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Title: Simulation studies of non-neutral plasma equilibria in an electrostatic trap with a magnetic mirror

Abstract

The equilibrium of an infinitely long, strongly magnetized, non-neutral plasma confined in a Penning-Malmberg trap with an additional mirror coil has been solved analytically [J. Fajans, Phys. Plasmas 10, 1209 (2003)] and shown to exhibit unusual features. Particles not only reflect near the mirror in the low field region, but also may be weakly trapped in part of the high field region. The plasma satisfies a Boltzmann distribution along field lines; however, the density and the potential vary along field lines. Some other simplifying assumptions were employed in order to analytically characterize the equilibrium; for example the interface region between the low and high field regions was not considered. The earlier results are confirmed in the present study, where two-dimensional particle-in-cell (PIC) simulations are performed with the Warp code in a more realistic configuration with an arbitrary (but physical) density profile, realistic trap geometry and magnetic field. A range of temperatures and radial plasma sizes are considered. Particle tracking is used to identify populations of trapped and untrapped particles. The present study also shows that it is possible to obtain local equilibria of non-neutral plasmas using a collisionless PIC code, by a scheme that uses the inherent numerical collisionality asmore » a proxy for physical collisions.« less

Authors:
; ; ; ; ; ;  [1];  [2];  [3];  [3];  [3]
  1. Center for Beam Physics, Lawrence Berkeley National Laboratory and Department of Physics, University of California, Berkeley, Berkeley, California 94720 (United States)
  2. (Israel)
  3. (United States)
Publication Date:
OSTI Identifier:
20974967
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 14; Journal Issue: 5; Other Information: DOI: 10.1063/1.2727470; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; COLLISIONS; CONFIGURATION; DISTRIBUTION; ELECTRON TEMPERATURE; EQUILIBRIUM; GEOMETRY; ION TEMPERATURE; MAGNETIC FIELDS; MAGNETIC MIRRORS; PLASMA; PLASMA DENSITY; PLASMA SIMULATION; TRAPPING; TRAPS; TWO-DIMENSIONAL CALCULATIONS

