Efficient Monte Carlo simulation of delayed activation analysis experiments

An approach is described for efficiently modelling delayed activation analysis experiments, where radioactivity is induced in a sample through irradiation with neutrons or gamma-rays and subsequently measured by a separate detection system. The continuous single-history method is used, in which a single computer code tracks both the initial irradiation quantum and the decay products of any induced radioactive nuclei in a single event using Monte Carlo methods. Key aspects of the approach include the forcing of both the irradiation and decay processes to improve efficiency and the ability to simulate complex radioactive decays producing multiple, coincident decay products. The method has been implemented in the general-purpose EGSnrc code. A comparison with experimental results for the photoactivation of a gold foil is presented.