Plasma and Fusion Research

Volume 11, 2406044 (2016)

Regular Articles

Numerical Analysis of Electron Energy Distribution Function and Its Effects on the H− Production in Linac4 H− Source
Shintaro MOCHIZUKI, Stefano MATTEI1), Kenjiro NISHIDA, Akiyoshi HATAYAMA and Jacques LETTRY1)
Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
1)
CERN, 1211 Geneva 23, Switzerland
(Received 30 November 2015 / Accepted 2 March 2016 / Published 10 June 2016)

Abstract

In order to enhance the H− surface production in hydrogen negative ion sources, it is important to increase the density of the H atoms dissociated from H2 molecule and the resultant atomic flux towards the surface of the plasma grid. In this paper, the effect of the Electron Energy Distribution Function (EEDF) on the dissociation of H2 in Linac4 H− source has been studied using Electromagnetic Particle In Cell (EM-PIC) simulation with Monte Carlo method for Collision Processes (MCC). It has been shown that the rate coefficient of dissociation reactions can be enhanced in the lower H2 gas pressure regime, while the H atom production rate becomes larger in the higher pressure regime. It is suggested that the optimal H2 gas pressure to maximize the H atom production is determined by the balance of rate coefficient and the H2 density.

Keywords

negative ion source, rf plasma, electron energy distribution function, dissociation rate, particle in cell

DOI: 10.1585/pfr.11.2406044

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