Neutron Irradiation Effects in Cu and Al at 80°K

A cryostat is described for pile neutron irradiation in the BNL reactor of samples at liquid nitrogen temperature. One-month irradiation resulted in resistivity increases of 20 and 33 percent for Cu and Al, respectively, at 80^∘{}K, and increases by about a factor of 5 in critical shear stress for both. Subsequent studies of the kinetics of recovery processes were made by a number of isothermal annealing curves at various temperatures from -80^∘{}C to 500^∘{}C. In copper, two-thirds of the resistivity effect anneals out from -80^∘{} to 20^∘{}C, activation energy {~}0.6 ev, with no decrease in critical shear stress effect. Both effects then anneal together near 320^∘{}C, with energy 2 ev. In aluminum, both effects completely anneal out together near -60^∘{}, with 0.55 ev energy. Data are correlated with diffusion activation energy for lattice defects.