Decadal operation of the cesiated RF-driven ion source for negative hydrogen ions at J-PARC

Shinto, Katsuhiro   ; Okoshi, Kiyonori ; Shibata, Takanori*; Nammo, Kesao*; Kawai, Isao*; Ikegami, Kiyoshi*; Takagi, Akira*; Asano, Hiroyuki*; Ueno, Akira  ; Oguri, Hidetomo  

In the autumn of 2014, we initiated the operation of a cesiated radio frequency (RF)-driven negative hydrogen (H) ion source at J-PARC in response to the necessity for increased beam intensities in the experimental facilities. The RF-driven ion source has extracted H beams with a beam energy of 50 keV and a beam current of 33 mA at the outset, 47 mA since January 2016, and 60 mA since October 2018. The last value fulfills the requirement that the linac injects the H beams with a beam current of 50 mA as specified in the initial design value into the 3-GeV rapid-cycling synchrotron (RCS). Prior to the 2021/2022 campaign, the ion source had been exchanged on one to three occasions during a campaign. Because it was challenging to ascertain the operational longevity that the RF-driven ion source could deliver beams without any significant issues necessitating the suspension of operations. However, from the 2022/2023 campaign onwards, a single RF-driven H ion source has functioned to deliver the H beams, with the continuous operation time exceeding 4,400 hours. Over the course of this decade, three instances of antenna failure and several other issues have been encountered. This presentation provides the statistical data pertaining to the RF-driven H ion source in terms of user operations, along with an overview of the R&D status in relation to the future J-PARC upgrades.