ION SOURCE FOR A MASS ANALYSER AND METHOD OF PROVIDING A SOURCE OF IONS FOR ANALYSIS

摘要

An ion source for a mass spectrometer operating at a low pressure has an atmospheric pressure sample ioniser which provides a sample flow containing desired sample ions. These ions are usually entrained with undesired gas and droplets. An interface chamber is held by a vacuum pump at a pressure between atmospheric and the operating pressure of the mass spectrometer. Sample ions with entrained gas are collected through an entrance orifice forming a stream of gas into the interface chamber. Sample ions exit the interface chamber through an exit orifice to the mass spectrometer. The interface chamber disrupts the stream of gas entering the interface chamber to provide a dead region having no net gas flow direction and the exit orifice is located in this dead region. The exit orifice should have no line of sight path to the entrance orifice or should be at least 30.degree. off the flow axis of the stream entering the interface chamber through the entrance orifice. A flow disrupting pin is located in the interface chamber to disrupt the flow of the stream of gas entering through the entrance orifice.