On June 3, the China Spallation Neutron Source (CSNS) Project invited experts to test the CSNC/RCS Low Level Radio Frequency (LLRF)

the on-stie test

prototype at the Institute of High Energy Physics (IHEP). After witnessing an on-site test and hearing the design and test reports, the expert group concluded that CSNC/RCS LLRF prototype met the strict physical design requirements, its structure and technology reached the advanced level.

The LLRF control system is a complex control system with multi-control loops. In the prototype R&D, the key technical issues of the fast tuning of RCS RF system, ferrite-loaded cavity nonlinear compensation and self-adaptive feed-forward control strategy for the cavity feedback control loops have been solved through the study and development of control arithmetic by FPGA logic programming.

The RCS RF system prototype can operate stably in the rapid cycling pattern mode with a repetition rate of 25Hz and duty factor of 50%, and passed a high power reliability test of 24 hours successfully. The cavity gap voltage ramping and the RF frequency sweeping range can reach to from 1.29~ 10.3kV and 1.022~2.44MHz respectively during 20ms sweeping operation. The control accuracy of the RF cavity voltage amplitude loop and RF system tuning loop all can meet the requirement of the design values.

The prototype of the RCS LLRF control system adopted a full digital embedded control system architecture based on CPCI bus. The LLRF control system for the CSNS/RCS uses the CPU modules of CPCI 6020 running the VxWorks operating system. The system integration software including EPICS device driver and device support have been completed corresponding to the RCS LLRF embedded control system. The greater real data transmission bandwidth of 214MB/s can be achieved. The EPICS control system can realize the real time monitoring and managing for the RCS LLRF control system.