Local feedback experiment in the Taiwan Light Source

A highly-effective digital global feedback system has been developed to control closed-orbit error in the Synchrotron Radiation Research Center (SRRC). However, the beam orbit in SRRC is intrinsically so stable that a digital local feedback system may be preferred for some operating conditions. Consequently, a prototype digital local feedback loop has been developed and tested for suppressing orbit disturbances at the source point of a photon beamline. This prototype consists of a local orbit bump whose strength is dynamically controlled to preserve the beam trajectory. The measured bump response is used in this feedback system, and the controller uses a PID algorithm. Digital filtering is used to reduce the noise in beam position measurements. The hardware of the local feedback system is integrated with that of the global feedback system.