================================================================ J-PARC Project Newsletter Special issue 19 September 2008 ================================================================ The J-PARC 3-GeV RCS achieved a beam power of 210 kW for a period of 70 seconds at 25Hz, and 315kW-equivalent power in one-pulse operation. At 6:33 pm on September 17th, the J-PARC 3-GeV Rapid-Cycling Synchrotron (RCS) accelerated a pulse of 2.3E13 protons to 3 GeV, which was successfully extracted to the beam dump. This beam flux corresponds to a beam power of 315 kW, if operated at 25 Hz. The beam loss at the extraction point was less than one percent, which is well below the designed value for the 25Hz operation. At 11:00 am on September 18th, the RCS achieved the beam power of 210 kW (1.77E13 protons per pulse) to the beam dump for 70 seconds with 25 Hz operation. The beam loss of 3% was observed at a collimator section from the linac to RCS at the injection energy of 180 MeV. This is well below the designed value and can be handled by the method of hand-on maintenance. As a demonstration, one pulse of 2.93E13 protons, which is equivalent to 352 kW for 25 Hz operation, was accelerated and extracted with a beam loss of 4% at the injection area. In the present commissioning operations, the transverse painting technique was not yet utilized, while the longitudinal painting was done. The beam operation beyond 300 kW may require the transverse painting and one more RF station, both of which are planned in this fall.