Effort for the reliable operation in J-PARC Rapid Cycling Synchrotron

Yamamoto, Kazami   ; Takayanagi, Tomohiro   ; Togashi, Tomohito; Hatakeyama, Shuichiro

The beam commissioning of the J-PARC 3-GeV rapid cycling synchrotron (RCS) was started in 2007, and the proton beams were delivered to the neutron target along with the Main Ring synchrotron in December 2008. At the beginning of the RCS operation, the operation stability was compromised by the discharge of a thyratron that was a part of the power supply system of the extraction kicker magnet. We investigated the operational statistics of the thyratron to improve its reliability and found an efficient method that fit the characteristics of an individual thyratron. As a result, the discharge rate was improved dramatically. During the operation, a radiation leak accident occurred in the Hadron Experimental Hall. In addition, two other water leak accidents occurred in the neutron target. From these accidents, we considered that it was necessary to not only monitor the status of the accelerator components but also to monitor the beam condition and radiation level to obtain rapid detection of any target defects. Therefore, we developed a new monitoring system. Also we developed a new interlock system to prevent an extraction of an unexpected beam, which might affect the components in the downstream facilities. These improvements have improved the stability of the RCS operation.