A5010861711- Particle accelerators and beam dynamics
- Particle Accelerators and Free-Electron Lasers
- Magnetic confinement fusion research
- Plasma Diagnostics and Applications
- Laser-Plasma Interactions and Diagnostics
- Gyrotron and Vacuum Electronics Research
- Superconducting Materials and Applications
- Ionosphere and magnetosphere dynamics
- Pulsed Power Technology Applications
- Ion-surface interactions and analysis
- Solar and Space Plasma Dynamics
- Nuclear Physics and Applications
- Electromagnetic Simulation and Numerical Methods
- Photocathodes and Microchannel Plates
- Electron and X-Ray Spectroscopy Techniques
- solar cell performance optimization
- Experimental Learning in Engineering
- Laser-induced spectroscopy and plasma
- Particle Detector Development and Performance
- Fusion materials and technologies
- Electrostatic Discharge in Electronics
- Gamma-ray bursts and supernovae
- Advanced X-ray Imaging Techniques
- High voltage insulation and dielectric phenomena
- Diamond and Carbon-based Materials Research
University of Maryland, College Park
2011-2022
Indiana State University
2019
United States Naval Research Laboratory
1994-2013
American Institute for Voice and Ear Research
2013
Cockcroft Institute
2010
University of Liverpool
2010
Technion – Israel Institute of Technology
2009
Lawrence Berkeley National Laboratory
1981-2005
Neurobehavioral Research Laboratory and Clinic
2003
Clarus Therapeutics (United States)
2002
Theory and simulation experiment are presented for a wide variety of transverse electromagnetic instabilities in plasmas with different sources degrees anisotropy. In each the electron bi-Maxwellian, electron-pinch, ion-pinch experiments, bulk response system during initial stages instability is good agreement predictions quasilinear theory. Furthermore, two independent energy constants which derive from fully nonlinear Vlasov-Maxwell equations found to remain constant very accuracy, even...
Ion heating by a strong ion-ion two-stream instability perpendicular to magnetic field in the presence of relatively cold electron background (Te≪miVd2) is considered. The strength such that ion trajectories are straight, whereas electrons bound lines (krLe≪1≪krLi). Theory presented for both quasilinear and nonlinear stages evolution system case electrostatic [(B2/8π) (1+β) >nmiVd2/8] compared with series computer simulation experiments. It found theory gives fairly accurate...
The beams in a heavy-ion-beam-driven inertial fusion (HIF) accelerator are collisionless, nonneutral plasmas, confined by applied magnetic and electric fields. These space-charge-dominated must be focused onto small (few mm) spots at the target, so preservation of emittance is crucial. nonlinear beam self-fields can lead to growth, self-consistent field description needed. To this end, multidimensional particle simulation code, warp [Friedman et al., Part. Accel. 37-38, 131 (1992)], has been...
The Warp code (and its framework of associated tools) was initially developed for particle-in-cell simulations space-charge-dominated ion beams in accelerators, heavy-ion-driven inertial fusion energy, and related experiments. It has found a broad range applications, including nonneutral plasmas traps, stray electron clouds laser-based acceleration, the focusing produced when short-pulse lasers irradiate foil targets. We summarize novel methods used Warp, including: time-stepping conducive...
Theoretical and computer simulation studies of whistler instabilities in anisotropic collisionless plasmas are presented. Initial bi-Maxwellian, Maxwellian with loss cone, hot superimposed on a more dense cold isotropic background electron distributions were used. Many the observed features common to all cases. Initially, total wave magnetic energy grows; average growth rate is good agreement linear theory; distribution isotropizes rapidly concomitant switching off high k number, initially...
Plasma simulations are often rendered challenging by the disparity of scales in time and space which must be resolved. When these disparities distinctive zones simulation domain, a method has proven to effective other areas (e.g., fluid dynamics simulations) is mesh refinement technique. A brief discussion challenges posed coupling this technique with plasma particle-in-cell given, followed presentation examples application heavy ion fusion related fields illustrate effectiveness approach....
