge of growth regimes, the ma

  16. Beam Coupling Impedance of the New Beam Screen of the LHC Injection Kicker Magnets

    CERN Document Server

    Day, H; Caspers, F; Métral, E; Salvant, B; Uythoven, J

    2014-01-01

    The LHC injection kicker magnets experienced significant beam induced heating of the ferrite yoke, with high beam currents circulating for many hours, during operation of the LHC in 2011 and 2012. The causes of this beam induced heating were studied in depth and an improved beam screen implemented to reduce the impedance. Results of measurements and simulations of the new beam screen design are presented in this paper: these are used to predict power loss for operation after long shutdown 1 and for proposed HL-LHC operational parameters.

  17. Special diffractive elements for optical trapping fabricated on optical fiber tips using the focused ion beam

    Science.gov (United States)

    Rodrigues Ribeiro, R. S.; Guerreiro, A.; Viegas, J.; Jorge, P. A. S.

    2016-05-01

    In this work, spiral phase lenses and Fresnel zone lenses for beam tailoring, fabricated on the tip of optical fibers, are reported. The spiral phase lenses allow tailoring the fundamental guided mode, a Gaussian beam, into a Laguerre - Gaussian profile without using additional optical elements. Whereas, the Fresnel lenses are used as focusing systems. The lenses are fabricated using Focused Ion Beam milling, enabling high resolution in the manufacturing process. The output optical intensity profiles matching the numerical simulations are presented and analyzed.

  18. Absorption of focused laser beams by a nonspherical plasma

    International Nuclear Information System (INIS)

    The interaction of a high intensity axially symmetric beam with a nonspherical plasma is studied numerically. The high frequency plasma response is calculated using a linearized fluid approximation. The full three dimensional Maxwell's equations are solved in spherical coordinates. A method for selectively damping the longitudinal electric fields is included to model thermal, kinetic, or nonlinear effects near the critical density. The low frequency response of the plasma to the ponderomotive force is followed with an isothermal hydrodynamic description. The incident laser beam is circularly polarized so that the plasma remains azimuthally symmetric to first order. Detailed descriptions of several representative calculations are given. It is found that the absorption of an initially spherical plasma can be significantly increased by induced aspherical plasma density profile modifications. A simple physical explanation for the observed absorption increase is proposed. Finally, the validity of the approximations made is analyzed briefly

  19. Testing beam-induced quench levels of LHC superconducting magnets

    CERN Document Server

    Auchmann, B; Bednarek, M; Bellodi, G; Bracco, C; Bruce, R; Cerutti, F; Chetvertkova, V; Dehning, B; Granieri, P P; Hofle, W; Holzer, E B; Lechner, A; Del Busto, E Nebot; Priebe, A; Redaelli, S; Salvachua, B; Sapinski, M; Schmidt, R; Shetty, N; Skordis, E; Solfaroli, M; Steckert, J; Valuch, D; Verweij, A; Wenninger, J; Wollmann, D; Zerlauth, M

    2015-01-01

    In the years 2009-2013 the Large Hadron Collider (LHC) has been operated with the top beam energies of 3.5 TeV and 4 TeV per proton (from 2012) instead of the nominal 7 TeV. The currents in the superconducting magnets were reduced accordingly. To date only seventeen beam-induced quenches have occurred; eight of them during specially designed quench tests, the others during injection. There has not been a single beam- induced quench during normal collider operation with stored beam. The conditions, however, are expected to become much more challenging after the long LHC shutdown. The magnets will be operating at near nominal currents, and in the presence of high energy and high intensity beams with a stored energy of up to 362 MJ per beam. In this paper we summarize our efforts to understand the quench levels of LHC superconducting magnets. We describe beam-loss events and dedicated experiments with beam, as well as the simulation methods used to reproduce the observable signals. The simulated energy depositio...

  20. LIF Diagnostic for Measuring Beam-Transport Magnetic Fields

    Science.gov (United States)

    Jones, T. G.; Hinshelwood, D. D.; Neri, J. M.; Ottinger, P. F.; Noonan, W. A.

    1997-11-01

    A novel, spatially-resolved diagnostic is being developed to measure magnetic fields associated with intense ion beam propagation through a low-pressure gas, as is envisioned for light ion-driven ICF. The diagnostic technique uses laser-induced fluorescence (LIF) spectroscopy, and can be varied to measure either small or large fields. Small fields, as expected in ballistic transport with solenoidal lens focusing using ~ 1 Torr gas, produce Zeeman shifts, Δ λ_Z, smaller than the transition linewidth, Δ λ. High sensitivity to measure these shifts is achieved by a variation on the Babcock technique.^1 Large fields, as expected in self-pinched transport using 1--100 mTorr gas, produce Δ λZ larger than Δ λ. These Δ λZ will be resolved using an etalon as a narrowband, high-throughput optical filter. Available results from benchtop experiments using calibrated B-fields for both the small- and large-field techniques, and progress in fielding this diagnostic on the Gamble-II accelerator for beam-transport studies will be presented. Work supported by DOE through Sandia National Laboratories. ^ National Research Council Research Associate. ^ Present address University of Maryland, College Park, MD. ^1 W.A. Noonan, et al., Rev. Sci. Instrum. 68, 1032 (1997).

  1. Multi-slit triode ion optical system with ballistic beam focusing

    Science.gov (United States)

    Davydenko, V.; Amirov, V.; Gorbovsky, A.; Deichuli, P.; Ivanov, A.; Kolmogorov, A.; Kapitonov, V.; Mishagin, V.; Shikhovtsev, I.; Sorokin, A.; Stupishin, N.; Karpushov, A. N.; Smirnov, A.; Uhlemann, R.

    2016-02-01

    Multi-slit triode ion-optical systems with spherical electrodes are of interest for formation of intense focused neutral beams for plasma heating. At present, two versions of focusing multi-slit triode ion optical system are developed. The first ion optical system forms the proton beam with 15 keV energy, 140 A current, and 30 ms duration. The second ion optical system is intended for heating neutral beam injector of Tokamak Configuration Variable (TCV). The injector produces focused deuterium neutral beam with 35 keV energy, 1 MW power, and 2 s duration. In the later case, the angular beam divergence of the neutral beam is 20-22 mrad in the direction across the slits of the ion optical system and 12 mrad in the direction along the slits.

  2. Multi-slit triode ion optical system with ballistic beam focusing

    International Nuclear Information System (INIS)

    Multi-slit triode ion-optical systems with spherical electrodes are of interest for formation of intense focused neutral beams for plasma heating. At present, two versions of focusing multi-slit triode ion optical system are developed. The first ion optical system forms the proton beam with 15 keV energy, 140 A current, and 30 ms duration. The second ion optical system is intended for heating neutral beam injector of Tokamak Configuration Variable (TCV). The injector produces focused deuterium neutral beam with 35 keV energy, 1 MW power, and 2 s duration. In the later case, the angular beam divergence of the neutral beam is 20-22 mrad in the direction across the slits of the ion optical system and 12 mrad in the direction along the slits

  3. Multi-slit triode ion optical system with ballistic beam focusing

    Energy Technology Data Exchange (ETDEWEB)

    Davydenko, V., E-mail: V.I.Davydenko@inp.nsk.su; Amirov, V.; Gorbovsky, A.; Deichuli, P.; Ivanov, A.; Kolmogorov, A.; Kapitonov, V.; Mishagin, V.; Shikhovtsev, I.; Sorokin, A.; Stupishin, N. [Budker Institute of Nuclear Physics, Novosibirsk 630090 (Russian Federation); Karpushov, A. N. [Ecole Polytechnique Fédérale de Lausanne, Centre de Recherches en Physique des Plasmas (CRPP), CH-1015 Lausanne (Switzerland); Smirnov, A. [Tri Alpha Energy, Inc., Rancho Santa Margarita, California 92688 (United States); Uhlemann, R. [Institute of Energy and Climate Research-Plasma Physics, Research Center Juelich, 52425 Juelich (Germany)

    2016-02-15

    Multi-slit triode ion-optical systems with spherical electrodes are of interest for formation of intense focused neutral beams for plasma heating. At present, two versions of focusing multi-slit triode ion optical system are developed. The first ion optical system forms the proton beam with 15 keV energy, 140 A current, and 30 ms duration. The second ion optical system is intended for heating neutral beam injector of Tokamak Configuration Variable (TCV). The injector produces focused deuterium neutral beam with 35 keV energy, 1 MW power, and 2 s duration. In the later case, the angular beam divergence of the neutral beam is 20-22 mrad in the direction across the slits of the ion optical system and 12 mrad in the direction along the slits.

  4. Superconducting wiggler magnets for beam-emittance damping rings

    CERN Document Server

    Schoerling, Daniel

    2012-01-01

    Ultra-low emittance beams with a high bunch charge are necessary for the luminosity performance of linear electron-positron colliders, such as the Compact Linear Collider (CLIC). An effective way to create ultra-low emittance beams with a high bunch charge is to use damping rings, or storage rings equipped with strong damping wiggler magnets. The remanent field of the permanent magnet materials and the ohmic losses in normal conductors limit the economically achievable pole field in accelerator magnets operated at around room temperature to below the magnetic saturation induction, which is 2.15 T for iron. In wiggler magnets, the pole field in the center of the gap is reduced further like the hyperbolic cosine of the ratio of the gap size and the period length multiplied by pi. Moreover, damping wiggler magnets require relatively large gaps because they have to accept the un-damped beam and to generate, at a small period length, a large magnetic flux density amplitude to effectively damp the beam emittance....

  5. Matching bunched beams to alternating gradient focusing systems

    International Nuclear Information System (INIS)

    A numerical procedure for generating phase-space distributions matched to alternating gradient focusing systems has been tested. For a smooth-focusing system a matched distribution can be calculated. With a particle tracing simulation code such a distribution can be followed while adiabatically deforming the focusing forces until an alternating gradient configuration is reached. The distribution remains matched; the final distribution is periodic with the structure period. External nonlinearities, including nonlinear couplings, were included in our examples but space charge was not. This procedure is expected to work with space charge but will require a 3-D space-charge calculation in the simulation code

  6. A critical literature review of focused electron beam induced deposition

    Science.gov (United States)

    van Dorp, W. F.; Hagen, C. W.

    2008-10-01

    An extensive review is given of the results from literature on electron beam induced deposition. Electron beam induced deposition is a complex process, where many and often mutually dependent factors are involved. The process has been studied by many over many years in many different experimental setups, so it is not surprising that there is a great variety of experimental results. To come to a better understanding of the process, it is important to see to which extent the experimental results are consistent with each other and with the existing model. All results from literature were categorized by sorting the data according to the specific parameter that was varied (current density, acceleration voltage, scan patterns, etc.). Each of these parameters can have an effect on the final deposit properties, such as the physical dimensions, the composition, the morphology, or the conductivity. For each parameter-property combination, the available data are discussed and (as far as possible) interpreted. By combining models for electron scattering in a solid, two different growth regimes, and electron beam induced heating, the majority of the experimental results were explained qualitatively. This indicates that the physical processes are well understood, although quantitatively speaking the models can still be improved. The review makes clear that several major issues remain. One issue encountered when interpreting results from literature is the lack of data. Often, important parameters (such as the local precursor pressure) are not reported, which can complicate interpretation of the results. Another issue is the fact that the cross section for electron induced dissociation is unknown. In a number of cases, a correlation between the vertical growth rate and the secondary electron yield was found, which suggests that the secondary electrons dominate the dissociation rather than the primary electrons. Conclusive evidence for this hypothesis has not been found. Finally

  7. Investigation of the chaotic dynamics of an electron beam with a virtual cathode in an external magnetic field

    Science.gov (United States)

    Egorov, E. N.; Hramov, A. E.

    2006-08-01

    The effect of the strength of the focusing magnetic field on chaotic dynamic processes occurring in an electron beam with a virtual cathode, as well as on the processes whereby the structures form in the beam and interact with each other, is studied by means of two-dimensional numerical simulations based on solving a self-consistent set of Vlasov-Maxwell equations. It is shown that, as the focusing magnetic field is decreased, the dynamics of an electron beam with a virtual cathode becomes more complicated due to the formation and interaction of spatiotemporal longitudinal and transverse structures in the interaction region of a vircator. The optimum efficiency of the interaction of an electron beam with the electromagnetic field of the vircator is achieved at a comparatively weak external magnetic field and is determined by the fundamentally two-dimensional nature of the motion of the beam electrons near the virtual cathode.

  8. Focusing properties of Gaussian Schell-model beams by an astigmatic aperture lens

    Institute of Scientific and Technical Information of China (English)

    Pan Liu-Zhan; Ding Chao-Liang

    2007-01-01

    This paper studies the focusing properties of Gaussian Schell-model (GSM) beams by an astigmatic aperture lens.It is shown that the axial irradiance distribution, the maximum axial irradiance and its position of focused GSM beams by an astigmatic aperture lens depend upon the astigmatism of the lens, the coherence of partially coherent light, the truncation parameter of the aperture and Fresnel number. The numerical calculation results are given to illustrate how these parameters affect the focusing property.

  9. Physico-chemical study of the focused electron beam induced deposition process

    OpenAIRE

    Bret, Tristan; Hoffmann, Patrik

    2007-01-01

    The focused electron beam induced deposition process is a promising technique for nano and micro patterning. Electrons can be focused in sub-angström dimensions, which allows atomic-scale resolution imaging, analysis, and processing techniques. Before the process can be used in controlled applications, the precise nature of the deposition mechanism must be described and modelled. The aim of this research work is to present a physical and chemical description of the focused electron beam induc...

  10. Self-focusing of Hermite-Gaussian laser beam with relativistic nonlinearity

    International Nuclear Information System (INIS)

    This paper presents an investigation of self-focusing of Hermite-Gaussian laser beams in plasma considering relativistic nonlinearity. The differential equations for beam width parameters are obtained using the usual Wentzel–Kramers–Brillouin and paraxial approximations. The nonlinearity in the dielectric constant is assumed to be aroused mainly due to the relativistic mass correction of electron. To highlight the nature of focusing, graphical results of the behavior of beam-width parameters with the dimensionless distance of propagation is presented. The numerical computation is completed by using Taylor series method. The present work is helpful to understand issues related to the beam propagation in laser plasma interaction experiments

  11. "On-chip magnetic bead microarray using hydrodynamic focusing in a passive magnetic separator"

    DEFF Research Database (Denmark)

    Smistrup, Kristian; Kjeldsen, B.; Reimers, R.L.;

    2005-01-01

    Implementing DNA and protein microarrays into lab-on-a-chip systems can be problematic since these are sensitive to heat and strong chemicals. Here, we describe the functionalization of a microchannel with two types of magnetic beads using hydrodynamic focusing combined with a passive magnetic...

  12. Effect of a spectrometer magnet on the beam-beam interaction

    Energy Technology Data Exchange (ETDEWEB)

    Cornacchia, M; Parzen, G

    1981-01-01

    The presence of experimental apparatus in the interaction regions of an intersecting beam accelerator changes the configuration of the crossing beams. This changes the space-charge forces with respect to the standard, magnet-free crossing. The question is: what is the maximum allowable perturbation caused by the spectrometer magnet that can be tolerated from the point of view of the beam dynamics. This paper is limited to the perturbations that the curved trajectories cause the beam-beam space charge nonlinearities. The question has arisen of how one defines the strength of the perturbation. The only solution is to compute the strength of the most important nonlinear resources. In what follows, the computational method used in calculating these resonances is described, and compared with those induced by random orbit errors.

  13. Matching bunched beams to alternating gradient focusing systems

    International Nuclear Information System (INIS)

    A numerical procedure for generating phase-space distributions matched to alternating gradient focusing systems has been tested. For a smooth-focusing system a matched distribution can be calculated. With a particle tracing simulation code such a distribution can be followed while adiabatically deforming the focusing forces until an alternating gradient configuration is reached. The distribution remains matched; that is, the final distribution is periodic with the structure period. This method is useful because it can produce distributions matched to nonlinear forces. This is a feature that elliptical distributions, with ellipse parameters obtained from the Courant-Snyder theory, do not have. External nonlinearities, including nonlinear couplings, were included in our examples but space charge was not. This procedure is expected to work with space charge but will require a three-dimensional space charge calculation in the simulation code

  14. Effects of beam velocity and density on an ion-beam pulse moving in magnetized plasmas

    CERN Document Server

    Zhao, Xiao-ying; Zhao, Yong-tao; Qi, Xin; Yang, Lei

    2016-01-01

    The wakefield and stopping power of an ion-beam pulse moving in magnetized plasmas are investigated by particle-in-cell (PIC) simulations. The effects of beam velocity and density on the wake and stopping power are discussed. In the presence of magnetic field, it is found that beside the longitudinal conversed V-shaped wakes, the strong whistler wave are observed when low-density and low-velocity pulses moving in plasmas. The corresponding stopping powers are enhanced due to the drag of these whistler waves. As beam velocities increase, the whistler waves disappear, and only are conversed V-shape wakes observed. The corresponding stopping powers are reduced compared with these in isotropic plasmas. When high-density pulses transport in the magnetized plasmas, the whistler waves are greatly inhibited for low-velocity pulses and disappear for high-velocity pulses. Additionally, the magnetic field reduces the stopping powers for all high-density cases.

  15. Atomic beam study of a superconductor's magnetic vortex lattice

    International Nuclear Information System (INIS)

    We have developed an atomic beam technique for studying magnetic vortices and vortex lattices of superconductors. Atoms moving near a superconductor's surface see a fluctuating magnetic field as they pass vortices. This field may drive magnetic resonance transitions between hyperfine states. Measuring the magnetic resonance transition probability as a function of atom velocity probes the vortex lattice autocorrelation function. We demonstrate this technique by studying the vortex lattice of a niobium film sample and measuring the sample's penetration depth. We also identify a systematic problem that we think thwarted an earlier attempt to experimentally realize this technique. copyright 1997 The American Physical Society

  16. Control of Beam Halo-Chaos by Fraction Power-Law Function in Hackle Periodic-Focusing Channel

    Institute of Scientific and Technical Information of China (English)

    YU Hai-Jun; BAI Long; WENG Jia-Qiang; LUO Xiao-Shu; FANG Jin-Qing

    2008-01-01

    The Kapehinsky-Vladimirsky (K-V) beam through a hackle periodic-focusing magnetic field is studied using the particle-core model. The beam halo-chaos is found, and an idea of fraction power-law function controller is proposed based on the mechanism of halo formation and the strategy of controlling halo-chaos. The method is applied to the multi-particle simulation to control the halo. The numerical results show that the halo-chaos and its regeneration can be eliminated effectively by using the fraction power-law function control method. At the same time, the radial particle density is uniform at the beam's center as long as the control method and appropriate parameter are chosen.

  17. Analyzer of energy spectra of a magnetized relativistic electron beam

    International Nuclear Information System (INIS)

    Analyzer of magnetized REB instant energy spectrum is described. The analyzer operation principle is based on the application of a sharp change of the direction of force lines of a magnetic field which is non-adiabatic for the beam electrons. The analyzer design is described, the main factors effecting the energy resolution are considered. The analyzer serviceability is examined in the course of experiments on plasma heating using a heavy-current microsecond REB at the GOL-3 device. The analyzer energy resolution which does not exceed 10% at 0.8 MeV energy and 20% at 0.3 MeV is determined. Beam energy spectra are obtained in one of the regimes of beam interaction with plasma. The efficiency of beam interaction with plasma determined using the analyzer achieves 30%. 10 refs.; 7 figs

  18. Beaming of particles and synchrotron radiation in relativistic magnetic reconnection

    CERN Document Server

    Kagan, Daniel; Piran, Tsvi

    2016-01-01

    Relativistic reconnection has been invoked as a mechanism for particle acceleration in numerous astrophysical systems. According to idealised analytical models reconnection produces a bulk relativistic outflow emerging from the reconnection sites (X-points). The resulting radiation is therefore highly beamed. Using two-dimensional particle-in-cell (PIC) simulations, we investigate particle and radiation beaming, finding a very different picture. Instead of having a relativistic average bulk motion with isotropic electron velocity distribution in its rest frame, we find that the bulk motion of particles in X-points is similar to their Lorentz factor gamma, and the particles are beamed within about 5/gamma. On the way from the X-point to the magnetic islands, particles turn in the magnetic field, forming a fan confined to the current sheet. Once they reach the islands they isotropise after completing a full Larmor gyration and their radiation is not strongly beamed anymore. The radiation pattern at a given freq...

  19. Transverse characterization of focused Bessel beams with angular momentum applied to study degree of coherence

    Science.gov (United States)

    He, Xi; Wu, Fengtie; Chen, Ziyang; Pu, Jixiong; Chavez-Cerda, Sabino

    2016-05-01

    The transverse focusing properties at the ‘pseudo-focal’ plane of coherent Bessel beams with angular momentum are analyzed in detail. The transverse magnification of the central dark region of Bessel beams at this pseudo-focal plane is derived for the first time by calculating the ratio of the magnitude of the transverse components of the corresponding wave vectors before and after the focusing lens. We test our results experimentally with coherent laser Bessel beams and excellent agreement is observed. Then, an LED light source is used to generate Bessel beams. By modifying the coherence of the LED light source, we observe that by reducing coherence a smaller and shallower central dark region of Bessel beams with angular momentum is produced at the pseudo-focal plane. This technique can be used as a method to characterize the degree of coherence of vortex beams.

  20. Corrected knife-edge-based reconstruction of tightly focused higher order beams

    CERN Document Server

    Orlov, S; Marchenko, P; Banzer, P; Leuchs, G

    2016-01-01

    The knife-edge method is an established technique for profiling of even tightly focused light beams. However the straightforward implementation of this method fails if the materials and geometry of the knife-edges are not chosen carefully or in particular if knife-edges are used that are made of pure materials. In these cases artifacts are introduced in the shape and position of the reconstructed beam profile due to the interaction of the light beam under study with the knife. Hence, corrections to the standard knife-edge evaluation method are required. Here we investigate the knife-edge method for highly focused radially and azimuthally polarized beams and their linearly polarized constituents. We introduce relative shifts for those constituents and report on the consistency with the case of a linearly polarized Gaussian beam. An adapted knife-edge reconstruction technique is presented and proof-of-concept tests demonstrating the reconstruction of beam profiles are shown.

  1. Transverse characterization of focused Bessel beams with angular momentum applied to study degree of coherence

    International Nuclear Information System (INIS)

    The transverse focusing properties at the ‘pseudo-focal’ plane of coherent Bessel beams with angular momentum are analyzed in detail. The transverse magnification of the central dark region of Bessel beams at this pseudo-focal plane is derived for the first time by calculating the ratio of the magnitude of the transverse components of the corresponding wave vectors before and after the focusing lens. We test our results experimentally with coherent laser Bessel beams and excellent agreement is observed. Then, an LED light source is used to generate Bessel beams. By modifying the coherence of the LED light source, we observe that by reducing coherence a smaller and shallower central dark region of Bessel beams with angular momentum is produced at the pseudo-focal plane. This technique can be used as a method to characterize the degree of coherence of vortex beams. (paper)

  2. About possibilities of obtaining focused beams of thermal neutrons of radionuclide source

    International Nuclear Information System (INIS)

    Full text: In the last years significant progress is achieved in development of neutron focusing methods (concentrating neutrons in a given direction and a small area). In this, main attention is given to focusing of neutron beams of reactor, particularly cold neutrons and their applications. [1,2]. However, isotope sources also let obtain intensive neutron beams and solve quite important (tasks) problems (e.g. neutron capture therapy for malignant tumors) [3], and an actual problems is focusing of neutrons. We developed a device on the basis of californium source of neutrons, allowing to obtain focused (preliminarily) beam of thermal neutrons with the aid of respective choice of moderators, reflectors and geometry of their disposition. Here, fast neutrons and gamma rays in the beam are minimized. With the aid of the model we developed on the basis of Monte-Carlo method, it is possible to modify aforementioned device and dynamics of output neutrons in wide energy range and analyze ways of optimization of neutron beams of isotope sources with different neutron outputs. Device of preliminary focusing of thermal neutrons can serve as a basis for further focus of neutrons using micro- and nano-capillar systems. It is known that, capillary systems performed with certain technology can form beam of thermal neutrons increasing its density by more than two orders of magnitude and effectively divert beams up to 20o with length of system 15 cm

  3. Consequences of the angular spectrum decomposition of a focused beam, including slower than c beam propagation

    Science.gov (United States)

    Gouesbet, Gérard; Lock, James A.

    2016-07-01

    When dealing with light scattering and propagation of an electromagnetic beam, there are essentially two kinds of expansions which have been used to describe the incident beam (i) a discrete expansion involving beam shape coefficients and (ii) a continuous expansion in terms of an angular spectrum of plane waves. In this paper, we demonstrate that the angular spectrum decomposition readily leads to two important consequences, (i) laser light beams travel in free space with an effective velocity that is smaller than the speed of light c, and (ii) the optical theorem does not hold for arbitrary shaped beams, both in the case of electromagnetic waves and scalar waves, e.g. quantum and acoustical waves.

  4. Demonstration of no feasibility of a crystalline beam in a Betatron Magnet II

    International Nuclear Information System (INIS)

    This paper investigates the feasibility of a Crystalline Beam in a weak-focusing Betatron Magnet. The curvature effect due to the bending magnet is also investigated. The case of circular one- dimensional string of electrically-charged particles is examined. It is found that the motion is unstable due to the dependence of the precession movement with the radial displacement. That is a form of negative-mass instability which can be avoided with an alternating-focussing structure. The calculation of the particle-particle interaction as well as of the forces due to the external magnetic field is done directly in the laboratory frame

  5. Evidence for beam self-focusing in the corona of laser-irradiated spherical targets

    International Nuclear Information System (INIS)

    Time integrated photographs have been obtained of the 3/2ω0 harmonic emission from spherical targets irradiated uniformly with a six-beam Nd glass laser system in the ablative mode. Extended filamentary structures are observed which indicate that self-focusing of the incident laser beams in the subcritical density plasma corona is occurring. (author)

  6. Focusing of ion beam with limit emittance by accelerator tube of electrostatic accelerator

    International Nuclear Information System (INIS)

    Focusing of nonrelativistic ion beam with finite emittance by accelerator tube is considered. Analytical relation between positions of the entrance and exit crossovers as a function of the beam emittance and the accelerator tube parameters was obtained. The comparison of conditions providing crossover to crossover transformation and conditions of entrance crossover optical image forming was carried out. 10 refs.; 3 figs

  7. Emittance preservation during bunch compression with a magnetized beam

    Energy Technology Data Exchange (ETDEWEB)

    Stratakis, Diktys [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2015-09-02

    The deleterious effects of coherent synchrotron radiation (CSR) on the phase-space and energy spread of high-energy beams in accelerator light sources can significantly constrain the machine design and performance. In this paper, we present a simple method to preserve the beam emittance by means of using magnetized beams that exhibit a large aspect ratio on their transverse dimensions. The concept is based on combining a finite solenoid field where the beam is generated together with a special optics adapter. Numerical simulations of this new type of beam source show that the induced phase-space density growth can be notably suppressed to less than 1% for any bunch charge. This work elucidates the key parameters that are needed for emittance preservation, such as the required field and aspect ratio for a given bunch charge.

  8. Emittance preservation during bunch compression with a magnetized beam

    Science.gov (United States)

    Stratakis, Diktys

    2016-03-01

    The deleterious effects of coherent synchrotron radiation (CSR) on the phase-space and energy spread of high-energy beams in accelerator light sources can significantly constrain the machine design and performance. In this paper, we present a simple method to preserve the beam emittance by means of using magnetized beams that exhibit a large aspect ratio on their transverse dimensions. The concept is based in combining a finite solenoid field where the beam is generated with a special optics adapter. Numerical simulations of this new type of beam source show that the induced phase-space density growth from CSR can be notably suppressed to less than 1% for any bunch charge. This work elucidates the key parameters that are needed for emittance preservation, such as the required field and aspect ratio for a given bunch charge.

  9. Electron beam characteristics in the hollow beam diode and cusped magnetic field of the Maryland ERA

    International Nuclear Information System (INIS)

    The University of Maryland electron ring accelerator (ERA) concept calls for the formation of an electron ring current by transmission of a hollow relativistic electron beam through a static, azimuthally symmetric, cusped magnetic field. Electron motion is approximately paraxial in the diode and pre-cusp drift region and is axis-encircling in the post-cusp region. Experiments show the electron flow in the diode to be approximately pressureless. The radial thickness of the drifting Brillouin hollow beam is derived from a radial force balance equation. Time-resolved measurements of the beam current and energy are made by measuring the extrapolated range of the beam in aluminum targets. These measurements are analyzed with a model of the diode as a terminating impedance driven by a transmission line. Beam motion in the cusped field region is analyzed. Beam dynamics in the post-cusp region are studied by examining the interaction of a hollow rotating beam with its self-induced potentials in a cylindrical box with conducting walls and ends. The energy of the self-induced electric and magnetic potentials is much less than the kinetic energy of the beam electrons for cases approximating experimental conditions

  10. Versatile AFM setup combined with micro-focused X-ray beam

    CERN Document Server

    Slobodskyy, T; Tholapi, R; Liefeith, L; Fester, M; Sprung, M; Hansen, W

    2015-01-01

    Micro-focused X-ray beams produced by third generation synchrotron sources offer new perspective of studying strains and processes at nanoscale. Atomic force microscope setup combined with a micro-focused synchrotron beam allows precise positioning and nanomanipulation of nanostructures under illumination. In this paper, we report on integration of a portable commercial atomic force microscope setup into a hard X-ray synchrotron beamline. Details of design, sample alignment procedure and performance of the setup are presented.

  11. From x-ray telescopes to neutron scattering: using axisymmetric mirrors to focus a neutron beam

    OpenAIRE

    Khaykovich, B.; Gubarev, M. V.; Bagdasarova, Y.; Ramsey, B. D.; Moncton, D.E.

    2012-01-01

    We demonstrate neutron beam focusing by axisymmetric mirror systems based on a pair of mirrors consisting of a confocal ellipsoid and hyperboloid. Such a system, known as a Wolter mirror configuration, is commonly used in x-ray telescopes. The axisymmetric Wolter geometry allows nesting of several mirror pairs to increase collection efficiency. We have implemented a system containing four nested Ni mirror pairs, which was tested by focusing a polychromatic neutron beam at the MIT Reactor. In ...

  12. Tightly Focusing of Circularly Polarized Vortex Beams through a Uniaxial Birefringent Crystal

    Institute of Scientific and Technical Information of China (English)

    RAO Lian-Zhou; WANG Zong-Chi; ZHENG Xiao-Xia

    2008-01-01

    Under the approximation of small birefringence, the properties of circalarly polarized vortex beams tightly focused through a uniaxial birefringent crystal are studied. With the proper combination of the topological charge and the birefringence, the small focus, the small bottle beam and the inverse c-shaped intensity profile can be obtained.The effects of the focal shift and the Strehl ratio on the birefringence are analysed. A relation between angular momentum (included spin and orbital) and topological Pancharatnam charge is also presented.

  13. Efficient generation and tight focusing of radially polarized beam from linearly polarized beam with all-dielectric metasurface.

    Science.gov (United States)

    Zhang, Fei; Yu, Honglin; Fang, Jiawen; Zhang, Ming; Chen, Sicheng; Wang, Jian; He, Anguo; Chen, Junyan

    2016-03-21

    We propose a single layer all-dielectric metasurface lens to simultaneously convert and focus an incident linear polarization into a radial beam with high efficiency and high numerical aperture (NA). It shows a better focusing property compared with the linearly polarized metasurface lens for high NA. A tight spot size (0.502λ) is achieved for the NA = 0.94. Additionally, the emergent polarization can in principle be switched flexibly between radially and azimuthally polarized beams by the adjustment of incident polarization direction. It is expected that our scheme may have potential value in microscopy, material processing, medicine, particles accelerating and trapping, and so on. PMID:27136854

  14. On the focused beam parameters of an electron gun with a plasma emitter

    Science.gov (United States)

    Kornilov, S.; Rempe, N.; Beniyash, A.; Murray, N.

    2014-11-01

    The report presents the measurement results of the focused beam brightness in the electron gun with plasma emitter. The beam brightness was approximately 1010 A·m-2·sr-1 under the beam power up to 4 kW and an electron energy of 60 keV at the focal distance of 0.5 m. Qualitative assessment of the beam parameters was performed by welding test pieces. The results describing the possibility in principle of using the guns with a plasma emitter in nonvacuum technological devices are presented.

  15. On the focused beam parameters of an electron gun with a plasma emitter

    International Nuclear Information System (INIS)

    The report presents the measurement results of the focused beam brightness in the electron gun with plasma emitter. The beam brightness was approximately 1010 A·m-2·sr-1 under the beam power up to 4 kW and an electron energy of 60 keV at the focal distance of 0.5 m. Qualitative assessment of the beam parameters was performed by welding test pieces. The results describing the possibility in principle of using the guns with a plasma emitter in nonvacuum technological devices are presented

  16. Evaluation of neon focused ion beam milling for TEM sample preparation.

    Science.gov (United States)

    Pekin, T C; Allen, F I; Minor, A M

    2016-10-01

    Gallium-based focused ion beams generated from liquid-metal sources are widely used in micromachining and sample preparation for transmission electron microscopy, with well-known drawbacks such as sample damage and contamination. In this work, an alternative (neon) focused ion beam generated by a gas field-ionization source is evaluated for the preparation of electron-transparent specimens. To do so, electron-transparent sections of Si and an Al alloy are prepared with both Ga and Ne ion beams for direct comparison. Diffraction-contrast imaging and energy dispersive x-ray spectroscopy are used to evaluate the relative damage induced by the two beams, and cross-sections of milled trenches are examined to compare the implantation depth with theoretical predictions from Monte Carlo simulations. Our results show that for the beam voltages and materials systems investigated, Ne ion beam milling does not significantly reduce the focused ion beam induced artefacts. However, the Ne ion beam does enable more precise milling and may be of interest in cases where Ga contamination cannot be tolerated.

  17. PROGRESS IN BEAM FOCUSING AND COMPRESSION FOR WARM-DENSE MATTER EXPERIMENTS

    International Nuclear Information System (INIS)

    The Heavy-Ion Fusion Sciences Virtual National Laboratory is pursuing an approach to target heating experiments in the Warm Dense Matter regime, using space charge-dominated ion beams that are simultaneously longitudinally bunched and transversely focused. Longitudinal beam compression by large factors has been demonstrated in the Neutralized Drift Compression Experiment (NDCX) with controlled ramps and forced neutralization. Using an injected 30-mA K+ ion beam with initial kinetic energy 0.3 MeV, axial compression leading to ∼50-fold current amplification and simultaneous radial focusing to beam radii of a few mm have led to encouraging energy deposition approaching the intensities required for eV-range target heating experiments. We discuss the status of several improvements to our Neutralized Drift Compression Experiment and associated beam diagnostics that are under development to reach the necessary higher beam intensities, including: (1) greater axial compression via a longer velocity ramp using a new bunching module with approximately twice the available volt seconds; (2) improved centroid control via beam steering dipoles to mitigate aberrations in the bunching module; (3) time-dependent focusing elements to correct considerable chromatic aberrations; and (4) plasma injection improvements to establish a plasma density always greater than the beam density, expected to be >1013 cm-3

  18. Focus on Materials Analysis and Processing in Magnetic Fields

    OpenAIRE

    Yoshio Sakka, Noriyuki Hirota, Shigeru Horii and Tsutomu Ando

    2009-01-01

    Recently, interest in the applications of feeble (diamagnetic and paramagnetic) magnetic materials has grown, whereas the popularity of ferromagnetic materials remains steady and high. This trend is due to the progress of superconducting magnet technology, particularly liquid-helium-free superconducting magnets that can generate magnetic fields of 10 T and higher. As the magnetic energy is proportional to the square of the applied magnetic field, the magnetic energy of such 10 T magnets is in...

