OPERATIONAL EVALUATION OF ULTRAHIGH-VACUUM PROTECTION SYSTEMS FOR INTENSE-PHOTON-FLUX WIGGLER BEAMLINES

The ultrahigh-vacuum (UHV) protection system at the 2.5 GeV synchrotro n radiation source (positron storage ring) at the Photon Factory allow s the intense-photon-flux wiggler beamlines to operate safely during s ynchrotron radiation experiments for a long time. There are six high-p ower wiggler/undulator beamlines that provide intense photon-flux beam s to the experimental hall. In the case of a possible instantaneous va cuum failure at the experimental hall, the intense photon-flux radiati on from the wiggler could cause a meltdown of the titanium-alloy fast- closing valve. The authors have developed a UHV protection system. Upo n a vacuum failure, the protection system can dump the positron beam b y turning off the RF power in the four RF klystrons (150 kW maximum), and then initiate a blade closure of the fast-closing valve. In this p aper, the operational performance of the vacuum protection system for the intense-photon-flux wiggler beamlines is evaluated and discussed r egarding the actual vacuum deterioration downstream of a beamline at t he experimental hall.