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Investigation by simulation of the influence of vacuum reduction on time of flight mass spectra

Mass spectrometry is an important technique for environmental monitoring, especially for gaseous substances as e.g. in air pollution monitoring. Devices using a certain technique of this family, time of flight mass spectrometers, have a very high selectivity, a very good sensitivity in the ppm range, but a quite large device footprint also due to the size of necessary vacuum pumps. It is a thus very actual goal to have a gas analyzer with the same positive characteristics as a time of flight mass spectrometer, but at smaller size. Any successful size reduction would have to include the vacuum pumps, which normally would then lead to a reduction of the vacuum inside the device. Here we analyzed the influence of a vacuum reduction on the device characteristics (signal intensity, resolving power) with help of finite element method studies in order to find out how much the pressure can be increased in standard time of flight mass spectrometers without compromising the good performance normally obtained.