Thermal Accommodation Coefficient of Helium on a Bare Tungsten Surface

Abstract
The accommodation coefficient of helium on a presumably clean tungsten surface is determined from 83° to 303°K. A getter technique is applied in which, after thorough baking of the tube and vacuum system, aluminum is evaporated in vacuum over the inner walls of the measuring tube. The technique appears to be superior to the circulation over charcoal used by Roberts. Clean surface values of the accommodation coefficient, found by linear extrapolation to time of flashing the filament, lie between 0.0151 and 0.0172 (with small positive corrections probably to be applied). The variation with temperature is small and the values themselves are much lower than any heretofore reported.

This publication has 6 references indexed in Scilit: