Performance of a microchannel plate ion detector in the energy range 3-25 keV

The performance of a double, chevron-mounted, microchannel plate ion detector of an atom-probe instrument has been studied using 3-25 keV He + , Ne + and Ar + ions. Pulse height distributions were recorded and the results indicate that the gain of the detector is strongly dependent on the ion energy. This energy dependence was found to be related to the secondary electron yield in the ion-channel-wall collision. However, the detection efficiency in atom-probe operation need not be affected by variations in mass and energy if an appropriate noise discrimination level is enforced and provided the ion energy exceeds approximately 5 keV.