The Experts below are selected from a list of 7452 Experts worldwide ranked by ideXlab platform
J C Fernandez - One of the best experts on this subject based on the ideXlab platform.
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efficient quasi monoenergetic Ion beams from laser driven relativistic plasmas
Nature Communications, 2015Co-Authors: Sasi Palaniyappan, Christopher E Hamilton, Adam B. Sefkow, D. C. Gautier, Christian Kreuzer, Miguel A. Santiago, R. C. Shah, C Huang, J C FernandezAbstract:Table-top laser-plasma Ion Accelerators have many potential applicatIons, but achieving simultaneous narrow energy spread and high efficiency remains a challenge. Here, the authors produce Ion beams with up to 18 MeV per nucleon whilst keeping the energy spread reduced through a self-organized process.
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efficient quasi monoenergetic Ion beams from laser driven relativistic plasmas
Nature Communications, 2015Co-Authors: Sasi Palaniyappan, Christopher E Hamilton, Adam B. Sefkow, D. C. Gautier, Christian Kreuzer, Miguel A. Santiago, R. C. Shah, C Huang, J C FernandezAbstract:Table-top laser-plasma Ion Accelerators have many exciting applicatIons, many of which require Ion beams with simultaneous narrow energy spread and high conversIon efficiency. However, achieving these requirements has been elusive. Here we report the experimental demonstratIon of laser-driven Ion beams with narrow energy spread and energies up to 18 MeV per nucleon and ∼5% conversIon efficiency (that is 4 J out of 80-J laser). Using computer simulatIons we identify a self-organizing scheme that reduces the Ion energy spread after the laser exits the plasma through persisting self-generated plasma electric (∼10(12) V m(-1)) and magnetic (∼10(4) T) fields. These results contribute to the development of next generatIon compact Accelerators suitable for many applicatIons such as isochoric heating for Ion-fast ignitIon and producing warm dense matter for basic science.
Sasi Palaniyappan - One of the best experts on this subject based on the ideXlab platform.
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efficient quasi monoenergetic Ion beams from laser driven relativistic plasmas
Nature Communications, 2015Co-Authors: Sasi Palaniyappan, Christopher E Hamilton, Adam B. Sefkow, D. C. Gautier, Christian Kreuzer, Miguel A. Santiago, R. C. Shah, C Huang, J C FernandezAbstract:Table-top laser-plasma Ion Accelerators have many potential applicatIons, but achieving simultaneous narrow energy spread and high efficiency remains a challenge. Here, the authors produce Ion beams with up to 18 MeV per nucleon whilst keeping the energy spread reduced through a self-organized process.
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efficient quasi monoenergetic Ion beams from laser driven relativistic plasmas
Nature Communications, 2015Co-Authors: Sasi Palaniyappan, Christopher E Hamilton, Adam B. Sefkow, D. C. Gautier, Christian Kreuzer, Miguel A. Santiago, R. C. Shah, C Huang, J C FernandezAbstract:Table-top laser-plasma Ion Accelerators have many exciting applicatIons, many of which require Ion beams with simultaneous narrow energy spread and high conversIon efficiency. However, achieving these requirements has been elusive. Here we report the experimental demonstratIon of laser-driven Ion beams with narrow energy spread and energies up to 18 MeV per nucleon and ∼5% conversIon efficiency (that is 4 J out of 80-J laser). Using computer simulatIons we identify a self-organizing scheme that reduces the Ion energy spread after the laser exits the plasma through persisting self-generated plasma electric (∼10(12) V m(-1)) and magnetic (∼10(4) T) fields. These results contribute to the development of next generatIon compact Accelerators suitable for many applicatIons such as isochoric heating for Ion-fast ignitIon and producing warm dense matter for basic science.
B Voss - One of the best experts on this subject based on the ideXlab platform.
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broadband electronics for cvd diamond detectors
Diamond and Related Materials, 2001Co-Authors: P Moritz, E Berdermann, K Blasche, H Stelzer, B VossAbstract:The applicatIon of CVD-diamond detectors for particle detectIon has created a demand for the development of very fast, low-noise electronics operated at high dc bias voltages. To take advantage of the high charge-carrier mobility of the new detector material the signal processing is performed using microwave layout techniques as well as picosecond pulse shapers and GHz-frequency dividers. The particle detectIon limits of CVD-diamond detectors processed with low impedance broadband electronics are described. The properties of the developed electronics are discussed in conjunctIon with results from beam diagnostics operatIon in the broad energy range of 120 keV/amu up to 2 GeV/amu for GSIs heavy Ion Accelerators.
