Electromagnetic valve for pulsed molecular beam

摘要

An electromagnetically operated valve for generating a fast, pulsed molecular beam is disclosed. Two axially aligned solenoids are mounted in a valve housing, the front end of which is closed by end plate having a central valve aperture. The solenoids are held in spaced apart relationship by a non-magnetic ring to define a gap between the faces of the two solenoid windings. A thin disc of magnetic material moves between the solenoid cores upon energization of first one and then the other of the windings. A small diameter non-magnetic tube extends from the center of the disc coaxially through one of the solenoid cores and terminates in a stainless steel tip which carries a valve head in the form of a short rod having a flat end. The tube is axially movable by the disc to move the valve head into and out of engagement with the end plate to close and open the valve aperture. The tube is surrounded by a metal bellows which serves to isolate it and the solenoids from a sample gas reservoir surrounding the valve head and formed by the end plate and the valve housing. The aperture in the end plate is a conical hole which serves both as a valve seat and as an expansion nozzle for the gas released by operation of the valve.PPThe two solenoid coils are driven by suitable multivibrators which produce timed pulses to drive one solenoid to open the valve and to drive the other solenoid to close the valve, with suitable switching circuitry being provided to operate the valve at a high rate of speed.