High Sensitivity Mass Spectrometer Leak Detector

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Abstract
A new type of mass spectrometer ion detector is described and some of its applications discussed. A positive ion entering the detector is accelerated onto a thin metal foil where it releases secondary electrons, which are in turn accelerated onto an organic scintillator viewed by a photomultiplier; this measures the total ion beam. Those ions which penetrate the foil sufficiently release secondary electrons from the back of the foil, and these are detected in a similar way. The transmission properties for many light ions has been investigated and it has been found that the foils have high transmission for helium ions and high rejection for ``air'' ions. The results obtained can be applied toim proving the sensititivity of leak detectors, appearance potential measurements, and the analysis of small quantities of deuterium in hydrogen.