Development of a fast closing valve system

A fast closing valve is usually connected to a beam line branched from an electron storage ring. It protects the ultra-high-vacuum (UHV) system against inrushes of air, which may accidentally occur at a measuring station located at the down stream of the beam flow. The simplest system of a fast closing valve consists of a vacuum pressure sensor, a fast closing valve (FCV) and a system controller. These components of a FCV system are based on some fundamental technologies, for instance, extremely quick responsive measurements of vacuum pressure changes, rapid conversions of input singnals into outputs, transmissions of the signals in noisy circumstances, quick actions of the mechanism, characteristics of low leak rate, reliability and long life of the system. Some of these are common and useful technologies for fusion devices, also. The authors have developed two types of fast closing valve systems. The closing time guaranteed is 50 ms and 10 ms respectively for the nearly same aperture size of 150 x 15 mm. In this paper, the 10 ms FCV system is mainly described. Materials of the valve are non magnetic, and have low outgassing rates and low damage rates for synchrotron radiation (SR). The baking temperature is allowed to be 2000C. The leak rate characteristics are kept within about 0.1 Torr.lit/sec. (1.33 x 10-2 Pa m3/sec.), even after closing operations of 1000 times