Thin nickel and copper foils (~12mum thick) have been homogeneously implanted with 0-6 MeV alpha-particles yielding helium concentrations between 0.1 and 5 at.%. These foils have been investigated by measurements of the length and the lattice parameter and by transmission electron microscopy (TEM). Starting at the lowest implantation dose clustering of irradiation induced vacancies and interstitial atoms leads to the formation of stacking fault tetrahedra (SFT) and dislocation loops that eventually interact to form a dislocation network. In addition a large number of small vacancy-helium complexes is present that are characterized by a rather low average He density, i.e. the concentration of He atoms cHe is about one half of the vacancy concentration cV. At higher implantation doses ( cHegsim0.6 at.%) cHe/ cV increases slightly up to a value of 1 and small cavities become visible in the TEM. A `model' is proposed that describes this microstructural evolution by the continuous nucleation of stable He-vacancy (He-V) complexes as a result of high energy collision cascades. This model directly explains the low average helium density ( cHe/ cV<1) that is much lower than necessary to activate bubble growth by a loop punching mechanism, as well as the coexistence of small cavities and SFTs. Defect annealing and bubble growth during thermal annealing are discussed

Atomic defects such as vacancies and interstitials in crystalline solids produce elastic diffuse scattering of X-rays or neutrons. The distribution in reciprocal space of the diffuse scattering intensity contains very direct information about the atomic structure of point defects, and it sensitively shows the formation of defect clusters. Three domains of the scattering are distinguished: (a) scattering in the forward direction (small-angle scattering); (b) scattering between the Bragg reflections; and (c) scattering close to the Bragg reflections (Huang scattering). The specific features of the information obtained from measurements in the different domains are discussed. Experimental results on the structure of interstitials in metals have been obtained after low temperature electron irradiation of the FCC metals Al and Cu, BCC Mo, and HCP Zn. In other metals (Au, Nb, Cd, Mg) the agglomeration of interstitials was observed during electron irradiation at 5K

For pt.I see ibid., vol.35, no.8, p.1929-41 (1987). The microstructural evolution during annealing of thin nickel foils (ap12 mum) that had been homogeneously implanted with helium up to concentrations of 1 at.% has been investigated by measurements of the electrical resistivity, by differential dilatometry and transmission electron microscopy (TEM). The most characteristic changes of the microstructure are: (i) for temperatures below annealing stage V of radiation damage annealing ( Tles650 K) major changes are observed only by a decrease of the electrical resistivity that reveals recombination reactions of small clusters of radiation defects; (ii) by annealing through the temperature range of stage V ( Tles790 K) a rearrangement and growth of the He-vacancy complexes into bubbles is observed; (iii) at higher temperatures ( Tles1070 K) bubble growth is observed by TEM and differential dilatometry directly shows that thermal vacancies are absorbed by He bubbles. The average bubble pressure tends to approach the thermal equilibrium pressure

Muonic Coulomb capture ratios and X-ray intensity patterns in four binary mixtures of the gases N 2, Ne, Ar, Kr, and Xe have been measured at three atomic ratios. An influence of the concentration has been established. The Lyman series intensity patterns of pure N 2 , Ne, Ar, Kr, and Xe were measured at pressures between 0.4 and 51 bar and found to depend on the pressure. Possible explanations are discussed