摘要:
A fast-closing valve system has been provided which operates to protect a cyclotron from loss of vacuum and backwash of radioactive contamination when using intensely alpha-active actinide targets. The valve portion consists of a valve chamber adapted for mounting in a beam tube and having aligned ports on opposite sides through which the accelerated particle beam travels. A valve gate is slidably mounted in the valve chamber between the ports and normally urged into a seated position, closing the ports, by means of compression springs. The valve gate is held open by means of an electromagnet and, when the current to the electromagnet is suddenly shorted, the magnetic field rapidly collapses and the springs slam the valve gate into the seated position. The circuit controlling the actuation of the electromagnet uses a spark plug as a pressure sensor mounted in the beam tube, downstream of the valve and when a slight pressure rise in the beam tube occurs the spark plug fires triggering the control circuit which, in turn, shorts the electromagnet. A plurality of annular baffles are mounted in the beam tube to retard the shock wave from pressurized gas backwash in the case of an accident, such as a target rupture, allowing the valve to close before the gas reaches the valve assembly.