Temperature-dependent defect properties from ion-irradiation in Pu(Ga)

We report the measured decrease of electrical resistivity during isochronal-annealing of ion irradiation damage accumulated at low-temperature (10 or 20 K), and the temperature dependence of the resistance of defect populations produced by low-temperature damage-accumulation and annealing in a stabilized delta-phase plutonium alloy, Pu(3.3 at.% Ga). The normalized change in resistivity is compared for a specimen that was either self-irradiated (from Pu alpha-decay and the associated uranium-recoil) or 3.8 MeV proton-irradiated with a Pelletron electrostatic accelerator. Modeling of the annealing data through combined molecular dynamics (MD) and kinetic Monte Carlo (KMC) methods describes the defect populations as a function of irradiation type and annealing temperature. It is observed that interstitial clustering is extant for the self-irradiation, but that the corresponding vacancies from the uranium damage cascade appear to be more point defect-like, as exhibited by their subsequent annealing behavior and comparison with the experimental annealing properties from the proton-irradiation. We also report the temperature dependence of the resistance of defects resulting from low-temperature damage accumulation and subsequent annealing at three temperatures: 30, 150, and 250 K. For the two defect populations dominated by vacancies and vacancy clusters (150 and 250K), we observe a temperature-dependent defect population resistance of the form -a[1n(T)] + b suggestive of a Kondo impurity. A discussion of possible causes leading to this observation and their effects, as it might relate to the nature of the delta-phase of Pu, are presented. (C) 2003 Elsevier B.V. All rights reserved.