Development of EPICS Enabled Analog I-Q Based Low Level RF Control System

The RF system is one of the important parts of Linear Accelerator. The RF power is responsible for the acceleration of the ion beam to higher velocity. The phase mismatch between RF voltage and ion beam may result in transmission losses. The low level RF (LLRF) control system plays an important role in maintaining the proper phase and amplitude of the RF voltage inside the accelerator cavity. In VECC, an I-Q based LLRF control system with embedded EPICS [1] control architecture is designed and developed for 37.8MHz RF cavities of Radioactive Ion Beam facility. The system is designed using ARM based SBC interfaced with external DAC and ADC. I-Q modulator and demodulator modules are developed in-house. The embedded EPICS input-output controller (IOC) is designed for acquisition of I and Q data from I-Q demodulator module through ADC, executing PID algorithm and production of desired I and Q voltages to I-Q demodulator module through DAC. At the same time, the IOC broadcast several control and monitoring parameters to the channel access clients e.g. operator interface, data archiver etc. The detail design and functional testing of the system is described in this paper.