low and self-diffusion of xenon through Morgan EY9-166 graphite was studied in the pressure range of 10 to 400torr, by using a tracer technique and xenon-133. This pressure range covered the transition region from viscous to Knudsen flow. The permeability coefficient K and the effective diffusion coefficient Deff differed markedly at high pressure but tended to the same value at low pressure. The precision of the low pressure results was not sufficient to determine whether there was a significant difference between K and Deff in the Knudsen region.

A Comparison of Flow and Self Diffusion of Xenon through a Porous Graphite. Weller, K.R., Watts, H.: Carbon, 1965, 2[4], 337-40