Evidence for the trapping of interstitial atoms in irradiated tungsten

The residual resistance of tungsten specimens was measured at 4 deg K after reactor irraddation at --196 deg C. Exposure in the BEPO Reactor at Harwell for six days doubled the residual resistivity from its original value. The specimen was heated to 1500 which restored its resistance to the pre- irradiation value. It was then irradiated for 12 hours, whlch caused a resistance increase of 8.81%. It appears that increasing the irradiation time to 12 hours causes more recovery at 100 deg C and 200 deg C and that there is very little change at --40 deg C. The results are explained by postulating the existence of several types of traps to which interstitial atoms could become attached. Such traps coudd take the form of substitutional impurity atoms whose size is less than that of the tungsten atom.