J-PARC upgrade

Ouchi, Nobuo 

J-PARC is in the first phase now. Proton beams have reached to the all experimental facilities up to now, and user operation of MLF started in 2008. Superconducting proton linac (SCL) from 400 to 600 MeV and the Transmutation Experimental Facility are planned in the second construction phase. SCL will consist of 11 cryomodules and two 9-cell 972 MHz elliptical cavities will be installed in each cryomodule. As two cavities will be driven by one klystron, phase stability between two cavities under the Lorentz force detuning in the pulsed operation is most important issue to be developed. A prototype cryomodule was fabricated, which was designed to be less Lorentz force detuning, and two cavity excitation was tested. The phase stability at 2K is satisfactory acceptable, while it deteriorates at 4K due to the microphonic noise. Design of SCL and the experimental results of the prototype cryomodule are presented.