A Needle Valve Type of Variable Gas Leak for Mass Spectrometers

A high vacuum needle valve may be used as an adjustable leak for regulating the flow rate of gas samples to a mass spectrometer, when the valve is equipped with a wedge and lever system providing very sensitive control of the needle position. Flow through the leak is molecular at spectrometer pressures, but mass flow may be secured by inserting a capillary tube between the sample and the leak. The leak may be closed completely, thereby simplifying the design of the sample inlet system.