Computer simulations are used to study whistler turbulence in plasmas driven by initially anisotropic bi-Maxwellian and loss-cone electron distributions. Linear growth saturates when the rate is of order particle trapping frequency.
In this paper, we describe results of self-consistent two-dimensional (x-z) particle-in-cell simulations, with a Monte Carlo collision model, an orificed micro-hollow cathode operating in planar diode geometry. The model includes thermionic electron emission Schottky effect, secondary due to bombardment by the plasma ions, several different processes, and non-uniform xenon background gas density cathode-anode gap. Simulated showing behavior density, potential distribution, energy flux...
The first experimental observation of a Korteweg--de Vries-type soliton wave train in intense electron beams is reported. A narrow, large-amplitude perturbation on long-pulse beam observed to steepen and spawn train. pulse width amplitude each peak remain unchanged over long propagation distance, the inversely proportional square width. Two such pulses are seen pass through other, emerging from collision unchanged. results reproduced by particle-in-cell simulations.
An experiment was designed to check theoretical predictions of charge homogenization and emittance growth in nonuniform space-charge-dominated beams due conversion field energy into transverse kinetic energy. Five beamlets were masked out a solid 5-keV electron beam injected periodic solenoidal focusing channel. Phosphor screen images showed that the merged an almost uniform density single beam. Images five-beamlet configuration observed at distance 7-8 lens periods. Experimental results on...
The dynamics of an ultrahigh-current electron ring in a modified-betatron configuration is addressed. This study includes analytical and numerical results for both ‘‘cold’’ ‘‘hot’’ rings. It has been found that the walls surrounding toroidal effects play very important role ring, even when wall conductivity infinite. For finite conductivity, diffusion ring’s self-magnetic field profoundly impacts its general equilibrium could be lost if means are not provided to compensate this effect. In...
A two-dimensional study is presented, based on computer simulation, of strong electron-ion streaming instabilities induced by counterstreaming ion beams, for initially cold electrons (ve ≪ vd). Wave growth agrees well with linear theory. Higher harmonics appear later, in good agreement mode coupling The wave spectrum, very broad perpendicular to the direction, narrows as heat and waves saturate, accordance quasilinear Electron heating explained nonresonant diffusion at early times, resonant...
High---Mach-number turbulent magnetosonic shocks caused by driving a purely reflecting piston into plasma have been simulated using an electromagnetic particle code. A physical analysis of the results is presented together with scaling arguments and comparisons experimental data.
A retarding electrostatic field energy analyzer for low-energy beams has been designed, simulated, and tested with electron of several keV, in which space-charge effects play an important role. cylindrical focusing electrode is used to overcome the beam expansion inside device due forces, emittance, etc. The voltage independently adjustable provide proper strength. Single particle simulation theoretical error analysis using envelopes show that this can get very high resolution (up 10 keV),...
The homogenization of a beam with transversely nonuniform initial density distribution is examined by masking the ouput from Pierce electron gun into five parallel beamlets, which are then propagated down channel periodically spaced solenoid focusing magnets. Experimental measurements, theoretical predictions, and PIC simulations in excellent agreement for averaged quantities such as rms emittance envelope radius. In addition, fine-structure characteristic nonlinear evolution beam, including...
The stabilization of electron beam interactions due to strongly turbulent nonlinearities is studied analytically and numerically for a wide range plasma parameters. A fluid mode coupling code described in which the effects ion Landau damping linear growth energetic are included phenomenological manner. Stabilization instability found occur when amplitudes unstable modes exceed threshold oscillating two-stream instability. coordinate space structure spectrum results clearly shows that...
Beams in which space charge forces are stronger than the force from thermal pressure nonneutral plasmas, since particles interact mostly via long-range collective potential. An ever-increasing number of applications demand such high-brightness beams. The University Maryland Electron Ring [P. G. O’Shea et al., Nucl. Instrum Methods Phys. Res. A 464, 646 (2001)], currently under construction, is designed for studying physics space-charge-dominated Indirect ways measuring beam emittance near...