  19. Dynamic Nonlinear Focal Shift in Amplitude Modulated Moderately Focused Acoustic Beams

    CERN Document Server

    Jiménez, Noé; González-Salido, Nuria

    2016-01-01

    The phenomenon of the displacement of the position of the pressure, intensity and acoustic radiation force maxima along the axis of focused acoustic beams under increasing driving amplitudes (nonlinear focal shift) is studied for the case of a moderately focused beam excited with continuous and 25 kHz amplitude modulated signals, both in water and tissue. We prove that in amplitude modulated beams the linear and nonlinear propagation effects coexist in a semi-period of modulation, giving place to a complex dynamic behaviour, where the singular points of the beam (peak pressure, rarefaction, intensity and acoustic radiation force) locate at different points on axis as a function of time. These entire phenomena are explained in terms of harmonic generation and absorption during the propagation in a lossy nonlinear medium both, for a continuous and an amplitude modulated beam. One of the possible applications of the acoustic radiation force displacement is the generation of shear waves at different locations by ...

  20. Self-Focusing/Defocusing of Chirped Gaussian Laser Beam in Collisional Plasma with Linear Absorption

    Science.gov (United States)

    Wani, Manzoor Ahmad; Kant, Niti

    2016-09-01

    This paper presents an investigation on the self-focusing/defocusing of chirped Gaussian laser beam in collisional plasma with linear absorption. We have derived the differential equation for the beam width parameter by using WKB and paraxial approximations and solved it numerically. The effect of chirp and other laser plasma parameters is seen on the behavior of beam width parameter with dimensionless distance of propagation. The results are discussed and presented graphically. Our simulation results show that the amplitude of oscillations decreases with the distance of propagation. Due to collisional frequency, the laser beam shows fast divergence which can be minimized by the introduction of chirp parameter. The chirp decreases the effect of defocusing and increases the ability of self-focusing of laser beam in collisional plasma. Supported by a financial grant from CSIR, New Delhi, India, under Project No. 03(1277)/13/EMR-II

  1. Investigation of the Chaotic Dynamics of an Electron Beam with a Virtual Cathode in an External Magnetic Field

    CERN Document Server

    Egorov, E N

    2006-01-01

    The effect of the strength of the focusing magnetic field on chaotic dynamic processes occurring inan electron beam with a virtual cathode, as well as on the processes whereby the structures form in the beamand interact with each other, is studied by means of two-dimensional numerical simulations based on solving a self-consistent set of Vlasov-Maxwell equations. It is shown that, as the focusing magnetic field is decreased,the dynamics of an electron beam with a virtual cathode becomes more complicated due to the formation andinteraction of spatio-temporal longitudinal and transverse structures in the interaction region of a vircator. The optimum efficiency of the interaction of an electron beam with the electromagnetic field of the vircator isachieved at a comparatively weak external magnetic field and is determined by the fundamentally two-dimensional nature of the motion of the beam electrons near the virtual cathode.

  2. Focusing and targeting of magnetic brain stimulation using multiple coils.

    Science.gov (United States)

    Ruohonen, J; Ilmoniemi, R J

    1998-05-01

    Neurones can be excited by an externally applied time-varying electromagnetic field. Focused magnetic brain stimulation is attained using multiple small coils instead of one large coil, the resultant induced electric field being a superposition of the fields from each coil. In multichannel magnetic brain stimulation, partial cancellation of fields from individual coils provides a significant improvement in the focusing of the stimulating field, and independent coil channels allow targeting of the stimuli on a given spot without moving the coils. The problem of shaping the stimulating field in multichannel stimulation is analysed, and a method is derived that yields the driving currents required to induce a field with a user-defined shape. The formulation makes use of lead fields and minimum-norm estimation from magneto-encephalography. Using these methods, some properties of multichannel coil arrays are examined. Computer-assisted multichannel stimulation of the cortex will enable several new studies, including quick determination of the cortical regions, the stimulation of which disrupts cortical processing required by a task. PMID:9747568

  3. Boundary effects in finite size plasmonic crystals: focusing and routing of plasmonic beams for optical communications

    Science.gov (United States)

    Benetou, M. I.; Bouillard, J.-S.; Segovia, P.; Dickson, W.; Thomsen, B. C.; Bayvel, P.; Zayats, A. V.

    2015-11-01

    Plasmonic crystals, which consist of periodic arrangements of surface features at a metal-dielectric interface, allow the manipulation of optical information in the form of surface plasmon polaritons. Here we investigate the excitation and propagation of plasmonic beams in and around finite size plasmonic crystals at telecom wavelengths, highlighting the effects of the crystal boundary shape and illumination conditions. Significant differences in broad plasmonic beam generation by crystals of different shapes are demonstrated, while for narrow beams, the propagation from a crystal onto the smooth metal film is less sensitive to the crystal boundary shape. We show that by controlling the boundary shape, the size and the excitation beam parameters, directional control of propagating plasmonic modes and their behaviour such as angular beam splitting, focusing power and beam width can be efficiently achieved. This provides a promising route for robust and alignment-independent integration of plasmonic crystals with optical communication components.

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

    Directory of Open Access Journals (Sweden)

    Muhammad Zubair Khan

    2014-01-01

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

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

    Science.gov (United States)

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

    2014-01-01

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

  6. Study of the production, the propagation and the focusing of an electron beam

    International Nuclear Information System (INIS)

    The electron beam (500 keV, 30 kA, 100 ns) of the RKA (Relativistic Klystron Amplifier) generator is used to study materials under shocks at low fluences (≤ 10 cal/cm2). Their response depends on the beam characteristics at the impact location, mainly in terms of spatial homogeneity. We have used electrical diagnostics as well as an optical diagnostics where the visible photons produced by Cerenkov emission in a silica target are collected by fast cameras. Beam homogeneity has been studied in the vacuum diode as a function of the materials used for the cathode and the anode. Beam propagation and focusing in a chamber filled with a low-pressure gas has also been investigated. Each part of the installation has been optimized during this work. We found that, among the tested materials, a velvet cathode with well-aligned fibers is the best emitter. An anode of thickness about ten micrometers improves the beam homogeneity by scattering of electrons. Next, we focused on beam propagation and focusing in the chamber. For example, a 400 keV, 4.2 kA electron beam can be propagated at constant radius in argon at 0.7 mbar. We performed simulations with the Monte Carlo code Geant4 in order to compute the beam interaction with the Cerenkov target as well as with the anode. Beam emission and propagation were simulated with the PIC code Magic. The good agreement with the experimental results allows us to estimate the electron distributions at any position along the beam path in order to initialize correctly the computation of the beam-material interaction. (author)

  7. Coherence properties of focused X-ray beams at high brilliance synchrotron sources

    CERN Document Server

    Singer, A

    2013-01-01

    An analytical approach describing properties of focused partially coherent X-ray beams is presented. The method is based on the results of statistical optics and gives both the beam size and transverse coherence length at any distance behind an optical element. In particular, here we consider Gaussian Schell-model beams and thin optical elements. Limiting cases of incoherent and fully coherent illumination of the focusing element are discussed. The effect of the beam defining aperture, typically used in combination with focusing elements at synchrotron sources to improve transverse coherence, is also analyzed in detail. As an example the coherence properties in the focal region of compound refractive lenses at the PETRA III synchrotron source are analyzed.

  8. Focusing of heavy ion beams by a high-current plasma lens

    International Nuclear Information System (INIS)

    The results of studies on focusing the wide-aperture heavy ion beams by a high-current electrostatic plasma lens within the range of low (100-400 eV) and medium (5-25 keV) energies are presented. It si established, that due to significant electron leakages the effective focusing of such beams is possible only under the condition of rigid fixation of the external potentials on the plasma lens electrodes. The peculiarities of the lens static and dynamic characteristics under such conditions are studied. The role of spherical and moment aberrations by focusing the wide-aperture weakly-diverging ion beams is identified. It is shown, that the role of the moment aberrations decreases with the energy growth, and focusing of the heavy elements high-current beams by the plasma lens becomes considerably more efficient as compared, to the focusing of the hydrogen light ion beams. This opens the possibility for application of electrostatic plasma lenses for controlling the ion beams in the high-dose ion implanters and in the high-current heavy-ion accelerators

  9. On-chip magnetic bead microarray using hydrodynamic focusing in a passive magnetic separator.

    Science.gov (United States)

    Smistrup, K; Kjeldsen, B G; Reimers, J L; Dufva, M; Petersen, J; Hansen, M F

    2005-11-01

    Implementing DNA and protein microarrays into lab-on-a-chip systems can be problematic since these are sensitive to heat and strong chemicals. Here, we describe the functionalization of a microchannel with two types of magnetic beads using hydrodynamic focusing combined with a passive magnetic separator with arrays of soft magnetic elements. The soft magnetic elements placed on both sides of the channel are magnetized by a relatively weak applied external magnetic field (21 mT) and provide magnetic field gradients attracting magnetic beads. Flows with two differently functionalized magnetic beads and a separating barrier flow are introduced simultaneously at the two channel sides and the centre of the microfluidic channel, respectively. On-chip experiments with fluorescence labeled beads demonstrate that the two types of beads are captured at each of the channel sidewalls. On-chip hybridization experiments show that the microfluidic systems can be functionalized with two sets of beads carrying different probes that selectively recognize a single base pair mismatch in target DNA. By switching the places of the two types of beads it is shown that the microsystem can be cleaned and functionalized repeatedly with different beads with no cross-talk between experiments. PMID:16234958

  10. Bending magnets for the CBA beam-transport line

    Energy Technology Data Exchange (ETDEWEB)

    Thern, R.E.

    1983-01-01

    The beam-transport line from the AGS to CBA requires 68 large bending magnets, consisting of pure dipoles and two types of combined function gradient magnets. All three types were designed with magnetic-field calculation program POISSON, using the same exterior dimensions and coil package. The design goal of +-1% momentum acceptance for the transport line required a wide horizontal aperture, with a much-smaller vertical aperture for economy. Two prototypes of one gradient magnet were built, and a facility constructed to measure them and the later production magnets. Measurements were done using both a long coil and a point coil (Rawson-Lush gaussmeter). Preliminary results show ..delta..B/B < 0.2 x 10/sup -3/, ..delta..G/G < 0.3 x 10/sup -2/, and ..delta..B/sub 2//B < 0.3 x 10/sup -4/ cm/sup -2/ over the beam aperture. Due to end effects, the actual gradient differs from the design gradient by 1%, which has been compensated for in the beam-line design.

  11. Fast magnetic field penetration into an intense neutralized ion beam

    International Nuclear Information System (INIS)

    Experiments involving propagation of neutralized ion beams across a magnetic field indicate a magnetic field penetration time determined by the Hall resistivity rather than the Spitzer or Pedersen resistivity. In magnetohydrodynamics the Hall current is negligible because electrons and ions drift together in response to an electric field perpendicular to the magnetic field. For a propagating neutralized ion beam, the ion orbits are completely different from the electron orbits and the Hall current must be considered. There would be no effect unless there is a component of magnetic field normal to the surface which would usually be absent for a good conductor. It is necessary to consider electron inertia and the consequent penetration of the normal component to a depth c/ωp. In addition it is essential to consider a component of magnetic field parallel to the velocity of the beam which may be initially absent, but is generated by the Hall effect. The penetration time is determined by whistler waves rather than diffusion

  12. Self-focusing and self-compression of a laser pulse in the presence of an external tapered magnetized density-ramp plasma

    Science.gov (United States)

    Saedjalil, N.; Jafari, S.

    2016-06-01

    In this paper, the effects of external tapered axial magnetic field and plasma density-ramp on the spatiotemporal evolution of the laser pulse in inhomogeneous plasma have been studied. The external magnetic field can modify the refractive index of plasma and consequently intensifies the nonlinear effects. By considering the relativistic nonlinearity effect, self-focusing and self-compression of the laser beam propagating through the magnetized plasma have been investigated, numerically. Numerical results indicate that self-focusing and self-compression are better enhanced in a tapered magnetic field than in a uniform one. Besides, in plasma density-ramp profile, self-focusing and self-compression of the laser beam improve in comparison with no ramp structure. In addition, with increasing both the slope of the density ramp and slope constant parameter of the tapered magnetic field, the laser focusing increases, properly, in short distances of the laser propagation through the plasma.

  13. Focusing a TM(01) beam with a slightly tilted parabolic mirror.

    Science.gov (United States)

    April, Alexandre; Bilodeau, Pierrick; Piché, Michel

    2011-05-01

    A parabolic mirror illuminated with an incident collimated beam whose axis of propagation does not exactly coincide with the axis of revolution of the mirror shows distortion and strong coma. To understand the behavior of such a focused beam, a detailed description of the electric field in the focal region of a parabolic mirror illuminated with a beam having a nonzero angle of incidence is required. We use the Richards-Wolf vector field equation to investigate the electric energy density distribution of a beam focused with a parabolic mirror. The explicit aberration function of this focused field is provided along with numerically calculated electric energy densities in the focal region for different angles of incidence. The location of the peak intensity, the Strehl ratio and the full-width at half-maximum as a function of the angle of incidence are given and discussed. The results confirm that the focal spot of a strongly focused beam is affected by severe coma, even for very small tilting of the mirror. This analysis provides a clearer understanding of the effect of the angle of incidence on the focusing properties of a parabolic mirror as such a focusing device is of growing interest in microscopy.

  14. Suppressing Transverse Beam Halo with Nonlinear Magnetic Fields

    CERN Document Server

    Webb, Stephen D; Abell, Dan T; Danilov, Viatcheslav; Nagaitsev, Sergei; Valishev, Alexander; Danilov, Kirill; Cary, John R

    2012-01-01

    High intensity proton storage rings are central for the development of advanced neutron sources, drivers for the production of pions in neutrino factories or muon colliders, and transmutation of radioactive waste. Fractional proton loss from the beam must be very small to prevent radioac- tivation of nearby structures, but many sources of beam loss are driven by collective effects that increase with intensity. Recent theoretical work on the use of nonlinear magnetic fields to design storage rings with integrable transverse dynamics is extended here to include collective effects, with numerical results showing validity in the presence of very high beam current. Among these effects is the formation of beam halo, where particles are driven to large amplitude oscillations by coherent space charge forces. The strong variation of particle oscillation frequency with amplitude results in nonlinear decoherence that is observed to suppress transverse halo development in the case studied. We also present a necessary gen...

  15. Pulse splitting of self-focusing-beams in normally dispersive media

    DEFF Research Database (Denmark)

    Bergé, L.; Juul Rasmussen, J.

    1996-01-01

    The influence of the normal group-velocity dispersion on anisotropic self-focusing beams in nonlinear Kerr media is studied analytically. It is shown that a light pulse self-focusing in the presence of normal dispersion is split up into several small-scale cells preventing a catastrophic collapse...

  16. Characterization of focused beam of desktop 10-Hz capillary-discharge 46.9-nm laser

    Science.gov (United States)

    Vyšin, Ludek; Burian, Tomás; Chalupský, Jaromír; Grisham, Michael; Hájková, Vera; Heinbuch, Scott; Jakubczak, Krzysztof; Martz, Dale; Mocek, Tomás; Pira, Peter; Polan, Jirí; Rocca, Jorge J.; Rus, Bedrich; Sobota, Jaroslav; Juha, Libor

    2009-05-01

    The desktop capillary-discharge Ne-like Ar laser (CDL) providing 10-μJ nanosecond pulses of coherent 46.9-nm radiation with a repetition rate up to 12 Hz was developed and built at the Colorado State University in Fort Collins and then installed in Prague. The beam of the laser was focused by a spherical mirror covered with Si/Sc multilayer coating onto the surface of poly(methyl methacrylate) - PMMA. Interaction parameters vary by changing the distance between sample surface and beam focus. The samples were exposed to various numbers of shots. Analysis of damaged PMMA by atomic force (AFM) and Nomarski (DIC - differential interference contrast) microscopes allows not only to determine the key characteristics of the focused beam (e.g. Rayleigh's parameter, focal spot diameter, tight focus position, etc.) but also to investigate mechanisms of the radiation-induced erosion processes.

  17. Focusing characteristics of an accelerating structure with non-circular beam holes

    International Nuclear Information System (INIS)

    High energy linacs of the next generation are required to keep stably high bunch populations and very small beam spots at colliding points, in order to realize high luminosity at TeV energy region. CERN proposed to apply the rf focusing technology which makes a strong focusing force according to the rf phase within a bunch, and rf focusing power is proportional to both the accelerating gradient and the operating frequency. Some computed results of the focusing property of 3 GHz accelerating structures are presented which has non-circular beam holes. The construction of this 3 GHz structure, because an rf technology for 3 GHz is well-established, will be useful in order to know, at an early stage of the development, whether the idea will be successful or not. The 3D code MAFIA was used to investigate the deflecting force caused by the asymmetry of the beam aperture. (R.P.) 5 refs., 14 figs., 3 tabs

  18. Self-Focusing of Hermite-Cosh-Gaussian Laser Beams in Plasma under Density Transition

    Directory of Open Access Journals (Sweden)

    Manzoor Ahmad Wani

    2014-01-01

    Full Text Available Self-focusing of Hermite-Cosh-Gaussian (HChG laser beam in plasma under density transition has been discussed here. The field distribution in the medium is expressed in terms of beam-width parameters and decentered parameter. The differential equations for the beam-width parameters are established by a parabolic wave equation approach under paraxial approximation. To overcome the defocusing, localized upward plasma density ramp is considered, so that the laser beam is focused on a small spot size. Plasma density ramp plays an important role in reducing the defocusing effect and maintaining the focal spot size up to several Rayleigh lengths. To discuss the nature of self-focusing, the behaviour of beam-width parameters with dimensionless distance of propagation for various values of decentered parameters is examined by numerical estimates. The results are presented graphically and the effect of plasma density ramp and decentered parameter on self-focusing of the beams has been discussed.

  19. Focusing of heavy ion beams by a high-current plasma lens

    International Nuclear Information System (INIS)

    Results are presented from studies of the focusing of wide-aperture low-energy (100-400 eV) and moderate-energy (5-25 keV) beams of heavy-metal ions by a high-current electrostatic plasma lens. It is found experimentally that, because of the significant electron losses, the efficient focusing of such beams can be achieved only if the external potentials at the plasma-lens electrodes are maintained constant. Static and dynamic characteristics of the lens are studied under these conditions. It is shown that, as the beam current and the electrode voltage increase, the maximum electrostatic field in the lens tends to a certain limiting value because of the increase in the spatial potential near the lens axis. The role of spherical and moment aberrations in the focusing of wide-aperture low-divergence ion beams is revealed. It is shown that, even when spherical aberrations are minimized, unremovable moment aberrations decrease the maximum compression ratio of a low-energy heavy-ion beam because of the charge separation of multiply charged ions in the focal region. At the same time, as the ion energy increases, the role of the moment aberrations decreases and the focusing of high-current heavy-ion beams by a plasma lens becomes more efficient than the focusing of light-ion (hydrogen) beams. This opens up the possibility of using electrostatic plasma lenses to control ion beams in high-dose ion implanters and high-current accelerators of heavy ions

  20. Collection and focusing of laser accelerated ion beams for therapy applications

    Science.gov (United States)

    Hofmann, Ingo; Meyer-Ter-Vehn, Jürgen; Yan, Xueqing; Orzhekhovskaya, Anna; Yaramyshev, Stepan

    2011-03-01

    Experimental results in laser acceleration of protons and ions and theoretical predictions that the currently achieved energies might be raised by factors 5-10 in the next few years have stimulated research exploring this new technology for oncology as a compact alternative to conventional synchrotron based accelerator technology. The emphasis of this paper is on collection and focusing of the laser produced particles by using simulation data from a specific laser acceleration model. We present a scaling law for the “chromatic emittance” of the collector—here assumed as a solenoid lens—and apply it to the particle energy and angular spectra of the simulation output. For a 10 Hz laser system we find that particle collection by a solenoid magnet well satisfies requirements of intensity and beam quality as needed for depth scanning irradiation. This includes a sufficiently large safety margin for intensity, whereas a scheme without collection—by using mere aperture collimation—hardly reaches the needed intensities.

  1. Controlling the optical fiber output beam profile by focused ion beam machining of a phase hologram on fiber tip.

    Science.gov (United States)

    Han, Jiho; Sparkes, Martin; O'Neill, William

    2015-02-01

    A phase hologram was machined on an optical fiber tip using a focused ion beam (FIB) system so that a ring-shaped beam emerges from the fiber tip. The fiber used for this work was a commercial single-mode optical fiber patch cable for a design wavelength of 633 nm with a germanosilicate core. The ring-shaped beam was chosen to ensure a simple geometry in the required phase hologram, though the Gerchberg-Saxton algorithm can be used to calculate a hologram for an arbitrary beam shape. The FIB machining took approximately 45 min at 30 kV and 200 pA. The radius of the resulting ring beam was 0.083 m at 1 m standoff, as compared to 0.1 m as was initially desired. Results suggest that this imaging technique may provide a basis for a beam-shaping method with several advantages over the current commercial solutions, having permanent alignment, compactness, and mechanical robustness. However, it would appear that minimizing the speckle pattern will remain a critical challenge for this technique to become widely implemented.

  2. Present status and first results of the final focus beam line at the KEK Accelerator Test Facility

    CERN Document Server

    Bambade, P; Amann, J; Angal-Kalinin, D; Apsimon, R; Araki, S; Aryshev, A; Bai, S; Bellomo, P; Bett, D; Blair, G; Bolzon, B; Boogert, S; Boorman, G; Burrows, P N; Christian, G; Coe, P; Constance, B; Delahaye, J P; Deacon, L; Elsen, E; Faus-Golfe, A; Fukuda, M; Gao, J; Geffroy, N; Gianfelice-Wendt, E; Guler, H; Hayano, H; Heo, A Y; Honda, Y; Huang, J Y; Hwang, W H; Iwashita, Y; Jeremie, A; Jones, J; Kamiya, Y; Karataev, P; Kim, E S; Kim, H S; Kim, S H; Komamiya, S; Kubo, K; Kume, T; Kuroda, S; Lam, B; Lyapin, A; Masuzawa, M; McCormick, D; Molloy, S; Naito, T; Nakamura, T; Nelson, J; Okamoto, D; Okugi, T; Oroku, M; Park, Y J; Parker, B; Paterson, E; Perry, C; Pivi, M; Raubenheimer, T; Renier, Y; Resta-Lopez, J; Rimbault, C; Ross, M; Sanuki, T; Scarfe, A; Schulte, D; Seryi, A; Spencer, C; Suehara, T; Sugahara, R; Swinson, C; Takahashi, T; Tauchi, T; Terunuma, N; Tomas, R; Urakawa, J; Urner, D; Verderi, M; Wang, M H; Warden, M; Wendt, M; White, G; Wittmer, W; Wolski, A; Woodley, M; Yamaguchi, Y; Yamanaka, T; Yan, Y; Yoda, H; Yokoya, K; Zhou, F; Zimmermann, F

    2010-01-01

    ATF2 is a final-focus test beam line which aims to focus the low emittance beam from the ATF damping ring to a vertical size of about 37 nm and to demonstrate nanometer level beam stability. Several advanced beam diagnostics and feedback tools are used. In December 2008, construction and installation were completed and beam commissioning started, supported by an international team of Asian, European, and U.S. scientists. The present status and first results are described.

  3. Present Status And First Results of the Final Focus Beam Line at the KEK Accelerator Test Facility

    Energy Technology Data Exchange (ETDEWEB)

    Bambade, P.; /Orsay /KEK, Tsukuba; Alabau Pons, M.; /Valencia U., IFIC; Amann, J.; /SLAC; Angal-Kalinin, D.; /Daresbury; Apsimon, R.; /Oxford U., JAI; Araki, S.; Aryshev, A.; /KEK, Tsukuba; Bai, S.; /Beijing, Inst. High Energy Phys.; Bellomo, P.; /SLAC; Bett, D.; /Oxford U., JAI; Blair, G.; /Royal Holloway, U. of London; Bolzon, B.; /Savoie U.; Boogert, S.; Boorman, G.; /Royal Holloway, U. of London; Burrows, P.N.; Christian, G.; Coe, P.; Constance, B.; /Oxford U., JAI; Delahaye, Jean-Pierre; /CERN; Deacon, L.; /Royal Holloway, U. of London; Elsen, E.; /DESY /Valencia U., IFIC /KEK, Tsukuba /Beijing, Inst. High Energy Phys. /Savoie U. /Fermilab /Ecole Polytechnique /KEK, Tsukuba /Kyungpook Natl. U. /KEK, Tsukuba /Pohang Accelerator Lab. /Kyoto U., Inst. Chem. Res. /Savoie U. /Daresbury /Tokyo U. /Royal Holloway, U. of London /Kyungpook Natl. U. /Pohang Accelerator Lab. /Tokyo U. /KEK, Tsukuba /SLAC /University Coll. London /KEK, Tsukuba /SLAC /Royal Holloway, U. of London /KEK, Tsukuba /Tokyo U. /SLAC /Tohoku U. /KEK, Tsukuba /Tokyo U. /Pohang Accelerator Lab. /Brookhaven /SLAC /Oxford U., JAI /SLAC /Orsay /KEK, Tsukuba /Oxford U., JAI /Orsay /Fermilab /Tohoku U. /Manchester U. /CERN /SLAC /Tokyo U. /KEK, Tsukuba /Oxford U., JAI /Hiroshima U. /KEK, Tsukuba /CERN /KEK, Tsukuba /Oxford U., JAI /Ecole Polytechnique /SLAC /Oxford U., JAI /Fermilab /SLAC /Liverpool U. /SLAC /Tokyo U. /SLAC /Tokyo U. /KEK, Tsukuba /SLAC /CERN

    2011-11-11

    ATF2 is a final-focus test beam line which aims to focus the low emittance beam from the ATF damping ring to a vertical size of about 37 nm and to demonstrate nanometer level beam stability. Several advanced beam diagnostics and feedback tools are used. In December 2008, construction and installation were completed and beam commissioning started, supported by an international team of Asian, European, and U.S. scientists. The present status and first results are described.

  4. Optical simulation of laser beam phase-shaping focusing optimization in biological tissues

    Science.gov (United States)

    Gomes, Ricardo; Vieira, Pedro; Coelho, João. M. P.

    2013-11-01

    In this paper we report the development of an optical simulator that can be used in the development of methodologies for compensate/decrease the light scattering effect of most biological tissues through phase-shaping methods. In fact, scattering has long been a major limitation for the medical applications of lasers where in-depth tissues concerns due to the turbid nature of most biological media in the human body. In developing the simulator, two different approaches were followed: one using multiple identical beams directed to the same target area and the other using a phase-shaped beam. In the multiple identical beams approach (used mainly to illustrate the limiting effect of scattering on the beam's propagation) there was no improvement in the beam focus at 1 mm compared to a single beam layout but, in phase-shaped beam approach, a 8x improvement on the radius of the beam at the same depth was achieved. The models were created using the optical design software Zemax and numerical algorithms created in Matlab programming language to shape the beam wavefront. A dedicated toolbox allowed communication between both programs. The use of the two software's proves to be a simple and powerful solution combining the best of the two and allowing a significant potential for adapting the simulations to new systems and thus allow to assess their response and define critical engineering parameters prior to laboratorial implementation.

  5. Transport properties of modulation-doped structures grown by molecular beam epitaxy after focused ion beam implantation

    International Nuclear Information System (INIS)

    Modulation-doped structures are grown by molecular beam epitaxy after focused ion beam writing. The growth and implantation chambers are connected in a high vacuum to minimize the effect of growth interruption. The electron channel is drastically depleted by the buried Be+ implanted region, but only slightly depleted by the buried Au+ and Au2+ implanted regions. This is because Be+ implantation forms a p-type material, while Au+ or Au2+ implantation leaves damage only in the n-type material. Be+ implantation is therefore used to fabricate 0.1 μm-wide wires with electron mobility of 2.1x105 cm2/Vs. (author)

  6. Planar electron beams in a wiggler magnet array

    Indian Academy of Sciences (India)

    Arti Hadap; K C Mittal

    2013-02-01

    Transport of high current (∼kA range with particle energy ∼ 1 MeV) planar electron beams is a topic of increasing interest for applications in high-power (1–10 GW) and high-frequency (10–20 GHz) microwave devices such as backward wave oscillator (BWO), klystrons, gyro-BWOs, etc. In this paper, we give a simulated result for transport of electron beams with velocity $V_{b} = 5.23 × 10^{8}$ cm s-1 , relativistic factor = 1.16, and beam voltage = ∼80 kV in notched wiggler magnet array. The calculation includes self-consistent effects of beam-generated fields. Our results show that the notched wiggler configuration with ∼6.97 kG magnetic field strength can provide vertical and horizontal confinements for a sheet electron beam with 0.3 cm thickness and 2 cm width. The feasibility calculation addresses to a system expected to drive for 13–20 GHz BWO with rippled waveguide parameters as width = 3.0 cm, thickness = 1.0 cm, corrugation depth ℎ = 0.225 cm, and spatial periodicity = 1.67 cm.

  7. In situ nanomechanical testing in focused ion beam and scanning electron microscopes

    Energy Technology Data Exchange (ETDEWEB)

    Gianola, D. S. [Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States); Institute for Applied Materials, Karlsruhe Institute of Technology, Karlsruhe (Germany); Sedlmayr, A.; Moenig, R.; Kraft, O. [Institute for Applied Materials, Karlsruhe Institute of Technology, Karlsruhe (Germany); Volkert, C. A. [Institute for Materials Physics, Georg-August University of Goettingen, Goettingen (Germany); Major, R. C.; Cyrankowski, E.; Asif, S. A. S.; Warren, O. L. [Hysitron, Inc., Minneapolis, Minnesota 55344 (United States)

    2011-06-15

    The recent interest in size-dependent deformation of micro- and nanoscale materials has paralleled both technological miniaturization and advancements in imaging and small-scale mechanical testing methods. Here we describe a quantitative in situ nanomechanical testing approach adapted to a dual-beam focused ion beam and scanning electron microscope. A transducer based on a three-plate capacitor system is used for high-fidelity force and displacement measurements. Specimen manipulation, transfer, and alignment are performed using a manipulator, independently controlled positioners, and the focused ion beam. Gripping of specimens is achieved using electron-beam assisted Pt-organic deposition. Local strain measurements are obtained using digital image correlation of electron images taken during testing. Examples showing results for tensile testing of single-crystalline metallic nanowires and compression of nanoporous Au pillars will be presented in the context of size effects on mechanical behavior and highlight some of the challenges of conducting nanomechanical testing in vacuum environments.

  8. In situ nanomechanical testing in focused ion beam and scanning electron microscopes.

    Science.gov (United States)

    Gianola, D S; Sedlmayr, A; Mönig, R; Volkert, C A; Major, R C; Cyrankowski, E; Asif, S A S; Warren, O L; Kraft, O

    2011-06-01

    The recent interest in size-dependent deformation of micro- and nanoscale materials has paralleled both technological miniaturization and advancements in imaging and small-scale mechanical testing methods. Here we describe a quantitative in situ nanomechanical testing approach adapted to a dual-beam focused ion beam and scanning electron microscope. A transducer based on a three-plate capacitor system is used for high-fidelity force and displacement measurements. Specimen manipulation, transfer, and alignment are performed using a manipulator, independently controlled positioners, and the focused ion beam. Gripping of specimens is achieved using electron-beam assisted Pt-organic deposition. Local strain measurements are obtained using digital image correlation of electron images taken during testing. Examples showing results for tensile testing of single-crystalline metallic nanowires and compression of nanoporous Au pillars will be presented in the context of size effects on mechanical behavior and highlight some of the challenges of conducting nanomechanical testing in vacuum environments.

  9. Self-focusing and defocusing of Gaussian laser beams in plasmas with linear temperature ramp

    International Nuclear Information System (INIS)

    The propagation characteristics of the Gaussian laser beam in plasmas in the presence of a linear electron temperature ramp have been investigated by taking the electron temperature as an individual variable. The ponderomotive force and collision have been considered as the mechanisms of nonlinearity. The second order differential equation of the dimensionless beam-width parameter has been acquired and solved with several initial electron temperatures and plus-minus temperature ramp parameters. The propagation regimes of laser beam are found to be sensitive with the selection of electron temperature. The linear temperature ramp breaks the stationary propagating mode and enhances the self-focusing or defocusing propagation properties. Results indicate the feasibility of extended propagation of focused laser beam in plasmas by modifying the electron temperature.

  10. Neutron and Ion Beams Emitted from Plasma Focus (112.5 J) Device

    Science.gov (United States)

    El-Aragi M., G.

    2010-02-01

    Preliminary results of recent experiments performed within the Mather-type 112.5 J plasma focus device are presented. The ion beams from the focus device operated with deuterium filling at 1 mbar were registered using CR-39 solid state nuclear track detectors (SSNTD) and a Faraday cup detector for time-resolved measurements. The time-resolved neutron emission from the focus region measurements was detected with a photomultiplier tube (IP-28) optically coupled with a plastic scintillator NE 102.

  11. Surface profiling of X-ray mirrors for shaping focused beams.

    Science.gov (United States)

    Laundy, David; Alianelli, Lucia; Sutter, John; Evans, Gwyndaf; Sawhney, Kawal

    2015-01-26

    Grazing incidence mirrors are a standard optic for focusing X-rays. Active mirrors, whose surface profile can be finely adjusted, allow control of beam shape and size at the sample. However, progress towards their routine use for beam shaping has been hampered by the strong striations in reflected beams away from the focal plane. Re-entrant (partly concave and partly convex) surface modifications are proposed for shaping X-ray beams to a top-hat in the focal plane while reducing the striations caused by unavoidable polishing errors. A method for constructing such surfaces with continuous height and slope (but only piecewise continuous curvature) will be provided. Ray tracing and wave propagation calculations confirm its effectiveness. A mirror system is proposed allowing vertical beam sizes in the range 0.5 to 10μm. A prototype will be fabricated and is expected to have applications on many synchrotron X-ray beamlines.

  12. Angular anisoplanatism of a focused beam using beacons over horizontal path

    Science.gov (United States)

    Wu, Wu-ming; Ning, Yu

    2016-01-01

    The performance of the achieve laser beam propagation through atmospheric turbulence with adaptive optics is degraded by the fact that the wavefront aberrations difference. This error is only include the angular anisoplanatism when there is separation between the achieve laser beam and beacon. In the paper we derive an analytic expression for the effective angular anisoplanatism as a function of displacement angular when the turbulence profile is uniform. It shows that the effective angular anisoplanatism becomes weaker as the diameter of laser beams and the Fried transverse coherence length increase. We report results from field experiments that the effective angular anisoplanatism of a focused beam over horizontal path. It is found that measured and theoretical results are consistent. The effective wavefront variance increases with the strength of atmospheric turbulence and the angular displacement. And the constant phase of angular anisoplanatism has no effect on the Strehl ratio of the beam.

