Beam momentum spread measurement using two beam position monitors at Xi’an Proton Application Facility

Abstract

Beam momentum spread is a key parameter of the linac injector at the Xi’an Proton Application Facility (XiPAF), China. A momentum spread measurement method using multiple beam position monitors (BPM) was successfully developed recently at Tsinghua University, China. This work is an extension of the method. The original method requires at least three BPMs to perform the measurement, and the BPMs should be installed far from the accelerator exit, causing long measurement space and low BPM signals. The new method only needs two BPMs, and a much shorter measurement space is proposed for the low-current linac in this paper. The new method was successfully tested at XiPAF. The measured rms momentum spread at the Radio Frequency Quadrupole exit is (5.05 ± 0.06) × 10−3, which agrees well with the spectrometer measured value (5.09 ± 0.05) × 10−3.