A Dummy beam pipe with improved gap connections for a high power test cavity for J-PARC RCS MA cores

Shimada, Taihei ; Yamamoto, Masanobu   ; Nomura, Masahiro  ; Schnase, A.; Tamura, Fumihiko   ; Hara, Keigo*; Hasegawa, Katsushi*; Omori, Chihiro*; Toda, Makoto*; Suzuki, Hiromitsu; Yoshii, Masahito*

The beam pipes of the RF acceleration section in the J-PARC RCS have a large aperture (247 mm) in order to handle a high power proton beam of 1 MW with acceptable loss. When we disassemble and later reassemble the test cavity in between the high power test runs for the MA cores, it is quite hard work to take out, and reinstall the beam pipe. Therefore, instead of using an original beam pipe, risking that it becomes unusable for accelerator operation due to scratches or discharges, we developed a light weight dummy beam pipe and dedicated copper connection parts for the acceleration gaps, which are easy to take apart and to assemble. Accordingly, the copper parts, which are used to connect the acceleration gaps to the cavity tanks for the installed cavity systems were redesigned, so that the time required for assembly or disassembly is reduced. This is especially important, as the cavities in the accelerator tunnel are in a high radiation environment caused by high power RCS operation.