TUBLA03
J-PARC, KEK & JAEA, Ibaraki-ken, Japan
KEK, Ibaraki, Japan
Kyoto University, Kyoto, Japan
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
One of the present obstacles for intensity upgrade of the J-PARC Main Ring is transverse collective instability. We have been developing so called intra-bunch feedback system and in operation during injection flat bottom since last year. But recent beam intensity upgrade push us to improve further the system, namely feedback during acceleration. The revolution frequency changes about 2% and the synchronous phase varies 0 - 26 degree during acceleration from 3 to 30 GeV in the MR. The delay in the feedback loop is changed stepwise triggered by external pulses. We are examining quick trigger timing determination by matching the bunch shape in the controller ("iGp12") to the one from the exciter (kicker) and estimating differences of slice markers in time. This method is time saving, which is important because of a limited machine tuning time. We will report present status of the feedback during acceleration.
