Abstract: An automatic nulling circuit applicable to small leak detection in vacuum chambers. A pressure sensitive, variable impedance element is connected as one branch of a bridge circuit, another branch of which comprises an adjustable impedance circuit. The voltage across the two branches are normally balanced by means of an amplifier circuit which amplifies any differential between the branch voltages, and a feedback circuit between the amplifier output and the adjustable impedance element. The amplifier and feedback circuits, however, introduce a time lag such that the two branches are unbalanced, resulting in an amplified output, in response to a changing sensed pressure. A filter circuit removes the effects of long term pressure changes, whereby the nulling circuit produces an output only for short term transients in the rate of pressure change, such as those associted with small leak testing.

Abstract: Laser emission from rare gas-halogen molecules, particularly krypton fluoride, is produced by a chemical reaction initiated by an efficient, high-power, high repetition-rate, fast electric discharge device transferring energy directly to a body of the gas in a laser cavity. The discharge device is of Blumlein parallel plate condensor/conductor type in which the condensor plates and their separating dielectric are uniformly compressed within an evacuated chamber by the force of the external atmospheric pressure.