Construction and Calibration of a Neutral Gas Spectrometer with Open Cathodeless Electron-impact Ion Source for Density Measurements in the Upper Atmosphere

H. Trinks

Jan 1973 · Air Force Cambridge Research Laboratories, Air Force Systems Command, United States Air Force

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Up to now, a reliable determination of the number density of atomic oxygen in the atmosphere by means of mass spectrometers has not been accomplished. Presumably, losses of O occur at the ion source walls and at the filament. Therefore, a mass spectrometer has been developed having an electron-impact ion source where the electrons are produced by a multiplier together with a UV lamp. To minimize the influence of impacts at the walls, the ion source was designed with a wide open geometry. The spectrometer was calibrated by means of a gas flow method with a gas flow of 50 liters/sec produced by a helium cooled cryopump. Neither oil nor mercury pumps were employed in the system. The calibration results are given, and the calculated mass discrimination curve is discussed and compared with that of a monopole spectrometer using an ion source with a hot filament.