BPM Design and Test Result of Xi’an Proton Application Facility

In the design of Xi’an Proton Application Facility (XiPAF), there are 6 beam position monitors (BPMs) installed in medium energy beam transport line to measure beam position and phase. Resolutions of position and phase measurement should be better than 0.1 mm and 1°, respectively, and accuracy of absolute position measurement should be better than ±0.5 mm. The effects of electrode length and opening angle on BPM resolution were analyzed theoretically. CST simulation was then performed to obtain the optimum parameters. The design resolution reaches 24.5 μm after optimization. The measured electrode capacitance, inter-electrode coupling and sensitivity of the BPM prototype agree with the designed value. Horizontal and vertical offsets between BPM mechanical center and electric center are （0.04±0.05） mm and （-1.53±0.05） mm, respectively, measured by a rotation method. The prototype was installed in the high energy beam transport line of Tsinghua University Compact Pulsed Hadron Source （CPHS) to test its performance. The test results show that resolutions of position and phase measured by XiPAF BPM are better than 60 μm and 0.74°, respectively, and accuracy of absolute position measurement is ±0.35 mm. The prototype satisfies the requirements of XiPAF.