Stabilization of HEPS linac microwave system

The linac of the High Energy Photon Source has been commissioned. The low-level RF (LLRF) control system for the linac has been developed using MicroTCA.4-based technologies to maintain high stability of beam energy and energy spread.

I–Q demodulation and proportional–integral algorithms are used in the LLRF feedback loops. In order to mitigate the effect induced by the variations of the environment of the controller and the temperature of the coolant water, compensations are implemented in the feedback loops.

The beam energy of the HEPS linac can be stabilized in a level of better than 0.02% with the help of the LLRF system.

The LLRF system of the HEPS linac has been working stably since March 2023. Multiple effects have been mitigated, yielding better than 0.3 \(\mathrm {^o}\) ${}^{\mathrm{o}}$ and 0.6% of peak-to-peak stability of the phase and amplitude of the microwave system, respectively.