Experience with the ultra-high-vacuum protection system for the synchrotron radiation beam lines with high-power wigglers/undulators at the Photon Factory

There are six high-power wiggler/undulator beam lines at the 2.5-GeV synchrotron radiation source at the Photon Factory. In the case of an instantaneous vacuum failure at such a beam line, a normal Fast-Closing-Valve (FCV) system is incapable of functioning to protect the Ultra-High-Vacuum (UHV) of the beam lines and the synchrotron radiation source, since a meltdown of the titanium-alloy FCV is caused by intense photon flux radiation. To avoid such a case, a dedicated UHV protection system has been built where all FCV systems for the high power beam lines have been linked, using high-speed communication links to RF klystrons to allow the FCV systems to initiate blade closure after dumping the positron beam by tuning off the RF power. In this paper, experience with the UHV protection system for the wiggler/undulator beam lines is discussed.