R. H. Cohen - One of the best experts on this subject based on the ideXlab platform.
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simulating electron clouds in high current Ion Accelerators with solenoid focusing
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2007Co-Authors: W M Sharp, R. H. Cohen, A. Friedman, J L Vay, P A Seidl, D P Grote, P K Roy, J E Coleman, Julien Armijo, I HaberAbstract:ContaminatIon from electrons is a concern for the solenoid-focused Ion Accelerators being developed for experiments in high-energy density physics (HEDP). These electrons are produced directly by beam Ions hitting lattice elements and intercepting diagnostics, or indirectly by IonizatIon of desorbed neutral gas, and they are believed responsible for time dependence of the beam radius, emittance, and focal distance seen on the solenoid transport experiment (STX) at Lawrence Berkeley NatIonal Laboratory. The electrostatic particle-in-cell code WARP has been upgraded to include the physics needed to simulate electron-cloud phenomena. We present preliminary self-consistent simulatIons of STX experiments suggesting that the observed time dependence of the beam stems from a complicated interactIon of beam Ions, desorbed neutrals, and electrons.
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simulating electron clouds in high current Ion Accelerators with solenoid focusing
Lawrence Berkeley National Laboratory, 2006Co-Authors: W M Sharp, R. H. Cohen, A. Friedman, J L Vay, P A Seidl, D P Grote, P K Roy, J E Coleman, Julien Armijo, I HaberAbstract:HIFAN 1539 LBNL-61683 Simulating Electron Clouds in High-Current Ion Accelerators with Solenoid Focusing* W. M. Sharp, D. P. Grote, R. H. Cohen, A. Friedman Lawrence Livermore NatIonal Laboratory J.-L. Vay, P. A. Seidl, P. K. Roy, J. E. Coleman, J. Armijo Lawrence Berkeley NatIonal Laboratory I. Haber University of Maryland, College Park abstract ContaminatIon from electrons is a concern for the solenoid-focused Ion Accelerators being developed for experiments in high- energy-density physics (HEDP). These electrons are produced directly by beam Ions hitting lattice elements and intercepting disgnostics, or indirectly by IonizatIon of desorbed neutral gas, and they are believed responsible for time dependence of the beam radius, emittance, and focal distance seen on the Solenoid Transport Experiment (STX) at Lawrence Berkeley NatIonal Laboratory. The electrostatic particle-in-cell code WARP has been upgraded to included the physics needed to simulate electron-cloud phenomena. We present preliminary self-consistent simulatIons of STX experiments suggesting that the observed time dependence of the beam stems from a complicated interactIon of beam Ions, desorbed neutrals, and electrons. 1. IntroductIon The Solenoid Transport Experiment (STX) is a scaled experiment to study emittance and envelope characteristics of a space-charge-dominated Ion beam confined transversely by solenoids [1]. An important aspect of this project is determining how the beam transverse emittance and envelope parameters evolve during solenoid transport, and how these parameters are affected by stray electrons in the system. The expectatIon is that a comparison of STX results with findings from the High-Current Experiment (HCX) will guide the choice of the transport lattice for projected experiments in High-Energy Density Physics (HEDP) and Heavy-Ion FusIon (HIF). The STX is presently undergoing commissIoning, with two of the planned four solenoids being tested. The remaining solenoids will be added during the remainder of FY2006. The two-solenoid layout consists of a 300 kV diode producing a K + beam with a 0.3 mm-mrad emittance, a pair of 2.5-T solenoids, each 51.1 cm in length and separated by 8.9 cm, and last, a box with intercepting diagnostics to characterize the beam. Negatively biased rings or “traps” are situated at both ends of the solenoids to restrict electron movement toward the source, and an aperture plate may be inserted midway along the upstream trap to reduce beam current by about half. To date, the beam has been characterized by placing the diagnostics box in three locatIons: (1) immediately after the aperture and first electron trap, without the solenoids in place, (2) immediately after the second solenoid, with the second electron trap placed partly inside the last solenoid, and (3) 29 cm beyond the last solenoid. CharacterizatIon of the beam in the first configuratIon, without solenoids and with a 1-cm-radius aperture plate in place, shows a 25 mA flattop of the beam that continues for about 10 µs, and slit-plate scans verify that the transverse emittance is about 14 mm-mrad. With the aperture removed, the current is 45 mA, and the emittance, 22 mm-mrad. A diagnostic measurement that is used repeatedly in the work reported here is the current from the final electron trap to ground through a 50-Ω resistor when a slit plate intercepts the beam 5-10 mm beyond the trap. The trap current in the case without solenoids is exactly what is expected. There is an initial positive current pulse of about 50 mA, balancing the image charge as the beam head enters the electron trap, followed by a gradually increasing positive current and finally a second capacitive pulse as the beam tail leaves the trap. The
