Numerical analysis of the spatial nonuniformity in a Cs-seeded H ion source

Takado, Naoyuki*; Hanatani, Junji*; Mizuno, Takatoshi*; Kato, Kyohei*; Hatayama, Akiyoshi*; Hanada, Masaya; Seki, Takayoshi; Inoue, Takashi

Surface production and transport process of H ions are numerically simulated to clarify the origin of H beam non-uniformity. A three-dimensional transport code using Monte Carlo method has been applied to productions of H atoms and H ions in a large negative ion source under the Cs seeded condition. The results show that a large fraction of hydrogen atoms are produced in a high electron temperature region. This leads to a spatial non-uniformity of H atom flux to the plasma grid where H atoms capture electrons and converted to H ions. In addition, most surface-produced H ions are extracted even through the high electron temperature region without destruction.