Abstract: Ions in a chamber or space are detected using an electron multiplier operating at relatively low gain. The electron multiplier is placed in communication with the chamber, such as a chamber of a mass spectrometer, such that ions from the chamber enter the electron multiplier. A bias voltage applied to the multiplier sets the gain of the multiplier. By setting the gain at a relatively low value, the gain of the multiplier remains independent of chamber pressure, such that an accurate pressure measurement is obtained without calibration at a particular pressure or as a function of pressure.

Abstract: A preconcentrator for analyzing trace constituents in gases wherein a sample gas is introduced to a confined sorbent which thereafter is evacuated by a vacuum pump and a low-pressure carrier gas passes through the sorbent while it is desorbing, wherein the desorbed trace constituents are carried by the carrier gas to a detector that operates at low pressure such as a mass spectrometer. Because the mass of the carrier gas which carries the desorbed trace consituents to the detector is at a lower pressure and therefore has less density than the sample gas, the relative mass of trace constituents in the carrier gas is much greater than in the sample gas. The sample gas can be hot to assist desorption or a gas which reacts with trace constituents of interest to improve their detection.