The cryogenic control system of BEPC

A superconducting cryogenic system has been designed and deployed in the Beijing Electron- Positron Collider Upgrade Project （BEPC II ）. The system consists of a Siemens PLC （ST-PLC, Programmable Logic Controller） for the compressor control, an Allen Bradley （AB） PLC for the cryogenic equipments, and the Experimental Physics and Industrial Control System （EPICS） that integrates the PLCs. The system fully automates the superconducting cryogenic control with process control, PID （Proportional-lntegral-Differential） control loops, real-time data access and data storage, alarm handler and human machine interface. It is capable of automatic recovery as well. This paper describes the BEPC 11 cryogenic control system, data communication between ST-PLC and EPICS Input/Output Controllers （IOCs）, and the integration of the flow control, the low level interlock, the AB-PLC, and EPICS.