Development of a simple neutron irradiation facility utilizing the stray neutron field of a medical cyclotron

Abstract

During the routine isotope production schedule at the Australian National Medical Cyclotron thick copper plates, electroplated with enriched target materials, are bombarded with 30 MeV protons with an average beam current of 200 μA. As a result an intense high-energy, prompt neutron flux of the order of 1.72 × 10 13 neutrons·cm −2·2 −1 is generated in the immediate vicinity of the target. The stray fast neutrons were moderated using a water-filled PVC bucket placed on the target station. A maximum thermal neutron flux of 3.88 × 10 9 neutrons·cm −2·s −1 was measured in the bucket using cobalt activation discs. The thermal neutrons from this irradiation facility has been used for the neutron activation analysis of trace elements in archaeological artefacts. It has also been planned to utilize the fast neutron flux by varying the geometry of the water moderator in order to estimate oxygen concentration in high-temperature superconductors and aluminium and silicon in ceramics.