Energy feedback system for the PLS-II linac

The upgraded Pohang-Light-Source (PLS-II) was opened to the public in 2012. Among many improvements of the PLS-II, a top-up operation was one of the highlights of them, and the stability of the electron beam was improved significantly. For the top-up operation, a stable injection from the linac to the storage ring was critically important, so that an energy feedback system was introduced to reduce the energy jitter of the linac electron beam. The result of the feedback system was successful and the measured energy jitter was less than ±0.1% (rms). In this work, the details of the energy feedback system are presented. It includes the setup for the energy feedback system, measurement results in the optimization process, and the future work for a better performance.