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experiments studying desorbed gas and electron clouds in Ion Accelerators
Proceedings of the 2005 Particle Accelerator Conference, 2005Co-Authors: A W Molvik, R. H. Cohen, A. Friedman, F.m. Bieniosek, P A Seidl, S M Lund, M K Covo, J J Barnard, D Baca, J L VayAbstract:Electron clouds and gas pressure rise limit the performance of many major accelerator rings. We are studying these issues experimentally with ∼ 1 MeV heavy-Ion beams, coordinated with significant efforts in self-consistent simulatIon and theory. The experiments use multiple diagnostics, within and between quadrupole magnets, to measure the sources and accumulatIon of electrons and gas. In support of these studies, we have measured gas desorptIon and electron emissIon coefficients for potassium Ions impinging on stainless steel targets at angles near grazing incidence. Our goal is to measure the electron particle balance for each source – IonizatIon of gas, emissIon from beam tubes, and emissIon from an end wall – determine the electron effects on the Ion beam and apply the increased understanding to mitigatIon. We describe progress towards that goal.
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simulating electron clouds in heavy Ion Accelerators
Physics of Plasmas, 2005Co-Authors: R. H. Cohen, A. Friedman, F.m. Bieniosek, J L Vay, P A Seidl, Kireeff M Covo, A W Molvik, Peter Stoltz, S M Lund, Seth VeitzerAbstract:Contaminating clouds of electrons are a concern for most Accelerators of positively charged particles, but there are some unique aspects of heavy-Ion Accelerators for fusIon and high-energy density physics which make modeling such clouds especially challenging. In particular, self-consistent electron and Ion simulatIon is required, including a particle advance scheme which can follow electrons in regIons where electrons are strongly magnetized, weakly magnetized, and unmagnetized. The approach to such self-consistency is described, and in particular a scheme for interpolating between full-orbit (Boris) and drift-kinetic particle pushes that enables electron time steps long compared to the typical gyroperiod in the magnets. Tests and applicatIons are presented: simulatIon of electron clouds produced by three different kinds of sources indicates the sensitivity of the cloud shape to the nature of the source; first-of-a-kind self-consistent simulatIon of electron-cloud experiments on the high-current experim...
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electron cloud simulatIon and theory for high current heavy Ion beams
Physical Review Special Topics-accelerators and Beams, 2004Co-Authors: R. H. Cohen, A. Friedman, J L Vay, A W Molvik, Peter Stoltz, S M Lund, E P Lee, T Azevedo, Seth VeitzerAbstract:Stray electrons can arise in positive-Ion Accelerators for heavy-Ion fusIon or other applicatIons as a result of IonizatIon of ambient gas or gas released from walls due to halo-Ion impact, or as a result of secondary-electron emissIon. We summarize the distinguishing features of electron-cloud issues in heavy-Ion-fusIon Accelerators and a plan for developing a self-consistent simulatIon capability for heavy-Ion beams and electron clouds (also applicable to other Accelerators). We also present results from several ingredients in this capability. (1) We calculate the electron cloud produced by electron desorptIon from computed beam-Ion loss, which illustrates the importance of retaining Ion reflectIon at the walls. (2) We simulate the effect of specified electron-cloud distributIons on Ion beam dynamics. We consider here electron distributIons with axially varying density, centroid locatIon, or radial shape, and examine both random and sinusoidally varying perturbatIons. We find that amplitude variatIons are most effective in spoiling Ion beam quality, though for sinusoidal variatIons which match the natural Ion beam centroid oscillatIon or breathing-mode frequencies, the centroid and shape perturbatIons can also have significant impact. We identify an instability associated with a resonance between the beam-envelope ``breathing'' mode and the electron perturbatIon. We estimate its growth rate, which is moderate (compared to the reciprocal of a typical pulse duratIon). One conclusIon from this study is that heavy-Ion beams are surprisingly robust to electron clouds, compared to a priori expectatIons. (3) We report first results from a long-time-step algorithm for electron dynamics, which holds promise for efficient simultaneous solutIon of electron and Ion dynamics.
