A desktop supersonic free-jet beam source for a scanning helium microscope (SHeM)

A simple design for an inexpensive, compact, desktop-sized helium free-jet beam source is described. The apparatus, which is Campargue-like in design and utilizes mostly off-the-shelf parts, is capable of producing a centreline intensity of 1.2 × 1019 atoms per second per steradian. The beam performance was investigated using a conventional ion gauge and a stagnation detector, with the latter being used to produce beam flux profiles. The profile of the macroskimmed beam has been experimentally demonstrated to be strongly Gaussian. (paper)