Recovery from the earthquake and operation of the J-PARC linac

The Japan Proton Accelerator Research Complex (J-PARC) facilities were extensively damaged by the Great East Japan Earthquake on March 2011. At the linac facility, the buildings, especially those above the ground, were severely damaged. Owing to the damage, most of the conventional facilities were unavailable for several months. There were many cracks in the accelerator tunnel, and a large amount of groundwater (approximately 10 tons per day) leaked into the tunnel. The RF cavities and magnets themselves were not seriously damaged; however, vacuum leaks occurred in the ion source, the medium-energy beam transport 1 (MEBT1), and the separated-type drift tube linac (SDTL) sections from the destruction of the vacuum port, beam monitors, and bellows. Therefore, the accelerator components were exposed to highly humid air for several weeks. A maximum misalignment of 0.2 mm of the drift-tube (DT) bore center in the drift tube linac (DTL) was observed. A subsidence of more than 40 mm and a tilt of about 3 mrad were also observed in the accelerator tunnel. After significant recovery efforts, we resumed beam operation in December 2011 and user operation in January 2012. The beam power from the linac reached 13.3 kW in March 2012, which is equal to that just before the earthquake. In this report, we will discuss the recovery from the earthquake and the present operating status of the J-PARC linac.