Beam acceleration with full-digital LLRF control system in the J-PARC RCS

Tamura, Fumihiko   ; Schnase, A.; Nomura, Masahiro  ; Yamamoto, Masanobu   ; Hasegawa, Katsushi; Haga, Koichi; Yoshii, Masahito*; Omori, Chihiro*; Toda, Makoto*; Hara, Keigo*; Ezura, Eiji*; Anami, Shozo*; Takagi, Akira*

In the J-PARC RCS (Rapid Cycling Synchrotron) we employ a full-digital LLRF control system to accelerate an ultra-high intensity proton beam. The key feature is the multi-harmonic RF signal generation by using direct digital synthesis (DDS) technology. By employing a full-digital system, highly accurate, stable and reproductive RF voltages are generated in the wide-band RF cavities loaded by magneticalloy (MA) cores. The beam commissioning of the J-PARC RCS has been started in October 2007. The accelerators, the linac and the RCS, show good stability. The beam orbit and the longitudinal beam shape and phase are reproductive from cycle to cycle especially thanks to the stability of the linac energy, the RCS bending field and the frequency and voltage of the RCS RF. This reproductivity makes the beam commissioning efficient. We present the examples of the orbit signals and the longitudinal currentsignals. Also, we discuss the longitudinal beam control performance and future plans.