Evaluation of a microsphere plate detector for an orthogonal acceleration matrix-assisted laser desorption/ionisation time-of-flight mass spectrometer

摘要

A single 70 mm diameter microsphere plate (MSP) detector was evaluated in an orthogonal acceleration time-of-flight mass spectrometer fitted with a matrix-assisted laser desorption/ionisation source. The ion energy of the spectrometer was approximately 20 kV. The results indicated that the detector performance was excellent, for a single plate device, in terms of background count-rate, temporal characteristics of the pulses and the gains for single ions. A background count rate was observed to be less than 1 count s~(-1) cm~(-2) and the single-ion pulse width was about 800 ps at half height. The plate displayed a gain in the range 1 * 10~6 to 3 * 10~6 for all masses tested. The single ion gain measurements showed no significant decrease with mass while the summed signal intensity (total observed counts) decreased strongly at high mass. The gain distribution data were interpreted in conjunction with this observation to indicate that the detector efficiency was poor for high mass ions.