Experimental and Statistical Investigations on the Measurement of Very Low Ion Currents in Mass Spectrometers

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Abstract
Ion-electron converters with low background current have been applied for the investigation of residual gas mass spectra. From the abundance distribution of the secondary electrons, measured with scintillation and surface barrier detectors, counting losses can be determined for different ion masses. Ion currents as low as some 10−22 A are measurable. The corresponding error limits are considered by a statistical analysis including the background current. Criteria are given to distinguish a mass peak from the background within a definite error probability.