โ Scribed by Birkinshaw, Keith
No coin nor oath required. For personal study only.
Spatial dispersion of ions in one dimension is a well established means of analysing ion mass and focal plane detectors (FPDs) allow ions of a wide range of masses to be recorded simultaneously. This paper is concerned with the principles governing the performance of FPDs and the types of FPD available. It is focused on magnetic sector mass spectrometry but is relevant to all applications in which spatially dispersed particles can be detected using a microchannel plate electron multiplier, e.g. ions, photons of wavelength AE200 nm, electrons and energetic neutrals.
Although it has proved possible to produce mass spectra with a high resolution, this has not been matched by an ability to detect them efficiently. Given that highly resolved spectra are available at the detector but are inaccessible efficiently, it is in the development of high-performance FPDs where there are enormous gains in efficiency to be achieved. Limitations of FPD performance of two fundamental types are discussed : the position of impact of an ion on the FPD cannot be measured exactly, and the upper and lower count rates of the FPD are both restricted. These limitations are not simply characterized but are sometimes determined by the electron multiplier stage, sometimes by the properties of the array and sometimes by the data acquisition system.
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