The influence of helium decorated vacancy clysters on the hyperfine interaction of impurities in metals

Prospects of the realization of fusion reactors have stimulated research of the behaviour of helium in metals. In particular, desorption studies of helium from metals have contributed to our knowledge of the trapping of helium in vacancies and vacancy clusters. Vacancies can be found in isolated places in the metal or associated with impurities. The hyperfine interaction of such impurities in principle procides another method for studying the behaviour of helium in metals. We have pursued this idea by implanting radioactive impurities, suitable for DPAC or Moessbauer spectroscopy, into various metals and by looking for changes in their hyperfine interaction caused by helium doping and subsequent annealing. (orig.)