Once separated by mass analyzer, ions reach ion detector which generates a current signal from incident ions. The most commonly used detector is the electron multiplier.3 different types of detectors: Electron multipliers, dynolyte photomultiplier, microchannel plates.

Electron multiplier

A conversion dynode is used to convert either negative or positive ions into electrons. These electrons are amplified by a cascade effect in a horn shape device, to produce a current. This device, also called channeltron, is widely used in quadrupole and ion trap instruments.

Dynolyte photomultiplier

Ions exiting the quadrupole are converted to electrons by a conversion dynode.These electrons strike a phosphor which when excited, emit photons. The photons strike a photocathode at the front of the photomultiplier to produce electrons and the signal is amplified by the photomultiplier. The photomultiplier is sealed in glass and held under vacuum. This prevents contamination and allows the detector to maintain its performance for a considerably longer period than conventional electron multipliers.

Microchannel plate

Most TOF spectrometers employ multichannel plate (mcp) detectors which have a time response < 1 ns and a high sensitivity (single ion signal > 50 mV). The large and plane detection area of mcp's results in a large acceptance volume of the spectrometer system. Only few mcp channels out of thousands are affected by the detection of a single ion i.e. it is possible to detect many ions at the same time which is important for laser ionisation where hundreds of ions can be created within a few nanoseconds. dynode phosphor photomultiplier.