METHOD AND APPARATUS FOR SELECTIVELY PERFORMING CHEMICAL IONIZATION OR ELECTRON IONIZATION

摘要

An ion source includes structure having separate first and second ion volumes therein, and electron source structure having first and second portions that selectively supply electrons to the first and second ion volumes, respectively. The electron source structure has a first operational mode in which the second portion substantially prevents a supply of electrons to the second ion volume and in which electrons are supplied to the first ion volume under control of the first portion, and has a second operational mode in which the first portion substantially prevents a supply of electrons to the first ion volume and in which electrons are supplied to the second ion volume under control of the second portion.