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systems. Covering the range 1-200 a.m.u., it has 2 novel features: a cylindrical ceramic quadrupole electrode system made from a single piece of material and bakeable to 400ยฐC (200ยฐ(3 in operation), and a constant-sensitivity facility that corrects the Quadruvac for the mass being analysed. The constituents of a gas mixture are determined qualitatively (mass number) and quantitatively (partial pressure) according to their pressure ratio, which is proportional to the number density ratio of the molecules present in the mixture.
Two types of gauge head are offered : one with a Faraday cup measuring partial pressure down to 1 x 10 -11 mbar, and an alternative head with Venetian blind photo-multiplier for partial pressures down to 1 x 10 -13 mbar. The ion source and mass separation system are the same for each gauge head, and the heads are easily demountable for cleaning and reassembly.
The nude axial ion source is small and has high permeability for residual gases, and a special configuration of anode cage prevents photons reaching the ion collector. A non-burn-out ring-shaped hot cathode surrounds the anode, and is designed to be easily changed.
The usual recording instruments can be connected to the output of the Q 200 ; oscilloscope or chart recorder, or data-processing system. Although the instrument normally operates at pressures below 4 x 10 -3 mbar, a pressure convertor offered as an optional extra, permits use at atmospheric pressure.
๐ SIMILAR VOLUMES
A range of instruments have been available for several years for use in the analysis of the spectra of gases and liquids. This paper describes recent work in the area of microprocessor enhancement of those machines. It examines, in particular, an application involving the quadrupole mass spectromete