Li, G (reprint author), CAS, Inst High Energy Phys, Beijing 100049, Peoples R China.
The superconducting cryogenic system has been designed and deployed in the Beijing Electron-Positron Collider Upgrade Project (BEPC II). Process variables, including the pressure, level, flow and so on, are manipulated to get the liquid helium, two-phase helium flow and supercritical helium flow, which are used to cool down the three kinds of superconducting devices respectively. The system fully automates the superconducting cryogenic control with the structure of EPICS+PLC. EPICS is used to take charge of the process control, the logical control and the PID control loops whereas the low level interlocks of the pivotal equipments are run in PLCs to protect the superconducting device from damage.