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Title: Quantitative experiments with electrons in a positively charged beam

Abstract

Intense ion beams are difficult to maintain as non-neutral plasmas. Experiments and simulations are used to study the complex interactions between beam ions and (unwanted) electrons. Such ''electron clouds'' limit the performance of many accelerators. To characterize electron clouds, a number of parameters are measured, including total and local electron production and loss for each of three major sources, beam potential versus time, electron line-charge density, and gas pressure within the beam. Electron control methods include surface treatments to reduce electron and gas emission, and techniques to remove electrons from the beam or block their capture by the beam. Detailed self-consistent simulations include beam-transport fields and electron and gas generation and transport; these compute unexpectedly rich behavior, much of which is confirmed experimentally. For example, in a quadrupole magnetic field, ion and dense electron plasmas interact to produce multi-kV oscillations in the electron plasma and distortions of the beam velocity space distribution, without the system becoming homogeneous or locally neutral.

Authors:
; ; ; ; ; ; ; ; ; ;  [1];  [2]
  1. Heavy-Ion Fusion Science Virtual National Laboratory, Berkeley, California 94720 and Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
  2. (United States)
Publication Date:
OSTI Identifier:
20975080
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 14; Journal Issue: 5; Other Information: DOI: 10.1063/1.2436850; (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; ACCELERATORS; BEAM TRANSPORT; BEAM-PLASMA SYSTEMS; CAPTURE; CHARGE DENSITY; ELECTRONS; ION BEAMS; IONS; MAGNETIC FIELDS; PLASMA; PLASMA DENSITY; PLASMA DIAGNOSTICS; PLASMA SIMULATION; PLASMA WAVES; QUADRUPOLES; SURFACE TREATMENTS

Citation Formats

Molvik, A. W., Kireeff Covo, M., Cohen, R., Friedman, A., Lund, S. M., Sharp, W., Vay, J-L., Baca, D., Bieniosek, F., Leister, C., Seidl, P., and Heavy-Ion Fusion Science Virtual National Laboratory, Berkeley, California 94720 and Lawrence Berkeley National Laboratory, Berkeley, California 94720. Quantitative experiments with electrons in a positively charged beam. United States: N. p., 2007. Web. doi:10.1063/1.2436850.
Molvik, A. W., Kireeff Covo, M., Cohen, R., Friedman, A., Lund, S. M., Sharp, W., Vay, J-L., Baca, D., Bieniosek, F., Leister, C., Seidl, P., & Heavy-Ion Fusion Science Virtual National Laboratory, Berkeley, California 94720 and Lawrence Berkeley National Laboratory, Berkeley, California 94720. Quantitative experiments with electrons in a positively charged beam. United States. doi:10.1063/1.2436850.
Molvik, A. W., Kireeff Covo, M., Cohen, R., Friedman, A., Lund, S. M., Sharp, W., Vay, J-L., Baca, D., Bieniosek, F., Leister, C., Seidl, P., and Heavy-Ion Fusion Science Virtual National Laboratory, Berkeley, California 94720 and Lawrence Berkeley National Laboratory, Berkeley, California 94720. Tue . "Quantitative experiments with electrons in a positively charged beam". United States. doi:10.1063/1.2436850.
@article{osti_20975080,
title = {Quantitative experiments with electrons in a positively charged beam},
author = {Molvik, A. W. and Kireeff Covo, M. and Cohen, R. and Friedman, A. and Lund, S. M. and Sharp, W. and Vay, J-L. and Baca, D. and Bieniosek, F. and Leister, C. and Seidl, P. and Heavy-Ion Fusion Science Virtual National Laboratory, Berkeley, California 94720 and Lawrence Berkeley National Laboratory, Berkeley, California 94720},
abstractNote = {Intense ion beams are difficult to maintain as non-neutral plasmas. Experiments and simulations are used to study the complex interactions between beam ions and (unwanted) electrons. Such ''electron clouds'' limit the performance of many accelerators. To characterize electron clouds, a number of parameters are measured, including total and local electron production and loss for each of three major sources, beam potential versus time, electron line-charge density, and gas pressure within the beam. Electron control methods include surface treatments to reduce electron and gas emission, and techniques to remove electrons from the beam or block their capture by the beam. Detailed self-consistent simulations include beam-transport fields and electron and gas generation and transport; these compute unexpectedly rich behavior, much of which is confirmed experimentally. For example, in a quadrupole magnetic field, ion and dense electron plasmas interact to produce multi-kV oscillations in the electron plasma and distortions of the beam velocity space distribution, without the system becoming homogeneous or locally neutral.},
doi = {10.1063/1.2436850},
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}
}
  • Intense ion beams are an extreme example of, and difficult to maintain as, a non-neutral plasma. Experiments and simulations are used to study the complex interactions between beam ions and (unwanted) electrons. Such ''electron clouds'' limit the performance of many accelerators. To characterize electron clouds, a number of parameters are measured including: total and local electron production and loss for each of three major sources, beam potential versus time, electron line-charge density, and gas pressure within the beam. Electron control methods include surface treatments to reduce electron and gas emission, and techniques to remove, or block, electrons from the beam.more » Detailed, self-consistent simulations include beam-transport fields, and electron and gas generation and consistent transport, to compute unexpectedly rich behavior, much of which is confirmed experimentally. For example, in a quadrupole magnetic field, ion and dense electron plasmas interact to produce multi-kV oscillations in the electron plasma and distortions of the beam velocity space distribution, without becoming homogenous or locally neutral.« less
  • Intense ion beams are difficult to maintain as non-neutral plasmas. Experiments and simulations are used to study the complex interactions between beam ions and (unwanted) electrons. Such ''electron clouds'' limit the performance of many accelerators. To characterize electron clouds, a number of parameters are measured including: total and local electron production and loss for each of three major sources, beam potential versus time, electron line-charge density, and gas pressure within the beam. Electron control methods include surface treatments to reduce electron and gas emission, and techniques to remove electrons from the beam, or block their capture by the beam. Detailed,more » self-consistent simulations include beam-transport fields, and electron and gas generation and transport; these compute unexpectedly rich behavior, much of which is confirmed experimentally. For example, in a quadrupole magnetic field, ion and dense electron plasmas interact to produce multi-kV oscillations in the electron plasma and distortions of the beam velocity space distribution, without the system becoming homogeneous or locally neutral.« less
  • Plasma-produced electrons have been trapped for long periods of time in orbits around a positively charged wire. Since the frequency of rotation of each electron increases if it loses kinetic energy and sinks into the positive-potential well, phase bunching resulting in intense microwave emission can be easily excited.
  • A pseudopotential approach is used to investigate large amplitude dust-acoustic solitary structures for a plasma composed of positively charged dust, cold electrons, and nonthermal hot electrons. Numerical investigation for an adiabatic situation is conducted to examine the existence region of the wave. The negative potential of the double layers is found to be dependent on nonthermal parameters, Mach number, and electrons temperature. A range of the nonthermal parameters values exists for which two possible double layers for the same plasma mix at different Mach numbers and with significant different amplitudes. The present model is used to investigate localized structures inmore » the lower-altitude Earth's ionosphere.« less
  • Large amplitude dust acoustic solitary waves and double layers in a nonthermal plasma consisting of positively charged dust grains, nonthermal electrons, and isothermal ions including the effect of dust temperature have been studied using the Sagdeev potential technique by a computational scheme. The effect of different parameters on the nature of existence of solitary waves and double layers has been investigated to delimit their compositional parameter space. The physics corresponding to the computational result has been pointed out.