Experimental assessment and analysis of calculations accuracy for the neutron-induced radio-isotopes in copper parts of radiotherapy accelerators

Induced radioactivity in particle accelerators is currently not sufficiently addressed, particularly for radiotherapy electron LINACs when the activation occurs via secondary neutrons created in photo-nuclear reactions.

Methodologies based on Monte-Carlo simulations coupled with activation calculation codes are often used to address this issue. Their accuracy, which is potentially affected by the limited capabilities of the calculation tools to simulate nuclear reactions at the origin of the materials activation, can be deeply analyzed only through comparisons with experimental values but the latter are not widely available.

New macroscopic data for the activity induced by neutrons in the materials commonly present in medical electron LINACs are presented. Neutron-induced activation has been measured by sample irradiation at SPIRAL2/NFS facility in accurately characterized configurations. Experimental results were compared to the simulations predictions allowing to assess the precision that can be achieved by a fully simulation-based methodology, mainly related to the energy-dependent reaction cross-sections.