To provide a replaceable and electronically-insulated micro channel plate electron multiplier-based spectrometer detector cartridge with enhanced sensitivity.

A mass detector is electro-optically isolated from a charge collector with the electron multiplier for converting a charged particle into a multiplicity of electrons and a scintillator for converting the multiplicity of electrons into a multiplicity of photons. A light sensor is provided to convert the multiplicity of photons back into electrons, which are summed into a charged pulse. The light sensor is realized by any of a plurality of photo-responsive devices.