  13. Focused electron beam induced etching of titanium with XeF{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Schoenaker, F J; Cordoba, R; Fernandez-Pacheco, R; Magen, C; Zuriaga-Monroy, C; Ibarra, M R [Instituto de Nanociencia de Aragon, Universidad de Zaragoza, E-50018 Zaragoza (Spain); Stephan, O [Laboratoire de Physique des Solides, CNRS UMR 8502, Universite Paris Sud XI, Batiment 510, F-91405 Orsay (France); De Teresa, J M, E-mail: deteresa@unizar.es [Departamento de Fisica de la Materia Condensada, Universidad de Zaragoza, E-50009 Zaragoza (Spain)

    2011-07-01

    Titanium is a relevant technological material due to its extraordinary mechanical and biocompatible properties, its nanopatterning being an increasingly important requirement in many applications. We report the successful nanopatterning of titanium by means of focused electron beam induced etching using XeF{sub 2} as a precursor gas. Etch rates up to 1.25 x 10{sup -3} {mu}m{sup 3} s{sup -1} and minimum pattern sizes of 80 nm were obtained. Different etching parameters such as beam current, beam energy, dwell time and pixel spacing are systematically investigated, the etching process being optimized by decreasing both the beam current and the beam energy. The etching mechanism is investigated by transmission electron microscopy. Potential applications in nanotechnology are discussed.

  14. Investigation of the Chaotic Dynamics of an Electron Beam with a Virtual Cathode in an External Magnetic Field

    OpenAIRE

    Egorov, E. N.; Hramov, A. E.

    2006-01-01

    The effect of the strength of the focusing magnetic field on chaotic dynamic processes occurring inan electron beam with a virtual cathode, as well as on the processes whereby the structures form in the beamand interact with each other, is studied by means of two-dimensional numerical simulations based on solving a self-consistent set of Vlasov-Maxwell equations. It is shown that, as the focusing magnetic field is decreased,the dynamics of an electron beam with a virtual cathode becomes more ...

  15. Beam induced electron cloud resonances in dipole magnetic fields

    Science.gov (United States)

    Calvey, J. R.; Hartung, W.; Makita, J.; Venturini, M.

    2016-07-01

    The buildup of low energy electrons in an accelerator, known as electron cloud, can be severely detrimental to machine performance. Under certain beam conditions, the beam can become resonant with the cloud dynamics, accelerating the buildup of electrons. This paper will examine two such effects: multipacting resonances, in which the cloud development time is resonant with the bunch spacing, and cyclotron resonances, in which the cyclotron period of electrons in a magnetic field is a multiple of bunch spacing. Both resonances have been studied directly in dipole fields using retarding field analyzers installed in the Cornell Electron Storage Ring. These measurements are supported by both analytical models and computer simulations.

  16. Superconductivity of ultra-fine tungsten nanowires grown by focused-ion-beam direct-writing

    OpenAIRE

    Li, W.X.; Fenton, J. C.; Gu, C. Z.; Warburton, P. A.

    2011-01-01

    The electrical properties of lateral ultra-fine tungsten nanowires, which were grown by focused-ion-beam-induced deposition with 1 pA ion-beam current, were investigated. Temperature-dependent electrical measurements show that the wires are conducting and have a superconducting transition with a transition temperature (T-c) about 5.1 K. Resistance vs. temperature measurements reveal that, with decreasing cross-sectional area, the wires display an increasingly broad superconducting transition....

  17. 3D micro-optical elements for generation of tightly focused vortex beams

    OpenAIRE

    Balčytis Armandas; Hakobyan Davit; Gabalis Martynas; Žukauskas Albertas; Urbonas Darius; Malinauskas Mangirdas; Petruškevičius Raimondas; Brasselet Etienne; Juodkazis Saulius

    2015-01-01

    Orbital angular momentum carrying light beams are usedfor optical trapping and manipulation. This emerging trend provides new challenges involving device miniaturization for improved performance and enhanced functionality at the microscale. Here we discus a new fabrication method based on combining the additive 3D structuring capability laser photopolymerization and the substractive sub-wavelength resolution patterning of focused ion beam lithography to produce micro-optical elements capable ...

  18. Beaming of Particles and Synchrotron Radiation in Relativistic Magnetic Reconnection

    Science.gov (United States)

    Kagan, Daniel; Nakar, Ehud; Piran, Tsvi

    2016-08-01

    Relativistic reconnection has been invoked as a mechanism for particle acceleration in numerous astrophysical systems. According to idealized analytical models, reconnection produces a bulk relativistic outflow emerging from the reconnection sites (X-points). The resulting radiation is therefore highly beamed. Using two-dimensional particle-in-cell simulations, we investigate particle and radiation beaming, finding a very different picture. Instead of having a relativistic average bulk motion with an isotropic electron velocity distribution in its rest frame, we find that the bulk motion of the particles in X-points is similar to their Lorentz factor γ, and the particles are beamed within ˜ 5/γ . On the way from the X-point to the magnetic islands, particles turn in the magnetic field, forming a fan confined to the current sheet. Once they reach the islands they isotropize after completing a full Larmor gyration and their radiation is no longer strongly beamed. The radiation pattern at a given frequency depends on where the corresponding emitting electrons radiate their energy. Lower-energy particles that cool slowly spend most of their time in the islands and their radiation is not highly beamed. Only particles that quickly cool at the edge of the X-points generate a highly beamed fan-like radiation pattern. The radiation emerging from these fast cooling particles is above the burn-off limit (˜100 MeV in the overall rest frame of the reconnecting plasma). This has significant implications for models of gamma-ray bursts and active galactic nuclei that invoke beaming in that frame at much lower energies.

  19. A focusable, convergent fast-electron beam from ultra-high-intensity laser-solid interactions

    CERN Document Server

    Scott, R H H

    2015-01-01

    A novel scheme for the creation of a convergent, or focussing, fast-electron beam generated from ultra-high-intensity laser-solid interactions is described. Self-consistent particle-in-cell simulations are used to demonstrate the efficacy of this scheme in two dimensions. It is shown that a beam of fast-electrons of energy 500 keV - 3 MeV propagates within a solid-density plasma, focussing at depth. The depth of focus of the fast-electron beam is controlled via the target dimensions and focussing optics.

  20. Lateral resolution in focused electron beam-induced deposition: scaling laws for pulsed and static exposure

    Energy Technology Data Exchange (ETDEWEB)

    Szkudlarek, Aleksandra [Empa, Laboratory for Mechanics of Materials and Nanostructures, Thun (Switzerland); AGH University of Science and Technology, Department of Solid State Physics, Faculty of Physics and Applied Computer Science, Krakow (Poland); Szmyt, Wojciech; Kapusta, Czeslaw [AGH University of Science and Technology, Department of Solid State Physics, Faculty of Physics and Applied Computer Science, Krakow (Poland); Utke, Ivo [Empa, Laboratory for Mechanics of Materials and Nanostructures, Thun (Switzerland)

    2014-12-15

    In this work, we review the single-adsorbate time-dependent continuum model for focused electron beam-induced deposition (FEBID). The differential equation for the adsorption rate will be expressed by dimensionless parameters describing the contributions of adsorption, desorption, dissociation, and the surface diffusion of the precursor adsorbates. The contributions are individually presented in order to elucidate their influence during variations in the electron beam exposure time. The findings are condensed into three new scaling laws for pulsed exposure FEBID (or FEB-induced etching) relating the lateral resolution of deposits or etch pits to surface diffusion and electron beam exposure dwell time for a given adsorbate depletion state. (orig.)

  1. Energy Loss of High Intensity Focused Proton Beams Penetrating Metal Foils

    Science.gov (United States)

    McGuffey, C.; Qiao, B.; Kim, J.; Beg, F. N.; Wei, M. S.; Evans, M.; Fitzsimmons, P.; Stephens, R. B.; Chen, S. N.; Fuchs, J.; Nilson, P. M.; Canning, D.; Mastrosimone, D.; Foord, M. E.

    2014-10-01

    Shortpulse-laser-driven intense ion beams are appealing for applications in probing and creating high energy density plasmas. Such a beam isochorically heats and rapidly ionizes any target it enters into warm dense matter with uncertain transport and stopping properties. Here we present experimental measurements taken with the 1.25 kJ, 10 ps OMEGA EP BL shortpulse laser of the proton and carbon spectra after passing through metal foils. The laser irradiated spherically curved C targets with intensity 4×1018 W/cm2, producing proton beams with 3 MeV slope temperature and a sharp low energy cutoff at 5 MeV which has not been observed on lower energy, shorter pulse intense lasers. The beam either diverged freely or was focused to estimated 1016 p +/cm2 ps by a surrounding structure before entering the metal foils (Al or Ag and a Cu tracer layer). The proton and ion spectra were altered by the foil depending on material and whether or not the beam was focused. Transverse proton radiography probed the target with ps temporal and 10 micron spatial resolution, indicating an electrostatic field on the foil may also have affected the beam. We present complementary particle-in-cell simulations of the beam generation and transport to the foils. This work was supported by the DOE/NNSA National Laser User Facility program, Contract DE-SC0001265.

  2. Using Focused Electron Beams to Drill Straight Nanopores on a Membrane

    Directory of Open Access Journals (Sweden)

    Yung-Cheng Wang

    2014-08-01

    Full Text Available A high-resolution focused electron beam is used for the fabrication of metal nanostructures and devices with insulating membranes by nanosculpting metal films. This top-down focused electron beam drilling method uses the controlled ablation of materials to produce nanoscale devices with near-atomic precision of order. Using the proposed procedure, nano-drilling is not directly realized through the aperture, but by using a focused electron beam to burn away the solvent. Recent studies have investigated silicon nitride nanopores with an hourglass profile and silica nanopores with a pyramid-shaped cross-section, but electronic drilling in these approaches failed to produce straight nanopores. A method is proposed to improve the membranes’ thermal conductivity to rapidly produce straight nanopores, and is experimentally confirmed and has significant potential for use in nano-sensors or nano-devices.

  3. Tight focus of a radially polarized and amplitude-modulated annular multi-Gaussian beam

    International Nuclear Information System (INIS)

    The focusing of a radially polarized beam without annular apodization ora phase filter at the entrance pupil of the objective results in a wide focus and low purity of the longitudinally polarized component. However, the presence of a physical annular apodization or phase filter makes some applications more difficult or even impossible. We propose a radially polarized and amplitude-modulated annular multi-Gaussian beam mode. Numerical simulation shows that it can be focused into a sharper focal spot of 0.125λ2 without additional apodizations or filters. The beam quality describing the purity of longitudinally polarized component is up to 86%. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  4. Identification and reduction of acoustic-noise influence on focused ion beam (FIB)

    Energy Technology Data Exchange (ETDEWEB)

    Pluska, M.; Czerwinski, A.; Wzorek, M.; Juchniewicz, M.; Kątcki, J.

    2015-04-01

    The use of focused ion beam (FIB) for research or processing of nanostructures requires very accurate beam positioning. However, numerous reasons for beam-position fluctuations exist. When FIB is used for specimen imaging, then these beam fluctuations cause the image jitter, blur or specimen-edge deformation. Similarly, beam fluctuations decrease the spatial resolution of FIB-based technological processes of milling or deposition. The sources of fluctuations are electromagnetic interference (EMI), floor vibrations and airborne acoustic noise. Our work concerns acoustic noise impact on focused ion beam fluctuations. The measurements were carried out on Helios NanoLab 600 DualBeam system with ion and electron beam columns. Reference specimens were imaged by electron or ion beam while acoustic waves of different frequency, magnitude and direction were intentionally generated nearby the system. It was found that while EMI-related distortions are caused by a wide and continuous spectrum of frequencies, for acoustic noise the strong deformations of image occur only at several resonant frequencies (mainly in the range 100–400 Hz). Comparison of results obtained for either electron or ion beam allowed to attribute different resonant peaks to various FIB-system components (ion column, electron column, specimen stage). Spectral analysis showed that resonant components of the acoustic noise surrounding the system cause beam-position fluctuations in the range of several nanometers, highly unfavourable for nanotechnological works on FIB. The noise is generated mainly by various parts of the system itself. A method was also developed to identify whether the observed beam-position fluctuations originate from acoustic noise or from electromagnetic interference. It was possible because electromagnetic field impacts charged particles along their entire path while the acoustic vibrations act only on the mechanic elements of the system. Therefore the electromagnetic fluctuations are

  5. Observations of low-aberration plasma lens focusing of relativistic electron beams at the underdense threshold

    International Nuclear Information System (INIS)

    Focusing of a 15 MeV electron bunch by a plasma lens operated at the threshold of the underdense regime has been demonstrated. The strong, 1.7 cm focal length, plasma lens focused both transverse directions simultaneously and reduced the minimum area of the beam spot by a factor of 23. It is shown through analytic analysis and simulation that the observed spherical aberration of this underdense lens, when expressed as the fractional departure of the focusing strength from its linear expectation, is ΔK/K=0.08±0.04. This is significantly lower than the minimum theoretical value for the spherical aberration of an overdense plasma lens. Parameter scans showing the dependence of focusing performance on beam charge, as well as time resolved measurements of the focused electron bunch, are reported.

  6. Focused ion beam techniques for fabricating geometrically-complex components and devices.

    Energy Technology Data Exchange (ETDEWEB)

    Mayer, Thomas Michael; Adams, David Price; Hodges, V. Carter; Vasile, Michael J.

    2004-03-01

    We have researched several new focused ion beam (FIB) micro-fabrication techniques that offer control of feature shape and the ability to accurately define features onto nonplanar substrates. These FIB-based processes are considered useful for prototyping, reverse engineering, and small-lot manufacturing. Ion beam-based techniques have been developed for defining features in miniature, nonplanar substrates. We demonstrate helices in cylindrical substrates having diameters from 100 {micro}m to 3 mm. Ion beam lathe processes sputter-define 10-{micro}m wide features in cylindrical substrates and tubes. For larger substrates, we combine focused ion beam milling with ultra-precision lathe turning techniques to accurately define 25-100 {micro}m features over many meters of path length. In several cases, we combine the feature defining capability of focused ion beam bombardment with additive techniques such as evaporation, sputter deposition and electroplating in order to build geometrically-complex, functionally-simple devices. Damascene methods that fabricate bound, metal microcoils have been developed for cylindrical substrates. Effects of focused ion milling on surface morphology are also highlighted in a study of ion-milled diamond.

  7. Design of titania nanotube structures by focused laser beam direct writing

    Energy Technology Data Exchange (ETDEWEB)

    Enachi, Mihai [National Center for Materials Study and Testing, Technical University of Moldova, Stefan cel Mare av. 168, Chisinau, MD-2004 (Moldova, Republic of); Stevens-Kalceff, Marion A. [School of Physics, University of New South Wales, Sydney, New South Wales 2052 (Australia); Sarua, Andrei [H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Ursaki, Veaceslav [Institute of Applied Physics, Academy of Sciences of Moldova, Chisinau, MD-2028 (Moldova, Republic of); Tiginyanu, Ion, E-mail: tiginyanu@asm.md [National Center for Materials Study and Testing, Technical University of Moldova, Stefan cel Mare av. 168, Chisinau, MD-2004 (Moldova, Republic of); Institute of Electronic Engineering and Nanotechnologies, Academy of Sciences of Moldova, Chisinau, MD-2028 (Moldova, Republic of)

    2013-12-21

    In this work, we report on electrochemical fabrication of titania films consisting of nanotubes (NTs) and their treatment by focused laser beam. The results of sample characterization by optical and scanning electron microscopy, cathodoluminescence imaging, and Raman scattering scanning spectroscopy are compared to those inherent to specimens subjected to thermal treatment in a furnace. The obtained data demonstrate possibilities for controlling crystallographic structure of TiO{sub 2} NTs by focused laser beam direct writing. These findings open new prospects for the design and fabrication of spatial architectures based on titania nanotubes.

  8. Focused ion beam post-processing of optical fiber Fabry-Perot cavities for sensing applications.

    Science.gov (United States)

    André, Ricardo M; Pevec, Simon; Becker, Martin; Dellith, Jan; Rothhardt, Manfred; Marques, Manuel B; Donlagic, Denis; Bartelt, Hartmut; Frazão, Orlando

    2014-06-01

    Focused ion beam technology is combined with chemical etching of specifically designed fibers to create Fabry-Perot interferometers. Hydrofluoric acid is used to etch special fibers and create microwires with diameters of 15 μm. These microwires are then milled with a focused ion beam to create two different structures: an indented Fabry-Perot structure and a cantilever Fabry-Perot structure that are characterized in terms of temperature. The cantilever structure is also sensitive to vibrations and is capable of measuring frequencies in the range 1 Hz - 40 kHz.

  9. Beam Focusing by a Non-Uniformly-Spaced Nanoslit Array in a Metallic Film

    Institute of Scientific and Technical Information of China (English)

    JIAO Xiao-Jin; WANG Pei; ZHANG Dou-Guo; LU Yong-Hua; XIE Jian-Ping; MING Hai

    2006-01-01

    @@ A finite difference time domain simulation has been performed to analyse the optical transmission through a non-uniformly-spaced nanoslit array in silver film. The phase change of surface plasmons propagating on the silver film is used to modulate the initial phase of the output beam. The beam deflection and focusing function are designed, and the focal depth of the focusing metallic structure are mainly considered. It is found that the focal depth can be controlled by altering the effective width of this structure, i.e. the number of slits, when the relative spacing is fixed.

  10. Magnetoinduction sensor of beam current with magnetic noise screening

    International Nuclear Information System (INIS)

    A description is given of a magnetoinduction sensor of beam current in a synchrotron, the latter being a booster of the VEhPP-4 electron-positron complex. The sensor operates under conditions of heavy background noise induced by the synchrotron pulsed magnetic fields. The means reducing the noise level in the sensor are considered. The most efficient screen protecting against pulsed fields is one made of conducting materials where the field is reduced at the expense of induced currents passing in a skin-layer. The screen has an azimuthal slit, which results in the beam vortex field penetration to the sensor without reduction. The noise field is reduced due to the conducting walls and deep slit. Application of the means deseribed allowed to measure low (of the order of 100 mcA) synchrotron beam currents

  11. Stimulated Raman Scattering and Nonlinear Focusing of High-Power Laser Beams Propagating in Water

    CERN Document Server

    Hafizi, B; Penano, J R; Gordon, D F; Jones, T G; Helle, M H; Kaganovich, D

    2015-01-01

    The physical processes associated with propagation of a high-power (power > critical power for self-focusing) laser beam in water include nonlinear focusing, stimulated Raman scattering (SRS), optical breakdown and plasma formation. The interplay between nonlinear focusing and SRS is analyzed for cases where a significant portion of the pump power is channeled into the Stokes wave. Propagation simulations and an analytical model demonstrate that the Stokes wave can re-focus the pump wave after the power in the latter falls below the critical power. It is shown that this novel focusing mechanism is distinct from cross-phase focusing. While discussed here in the context of propagation in water, the gain-focusing phenomenon is general to any medium supporting nonlinear focusing and stimulated forward Raman scattering.

  12. Stimulated Raman scattering and nonlinear focusing of high-power laser beams propagating in water.

    Science.gov (United States)

    Hafizi, B; Palastro, J P; Peñano, J R; Gordon, D F; Jones, T G; Helle, M H; Kaganovich, D

    2015-04-01

    The physical processes associated with propagation of a high-power (power > critical power for self-focusing) laser beam in water include nonlinear focusing, stimulated Raman scattering (SRS), optical breakdown, and plasma formation. The interplay between nonlinear focusing and SRS is analyzed for cases where a significant portion of the pump power is channeled into the Stokes wave. Propagation simulations and an analytical model demonstrate that the Stokes wave can re-focus the pump wave after the power in the latter falls below the critical power. It is shown that this novel focusing mechanism is distinct from cross-phase focusing. The phenomenon of gain-focusing discussed here for propagation in water is expected to be of general occurrence applicable to any medium supporting nonlinear focusing and stimulated Raman scattering. PMID:25831383

  13. Pink-beam focusing with a one-dimensional compound refractive lens.

    Science.gov (United States)

    Dufresne, Eric M; Dunford, Robert W; Kanter, Elliot P; Gao, Yuan; Moon, Seoksu; Walko, Donald A; Zhang, Xusheng

    2016-09-01

    The performance of a cooled Be compound refractive lens (CRL) has been tested at the Advanced Photon Source (APS) to enable vertical focusing of the pink beam and permit the X-ray beam to spatially overlap with an 80 µm-high low-density plasma that simulates astrophysical environments. Focusing the fundamental harmonics of an insertion device white beam increases the APS power density; here, a power density as high as 500 W mm(-2) was calculated. A CRL is chromatic so it does not efficiently focus X-rays whose energies are above the fundamental. Only the fundamental of the undulator focuses at the experiment. A two-chopper system reduces the power density on the imaging system and lens by four orders of magnitude, enabling imaging of the focal plane without any X-ray filter. A method to measure such high power density as well as the performance of the lens in focusing the pink beam is reported. PMID:27577759

  14. Peakon profiles and collapse-bounce cycles in self-focusing spatial beams.

    Science.gov (United States)

    Sun, Can; Barsi, Christopher; Fleischer, Jason W

    2008-12-01

    We study the over-focusing of spatial light beams due to self-focusing nonlinearity, in both local and nonlocal nonlinear media. Numerical simulation of both cases reveals a peaked profile, with a near-cusp at the center surrounded by exponentially-decaying tails, at a critical self-focusing power. The profile is a local effect, occurring as diffraction counteracts nonlinearity. Nonlocality, however, is needed to prevent modulation instability of the initial beam and to prevent catastrophic collapse in 2D. The peaked profile remains for weak nonlocality but disappears for wide nonlocal responses. Beyond the critical power for a peaked solution, or for longer propagation distances, competition between nonlinearity and diffraction causes oscillatory collapse-bounce behavior. The numerical results are confirmed by observing these dynamics in a self-focusing glass with a nonlocal, thermal response.

  15. Experimental research on the longitudinal field generated by a tightly focused beam

    Institute of Scientific and Technical Information of China (English)

    Zhang Ming-Qian; Wang Jia; Tian Qian

    2013-01-01

    The longitudinal optical field is a peculiar physical phenomenon that is always involved with the domain of near-field optics.Due to its extraordinary properties,it has recently attracted increasing attention in research and application.In this1 work,the longitudinal fields generated by the evanescent illumination of tightly focused,different polarized hollow beams are investigated.The focused light fields are numerically simulated according to vector diffraction theory,and their vector analysis is also carried out.The longitudinal fields on the focal plane are demonstrated experimentally using tip-enhanced scanning near-field microscopy.The simulation and experimental results show that the tightly focused radially polarized beam is suited to generating a stronger and purer longitudinal optical field at the focus.

  16. Development of Focused Ion Beam technique for high speed steel 3D-SEM artefact fabrication

    DEFF Research Database (Denmark)

    Carli, Lorenzo; MacDonald, A. Nicole; De Chiffre, Leonardo;

    2009-01-01

    The work describes preliminary manufacture by grinding, followed by machining on a Focused Ion Beam (FIB), of a high speed steel step artefact for 3D-SEM calibration. The FIB is coupled with a SEM in the so called dual beam instrument. The milling capabilities of FIB were checked from a qualitative...... point of view, using the dual beam SEM imaging, and quantitatively using a reference stylus instrument, to establish traceability. A triangular section having a depth of about 10 μm was machined, where the 50 μm curvature radius due to grinding was reduced to about 2 μm by FIB milling...... as it was estimated using the dual beam SEM....

  17. Processes in a dense long-pulse electron beam focused on a solid target

    International Nuclear Information System (INIS)

    The results obtained in beam-target experiments with dense medium-energy electron beam in the regime of long single pulses are presented. The measured power density of the focused beam at the target reached 20 MW/cm2 in these experiments. The processes caused by dense flows of secondary particles and by a dense target ablation plasma were studied in detail. Substantial target shielding occurs when the energy density at the target exceeds the value of about 1 kJ/cm2. The target plasma and the sputtered matter that is responsible for shielding affects also the beam structure, as well as the target etching rates. (J.U.). 3 figs., 5 refs

  18. Model of an LHC superconducting quadrupole magnet

    CERN Multimedia

    Laurent Guiraud

    2000-01-01

    Model of a superconducting quadrupole magnet for the LHC project. These magnets are used to focus the beam by squeezing it into a smaller cross-section, a similar effect to a lens focusing light. However, each magnet only focuses the beam in one direction so alternating magnet arrangements are required to produce a fully focused beam.

  19. Tight focusing of partially polarized vortex beams by binary phase Fresnel zone plates

    Institute of Scientific and Technical Information of China (English)

    Shu Jian-Hua; Chen Zi-Yang; Pu Ji-Xiong; Liu Yong-Xin

    2011-01-01

    Based on vectorial Debye theory,the focusing properties of partially polarized vortex beam by high numerical aperture Fresnel zone plate are investigated.The effects of the numerical apertures of and the phase difference of binary phase Fresnel zone plates,the topological charge of vortex beam and the degree of polarization of incident beam on the intensity distribution and degree of coherence in the focal plane are investigated in detail.It is shown that elliptical light spots and the fiat top beam can be obtained by selecting certain parameters.Studies of degree of coherence reveal that the degree of coherence between x and y components of the electric field,which is zero in the source plane,is improved in the focal plane for vortex beam,but it is hardly changed for the nonvortex beam.It is also proved that any two of the three electric field components Ex,Ey and Ez are completely coherent everywhere in the focal region if the incident light beam is linearly polarized.

  20. Developments in magnet modeling and beam optics for the ARIS separator at FRIB

    Science.gov (United States)

    Portillo, M.; Hausmann, M.; Chouhan, S.

    2016-06-01

    A description is given on the methods used for field analysis of magnets and the extracted parameters used for accurate beam simulations of the fragment separator. For the strong focusing magnets, Fourier decomposition is used in order to extract induced fields associated with higher order multipoles. For dipoles, a 2D field map model is used instead in order to emulate complex field distributions. The theory of the models and the techniques chosen are described, along with results from Monte Carlo beam simulations up to 5th order. The n = 6 multipole induced by the quadrupole is the most significant component. The effects on separator performance with and without this component in the model are demonstrated.

  1. Motion-free hybrid design laser beam propagation analyzer using a digital micromirror device and a variable focus liquid lens.

    Science.gov (United States)

    Sheikh, Mumtaz; Riza, Nabeel A

    2010-06-01

    To the best of our knowledge, we propose the first motion-free laser beam propagation analyzer with a hybrid design using a digital micromirror device (DMD) and a liquid electronically controlled variable focus lens (ECVFL). Unlike prior analyzers that require profiling the beam at multiple locations along the light propagation axis, the proposed analyzer profiles the beam at the same plane for multiple values of the ECVFL focal length, thus eliminating beam profiler assembly motion. In addition to measuring standard Gaussian beam parameters, the analyzer can also be used to measure the M(2) beam propagation parameter of a multimode beam. Proof-of-concept beam parameter measurements with the proposed analyzer are successfully conducted for a 633 nm laser beam. Given the all-digital nature of the DMD-based profiling and all-analog motion-free nature of the ECVFL beam focus control, the proposed analyzer versus prior art promises better repeatability, speed, and reliability.

  2. Small-Scale Self-Focusing of Intense Laser Beams In the Presence of Vector Effect

    Institute of Scientific and Technical Information of China (English)

    WEN Shuang-Chun; FAN Dian-Yuan

    2000-01-01

    We extend Bespalov-Talanov (B-T) theory on small-scale self-focusing (SSSF) to include vector effect of a very narrow intense laser beam with application of the vector self-focusing model. The gain spectrum for perturbations is obtained by using the standard linear instability analysis. It is shown that the influence on SSSF of vector effect is closely related to the beam width. For a very narrow beam, the role played by vector effect becomes significant, it reduces the fastest growing frequency and the maximum growth rate, and shortens the frequency range for perturbation growing, and thus deviates the gain spectrum from that of B-T theory.

  3. Interaction of highly focused vector beams with a metal knife-edge

    CERN Document Server

    Quabis, S

    2011-01-01

    We investigate the interaction of highly focused linearly polarized optical beams with a metal knife-edge both theoretically and experimentally. A high numerical aperture objective focusses beams of various wavelengths onto samples of different sub-wavelength thicknesses made of several opaque and pure materials. The standard evaluation of the experimental data shows material and sample dependent spatial shifts of the reconstructed intensity distribution, where the orientation of the electric field with respect to the edge plays an important role. A deeper understanding of the interaction between the knife-edge and the incoming highly focused beam is obtained by extending previous studies on diffraction through a finite slit and incorporating plasmonic modes into the theoretical model.We achieve good qualitative agreement of our numerical simulations with the experimental findings.

  4. Focusing a beam beyond the diffraction limit using a hyperlens-based device

    Institute of Scientific and Technical Information of China (English)

    Zheng Guo-Xing; Zhang Rui-Ying; Li Song; He Ping-An; Zhou Hui

    2011-01-01

    A super-focusing device composed of a focusing objective and a hyperlens is proposed to focus an incident plane wave into the deep subwavelength dimension. In the device,the objective converts the incident plane wave into a convergent one.The half cylindrical hyperlens can support high wave vector k modes propagating towards its core.So the convergent wave can be focused into an ultrasmall spot beyond the diffraction limit.The layout is proposed for the super-focusing device and its characteristics are investigated theoretically.Numerical simulations verify that the focused beams are confined in a spot with a diameter of 16.3 nm in the focal plane of the focusing objective with a numerical aperture of 0.6,which corresponds to a super-resolution spot of λ0/23 (λ0 is the wavelength in vacuum).The simulations confirm the effectiveness of the proposed device.

  5. Lecture-Room Interference Demo Using a Glass Plate and a Laser Beam Focused on It

    Science.gov (United States)

    Ageev, Leonid A.; Yegorenkov, Vladimir D.

    2010-01-01

    We describe a simple case of non-localized interference produced with a glass plate and a laser beam focused on it. The proposed setup for observing interference is compact when semiconductor lasers are employed, and it is well suited for demonstration and comparison of interference in reflected and transmitted light in a large lecture-room. This…

  6. Dynamics of cavitation clouds within a high-intensity focused ultrasonic beam

    NARCIS (Netherlands)

    Lu, Yuan; Katz, Joseph; Prosperetti, Andrea

    2013-01-01

    In this experimental study, we generate a 500 kHz high-intensity focused ultrasonic beam, with pressure amplitude in the focal zone of up to 1.9 MPa, in initially quiescent water. The resulting pressure field and behavior of the cavitation bubbles are measured using high-speed digital in-line hologr

  7. Focused ion beam nano-structuring of $Al_2O_3$ dielectric layers for photonic applications

    NARCIS (Netherlands)

    Ay, Feridun; Bradley, Jonathan D.B.; Hopman, Wico C.L.; Gadgil, Vishwas J.; Ridder, de René M.; Wörhoff, Kerstin; Pollnau, Markus

    2007-01-01

    In order to enable full integration of active integrated optical components based on Si-technology, high quality micro- and nano-structuring processes aiming at the development of on-chip resonator structures are to be achieved. By optimizing focused ion beam milling parameters such as ion current,

  8. Focused ion beam nano-structuring of photonic Bragg gratings in $Al_2O_3$ waveguides

    NARCIS (Netherlands)

    Uranga, Amaia; Ay, Feridun; Bradley, Jonathan D.B.; Ridder, de René M.; Wörhoff, Kerstin; Pollnau, Markus; Emplit, Ph.; Delqué, M.; Gorza, S.-P.; Kockaart, P.; Leijtens, X.

    2007-01-01

    Focused ion beam (FIB) etching is receiving increasing attention for the fabrication of active integrated optical components such as waveguide amplifiers and lasers. Si-technology compatible low-loss $Al_2O_3$ channel waveguides grown on thermally oxidized silicon substrates have been reported recen

  9. Focused ion beam nano-structuring of Bragg gratings in $Al_2O_3$ channel waveguides

    NARCIS (Netherlands)

    Ay, Feridun; Uranga, Amaia; Bradley, Jonathan D.B.; Wörhoff, Kerstin; Ridder, de René M.; Pollnau, Markus; Ridder, de R.M.; Ay, F.; Kauppinen, L.J.

    2008-01-01

    We report our recent results on an optimization study of focused ion beam (FIB) nano-structuring of Bragg gratings in $Al_2O_3$ channel waveguides. By optimizing FIB milling parameters such as ion current, dwell time, loop repetitions, scanning strategy, and applying a top metal layer for reducing c

  10. Portable test bench for the studies concerning ion sources and ion beam extraction and focusing systems

    International Nuclear Information System (INIS)

    A portable test bench is described, which was designed to check ion sources, ion beam extraction and focusing systems before its use in a 600 KeV Cockcroft-Walton accelerator. The vacuum possibilities of the system are specially analyzed in connection with its particular use. The whole can be considered as a portable accelerator of low energy (50 keV). (Author)

  11. High-resolution direct-write patterning using focused ion beams

    NARCIS (Netherlands)

    Ocola, L.E.; Rue, C.; Maas, D.J.

    2014-01-01

    Over the last few years, significant improvements in sources, columns, detectors, control software, and accessories have enabled a wealth of new focused ion beam applications. In addition, modeling has provided many insights into ion-sample interactions and the resultant effects on the sample. With

  12. Focused Ion Beam - Scanning Electron Microscopy Applied to Electrically Insulating Materials

    NARCIS (Netherlands)

    de Winter, D.A.M.

    2015-01-01

    The Focused Ion Beam – Scanning Electron Microscope (FIB-SEM) is a versatile instrument originating from the semiconductor industry. The FIB is used to produce cross sections of pre-defined locations of interest, which are imaged and analyzed with the SEM. Repeated FIB cross sectioning and subsequen

  13. Patterning of Spiral Structure on Optical Fiber by Focused-Ion-Beam Etching

    Science.gov (United States)

    Mekaru, Harutaka; Yano, Takayuki

    2012-06-01

    We produce patterns on minute and curved surfaces of optical fibers, and develop a processing technology for fabricating sensors, antennas, electrical circuits, and other devices on such patterned surfaces by metallization. A three-dimensional processing technology can be used to fabricate a spiral coil on the surface of cylindrical quartz materials, and then the microcoils can also be applied to capillaries of micro-fluid devices, as well as to receiver coils connected to a catheter and an endoscope of nuclear magnetic resonance imaging (MRI) systems used in imaging blood vessels. To create a spiral line pattern with a small linewidth on a full-circumference surface of an optical fiber, focused-ion-beam (FIB) etching was employed. Here, a simple rotation stage comprising a dc motor and an LR3 battery was built. However, during the development of a prototype rotation stage before finalizing a large-scale remodelling of our FIB etching system, a technical problem was encountered where a spiral line could not be processed without running into breaks and notches in the features. It turned out that the problem was caused by axis blur resulting from an eccentric spinning (or wobbling) of the axis of the fiber caused by its unrestrained free end. The problem was solved by installing a rotation guide and an axis suppression device onto the rotation stage. Using this improved rotation stage. we succeeded in the seamless patterning of 1-µm-wide features on the full-circumference surface of a 250-µm-diameter quartz optical fiber (QOF) by FIB etching.

  14. Main magnetic focus ion source: Basic principles, theoretical predictions and experimental confirmations

    Science.gov (United States)

    Ovsyannikov, V. P.; Nefiodov, A. V.

