AN ION GAUGE, A MONITORING SYSTEM AND A METHOD FOR DETERMINING A TOTAL INTEGRATED CONCENTRATION OF SUBSTANCES HAVING SPECIFIC MOLECULAR WEIGHT IN A GAS SAMPLE

摘要

The invention relates to anion gauge10 for determining a total integrated concentration of a substance having a molecular weight falling into a pre-determined range of molecular weights in a gas sample, comprising an ionization region in a vicinity of the ionization source 1; an accelerator 2, 3, 4 for generating a flow of said ionized molecules I; a mass filter 8 for intercepting said flow for separating ions having the molecular weight falling into said range from said ionized molecules and a detector 7 for generating a signal representative of the total integrated concentration of such ions present in the gas sample. The invention further relates to a lithographic apparatus and a method for determining a total integrated concentration of a substance having a molecular weight falling into a pre-determined range of molecular weights in a gas sample.