Reagent gas flow control for an ion trap mass spectrometer used in the chemical ionization mode

摘要

A reagent gas flow control system for use with an ion trap mass spectrometer is shown. The reagent gas flows from a source (5) through a first gas flow restrictor (70) connected to the inputs of second (80) and third (90) gas flow restrictors. The output of the second restrictor (80) is connected to the ion trap (10) where reagent gas is used, and the output of the third restrictor (90) is connected to a vacuum pump (20), which may be the roughing pump used by the ion trap. At least one of the three restrictors is a variable restrictor. The configuration of the present invention allows the use of simple and inexpensive parts to provide exacting flow control.