Ion source for compact mass spectrometer and method of mass analyzing a sample

A mass spectrometer 20 includes an electron multiplier 30 for producing an electron avalanche 58 directed toward an ionization region 38. A sample 40 enters the ionization region 38 through a sample inlet 68. In the ionization region 38 the electron avalanche 58 collides with the sample 40 and produces ions 60. A start detector 56 detects the electron avalanche 58 and provides a start signal. The ions 60 exit the ionization region 38 and enter a flight region 26. The ions 60 flow through the flight region 26 and interact with a stop detector 42. The stop detector 42 generates a stop signal in response to being activated. A low pressure enclosure 22 encloses at least the electron multiplier 30 and the ionization region 38. The start and stop signals are supplied to an analysis system for determining the mass of the sample using time-of-flight mass spectrometry.U