Pneumatic fast-closing valve for synchrotron radiation beam lines at the photon factory

A fast-closing valve system has been designed and fabricated in order to protect the vacuum of the synchrotron radiation beam line and that of the 2.5 GeV storage ring from a sudden vacuum failure at the downstream end of the beam line. Upon the detection of a failure the valve closes within 11.9 ms by pneumatic pressure on a drive piston in a cylinder. Within the last 3.7 ms of the closing time the downward movement of the blade is decelerated so as to reduce the closing shock. A hard TiN ceramic membrane is coated on the surface of the titanium blade. On the surface of a stainless steel aperture, an Al₂O ₃-TiO₂ ceramic membrane (less hard than TiN) is coated in order to attain low conductance and smooth movement of the blade. This ensures a low leak rate of 0.135 torr l/s and a long life cycle of the mechanism (more than 8000 times)