Status of the J-PARC RF ion source

In order to satisfy the requirements of the Japan Proton Accelerator Research Complex (J-PARC) second stage, which will produce a 1 MW beam, the Cs-free LaB₆-filament-driven H^- ion source was replaced to a cesiated RF-driven H^- ion source (RF ion source) during the summer shutdown period on 2014. By developing and testing the RF ion source on an off-line test-stand for about five years, it successfully and stably produced a peak current of more than 60 mA within the acceptance of the following RFQ linac with the required beam duty-factor of more than 1.25% (500 μs × 25 Hz). For about one year, the RF ion source has been operated with a peak current of 33 mA routinely, which causes the smallest beam loss in the J-PARC operated with a 500 kW beam. It has been also operated with a peak current of 55 mA for a few weeks in each two months for the J-PARC beam study striving toward the 1 MW beam operation. The beam current is controlled within the error of ±0.1 mA by feed-backing the RF power and the Cs density during the operation. Except for the only one failure of the internal RF-antenna in the beginning of the operation, there was no serious trouble. The RF ion source with the 33 mA peak current operation is successfully operated for approximately 1100 hours. (author)