Malfunction, Cause and Recurrence Prevention Measures of J-PARC Slow Extraction

The radiation leakage accident occurred at the J-PARC hadron experimental hall in May 2013 was triggered by a target damage due to an unanticipated short beam pulse from J-PARC main ring. An extremely short beam pulse was produced by a rapid current increase of the quadrupole (EQ) power supply system for a spill feedback. A simulation with the slow extraction process could explain such a short beam pulse generation. The cause of the malfunction has been identified by an intensive investigation of the EQ power supply system performed after the accident. We will show measures to prevent recurrence.
Proceedings of the 5th Int. Particle Accelerator Conf., IPAC2014, Dresden, Germany