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Japan Proton Accelerator Research Complex

J-PARC back to operation after the summer maintenance

Japan Proton Accelerator Research Complex under operation jointly by the High Energy Accelerator Research Organization (KEK) and the Japan Atomic Energy Agency (JAEA).

J-PARC is back to its user operation since mid-October after three months of summer shutdown for maintenance. Beam operation was suspended for maintenance during the summer shutdown from July to September. Maintenance of the components and various improvement work were conducted in the accelerator facilities. The linac started beam commissioning in 2006 and some of the components are approaching the end of life. For the 324-MHz radio frequency systems, we are using 20 klystrons, and we have replaced some of them in these years based on the conditions. As preventive measures during this summer shutdown, we have replaced four klystrons. Most of them exceeded operation time of 55,000 hours and have shown lowering of their performance. We have performed reliability improvement work continuously such as cleanup inside the separated type drift tube linac cavities and cooling water flow stabilization.

The highlights are as follows: 1) The proton beam window #2 was replaced with a new one after three years of use at 2500 MWh irradiation. Highly activated proton beam window, which was mounted on a 3.8 m long iron plug, was lifted up into a shielding cask on the top of the neutron source station and was moved to the irradiated component room. The replacement was done with remote handling tools. 2) The off-gas process system to collect gaseous radioactive materials which are generated in the target was improved so that processing of both collected radioactive gas and exhaust gas stored in the gas holders through the stack can be done in parallel. This is the second step update to shorten the target vessel replacement time from 32 workdays to 23 workdays after the addition of gas holders last March. From October 2, replacement of the target vessel with improved water shroud structure will be performed. With the new target vessel, we are going to operate the target with power of 300 to 500 kW in the operating period from autumn to next summer.

A report meeting of industrial application at J-PARC MLF was held on July 20 and July 21 at Akihabara Convention Center. Total number of attendees was 452 during the two days of this meeting. The promotion of industrial application is one of the main missions of MLF. The industrial application at MLF is growing but it is not steady in terms of “creation of Innovation” through the industrial application of neutron and muon experiments. In this report meeting, it aimed to get common understanding of the essential output on the innovation and requiring actions by MLF for results between.

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