Associated Electrical Industries Limited

Thomas Oliver Merren

Sydney Evans

Ions are formed from an unknown substance in a first ion source of a double beam mass spectrometer and accelerated therefrom at a low accelerating voltage, e.g. 1kV or 2kV. Ions are formed from a reference substance in the second ion source and accelerated therefrom at a relatively high accelerating voltage, e.g. 8kV. The ion beams so formed pass through a common magnetic analyser to produce respective mass spectra. With pefluorokerosene as a reference substance producing a reference mass scale up to about 1000a.m.u., the mass spectrum of the unknown substance can be accurately calibrated (mass marked) up to 8000a.m.u. or 4000a.m.u. (with the above exemplary low accelerating voltages). Thus the invention enables the inherently very accurate chemical mass marking ability of a double-beam mass spectrometer to be scaled up along the mass scale of the unknown substance.

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Hale, United Kingdom

Thomas Oliver Merren