Status of SuperKEKB vacuum system at initial stage of Phase-3 commissioning

Abstract

The SuperKEKB is a high-luminosity electron-positron collider, and its Main Ring with a circumference of 3016 m is composed of the high-energy ring (HER) for 7.0 GeV electrons and the low-energy ring (LER) for 4.0 GeV positrons. Phase-3 commissioning of the SuperKEKB commenced in March 2019, in which the Belle II experiment started taking data with a fully instrumented detector. Prior to Phase-3 commissioning, in the Main Ring, the countermeasures against the problems such as overheating of the vacuum components found in previous commissioning were taken, and new beam pipes and components were installed. So far, the vacuum system of the SuperKEKB has been working generally well. No serious problems have been observed and vacuum scrubbing in the arc sections progressed smoothly. We will report the status of the SuperKEKB vacuum system in Phase-3 commissioning.