Soundness evaluation of J-PARC RF ion source after 5-month continuous operation

Abstract

In the J-PARC user operation from Nov. 2020 – Apr. 2021, continuous operation of J-PARC Radio Frequency (RF) negative hydrogen ion (H^-) source up to 3,651 hours (5 months) has been achieved. The ion source was operated with the output H^- current of 60 mA, the duty factor (for plasma generation) 2% and the input RF power up to 30 kW. After the operation, phase space diagrams at the Radio Frequency Quadrupole linac (RFQ) entrance were measured by the emittance monitor at the ion source test stand (IS-TS) under the same operation condition as in the J-PARC Linac. Comparison of the phase spaces and the beam emittances between the ion sources in the present and the previous operations shows slight difference. From the direct observation of the antenna coil, no exhaustion or the decrease in the thickness of the enamel coating of the coil have been confirmed. The results indicate the possibility of the next goal of the long-run up to 7 months, which is the same as the full duration of the J-PARC user operation in 1 year.