Experiment of optimal filament shape for the J-PARC H ion source

Namekawa, Yuya; Ueno, Akira  ; Okoshi, Kiyonori ; Oguri, Hidetomo  ; Ikegami, Kiyoshi*

The J-PARC H ion source driven with a lanthanum hexaboride filament (LaB-fil.) is successfully producing a stable beam for each J-PARC operation cycle of about 500 hours. However, its maximum peak H ion current of 36 mA does not satisfy the requirement of 60 mA for the J-PARC design beam power of 1 MW. In this paper, two results of the experiments to increase the current with a sufficient life-time are presented. That using a flat quintuple-hairpin LaB-fil. resulted in the lower current of 33 mA and the lower life-time of less than 230 hours. The deterioration seemed to be caused by the localized emission area due to too large magnetic field on it. On the other hand, that using two triple-hairpin tungsten filaments (W-fil.) connected in parallel with a short distance resulted in a life-time of 500 hours with a 15 kW arc power operation, which should produce an H ion current of more than 60 mA if cesium was seeded.