Diffusion of Lithium Through Tungsten

The diffusion coefficients of Li/sup 7/ and Li/sup 6/ in tungsten were measured on tungsten ribbcn with Li deposited on one side; the Li atoms diffusing to the other side were identified by a mass spectrometer as a function of time. For the equation D = D/sub 0/ exp(- epsilon /kT), a plot of the Li/sup 7/ data on a D vs 1/T graph gives epsilon =2.42 plus or minus 0.05ev and D/sub 0/= 82 plus or minus 40cm/sup 2/ sec/sup -1/, and comparison of Li/sup 7/ and Li/sup 6/ data gives D/sub 6/D/sub 7/ = 1.07 plus or minus 0.02, which is in good agreement with (M/sub 7/M/sub 6/)/sup 1/2/ = 1.080. The diffusion is through the lattice rather than through the grain boundary or surface. (D.L.C.)