Numerical analysis of electronegative plasma in the extraction region of negative hydrogen ion sources

Journal Article · Sat Jan 01 00:00:00 EST 2011 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.3530454· OSTI ID:21538005

Kuppel, S; Matsushita, D; Hatayama, A ^[1]; Bacal, M ^[2]

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1. Graduate School of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, 223-8522 Yokohama (Japan)
2. Laboratoire de Physique des Plasmas, Ecole Polytechnique, UPMC, Universite Paris-Sud 11, UMR 7648 CNRS, 91128 Palaiseau (France)

This numerical study focuses on the physical mechanisms involved in the extraction of volume-produced H{sup -} ions from a steady state laboratory negative hydrogen ion source with one opening in the plasma electrode (PE) on which a dc-bias voltage is applied. A weak magnetic field is applied in the source plasma transversely to the extracted beam. The goal is to highlight the combined effects of the weak magnetic field and the PE bias voltage (upon the extraction process of H{sup -} ions and electrons). To do so, we focus on the behavior of electrons and volume-produced negative ions within a two-dimensional model using the particle-in-cell method. No collision processes are taken into account, except for electron diffusion across the magnetic field using a simple random-walk model at each time step of the simulation. The results show first that applying the magnetic field (without PE bias) enhances H{sup -} ion extraction, while it drastically decreases the extracted electron current. Secondly, the extracted H{sup -} ion current has a maximum when the PE bias is equal to the plasma potential, while the extracted electron current is significantly reduced by applying the PE bias. The underlying mechanism leading to the above results is the gradual opening by the PE bias of the equipotential lines towards the parts of the extraction region facing the PE. The shape of these lines is due originally to the electron trapping by the magnetic field.

• OSTI ID: 21538005
• Journal Information: Journal of Applied Physics, Vol. 109, Issue 1; Other Information: DOI: 10.1063/1.3530454; (c) 2011 American Institute of Physics; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
BEAMS
COLLISIONS
COMPUTERIZED SIMULATION
DIFFUSION
ELECTRONEGATIVITY
ELECTRONS
EXTRACTION
HYDROGEN
HYDROGEN IONS 1 MINUS
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
NUMERICAL ANALYSIS
PLASMA POTENTIAL
PLASMA SIMULATION
RANDOMNESS
STEADY-STATE CONDITIONS
TRAPPING
ANIONS
CHARGED PARTICLES
ELECTRIC POTENTIAL
ELEMENTARY PARTICLES
ELEMENTS
FERMIONS
FLUID MECHANICS
HYDRODYNAMICS
HYDROGEN IONS
IONS
LEPTONS
MATHEMATICS
MECHANICS
NONMETALS
SEPARATION PROCESSES
SIMULATION