    2016-03-01

    It is proposed to produce highly charged ions in the local potential traps formed by the rippled electron beam in a focusing magnetic field. In this method, extremely high electron current densities can be attained on short length of the ion trap. The design of very compact ion sources of the new generation is presented. The computer simulations predict that for such ions as, for example, Ne8+ and Xe44+, the intensities of about 109 and 106 ions per second, respectively, can be obtained. The experiments with pilot example of the ion source confirm efficiency of the suggested method. The X-ray emission from Ir59+, Xe44+ and Ar16+ ions was detected. The control over depth of the local ion trap is shown to be feasible.

  15. A numerical study of transcranial focused ultrasound beam propagation at low frequency

    International Nuclear Information System (INIS)

    The feasibility of transcranial ultrasound focusing with a non-moving phased array and without skull-specific aberration correction was investigated using computer simulations. Three cadaver skull CT image data sets were incorporated into an acoustic wave transmission model to simulate transskull ultrasound wave propagation. Using a 0.25 MHz hemispherical array (125 mm radius of curvature, 250 mm diameter, 24 255 elements), the simulated beams could be focused and steered with transducer element driving phases and amplitude adjusted for focal beam steering in water (water-path). A total of 82 foci, spanning wide ranges of distance in the three orthogonal dimensions, were simulated to test the focal beam steering capability inside the three skulls. The acoustic pressure distribution in a volume of 20 x 20 x 20 mm3 centred at each focus was calculated with a 0.5 mm spacing in each axis. Clearly defined foci were retained through the skulls (skull-path) in most cases. The skull-path foci were on average 1.6 ± 0.8 mm shifted from their intended locations. The -3 dB skull-path beam width and length were on average 4.3 ± 1.0 mm and 7.7 ± 1.8 mm, respectively. The skull-path sidelobe levels ranged from 25% to 55% of the peak pressure values. The skull-path peak pressure levels were about 10%-40% of their water-path counterparts. Focusing low-frequency beam through skull without skull-specific aberration correction is possible. This method may be useful for applying ultrasound to disrupt the blood-brain barrier for targeted delivery of therapeutic or diagnostic agents, or to induce microbubbles, or for other uses of ultrasound in brain where the required power levels are low and the sharp focusing is not needed

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

    Indian Academy of Sciences (India)

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

    2015-12-01

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

  17. Controlled fabrication of nanopores using a direct focused ion beam approach with back face particle detection

    Science.gov (United States)

    Patterson, N.; Adams, D. P.; Hodges, V. C.; Vasile, M. J.; Michael, J. R.; Kotula, P. G.

    2008-06-01

    We report a direct, ion drilling technique that enables the reproducible fabrication and placement of nanopores in membranes of different thickness. Using a 30 keV focused Ga ion beam column combined with an in situ, back face, multi-channelplate particle detector, nanopores are sputtered in Si3N4 and W/Si3N4 to have diameters as small as 12 nm. Transmission electron microscopy shows that focused ion beam-drilled holes are near-conical with the diameter decreasing from entry to exit side. By monitoring the detector signal during ion exposure, the drilled hole width can be minimized such that the exit-side diameter is smaller than the full width at half-maximum of the nominally Gaussian-shaped incident beam. Judicious choice of the beam defining aperture combined with back face particle detection allows for reproducible exit-side hole diameters between 18 and 100 nm. The nanopore direct drilling technique does not require potentially damaging broad area exposure to tailor hole sizes. Moreover, this technique successfully achieves breakthrough despite the effects of varying membrane thickness, redeposition, polycrystalline grain structure, and slight ion beam current fluctuations.

  18. Controlled fabrication of nanopores using a direct focused ion beam approach with back face particle detection

    International Nuclear Information System (INIS)

    We report a direct, ion drilling technique that enables the reproducible fabrication and placement of nanopores in membranes of different thickness. Using a 30 keV focused Ga ion beam column combined with an in situ, back face, multi-channelplate particle detector, nanopores are sputtered in Si3N4 and W/Si3N4 to have diameters as small as 12 nm. Transmission electron microscopy shows that focused ion beam-drilled holes are near-conical with the diameter decreasing from entry to exit side. By monitoring the detector signal during ion exposure, the drilled hole width can be minimized such that the exit-side diameter is smaller than the full width at half-maximum of the nominally Gaussian-shaped incident beam. Judicious choice of the beam defining aperture combined with back face particle detection allows for reproducible exit-side hole diameters between 18 and 100 nm. The nanopore direct drilling technique does not require potentially damaging broad area exposure to tailor hole sizes. Moreover, this technique successfully achieves breakthrough despite the effects of varying membrane thickness, redeposition, polycrystalline grain structure, and slight ion beam current fluctuations

  19. Isentropic focusing of supersonic plasma jets for magnetized target fusion

    International Nuclear Information System (INIS)

    It is shown that high energy flux densities can be reached by the isentropic Prandtl-Meyer compression flow of a supersonic plasma jet in a convergent nozzle. The energy flux density thereby increases in proportion to M2/(γ-1) where M is the Mach number of the jet and γ the specific heat ratio. With an axial magnetic field set up inside the nozzle by the thermomagnetic Nernst effect, the jet is magnetically insulated from the nozzle wall, reducing the bremsstrahlung radiation and conveniently magnetizing the target plasma. A sufficiently large number of spherically arranged nozzles can then be used for the ignition and confinement of a magnetized thermonuclear target

  20. Ion beam enhancement in magnetically insulated ion diodes for high-intensity pulsed ion beam generation in non-relativistic mode

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, X. P. [Key Laboratory of Materials Modification by Laser, Ion, and Electron Beams, Ministry of Education, Dalian University of Technology, Dalian 116024 (China); Surface Engineering Laboratory, School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China); Zhang, Z. C.; Lei, M. K., E-mail: surfeng@dlut.edu.cn [Surface Engineering Laboratory, School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China); Pushkarev, A. I. [Surface Engineering Laboratory, School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China); Laboratory of Beam and Plasma Technology, High Technologies Physics Institute, Tomsk Polytechnic University, 30, Lenin Ave, 634050 Tomsk (Russian Federation)

    2016-01-15

    High-intensity pulsed ion beam (HIPIB) with ion current density above Child-Langmuir limit is achieved by extracting ion beam from anode plasma of ion diodes with suppressing electron flow under magnetic field insulation. It was theoretically estimated that with increasing the magnetic field, a maximal value of ion current density may reach nearly 3 times that of Child-Langmuir limit in a non-relativistic mode and close to 6 times in a highly relativistic mode. In this study, the behavior of ion beam enhancement by magnetic insulation is systematically investigated in three types of magnetically insulated ion diodes (MIDs) with passive anode, taking into account the anode plasma generation process on the anode surface. A maximal enhancement factor higher than 6 over the Child-Langmuir limit can be obtained in the non-relativistic mode with accelerating voltage of 200–300 kV. The MIDs differ in two anode plasma formation mechanisms, i.e., surface flashover of a dielectric coating on the anode and explosive emission of electrons from the anode, as well as in two insulation modes of external-magnetic field and self-magnetic field with either non-closed or closed drift of electrons in the anode-cathode (A-K) gap, respectively. Combined with ion current density measurement, energy density characterization is employed to resolve the spatial distribution of energy density before focusing for exploring the ion beam generation process. Consistent results are obtained on three types of MIDs concerning control of neutralizing electron flows for the space charge of ions where the high ion beam enhancement is determined by effective electron neutralization in the A-K gap, while the HIPIB composition of different ion species downstream from the diode may be considerably affected by the ion beam neutralization during propagation.

  1. Ion beam enhancement in magnetically insulated ion diodes for high-intensity pulsed ion beam generation in non-relativistic mode

    International Nuclear Information System (INIS)

    High-intensity pulsed ion beam (HIPIB) with ion current density above Child-Langmuir limit is achieved by extracting ion beam from anode plasma of ion diodes with suppressing electron flow under magnetic field insulation. It was theoretically estimated that with increasing the magnetic field, a maximal value of ion current density may reach nearly 3 times that of Child-Langmuir limit in a non-relativistic mode and close to 6 times in a highly relativistic mode. In this study, the behavior of ion beam enhancement by magnetic insulation is systematically investigated in three types of magnetically insulated ion diodes (MIDs) with passive anode, taking into account the anode plasma generation process on the anode surface. A maximal enhancement factor higher than 6 over the Child-Langmuir limit can be obtained in the non-relativistic mode with accelerating voltage of 200–300 kV. The MIDs differ in two anode plasma formation mechanisms, i.e., surface flashover of a dielectric coating on the anode and explosive emission of electrons from the anode, as well as in two insulation modes of external-magnetic field and self-magnetic field with either non-closed or closed drift of electrons in the anode-cathode (A-K) gap, respectively. Combined with ion current density measurement, energy density characterization is employed to resolve the spatial distribution of energy density before focusing for exploring the ion beam generation process. Consistent results are obtained on three types of MIDs concerning control of neutralizing electron flows for the space charge of ions where the high ion beam enhancement is determined by effective electron neutralization in the A-K gap, while the HIPIB composition of different ion species downstream from the diode may be considerably affected by the ion beam neutralization during propagation

  2. Generation and focusing of electron beams with initial transverse-longitudinal correlation

    Energy Technology Data Exchange (ETDEWEB)

    Harris, J. R., E-mail: john.harris@colostate.edu [Department of Electrical and Computer Engineering, Colorado State University, Fort Collins, Colorado 80523 (United States); Lewellen, J. W. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Poole, B. R. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

    2014-10-07

    In charged particle beams, one of the roles played by space charge is to couple the transverse and longitudinal dynamics of the beam. This can lead to very complex phenomena which are generally studied using computer simulations. However, in some cases models based on phenomenological or analytic approximations can provide valuable insight into the system behavior. In this paper, we employ such approximations to investigate the conditions under which all the slices of a space charge dominated electron beam with slowly varying current could be focused to a waist with the same radius and at the same location, independent of slice current, and show that this can be accomplished approximately if the initial transverse-longitudinal correlation introduced onto the beam by the electron gun is chosen to compensate for the transverse-longitudinal correlation introduced onto the beam in the drift section. The validity of our approximations is assessed by use of progressively more realistic calculations. We also consider several design elements of electron guns that affect the initial correlations in the beams they generate.

  3. An angled nano-tunnel fabricated on poly(methyl methacrylate) by a focused ion beam

    Science.gov (United States)

    Her, Eun Kyu; Chung, Hee-Suk; Moon, Myoung-Woon; Oh, Kyu Hwan

    2009-07-01

    Angled nano-scale tunnels with high aspect ratio were fabricated on poly(methyl methacrylate) (PMMA) using a focused ion beam (FIB). The fabrication parameters such as ion fluence, incidence angle, and acceleration voltage of the Ga+ ion beam were first studied on the PMMA surface to explore the formation of the nano-scale configurations such as nano-holes and cones with diameter in the range of 50-150 nm at an ion beam acceleration voltage of 5-20 kV. It was also found that the PMMA surface exposed to FIB was changed into an amorphous graphitic structure. Angled nano-scale tunnels were fabricated with high aspect ratio of 700-1500 nm in depth and 60 nm in mean diameter at an ion beam acceleration voltage of 5 kV and under a specific ion beam current. The angle of the nano-tunnels was found to follow the incident angle of the ion beam tilted from 0° to 85°, which has the potential for creating a mold for anisotropic adhesives by mimicking the hairs on a gecko's feet.

  4. Precise milling of nano-gap chains in graphene with a focused helium ion beam

    Science.gov (United States)

    Zhou, Yangbo; Maguire, Pierce; Jadwiszczak, Jakub; Muruganathan, Manoharan; Mizuta, Hiroshi; Zhang, Hongzhou

    2016-08-01

    A focused helium ion beam was used to introduce nano-sized gap chains in graphene. The effect of beam scanning strategies in the fabrication of the nano-gap chains was investigated. The tuning of graphene conductivity has been achieved by modulating the magnitude and uniformity of the ion dose and hence the morphology of the nano-gap chains. A model based on the site-specific and dose-dependent conductivity was built to understand the tuning of the conductivity, taking into account the nanoscale non-uniformity of irradiation.

  5. Precise milling of nano-gap chains in graphene with a focused helium ion beam.

    Science.gov (United States)

    Zhou, Yangbo; Maguire, Pierce; Jadwiszczak, Jakub; Muruganathan, Manoharan; Mizuta, Hiroshi; Zhang, Hongzhou

    2016-08-12

    A focused helium ion beam was used to introduce nano-sized gap chains in graphene. The effect of beam scanning strategies in the fabrication of the nano-gap chains was investigated. The tuning of graphene conductivity has been achieved by modulating the magnitude and uniformity of the ion dose and hence the morphology of the nano-gap chains. A model based on the site-specific and dose-dependent conductivity was built to understand the tuning of the conductivity, taking into account the nanoscale non-uniformity of irradiation. PMID:27347752

  6. Hexapole State-Selection and Beam Focus of Polar Top Molecules

    Institute of Scientific and Technical Information of China (English)

    LIU Fu-Chun; JIN Ming-Xing; GAO Xin; DING Da-Jun

    2006-01-01

    @@ We express a description of the state-selection role for a polar molecule in a hexapole electrostatic field. By a quantum mechanical treatment of the molecular Stark energy and a classical mechanical treatment for the molecular trajectory in the field, we present the calculated results of the different molecular rotational state selection and beam focus and discuss the influence of the high order Stark effect, the beam speed on the results for the symmetric top molecule CH3CN, CH3I, and the asymmetric top molecule CH2F2 in the hexapole field.

  7. The effects of magnetic fringe fields on beam dynamics in a beam transport line of a terahertz FEL source

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Han [State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan 430074, Hubei (China); Xiong, Yongqian, E-mail: yqxiong@mail.hust.edu.cn [State Key Laboratory of Advanced Electromagnetic Engineering and Technology, Huazhong University of Science and Technology, Wuhan 430074, Hubei (China); Pei, Yuanji [National Synchrotron Radiation laboratory, University of Science and Technology of China, Hefei 230029, Anhui (China)

    2014-11-11

    The transport line used in a terahertz FEL device has to transport electron beam through the entire system efficiently and meet the requirements of the beam parameters at the undulator entrance. Due to space limitations, the size of the magnets (five quadrupoles and two bending magnets) employed in the transport line was limited, and some devices were densely packed. In this paper, analyses of the effect of fringe fields and magnetic interference of magnets are presented. 3D models of these magnets are built and their linear optical properties are compared with those obtained by hard edge models. The results indicated that the effects of these factors are significant and they would cause a mismatch of the beam at the exit of the transport line under the preliminary lattice design. To solve this problem, the beam was re-matched using the particle swarm optimization algorithm.

  8. Niobium nano-SQUIDs based on sub-micron tunnel junction fabricated by three-dimensional Focused Ion Beam sculpting

    Science.gov (United States)

    Fretto, M.; Enrico, E.; De Leo, N.; Boarino, L.; Lacquaniti, V.; Granata, C.; Russo, R.; Vettoliere, A.

    2014-05-01

    A three dimensional nano-SQUID (Superconducting Quantum Interference Device) has been realized in a vertical configuration (with the loop in the same plane of Josephson Tunneling Junctions, JTJs). The loop area is 0.25 μm2 corresponding to a modulation period of about 5 mT, the square JTJs have a side length of 0.3 μm. Josephson junction's fabrication is carried out combining optical lithography to pattern trilayer and three dimensional (3D) Focused Ion Beam (FIB) sculpting technique to define the junctions' and the loop's areas. Two different ion etching processes were performed, perpendicular and parallel to the multilayer, resulting in a precise 3D structure. Finally, a standard anodization was performed to eliminate the unstructured surface material generated by the high energetic ion beam assuring high quality junctions. Electric transport characteristics of the nanodevice measured at T = 4.2 K are reported, in particular the current-voltage characteristics and critical current vs external magnetic field. The high modulation depth of the critical current (up to 70% of the Ic at zero magnetic flux) and the device reliability are very encouraging in view of nanoscience applications.

  9. Atomic-Beam Magnetic Resonance Experiments at ISOLDE

    CERN Multimedia

    2002-01-01

    The aim of the atomic-beam magnetic resonance (ABMR) experiments at ISOLDE is to map the nuclear behaviour in wide regions of the nuclear chart by measuring nuclear spins and moments of ground and isomeric states. This is made through an investigation of the atomic hyperfine structure of free, neutral atoms in a thermal atomic-beam using radio-frequency techniques. On-line operation allows the study of short-lived nuclei far from the region of beta-stability.\\\\ \\\\ The ABMR experiments on the |2S^1 ^2 elements Rb, Cs, Au and Fr have been completed, and present efforts are directed towards the elements with an open p-shell and on the rare-earth elements.\\\\ \\\\ The experimental data obtained are compared with results from model calculations, giving information on the single-particle structure and on the nuclear shape parameters.

  10. Integration of RFQ beam coolers and solenoidal magnetic fields

    Science.gov (United States)

    Cavenago, M.; Romé, M.; Maggiore, M.; Porcellato, A. M.; Maero, G.; Chiurlotto, F.; Comunian, M.; Galatà, A.; Cavaliere, F.

    2016-02-01

    Electromagnetic traps are a flexible and powerful method of controlling particle beams, possibly of exotic nuclei, with cooling (of energy spread and transverse oscillations) provided by collisions with light gases as in the Radio Frequency Quadrupole Cooler (RFQC). A RFQC prototype can be placed inside the existing Eltrap solenoid, capable of providing a magnetic flux density component Bz up to 0.2 T, where z is the solenoid axis. Confinement in the transverse plane is provided both by Bz and the rf voltage Vrf (up to 1 kV at few MHz). Transport is provided by a static electric field Ez (order of 100 V/m), while gas collisions (say He at 1 Pa, to be maintained by differential pumping) provide cooling or heating depending on Vrf. The beamline design and the major parameters Vrf, Bz (which affect the beam transmission optimization) are here reported, with a brief description of the experimental setup.

  11. Measurement of beam energy of spherical plasma focus diode and its PIC code simulations

    International Nuclear Information System (INIS)

    We have evaluated dynamic characteristics of spherical plasma focus diode (SPFD) by experiments and simulations. Using a calorimeter, there was a peak of 84 J/cm2 on z-axis of an intense, pulsed, light-ion beam energy density. To evaluate the species and energy, Thomson parabola energy spectrometer measurement was carried out. To obtain beam flux, new types of electrodes were used; grooveless high flux anode and highly transparent, webbed cathode. We found that the protonic ratio, defined by the ratio of protons over heavy ions (C+, C++, O+, and O++), is 8.2. The energy of protons, which had a peak at 300 keV, distributed in the range of 230 - 600 keV. In PIC code simulations, we proposed initial thermal energy model to express the local divergence of LIB. We assumed that the initial thermal energy models takes half vector space. The vector had a constant magnitude and random direction. When the initial energy is 20 eV, the ion beam focused in a cylindrical area of 0.4 mmφ x 2.4 mm. This focusing size was much tighter than the experimental results (6.0 mmφ x 4.5 mm) measured by time-integrated backward Rutherford scattering pinhole camera. Above 20 eV, simulation results gave better focusing. The local divergence, however, could not be expressed by the above models. (author)

  12. Acoustical tweezers using single spherically focused piston, X-cut, and Gaussian beams.

    Science.gov (United States)

    Mitri, Farid G

    2015-10-01

    Partial-wave series expansions (PWSEs) satisfying the Helmholtz equation in spherical coordinates are derived for circular spherically focused piston (i.e., apodized by a uniform velocity amplitude normal to its surface), X-cut (i.e., apodized by a velocity amplitude parallel to the axis of wave propagation), and Gaussian (i.e., apodized by a Gaussian distribution of the velocity amplitude) beams. The Rayleigh-Sommerfeld diffraction integral and the addition theorems for the Legendre and spherical wave functions are used to obtain the PWSEs assuming weakly focused beams (with focusing angle α ⩽ 20°) in the Fresnel-Kirchhoff (parabolic) approximation. In contrast with previous analytical models, the derived expressions allow computing the scattering and acoustic radiation force from a sphere of radius a without restriction to either the Rayleigh (a ≪ λ, where λ is the wavelength of the incident radiation) or the ray acoustics (a ≫λ) regimes. The analytical formulations are valid for wavelengths largely exceeding the radius of the focused acoustic radiator, when the viscosity of the surrounding fluid can be neglected, and when the sphere is translated along the axis of wave propagation. Computational results illustrate the analysis with particular emphasis on the sphere's elastic properties and the axial distance to the center of the concave surface, with close connection of the emergence of negative trapping forces. Potential applications are in single-beam acoustical tweezers, acoustic levitation, and particle manipulation. PMID:26470046

  13. Phase-transition oscillations induced by a strongly focused laser beam

    Science.gov (United States)

    Devailly, Clémence; Crauste-Thibierge, Caroline; Petrosyan, Artyom; Ciliberto, Sergio

    2015-11-01

    We report the observation of a surprising phenomenon consisting in a oscillating phase transition which appears in a binary mixture when this is enlightened by a strongly focused infrared laser beam. The mixture is poly-methyl-meth-acrylate (PMMA)-3-octanone, which has an upper critical solution temperature at Tc=306.6 K and volume fraction ϕc=12.8 % [Crauste et al., arXiv:1310.6720, 2013]. We describe the dynamical properties of the oscillations, which are produced by a competition between various effects: the local accumulation of PMMA produced by the laser beam, thermophoresis, and nonlinear diffusion. We show that the main properties of this kind of oscillations can be reproduced in the Landau theory for a binary mixture in which a local driving mechanism, simulating the laser beam, is introduced.

  14. Tentative design of beam focusing for the AHF linac and transport systems

    International Nuclear Information System (INIS)

    Proposals for an advanced hadron facility include building afterburner linacs for LAMPF. A first afterburner, Add-on Linac number 1, is proposed to accelerate the beam from 0.8 to 1.6 GeV. The output beam would then be fed to a compressor ring and to another afterburner, Add-on Linac number 2. We make a rough estimate of the transverse focusing strength needed in these linacs, and consider the transport line from the end of the LAMPF 805-MHz linac to the start of Add-on Linac number 1. A rebuncher is needed in this transport line for proper acceptance of the beam into the add-on linac. 2 refs., 4 figs

  15. Three-dimensional microstructural characterization of bulk plutonium and uranium metals using focused ion beam technique

    Science.gov (United States)

    Chung, Brandon W.; Erler, Robert G.; Teslich, Nick E.

    2016-05-01

    Nuclear forensics requires accurate quantification of discriminating microstructural characteristics of the bulk nuclear material to identify its process history and provenance. Conventional metallographic preparation techniques for bulk plutonium (Pu) and uranium (U) metals are limited to providing information in two-dimension (2D) and do not allow for obtaining depth profile of the material. In this contribution, use of dual-beam focused ion-beam/scanning electron microscopy (FIB-SEM) to investigate the internal microstructure of bulk Pu and U metals is demonstrated. Our results demonstrate that the dual-beam methodology optimally elucidate microstructural features without preparation artifacts, and the three-dimensional (3D) characterization of inner microstructures can reveal salient microstructural features that cannot be observed from conventional metallographic techniques. Examples are shown to demonstrate the benefit of FIB-SEM in improving microstructural characterization of microscopic inclusions, particularly with respect to nuclear forensics.

  16. Beam dynamics in the final focus section of the future linear collider

    CERN Document Server

    AUTHOR|(SzGeCERN)739431; TOMAS, Rogelio

    The exploration of new physics in the ``Tera electron-Volt''~(TeV) scale with precision measurements requires lepton colliders providing high luminosities to obtain enough statistics for the particle interaction analysis. In order to achieve design luminosity values, linear colliders feature nanometer beam spot sizes at the Interaction~Point~(IP).\\par In addition to several effects affecting the luminosity, three main issues to achieve the beam size demagnification in the Final Focus Section (FFS) of the accelerator are the chromaticity correction, the synchrotron radiation effects and the correction of the lattice errors.\\par This thesis considers two important aspects for linear colliders: push the limits of linear colliders design, in particular the chromaticity correction and the radiation effects at 3~TeV, and the instrumentation and experimental work on beam stabilization in a test facility.\\par The current linear collider projects, CLIC~\\cite{CLICdes} and ILC~\\cite{ILCdes}, have lattices designed using...

  17. Ion beam and neutron output from a sub-kilojoule dense plasma focus

    International Nuclear Information System (INIS)

    We are seeking to gain a better fundamental understanding of the ion beam acceleration and neutron production dense plasma focus (DPF) device. Experiments were performed on a kilojoule level, fast rise time DPF located at LLNL. Ion beam spectra and neutron yield were measured for deuterium pinches. Visible light images of the pinch are used to determine the pinch length. In addition, an RF probe was placed just outside the cathode to measure fluctuations in Ez up to 6 GHz, which is within the range of the lower hybrid frequencies. We find these oscillations arise at a characteristic frequency near 4 GHz during the pinch. Comparisons of the neutron yield and ion beam characteristics are presented. The neutron yield is also compared to scaling laws

  18. Beam-Based Alignment, Tuning and Beam Dynamics Studies for the ATF2 Extraction Line and Final Focus System

    International Nuclear Information System (INIS)

    Using a new extraction line currently under construction, the ATF2 experiment plans to test the novel compact final focus optics design with local chromaticity correction intended for use in future linear colliders. With a 1.3 GeV design beam of 30nm normalized vertical emittance extracted from the ATF damping ring, the primary goal is to achieve a vertical spot-size at the IP waist of 37nm. We discuss our planned strategy for tuning the ATF2 beam to meet the primary goal. Simulation studies have been performed to asses the effectiveness of the strategy, including 'static' (installation) errors and dynamical effects (ground-motion, mechanical vibration, ring extraction jitter etc.). We have simulated all steps in the tuning procedure, from initial orbit establishment to final IP spot-size tuning. Through a Monte Carlo study of 100's of simulation seeds we find we can achieve a spot-size within ∼10% of the design optics value in at least 75% of cases. We also ran a simulation to study the long-term performance with the use of beam-based feedbacks

  19. Low-field permanent magnet quadrupoles in a new relativistic-klystron two-beam accelerator design

    Energy Technology Data Exchange (ETDEWEB)

    Yu, S.; Sessler, A. [Lawrence Berkeley Lab., CA (United States)

    1995-02-01

    Permanent magnets play a central role in the new relativistic klystron two-beam-accelerator design. The two key goals of this new design, low cost and the suppression of beam break-up instability are both intimately tied to the permanent magnet quadrupole focusing system. A recently completed systems study by a joint LBL-LLNL team concludes that a power source for a 1 TeV center-of-mass Next Linear Collider based on the new TBA design can be as low as $1 billion, and the efficiency (wall plug to rf) is estimated to be 36%. End-to-end simulations of longitudinal and transverse beam dynamics show that the drive beam is stable over the entire TBA unit.

  20. Correlation of Beam Transport Characteristics and Mass Resolving Power to Analyzing Magnet Pole Piece Wear in Axcelis HE Ion Implanters

    Science.gov (United States)

    Johnson, Ron; Schuur, John; Tysinger, Randy

    2008-11-01

    An investigation into odd analyzing magnet tuning behavior on an Axcelis HE ion implanter revealed a correlation to excessive wear on the analyzer magnet pole pieces. Though the lifetime is generally quite good, the pole pieces are internal to the beamline design and are exposed to and sputtered by the ion beam during mass analysis. This erosion of the pole piece surfaces affects beam focus and transport, especially for lower current ion beams. Eventually, automatic beam set-up fails altogether as the system is unable to locate the correct amu peak. It is important to understand and correct any deficiencies in pole piece condition as long-term neglect will eventually lead to process errors. Data is presented to illustrate good and bad pole piece condition and a method is suggested for non-invasive testing.

  1. Superposition of nonparaxial vectorial complex-source spherically focused beams: Axial Poynting singularity and reverse propagation

    Science.gov (United States)

    Mitri, F. G.

    2016-08-01

    In this work, counterintuitive effects such as the generation of an axial (i.e., long the direction of wave motion) zero-energy flux density (i.e., axial Poynting singularity) and reverse (i.e., negative) propagation of nonparaxial quasi-Gaussian electromagnetic (EM) beams are examined. Generalized analytical expressions for the EM field's components of a coherent superposition of two high-order quasi-Gaussian vortex beams of opposite handedness and different amplitudes are derived based on the complex-source-point method, stemming from Maxwell's vector equations and the Lorenz gauge condition. The general solutions exhibiting unusual effects satisfy the Helmholtz and Maxwell's equations. The EM beam components are characterized by nonzero integer degree and order (n ,m ) , respectively, an arbitrary waist w0, a diffraction convergence length known as the Rayleigh range zR, and a weighting (real) factor 0 ≤α ≤1 that describes the transition of the beam from a purely vortex (α =0 ) to a nonvortex (α =1 ) type. An attractive feature for this superposition is the description of strongly focused (or strongly divergent) wave fields. Computations of the EM power density as well as the linear and angular momentum density fluxes illustrate the analysis with particular emphasis on the polarization states of the vector potentials forming the beams and the weight of the coherent beam superposition causing the transition from the vortex to the nonvortex type. Should some conditions determined by the polarization state of the vector potentials and the beam parameters be met, an axial zero-energy flux density is predicted in addition to a negative retrograde propagation effect. Moreover, rotation reversal of the angular momentum flux density with respect to the beam handedness is anticipated, suggesting the possible generation of negative (left-handed) torques. The results are particularly useful in applications involving the design of strongly focused optical laser

  2. Beat wave excitation of electron plasma wave by relativistic cross focusing of cosh-Gaussian laser beams in plasma

    Science.gov (United States)

    Singh, Arvinder; Gupta, Naveen

    2015-06-01

    A scheme for beat wave excitation of electron plasma wave (EPW) is proposed by relativistic cross-focusing of two coaxial Cosh-Gaussian (ChG) laser beams in an under dense plasma. The plasma wave is generated on account of beating of two coaxial laser beams of frequencies ω1 and ω2 . The mechanism for laser produced nonlinearity is assumed to be relativistic nonlinearity in electron mass. Following moment theory approach in Wentzel Kramers Brillouin (W.K.B) approximation, the coupled differential equations governing the evolution of spot size of laser beams with distance of propagation have been derived. The relativistic nonlinearity depends not only on the intensity of first laser beam but also on the intensity of second laser beam. Therefore, propagation dynamics of one laser beam affect that of second beam and hence cross-focusing of the two laser beams takes place. Due to non uniform intensity distribution of pump laser beams, the background electron concentration gets modified. The amplitude of EPW, which depends on the background electron concentration, thus gets nonlinearly coupled with the laser beams. The effects of relativistic electron mass nonlinearity and the cross-focusing of pump beams on excitation of EPW have been incorporated. Numerical simulations have been carried out to investigate the effect of laser as well as plasma parameters on cross-focusing of laser beams and further its effect on power of excited EPW.

  3. Annular spherically focused ring transducers for improved single-beam acoustical tweezers

    Energy Technology Data Exchange (ETDEWEB)

    Mitri, F. G., E-mail: F.G.Mitri@ieee.org [Chevron, Area 52 Technology—ETC, Santa Fe, New Mexico 87508 (United States)

    2016-02-14

    The use of ultrasonic transducers with a central hollow is suggested for improved single-beam acoustical tweezers applications. Within the framework of the Fresnel-Kirchhoff parabolic approximation, a closed-form partial-wave series expansion (PWSE) for the incident velocity potential (or pressure) field is derived for an annular spherically focused ring (asfr) with uniform vibration across its surface in spherical coordinates. The Rayleigh-Sommerfeld diffraction integral and the addition theorems for the Legendre and spherical wave functions are used to obtain the PWSE assuming a weakly focused beam (with a focusing angle α ≤ 20°). The PWSE allows evaluating the incident field from the finite asfr in 3D. Moreover, the obtained solution allows computing efficiently the acoustic scattering and radiation force on a sphere centered on the beam's axis of wave propagation. The analytical solution is valid for wavelengths largely exceeding the radius of the asfr and when the viscosity of the surrounding fluid can be neglected. Numerical predictions for the beam-forming, scattering, and axial time-averaged radiation force are performed with particular emphasis on the asfr thickness, the axial distance separating the sphere from the center of the transducer, the (non-dimensional) size of the transducer, as well as the sphere's elastic properties without restriction to the long- (i.e., Rayleigh) or the short-wavelength (i.e., ray acoustics) regimes. Potential applications of the present solution are in beam-forming design, particle tweezing, and manipulation due to negative forces using ultrasonic asfr transducers.

  4. Annular spherically focused ring transducers for improved single-beam acoustical tweezers

    Science.gov (United States)

    Mitri, F. G.

    2016-02-01

    The use of ultrasonic transducers with a central hollow is suggested for improved single-beam acoustical tweezers applications. Within the framework of the Fresnel-Kirchhoff parabolic approximation, a closed-form partial-wave series expansion (PWSE) for the incident velocity potential (or pressure) field is derived for an annular spherically focused ring (asfr) with uniform vibration across its surface in spherical coordinates. The Rayleigh-Sommerfeld diffraction integral and the addition theorems for the Legendre and spherical wave functions are used to obtain the PWSE assuming a weakly focused beam (with a focusing angle α ≤ 20°). The PWSE allows evaluating the incident field from the finite asfr in 3D. Moreover, the obtained solution allows computing efficiently the acoustic scattering and radiation force on a sphere centered on the beam's axis of wave propagation. The analytical solution is valid for wavelengths largely exceeding the radius of the asfr and when the viscosity of the surrounding fluid can be neglected. Numerical predictions for the beam-forming, scattering, and axial time-averaged radiation force are performed with particular emphasis on the asfr thickness, the axial distance separating the sphere from the center of the transducer, the (non-dimensional) size of the transducer, as well as the sphere's elastic properties without restriction to the long- (i.e., Rayleigh) or the short-wavelength (i.e., ray acoustics) regimes. Potential applications of the present solution are in beam-forming design, particle tweezing, and manipulation due to negative forces using ultrasonic asfr transducers.

  5. Superconducting Magnetic Shield of the Beam Vacuum Chamber for ALICE Muon Spectrometer

    CERN Document Server

    Shishov, Yu A; CERN. Geneva; Tsvineva, A G

    1997-01-01

    The operation of the dipole magnet of the ALICE muon spectrometer will require the ramping of the magnetic field in it according to the acceleration of the LHC beam. For the superconducting dipole magnet the ramping of the field will complicate the design of the magnet. To avoid the ramping of the magnetic field in the dipole magnet we propose to shield the LHC vacuum chamber inside of the dipole by the superconducting magnetic shield.

  6. Self-focusing of a pulsed electron beam in gases and their ionization

    International Nuclear Information System (INIS)

    A relativistic high-intensity pulsed electron beam generated from a Febetron 706 was strongly self-focused in two pressure regions, i.e., below and above 5 Torr. The dependence of the electron energy spectrum on pressure and path length in He was at first studied by measuring depth-dose distributions in an aluminum-blue cellophane stack. Then, maximum doses of the depth-dose curves in the dosimeter placed on the beam axis at 10.4 cm from the cell window were measured as functions of pressure in He, Ne, Ar, Kr, Xe, H2, D2, N2, O2, N2O, CO2, SF6, CH4, C2H2, C2H4, C2H6, C3H8, CH3F, CHClF2, CCl2F2, He + X, Ar + X, and O2 + X (X: additive gas). The strong self-focusing at pressure lower than 5 Torr is attributed to space-charge neutralization by positive ions due to escaping of secondary electrons. Therefore, relative total ionization cross sections for beam electrons could be obtained in this region. When the spa ce-charge neutralization time becomes shorter than a rise time of the pulsed beam, secondary electrons are accelerated by a backward electric field E sub(z) induced by the pulsed beam so that the self-focusing declines abruptly due to electron avalanching. The beam is self-focused again gradually with further increasing pressure because of suppression of this avalanching. The avalanching was analyzed self-consistently for He, Ar, H2, N2, and CH4 by a computer simulation in the pressure region between 5 and 300 Torr. The present computational results indicate that the larger cose is given by the longer mean ionization time t sub(i) which depends on E sub(z)/p. The value of t sub(i) increases with increasing pressure in the pressure region of gradually-increasing self-focusing. (J.P.N.)

