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ion sourceUeno, Akira
no journal, ,
At the 15th International Conference on Ion Sources (ICIS'13), the rf-driven H ion source, which satisfied the Japan Proton Accelerator Research Complex (J-PARC) 2nd stage requirements of an H ion beam current of 60mA within normalized emittances of 1.5
mm
mrad both horizontally and vertically and a flat top beam duty factor of 1.25
(500
s
25Hz), was reported. The most important experimental result was that the emittances unexpectedly largely depended upon the plasma electrode (PE) temperature (T
) and the RF-power (P
). There were two essential conditions of T
150
C and P 40 kW in order to satisfy the requirements. In the meeting, the recent experimental result that there is a sufficient condition of the optimum cesium deposition on the PE surface is reported. Furthermore, the cesiation sequence for the T
69C operation, which produces smaller emittances, is reported.
Yamazaki, Saishun
no journal, ,
A cesium-free H
ion source driven with a LaB
filament is being operated at the Japan Proton Accelerator Research Complex (J-PARC) without any serious trouble since the restoration from the March 2011 earthquake. The beam current from the source is routinely restricted approximately 19 mA for the lifetime of the filament. To increase the beam power at the linac beam operation, the beam current from the source was increased to 22 mA. At this operation, the lifetime of the filament was estimated by the reduction in the filament current. According to the steep reduction in the filament current, the break of the filament was predicted. As a part of the beam current upgrade plan, the front end test stand consisting of the rf-driven H ion source developed for the J-PARC 2nd stage requirements and the RFQ is under preparation.
Kojima, Atsushi; Hanada, Masaya; Yoshida, Masafumi; Akashi, Keisuke
no journal, ,
In this paper, the recent activities on the new test stand are reported toward demonstration of the long pulse production for 22A, 100s negative ion beams. As for the temperature control of the plasma grid, a prototype of the grid with cooling/heating by circulating a high-temperature fluorinated fluid has been developed. This grid was found to have a capability to control the temperature with a time constant of 10s by considering the physical properties of the fluid. As a result, 120 A/m
beams for 100 s have been achieved, which is about 90 percent of the rated value for JT-60SA.
Akashi, Keisuke; Kojima, Atsushi; Yoshida, Masafumi; Hanada, Masaya; Yamano, Yasushi*
no journal, ,
To improve the voltage holding capability of the large-size multi-aperture grid, the clarification of the mechanism of the break-down should be understood. However, the relation between the locally electric field and the break-down is still unclear. This time, this relation was investigated by direct measurement of the dark current density as the initiation of the break-down may be caused by the field-emitted electrons. As a result, the break-down probability increases with the current density, and current density of 0.1 mA/m cause the break-down at 50% in 10 s pulse.
Yoshida, Masafumi; Hanada, Masaya; Kojima, Atsushi; Kashiwagi, Mieko
no journal, ,
Non-uniformity of the negative ion beams in the JT-60 negative ion source with the world-largest ion extraction area was improved by modifying the magnetic filter in the source from the PG filter to a tent-shaped filter. The magnetic design via electron trajectory calculation showed that the tent-shaped filter was expected to suppress the localization of the primary electrons emitted from the filaments and created uniform plasma with positive ions and atoms of the parent particles for the negative ions. By modifying the magnetic filter to the tent-shaped filter, the uniformity defined as the deviation from the averaged beam intensity was reduced from 14% of the PG filter to 
10% without a reduction of the negative ion production.