A. Friedman - One of the best experts on this subject based on the ideXlab platform.
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simulating electron clouds in high current Ion Accelerators with solenoid focusing
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2007Co-Authors: W M Sharp, R. H. Cohen, A. Friedman, J L Vay, P A Seidl, D P Grote, P K Roy, J E Coleman, Julien Armijo, I HaberAbstract:ContaminatIon from electrons is a concern for the solenoid-focused Ion Accelerators being developed for experiments in high-energy density physics (HEDP). These electrons are produced directly by beam Ions hitting lattice elements and intercepting diagnostics, or indirectly by IonizatIon of desorbed neutral gas, and they are believed responsible for time dependence of the beam radius, emittance, and focal distance seen on the solenoid transport experiment (STX) at Lawrence Berkeley NatIonal Laboratory. The electrostatic particle-in-cell code WARP has been upgraded to include the physics needed to simulate electron-cloud phenomena. We present preliminary self-consistent simulatIons of STX experiments suggesting that the observed time dependence of the beam stems from a complicated interactIon of beam Ions, desorbed neutrals, and electrons.
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simulating electron clouds in high current Ion Accelerators with solenoid focusing
Lawrence Berkeley National Laboratory, 2006Co-Authors: W M Sharp, R. H. Cohen, A. Friedman, J L Vay, P A Seidl, D P Grote, P K Roy, J E Coleman, Julien Armijo, I HaberAbstract:HIFAN 1539 LBNL-61683 Simulating Electron Clouds in High-Current Ion Accelerators with Solenoid Focusing* W. M. Sharp, D. P. Grote, R. H. Cohen, A. Friedman Lawrence Livermore NatIonal Laboratory J.-L. Vay, P. A. Seidl, P. K. Roy, J. E. Coleman, J. Armijo Lawrence Berkeley NatIonal Laboratory I. Haber University of Maryland, College Park abstract ContaminatIon from electrons is a concern for the solenoid-focused Ion Accelerators being developed for experiments in high- energy-density physics (HEDP). These electrons are produced directly by beam Ions hitting lattice elements and intercepting disgnostics, or indirectly by IonizatIon of desorbed neutral gas, and they are believed responsible for time dependence of the beam radius, emittance, and focal distance seen on the Solenoid Transport Experiment (STX) at Lawrence Berkeley NatIonal Laboratory. The electrostatic particle-in-cell code WARP has been upgraded to included the physics needed to simulate electron-cloud phenomena. We present preliminary self-consistent simulatIons of STX experiments suggesting that the observed time dependence of the beam stems from a complicated interactIon of beam Ions, desorbed neutrals, and electrons. 1. IntroductIon The Solenoid Transport Experiment (STX) is a scaled experiment to study emittance and envelope characteristics of a space-charge-dominated Ion beam confined transversely by solenoids [1]. An important aspect of this project is determining how the beam transverse emittance and envelope parameters evolve during solenoid transport, and how these parameters are affected by stray electrons in the system. The expectatIon is that a comparison of STX results with findings from the High-Current Experiment (HCX) will guide the choice of the transport lattice for projected experiments in High-Energy Density Physics (HEDP) and Heavy-Ion FusIon (HIF). The STX is presently undergoing commissIoning, with two of the planned four solenoids being tested. The remaining solenoids will be added during the remainder of FY2006. The two-solenoid layout consists of a 300 kV diode producing a K + beam with a 0.3 mm-mrad emittance, a pair of 2.5-T solenoids, each 51.1 cm in length and separated by 8.9 cm, and last, a box with intercepting diagnostics to characterize the beam. Negatively biased rings or “traps” are situated at both ends of the solenoids to restrict electron movement toward the source, and an aperture plate may be inserted midway along the upstream trap to reduce beam current by about half. To date, the beam has been characterized by placing the diagnostics box in three locatIons: (1) immediately after the aperture and first electron trap, without the solenoids in place, (2) immediately after the second solenoid, with the second electron trap placed partly inside the last solenoid, and (3) 29 cm beyond the last solenoid. CharacterizatIon of the beam in the first configuratIon, without solenoids and with a 1-cm-radius aperture plate in place, shows a 25 mA flattop of the beam that continues for about 10 µs, and slit-plate scans verify that the transverse emittance is about 14 mm-mrad. With the aperture removed, the current is 45 mA, and the emittance, 22 mm-mrad. A diagnostic measurement that is used repeatedly in the work reported here is the current from the final electron trap to ground through a 50-Ω resistor when a slit plate intercepts the beam 5-10 mm beyond the trap. The trap current in the case without solenoids is exactly what is expected. There is an initial positive current pulse of about 50 mA, balancing the image charge as the beam head enters the electron trap, followed by a gradually increasing positive current and finally a second capacitive pulse as the beam tail leaves the trap. The
