Beam-based alignment of the BPMs at J-PARC MR

In high beam intensity accelerators such as J-PARC, precise measurements of beam orbits are indispensable to control the beam orbits and to reduce beam losses as well as modeling the accelerators with determining precise machine parameters as beta function, dispersion function and so on. For these aim the centers of the BPMs should be known in terms of the quadrupole magnet centers in the transverse plane. In spring 2014 we carried beam based alignment (BBA) and beam based gain calibration (BBGC) for 186 BPMs in the J-PARC MR. Using fully calibrated BPMs, the closed orbits (COD) were corrected better than using previous partially calibrated BPMs. The residual CODs were improved from 0.39 mm (RMS) to 0.15 mm (RMS) in the vertical direction. Beam losses were reduced accordingly. In the horizontal plane the position data are significantly deteriorated by the synchrotron oscillation and the field ripples of the bending magnets. This makes the correction improvement ineffective in this plane. (author)