AN AUTONEUTRALIZING NEUTRAL MOLECULAR-BEAM GUN

A high-energy (up to 28 keV) neutral molecular beam gun has been developed and put into routine use that takes advantage of the autoneutralization properties of the sulfur hexafluoride anion for the production of high-energy sulfur hexafluoride neutral molecules. The anions are produced in an electron-capture source, accelerated, and focused in a lens assembly designed to minimize residence time, allowed to drift at their terminal velocity for a suitable distance during which up to 30% auto-eject an electron, and all remaining charged particles are electrostatically skimmed, resulting in a focused neutral beam. Rasterable neutral beams focused to a 5-mm spot size up to 3 m from the source have been produced with beam currents up to 40 pA equivalent. Spot sizes of 1 mm can be produced with intensity levels of a few picoamperes equivalent.