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experiments studying desorbed gas and electron clouds in Ion Accelerators
Proceedings of the 2005 Particle Accelerator Conference, 2005Co-Authors: A W Molvik, R. H. Cohen, A. Friedman, F.m. Bieniosek, P A Seidl, S M Lund, M K Covo, J J Barnard, D Baca, J L VayAbstract:Electron clouds and gas pressure rise limit the performance of many major accelerator rings. We are studying these issues experimentally with ∼ 1 MeV heavy-Ion beams, coordinated with significant efforts in self-consistent simulatIon and theory. The experiments use multiple diagnostics, within and between quadrupole magnets, to measure the sources and accumulatIon of electrons and gas. In support of these studies, we have measured gas desorptIon and electron emissIon coefficients for potassium Ions impinging on stainless steel targets at angles near grazing incidence. Our goal is to measure the electron particle balance for each source – IonizatIon of gas, emissIon from beam tubes, and emissIon from an end wall – determine the electron effects on the Ion beam and apply the increased understanding to mitigatIon. We describe progress towards that goal.
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simulating electron clouds in heavy Ion Accelerators
Physics of Plasmas, 2005Co-Authors: R. H. Cohen, A. Friedman, F.m. Bieniosek, J L Vay, P A Seidl, Kireeff M Covo, A W Molvik, Peter Stoltz, S M Lund, Seth VeitzerAbstract:Contaminating clouds of electrons are a concern for most Accelerators of positively charged particles, but there are some unique aspects of heavy-Ion Accelerators for fusIon and high-energy density physics which make modeling such clouds especially challenging. In particular, self-consistent electron and Ion simulatIon is required, including a particle advance scheme which can follow electrons in regIons where electrons are strongly magnetized, weakly magnetized, and unmagnetized. The approach to such self-consistency is described, and in particular a scheme for interpolating between full-orbit (Boris) and drift-kinetic particle pushes that enables electron time steps long compared to the typical gyroperiod in the magnets. Tests and applicatIons are presented: simulatIon of electron clouds produced by three different kinds of sources indicates the sensitivity of the cloud shape to the nature of the source; first-of-a-kind self-consistent simulatIon of electron-cloud experiments on the high-current experim...
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electron cloud simulatIon and theory for high current heavy Ion beams
Physical Review Special Topics-accelerators and Beams, 2004Co-Authors: R. H. Cohen, A. Friedman, J L Vay, A W Molvik, Peter Stoltz, S M Lund, E P Lee, T Azevedo, Seth VeitzerAbstract:Stray electrons can arise in positive-Ion Accelerators for heavy-Ion fusIon or other applicatIons as a result of IonizatIon of ambient gas or gas released from walls due to halo-Ion impact, or as a result of secondary-electron emissIon. We summarize the distinguishing features of electron-cloud issues in heavy-Ion-fusIon Accelerators and a plan for developing a self-consistent simulatIon capability for heavy-Ion beams and electron clouds (also applicable to other Accelerators). We also present results from several ingredients in this capability. (1) We calculate the electron cloud produced by electron desorptIon from computed beam-Ion loss, which illustrates the importance of retaining Ion reflectIon at the walls. (2) We simulate the effect of specified electron-cloud distributIons on Ion beam dynamics. We consider here electron distributIons with axially varying density, centroid locatIon, or radial shape, and examine both random and sinusoidally varying perturbatIons. We find that amplitude variatIons are most effective in spoiling Ion beam quality, though for sinusoidal variatIons which match the natural Ion beam centroid oscillatIon or breathing-mode frequencies, the centroid and shape perturbatIons can also have significant impact. We identify an instability associated with a resonance between the beam-envelope ``breathing'' mode and the electron perturbatIon. We estimate its growth rate, which is moderate (compared to the reciprocal of a typical pulse duratIon). One conclusIon from this study is that heavy-Ion beams are surprisingly robust to electron clouds, compared to a priori expectatIons. (3) We report first results from a long-time-step algorithm for electron dynamics, which holds promise for efficient simultaneous solutIon of electron and Ion dynamics.
