Cooling High Intensity Atomic Hydrogen Beams to Liquid Heliumi Temperatures

An atomic hydrogen source, designed to operate in the viscous flow range, has been built at BNL. A unique feature of this source is a miniature gap between a teflon tube which guides the beam and an accommodator which cools it. Across this gap a stepfunction in temperature, with the teflon temperature exceeding 100°K and the accommodator temperature below 8°K, was successfully maintained. This configuration collimates the beam enough to prevent significant diffusive losses without subjecting it to the temperature range of high recombination. Initial results with an orifice of only one-tenth the dissociator aperture are indicative of particle density in the beam of well above 1010 cm-3.