Review of activation methods for the determination of neutron flux density spectra

A review is given of the possibilities for determining neutron flux density spectra from the counting results obtained with activation and fission foils. An introductory section deals with basic concepts and procedures. The most promising computer programs for determining neutron spectra from activation results, such as SAND-II, SPECTRA, RFSP, CRYSTAL BALL are reviewed with respect to the possibilities and experience obtained. Attention is given to the energy coverage and response characteristics of activation reactions in use. In the discussion of the quality of the solution the concept of improvement ratio is defined, which describes the increase of information on the spectrum due to the unfolding procedure. Finally the availability of nuclear data is considered