This is an all-metal, remotely actuated UHV valve that seals to isolate the Storage Ring from any vacuum breach in the downstream transport piping. The closing time of this valve is usually 1-2 seconds. However, it cannot accept the heat load from the photon beam and therefore has to be interlocked to close only when beam is NOT present or the photon shutter (PS1) is closed. Closure of the slow valve occurs after the fast valve is closed. This action also helps to retard the progression of a pressure wave upstream in the event of a vacuum breach somewhere downstream.