  7. From x-ray telescopes to neutron scattering: Using axisymmetric mirrors to focus a neutron beam

    Energy Technology Data Exchange (ETDEWEB)

    Khaykovich, B., E-mail: bkh@mit.ed [Nuclear Reactor Laboratory, Massachusetts Institute of Technology, 138 Albany Street, Cambridge, MA 02139 (United States); Gubarev, M.V. [Marshall Space Flight Center, NASA, VP62, Huntsville, AL 35812 (United States); Bagdasarova, Y. [Department of Physics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Ramsey, B.D. [Marshall Space Flight Center, NASA, VP62, Huntsville, AL 35812 (United States); Moncton, D.E. [Nuclear Reactor Laboratory, Massachusetts Institute of Technology, 138 Albany Street, Cambridge, MA 02139 (United States); Department of Physics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States)

    2011-03-01

    We demonstrate neutron beam focusing by axisymmetric mirror systems based on a pair of mirrors consisting of a confocal ellipsoid and hyperboloid. Such a system, known as a Wolter mirror configuration, is commonly used in X-ray telescopes. The axisymmetric Wolter geometry allows nesting of several mirror pairs to increase collection efficiency. We implemented a system containing four nested Ni mirror pairs, which was tested by the focusing of a polychromatic neutron beam at the MIT Reactor. In addition, we have carried out extensive ray-tracing simulations of the mirrors and their performance in different situations. The major advantages of the Wolter mirrors are nesting for large angular collection and aberration-free performance. We discuss how these advantages can be utilized to benefit various neutron scattering methods, such as imaging, SANS, and time-of-flight spectroscopy.

  8. From x-ray telescopes to neutron scattering: Using axisymmetric mirrors to focus a neutron beam

    International Nuclear Information System (INIS)

    We demonstrate neutron beam focusing by axisymmetric mirror systems based on a pair of mirrors consisting of a confocal ellipsoid and hyperboloid. Such a system, known as a Wolter mirror configuration, is commonly used in X-ray telescopes. The axisymmetric Wolter geometry allows nesting of several mirror pairs to increase collection efficiency. We implemented a system containing four nested Ni mirror pairs, which was tested by the focusing of a polychromatic neutron beam at the MIT Reactor. In addition, we have carried out extensive ray-tracing simulations of the mirrors and their performance in different situations. The major advantages of the Wolter mirrors are nesting for large angular collection and aberration-free performance. We discuss how these advantages can be utilized to benefit various neutron scattering methods, such as imaging, SANS, and time-of-flight spectroscopy.

  9. Hexapole State-Selection and Beam Focus of Linear Triatomic Molecules

    Institute of Scientific and Technical Information of China (English)

    LIU Fu-Chun; JIN Ming-Xing; DING Da-Jun

    2006-01-01

    @@ The state selection and beam focus of linear triatomic molecules (OCS, HCN, CICN, BrCN and ICN) with doubling states in a hexapole electric field have been numerically realized. The method is based on a quantum mechanical treatment of the molecular Stark energy and a classical mechanical treatment for the molecular trajectory in the field. In linear molecules with doubling states, the second-order Stark effect can be neglected and the doubling states have the same value of J and M. The influences of the molecular properties, state energies, and the apparatus parameters such as molecular beam temperature and length of the hexapole, on the role of state selection and focus have been discussed. The method established here can be taken as a guide for hexapole experiment of orientation of polar molecules.

  10. Fermilab Main Ring low level RF system modifications for focus free transition beam tests

    International Nuclear Information System (INIS)

    A novel idea for crossing transition energy has been proposed for study in the Fermilab Main Ring accelerator. The idea has been named focus free transition crossing and involves reducing the RF focusing force nearly to zero when the beam energy is near the transition energy by adding a third harmonic to the RF accelerating voltage, and then adjusting the accelerating phase angle to 90 degrees. The modification of the accelerating voltage wave form shape and phase are accomplished by accurate program control of the amplitude and phase of the 53 Mhz RF cavities and a recently installed 159 Mhz cavity. The studies also require interrupting the normal LLRF system beam energy feedback loops in favor of a new energy control loop near the transition energy. This paper describes the functions of the LLRF system electronics recently installed to facilitate this control, and initial operational experience with the system

  11. Single palladium nanowire growth in place assisted by dielectrophoresis and focused ion beam.

    Science.gov (United States)

    La Ferrara, Vera; Alfano, Brigida; Massera, Ettore; Di Francia, Girolamo

    2009-05-01

    Here we report, for the first time, on the combined use of Focused Ion Beam and Dielectrophoresis techniques for the fabrication of a nanodevice whose operating mechanism relies on a single palladium nanowire. Focused Ion Beam is used to deposit, without photolithographic masks, platinum microelectrodes on a silicon/silicon nitride substrate. Dielectrophoresis is employed for assembling the palladium nanowire, starting from a saturated palladium particles solution, and precisely positioning it between the nanocontacts. The nanodevice works as a hydrogen sensor, confirming the reliability of technology. Its electrical response has been recorded, at room temperature, in a dynamic environment, where different hydrogen concentrations, from 0.1% to 4% in dry air, have been introduced. Its sensitivity, towards 0.1% to 1% gas concentrations in dry air, has been calculated, too.

  12. Magnetic field measurements of superconducting magnets for the colliding beam accelerator

    International Nuclear Information System (INIS)

    An important aspect of the development and production of superconducting magnets for the Colliding Beam Accelerator is the measurement of the magnetic field in the aperture of these magnets. The measurements have the three-fold purpose of determining the field quality as compared to the lattice requirements of the CBA, of obtaining the survey data necessary to position the magnets in the CBA tunnel, and lastly, of characterizing the magnetic fields for use in initial and future orbit studies of the CBA proton beams. Since for a superconducting storage accelerator it is necessary to carry out these detailed measurements on many (approx. 1000) magnets and at many current values (approx. 1000), we have chosen, in agreement with previous experience, to develop a system which Fourier analyses the voltages induced in a number of rotating windings and thereby obtains the multipole field components. The important point is that such a measuring system can be fast and precise. It has been used for horizontal measurements of the CBA ring dipoles

  13. Focused-ion beam patterning of organolead trihalide perovskite for subwavelength grating nanophotonic applications

    KAUST Repository

    Alias, Mohd Sharizal

    2015-07-30

    The coherent amplified spontaneous emission and high photoluminescence quantum efficiency of organolead trihalide perovskite have led to research interest in this material for use in photonic devices. In this paper, the authors present a focused-ion beam patterning strategy for methylammonium lead tribromide (MAPbBr3) perovskite crystal for subwavelength grating nanophotonic applications. The essential parameters for milling, such as the number of scan passes, dwell time, ion dose, ion current, ion incident angle, and gas-assisted etching, were experimentally evaluated to determine the sputtering yield of the perovskite. Based on our patterning conditions, the authors observed that the sputtering yield ranged from 0.0302 to 0.0719 μm3/pC for the MAPbBr3 perovskite crystal. Using XeF2 for the focused-ion beam gas-assisted etching, the authors determined that the etching rate was reduced to between 0.40 and 0.97, depending on the ion dose, compared with milling with ions only. Using the optimized patterning parameters, the authors patterned binary and circular subwavelength grating reflectors on the MAPbBr3 perovskite crystal using the focused-ion beam technique. Based on the computed grating structure with around 97% reflectivity, all of the grating dimensions (period, duty cycle, and grating thickness) were patterned with nanoscale precision (>±3 nm), high contrast, and excellent uniformity. Our results provide a platform for utilizing the focused-ion beam technique for fast prototyping of photonic nanostructures or nanodevices on organolead trihalide perovskite.

  14. Direct-writing lithography using laser diode beam focused with single elliptical microlens

    Science.gov (United States)

    Hasan, Md. Nazmul; Haque, Muttahid-Ull; Trisno, Jonathan; Lee, Yung-Chun

    2015-10-01

    A lithography method is proposed for arbitrary patterning using an elliptically diverging laser diode beam focused with a single planoconvex elliptical microlens. Simulations are performed to model the propagation properties of the laser beam and to design the elliptical microlens, which has two different profiles in the x- and y-axis directions. The microlens is fabricated using an excimer laser dragging method and is then attached to the laser diode using double-sided optically cleared adhesive (OCA) tape. Notably, the use of OCA tape removes the need for a complicated alignment procedure and thus significantly reduces the assembly cost. The minimum focused spot of the laser diode beam is investigated by performing single-shot exposure tests on a photoresist (PR) layer. Finally, the practical feasibility of this lithography technique to generate an arbitrary pattern is demonstrated by dotted and continuous features through thin chromium layer deposition on PR and a metal lift-off process. The results show that the minimum feature size for the dotted patterns is around 6.23 μm, while the minimum linewidths for continuous patterns is 6.44 μm. In other words, the proposed focusing technique has significant potential for writing any arbitrary high-resolution pattern for applications like printed circuit board fabrication.

  15. Using an energized oxygen micro-jet for improved graphene etching by focused electron beam

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Songkil; Henry, Mathias [George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Fedorov, Andrei G., E-mail: agf@gatech.edu [George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States)

    2015-12-07

    We report on an improved Focused Electron Beam Induced Etching (FEBIE) process, which exploits heated oxygen delivery via a continuous supersonic micro-jet resulting in faster graphene patterning and better etch feature definition. Positioning a micro-jet in close proximity to a graphene surface with minimal jet spreading due to a continuous regime of gas flow at the exit of the 10 μm inner diameter capillary allows for focused exposure of the surface to reactive oxygen at high mass flux and impingement energy of a supersonic gas stream localized to a small etching area exposed to electron beam. These unique benefits of focused supersonic oxygen delivery to the surface enable a dramatic increase in the etch rate of graphene with no parasitic carbon “halo” deposition due to secondary electrons from backscattered electrons (BSE) in the area surrounding the etched regions. Increase of jet temperature via local nozzle heating provides means for enhancing kinetic energy of impinging oxygen molecules, which further speed up the etch, thus minimizing the beam exposure time and required electron dose, before parasitic carbon film deposition due to BSE mediated decomposition of adsorbed hydrocarbon contaminants has a measurable impact on quality of graphene etched features. Interplay of different physical mechanisms underlying an oxygen micro-jet assisted FEBIE process is discussed with support from experimental observations.

  16. In Situ Mitigation of Subsurface and Peripheral Focused Ion Beam Damage via Simultaneous Pulsed Laser Heating.

    Science.gov (United States)

    Stanford, Michael G; Lewis, Brett B; Iberi, Vighter; Fowlkes, Jason D; Tan, Shida; Livengood, Rick; Rack, Philip D

    2016-04-01

    Focused helium and neon ion (He(+)/Ne(+)) beam processing has recently been used to push resolution limits of direct-write nanoscale synthesis. The ubiquitous insertion of focused He(+)/Ne(+) beams as the next-generation nanofabrication tool-of-choice is currently limited by deleterious subsurface and peripheral damage induced by the energetic ions in the underlying substrate. The in situ mitigation of subsurface damage induced by He(+)/Ne(+) ion exposures in silicon via a synchronized infrared pulsed laser-assisted process is demonstrated. The pulsed laser assist provides highly localized in situ photothermal energy which reduces the implantation and defect concentration by greater than 90%. The laser-assisted exposure process is also shown to reduce peripheral defects in He(+) patterned graphene, which makes this process an attractive candidate for direct-write patterning of 2D materials. These results offer a necessary solution for the applicability of high-resolution direct-write nanoscale material processing via focused ion beams.

  17. Using an energized oxygen micro-jet for improved graphene etching by focused electron beam

    International Nuclear Information System (INIS)

    We report on an improved Focused Electron Beam Induced Etching (FEBIE) process, which exploits heated oxygen delivery via a continuous supersonic micro-jet resulting in faster graphene patterning and better etch feature definition. Positioning a micro-jet in close proximity to a graphene surface with minimal jet spreading due to a continuous regime of gas flow at the exit of the 10 μm inner diameter capillary allows for focused exposure of the surface to reactive oxygen at high mass flux and impingement energy of a supersonic gas stream localized to a small etching area exposed to electron beam. These unique benefits of focused supersonic oxygen delivery to the surface enable a dramatic increase in the etch rate of graphene with no parasitic carbon “halo” deposition due to secondary electrons from backscattered electrons (BSE) in the area surrounding the etched regions. Increase of jet temperature via local nozzle heating provides means for enhancing kinetic energy of impinging oxygen molecules, which further speed up the etch, thus minimizing the beam exposure time and required electron dose, before parasitic carbon film deposition due to BSE mediated decomposition of adsorbed hydrocarbon contaminants has a measurable impact on quality of graphene etched features. Interplay of different physical mechanisms underlying an oxygen micro-jet assisted FEBIE process is discussed with support from experimental observations

  18. Using an energized oxygen micro-jet for improved graphene etching by focused electron beam

    Science.gov (United States)

    Kim, Songkil; Henry, Mathias; Fedorov, Andrei G.

    2015-12-01

    We report on an improved Focused Electron Beam Induced Etching (FEBIE) process, which exploits heated oxygen delivery via a continuous supersonic micro-jet resulting in faster graphene patterning and better etch feature definition. Positioning a micro-jet in close proximity to a graphene surface with minimal jet spreading due to a continuous regime of gas flow at the exit of the 10 μm inner diameter capillary allows for focused exposure of the surface to reactive oxygen at high mass flux and impingement energy of a supersonic gas stream localized to a small etching area exposed to electron beam. These unique benefits of focused supersonic oxygen delivery to the surface enable a dramatic increase in the etch rate of graphene with no parasitic carbon "halo" deposition due to secondary electrons from backscattered electrons (BSE) in the area surrounding the etched regions. Increase of jet temperature via local nozzle heating provides means for enhancing kinetic energy of impinging oxygen molecules, which further speed up the etch, thus minimizing the beam exposure time and required electron dose, before parasitic carbon film deposition due to BSE mediated decomposition of adsorbed hydrocarbon contaminants has a measurable impact on quality of graphene etched features. Interplay of different physical mechanisms underlying an oxygen micro-jet assisted FEBIE process is discussed with support from experimental observations.

  19. Investigation of wide-aperture plasmonic detectors by a tightly focused terahertz beam

    International Nuclear Information System (INIS)

    Terahertz response of wide-aperture plasmonic detectors is studied experimentally by using a focused terahertz radiation with frequencies 1.63, 1.89 and 2.55 THz. Two different types of plasmonic detector have been investigated: (i) field-effect transistor (FET) with a grating-gate of large (2×2 mm2) area and (ii) FET with a single gate and ohmic contacts forming a bow-tie antenna. By raster scanning the detector area by using a tightly focused terahertz beam, we studied the contribution of individual parts of the detector to the total detection response and we determined the effective area of the detector structures

  20. An improved beam waist formula for ultrashort, tightly-focused linearly, radially, and azimuthally polarized laser pulses in free space

    OpenAIRE

    Wong, Liang Jie; Kaertner, Franz; Johnson, Steven G.

    2013-01-01

    We derive an asymptotically accurate formula for the beam waist of ultrashort, tightly focused fundamental linearly polarized, radially polarized, and azimuthally polarized modes in free space. We compute the exact beam waist via numerical cubature to ascertain the accuracy with which our formula approximates the exact beam waist over a broad range of parameters of practical interest. Based on this, we describe a method of choosing parameters in the model given the beam waist and pulse durati...

  1. Fabrication of high sensitivity 3D nanoSQUIDs based on a focused ion beam sculpting technique

    Science.gov (United States)

    De Leo, Natascia; Fretto, Matteo; Lacquaniti, Vincenzo; Granata, Carmine; Vettoliere, Antonio

    2016-09-01

    In this paper a nanofabrication process, based on a focused ion beam (FIB) nanosculpting technique, for high sensitivity three-dimensional nanoscale superconducting quantum interference devices (nanoSQUIDs) is reported. The crucial steps of the fabrication process are described, as are some peculiar features of the superconductor-normal metal-insulator-superconductor (SNIS) Josephson junctions, which may useful for applications in cryocooler systems. This fabrication procedure is employed to fabricate sandwich nanojunctions and high sensitivity nanoSQUIDs. Specifically, the superconductive nanosensors have a rectangular loop of 1 × 0.2-0.4 μm2 interrupted by two square Nb/Al-AlO x /Nb SNIS Josephson junctions with side lengths of 0.3 μm. The characterization of a typical nanoSQUID has been carried out and a spectral density of magnetic flux noise as low as 0.8 μΦ0 Hz-1/2 has been measured.

  2. Fabrication of high sensitivity 3D nanoSQUIDs based on a focused ion beam sculpting technique

    Science.gov (United States)

    De Leo, Natascia; Fretto, Matteo; Lacquaniti, Vincenzo; Granata, Carmine; Vettoliere, Antonio

    2016-09-01

    In this paper a nanofabrication process, based on a focused ion beam (FIB) nanosculpting technique, for high sensitivity three-dimensional nanoscale superconducting quantum interference devices (nanoSQUIDs) is reported. The crucial steps of the fabrication process are described, as are some peculiar features of the superconductor–normal metal–insulator–superconductor (SNIS) Josephson junctions, which may useful for applications in cryocooler systems. This fabrication procedure is employed to fabricate sandwich nanojunctions and high sensitivity nanoSQUIDs. Specifically, the superconductive nanosensors have a rectangular loop of 1 × 0.2–0.4 μm2 interrupted by two square Nb/Al–AlO x /Nb SNIS Josephson junctions with side lengths of 0.3 μm. The characterization of a typical nanoSQUID has been carried out and a spectral density of magnetic flux noise as low as 0.8 μΦ0 Hz–1/2 has been measured.

  3. Generation of Vortex Beams with Strong Longitudinally Polarized Magnetic Field by Using a Metasurface

    CERN Document Server

    Veysi, Mehdi; Capolino, Filippo

    2014-01-01

    A novel method of generation and synthesis of azimuthally E-polarized vortex beams is presented. Along the axis of propagation such beams have a strong longitudinally polarized magnetic field where ideally there is no electric field. We show how these beams can be constructed through the interference of Laguerre-Gaussian beams carrying orbital angular momentum. As an example, we present a metasurface made of double-split ring slot pairs and report a good agreement between simulated and analytical results. Both a high magnetic-to-electric-field contrast ratio and a magnetic field enhancement are achieved. We also investigate the metasurface physical constraints to convert a linearly polarized beam into an azimuthally E- polarized beam and characterize the performance of magnetic field enhancement and electric field suppression of a realistic metasurface. These findings are potentially useful for novel optical spectroscopy related to magnetic dipolar transitions and for optical manipulation of particles with sp...

  4. Magnetic Resonance-Guided High-Intensity Focused Ultrasound (MR-HIFU) in Treatment of Symptomatic Uterine Myomas

    International Nuclear Information System (INIS)

    Magnetic Resonance-guided High-Intensity Focused Ultrasound (MR-HIFU) is a noninvasive technique for ablation therapy for uterine myomas, where focused ultrasound energy beam generates localized high temperature in the selected area and coagulates chosen tissue, leaving the skin and tissues in between unharmed. Magnetic resonance imaging enables accurate targeting for HIFU as well as temperature monitoring during treatment. MR guidance with 3D anatomical imaging provides reference data for treatment planning, while real-time temperature monitoring aids in controlling ablation process. This review provides basic information regarding methodology, clinical indications for this kind of treatment, expected outcome and patient management during MR-HIFU procedure. The aim of this work is to introduce a new, noninvasive treatment method for uterine leiomyomas and to present a comparison with other currently used methods

  5. Ultrasensitive detection of microbial cells using magnetic focus enhanced lateral flow sensors.

    Science.gov (United States)

    Ren, Wen; Cho, Il-Hoon; Zhou, Zhongwu; Irudayaraj, Joseph

    2016-04-01

    We report on an improved lateral flow immunoassay (LFIA) sensor with a magnetic focus for ultrasensitive naked-eye detection of pathogenic microorganisms at a near single cell limit without any pre-enrichment steps, by allowing the magnetic probes to focus the labelled pathogens to the target zone of the LF strip.

  6. Shaping symmetric Airy beam through binary amplitude modulation for ultralong needle focus

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Zhao-Xiang; Gong, Lei [Department of Optics and Optical Engineering, University of Science and Technology of China, Hefei 230026 (China); Ren, Yu-Xuan, E-mail: yxren@ustc.edu.cn [National Center for Protein Sciences Shanghai, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Shanghai 200031 (China); Vaveliuk, Pablo [Centro de Investigaciones Opticas (CONICET La Plata-CIC), Cno. Centenario y 506, P.O. Box 3, 1897 Gonnet, La Plata, Pcia. de Buenos Aires (Argentina); Chen, Yue; Lu, Rong-De, E-mail: lrd@ustc.edu.cn [Physics Experiment Teaching Center, School of Physical Sciences, University of Science and Technology of China, Hefei 230026 (China)

    2015-11-28

    Needle-like electromagnetic field has various advantages for the applications in high-resolution imaging, Raman spectroscopy, as well as long-distance optical transportation. The realization of such field often requires high numerical aperture (NA) objective lens and the transmission masks. We demonstrate an ultralong needle-like focus in the optical range produced with an ordinary lens. This is achieved by focusing a symmetric Airy beam (SAB) generated via binary spectral modulation with a digital micromirror device. Such amplitude modulation technique is able to shape traditional Airy beams, SABs, as well as the dynamic transition modes between the one-dimensional and two-dimensional (2D) symmetric Airy modes. The created 2D SAB was characterized through measurement of the propagating fields with one of the four main lobes blocked by an opaque mask. The 2D SAB was verified to exhibit self-healing property against propagation with the obstructed major lobe reconstructed after a certain distance. We further produced an elongated focal line by concentrating the SAB via lenses with different NAs and achieved an ultralong longitudinal needle focus. The produced long needle focus will be applied in optical, chemical, and biological sciences.

  7. Damage in III-V compounds during focused ion beam milling.

    Science.gov (United States)

    Rubanov, S; Munroe, P R

    2005-10-01

    The damage layers generated in III-V compounds exposed to energetic gallium ions in a focused ion beam (FIB) instrument have been characterized by transmission electron microscopy (TEM). The damage on the side walls of the milled trenches is in the form of amorphous layers associated with direct amorphization from the gallium beam, rather than from redeposition of milled material. However, the damage on the bottom of the milled trenches is more complex. For InP and InAs the damage layers include the presence of crystalline phases resulting from recrystallization associated heating from the incident beam and gallium implantation. In contrast, such crystalline phases are not present in GaAs. The thicknesses of the damage layers are greater than those calculated from theoretical models of ion implantation. These differences arise because the dynamic nature of FIB milling means that the energetic ion beams pass through already damaged layers. In InP recoil phosphorus atoms also cause significant damage.

  8. Focused particle beam nano-machining: the next evolution step towards simulation aided process prediction.

    Science.gov (United States)

    Plank, Harald

    2015-02-01

    During the last decade, focused ion beam processing has been developed from traditionally used Ga(+) liquid ion sources towards higher resolution gas field ion sources (He(+) and Ne(+)). Process simulations not only improve the fundamental understanding of the relevant ion-matter interactions, but also enable a certain predictive power to accelerate advances. The historic 'gold' standard in ion-solid simulations is the SRIM/TRIM Monte Carlo package released by Ziegler, Ziegler and Biersack 2010 Nucl. Instrum. Methods B 268 1818-23. While SRIM/TRIM is very useful for a myriad of applications, it is not applicable for the understanding of the nanoscale evolution associated with ion beam nano-machining as the substrate does not evolve with the sputtering process. As a solution for this problem, a new, adapted simulation code is briefly overviewed and finally addresses these contributions. By that, experimentally observed Ne(+) beam sputter profiles can be explained from a fundamental point of view. Due to their very good agreement, these simulations contain the potential for computer aided optimization towards predictable sputter processes for different nanotechnology applications. With these benefits in mind, the discussed simulation approach represents an enormous step towards a computer based master tool for adaptable ion beam applications in the context of industrial applications.

  9. Focused particle beam nano-machining: the next evolution step towards simulation aided process prediction

    International Nuclear Information System (INIS)

    During the last decade, focused ion beam processing has been developed from traditionally used Ga+ liquid ion sources towards higher resolution gas field ion sources (He+ and Ne+). Process simulations not only improve the fundamental understanding of the relevant ion–matter interactions, but also enable a certain predictive power to accelerate advances. The historic ‘gold’ standard in ion–solid simulations is the SRIM/TRIM Monte Carlo package released by Ziegler, Ziegler and Biersack 2010 Nucl. Instrum. Methods B 268 1818–23. While SRIM/TRIM is very useful for a myriad of applications, it is not applicable for the understanding of the nanoscale evolution associated with ion beam nano-machining as the substrate does not evolve with the sputtering process. As a solution for this problem, a new, adapted simulation code is briefly overviewed and finally addresses these contributions. By that, experimentally observed Ne+ beam sputter profiles can be explained from a fundamental point of view. Due to their very good agreement, these simulations contain the potential for computer aided optimization towards predictable sputter processes for different nanotechnology applications. With these benefits in mind, the discussed simulation approach represents an enormous step towards a computer based master tool for adaptable ion beam applications in the context of industrial applications. (viewpoint)

  10. The positive charging effect of dielectric films irradiated by a focused electron beam

    International Nuclear Information System (INIS)

    Space charge and surface potential profiles are investigated with numerical simulation for dielectric films of SiO2 positively charged by a focused electron beam. By combining the Monte Carlo method and the finite difference method, the simulation is preformed with a newly developed comprehensive two-dimensional model including electron scattering, charge transport and trapping. Results show that the space charge is distributed positively, like a semi-ellipsoid, within a high-density region of electrons and holes, but negatively outside the region due to electron diffusion along the radial and beam incident directions. Simultaneously, peak positions of the positive and negative space charge densities shift outwards or downwards with electron beam irradiation. The surface potential, along the radial direction, has a nearly flat-top around the center, abruptly decreases to negative values outside the high-density region and finally increases to zero gradually. Influences of electron beam and film parameters on the surface potential profile in the equilibrium state are also shown and analyzed. Furthermore, the variation of secondary electron signal of a large-scale integration sample positively charged in scanning electron microscopic observation is simulated and validated by experiment.

  11. Breakdown simulations in a focused microwave beam within the simplified model

    Science.gov (United States)

    Semenov, V. E.; Rakova, E. I.; Glyavin, M. Yu.; Nusinovich, G. S.

    2016-07-01

    The simplified model is proposed to simulate numerically air breakdown in a focused microwave beam. The model is 1D from the mathematical point of view, but it takes into account the spatial non-uniformity of microwave field amplitude along the beam axis. The simulations are completed for different frequencies and different focal lengths of microwave beams. The results demonstrate complicated regimes of the breakdown evolution which represents a series of repeated ionization waves. These waves start at the focal point and propagate towards incident microwave radiation. The ionization wave parameters vary during propagation. At relatively low frequencies, the propagation regime of subsequent waves can also change qualitatively. Each next ionization wave is less pronounced than the previous one, and the breakdown evolution approaches the steady state with relatively small plasma density. The ionization wave parameters are sensitive to the weak source of external ionization, but the steady state is independent on such a source. As the beam focal length decreases, the stationary plasma density increases and the onset of the steady state occurs faster.

  12. Bright focused ion beam sources based on laser-cooled atoms

    CERN Document Server

    McClelland, J J; Knuffman, B; Twedt, K A; Schwarzkopf, A; Wilson, T M

    2015-01-01

    Nanoscale focused ion beams (FIBs) represent one of the most useful tools in nanotechnology, enabling nanofabrication via milling and gas-assisted deposition, microscopy and microanalysis, and selective, spatially resolved doping of materials. Recently, a new type of FIB source has emerged, which uses ionization of laser cooled neutral atoms to produce the ion beam. The extremely cold temperatures attainable with laser cooling (in the range of 100 uK or below) result in a beam of ions with a very small transverse velocity distribution. This corresponds to a source with extremely high brightness that rivals or may even exceed the brightness of the industry standard Ga+ liquid metal ion source. In this review we discuss the context of ion beam technology in which these new ion sources can play a role, their principles of operation, and some examples of recent demonstrations. The field is relatively new, so only a few applications have been demonstrated, most notably low energy ion microscopy with Li ions. Never...

  13. Bright focused ion beam sources based on laser-cooled atoms

    Science.gov (United States)

    McClelland, J. J.; Steele, A. V.; Knuffman, B.; Twedt, K. A.; Schwarzkopf, A.; Wilson, T. M.

    2016-03-01

    Nanoscale focused ion beams (FIBs) represent one of the most useful tools in nanotechnology, enabling nanofabrication via milling and gas-assisted deposition, microscopy and microanalysis, and selective, spatially resolved doping of materials. Recently, a new type of FIB source has emerged, which uses ionization of laser cooled neutral atoms to produce the ion beam. The extremely cold temperatures attainable with laser cooling (in the range of 100 μK or below) result in a beam of ions with a very small transverse velocity distribution. This corresponds to a source with extremely high brightness that rivals or may even exceed the brightness of the industry standard Ga+ liquid metal ion source. In this review, we discuss the context of ion beam technology in which these new ion sources can play a role, their principles of operation, and some examples of recent demonstrations. The field is relatively new, so only a few applications have been demonstrated, most notably low energy ion microscopy with Li ions. Nevertheless, a number of promising new approaches have been proposed and/or demonstrated, suggesting that a rapid evolution of this type of source is likely in the near future.

  14. New magnet transport system for the LHC beam transfer lines

    CERN Multimedia

    Patrice Loïez

    2003-01-01

    The first of 700 magnets has been installed in one of the two transfer tunnels built to transfer the SPS beam into the LHC. The start of this first installation phase of the LHC transfer lines provides the opportunity to launch a new and highly original modular system for transporting and installing all kinds of magnets in very narrow tunnels. The system (pictured here in one of the tunnels) is based on very compact bogies, up to four of which can be coupled together to form a convoy. The wheels are fitted with individual motors enabling them to swivel through an angle of 90° and the convoy to move laterally. The lead vehicle is powered by an electric rail set into the roof of the tunnel. The system is backed up by electrical batteries that enable it to operate in the absence of an outside power source or in the event of power failure. Last but not least, for the long-distance transport of magnets, it can be optically guided by a line traced on the tunnel floor. The convoy moves through the particularly narr...

  15. 3D micro-optical elements for generation of tightly focused vortex beams

    Directory of Open Access Journals (Sweden)

    Balčytis Armandas

    2015-01-01

    Full Text Available Orbital angular momentum carrying light beams are usedfor optical trapping and manipulation. This emerging trend provides new challenges involving device miniaturization for improved performance and enhanced functionality at the microscale. Here we discus a new fabrication method based on combining the additive 3D structuring capability laser photopolymerization and the substractive sub-wavelength resolution patterning of focused ion beam lithography to produce micro-optical elements capable of compound functionality. As a case in point of this approach binary spiral zone pattern based high numerical aperture micro-lenses capable of generating topological charge carrying tightly focused vortex beams in a single wavefront transformation step are presented. The devices were modelled using finite-difference time-domain simulations, and the theoretical predictions were verified by optically characterizing the propagation properties of light transmitted through the fabricated structures. The resulting devices had focal lengths close to the predicted values of f = 18 µm and f = 13 µm as well as topological charge ℓ dependent vortex focal spot sizes of ~ 1:3 µm and ~ 2:0 µm for ℓ = 1 and ℓ = 2 respectively.

  16. Lateral damage in graphene carved by high energy focused gallium ion beams

    Energy Technology Data Exchange (ETDEWEB)

    Liao, Zhongquan, E-mail: zhongquan.liao@ikts-md.fraunhofer.de [Fraunhofer Institute for Ceramic Technologies and Systems (IKTS), Maria-Reiche-Straße 2, 01109 Dresden (Germany); Dresden Center for Nanoanalysis (DCN), Technische Universität Dresden, Helmholtzstraße 18, 01069 Dresden (Germany); Institute for Materials Science and Max Bergmann Center of Biomaterials, Technische Universität Dresden, Hallwachsstraße 3, 01069 Dresden (Germany); Zhang, Tao; Jordan, Rainer [Professur für Makromolekulare Chemie, Department Chemie, Technische Universität Dresden, Mommsenstraße 4, 01069 Dresden (Germany); Gall, Martin; Rosenkranz, Rüdiger [Fraunhofer Institute for Ceramic Technologies and Systems (IKTS), Maria-Reiche-Straße 2, 01109 Dresden (Germany); Dianat, Arezoo [Institute for Materials Science and Max Bergmann Center of Biomaterials, Technische Universität Dresden, Hallwachsstraße 3, 01069 Dresden (Germany); Cuniberti, Gianaurelio [Institute for Materials Science and Max Bergmann Center of Biomaterials, Technische Universität Dresden, Hallwachsstraße 3, 01069 Dresden (Germany); Center for Advancing Electronics Dresden (cfaed), Technische Universität Dresden, Würzburger Straße 46, 01187 Dresden (Germany); Dresden Center for Computational Materials Science (DCCMS), Technische Universität Dresden, Hallwachsstraße 3, 01069 Dresden (Germany); and others

    2015-07-06

    Raman mapping is performed to study the lateral damage in supported monolayer graphene carved by 30 keV focused Ga{sup +} beams. The evolution of the lateral damage is tracked based on the profiles of the intensity ratio between the D (1341 cm{sup −1}) and G (1582 cm{sup −1}) peaks (I{sub D}/I{sub G}) of the Raman spectra. The I{sub D}/I{sub G} profile clearly reveals the transition from stage 2 disorder into stage 1 disorder in graphene along the direction away from the carved area. The critical lateral damage distance spans from <1 μm up to more than 30 μm in the experiment, depending on the parameters used for carving the graphene. The wide damage in the lateral direction is attributed to the deleterious tail of unfocused ions in the ion beam probe. The study raises the attention on potential sample damage during direct patterning of graphene nanostructures using the focused ion beam technique. Minimizing the total carving time is recommended to mitigate the lateral damage.

  17. Focus modulation of cylindrical vector beams through negative-index grating lenses

    Science.gov (United States)

    Wang, Shengming; Xu, Ji; Zhong, Yi; Ren, Rong; Lu, Yunqing; Wan, Hongdan; Wang, Jin; Ding, Jianping

    2016-08-01

    A cylindrically symmetric negative-index grating lens composed of unitary material is proposed as an effective method to modulate the focusing of cylindrical vector beams (CVBs). The grating parameters are designed to obtain an appropriate negative index, and the lens profile is tailored to realize the constructive interference. The plano-concave lens is parameterized to achieve desired focal length and the plano-cone lens is proposed to obtain large depth of focus. An optical needle is generated with radially polarized incidence, and an optical tube is achieved with incidence of azimuthal polarization. Moreover, the presented modulation methods can be applied for any arbitrary polarized CVBs. This work offers a more flexible and effective approach to design negative-index lenses for subwavelength focusing of CVBs, which has potential application value in related areas, such as optical trapping, and other nano-optics fields.

