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Studies of supersonic beam formation at low temperatures for a polarized helium 3 ion source Vyse, Robert Norman

Abstract

The formation of a molecular beam using a miniature supersonic nozzle source is discussed. The results of operation at room, liquid nitrogen and liquid helium temperatures of a supersonic nozzle system designed for use in a polarized helium³ ion source are presented. It is shown that helium⁴ beam intensities at 4.2ºK are approximately 1/8 of those at 300ºK. Factors upon which the beam intensity depend have been investigated experimentally and it is found that at room temperature and a distance of 16cm from the skimmer a heliun⁴ beam intensity of 3x10¹⁶ molecules/cm²/sec is attainable under certain circumstances. This beam intensity is an improvement by a factor of 10 over the original performance of the nozzle source. Assuming a 40% transmission through the magnet and a 0.25% ionization efficiency an ion current of 0.02 microamperes is estimated for the polarized helium³ ion source.

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