Abstract

The J-PARC 3 GeV Rapid Cycling Synchrotron (RCS) delivers a 1-MW, high-intensity beam to facilities downstream. In such high-intensity accelerators, the operational beam intensity is limited to keep worker exposure to the residual dose within acceptable tolerances. Therefore, we continue to pursue accelerator commissioning that reduces beam loss. In order to achieve further high-intensity operation, the J-PARC accelerator system has been drastically upgraded over the past two years. As a result, it was found that beam loss decreased, whereas output power increased; the residual doses were kept at the same level or decreased in RCS. A malfunction of a collimator occurred in April 2016, and we replaced it to a spare duct in a hurry. The broken collimator was higher activated, but exposure to workers was kept within the acceptable level.

Highlights

  • The J-PARC 3 GeV Rapid Cycling Synchrotron (RCS) was constructed to deliver a 1-MW, high-intensity beam to the Material and Life Science Experimental Facility (MLF) and the Main Ring (MR) [1]

  • The J-PARC linac energy was upgraded to 400 MeV during the 2013 summer shutdown period [2], and the peak current of the ion source was increased to 50 mA during the summer shutdown period of 2014 [3]

  • We investigated the radio-activation of the foil chamber and found that the radio-activation source was the interaction of the injection and circulating beams with the charge-exchange foil [6]

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Summary

Introduction

The J-PARC 3 GeV Rapid Cycling Synchrotron (RCS) was constructed to deliver a 1-MW, high-intensity beam to the Material and Life Science Experimental Facility (MLF) and the Main Ring (MR) [1]. In a high-intensity proton accelerator such as RCS, beam loss, which constitutes just a small fraction of the beam, causes large doses of prompt radiation and serious radio-activation, which may cause malfunctions in the accelerator components and higher exposure doses to maintenance workers. The J-PARC linac energy was upgraded to 400 MeV during the 2013 summer shutdown period [2], and the peak current of the ion source was increased to 50 mA during the summer shutdown period of 2014 [3]. Due to these upgrades, necessary equipment for 1-MW operation has been prepared. We report the conditions of radio-activation and worker dose in the RCS after the accelerator upgrade

History of beam power and residual doses
Worker doses during the maintenance period of 2014
Malfunction of the ring collimator
Findings
Conclusion
Full Text
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