The Realignment of the beamline for J-PARC 3GeV RCS

Tani, Norio  ; Yamamoto, Masanobu   ; Kamiya, Junichiro   ; Hotchi, Hideaki  ; Kinsho, Michikazu  

J-PARC 3GeV RCS suffered from the misalignments of several millimeters of the magnets in both horizontal and vertical directions caused by the Tohoku Region Pacific Coast Earthquake on March 11, 2011. As the result of the orbit calculation showed that the beam loss was acceptable for beam operation at 300 kW, beam operation with the current placement was implemented until May, 2013. However according to the simulation of beam loss at 1 MW operation, it was found out that the beam loss increased and the horizontal emittance expanded. Therefore it was understood that 1 MW operation was difficult without the realignment of the beamline. The realignment of the beamline was carried out from July to November, 2013 in conjunction with the upgrade of Linac. During the realignment, the adjustment of the magnets and the ceramics chambers was mainly performed. The magnets were adjusted to within 0.2 mm. The ceramics chambers were aimed to be adjusted within 0.5 mm. Beam commissioning started on January 30, 2014. RCS succeeded in injection of 400 MeV beam from the upgraded Linac and extraction of 3GeV beam to MLF. In this paper, the alignment result of the magnets and the ceramics chambers that constitute the beamline of 3 GeV RCS is reported.