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Title: Space Charge Neutralization of DEMO Relevant Negative Ion Beams at Low Gas Density

Abstract

The application of neutral beams to future power plant devices (DEMO) is dependent on achieving significantly improved electrical efficiency and the most promising route to achieving this is by implementing a photoneutralizer in place of the traditional gas neutralizer. A corollary of this innovation would be a significant reduction in the background gas density through which the beam is transported between the accelerator and the neutralizer. This background gas is responsible for the space charge neutralization of the beam, enabling distances of several metres to be traversed without significant beam expansion. This work investigates the sensitivity of a D{sup -} beam to reduced levels of space charge compensation for energies from 100 keV to 1.5 MeV, representative of a scaled prototype experiment, commissioning and full energy operation. A beam transport code, following the evolution of the phase space ellipse, is employed to investigate the effect of space charge on the beam optics. This shows that the higher energy beams are insensitive to large degrees of under compensation, unlike the lower energies. The probable degree of compensation at low gas density is then investigated through a simple, two component beam-plasma model that allows the potential to be negative. The degree ofmore » under-compensation is dependent on the positive plasma ion energy, one source of which is dissociation of the gas by the beam. The subsequent space charge state of the beam is shown to depend upon the relative times for equilibration of the dissociation energy and ionization by the beam ions.« less

Authors:
;  [1]
  1. EURATOM/CCFE Fusion Association, Culham Science Centre, Abingdon, Oxon 0X14 3DB (United Kingdom)
Publication Date:
OSTI Identifier:
21611694
Resource Type:
Journal Article
Journal Name:
AIP Conference Proceedings
Additional Journal Information:
Journal Volume: 1390; Journal Issue: 1; Conference: 2. international symposium on negative ions, beams and sources, Takayama City (Japan), 16-19 Nov 2010; Other Information: DOI: 10.1063/1.3637420; (c) 2011 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0094-243X
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ACCELERATORS; ANIONS; BEAM INJECTION HEATING; BEAM OPTICS; BEAM TRANSPORT; BEAM-PLASMA SYSTEMS; DEUTERIUM IONS; DISSOCIATION ENERGY; ION BEAMS; IONIZATION; KEV RANGE; MEV RANGE; NEUTRAL ATOM BEAM INJECTION; PHASE SPACE; PLASMA; SPACE CHARGE; BEAM INJECTION; BEAMS; CHARGED PARTICLES; ENERGY; ENERGY RANGE; HEATING; IONS; MATHEMATICAL SPACE; PLASMA HEATING; SPACE

Citation Formats

Surrey, Elizabeth, and Porton, Michael. Space Charge Neutralization of DEMO Relevant Negative Ion Beams at Low Gas Density. United States: N. p., 2011. Web. doi:10.1063/1.3637420.
Surrey, Elizabeth, & Porton, Michael. Space Charge Neutralization of DEMO Relevant Negative Ion Beams at Low Gas Density. United States. doi:10.1063/1.3637420.
Surrey, Elizabeth, and Porton, Michael. Mon . "Space Charge Neutralization of DEMO Relevant Negative Ion Beams at Low Gas Density". United States. doi:10.1063/1.3637420.
@article{osti_21611694,
title = {Space Charge Neutralization of DEMO Relevant Negative Ion Beams at Low Gas Density},
author = {Surrey, Elizabeth and Porton, Michael},
abstractNote = {The application of neutral beams to future power plant devices (DEMO) is dependent on achieving significantly improved electrical efficiency and the most promising route to achieving this is by implementing a photoneutralizer in place of the traditional gas neutralizer. A corollary of this innovation would be a significant reduction in the background gas density through which the beam is transported between the accelerator and the neutralizer. This background gas is responsible for the space charge neutralization of the beam, enabling distances of several metres to be traversed without significant beam expansion. This work investigates the sensitivity of a D{sup -} beam to reduced levels of space charge compensation for energies from 100 keV to 1.5 MeV, representative of a scaled prototype experiment, commissioning and full energy operation. A beam transport code, following the evolution of the phase space ellipse, is employed to investigate the effect of space charge on the beam optics. This shows that the higher energy beams are insensitive to large degrees of under compensation, unlike the lower energies. The probable degree of compensation at low gas density is then investigated through a simple, two component beam-plasma model that allows the potential to be negative. The degree of under-compensation is dependent on the positive plasma ion energy, one source of which is dissociation of the gas by the beam. The subsequent space charge state of the beam is shown to depend upon the relative times for equilibration of the dissociation energy and ionization by the beam ions.},
doi = {10.1063/1.3637420},
journal = {AIP Conference Proceedings},
issn = {0094-243X},
number = 1,
volume = 1390,
place = {United States},
year = {2011},
month = {9}
}