Changes in the damage rate (residual electrical resistivity per unit electron fluence) were measured as a function of incident electron energy in the range 1.0-2.2 MeV for 0.002-in.-diam Nb and Ta wires. The threshold energies, estimated by simple extrapolation to zero production rates, were 36 eV for Nb and 32 eV for Ta. The resistivity of a Frenkel pair was determined to be about 5.3 μΩ cm/at.% for Nb and 1.9 μΩ cm/at.% for Ta. The damage production curves for two other bcc metals, Mo and W, are compared with those for Nb and Ta.

• Received 19 May 1969

DOI:https://doi.org/10.1103/PhysRev.188.1101