  18. Focusing a laser beam by means of an off-centre parabolic mirror

    International Nuclear Information System (INIS)

    In this study particular attention was paid to defining and optimizing a focusing system for concentrating a CO2 laser beam (wave length lambda = 10.6 μm) on to a target containing a deuterium and tritium mixture. A digital study of the focusing of a spherical wave, in conjunction with the examination of the properties of reflecting surfaces led to the development of a focusing device using an off-centre parabolic mirror. Despite an aberration of 6 μm in the mirror, the lighting achieved experimentally in the plane of the circle of least scattering is 1.6 times greater than that achieved during the use of an NaCl spherical plane lense

  19. Self-focusing of electromagnetic beams in collisional plasmas with nonlinear absorption

    International Nuclear Information System (INIS)

    In this paper the formalism of self-focusing of electromagnetic waves is extended to include nonlinear absorption by the medium. A complex eikonal has been employed, which does not need any approximation about the relative magnitudes of the real and imaginary parts of the dielectric constant or their dependence on the irradiance of the beam. The specific case of collisional plasmas has been considered as an application of the theory. It is seen that the nonlinearity in absorption tends to cancel the effect of divergence on account of diffraction. The dependence of the beam width and attenuation on distance of propagation has been illustrated for specific cases. The relevance of the investigation to radio wave propagation has also been pointed out

  20. Localized conductive patterning via focused electron beam reduction of graphene oxide

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Songkil; Henry, Mathias [George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Kulkarni, Dhaval D.; Zackowski, Paul; Jang, Seung Soon; Tsukruk, Vladimir V. [School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Fedorov, Andrei G., E-mail: agf@gatech.edu [George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States)

    2015-03-30

    We report on a method for “direct-write” conductive patterning via reduction of graphene oxide (GO) sheets using focused electron beam induced deposition (FEBID) of carbon. FEBID treatment of the intrinsically dielectric graphene oxide between two metal terminals opens up the conduction channel, thus enabling a unique capability for nanoscale conductive domain patterning in GO. An increase in FEBID electron dose results in a significant increase of the domain electrical conductivity with improving linearity of drain-source current vs. voltage dependence, indicative of a change of graphene oxide electronic properties from insulating to semiconducting. Density functional theory calculations suggest a possible mechanism underlying this experimentally observed phenomenon, as localized reduction of graphene oxide layers via interactions with highly reactive intermediates of electron-beam-assisted dissociation of surface-adsorbed hydrocarbon molecules. These findings establish an unusual route for using FEBID as nanoscale lithography and patterning technique for engineering carbon-based nanomaterials and devices with locally tailored electronic properties.

  1. Preparation and Analysis of Atom Probe Tips by Xenon Focused Ion Beam Milling.

    Science.gov (United States)

    Estivill, Robert; Audoit, Guillaume; Barnes, Jean-Paul; Grenier, Adeline; Blavette, Didier

    2016-06-01

    The damage and ion distribution induced in Si by an inductively coupled plasma Xe focused ion beam was investigated by atom probe tomography. By using predefined patterns it was possible to prepare the atom probe tips with a sub 50 nm end radius in the ion beam microscope. The atom probe reconstruction shows good agreement with simulated implantation profiles and interplanar distances extracted from spatial distribution maps. The elemental profiles of O and C indicate co-implantation during the milling process. The presence of small disc-shaped Xe clusters are also found in the three-dimensional reconstruction. These are attributed to the presence of Xe nanocrystals or bubbles that open during the evaporation process. The expected accumulated dose points to a loss of >95% of the Xe during analysis, which escapes undetected.

  2. Ultraviolet Beam Focusing in Gallium Arsenide by Direct Excitation of Surface Plasmon Polaritons

    Directory of Open Access Journals (Sweden)

    Senfeng Lai

    2015-01-01

    Full Text Available This paper proposed that ultraviolet beam could be focused by gallium arsenide (GaAs through direct excitation of surface plasmon polaritons. Both theoretical analysis and computer simulation showed that GaAs could be a reasonably good plasmonic material in the air in the deep ultraviolet waveband. With a properly designed bull’s eye structure etched in GaAs, the ultraviolet electric field could be enhanced to as high as 20 times the incident value, and the full-width-half-maximum (FWHM of the light beam could be shrunk from ~48° to ~6°. As a plasmonic material, GaAs was compared to Ag and Al. Within the studied ultraviolet waveband, the field enhancement in GaAs was much stronger than Ag but not as high as Al.

  3. Propagation of a nonrelativistic electron beam in a plasma in a magnetic field

    International Nuclear Information System (INIS)

    Propagation of a nonrelativistic electron beam in a plasma in a strong magnetic field has been studied using electrostatic one-dimensional particle simulation models. Electron beams of finite pulse length and of continuous injection are followed in time to study the effects of beam-plasma interaction on the beam propagation. For the case of pulsed beam propagation, it is found that the beam distribution rapidly spreads in velocity space generating a plateaulike distribution with a high energy tail extending beyond the initial beam velocity

  4. Interference of Backscatter from Two Droplets in a Focused Continuous Wave CO2 Doppler Lidar Beam

    Science.gov (United States)

    Jarzembski, Maurice A.; Srivastava, Vandana

    1999-01-01

    Interference due to the superposition of backscatter, beta, from two micron-sized droplets using a NASA/MSFC cw (continuous wave) CO2 Doppler lidar at 9.1 micrometer wavelength was detected for the first time. The resultant single beta signal from both droplets contained an interference structure with a well-defined periodicity which was accurately measured and compared with cw lidar theory. The agreement between measurements and theory is excellent, indicating that the interference arises because the droplets are moving at different speeds and, therefore, the relative droplet separation is not constant. This gives the superimposed beta signal from both droplets in the lidar beam moving in and out of constructive and destructive interference with a well-defined periodic structure. A measurement of a time-resolved signal pulse with an oscilloscope of the combined from two approx. 14.12 micrometers in diameter silicone oil droplets responding to the Gaussian lidar beam intensity at the lidar beam focus is shown. Full details of this laboratory experimental setup, particle generation method, measurement technique, and the cw lidar can be found elsewhere. The stream of silicone oil droplets resided at a Doppler-shift center frequency of f (sub D) approx. (3.4 plus or minus 0.2) MHz, giving droplet speed v approx.(21.9 plus or minus 1.3) ms (exp. -1). Also shown on a separate channel is the corresponding signature using an amplitude demodulator circuit designed to detect the amplitude envelope of f(sub D) within the pulse profile. beta from simultaneous droplet events show a complete cyclic interference structure of maximum and minimum. The average period T of the complete cycle of interference is 13.02 plus or minus.39 microseconds. Toward the right edge of the profile, the interference disappears because one of the droplets is leaving the lidar beam while the other one remains in the beam, thus, giving beta for a single droplet.

  5. Design Features of a Planar Hybrid/Permanent Magnet Strong Focusing Undulator for Free Electron Laser (FEL) And Synchrotron Radiation (SR) Applications

    Energy Technology Data Exchange (ETDEWEB)

    Tatchyn, Roman; /SLAC

    2011-09-09

    Insertion devices for Angstrom-wavelength Free Electron Laser (FEL) amplifiers driven by multi-GeV electron beams generally require distributed focusing substantially stronger than their own natural focusing fields. Over the last several years a wide variety of focusing schemes and configurations have been proposed for undulators of this class, ranging from conventional current-driven quadrupoles external to the undulator magnets to permanent magnet (PM) lattices inserted into the insertion device gap. In this paper we present design studies of a flexible high-field hybrid/PM undulator with strong superimposed planar PM focusing proposed for a 1.5 Angstrom Linac Coherent Light Source (LCLS) driven by an electron beam with a 1 mm-mr normalized emittance. Attainable field parameters, tuning modes, and potential applications of the proposed structure are discussed.

  6. Second harmonic generation by self-focusing of intense hollow Gaussian laser beam in collisionless plasma

    International Nuclear Information System (INIS)

    The effect of self focused hollow Gaussian laser beam (HGLB) (carrying null intensity in center) on the excitation of electron plasma wave (EPW) and second harmonic generation (SHG) has been investigated in collisionless plasma, where relativistic-ponderomotive and only relativistic nonlinearities are operative. The relativistic change of electron mass and the modification of the background electron density due to ponderomotive nonlinearity lead to self-focusing of HGLB in plasma. Paraxial ray theory has been used to derive coupled equations for the self focusing of HGLB in plasma, generation of EPW, and second harmonic. These coupled equations are solved analytically and numerically to study the laser intensity in the plasma, electric field associated with the excited EPW, and the power of SHG. Second harmonic emission is generated due to nonlinear coupling between incident HGLB and EPW satisfying the proper phase matching conditions. The results show that the effect of including the ponderomotive nonlinearity is significant on the generation of EPW and second harmonic. The electric field associated with EPW and the power of SHG are found to be highly sensitive to the order of the hollow Gaussian beam

  7. The influence of magnetised electron transport on thermal self-focusing and channelling of nanosecond laser beams

    Science.gov (United States)

    Read, Martin; Kingham, Robert; Bissell, John

    2016-05-01

    The propagation of a nanosecond IR laser pulse through an under-dense (0.01 — 0.1ncr) magnetised laser-plasma is considered. The interplay between magnetised transport, B-field evolution and plasma hydrodynamics in the presence of a dynamically evolving beam are investigated by means of a paraxial wave solving module coupled to CTC, a 2D MHD code including Braginskii electron transport and IMPACT, a 2D implicit Vlasov-Fokker-Planck (VFP) code with magnetic fields. Magnetic fields have previously been shown to improve density channel formation for plasma waveguides however fluid simulations presented here indicate that Nernst advection can result in the rapid cavitation of magnetic field in the laser-heated region resulting in beam defocusing. Kinetic simulations indicate that strong non-local transport is present leading to the fluid code overestimating heat-flow and magnetic field advection and resulting in the recovery of beam channelling for the conditions considered.

  8. Risk and Machine Protection for Stored Magnetic and Beam Energies

    CERN Document Server

    Todd, B

    2015-01-01

    Risk is a fundamental consideration when designing electronic systems. For most systems a view of risk can assist in setting design objectives, whereas both a qualitative and quantitative understanding of risk is mandatory when considering protection systems. This paper gives an overview of the risks due to stored magnetic and beam energies in high-energy physics, and shows how a risk-based approach can be used to design new systems mitigating these risks, using a lifecycle inspired by IEC 61508. Designing new systems in high-energy physics can be challenging as new and novel techniques are difficult to quantify and predict. This paper shows how the same lifecycle approach can be used in reverse to analyse existing systems, following their operation and first experiences.

  9. Radiation damage and its recovery in focused ion beam fabricated ferroelectric capacitors

    Science.gov (United States)

    Stanishevsky, A.; Nagaraj, B.; Melngailis, J.; Ramesh, R.; Khriachtchev, L.; McDaniel, E.

    2002-09-01

    We studied the effect of ion damage on the properties of 50 keV Ga+ focused ion beam fabricated lead-zirconate-titanate capacitors as a function of the ion dose. We observed significant modification in the chemical composition of the damaged layer due to loss of lead and oxygen, and gallium impurity accumulation. The 5-10 nm thick damaged layer becomes dielectric after annealing and does not recover its ferroelectric properties. This dielectric layer substantially reduces the actual volume of the ferroelectric material in sub-100 nm structures, and can affect their performance.

  10. Single Cell Element of Chalcogenide Random Access Memory Fabricated with the Focused Ion Beam Method

    Institute of Scientific and Technical Information of China (English)

    LIU Bo; SONG Zhi-Tang; FENG Song-Lin; CHEN Bomy

    2004-01-01

    A single cell element of chalcogenide random access memory was fabricated by using the focused ion beam method. The contact size between the Ge2Sb2 Te5 phase change film and the top electrode film is about 600nm (diameter) and the contact area is calculated to be 0.28pm2. The thickness of the phase change film is 83nm.The current-voltage characteristics of the cell element are studied using the home-made current-voltage tester in our laboratory. The minimum threshold current of about 0.6mA is obtained.

  11. Nanoelectromechanical device fabrications by 3-D nanotechnology using focused-ion beams

    OpenAIRE

    Reo Kometani and Sunao Ishihara

    2009-01-01

    Nanoelectromechanical devices, which can be used as nanotools in nanofactories, were fabricated by focused ion beam chemical vapor deposition (FIB-CVD). The devices are made of diamond-like carbon (DLC), deposited on a Si substrate using gasified phenanthrene (C14H10) as a carbon source. The Young modulus and density of the deposited DLC were measured as 190 GPa and 3.8 g cm−3, respectively. The work function was smaller for DLC (2.9 eV) than for W (4.7 eV) and Fe (5.2 eV) deposited by FIB-CV...

  12. Selective filling of photonic crystal fibers using focused ion beam milled microchannels

    DEFF Research Database (Denmark)

    Wang, Fei; Yuan, Scott Wu; Hansen, Ole;

    2011-01-01

    We introduce a versatile, robust, and integrated technique to selectively fill fluid into a desired pattern of air holes in a photonic crystal fiber (PCF). Focused ion beam (FIB) is used to efficiently mill a microchannel on the end facet of a PCF before it is spliced to a single-mode fiber (SMF......). Selected air holes are therefore exposed to the atmosphere through the microchannel for fluid filling. A low-loss in-line tunable optical hybrid fiber device is demonstrated by using such a technique. (C) 2011 Optical Society of America...

  13. Lateral control of self-assembled island nucleation by focused-ion-beam micropatterning

    International Nuclear Information System (INIS)

    We demonstrate that the nucleation sites of nanoscale, self-assembled Ge islands on Si(001) can be controlled by patterning the Si surface in situ with a focused ion beam. At low doses of 6000 Ga+ ions per <100 nm spot, the selective growth is achieved without modifying the initial surface topography. At larger doses, topographic effects produced by sputtering and redeposition control the selective nucleation sites. Islands grown on irradiated spots are smaller with higher aspect ratio than islands grown on clean Si(001), suggesting a strong surfactant effect of Ga

  14. Tunable photonic crystals based on ferroelectric and ferromagnetic materials by focused ion beam

    Institute of Scientific and Technical Information of China (English)

    Ziyou Zhou; Xiaoyue Huang; Raghav Vanga; Rong Li

    2007-01-01

    By making photonic crystals in ferroelectric and ferromagnetic materials, field-provoked tunability of photonic crystals is broadening the interest in new applications of on-chip photonic devices. We report a nano-precise fabrication of various designs of photonic crystals in these non-conventional materials using the focused ion beam milling technique. Standard methods are developed and parameters for different materials are calibrated. Optical responses such as bandgaps and polarization status changing from planar film waveguide system with these patterns have been examined on ferromagnetic materials.

  15. ZnO-Based Microcavities Sculpted by Focus Ion Beam Milling.

    Science.gov (United States)

    Chang, Tsu-Chi; Hong, Kuo-Bin; Lai, Ying-Yu; Chou, Yu-Hsun; Wang, Shing-Chung; Lu, Tien-Chang

    2016-12-01

    We reported an easy fabrication method to realize ZnO-based microcavities with various cavity shapes by focused ion beam (FIB) milling. The optical characteristics of different shaped microcavities have been systematically carried out and analyzed. Through comprehensive studies of cathodoluminescence and photoluminescence spectra, the whispering gallery mode (WGM) was observed in different shaped microcavities. Up further increasing excitation, the lasing action was dominated by these WGMs and matched very well to the simulated results. Our experiment shows that ZnO microcavities with different shapes can be made with high quality by FIB milling for specific applications of microlight sources and optical devices. PMID:27364999

  16. Correlative in vivo 2 photon and focused ion beam scanning electron microscopy of cortical neurons.

    Directory of Open Access Journals (Sweden)

    Bohumil Maco

    Full Text Available Correlating in vivo imaging of neurons and their synaptic connections with electron microscopy combines dynamic and ultrastructural information. Here we describe a semi-automated technique whereby volumes of brain tissue containing axons and dendrites, previously studied in vivo, are subsequently imaged in three dimensions with focused ion beam scanning electron microcopy. These neurites are then identified and reconstructed automatically from the image series using the latest segmentation algorithms. The fast and reliable imaging and reconstruction technique avoids any specific labeling to identify the features of interest in the electron microscope, and optimises their preservation and staining for 3D analysis.

  17. Magnetic resonance monitoring of focused ultrasound/magnetic nanoparticle targeting delivery of therapeutic agents to the brain

    OpenAIRE

    Liu, Hao-Li; Hua, Mu-Yi; Yang, Hung-Wei; Huang, Chiung-Yin; Chu, Po-Chun; Wu, Jia-Shin; Tseng, I-Chou; Wang, Jiun-Jie; Yen, Tzu-Chen; Chen, Pin-Yuan; Wei, Kuo-Chen

    2010-01-01

    The superparamagnetic properties of magnetic nanoparticles (MNPs) allow them to be guided by an externally positioned magnet and also provide contrast for MRI. However, their therapeutic use in treating CNS pathologies in vivo is limited by insufficient local accumulation and retention resulting from their inability to traverse biological barriers. The combined use of focused ultrasound and magnetic targeting synergistically delivers therapeutic MNPs across the blood–brain barrier to enter th...

  18. High-current relativistic electron beam shaping in a coaxial diode with magnetic insulation

    International Nuclear Information System (INIS)

    Solution of the problem of relativistic electron beam (REB) for the system with a constant transverse cross-section and thin-wall tubular cathode in an arbitrary magnetic field is presented. The total equation system determining REB parameters as a function of external longitudinal magnetic field is obtained on the base on the laws of conservation of impulse flow and momentum of electron impulse and fields (electrical and magnetic) under the assumption of the electron beam. Calculation results carried out with provision for a diamagnetism and screening of the beam impulse magnetic field by metal are in a good agreement with experimental data

  19. Influence of the substrate material on the knife-edge based profiling of tightly focused light beams

    CERN Document Server

    Huber, C; Banzer, P; Leuchs, G

    2016-01-01

    The performance of the knife-edge method as a beam profiling technique for tightly focused light beams depends on several parameters, such as the material and height of the knife-pad as well as the polarization and wavelength of the focused light beam under study. Here we demonstrate that the choice of the substrate the knife-pads are fabricated on has a crucial influence on the reconstructed beam projections as well. We employ an analytical model for the interaction of the knife-pad with the beam and report good agreement between our numerical and experimental results. Moreover, we simplify the analytical model and demonstrate, in which way the underlying physical effects lead to the apparent polarization dependent beam shifts and changes of the beamwidth for different substrate materials and heights of the knife-pad.

  20. Internal composition of atmospheric dust particles from focused ion-beam scanning electron microscopy.

    Science.gov (United States)

    Conny, Joseph M

    2013-08-01

    Use of focused ion-beam scanning electron microscopy (FIB-SEM) to investigate the internal composition of atmospheric particles is demonstrated for assessing particle optical properties. In the FIB-SEM instrument equipped with an X-ray detector, a gallium-ion beam mills the particle, while the electron beam images the slice faces and energy-dispersive X-ray spectroscopy provides element maps of the particle. Differences in assessments of optical behavior based on FIB-SEM and conventional SEM were shown for five selected urban dust particles. The benefit of FIB-SEM for accurately determining the depth and size of optically important phases within particles was shown. FIB-SEM revealed that iron oxide grains left undetected by conventional SEM could potentially shift the single-scattering albedo of the particle from negative to positive radiative forcing. Analysis of a coke-like particle showed that 73% of the light-scattering inclusion went undetected with conventional SEM, causing the bulk absorption coefficient to vary by as much as 25%. Optical property calculations for particles as volume-equivalent spheres and as spheroids that approximated actual particle shapes revealed that the largest effect between conventional SEM and FIB-SEM analyses was on backscattering efficiency, in some cases varying several-fold. PMID:23763344

  1. Direct patterning of gold oxide thin films by focused ion-beam irradiation

    Science.gov (United States)

    Machalett, F.; Edinger, K.; Melngailis, J.; Diegel, M.; Steenbeck, K.; Steinbeiss, E.

    For direct writing of electrically conducting connections and areas into insulating gold oxide thin films a scanning Ar+ laser beam and a 30 keV Ga+ focused ion beam (FIB) have been used. The gold oxide films are prepared by magnetron sputtering under argon/oxygen plasma. The patterning of larger areas (dimension 10-100 μm) has been carried out with the laser beam by local heating of the selected area above the decomposition temperature of AuOx (130-150 °C). For smaller dimensions (100 nm to 10 μm) the FIB irradiation could be used. With both complementary methods a reduction of the sheet resistance by 6-7 orders of magnitude has been achieved in the irradiated regions (e.g. with FIB irradiation from 1.5×107 Ω/□ to approximately 6 Ω/□). The energy-dispersive X-ray analysis (EDX) show a considerably reduced oxygen content in the irradiated areas, and scanning electron microscopy (SEM), as well as atomic force microscopy (AFM) investigations, indicate that the FIB patterning in the low-dose region (1014 Ga+/cm2) is combined with a volume reduction, which is caused by oxygen escape rather than by sputtering.

  2. Dense Plasma Focus With High Energy Helium Beams for Radiological Source Replacement

    Science.gov (United States)

    Schmidt, Andrea; Ellsworth, Jennifer; Falabella, Steve; Link, Anthony; Rusnak, Brian; Sears, Jason; Tang, Vincent

    2014-10-01

    A dense plasma focus (DPF) is a compact accelerator that can produce intense high energy ion beams (multiple MeV). It could be used in place of americium-beryllium (AmBe) neutron sources in applications such as oil well logging if optimized to produce high energy helium beams. AmBe sources produce neutrons when 5.5 MeV alphas emitted from the Am interact with the Be. However, due to the very small alpha-Be cross section for alphas Simulations will be benchmarked to He beam measurements using filtered and time-of-flight Faraday cup diagnostics. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. This work supported by US DOE/NA-22 Office of Non-proliferation Research and Development. Computing support for this work came from the LLNL Institutional Computing Grand Challenge program.

  3. SWG-designed MMI waveguides for dual and multi-beam splitting, beam position-shifting, and focusing purposes

    Science.gov (United States)

    Abdolahi, Z.; Jiang, H.; Kaminska, B.

    2016-03-01

    In this research, subwavelength grating (SWG) nanostructures with different periodic configurations are designed on a slab dielectric waveguide and theoretically studied for creating beam splitting, position-shifting, and focusing effects, using Comsol Multiphysics as the simulation tool. Su8 with a refractive index (n) of 1.585 is considered as the core material for the dielectric waveguide, which has a lateral and longitudinal dimension of 3 and 6 um, respectively. Uniform and nonuniform rows and columns of nanoholes with diameters of 90 nm are considered as the diffractive design elements. We took advantage of the multimode interference (MMI) phenomenon caused by periodic arrays of nanoholes as SWG structures, which are engineered to induce the desired effects. The power transmission efficiencies of the SWG-designed MMI waveguides are calculated in the wavelength range of 500-1200 nm. The efficiencies are high for the major part of the studied spectrum and reach a maximum of ~97% at 1200 nm for some designs. Also, the refractive index contrasts between the effective index (neff) and the ideal parabolic model (npar) are shown for the conventional MMI SU8 waveguide within a wavelength range of 700-1000 nm. It can be clearly seen that the contrast is minimum for λ = 700nm, and increases with wavelength, showing the multimode interference effect is optimum at 700 nm and deteriorates as the wavelength increases. Modal phase error (MPE) estimated for m=5 and different wavelengths revealed that the MMI device can have a fairly high performance within the whole studied wavelength range for a maximum mode number of 3. Additionally, the field intensity distributions calculated for the design with the beam splitting effect for different wavelengths reflected that the effect has a broadband characteristic.

  4. Subsurface Examination of a Foliar Biofilm Using Scanning Electron- and Focused-Ion-Beam Microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Wallace, Patricia K.; Arey, Bruce W.; Mahaffee, Walt F.

    2011-08-01

    The dual beam scanning electron microscope, equipped with both a focused ion- and scanning electron- beam (FIB SEM) is a novel tool for the exploration of the subsurface structure of biological tissues. The FIB can remove a predetermined amount of material from a selected site to allow for subsurface exploration and when coupled with SEM or scanning ion- beam microscopy (SIM) could be suitable to examine the subsurface structure of bacterial biofilms on the leaf surface. The suitability of chemical and cryofixation was examined for use with the FIB SEM to examine bacterial biofilms on leaf surfaces. The biological control agent, Burkholderia pyroccinia FP62, that rapidly colonizes the leaf surface and forms biofilms, was inoculated onto geranium leaves and incubated in a greenhouse for 7 or 14 days. Cryofixation was not suitable for examination of leaf biofilms because it created a frozen layer over the leaf surface that cracked when exposed to the electron beam and the protective cap required for FIB milling could not be accurately deposited. With chemically fixed samples, it was possible to precisely FIB mill a single cross section (5 µm) or sequential cross sections from a single site without any damage to the surrounding surface. Biofilms, 7 days post-inoculation (DPI), were composed of 2 to 5 bacterial cell layers while biofilms 14 DPI ranged from 5 to greater than 30 cell layers. Empty spaces between bacteria cells in the subsurface structure were observed in biofilms 7- and 14-DPI. Sequential cross sections inferred that the empty spaces were often continuous between FP62 cells and could possibly make up a network of channels throughout the biofilm. FIB SEM was a useful tool to observe the subsurface composition of a foliar biofilm.

  5. Focused ion beam (FIB)/scanning electron microscopy (SEM) in tissue structural research.

    Science.gov (United States)

    Leser, Vladka; Milani, Marziale; Tatti, Francesco; Tkalec, Ziva Pipan; Strus, Jasna; Drobne, Damjana

    2010-10-01

    The focused ion beam (FIB) and scanning electron microscope (SEM) are commonly used in material sciences for imaging and analysis of materials. Over the last decade, the combined FIB/SEM system has proven to be also applicable in the life sciences. We have examined the potential of the focused ion beam/scanning electron microscope system for the investigation of biological tissues of the model organism Porcellio scaber (Crustacea: Isopoda). Tissue from digestive glands was prepared as for conventional SEM or as for transmission electron microscopy (TEM). The samples were transferred into FIB/SEM for FIB milling and an imaging operation. FIB-milled regions were secondary electron imaged, back-scattered electron imaged, or energy dispersive X-ray (EDX) analyzed. Our results demonstrated that FIB/SEM enables simultaneous investigation of sample gross morphology, cell surface characteristics, and subsurface structures. The same FIB-exposed regions were analyzed by EDX to provide basic compositional data. When samples were prepared as for TEM, the information obtained with FIB/SEM is comparable, though at limited magnification, to that obtained from TEM. A combination of imaging, micro-manipulation, and compositional analysis appears of particular interest in the investigation of epithelial tissues, which are subjected to various endogenous and exogenous conditions affecting their structure and function. The FIB/SEM is a promising tool for an overall examination of epithelial tissue under normal, stressed, or pathological conditions.

  6. Functional nickel-based deposits synthesized by focused beam induced processing

    Science.gov (United States)

    Córdoba, R.; Barcones, B.; Roelfsema, E.; Verheijen, M. A.; Mulders, J. J. L.; Trompenaars, P. H. F.; Koopmans, B.

    2016-02-01

    Functional nanostructures fabricated by focused electron/ion beam induced processing (FEBIP/FIBIP) open a promising route for applications in nanoelectronics. Such developments rely on the exploration of new advanced materials. We report here the successful fabrication of nickel-based deposits by FEBIP/FIBIP using bis(methyl cyclopentadienyl)nickel as a precursor. In particular, binary compounds such as nickel oxide (NiO) are synthesized by using an in situ two-step process at room temperature. By this method, as-grown Ni deposits transform into homogeneous NiO deposits using focused electron beam irradiation under O2 flux. This procedure is effective in producing highly pure NiO deposits with resistivity of 2000 Ωcm and a polycrystalline structure with face-centred cubic lattice and grains of 5 nm. We demonstrate that systems based on NiO deposits displaying resistance switching and an exchange-bias effect could be grown by FEBIP using optimized parameters. Our results provide a breakthrough towards using these techniques for the fabrication of functional nanodevices.

  7. Fresnel Number Concept and Revision of some Characteristics in the Linear Theory of Focused Acoustic Beams

    CERN Document Server

    Makov, Yu N

    2008-01-01

    The advisability of the use of the Fresnel number as the measure (characteristic) of the ratio of diffraction and focusing properties for ultrasonic transducers and its radiated beams is proposed and demonstrated. Althought this characteristic is more habitual in optics, in acoustics the equivalent (mathematically although not fully in its physical meaning) parameter of linear gain is used as a rule. However, the preference and the more accuracy of the Fresnel number use is demonstrated here on the basis that the usual determination of the linear gain parameter ceases to correspond to the real value of the gain for low Fresnel number acoustic beams. It connects with the linear effect of axial maximum pressure shift from the geometrical focus towards the transducer. This effect is known for a long time, but here the analytical formulas describing this shift with a high accuracy for arbitrary Fresnel numbers are presented. As a consequence, also the analytical dependence of the real gain on the Fresnel number i...

  8. Shaping symmetric Airy beam through binary amplitude modulation for ultralong needle focus

    CERN Document Server

    Fang, Zhao-Xiang; Gong, Lei; Vaveliuk, Pablo; Chen, Yue; Lu, Rong-De

    2015-01-01

    Needle-like electromagnetic fields has various advantages for the applications in high-resolution imaging, Raman Spectroscopy, as well as long-distance optical transportation. The realization of such field often requires high numerical aperture (NA) objective lens and the transmission masks. We demonstrate an ultralong needle-like focus in the optical range produced with an ordinary lens. This is achieved by focusing a symmetric Airy beam (SAB) generated via binary spectral modulation with a digital micromirror device(DMD). Such amplitude modulation technique is able to shape traditional Airy beams, SABs, as well as the dynamic transition modes between the one-dimensional(1D) and two-dimensional (2D) symmetric Airy modes. The created 2D SAB was characterized through measurement of the propagating fields with one of the four main lobes blocked by an opaque mask. The 2D SAB was verified to exhibit self-healing property against propagation with the obstructed major lobe reconstructed after a certain distance. We...

  9. Mechanisms of material removal and mass transport in focused ion beam nanopore formation

    Energy Technology Data Exchange (ETDEWEB)

    Das, Kallol, E-mail: das7@illinois.edu; Johnson, Harley T., E-mail: htj@illinois.edu [Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, 1206 West Green Street, MC-244, Urbana, Illinois 61801 (United States); Freund, Jonathan B., E-mail: jbfreund@illinois.edu [Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, 1206 West Green Street, MC-244, Urbana, Illinois 61801 (United States); Department of Aerospace Engineering, University of Illinois at Urbana-Champaign, 306 Talbot Laboratory, MC-236, 104 South Wright Street Urbana, Illinois 61801 (United States)

    2015-02-28

    Despite the widespread use of focused ion beam (FIB) processing as a material removal method for applications ranging from electron microscope sample preparation to nanopore processing for DNA sequencing, the basic material removal mechanisms of FIB processing are not well understood. We present the first complete atomistic simulation of high-flux FIB using large-scale parallel molecular dynamics (MD) simulations of nanopore fabrication in freestanding thin films. We focus on the root mechanisms of material removal and rearrangement and describe the role of explosive boiling in forming nanopores. FIB nanopore fabrication is typically understood to occur via sputter erosion. This can be shown to be the case in low flux systems, where individual ion impacts are sufficiently separated in time that they may be considered as independent events. But our detailed MD simulations show that in high flux FIB processing, above a threshold level at which thermal effects become significant, the primary mechanism of material removal changes to a significantly accelerated, thermally dominated process. Under these conditions, the target is heated by the ion beam faster than heat is conducted away by the material, leading quickly to melting, and then continued heating to nearly the material critical temperature. This leads to explosive boiling of the target material with spontaneous bubble formation and coalescence. Mass is rapidly rearranged at the atomistic scale, and material removal occurs orders of magnitude faster than would occur by simple sputtering. While the phenomenology is demonstrated computationally in silicon, it can be expected to occur at lower beam fluxes in other cases where thermal conduction is suppressed due to material properties, geometry, or ambient thermal conditions.

  10. Dynamic T2-mapping during magnetic resonance guided high intensity focused ultrasound ablation of bone marrow

    International Nuclear Information System (INIS)

    Focal bone tumor treatments include amputation, limb-sparing surgical excision with bone reconstruction, and high-dose external-beam radiation therapy. Magnetic resonance guided high intensity focused ultrasound (MR-HIFU) is an effective non-invasive thermotherapy for palliative management of bone metastases pain. MR thermometry (MRT) measures the proton resonance frequency shift (PRFS) of water molecules and produces accurate (2, since T2 increases linearly in fat during heating. T2-mapping using dual echo times during a dynamic turbo spin-echo pulse sequence enabled rapid measurement of T2. Calibration of T2-based thermal maps involved heating the marrow in a bovine femur and simultaneously measuring T2 and temperature with a thermocouple. A positive T2 temperature dependence in bone marrow of 20 ms/°C was observed. Dynamic T2-mapping should enable accurate temperature monitoring during MR-HIFU treatment of bone marrow and shows promise for improving the safety and reducing the invasiveness of pediatric bone tumor treatments.

  11. Generation of Vortex Beams with Strong Longitudinally Polarized Magnetic Field by Using a Metasurface

    OpenAIRE

    Veysi, Mehdi; Guclu, Caner; Capolino, Filippo

    2014-01-01

    A novel method of generation and synthesis of azimuthally E-polarized vortex beams is presented. Along the axis of propagation such beams have a strong longitudinally polarized magnetic field where ideally there is no electric field. We show how these beams can be constructed through the interference of Laguerre-Gaussian beams carrying orbital angular momentum. As an example, we present a metasurface made of double-split ring slot pairs and report a good agreement between simulated and analyt...

  12. Enhanced relativistic self-focusing of Hermite-cosh-Gaussian laser beam in plasma under density transition

    Energy Technology Data Exchange (ETDEWEB)

    Nanda, Vikas; Kant, Niti, E-mail: nitikant@yahoo.com [Department of Physics, Lovely Professional University, Phagwara 144411, Punjab (India)

    2014-04-15

    Enhanced and early relativistic self-focusing of Hermite-cosh-Gaussian (HChG) beam in the plasmas under density transition has been investigated theoretically using Wentzel-Kramers-Brillouin and paraxial ray approximation for mode indices m=0, 1, and 2. The variation of beam width parameter with normalized propagation distance for m=0, 1, and 2 is reported, and it is observed that strong self-focusing occurs as the HChG beam propagates deeper inside the nonlinear medium as spot size shrinks due to highly dense plasmas and the results are presented graphically. A comparative study between self-focusing of HChG beam in the presence and absence of plasmas density transition is reported. The dependency of beam width parameter on the normalized propagation distance for different values of decentered parameter “b” has also been presented graphically. For m=0 and 1, strong self-focusing is reported for b=1.8, and for m=2 and b=1.8, beam gets diffracted. The results obtained indicate the dependency of the self-focusing of the HChG beam on the selected values of decentered parameter. Moreover, proper selection of decentered parameter results strong self-focusing of HChG beam. Stronger self-focusing of laser beam is observed due to the presence of plasma density transition which might be very useful in the applications like the generation of inertial fusion energy driven by lasers, laser driven accelerators, etc.