Citation Formats

Gomberoff, K., Fajans, J., Wurtele, J., Friedman, A., Grote, D. P., Cohen, R. H., Vay, J.-L., Physics Department, Technion, Haifa 32000, Center for Beam Physics, Lawrence Berkeley National Laboratory and Department of Physics, University of California, Berkeley, Berkeley, California 94720, Fusion Energy Program, Lawrence Livermore National Laboratory, Livermore, California 94550, and Lawrence Berkeley National Laboratory, Berkeley, California 94720. Simulation studies of non-neutral plasma equilibria in an electrostatic trap with a magnetic mirror. United States: N. p., 2007. Web. doi:10.1063/1.2727470.
Gomberoff, K., Fajans, J., Wurtele, J., Friedman, A., Grote, D. P., Cohen, R. H., Vay, J.-L., Physics Department, Technion, Haifa 32000, Center for Beam Physics, Lawrence Berkeley National Laboratory and Department of Physics, University of California, Berkeley, Berkeley, California 94720, Fusion Energy Program, Lawrence Livermore National Laboratory, Livermore, California 94550, & Lawrence Berkeley National Laboratory, Berkeley, California 94720. Simulation studies of non-neutral plasma equilibria in an electrostatic trap with a magnetic mirror. United States. doi:10.1063/1.2727470.
Gomberoff, K., Fajans, J., Wurtele, J., Friedman, A., Grote, D. P., Cohen, R. H., Vay, J.-L., Physics Department, Technion, Haifa 32000, Center for Beam Physics, Lawrence Berkeley National Laboratory and Department of Physics, University of California, Berkeley, Berkeley, California 94720, Fusion Energy Program, Lawrence Livermore National Laboratory, Livermore, California 94550, and Lawrence Berkeley National Laboratory, Berkeley, California 94720. Tue . "Simulation studies of non-neutral plasma equilibria in an electrostatic trap with a magnetic mirror". United States. doi:10.1063/1.2727470.
@article{osti_20974967,
title = {Simulation studies of non-neutral plasma equilibria in an electrostatic trap with a magnetic mirror},
author = {Gomberoff, K. and Fajans, J. and Wurtele, J. and Friedman, A. and Grote, D. P. and Cohen, R. H. and Vay, J.-L. and Physics Department, Technion, Haifa 32000 and Center for Beam Physics, Lawrence Berkeley National Laboratory and Department of Physics, University of California, Berkeley, Berkeley, California 94720 and Fusion Energy Program, Lawrence Livermore National Laboratory, Livermore, California 94550 and Lawrence Berkeley National Laboratory, Berkeley, California 94720},
abstractNote = {The equilibrium of an infinitely long, strongly magnetized, non-neutral plasma confined in a Penning-Malmberg trap with an additional mirror coil has been solved analytically [J. Fajans, Phys. Plasmas 10, 1209 (2003)] and shown to exhibit unusual features. Particles not only reflect near the mirror in the low field region, but also may be weakly trapped in part of the high field region. The plasma satisfies a Boltzmann distribution along field lines; however, the density and the potential vary along field lines. Some other simplifying assumptions were employed in order to analytically characterize the equilibrium; for example the interface region between the low and high field regions was not considered. The earlier results are confirmed in the present study, where two-dimensional particle-in-cell (PIC) simulations are performed with the Warp code in a more realistic configuration with an arbitrary (but physical) density profile, realistic trap geometry and magnetic field. A range of temperatures and radial plasma sizes are considered. Particle tracking is used to identify populations of trapped and untrapped particles. The present study also shows that it is possible to obtain local equilibria of non-neutral plasmas using a collisionless PIC code, by a scheme that uses the inherent numerical collisionality as a proxy for physical collisions.},
doi = {10.1063/1.2727470},
journal = {Physics of Plasmas},
number = 5,
volume = 14,
place = {United States},
year = {Tue May 15 00:00:00 EDT 2007},
month = {Tue May 15 00:00:00 EDT 2007}
}
  • The equilibrium of an infinitely long, strongly magnetized, non-neutral plasma confined in a Penning-Malmberg trap with an additional mirror coil has been solved analytically [J. Fajans, Phys. Plasmas 10, 1209 (2003)] and shown to exhibit unusual features. Particles not only reflect near the mirror in the low field region, but also may be weakly trapped in part of in the high field region. The plasma satisfies a Boltzmann distribution along field lines; however, the density and the potential vary along field lines. Some other simplifying assumptions were employed in order to analytically characterize the equilibrium; for example the interface regionmore » between the low and high field regions was not considered. The earlier results are confirmed in the present study, where two-dimensional particle-in-cell simulations are performed with the Warp code in a more realistic configuration with an arbitrary (but physical) density profile, realistic trap geometry and magnetic field. A range of temperatures and radial plasma sizes are considered. Particle tracking is used to identify populations of trapped and untrapped particles. The present study also shows that it is possible to obtain local equilibria of non-neutral plasmas using a collisionless PIC code, by a scheme that uses the inherent numerical collisionality as a proxy for physical collisions.« less
  • The equilibrium of an infinitely long, strongly magnetized, non-neutral plasma confined in a Penning-Malmberg trap with an additional mirror coil has been solved analytically [J. Fajans, Phys. Plasmas 10, 1209 (2003)] and shown to exhibit unusual features. Particles not only reflect near the mirror in the low field region, but also may be weakly trapped in part of in the high field region. The plasma satisfies a Boltzmann distribution along field lines; however, the density and the potential vary along field lines. Some other simplifying assumptions were employed in order to analytically characterize the equilibrium; for example the interface regionmore » between the low and high field regions was not considered. The earlier results are confirmed in the present study, where two-dimensional particle-in-cell simulations are performed with the Warp code in a more realistic configuration with an arbitrary (but physical) density profile, realistic trap geometry and magnetic field. A range of temperatures and radial plasma sizes are considered. Particle tracking is used to identify populations of trapped and untrapped particles. The present study also shows that it is possible to obtain local equilibria of non-neutral plasmas using a collisionless PIC code, by a scheme that uses the inherent numerical collisionality as a proxy for physical collisions.« less
  • Spectroscopic comparison of antihydrogen and hydrogen atoms is one of the best candidates for the stringent tests of the CPT symmetry, and intensive studies are being carried out by using Antiproton Decelerator at CERN. The ASACUSA collaboration has constructed a superconducting cusp trap for the formation, trapping and extraction of antihydrogen atoms, where a quadrupole magnetic field is generated by a pair of anti-Helmholtz coils with anti-parallel currents. The cusp configuration is considerably advantageous for the extraction of spin-polarized and ground-state antihydrogen beams that are ideal for the spectroscopic measurements of hyperfine structures of the ground state of antihydrogen. Formore » the effective generation of antihydrogen atoms, it is essential to form high density and stable plasmas of antiproton and positrons. In this study, we applied a rotating electric field to an electron plasma in the inhomogeneous cusp magnetic field, and demonstrated the effective radial compression of a non-neutral plasma in a broad frequency range. The compression rate depended on the rotating frequency and had a broad peak extending on both sides of a longitudinal (1,0) mode frequency, which was the only observed characteristic frequency. The similar procedure can in principle be applied to positron and antiproton plasmas, and the results are one of necessary steps toward antihydrogen experiments in the cusp trap.« less
  • The resonance microwave plasma heating in a large-scale open magnetic trap is simulated taking into account all the basic wave effects during the propagation of short-wavelength wave beams (diffraction, dispersion, and aberration) within the framework of the consistent quasi-optical approximation of Maxwell’s equations. The quasi-optical method is generalized to the case of inhomogeneous media with absorption dispersion, a new form of the quasi-optical equation is obtained, the efficient method for numerical integration is found, and simulation results are verified on the GDT facility (Novosibirsk).
  • It has been suggested that magnetically trapped particles play a role in the asymmetry-induced radial transport observed in the Occidental non-neutral plasma trap. This magnetic trapping would occur due to a small increase ({beta}{identical_to}{delta}B/B{approx_equal}0.4%) in magnetic field at the center of our solenoid and would keep low velocity particles confined to the ends of the trap. To test this suggestion, three coils of additional windings have been added to the trap solenoid thus allowing adjustment of the axial field variation {delta}B. The effect of these adjustments on typical radial flux resonances is investigated. Making B as uniform as possible reducesmore » {beta} by a factor of 5.9, but this produces little change in the transport. Varying {beta} over the broader range from -8.5% to 9.5% gives variations of 20%-90% in the magnitude, peak frequency, and width of the flux resonances, but these variations do not match the predictions of a simple model of trapped particle transport based on isotropic particle distributions.« less