Dependence of charge-exchange efficiency on cooling water temperature of a beam transport line

Kazami Yamamoto,Kazuaki Suganuma,Yoshio Yamazaki,Kota Okabe,Masahiro Yoshimoto,Takamitsu Nakanoya,Katsuhiro Moriya,Shuichiro Hatakeyama,Pranab Kumar Saha,Kosuke Fujirai

doi:10.1140/epjti/s40485-021-00067-6

Abstract

The 3-GeV Rapid Cycling Synchrotron at the Japan Proton Accelerator Research Complex supplies a high-intensity proton beam for neutron experiments and to the Main Ring synchrotron. Various parameters are monitored to achieve a stable operation, and it was found that the oscillations of the charge-exchange efficiency and cooling water temperature were synchronized. We evaluated the orbit fluctuations at the injection point using a beam current of the injection dump, which is proportional to the number of particles that miss the foil and fail in the charge exchange, and profile of the injection beam. The total width of the fluctuations was approximately 0.072 mm. This value is negligible from the user operation viewpoint as our existing beam position monitors cannot detect such a small signal deviation. This displacement corresponds to a 1.63 × 10− 5 variation in the dipole magnetic field. Conversely, the magnetic field variation in the L3BT dipole magnet, which was estimated by the temperature change directly, is 4.08 × 10− 5. This result suggested that the change in the cooling water temperature is one of the major causes of the efficiency fluctuation.

Highlights

The 3-GeV Rapid Cycling Synchrotron (RCS) of the Japan Proton Accelerator Research Complex (J-PARC) was constructed to supply a 1-MW, high-power proton beam to the Main Ring (MR) synchrotron and Material and Life science experimental Facility (MLF) [1]
From the above considerations, it was found that the injection beam orbit can be distorted by the fluctuation in the cooling water temperature, which would result in a 0.072 mm displacement of the injection point
We carried out the fast Fourier transform (FFT) analysis on these data around the frequency range of the temperature oscillation; we did not find any clear peak in the spectra

Summary

Introduction

The 3-GeV Rapid Cycling Synchrotron (RCS) of the Japan Proton Accelerator Research Complex (J-PARC) was constructed to supply a 1-MW, high-power proton beam to the Main Ring (MR) synchrotron and Material and Life science experimental Facility (MLF) [1]. The RCS accelerates the proton energy from 400 MeV to 3 GeV at a repetition rate of 25 Hz. The RCS accelerates the proton energy from 400 MeV to 3 GeV at a repetition rate of 25 Hz While operating such a high-intensity hadron accelerator, the most important aspect is the reduction of the beam loss around the accelerator to maintain a hands-on maintenance condition. A major cause for the beam loss is a halo, generated by the nonlinearity of the space charge force. To mitigate this space charge effect, the RCS adopts a painting injection scheme for the injection process in the transverse and longitudinal phase spaces [2]. In the injection beam-painting process, to achieve an arbitrary distribution in the transverse phase space, the injection beam orbit

Methods

Results

Conclusion