Analysis of Radiation Annealing Observed during Low Temperature Irradiation with Neutrons and Heavy Charged Particles

Abstract

Large radiation annealing effects are observed for different metals during reactor irradiation at 4.5 °K. Saturation values for the resistivity changes are obtained by extrapolation from the linear decrease of the effective damage rate with defect concentration. These results agree well with those deduced from radiation annealing observed during irradiation with heavy charged particles. Various physical processes which are thought to contribute to the observed reduction of the accumulation rate of defects with irradiation time, are analysed.

Gamma irradiation effects in W films

“…1, the vertical traced lines indicates each irradiation stage. A typical annealing [6] time is observed in these results. After each irradiation, the resistivity presents exponential decrease as a function of the time.…”

Effective Charge Associated with a Displaced Ion in the Orthogonalized-Plane-Wave Formalism

“…ment, it was concluded that the observed "radiation annealing" was in fact a thermal-annealing effect caused by deterioration of the heat conductivity of the specimens during irradiation. 6 Large radiation annealing effects were observed in various metals during neutron irradiation by Burger et al 1 They proposed a model in which newly produced interstitials and vacancies recombine spontaneously with defects previously produced, thus reducing the net damage rate. In the case of neutron damage, this model has to be modified to include defect zones which overlap; in the overlapped zone, part of the defects annihilate each other.…”

“…(2.22) in Eq. (2.21a) and assuming that there is no overlap between core states centered around different ions results in^c(r)=LCiV-1 E {EC^-^-^M^^.kW^-Ri)The interpretation of (2.23) is clear: Centered about each ion there is a spherical distribution of charge due to the conduction electrons with approximately the same spread as the core distribution, the total number of electrons associated with each ion being Since n c {r) occurs with a minus sign in (2.21), for the long-range Coulomb interaction between ions, it appears that the total localized positive charge associated with each ion is (Z v +8Z v )e=Z v *e. This is the source of effective ion charge concept of Pick and Sarma 1. However, the effect of n p {r) in (2.21) must be examined.…”

“…[1][2][3][4] Radiation annealing, the nonlinear increase of damage with increase in particle flux, was first observed by Cooper et al 5 in copper, silver, and gold irradiated with 10-MeV deuterons. Later no radiation annealing was found in bombardment of aluminum and gold with 20-MeV deuterons.…”

Saturation Behavior of the Defect Production in Electron-Irradiated Copper Below 7.5°K

“…With c = Ap/Ap-p and the resistivity increase per 100 at.% Frenkel pairs App= 2.5X10"" 4 Here P is the production rate of Frenkel pairs which also includes the fraction y of unstable interstitials originally placed within the recombination volume V s around their corresponding vacancies. The parameters P = 1.34X 10"* 26 fi cm/(r/cm 2 ), r=0.1, and V s = 200 atomic volumina were obtained by fitting formula (3) to the experimental data (solid curve in Fig. 1).…”