Beam based alignment of the beam position monitors at J-PARC RCS

Hayashi, Naoki  ; Harada, Hiroyuki  ; Hotchi, Hideaki  ; Toyama, Takeshi*; Tejima, Masaki*

The J-PARC RCS is an M-Watt class rapid cycling synchrotron and, its physical aperture is designed to be more than 250mm in diameter. Even though its chamber size is such large, the BPM system gives precise data to determine beam optics parameters of the ring. For this purpose, relative positions and resolutions are important, however, for much higher intensity, the absolute beam position and accurate COD correction are indispensable. We have carefully installed the BPM, but it is also necessary to estimate its absolute position by using beam. If each QM could be controlled independently, the simple beam based alignment technique can be utilized, but it is not the case for RCS. There are seven families of QM, and only each family can be controlled at one time. We developed a new technique by expanding the simple method for the case of multiple QM focusing changed simultaneously, and applied to the J-PARC RCS. The paper describes this method and discussed about experimental results.