Beam study of the extructed beam from the RFQ of the J-PARC linac

Yanai, Kyosuke; Kondo, Yasuhiro   ; Otani, Masashi*

We have upgraded the J-PARC linac to a beam current of 50 mA. As the beam current increase, more precise beam tuning is required in the medium-energy beam transport (MEBT1) line from RFQ to DTL. To obtain more precise beam orbit information, we reconfirm the electric centers of the BPM's installed in the quadrupole magnets match to the magnetic centers of the quadrupoles using beam based alignment (BBA) method for all BPM's in the MEBT. As a result, we obtained data indicating some BPM's centers are at most 3 mm displaced from the quadrupole centers. This suggests that the responses of these BPM's are not correctly correspond to the actual beam position. Further investigation of the BMP response is needed.