Injecting painting improvements in the J-PARC RCS

Kato, Shinichi; Harada, Hiroyuki  ; Hotchi, Hideaki  ; Saha, P. K.   ; Okabe, Kota  ; Takayanagi, Tomohiro   ; Horino, Koki; Ueno, Tomoaki; Tobita, Norimitsu*; Kinsho, Michikazu  

In the J-PARC 3GeV RCS, the injection painting is essential method for the reduction of the space charge force. In this method, the H beam from Linac is arranged on the large phase space area of the ring orbit during multiple turns. To implement this method, painting magnets form the time variable beam orbit. Therefore, the precise output current control of the magnet power supply is required. Because the power supply controlled by mainly feedforward signal is operated, we developed the iterative tuning method for the optimum feedforward parameter determination. As a result, we could reduce the tracking error of the current compared to before. Furthermore, to improve the accuracy of the painting area size, we applied the output readjustment additionally. Because the current monitor value of the power supply was different from the actual magnetic field due to the delay in the circuit and the leakage field, we corrected the tracking of the current based on the measured painting area size determined by the analysis of the measured COD. As a result, we achieved the precise injection painting. This talk presents these improvement results of the injection painting in the RCS.