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

Journal Article · Mon Sep 26 00:00:00 EDT 2011 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.3637420· OSTI ID:21611694

Surrey, Elizabeth; Porton, Michael ^[1]

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1. EURATOM/CCFE Fusion Association, Culham Science Centre, Abingdon, Oxon 0X14 3DB (United Kingdom)

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.

• OSTI ID: 21611694
• Journal Information: AIP Conference Proceedings, Vol. 1390, 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); ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

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