A replaceable, electronically-isolated, MCP-based spectrometer detector cartridge with enhanced sensitivity is disclosed. A mass detector is electro-optically isolated from a charge collector with an 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 charge pulse. The light sensor is realized by any of a plurality of photo-responsive devices.