Fisons Ltd.

Vg Instruments Group Limited

Edward F Hall

Philip A Freedman

Neil E Sanderson

David J Hall

A multiple charged-particle detector system includes a plurality of charged-particle detector assemblies (10-12) which are each made up of a first arm (19-22) and a second arm (24-27) extending at an angle to each other. Charged particles (4-7) enter an aperture (14-18) at the entrance of the first arm (19-22) of each detector assembly (10-12) and strike a dynode (30-33) positioned at the intersection of the two arms causing electrons to be emitted by the dynode (30-33). Some of the electrons pass into the second arms (24-27) of the detector assemblies (10-12) and are detected by a continuous-dynode electron multiplier (35-38). The first arms (19-22) are narrower than the detectors (35-38), and the detector assemblies (10-12) are arranged in such a way that the minimum separation at which charged-particle beams (4-7) can be detected is determined by the widths of the said first arms (19-22) of the detector assemblies (10-12), and not by the widths of the detectors (35-38) themselves.

Multiple-detector system for detecting charged particles

There is provided a mass spectrometer adapted for the elemental analysis of a sample, especially a solid sample, comprising a glow discharge ion source which yields ions characteristic of the elements in the sample. The background spectrum produced by such a mass spectrometer is substantially reduced by cooling the ion source below 20.degree. C., and preferably below -100.degree. C., thereby increasing the sensitivity and the accuracy of the spectrometer. The cooling of the ion source is preferably accomplished by flowing liquid nitrogen through a heat exchanger disposed in good thermal contact with it.

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Winsford, United Kingdom

Edward F Hall