The negative curvature phenomenon of resistivity damage rate observed in some metals neutron irradiated at 4.6 K

The collapse of defect cascades to dislocation loops

“…However, our Ni yield disagrees with those of Robinson [11] and Kitagawa [10]. Finally, a correlation can be made with the resistivity data of low temperature (5 K) fast neutron bombardment in these pure metals [4]. The socalled negative curvature in the resistivity production rate, observed to occur markedly in Fe and less so in Ni, may be due to vacancy loop formation with cascade overlap at higher neutron doses, and increasing nonlinearly with dose.…”

“…The socalled negative curvature in the resistivity production rate, observed to occur markedly in Fe and less so in Ni, may be due to vacancy loop formation with cascade overlap at higher neutron doses, and increasing nonlinearly with dose. The change in resistivity per vacancy upon loop formation (as suggested by Dunlap et al [4]) could explain this negative curvature. Our TEM evidence in Fe strongly supports this.…”

“…Self ions of energies of 50 and 100 keV were employed to simulate cascades produced by fast neutrons. Iron, nickel and copper were chosen to represent a possible range of cascade collapse probabilities based on an interpretation of resistivity damage rate data in Fe at 5 K under fast neutron bombardment [4]. These and other neutron data suggest that loops form from individual cascades produced at 5 K with increasing probability from Fe to Ni to Cu and that the probability increases with dose in Fe, and possibly to a lesser extent in Ni.…”

Heavy-ion irradiations of Fe and Fe–Cr model alloys Part 1: Damage evolution in thin-foils at lower doses

“…This conclusion is consistent with the observation that loops are first seen at doses > 10 16 m -2 when cascade overlap becomes significant. Such a mechanism had also been postulated by Dunlop et al [11] to explain their electrical resistivity experiments in iron neutron-irradiated at 4.2K. Recent molecular dynamics simulations suggest that small, sub-microscopic vacancy clusters (as well as small, mobile interstitial clusters) are produced in individual cascades in Fe [12].…”

“…Specimens could usually not be tilted by more than about [10][11][12][13][14][15] o before it became impossible to correct astigmatism. Only in a few cases was it possible to characterize completely all the loops present (for an example see Part 2).…”