The diffusion of He in crystalline material was studied at 160 to 300C, and 800torr. The results could be described by:

D (cm2/s) = 3.9 x 10-5 exp[-10.6/RT]

A.Y.Kupryazhkin, P.V.Volobuev, P.E.Suetin: Zh. Tekh. Fiz., 1974, 44[8], 1774-8