  13. Enhanced relativistic self-focusing of Hermite-cosh-Gaussian laser beam in plasma under density transition

    International Nuclear Information System (INIS)

    Enhanced and early relativistic self-focusing of Hermite-cosh-Gaussian (HChG) beam in the plasmas under density transition has been investigated theoretically using Wentzel-Kramers-Brillouin and paraxial ray approximation for mode indices m=0, 1, and 2. The variation of beam width parameter with normalized propagation distance for m=0, 1, and 2 is reported, and it is observed that strong self-focusing occurs as the HChG beam propagates deeper inside the nonlinear medium as spot size shrinks due to highly dense plasmas and the results are presented graphically. A comparative study between self-focusing of HChG beam in the presence and absence of plasmas density transition is reported. The dependency of beam width parameter on the normalized propagation distance for different values of decentered parameter “b” has also been presented graphically. For m=0 and 1, strong self-focusing is reported for b=1.8, and for m=2 and b=1.8, beam gets diffracted. The results obtained indicate the dependency of the self-focusing of the HChG beam on the selected values of decentered parameter. Moreover, proper selection of decentered parameter results strong self-focusing of HChG beam. Stronger self-focusing of laser beam is observed due to the presence of plasma density transition which might be very useful in the applications like the generation of inertial fusion energy driven by lasers, laser driven accelerators, etc

  14. Investigation of effect of solenoid magnet on emittances of ion beam from laser ablation plasma

    International Nuclear Information System (INIS)

    A magnetic field can increase an ion current of a laser ablation plasma and is expected to control the change of the plasma ion current. However, the magnetic field can also make some fluctuations of the plasma and the effect on the beam emittance and the emission surface is not clear. To investigate the effect of a magnetic field, we extracted the ion beams under three conditions where without magnetic field, with magnetic field, and without magnetic field with higher laser energy to measure the beam distribution in phase space. Then we compared the relations between the plasma ion current density into the extraction gap and the Twiss parameters with each condition. We observed the effect of the magnetic field on the emission surface

  15. Investigation of effect of solenoid magnet on emittances of ion beam from laser ablation plasma

    Science.gov (United States)

    Ikeda, Shunsuke; Romanelli, Mark; Cinquegrani, David; Sekine, Megumi; Kumaki, Masafumi; Fuwa, Yasuhiro; Kanesue, Takeshi; Okamura, Masahiro; Horioka, Kazuhiko

    2014-02-01

    A magnetic field can increase an ion current of a laser ablation plasma and is expected to control the change of the plasma ion current. However, the magnetic field can also make some fluctuations of the plasma and the effect on the beam emittance and the emission surface is not clear. To investigate the effect of a magnetic field, we extracted the ion beams under three conditions where without magnetic field, with magnetic field, and without magnetic field with higher laser energy to measure the beam distribution in phase space. Then we compared the relations between the plasma ion current density into the extraction gap and the Twiss parameters with each condition. We observed the effect of the magnetic field on the emission surface.

  16. Investigation of effect of solenoid magnet on emittances of ion beam from laser ablation plasma

    Energy Technology Data Exchange (ETDEWEB)

    Ikeda, Shunsuke, E-mail: shunsuke.ikeda@riken.jp; Sekine, Megumi [Tokyo Institute of Technology, Yokohama, Kanagawa (Japan); Riken, Wako, Saitama (Japan); Romanelli, Mark [Cornell University, Ithaca, New York 14850 (United States); Cinquegrani, David [University of Michigan, Ann Arbor, Michigan 48109 (United States); Kumaki, Masafumi [Waseda University, Shinjuku, Tokyo (Japan); Fuwa, Yasuhiro [Kyoto University, Uji, Kyoto (Japan); Kanesue, Takeshi; Okamura, Masahiro [Brookhaven National Laboratory, Upton, New York 11973 (United States); Horioka, Kazuhiko [Tokyo Institute of Technology, Yokohama, Kanagawa (Japan)

    2014-02-15

    A magnetic field can increase an ion current of a laser ablation plasma and is expected to control the change of the plasma ion current. However, the magnetic field can also make some fluctuations of the plasma and the effect on the beam emittance and the emission surface is not clear. To investigate the effect of a magnetic field, we extracted the ion beams under three conditions where without magnetic field, with magnetic field, and without magnetic field with higher laser energy to measure the beam distribution in phase space. Then we compared the relations between the plasma ion current density into the extraction gap and the Twiss parameters with each condition. We observed the effect of the magnetic field on the emission surface.

  17. Simulation of the magnetic mirror effect on a beam of positrons

    CERN Document Server

    Boursette, Delphine

    2014-01-01

    I simulated a beam of positrons at the entrance of a 5 Tesla magnet for the Aegis experiment. The goal was to show how many positrons are lost because of the magnetic mirror effect. To do my simulation, I used Comsol to create the magnetic field map and Geant4 to draw the trajectories of the positrons in this field map.

  18. Modeling an elastic beam with piezoelectric patches by including magnetic effects

    CERN Document Server

    Ozer, A O

    2014-01-01

    Models for piezoelectric beams using Euler-Bernoulli small displacement theory predict the dynamics of slender beams at the low frequency accurately but are insufficient for beams vibrating at high frequencies or beams with low length-to-width aspect ratios. A more thorough model that includes the effects of rotational inertia and shear strain, Mindlin-Timoshenko small displacement theory, is needed to predict the dynamics more accurately for these cases. Moreover, existing models ignore the magnetic effects since the magnetic effects are relatively small. However, it was shown recently \\cite{O-M1} that these effects can substantially change the controllability and stabilizability properties of even a single piezoelectric beam. In this paper, we use a variational approach to derive models that include magnetic effects for an elastic beam with two piezoelectric patches actuated by different voltage sources. Both Euler-Bernoulli and Mindlin-Timoshenko small displacement theories are considered. Due to the magne...

  19. Observation of early and strong relativistic self-focusing of cosh-Gaussian laser beam in cold quantum plasma

    International Nuclear Information System (INIS)

    Relativistic self-focusing of cosh-Gaussian laser beam in the cold quantum plasma has been investigated theoretically using Wentzel-Kramers-Brillouin (WKB) and paraxial ray approximation. The comparative study between self-focusing of cosh-Gaussian laser beam in cold quantum case and classical relativistic case has been made for decentered parameter b = 0.9 and it is observed that as the beam propagates deeper inside the cold quantum plasma, the self-focusing ability of the laser beam enhances and shifted towards lower value of normalized propagation distance due to quantum contribution. The variation of beam width parameter with normalized propagation distance for various values of relative density parameter of the medium and intensity parameter has also been studied. It is observed that with the increase in the value of relative density parameter, self-focusing of laser beam becomes stronger. Observation of early and strong self-focusing for higher values of relative density parameter and intensity parameter are reported. Also, with the increase in the value of the relative density parameter of the medium and intensity parameter, self-focusing ability shifted towards lower value of normalized propagation distance due to relativistic effect. The present study might be very useful in the applications like the generation of inertial fusion energy driven by lasers, laser driven accelerators, scribing type of applications in electronics etc. (author)

  20. Characterizing the focus of a multilayer coated off-axis parabola for FLASH beam at λ = 4.3 nm

    Science.gov (United States)

    Leontowich, Adam F. G.; Aquila, Andrew; Stellato, Francesco; Bean, Richard; Fleckenstein, Holger; Prasciolu, Mauro; Liang, Mengning; DePonte, Daniel P.; Barty, Anton; Wang, Fenglin; Andreasson, Jakob; Hajdu, Janos; Chapman, Henry N.; Bajt, Saša.

    2013-05-01

    A super-polished substrate with an off-axis parabola figure was coated with a Sc/B4C/Cr multilayer. This optic was used to focus pulses of 4.3 nm photons from the Free-electron LASer in Hamburg (FLASH) at normal incidence. Beam imprints were made in poly(methyl methacrylate) to align the optic and to measure the beam profile at the focal plane. The intense interaction resulted in imprints with raised perimeters, surrounded by ablated material extending out several micrometres. These features interfere with the beam profile measurement. The effect of a post-exposure development step on the beam imprints was investigated.

  1. Ponderomotive and weakly relativistic self-focusing of Gaussian laser beam in plasma: Effect of light absorption

    Science.gov (United States)

    Patil, S. D.; Takale, M. V.

    2016-05-01

    This paper presents an influence of light absorption on self-focusing of laser beam propagation in plasma. The differential equation for beam-width parameter is obtained using the Wentzel-Kramers-Brillouin and paraxial approximations through parabolic equation approach. The nonlinearity in dielectric function is assumed to be aroused due to the combined effect of weakly relativistic and ponderomotive regime. To highlight the nature of propagation, behavior of beam-width parameter with dimensionless distance of propagation is presented graphically and discussed. The present work is helpful to understand issues related to the beam propagation in laser plasma interaction experiments where light absorption plays a vital role.

  2. Magnetic resonance-guided focused ultrasound surgery for treatment of painful osseous metastases

    Science.gov (United States)

    Hurwitz, Mark; Machtinger, Ronit; Fennessy, Fiona

    2011-03-01

    Magnetic resonance guided focused ultrasound surgery (MRgFUS) is an emerging technology that can non-invasively heat and ablate targeted tissue utilizing ultrasound energy. Use of MR imaging for treatment guidance provides several key advantages over more widely used ultrasound guidance for focused ultrasound ablation. MR allows for precise targeting, detailed beam path visualization, real time non-invasive temperature measurement, and treatment feedback to ensure therapeutic goals are achieved. In the realm of oncology, management of painful bone metastases is a common and daunting clinical problem. The Insightec ExAblate System has been shown in phase I/II trials for treatment of bone metastases to have an excellent safety profile and high rates of pain response. An international multi-center phase III trial for patients with painful bone metastases or multiple myeloma who are not candidates for radiation therapy is currently open. Patients are randomized 3:1 to MRgFUS or sham treatment with crossover to study treatment allowed for sham failures. The primary study endpoint is assessment of pain control over 3 months following treatment. In addition safety, quality of life, cost effectiveness analysis, and patient perceived clinical benefit are also being assessed. Details of the MRgFUS system, technical and clinical therapeutic parameters, use of real time non-invasive MR thermometry, and examples of patient treatments with use of MRgFUS to treat bone metastases will be discussed. New directions in use of MRgFUS including an update on development of a new mobile applicator and integration of MRgFUS in multimodality oncologic care will also be presented.

  3. Experiments on the margin of beam induced quenches a superconducting quadrupole magnet in the LHC

    CERN Document Server

    Bracco, C; Bednarek, M J; Nebot Del Busto, E; Goddard, B; Holzer, E B; Nordt, A; Sapinski, M; Schmidt, R; Solfaroli Camillocci, M; Zerlauth, M

    2012-01-01

    Protection of LHC equipment relies on a complex system of collimators to capture injected and circulating beam in case of LHC kicker magnet failures. However, for specific failures of the injection kickers, the beam can graze the injection protection collimators and induce quenches of downstream superconducting magnets. This occurred twice during 2011 operation and cannot be excluded during future operation. Tests were performed during Machine Development periods of the LHC to assess the quench margin of the quadrupole located just downstream of the last injection protection collimator in point 8. In addition to the existing Quench Protection System, a special monitoring instrumentation was installed at this magnet to detect any resistance increase below the quench limit. The correlation between the magnet and Beam Loss Monitor signals was analysed for different beam intensities and magnet currents. The results of the experiments are presented.

  4. Mapping of focused Laguerre-Gauss beams: The interplay between spin and orbital angular momentum and its dependence on detector characteristics

    CERN Document Server

    Klimov, Vasily V; Ducloy, Martial; Leite, Jose Roberto Rios

    2012-01-01

    We show that propagating optical fields bearing an axial symmetry are not truly hollow in spite of a null electric field on-axis. The result, obtained by general arguments based upon the vectorial nature of electromagnetic fields, is of particular significance in the situation of an extreme focusing, when the paraxial approximation no longer holds. The rapid spatial variations of fields with a "complicated" spatial structure are extensively analyzed in the general case and for a Laguerre-Gauss beam 2 as well, notably for beams bearing a |l| = 2 orbital angular momentum for which a magnetic field and a gradient of the electric field are present on-axis. We thus analyze the behavior of a atomic size light-detector, sensitive as well to quadrupole electric transitions and to magnetic dipole transitions, and apply it to the case of Laguerre-Gauss beam. We detail how the mapping of such a beam depends on the nature and on the specific orientation of the detector. We show also that the interplay of mixing of polari...

  5. Extraction of a strongly focusing He+ beam from three-stage concave electrodes for alpha particle measurement system in ITER.

    Science.gov (United States)

    Kobuchi, T; Sasao, M; Kisaki, M; Tsumori, K; Tanaka, N; Okamoto, A; Kitajima, S; Kaneko, O; Shinto, K; Wada, M

    2012-02-01

    A strongly focusing He(+) ion beam source equipped with concave multi-aperture electrodes was developed for production of He(-) through a charge exchange cell. The beam was extracted at a voltage less than 20 kV from 301 apertures distributed in an area of 100 mm φ, and focused at 750 mm distance. The beam current and the beam size of 2 A and 20 mm in diameter, respectively, were achieved with an arc power less than 10 kW. The optimum perveance was obtained at 0.02 A∕kV(1.5) at the beam energy less than 20 keV which is suitable for the conversion to He(-) in an alkali vapor cell.

  6. Investigation of Generation, Acceleration, Transport and Final Focusing of High-Intensity Heavy Ion Beams from Sources to Targets

    Energy Technology Data Exchange (ETDEWEB)

    Chiping Chen

    2006-10-26

    Under the auspices of the research grant, the Intense Beam Theoretical Research Goup at Massachusetts Institute of Technology's Plasma Science and Fusion Center made significant contributions in a number of important areas in the HIF and HEDP research, including: (a) Derivation of rms envelope equations and study of rms envelope dynamics for high-intensity heavy ion beams in a small-aperture AG focusing transport systems; (b) Identification of a new mechanism for chaotic particle motion, halo formation, and beam loss in high-intensity heavy ion beams in a small-aperture AG focusing systems; Development of elliptic beam theory; (d) Study of Physics Issues in the Neutralization Transport Experiment (NTX).

  7. Investigation of Generation, Acceleration, Transport and Final Focusing of High-Intensity Heavy Ion Beams from Sources to Targets

    International Nuclear Information System (INIS)

    Under the auspices of the research grant, the Intense Beam Theoretical Research Group at Massachusetts Institute of Technology's Plasma Science and Fusion Center made significant contributions in a number of important areas in the HIF and HEDP research, including: (a) Derivation of rms envelope equations and study of rms envelope dynamics for high-intensity heavy ion beams in a small-aperture AG focusing transport systems; (b) Identification of a new mechanism for chaotic particle motion, halo formation, and beam loss in high-intensity heavy ion beams in a small-aperture AG focusing systems; (c) Development of elliptic beam theory; and (d) Study of Physics Issues in the Neutralization Transport Experiment (NTX)

  8. Focused-electron-beam-induced processing (FEBIP) for emerging applications in carbon nanoelectronics

    International Nuclear Information System (INIS)

    Focused-electron-beam-induced processing (FEBIP), a resist-free additive nanomanufacturing technique, is an actively researched method for ''direct-write'' processing of a wide range of structural and functional nanomaterials, with high degree of spatial and time-domain control. This article attempts to critically assess the FEBIP capabilities and unique value proposition in the context of processing of electronics materials, with a particular emphasis on emerging carbon (i.e., based on graphene and carbon nanotubes) devices and interconnect structures. One of the major hurdles in advancing the carbon-based electronic materials and device fabrication is a disjoint nature of various processing steps involved in making a functional device from the precursor graphene/CNT materials. Not only this multi-step sequence severely limits the throughput and increases the cost, but also dramatically reduces the processing reproducibility and negatively impacts the quality because of possible between-the-step contamination, especially for impurity-susceptible materials such as graphene. The FEBIP provides a unique opportunity to address many challenges of carbon nanoelectronics, especially when it is employed as part of an integrated processing environment based on multiple ''beams'' of energetic particles, including electrons, photons, and molecules. This avenue is promising from the applications' prospective, as such a multi-functional (electron/photon/molecule beam) enables one to define shapes (patterning), form structures (deposition/etching), and modify (cleaning/doping/annealing) properties with locally resolved control on nanoscale using the same tool without ever changing the processing environment. It thus will have a direct positive impact on enhancing functionality, improving quality and reducing fabrication costs for electronic devices, based on both conventional CMOS and emerging carbon (CNT/graphene) materials. (orig.)

  9. Focused-electron-beam-induced processing (FEBIP) for emerging applications in carbon nanoelectronics

    Science.gov (United States)

    Fedorov, Andrei G.; Kim, Songkil; Henry, Mathias; Kulkarni, Dhaval; Tsukruk, Vladimir V.

    2014-12-01

    Focused-electron-beam-induced processing (FEBIP), a resist-free additive nanomanufacturing technique, is an actively researched method for "direct-write" processing of a wide range of structural and functional nanomaterials, with high degree of spatial and time-domain control. This article attempts to critically assess the FEBIP capabilities and unique value proposition in the context of processing of electronics materials, with a particular emphasis on emerging carbon (i.e., based on graphene and carbon nanotubes) devices and interconnect structures. One of the major hurdles in advancing the carbon-based electronic materials and device fabrication is a disjoint nature of various processing steps involved in making a functional device from the precursor graphene/CNT materials. Not only this multi-step sequence severely limits the throughput and increases the cost, but also dramatically reduces the processing reproducibility and negatively impacts the quality because of possible between-the-step contamination, especially for impurity-susceptible materials such as graphene. The FEBIP provides a unique opportunity to address many challenges of carbon nanoelectronics, especially when it is employed as part of an integrated processing environment based on multiple "beams" of energetic particles, including electrons, photons, and molecules. This avenue is promising from the applications' prospective, as such a multi-functional (electron/photon/molecule beam) enables one to define shapes (patterning), form structures (deposition/etching), and modify (cleaning/doping/annealing) properties with locally resolved control on nanoscale using the same tool without ever changing the processing environment. It thus will have a direct positive impact on enhancing functionality, improving quality and reducing fabrication costs for electronic devices, based on both conventional CMOS and emerging carbon (CNT/graphene) materials.

  10. Mechanisms of Focused Ion Beam Implantation Damage and Recovery in Si

    Science.gov (United States)

    Balasubramanian, G. P. S.; Hull, R.

    2016-06-01

    The ion current density in focused ion beam (FIB) systems, 0.1-10 A cm-2, is at least three orders of magnitude greater than that in commercial broad ion beam implanters. This large difference in ion current density is expected to strongly affect the damage recovery dynamics. In this work, we study the ion implantation damage and recovery of Si(100) substrates implanted with 1 × 1012-5 × 1015 Si cm-2 fluences of 60-keV Si2+ at normal incidence in a mass-selecting FIB. Additionally, damage and recovery in different broad ion beam implants of 60-keV Si+ were studied for a comparison. For recovering implantation damage, specimens were annealed for different times at 730-900°C in an ultra-high purity nitrogen ambient, and for characterizing damage and recovery, Raman spectroscopy at wavelengths 405 nm and 514 nm was carried out. Raman measurements comprised of measurements of crystalline Si (c-Si) peak height of the peak at 520 cm-1, and the peak shift relative to that of un-implanted reference Si. Our measurements of structural damage—calculated from the attenuation in the c-Si peak heights for the implants relative to that of unimplanted Si(100)—indicates that the FIB implantations lead to a greater as-implanted damage but also typically lead to a better recovery than that for the commercial broad-area implants. The underlying mechanisms for these observations are discussed.

  11. Through-silicon via plating void metrology using focused ion beam mill

    Science.gov (United States)

    Rudack, A. C.; Nadeau, J.; Routh, R.; Young, R. J.

    2012-03-01

    3D IC integration continues to increase in complexity, employing advanced interconnect technologies such as throughsilicon vias (TSVs), wafer-to-wafer (W2W) bonding, and multi-chip stacking. As always, the challenge with developing new processes is to get fast, effective feedback to the integration engineer. Ideally this data is provided by nondestructive in-line metrology, but this is not always possible. For example, some form of physical cross-sectioning is still the most practical way to detect and characterize TSV copper plating voids. This can be achieved by cleaving, followed by scanning electron microscope (SEM) inspection. A more effective physical cross-sectioning method has been developed using an automated dual-beam focused ion beam (FIB)-SEM system, in which multiple locations can be sectioned and imaged while leaving the wafer intact. This method has been used routinely to assess copper plating voids over the last 24 months at SEMATECH. FIB-SEM feedback has been used to evaluate new plating chemistries, plating recipes, and process tool requalification after downtime. The dualbeam FIB-SEM used for these studies employs a gallium-based liquid metal ion source (LMIS). The overall throughput of relatively large volumes being milled is limited to 3-4 hours per section due to the maximum available beam current of 20 nA. Despite the larger volumetric removal rates of other techniques (e.g., mechanical polishing, broad-ion milling, and laser ablation), the value of localized, site-specific, and artifact-free FIB milling is well appreciated. The challenge, therefore, has been to reap the desired FIB benefits, but at faster volume removal rates. This has led to several system and technology developments for improving the throughput of the FIB technique, the most recent being the introduction of FIBs based on an inductively coupled plasma (ICP) ion source. The ICP source offers much better performance than the LMIS at very high beam currents, enabling more than

  12. Primary Beam Steering Due To Field Leakage From Superconducting SHMS Magnets

    Science.gov (United States)

    Moore, Michael; Covrig, Silviu; Carlini, Roger; Waidyawansa, Buddhini; Benesch, Jay

    2014-03-01

    The Super High Momentum Spectrometer (SHMS) was designed for the 12 GeV/c physics program in Hall C at Thomas Jefferson National Accelerator (JLab). At JLab an electron beam impinges on a fixed target and scattered particles are analyzed with magnetic spectrometers. The SHMS angular acceptance is 5 .5° 51.8 m from the target. The effects of these magnetic fields on the primary beam line downstream of the target are studied using Opera 3-D and TOSCA. A solution is presented that uses passive elements to shape these fields and assure that the primary beam is steered onto the beam dump window.

  13. Bi-spectral beam extraction in combination with a focusing feeder

    CERN Document Server

    Zendler, C; Nekrassov, D; Cussen, L D; Strobl, M

    2013-01-01

    Bi-spectral beam extraction combines neutrons from two different kind of moderators into one beamline, expanding the spectral range and thereby the utilization of an instrument. This idea can be realized by a mirror that reflects long wavelength neutrons from an off-axis colder moderator into a neutron guide aligned with another moderator emitting neutrons with shorter wavelengths which will be transmitted through the mirror. The mirror used in such systems is typically several meters long, which is a severe disadvantage because it reduces the possible length of a focusing device in design concepts requiring a narrow beam at a short distance from the source, as used in many instruments under development for the planned European Spallation Source (ESS). We propose a shortened extraction system consisting of several mirrors, and show that such an extraction system is better suited for combination with a feeder in an eye of the needle design, illustrated here in the context of a possible ESS imaging beamline.

  14. Direct-Write Fabrication of Cellulose Nano-Structures via Focused Electron Beam Induced Nanosynthesis.

    Science.gov (United States)

    Ganner, Thomas; Sattelkow, Jürgen; Rumpf, Bernhard; Eibinger, Manuel; Reishofer, David; Winkler, Robert; Nidetzky, Bernd; Spirk, Stefan; Plank, Harald

    2016-01-01

    In many areas of science and technology, patterned films and surfaces play a key role in engineering and development of advanced materials. Here, we introduce a new generic technique for the fabrication of polysaccharide nano-structures via focused electron beam induced conversion (FEBIC). For the proof of principle, organosoluble trimethylsilyl-cellulose (TMSC) thin films have been deposited by spin coating on SiO2 / Si and exposed to a nano-sized electron beam. It turns out that in the exposed areas an electron induced desilylation reaction takes place converting soluble TMSC to rather insoluble cellulose. After removal of the unexposed TMSC areas, structured cellulose patterns remain on the surface with FWHM line widths down to 70 nm. Systematic FEBIC parameter sweeps reveal a generally electron dose dependent behavior with three working regimes: incomplete conversion, ideal doses and over exposure. Direct (FT-IR) and indirect chemical analyses (enzymatic degradation) confirmed the cellulosic character of ideally converted areas. These investigations are complemented by a theoretical model which suggests a two-step reaction process by means of TMSC → cellulose and cellulose → non-cellulose material conversion in excellent agreement with experimental data. The extracted, individual reaction rates allowed the derivation of design rules for FEBIC parameters towards highest conversion efficiencies and highest lateral resolution. PMID:27585861

  15. Growth of GaN based structures on focused ion beam patterned templates

    Energy Technology Data Exchange (ETDEWEB)

    Cordier, Y.; Tottereau, O.; Nguyen, L. [Centre de Recherche sur l' Heteroepitaxie et ses Application, UPR-CNRS, Valbonne (France); Ramdani, M.; Soltani, A.; Boucherit, M.; Troadec, D.; Lo, F.Y.; Hu, Y.Y.; Ludwig, A.; Wieck, A.D. [Centre de Recherche sur l' Heteroepitaxie et ses Application, UPR-CNRS, Valbonne (France); Institut d' Electronique, de Microelectronique et de Nanotechnologie, Cite Scientifique, Villeneuve d' Ascq (France); Lehrstuhl fuer Angewandte Festkoerperphysik, Ruhr-Universitaet Bochum (Germany)

    2011-05-15

    Focused ion beam technique is a powerful tool for defining patterns within a semiconductor film. In this paper, we show that it is possible to realize patterns such as disks and columns within thick GaN templates and that it is compatible with the regrowth of GaN based heterostructures. We study the effect of the pattern size and shape on the regrowth by molecular beam epitaxy. We show that the growth using ammonia as the nitrogen source with flux at temperature optimized for 2-dimensional growth leads to the apparition of well defined growth planes. We show that the development of these planes is dependent with the initial pattern size and shape. These results confirm the difficulty for realizing micro or nano-columns with axial heterostructures. At the opposite, these growth conditions seem favourable for core-shell heterostructures column with well defined m-plane and eventually a-plane lateral facets. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Bi-spectral beam extraction in combination with a focusing feeder

    Energy Technology Data Exchange (ETDEWEB)

    Zendler, C., E-mail: carolin.zendler@helmholtz-berlin.de [Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin (Germany); ESS Design Update Programme (Germany); Lieutenant, K.; Nekrassov, D.; Cussen, L.D. [Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin (Germany); ESS Design Update Programme (Germany); Strobl, M. [European Spallation Source ESS AB, Box 176, 22100 Lund (Sweden)

    2013-03-11

    Bi-spectral beam extraction combines neutrons from two different kinds of moderators into one beamline, expanding the spectral range and thereby the utilization of an instrument. This idea can be realized by a mirror that reflects long wavelength neutrons from an off-axis colder moderator into a neutron guide aligned with another moderator emitting neutrons with shorter wavelengths which will be transmitted through the mirror. The mirror used in such systems is typically several meters long, which is a severe disadvantage because it reduces the possible length of a focusing device in design concepts requiring a narrow beam at a short distance from the source, as used in many instruments under development for the planned European Spallation Source (ESS). We propose a shortened extraction system consisting of several mirrors and show that such an extraction system is better suited for combination with a feeder in an eye of the needle design, illustrated here in the context of a possible ESS imaging beamline.

  17. In situ growth optimization in focused electron-beam induced deposition

    Directory of Open Access Journals (Sweden)

    Paul M. Weirich

    2013-12-01

    Full Text Available We present the application of an evolutionary genetic algorithm for the in situ optimization of nanostructures that are prepared by focused electron-beam-induced deposition (FEBID. It allows us to tune the properties of the deposits towards the highest conductivity by using the time gradient of the measured in situ rate of change of conductance as the fitness parameter for the algorithm. The effectiveness of the procedure is presented for the precursor W(CO6 as well as for post-treatment of Pt–C deposits, which were obtained by the dissociation of MeCpPt(Me3. For W(CO6-based structures an increase of conductivity by one order of magnitude can be achieved, whereas the effect for MeCpPt(Me3 is largely suppressed. The presented technique can be applied to all beam-induced deposition processes and has great potential for a further optimization or tuning of parameters for nanostructures that are prepared by FEBID or related techniques.

  18. Intracavity contacts for nitride based monolithic surface emitters by focused ion beam processing

    Energy Technology Data Exchange (ETDEWEB)

    Fandrich, Malte; Dartsch, Heiko; Tessarek, Christian; Aschenbrenner, Timo; Hommel, Detlef [Institut fuer Festkoerperphysik - Halbleiterepitaxie, Universitaet Bremen (Germany)

    2010-07-01

    The realization of electrically driven nitride based vertical-cavity surface-emitting lasers (VCSELs) is challenging due to limitations in the conductivity of the distributed Bragg reflectors (DBRs). Therefore monolithic approaches are based on a doped cavity and one or two undoped DBRs. This requires the use of technologically complex intracavity contacts. The presented process yields intracavity contacts applicable to monolithically grown VCSEL structures. Initially mesas are structured by photolithography and chemical assisted ion beam etching. The precise structuring of the prestructured mesas is performed in a focused ion beam system (FIB), where the micropillars are thinned stepwise down to a diameter of 0.5-5 {mu}m. The contacting of the pillars is realized by FIB deposited metal and insulator structures. Insulator separated Pt ring-contacts connect the micropillars with large-scale contact pads. This procedure was applied to a VCSEL structure consisting of a bottom AlInN/GaN-DBR with 40 pairs, a p/n-doped 5 {lambda} GaN-cavity with embedded InGaN quantum dots and a top 10 pair AlInN/GaN-DBR. The developed contacting structure enables a current up to 15 mA through the cavity which documents the capability for the electrical operation of VCSEL devices.

  19. Direct-Write Fabrication of Cellulose Nano-Structures via Focused Electron Beam Induced Nanosynthesis

    Science.gov (United States)

    Ganner, Thomas; Sattelkow, Jürgen; Rumpf, Bernhard; Eibinger, Manuel; Reishofer, David; Winkler, Robert; Nidetzky, Bernd; Spirk, Stefan; Plank, Harald

    2016-09-01

    In many areas of science and technology, patterned films and surfaces play a key role in engineering and development of advanced materials. Here, we introduce a new generic technique for the fabrication of polysaccharide nano-structures via focused electron beam induced conversion (FEBIC). For the proof of principle, organosoluble trimethylsilyl-cellulose (TMSC) thin films have been deposited by spin coating on SiO2 / Si and exposed to a nano-sized electron beam. It turns out that in the exposed areas an electron induced desilylation reaction takes place converting soluble TMSC to rather insoluble cellulose. After removal of the unexposed TMSC areas, structured cellulose patterns remain on the surface with FWHM line widths down to 70 nm. Systematic FEBIC parameter sweeps reveal a generally electron dose dependent behavior with three working regimes: incomplete conversion, ideal doses and over exposure. Direct (FT-IR) and indirect chemical analyses (enzymatic degradation) confirmed the cellulosic character of ideally converted areas. These investigations are complemented by a theoretical model which suggests a two-step reaction process by means of TMSC → cellulose and cellulose → non-cellulose material conversion in excellent agreement with experimental data. The extracted, individual reaction rates allowed the derivation of design rules for FEBIC parameters towards highest conversion efficiencies and highest lateral resolution.

  20. Positioning of self-assembled InAs quantum dots by focused ion beam implantation

    International Nuclear Information System (INIS)

    Self-assembled quantum dots (QDs) are envisioned as building blocks for realization of novel nanoelectronic devices, for which the site-selective growth is highly desirable. This thesis presents a successful route toward selective positioning of self-assembled InAs QDs on patterned GaAs surface by combination of in situ focused ion beam (FIB) implantation and molecular beam epitaxy (MBE) technology. First, a buffer layer of GaAs was grown by MBE before a square array of holes with a pitch of 1-2 μm was fabricated by FIB implantation of Ga and In, ions respectively. Later, an in-situ annealing step followed by InAs deposition was performed. The InAs QDs were preferentially formed in the holes generated by FIB. The influence of ion dose, annealing parameters and InAs amount was investigated in this work. With optimized parameters, more than 50 % single dot occupancy per hole is achieved. Furthermore, the photoluminescence spectra from positioned QDs confirm their good optical quality. (orig.)

  1. Nanoelectromechanical device fabrications by 3-D nanotechnology using focused-ion beams

    Directory of Open Access Journals (Sweden)

    Reo Kometani and Sunao Ishihara

    2009-01-01

    Full Text Available Nanoelectromechanical devices, which can be used as nanotools in nanofactories, were fabricated by focused ion beam chemical vapor deposition (FIB-CVD. The devices are made of diamond-like carbon (DLC, deposited on a Si substrate using gasified phenanthrene (C14H10 as a carbon source. The Young modulus and density of the deposited DLC were measured as 190 GPa and 3.8 g cm−3, respectively. The work function was smaller for DLC (2.9 eV than for W (4.7 eV and Fe (5.2 eV deposited by FIB-CVD. A nanomanipulator was manufactured by FIB-CVD and used for actual manipulations. A glass capillary based local field emitter was developed and produced as a tool for spot deposition, and its electron field emission was confirmed. FIB-CVD is proven as an efficient fabrication technology of novel nanoelectromechanical devices.

  2. Nano-structuring, surface and bulk modification with a focused helium ion beam

    Directory of Open Access Journals (Sweden)

    Daniel Fox

    2012-08-01

    Full Text Available We investigate the ability of a focused helium ion beam to selectively modify and mill materials. The sub nanometer probe size of the helium ion microscope used provides lateral control not previously available for helium ion irradiation experiments. At high incidence angles the helium ions were found to remove surface material from a silicon lamella leaving the subsurface structure intact for further analysis. Surface roughness and contaminants were both reduced by the irradiation process. Fabrication is also realized with a high level of patterning acuity. Implantation of helium beneath the surface of the sample is visualized in cross section allowing direct observation of the extended effects of high dose irradiation. The effect of the irradiation on the crystal structure of the material is presented. Applications of the sample modification process are presented and further prospects discussed.

  3. Scalable Focused Ion Beam Creation of Nearly Lifetime-Limited Single Quantum Emitters in Diamond Nanostructures

    CERN Document Server

    Schröder, Tim; Walsh, Michael; Li, Luozhou; Zheng, Jiabao; Schukraft, Marco; Pacheco, Jose L; Camacho, Ryan M; Bielejec, Edward S; Sipahigil, Alp; Evans, Ruffin E; Sukachev, Denis D; Nguyen, Christian T; Lukin, Mikhail D; Englund, Dirk

    2016-01-01

    The controlled creation of defect center---nanocavity systems is one of the outstanding challenges for efficiently interfacing spin quantum memories with photons for photon-based entanglement operations in a quantum network. Here, we demonstrate direct, maskless creation of atom-like single silicon-vacancy (SiV) centers in diamond nanostructures via focused ion beam implantation with $\\sim 32$ nm lateral precision and $< 50$ nm positioning accuracy relative to a nanocavity. Moreover, we determine the Si+ ion to SiV center conversion yield to $\\sim 2.5\\%$ and observe a 10-fold conversion yield increase by additional electron irradiation. We extract inhomogeneously broadened ensemble emission linewidths of $\\sim 51$ GHz, and close to lifetime-limited single-emitter transition linewidths down to $126 \\pm13$ MHz corresponding to $\\sim 1.4$-times the natural linewidth. This demonstration of deterministic creation of optically coherent solid-state single quantum systems is an important step towards development o...

