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Modeling of Negative Ion Transport
in Cesium-Seeded Volume Negative Ion Sources
Osamu Fukumasa and Ryo Nishida
Department of Electrical and Electronic Engineering, Faculty of Engineering,
Yamaguchi University, Tokiwadai 2-16-1, Ube 755-8611, Japan
Abstract: Trajectories of H- ions are calculated numerically by solving the 3D motion
equation, including effects of collisional destruction, elastic collisions and charge exchange
collisions. According to these trajectories, extraction probability of H- ions produced at any
location inside the source and energy of extracted H- ions are discussed as a function of gas
pressure. Effects of production zone and filter magnetic field on extraction probability are
also discussed. The probability for surface produced H- ions keeps nearly the constant value,
and that for volume produced H- ions decreases with gas pressure. The kinetic energy of
extracted H- ions is reduced mainly by charge exchange collision.
We also discuss the characteristics of extracted negative ion current combining the present
numerical results and the results of the model calculation with the zero-dimensional code.
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Abstract (pdf)