Study of magnetic alloy cut-core for J-PARC MR

Nomura, Masahiro  ; Yamamoto, Masanobu   ; Shimada, Taihei ; Tamura, Fumihiko   ; Omori, Chihiro*; Toda, Makoto*; Hasegawa, Katsushi*; Hara, Keigo*; Yoshii, Masahito*

J-PARC 3 GeV RCS and Main Ring (MR) employ RF cavities loaded with Magnetic Alloy (MA) cores. The RF cavities in RCS employ un-cut cores and the RF cavities in MR employ cut cores to increase the Q-value. In this paper, we discuss the magnetic characteristics of cut cores. At first, we show the fundamental magnetic characteristics of cut core and the influence of leakage magnetic field. Next, we discuss the relation between Rp of un-cut core and cut core. At last, we show what parameters are effective to increase the cut core Rp. Rp is a key parameter to achieve a high field gradient for increasing the beam power.