Beam Position Monitor for Undulator by Using SR Monitor Technique

A beam position monitor for the undulator by using the optical SR monitor technique has been tested in the Photon Factory. A visible SR in far tail of the undurater spectrum is extracted by a water-cooled beryllium mirror. The extraction mirror has a hole in the center for passing through the central peak of the undulator radiation. Extracted visible light in large opening angle has same optical axis of the undulator radiation, because of it is a far tail of the spectrum of same radiation. We applied focusing system to observe a beam position in the undulator through an optical image of beam. The results show us this method is applicable to monitor a position of beam in the undulator, and gap change of undulator has no effect for the beam position monitoring.