Commissioning of the SuperKEKB final focusing superconducting magnet cryogenic systems

Abstract

The 55 SuperKEKB final focusing superconducting magnets are assembled into two cryostats, located at the left side and the right side of the accelerator interaction point, respectively. The two cryostats are cooled by sub-cooled liquid helium at 0.16 MPa with two independent refrigerators of about 250 W cooling capacity. From August 2016, the two cryostats were installed into the accelerator beam line and were connected with their own sub-coolers and refrigerators. As cryogenic systems, commissioning was carried out to cool down the cryostats, to excite superconducting magnets, and to test system interlock protections against some emergencies. This paper introduces the cryostats and cryogenic systems, and the commissioning processes. The cryostat heat loads were measured and the results are presented in this paper.