ON THE PERFORMANCE OF A MICROCHANNEL PLATE DETECTOR USED FOR ATOM-PROBE ANALYSIS

The dependence of the detector gain and the detectivity on ion energy and detector bias voltage has been investigated. It is shown that the detectivity is not constant at ion energies below about 10 keV. For a given charge state the gain and thus the detectivity can be kept constant by tuning the bias voltage to the evaporation voltage. The main advantage of such a system is that it ensures a high detectivity for singly charged ions at low evaporation voltages, the main disadvantage being that a slightly lower average detectivity is obtained at high evaporation voltages.