Residual Field Correction of Pulsed Bending Magnet

At the J-PARC, to deliver bunches of protons to both of beam transport lines, 3NBT and 3-50BT, a pulsed bending magnet (PB) [1] is operated. Bunches between K1 and K4 timing are bended to 3-50BT, and the other bunches through the PB to 3NBT after the magnetic field is fallen down. The rise and fall time of the pulsed bending magnet was designed as less than 40msec because the interval time of bunches is 40msec. However the residual magnetic field after K4 has been observed as equal to 0.27mrad kick angle at K5 as shown in Fig1. Therefore, bunches at K5, K6 and K7 have not been filled to avoid time depended beam orbit shift at the target of Material and Life Science Experimental Facility (MLF). If the residual field of PB is corrected, the production beam power for the MLF will be higher with K5, K6 and K7 bunches. To reduce the PB residual field, additional coils have been wound to poles of the PB, and a power supply has been installed. Results of the beam study by using the additional correction coil will be reported in this paper.