a) The common types of detectors in mass spectrometry are SEM, CEM and MCP. What is the meaning of these acronyms?
SEM: secondary electron multiplier
CEM: channel electron multiplier
MCP: microchannel plate (or multichannel plate)
b) What are the differences in ion detection with SEM, CEM, and MCP on one side and in FT-ICR on the other?
Ion detection with SEM, CEM, and MCP is destructive as the ions are impinging on a surface, but it is very sensitive due to high amplification factors of the ion current.
Detection in FT-ICR is based on the measurement of image currents, i.e., detection in FT-ICR means “listening to the circulating ions” and it is non-destructive.
c) What is cryogenic detection?
Cryogenic detectors, a rather special type of an ion counting detector for high-mass ions in TOF-MS have gained interest in the past. Cryogenic detectors measure the heat dissipated in the detector surface upon ion impact. This makes their response independent of ion velocity and allows extremely heavy ions (> 1.000.000 u) to be detected with good sensitivity. The first (and only) commercial cryogenic detector TOF instrument has been released in 2003 (Comet Macromizer, Flamatt, Switzerland).