  4. First evidence of tyre debris characterization at the nanoscale by focused ion beam

    International Nuclear Information System (INIS)

    In this paper, we present a novel technique for the nanoscale characterization of the outer and inner structure of tyre debris. Tyre debris is produced by the normal wear of tyres. In previous studies, the microcharacterization and identification were performed by analytical electron microscopy. This study is a development of the characterization of surface and microstructure of tyre debris. For the first time, tyre debris was analysed by focused ion beam (FIB), a technique with 2- to 5-nm resolution that does not require any sample preparation. We studied tyre debris produced in the laboratory. We made electron and ionic imaging of the surface of the material, and after a ionic cut, we studied the internal microstructure of the same sample. The tyre debris was analysed by FIB without any sample preparations unlike the case of scanning and transmission electron microscopy (SEM and TEM). Useful information was derived to improve detection and monitoring techniques of pollution by tyre degradation processes

  5. Fabrication of nanoelectrodes for neurophysiology: cathodic electrophoretic paint insulation and focused ion beam milling

    Science.gov (United States)

    Qiao, Yi; Chen, Jie; Guo, Xiaoli; Cantrell, Donald; Ruoff, Rodney; Troy, John

    2005-09-01

    The fabrication and characterization of tungsten nanoelectrodes insulated with cathodic electrophoretic paint is described together with their application within the field of neurophysiology. The tip of a 127 µm diameter tungsten wire was etched down to less than 100 nm and then insulated with cathodic electrophoretic paint. Focused ion beam (FIB) polishing was employed to remove the insulation at the electrode's apex, leaving a nanoscale sized conductive tip of 100-1000 nm. The nanoelectrodes were examined by scanning electron microscopy (SEM) and their electrochemical properties characterized by steady state linear sweep voltammetry. Electrode impedance at 1 kHz was measured too. The ability of a 700 nm tipped electrode to record well-isolated action potentials extracellularly from single visual neurons in vivo was demonstrated. Such electrodes have the potential to open new populations of neurons to study.

  6. Dual focused coherent beams for three-dimensional optical trapping and continuous rotation of metallic nanostructures

    Science.gov (United States)

    Xu, Xiaohao; Cheng, Chang; Zhang, Yao; Lei, Hongxiang; Li, Baojun

    2016-01-01

    Metallic nanoparticles and nanowires are extremely important for nanoscience and nanotechnology. Techniques to optically trap and rotate metallic nanostructures can enable their potential applications. However, because of the destabilizing effects of optical radiation pressure, the optical trapping of large metallic particles in three dimensions is challenging. Additionally, the photothermal issues associated with optical rotation of metallic nanowires have far prevented their practical applications. Here, we utilize dual focused coherent beams to realize three-dimensional (3D) optical trapping of large silver particles. Continuous rotation of silver nanowires with frequencies measured in several hertz is also demonstrated based on interference-induced optical vortices with very low local light intensity. The experiments are interpreted by numerical simulations and calculations. PMID:27386838

  7. First demonstration of X-ray mirrors using focused ion beam

    Science.gov (United States)

    Numazawa, Masaki; Ezoe, Yuichiro; Ishikawa, Kumi; Ogawa, Tomohiro; Sato, Mayu; Nakamura, Kasumi; Takeuchi, Kazuma; Terada, Masaru; Ohashi, Takaya; Mitsuda, Kazuhisa; Kelley, Ron; Murata, Kaoru

    2016-06-01

    We report on novel X-ray mirrors fabricated with a focused ion beam for future astronomical missions. We fabricated a test sample from a silicon wafer by forming six slits whose sidewalls were used as X-ray reflection surfaces. The six slits were designed with a size of 25 × 300 × 170 µm3 and with different inclination angles of 0 and ±1°. We examined X-ray reflection using three slits with different inclination angles at Al Kα 1.49 keV. Consequently, we demonstrated X-ray reflection from all the three slits. All the sidewalls have multiangular components with a microroughness of ˜1 nm rms. ˜30-45% of the total surface area is effective for X-ray reflection. We confirmed that the inclination angles are consistent with the designed values.

  8. Membrane Thickness Dependence of Nanopore Formation with a Focused Helium Ion Beam

    Directory of Open Access Journals (Sweden)

    Furat Sawafta

    2014-05-01

    Full Text Available Solid-state nanopores are emerging as a valuable tool for the detection and characterization of individual biomolecules. Central to their success is the realization of fabrication strategies that are both rapid and flexible in their ability to achieve diverse device dimensions. In this paper, we demonstrate the membrane thickness dependence of solid-state nanopore formation with a focused helium ion beam. We vary membrane thickness in situ and show that the rate of pore expansion follows a reproducible trend under all investigated membrane conditions. We show that this trend shifts to lower ion dose for thin membranes in a manner that can be described quantitatively, allowing devices of arbitrary dimension to be realized. Finally, we demonstrate that thin, small-diameter nanopores formed with our approach can be utilized for high signal-to-noise ratio resistive pulse sensing of DNA.

  9. Ultrahigh resolution focused electron beam induced processing: the effect of substrate thickness

    DEFF Research Database (Denmark)

    van Dorp, Willem F; Lazic, Ivan; Beyer, André;

    2011-01-01

    It is often suggested that the growth in focused electron beam induced processing (FEBIP) is caused not only by primary electrons, but also (and even predominantly) by secondary electrons (SEs). If that is true, the growth rate for FEBIP can be changed by modifying the SE yield. Results from our...... Monte Carlo simulations show that the SE yield changes strongly with substrate thickness for thicknesses below the SE escape depth. However, our experimental results show that the growth rate is independent of the substrate thickness. Deposits with an average size of about 3 nm were written on 1 and 9...... nm thick carbon substrates. The apparent contradiction between simulation and experiment is explained by simulating the SE emission from a carbon substrate with platinum deposits on the surface. It appears that the SE emission is dominated by the deposits rather than the carbon substrate, even for...

  10. Heavy charged particle radiobiology: using enhanced biological effectiveness and improved beam focusing to advance cancer therapy.

    Science.gov (United States)

    Allen, Christopher; Borak, Thomas B; Tsujii, Hirohiko; Nickoloff, Jac A

    2011-06-01

    Ionizing radiation causes many types of DNA damage, including base damage and single- and double-strand breaks. Photons, including X-rays and γ-rays, are the most widely used type of ionizing radiation in radiobiology experiments, and in radiation cancer therapy. Charged particles, including protons and carbon ions, are seeing increased use as an alternative therapeutic modality. Although the facilities needed to produce high energy charged particle beams are more costly than photon facilities, particle therapy has shown improved cancer survival rates, reflecting more highly focused dose distributions and more severe DNA damage to tumor cells. Despite early successes of charged particle radiotherapy, there is room for further improvement, and much remains to be learned about normal and cancer cell responses to charged particle radiation.

  11. A semiconductor metasurface with multiple functionalities: A polarizing beam splitter with simultaneous focusing ability

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jun Hyung; Jin Jung, Myoung; Ho Song, Seok, E-mail: shsong@hanyang.ac.kr [Department of Physics, Hanyang University, Seoul (Korea, Republic of); Woong Yoon, Jae; Magnusson, Robert [Department of Electrical Engineering, University of Texas–Arlington, Arlington, Texas 76019 (United States); Kyun Hong, Jong [Department of Electrical Engineering, Hanyang University, Seoul (Korea, Republic of)

    2014-06-09

    We propose a semiconductor metasurface that simultaneously performs two independent functions: focusing and polarization filtering. The wavefronts of the reflected and transmitted light distributions are precisely manipulated by spatial parametric variation of a subwavelength thin-film Si grating, which inherently possesses polarization filtering properties. We design a 12-μm-wide metasurface containing only nineteen Si grating ridges. Under a 10-μm-wide unpolarized Gaussian beam incidence at wavelength of 1.55 μm, the resulting device shows promising theoretical performance with high power efficiency exceeding 80% and polarization extinction ratio of ∼10 dB with focal spot diameters near 1–2 μm.

  12. Focused-ion-beam-assisted fabrication of polymer rolled-up microtubes

    Science.gov (United States)

    Luchnikov, V.; Stamm, M.; Akhmadaliev, Ch; Bischoff, L.; Schmidt, B.

    2006-08-01

    A focused ion beam (FIB) has been applied to the fabrication of polymer microtubes via the rolling-up technique from poly(4-vinyl pyridine)/polystyrene bilayer films deposited on the top of a sacrificial aluminum layer covering a silicon wafer. The bending forces in the film arise due to different swelling of the bilayer components in acidic water and lead to rolling of the film. The dimensions and position of the rolled-up tubes can be controlled by FIB milling (sputtering) of geometrically well-adjusted openings in the polymer films. This technique can be applied to the structuring of scrolled films formed from different materials without the use of lithographically patterned photoresists. The geometrical patterning of the tube interior can also be done by FIB irradiation.

  13. Acoustic radiation force on a double-layer microsphere by a Gaussian focused beam

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Rongrong; Cheng, Kaixuan; Liu, Jiehui; Mao, Yiwei; Gong, Xiufen [Key Laboratory of Modern Acoustics, Institute of Acoustics, Nanjing University, Nanjing 210093 (China); Liu, Xiaozhou, E-mail: xzliu@nju.edu.cn [Key Laboratory of Modern Acoustics, Institute of Acoustics, Nanjing University, Nanjing 210093 (China); State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190 (China)

    2014-10-14

    A new model for calculating the radiation force on double-layer microsphere is proposed based on the ray acoustics approach. The axial acoustic radiation force resulting from a focused Gaussian beam incident on spherical shells immersed in water is examined theoretically in relation to its thickness and the contents of its double-layer. The attenuation both in the water and inside the sphere is considered in this method, which cannot be ignored while the high frequency ultrasonic is used. Results of numerical calculations are presented for fat and low density polyethylene materials, with the hollow region filled with animal oil, water, or air. These results show how the acoustic impedance and the sound velocity of both layers, together with the thickness of the shell, affect the acoustic radiation force.

  14. Heavy charged particle radiobiology: using enhanced biological effectiveness and improved beam focusing to advance cancer therapy.

    Science.gov (United States)

    Allen, Christopher; Borak, Thomas B; Tsujii, Hirohiko; Nickoloff, Jac A

    2011-06-01

    Ionizing radiation causes many types of DNA damage, including base damage and single- and double-strand breaks. Photons, including X-rays and γ-rays, are the most widely used type of ionizing radiation in radiobiology experiments, and in radiation cancer therapy. Charged particles, including protons and carbon ions, are seeing increased use as an alternative therapeutic modality. Although the facilities needed to produce high energy charged particle beams are more costly than photon facilities, particle therapy has shown improved cancer survival rates, reflecting more highly focused dose distributions and more severe DNA damage to tumor cells. Despite early successes of charged particle radiotherapy, there is room for further improvement, and much remains to be learned about normal and cancer cell responses to charged particle radiation. PMID:21376738

  15. Dual focused coherent beams for three-dimensional optical trapping and continuous rotation of metallic nanostructures

    Science.gov (United States)

    Xu, Xiaohao; Cheng, Chang; Zhang, Yao; Lei, Hongxiang; Li, Baojun

    2016-07-01

    Metallic nanoparticles and nanowires are extremely important for nanoscience and nanotechnology. Techniques to optically trap and rotate metallic nanostructures can enable their potential applications. However, because of the destabilizing effects of optical radiation pressure, the optical trapping of large metallic particles in three dimensions is challenging. Additionally, the photothermal issues associated with optical rotation of metallic nanowires have far prevented their practical applications. Here, we utilize dual focused coherent beams to realize three-dimensional (3D) optical trapping of large silver particles. Continuous rotation of silver nanowires with frequencies measured in several hertz is also demonstrated based on interference-induced optical vortices with very low local light intensity. The experiments are interpreted by numerical simulations and calculations.

  16. Vlasov's kinetic theory of the collective charged particle beam transport through a magnetized plasma in the strongly nonlocal regime

    International Nuclear Information System (INIS)

    Plasma-based accelerator schemes represent the first step of the research-development of the future accelerator machines. Within the Vlasov's kinetic theory, describing the plasma wake field interaction, the collective transport of a warm non-laminar relativistic charged particle beam is analyzed in the strongly nonlocal regime, where the beam spot-size is much less than the plasma wavelength. This is done in the overdense regime, i.e., the beam density is much less than the plasma density. The beam is supposed to be sufficiently long to experience the adiabatic shielding by the plasma. In these conditions, we neglect the longitudinal beam dynamics and focus on the transverse one only. We derive the virial description (envelope description) from the 2D Vlasov-Poisson-type system of equations that governs the transverse self-consistent plasma wake field excitation. The resulting envelope equation is then reduced, in the aberration-less approximation, to a differential equation for the beam spot size, where the role of the ambient magnetic field is evaluated in both laboratory and astrophysical environments. An analysis of the beam envelope self-modulation is then carried out and the criteria for the occurrence of the instability are found. (authors)

  17. Magnetic fields and the technology challenges they pose to beam-based equipment: a semiconductor perspective

    Science.gov (United States)

    Esqueda, Vincent; Montoya, Julian A.

    2005-08-01

    As semiconductor devices shrink in size to accommodate faster processing speeds, the need for higher resolution beam-based metrology equipment and beam-based writing equipment will increase. The electron and ion beams used within these types of equipment are sensitive to very small variations in magnetic force applied to the beam. This phenomenon results from changes in Alternating Current (AC) and Direct Current (DC) magnetic flux density at the beam column which causes deflections of the beam that can impact equipment performance. Currently the most sensitive beam-based microscope manufacturers require an ambient magnetic field environment that does not have variations that exceed 0.2 milli-Gauss (mG). Studies have shown that such low levels of magnetic flux density can be extremely difficult to achieve. As examples, scissor lifts, vehicles, metal chairs, and doors moving in time and space under typical use conditions can create distortions in the Earth's magnetic field that can exceed 0.2 mG at the beam column. In addition it is known that changes in the Earth's magnetic field caused by solar flares, earthquakes, and variations in the Earth's core itself all cause changes in the magnetic field that can exceed 0.2 mG. This paper will provide the reader with the basic understanding of the emerging problem, will discuss the environmental and facility level challenges associated in meeting such stringent magnetic field environments, will discuss some of the mitigation techniques used to address the problem, and will close by discussing needs for further research in this area to assure semiconductor and nanotechnology industries are pre-positioned for even more stringent magnetic field environmental requirements.

  18. Efficient focusing of 8 keV X-rays with multilayer Fresnel zone plates fabricated by atomic layer deposition and focused ion beam milling

    OpenAIRE

    Mayer, Marcel; Keskinbora, Kahraman; Grévent, Corinne; Szeghalmi, Adriana; Knez, Mato; Weigand, Markus; Snigirev, Anatoly; Snigireva, Irina; Schütz, Gisela

    2013-01-01

    Fresnel zone plates (FZPs) recently showed significant improvement by focusing soft X-rays down to ∼10 nm. In contrast to soft X-rays, generally a very high aspect ratio FZP is needed for efficient focusing of hard X-rays. Therefore, FZPs had limited success in the hard X-ray range owing to difficulties of manufacturing high-aspect-ratio zone plates using conventional techniques. Here, employing a method of fabrication based on atomic layer deposition (ALD) and focused ion beam (FIB) milling,...

  19. Novel Hamiltonian method for collective dynamics analysis of an intense charged particle beam propagating through a periodic focusing quadrupole lattice

    International Nuclear Information System (INIS)

    Identifying regimes for quiescent propagation of intense beams over long distances has been a major challenge in accelerator research. In particular, the development of systematic theoretical approaches that are able to treat self-consistently the applied oscillating force and the nonlinear self-field force of the beam particles simultaneously has been a major challenge of modern beam physics. In this paper, the recently developed Hamiltonian averaging technique [E. A. Startsev, R. C. Davidson, and M. Dorf, Phys. Rev. ST Accel. Beams 13, 064402 (2010)] which incorporates both the applied periodic focusing force and the self-field force of the beam particles, is generalized to the case of time-dependent beam distributions. The new formulation allows not only a determination of quasi-equilibrium solutions of the non-linear Vlasov-Poison system of equations but also a detailed study of their stability properties. The corrections to the well-known ''smooth-focusing'' approximation are derived, and the results are applied to a matched beam with thermal equilibrium distribution function. It is shown that the corrections remain small even for moderate values of the vacuum phase advance συ. Nonetheless, because the corrections to the average self-field potential are non-axisymmetric, the stability properties of the different beam quasi-equilibria can change significantly.

  20. Phase and group velocity of focused, pulsed Gaussian beams in the presence and absence of primary aberrations

    International Nuclear Information System (INIS)

    This work presents a study on the phase- and group-velocity variations of focused, pulsed Gaussian beams during the propagation through the focal region along the optical axis. In the aberration-free case, it is discussed how the wavelength dependence of beam properties alters the group velocity, and how a chromatic aberration-like effect can arise even when focusing is performed with an element that does not have chromatic aberration. It is also examined what effects primary spherical aberration, astigmatism, coma, curvature of field and distortion, along with chromatic aberration, have on the phase- and group-velocity changes occurring during propagation through focus. (paper)

  1. Multichannel analyzer of energy spectra of a magnetized relativistic electron beam

    International Nuclear Information System (INIS)

    A description of a magnetic step-analyser of intense relativistic electron beam energy spectra is presented. The azimuthal magnetic field in the analyser is created by the current flowing through two coaxial cylinders. The particles move in the analyser along the trajectories, representing spirals with the pitch depending on the energy and rolled on the magnetic field spiral force lines. The magnetic analyser serviceability is demonstrated at the U-1 device with 1.1 MeV electron beam energy and 50 kA current. 6 refs.; 7 figs.; 2 tabs

  2. Design of the magnetic field system for Beijing intense slow positron beam transportation

    International Nuclear Information System (INIS)

    A slow positron beam with intensity of 106 e+/s produced by the Beijing Electron-Positron Collider (BEPC) is transported by the 100 Gauss magnetic field system with the oscillation less that 10%. In this paper, the distributions of magnetic field at target chamber, sample chamber and Penning-Trap storage are calculated systematically, and the parameters of solenoidal coils and steering coils are calculated respectively. The correction coils are designed to compensate the affect induced by the geomagnetic field and the bent tube. Results of electron beam experiment show that the positron beams are transported to sample chamber with the beam spot size basically unchanged, and the magnetic field distributions satisfy to the requirement of the slow positron beam system

  3. Magnet lattice design of the SSRF electron-beam transfer lines

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Under three-dimensional plane geometrical constraints (X,Y,θ), with two asymmetric achromatic sections,the combined three-section structural FODO-like magnet lattice design is adopted and finely optimized in the SSRF electron-beam transfer lines. The magnet lattice has high flexibility and robustness, and the Courant-Snyder parameters can be easily adjusted within a wide range to meet the requirements of transmission and injection for different operation modes of the linear accelerator, booster synchrotron, and storage ring. In this article, the main parameters of the linear optics design of the SSRF electron-beam transfer lines are described, involving the physical design criteria, the total geometrical layout, the magnet lattice, and the beam Courant-Snyder parameters matching. The studies of the variant beam dynamic simulation program calculations show that the design purpose of the efficient beam transmission and injection will be basically achieved.

  4. Spatial chemistry evolution during focused electron beam-induced deposition: origins and workarounds

    International Nuclear Information System (INIS)

    The successful application of functional nanostructures, fabricated via focused electron-beam-induced deposition (FEBID), is known to depend crucially on its chemistry as FEBID tends to strong incorporation of carbon. Hence, it is essential to understand the underlying mechanisms which finally determine the elemental composition after fabrication. In this study we focus on these processes from a fundamental point of view by means of (1) varying electron emission on the deposit surface; and (2) changing replenishment mechanism, both driven by the growing deposit itself. First, we revisit previous results concerning chemical variations in nanopillars (with a quasi-1D footprint) depending on the process parameters. In a second step we expand the investigations to deposits with a 3D footprint which are more relevant in the context of applications. Then, we demonstrate how technical setups and directional gas fluxes influence final chemistries. Finally, we put the findings in a bigger context with respect to functionalities which demonstrates the crucial importance of carefully set up fabrication processes to achieve controllable, predictable and reproducible chemistries for FEBID deposits as a key element for industrially oriented applications. (orig.)

  5. Nano-Tomography of Porous Geological Materials Using Focused Ion Beam-Scanning Electron Microscopy

    Directory of Open Access Journals (Sweden)

    Yang Liu

    2016-10-01

    Full Text Available Tomographic analysis using focused ion beam-scanning electron microscopy (FIB-SEM provides three-dimensional information about solid materials with a resolution of a few nanometres and thus bridges the gap between X-ray and transmission electron microscopic tomography techniques. This contribution serves as an introduction and overview of FIB-SEM tomography applied to porous materials. Using two different porous Earth materials, a diatomite specimen, and an experimentally produced amorphous silica layer on olivine, we discuss the experimental setup of FIB-SEM tomography. We then focus on image processing procedures, including image alignment, correction, and segmentation to finally result in a three-dimensional, quantified pore network representation of the two example materials. To each image processing step we consider potential issues, such as imaging the back of pore walls, and the generation of image artefacts through the application of processing algorithms. We conclude that there is no single image processing recipe; processing steps need to be decided on a case-by-case study.

  6. Measuring the electron beam energy in a magnetic bunch compressor

    International Nuclear Information System (INIS)

    Within this thesis, work was carried out in and around the first bunch compressor chicane of the FLASH (Free-electron LASer in Hamburg) linear accelerator in which two distinct systems were developed for the measurement of an electron beams' position with sub-5 μm precision over a 10 cm range. One of these two systems utilized RF techniques to measure the difference between the arrival-times of two broadband electrical pulses generated by the passage of the electron beam adjacent to a pickup antenna. The other system measured the arrival-times of the pulses from the pickup with an optical technique dependent on the delivery of laser pulses which are synchronized to the RF reference of the machine. The relative advantages and disadvantages of these two techniques are explored and compared to other available approaches to measure the same beam property, including a time-of-flight measurement with two beam arrival-time monitors and a synchrotron light monitor with two photomultiplier tubes. The electron beam position measurement is required as part of a measurement of the electron beam energy and could be used in an intra-bunch-train beam-based feedback system that would stabilize the amplitude of the accelerating field. By stabilizing the accelerating field amplitude, the arrival-time of the electron beam can be made more stable. By stabilizing the electron beam arrival-time relative to a stable reference, diagnostic, seeding, and beam-manipulation lasers can be synchronized to the beam. (orig.)

  7. Perturbed angular correlations for Gd in gadolinium: in-beam comparisons of relative magnetizations

    OpenAIRE

    Stuchbery, A. E.; Wilson, A. N.; Davidson, P. M.; Benczer-Koller, N.

    2006-01-01

    Perturbed angular correlations were measured for Gd ions implanted into gadolinium foils following Coulomb excitation with 40 MeV O-16 beams. A technique for measuring the relative magnetizations of ferromagnetic gadolinium hosts under in-beam conditions is described and discussed. The combined electric-quadrupole and magnetic-dipole interaction is evaluated. The effect of nuclei implanted onto damaged or non-substitutional sites is assessed, as is the effect of misalignment between the inter...

  8. Self-focusing of an ultra-intense short pulse laser beam in a tunnel-ionized plasma

    International Nuclear Information System (INIS)

    Tunnel-ionized plasma evolve on a time scale shorter than the duration of an ultra-intense short-pulse laser beam propagating through matter. Self-focusing of a linearly polarized laser beam with a parabolic intensity distribution in a tunnel-ionized plasma produced during its propagation through a gas is studied under the paraxial ray approximation. The Laplacian term of the electric field in the electromagnetic wave equation has been evaluated using two approaches, one leading to the more accurate expression for the beam-width parameter f and the other leading to the less accurate expressions for f. Analyzing these expressions along with that reported in the literature for a Gaussian laser beam it is observed that the expressions obtained in this paper predict the increasing axial intensity with the distance of propagation (self-focusing) in contrast to the result (self-defocusing) predicted from the earlier reported expression. (author)

  9. Polymer gel dosimetry of an electron beam in the presence of a magnetic field

    Science.gov (United States)

    Vandecasteele, J.; De Deene, Y.

    2013-06-01

    The effect of a strong external magnetic field on 4 MeV electron beam was measured with polymer gel dosimetry. The measured entrance dose distribution was compared with a calculated fluence map. The magnetic field was created by use of two permanent Neodymium (NdFeB) magnets that were positioned perpendicular to the electron beam. The magnetic field between the magnets was measured with Hall sensors. Based on the magnetic field measurement and the law of Biot-Savart, the magnetic field distribution was extrapolated. Electron trajectories were calculated using a relativistic Lorentz force operator. Although the simplified computational model that was applied, the shape and position of the calculated entrance fluence map are found to be in good agreement with the measured dose distribution in the first layer of the phantom. In combination with the development of low density polymer gel dosimeters, these preliminary results show the potential of 3D gel dosimetry in MRI-linac applications.

  10. DEPENDENCE OF DAMPING CHARACTERISTICS OF A BEAM WITH DAMPING RUBBER MAGNETIC POWDER ON RUBBER PROPERTY

    Institute of Scientific and Technical Information of China (English)

    Ming Li; Zeng He; Huiming Zheng; Ning Zhang

    2008-01-01

    A cantilever beam with Damping Material Applying Rubber Magnetic Powder (DRM)has been investigated.Two methods are selected to hold DRM to a vibrating steel beam,one is to attach DRM by the magnetic attractive force (called DRM beam) and the other by adhesive bonding (called AB-DRM beam).Different from the damping property of AB-DRM beam caused by shear deformation of damping material,the damping property of DRM beam is characterized by the sliding frictional loss together with the internal loss of damping material.The authors established a formulation to predict the damping characteristics of DRM beam,which was validated experimentally.It is found that rubber material loss factor/β has a decisive influence on damping improvement of DRM beam versus AB-DRM beam.If/β is smaller than the critical value around 0.8255,a valid range of vibratory amplitude always exists in which DRM beam can achieve better damping than AB-DRM beam;conversely,if/β is bigger than the critical value,the valid range does not exist when slide occurs.Such results are used to determine the merits and limitations of DRM and develop design guidelines.

  11. Focused Ion Beam Fabrication of Silicon-On Field-Effect Transistors.

    Science.gov (United States)

    Mattiussi, Greg Andrew

    N-channel metal-oxide-semiconductor field-effect transistors (MOSFET's) have been fabricated on silicon -on-insulator (SOI) substrates using a Focused Ion Beam (FIB) to pattern the gate and to dope the source and drains. Lightly -doped source (LDS) structures were implemented with the FIB to increase the drain-to-source voltage at which single transistor latch-up occurred. FIB exposure of two electron-beam resists was investigated for lithography of the transistor gate and the device mesas. Vertical resist profiles were achieved for linewidths down to 0.2 μm in width in the case of the negative-tone SAL-601 resist from Shipley Co. Openings in resist as narrow as 0.35 μm were made using the positive-tone P28 resist from OCG Microelectronic Materials. Optimal doses, pre- and post-exposure processing conditions were determined for both resists. Transistors with LDS structures showed higher latching voltages than those without. The magnitude of the increase in latching voltage due to the LDS was a function of body doping level, SOI thickness, and coded gate length. The largest increase was 5.1 V for a 0.8 μm MOSFET fabricated in a 125 nm thick SOI film with a body implant dose of 5.6times10^ {12} B cm^{-2}. Devices fabricated in SOI films of thickness 250 nm showed smaller increases in latching voltage with the LDS than those in 125 nm SOI films.

  12. Focused tight dressing does not prevent cochlear implant magnet migration under 1.5 Tesla MRI

    OpenAIRE

    CUDA, D.; A. MURRI; Succo, G.

    2013-01-01

    SUMMARY We report a retrospective case of inner magnet migration, which occurred after 1.5 Tesla MRI scanning in an adult recipient of a bilateral cochlear implant (CI) despite a focused head dressing. The patient, bilaterally implanted with Nucleus 5 CIs (Cochlear LTD, Sydney, Australia), underwent a 1.5 Tesla cholangio-MRI scan for biliary duct pathology. In subsequent days, a focal skin alteration appeared over the left inner coil. Plain skull radiographs showed partial magnet migration on...

  13. Self-focusing induced reduction of Stimulated Brillouin Scattering for the case of monospeckle laser beams interacting with a plasma

    Science.gov (United States)

    Masson-Laborde, Paul-Edouard; Hueller, Stefan; Pesme, Denis; Loiseau, Pascal; Labaune, Christine; Bandulet, Heidi

    2008-11-01

    The mechanism explaining the low level of Stimulated Brillouin Scattering observed in laser-plasma experiments with monospeckle laser beams, carried out at the LULI facility, is studied by means of numerical simulations. For the regime where the beam power is well above the self-focusing critical power, simulations carried out with the codes Harmony2D and HERA-ILP (in 2D and 3D geometry respectively), show time-averaged reflectivities of the order of only a few percent. Because of self-focusing and the filament resonant instability, SBS takes only place in self-focused hot spots located in the low-density front part of the plasma. The shortened hot spot sizes and the steepened flow-profile dramatically reduce SBS. This scenario may also applies to the most intense laser hot spots in a spatially smoothed laser beam.

  14. Design and end chamfer simulation of PEFP beam line curved dipole magnets%Design and end chamfer simulation of PEFP beam line curved dipole magnets

    Institute of Scientific and Technical Information of China (English)

    朱应顺; 杨梅; 张卓; 陈宛; 尹宝贵; 石才土; 康文

    2011-01-01

    The design, fabrication and field measurement of 11 DC curved dipole magnets for the PEFP Beam Line have been completed. In this paper, a design method for a complex end chamfer using OPERA-3D is proposed. The conventional method for estimating chamfer sh

  15. Cryogenic Beam Loss Monitors for the Superconducting Magnets of the LHC

    CERN Document Server

    Bartosik, MR; Sapinski, M; Kurfuerst, C; Griesmayer, E; Eremin, V; Verbitskaya, E

    2014-01-01

    The Beam Loss Monitor detectors close to the interaction points of the Large Hadron Collider are currently located outside the cryostat, far from the superconducting coils of the magnets. In addition to their sensitivity to lost beam particles, they also detect particles coming from the experimental collisions, which do not contribute significantly to the heat deposition in the superconducting coils. In the future, with beams of higher energy and brightness resulting in higher luminosity, distinguishing between these interaction products and dangerous quench-provoking beam losses from the primary proton beams will be challenging. The system can be optimised by locating beam loss monitors as close as possible to the superconducting coils, inside the cold mass in a superfluid helium environment, at 1.9 K. The dose then measured by such Cryogenic Beam Loss Monitors would more precisely correspond to the real dose deposited in the coil. The candidates under investigation for such detectors are based on p+-n-n+ si...

  16. Measuring the electron beam energy in a magnetic bunch compressor

    Energy Technology Data Exchange (ETDEWEB)

    Hacker, Kirsten

    2010-09-15

    Within this thesis, work was carried out in and around the first bunch compressor chicane of the FLASH (Free-electron LASer in Hamburg) linear accelerator in which two distinct systems were developed for the measurement of an electron beams' position with sub-5 {mu}m precision over a 10 cm range. One of these two systems utilized RF techniques to measure the difference between the arrival-times of two broadband electrical pulses generated by the passage of the electron beam adjacent to a pickup antenna. The other system measured the arrival-times of the pulses from the pickup with an optical technique dependent on the delivery of laser pulses which are synchronized to the RF reference of the machine. The relative advantages and disadvantages of these two techniques are explored and compared to other available approaches to measure the same beam property, including a time-of-flight measurement with two beam arrival-time monitors and a synchrotron light monitor with two photomultiplier tubes. The electron beam position measurement is required as part of a measurement of the electron beam energy and could be used in an intra-bunch-train beam-based feedback system that would stabilize the amplitude of the accelerating field. By stabilizing the accelerating field amplitude, the arrival-time of the electron beam can be made more stable. By stabilizing the electron beam arrival-time relative to a stable reference, diagnostic, seeding, and beam-manipulation lasers can be synchronized to the beam. (orig.)

  17. Electron beam fabrication and characterization of high- resolution magnetic force microscopy tips

    NARCIS (Netherlands)

    Rührig, M.; Porthun, S.; Lodder, J.C.; McVitie, S.; Heyderman, L.J.; Johnston, A.B.; Chapman, J.N.

    1996-01-01

    The stray field, magnetic microstructure, and switching behavior of high‐resolution electron beam fabricated thin film tips for magnetic force microscopy (MFM) are investigated with different imaging modes in a transmission electron microscope (TEM). As the tiny smooth carbon needles covered with a

  18. Effect of focused ion beam deposition induced contamination on the transport properties of nano devices

    International Nuclear Information System (INIS)

    Focused ion beam (FIB) deposition produces unwanted particle contamination beyond the deposition point. This is due to the FIB having a Gaussian distribution. This work investigates the spatial extent of this contamination and its influence on the electrical properties of nano-electronic devices. A correlation study is performed on carbon-nanotube (CNT) devices manufactured using FIB deposition. The devices are observed using transmission electron microscopy (TEM) and these images are correlated with device electrical characteristics. To discover how far Pt-nanoparticle contamination occurs along a CNT after FIB electrical contact deposition careful TEM inspections are performed. The results show FIB deposition efficiently improves electrical contact; however, the practice is accompanied by serious particle contamination near deposition points. These contaminants include metal particles and amorphous elements originating from precursor gases and residual water molecules in the vacuum chamber. Pt-contamination extends for approximately 2 μm from the point of FIB contact deposition. These contaminants cause current fluctuations and alter the transport characteristics of devices. It is recommended that nano-device fabrication occurs at a distance greater than 2 μm from the FIB deposition of an electrical contact. (paper)

  19. Focused ion beam fabrication and IBIC characterization of a diamond detector with buried electrodes

    CERN Document Server

    Olivero, P; Jaksic, M; Pastuovic, Z; Picollo, F; Skukan, N; Vittone, E

    2016-01-01

    This paper reports on the fabrication and characterization of a high purity monocrystalline diamond detector with buried electrodes realized by the selective damage induced by a focused 6 MeV carbon ion beam scanned over a pattern defined at the micrometric scale. A suitable variable-thickness mask was deposited on the diamond surface in order to modulate the penetration depth of the ions and to shallow the damage profile toward the surface. After the irradiation, the sample was annealed at high temperature in order to promote the conversion to the graphitic phase of the end-of-range regions which experienced an ion-induced damage exceeding the damage threshold, while recovering the sub-threshold damaged regions to the highly resistive diamond phase. This process provided conductive graphitic electrodes embedded in the insulating diamond matrix; the presence of the variable-thickness mask made the terminations of the channels emerging at the diamond surface and available to be connected to an external electro...

  20. Thermal conductivity and nanocrystalline structure of platinum deposited by focused ion beam

    KAUST Repository

    Alaie, Seyedhamidreza

    2015-02-04

    Pt deposited by focused ion beam (FIB) is a common material used for attachment of nanosamples, repair of integrated circuits, and synthesis of nanostructures. Despite its common use little information is available on its thermal properties. In this work, Pt deposited by FIB is characterized thermally, structurally, and chemically. Its thermal conductivity is found to be substantially lower than the bulk value of Pt, 7.2 W m-1 K-1 versus 71.6 W m-1 K-1 at room temperature. The low thermal conductivity is attributed to the nanostructure of the material and its chemical composition. Pt deposited by FIB is shown, via aberration corrected TEM, to be a segregated mix of nanocrystalline Pt and amorphous C with Ga and O impurities. Ga impurities mainly reside in the Pt while O is homogeneously distributed throughout. The Ga impurity, small grain size of the Pt, and the amorphous carbon between grains are the cause for the low thermal conductivity of this material. Since Pt deposited by FIB is a common material for affixing samples, this information can be used to assess systematic errors in thermal characterization of different nanosamples. This application is also demonstrated by thermal characterization of two carbon nanofibers and a correction using the reported thermal properties of the Pt deposited by FIB.