Abstract

Negative hydrogen (H⁻) ion sources have a wide range of applications. The general requirement for these ion sources is to produce intense ion beams with good beam optics. The purpose of this paper is to clarify the effects of the beam extraction voltage on the beam divergence angle by three-dimensional Particle-in-Cell (PIC) modeling. Perveance matching has been studied for a wide range of the extraction voltage with the model geometry of a Linac4 ion source. The extracted beam divergence angle is evaluated for extraction voltages ranging from 7 to 14 kV by using the Keio-BFX PIC code. The results show divergence minima in the range of 9.2–11.5 kV for the case without surface production, which correspond to experimental results. The dependence of divergence on the extraction voltage is explained by the change of the shape of the meniscus. In particular, a flat meniscus corresponds to low beam divergence, and particles extracted through the center of the meniscus have a lower divergence than particles extracted near the Plasma Electrode.

Recommended citation: M. Lindqvist, S. Nishioka, K. Miyamoto, K. Hoshino, J. Lettry, A. Hatayama, Journal of Applied Physics 126, 123303 (2019)
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