G. Solt

Dynamics of μ+ in Sc and ScHx

Abstract Muon spin rotation (μSR) experiments on single-cystal samples of ScHx, with x = 0, 0.05, 0.10 and 0.25, were performed in order to investigate the muon location and possible systematic variations in muon dynamics in these systems. The angular and magnetic field dependance of the μSR relaxation rates shows that at temperatures below 50 K the muon is localized at the interstitial tetrahedral (T) sites. The results for pure Sc, covering a wide range of high and low fields, are coherent with the picture that the muon performs fast tunnelling between two adjacent T sites, separated by 2z = 0.18c, above and below the a-b plane. This value for the muon position along the c axis is remarkably near the 2z = 0.194c found for D in Sc by neutron diffraction. The anisotropy of the relaxation rate at low magnetic fields varies sensitively with the H concentration, indicating a change in the ratio of the radial, muon-induced and the partly inherent, uniaxial electric field gradients at the position of the Sc nuclei.

A study of the mechanisms for the irradiation embrittlement of reactor pressure vessel steels

Abstract Irradiation damage particles were detected by small angle neutron scattering and positron annihilation techniques in two RPV steels. The particle radii were 8 A and 14 A prior to heat treatments for the plate and weldment, respectively; annealing leads to coarsening in the weldment, the volume fraction remains essentially constant at ∼0·14% . The model of copper-rich precipitates ‘diluted’ by Mn atoms or, alternatively, by vacancy agglomerates is consistent with the neutron scattering data, the presence of simple voids in the weldment would contradict the positron results. Preliminary results on these steels and also on related alloys by methods ‘new’ in this field are reported.