Performance of a micro-channel plates position sensitive detector

The absolute detection efficiency of large area micro-channel plates (MCPs) detectors has been measured with 6Li+ and 23Na+ ions in the 0.5-7.5 keV energy range. Two detectors of 47 mm and 83 mm active diameter have been tested. They consist in a pair of MCPs mounted in a chevron configuration with delay line anodes for position readout. The efficiency saturates above 3000 eV, reaching a value of 52.3(3)%, consistent with the MCPs geometry. The behaviour of the efficiency with respect to the ion kinetic energy is ascribed to the electronic threshold, through a detailed analysis of the collected charge distribution. The efficiency dependence on the ions impact position and incidence angle has also been studied. A loss of efficiency has been observed in the vicinity of the MCPs bias angle, which can be avoided if a large post-acceleration field is created in front of the MCPs. Finally the study of a position calibration is presented. A position resolution of 110(26) μm has been achieved.