Vg Instruments Group Limited

Fisons Ltd.

Neil E Sanderson

Neil Bradshaw

Alan L Gray

Edward F Hall

David J Mills

Nigel Kinge

Christopher T Tye

David J Hall

Plasma sources mass spectrometry

High resolution plasma mass spectrometer

Plasma mass spectrometer

The invention comprises a mass spectrometer adapted for the determination of isotopic ratios which has several ion-collecting means disposed along its mass focal plane. Separate current amplifier means are provided for each ion collecting means and comprise an electrometer amplifying element, and an input resistor disposed in an inner box, itself disposed within a sealed evacuated housing. Means are provided for cooling the amplifier element to a temperature substantially below 20.degree. C. Means are provided for maintaining the temperature of at least the input resistor substantially constant. Cooling the amplifier element, typically to between 0.degree. and 5.degree. C., results in an unexpected reduction in low frequency noise which allows the time required to determine an isotope ratio to be reduced, thereby substantially increasing sample throughout.

Mass spectrometer including cooling for the ion collection amplifiers

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.

Glow discharge mass spectrometer

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Sandiway, United Kingdom

Neil E Sanderson