A System for monitoring of the transverse injection error and betatron tune in J-PARC MR

Hatakeyama, Shuichiro; Toyama, Takeshi*; Tejima, Masaki*

The beam commissioning of J-PARC MR (Main Ring) started in 2008. The current beam power of the user operation is 40 kW - 70 kW which corresponds 1/10 of the designed value of 1st stage. One of the hurdle to clear for the power up is the beam loss at the injection. A candidate of the origin of the injection beam loss is the error of bending angles of RCS extraction magnets and MR injection magnets, therefore it is required to monitor continuously the transverse injection error. The transverse injection error can be calculated using beam bunch positions at the injection. For this purpose a dedicated digitizer is used to acquire the waveform of BPM. It is also monitored the betatron tune using the same digitizer. Processing the injected 93 turns beam bunch positions by FFT it is realized the continuous monitoring with 3.52 s operating cycle. When determining the beam bunch position, the digital-high-pass filtering is adapted to the waveform of BPM to remove the slow component of noise.