METHOD AND APPARATUS FOR OPERATING A VACUUM INTERFACE OF A MASS SPECTROMETER

A method of operating a mass spectrometer vacuum interface, the vacuum interface comprising an evacuated expansion chamber downstream of a plasma ion source at atmospheric or relatively high pressure,the expansion chamber having a first aperture that interfaces with the plasma ion source to form an expanding plasma downstream of the first aperture and a second aperture downstream of the first aperture from the plasma for skimming the expanding plasma to form a skimmed expanding plasma; wherein the expansion chamber is pumped by an interface vacuum pump to provide an interface pressure in thechamber; the method comprising using a controller to automatically, or according to user input, control the throughput of the interface vacuum pump to control the interface pressure dependent on one or more operating modes of the spectrometer. A pressure gauge can be located in the expansion chamber and a feedback loop provided between the pressure gauge and controller. 一种操作质谱仪真空接口的方法，所述真空接口包括处于大气压或相对高压下的等离子体离子源下游的已抽真空的膨胀室