Improvements relating to mass spectrometers

1,149,632. Mass spectrometers. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. 6 June, 1966 [11 June, 1965], No. 24770/65. Heading H1D. A mass spectrometer, e.g. of the doublefocusing type, has variable slits at the ion source and collector ends of the beam path whereby the instrument may be alternately adjusted for high and low resolution, preferably automatically, in successive scans of the mass spectrum. Provision is also made by means of a selector switch for providing continuous high resolution or continuous low resolution. With magnetic scanning the spectrum may be observed during the decay or recovery sweeps of the magnetic flux. The slits may comprise electrostatic lenses as in Specification 759,917 or mechanically varied apertures such as that, 21, formed between two blocks 20 which are acted upon by a motor driven rod 23 against return springs 24. The mechanism includes limit stops for the action of the rod 23 and a control circuit including limiting switches.