Advanced undergraduate experiments in vacuum physics and mass spectrometry

A comprehensive high‐vacuum system has been set up and operated in an advanced undergraduate laboratory for students majoring in physics and microelectronics. The aim of the experiment is to provide the students with both practical experience and basic theoretical understanding of the production and measurement of low pressures. The students measure the pumping speed of a rotary forepump and of an oil diffusion pump, as a function of pressure, using procedures adopted by the AVS. A hot‐cathode ionization gauge and a thermocouple gauge are calibrated against a McLeod (absolute) manometer for several gases. The compositions of ambient air, of an isotopic mixture of neon, and of the residual gases in an oil‐diffusion‐pumped system are determined with the aid of a mass spectrometer. The influence of a liquid‐nitrogen‐cooled surface is assessed. Helium leak detection is demonstrated, and the response and sensitivity of the mass spectrometer as a leak detector are evaluated