High-Vacuum Pumping Systems

Source of high-energy electrons, ion accelerator, magnetic/electrostatic analyser, detector and recorder, high vacuum pumping system. 

Fig. 3.20 Schematic diagram of a high vacuum pump system with optionai operation of a Roots pump or a diffusion pump...

The vacuum system must be able to attain the required pressures reliably despite these high gas loads. In the example shown, the system is evacuated with a combination of a backing and Roots pump. A diffusion pump along with a cold surface forms the high vacuum pump system. The cold surfaces pump a large portion of the vapor and volatile substances emitted by the plastic parts while the diffusion pump basically removes the non-condensable gases as well as the noble gas required for the sputter process. 

A very convenient way of detecting and measuring leaks is to use a tracer gas (such as He) and a selective tracer gas detector, such as a helium leak detector. In addition to the mass spectrometer, MSLD include a high vacuum pumping system of definite pumping speed. 

Isotope mass spectrometers typically cover the range m e 2—100. A high vacuum pumping system is required to maintain a sample inlet pressure of 10 torr and an analyser pressure of 10 torr. Both inlet and analyser components can be baked to 300°C to reduce the background spectrum. 

Split flow (leak detection) When part of the helium flow passes through the leak detector and part through the high vacuum pumping system. See also Full flow. 

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