Speaker
Description
The 3-GeV RCS (Rapid Cycling Synchrotron) of J-PARC accelerates 8.33E13 protons per pulse from 0.4 GeV to 3 GeV at a repetition rare of 25 Hz for 1 MW output beam power. We have already achieved stable operation at the designed 1 MW beam power by sufficiently minimizing the beam loss [1]. The residual beam loss is mostly caused by the unavoidable foil scattering beam loss, occurring around injection period. To cope with upgrades of the downstream facilities, recently we have conducted 1.5 MW beam test by increasing 25% and 20% of the injection peak current and pulse length, respectively. To overcome the space charge effect at 1.5 times higher beam intensity in the RCS, careful optimizations have been done for both transverse and longitudinal injection paintings. In addition, an extremely wider and uniform momentum spread of the injection beam was utilized. As a result, the beam loss at 1.5 MW has also been significantly reduced. The measured beam loss is estimated to be less than 0.1% occurring only at lower beam energy dominating by the foil scattering of the circulating beam during injection period and well localized at the collimator section. The beam loss power has been estimated to be only less than 0.2 kW, significantly lower than the collimator capacity of 4 kW. The machine activation at 1.5 MW can be thus kept at a sufficiently low level as of present 1 MW operation. The details of beam test and numerical simulation results will be presented.