The construction of a Dempster type mass spectrometer, its use in the measurement of the difussion rates of certain alkali metals in tungsten

Details concerning the design and performance of a conventional l80° mass spectrometer are given. The operation of a new type of high frequency positive ion source is discussed and its characteristics are compared with two conventional ion sources, the hot filament and electron-impaction source. Observations on the decay of positive ion emission from heated tungsten filaments have been interpreted in terms of a diffusion process. Analysis of these observations has given values for the diffusion constants of potassium and sodium in tungsten