Design of an optical cavity in the NIJI-IV for high output power

A new optical cavity system which efficiently takes out intense intracavity power of a storage ring free electron laser (SRFEL) in the visible and ultraviolet (UV) regions are planed. If a cavity mirror is started to rotate at the peak of an SRFEL macro-pulse to rapidly lead an SRFEL micro-pulse to the high transmission area, we can dump a part of the intracavity power sufficiently. A high-speed piezotranslator and a special mirror holder will realize this system, what is called cavity dump. The piezotranslator would make the optical cavity mirror rotate with the angular velocity of 2.52 × 10−6rad per one round-trip. In the case of NIJI-IV FELs, the output power of the micro-pulse would be estimated at about 7600 times around 488 nm and about 2700 times around 352 nm as strong as that in the normal operation.