The change in the residual electrical resistivity of palladium was measured as a function of bombarding electron energy from 1 to 3 MeV. The measurements were compared with several theoretical models for multiple atomic displacements using a weighted least-squares analysis. The results indicate that the degree of fit between the models tested and the data improves as the number of secondary displacements predicted by the model decreases. Using the single-displacement model, the effective threshold for atomic displacement in palladium was found to be 34±2 eV, with a Frenkel resistivity of (9±1) X10 -4 Q cm per unit concentration of defects.

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A system is described for making low temperature electron bombardment studies. A liquid helium Dewar is used in ?onjunction wit? a 1.2-Mey Dynamitron electron accelerator. Cooling is by conduction, and annealing is accomplish~d by balancmg the hehum fl?w rate thro~gh the cooling coils with a heater located within the cooling head. Details of the sample mount are given along With the beam positioning and monitoring devices.