Status of the J-PARC 3 GeV RCS

The J-PARC rapid cycling synchrotron (RCS) was heavily affected by the last Great East Japan Earthquake. The damage to each device was investigated and an attempt was made to restore them, with successful beam commissioning of the the RCS beginning on 17 th December 2011. On the 22 nd , a 3 GeV beam was extracted to the MLF with beam currents that approached those obtained before the earthquake. Not only the recovery, but also an improvement of the RCS has been achieved, enabling high-power stable operation with low beam losses. Specifically, downstream beam losses due to the charge exchange foil were localized by installing a new collimator at injection area. As a result, the residual activation of this area was reduced by one order of magnitude and created the possibility of a higher beam power for the RCS. In a recent high-intensity trial of the RCS with a 420 kW equivalent intensity beam, significant progress toward design output beam power of 1 MW was demonstrated.