RESUMO
The aim of this research was to investigate the relationship between the collimator aperture and fast-neutron flux, neutron-energy spectrum and absorbed dose rate. For remote therapy, rather large fluxes of fast neutrons are needed which can create dose levels in the tissues of at least 0.1 Gy/min with a source-patient distance of 1 m. Advantageously for these purposes, the 9Be(d, n) reaction was investigated with deuteron energy of 13.6 MeV. The mean energy of the outgoing neutrons was obtained using the code PACE 4 (LISE++) which gave the value of about 5.2 MeV. The maximum neutron flux was at an energy of about 2.5 MeV. Samples activation analysis was deployed to measure the neutron flux in the energy-region [0-14 MeV]. The experimental works were carried out using Al, Fe, Cu and Cd foils which installed on the collimator apertures. To investigate the neutron spectrum, fluxes, and dose rates absorbed at the position of patients, experiments were conducted for four different neutron irradiation-field sizes, which can be modified by the removable-polyethylene parts. Simulation results obtained by the code MCNP-4C and PACE4 (LISE++) were comparable with the experimental data to some extent with consideration of some uncertainties of PACE4 results. It can be concluded that the neutron flux is depended on the irradiation-field size where the neutron flux output for bigger aperture size was about +25% comparing with the smaller ones. These results could play a significant role in improving the neutron flux and optimizing the collimation system utilized in fast neutron therapy. In addition, this can lead to optimization of irradiation canals installed in the nuclear reactors which employed for production of medical isotopes, material testing and many other applications.
RESUMO
The excitation function of the 96Zr (α,n)99Mo reaction was determined using the stacked-foil activation technique. For the experiments, two stacks with metal foils of Cu, Ti and Zr of natural isotopic composition were irradiated independently with a 27.2 MeV α-particle beam. The characteristics of the primary beam and its verification along each stack were determined according to the well-known natCu(α,x)65Zn, natCu(α,x)66,67Ga, and natTi (α,x)51Cr monitor reactions. It was deduced that the expected production yield from 99Mo by irradiating 96Zr targets with a 23.8 MeV alpha particle beam for 1 h is 1.77 MBq/µA. According to the results, irradiation characteristics are proposed to produce 99Mo with high specific activity.
RESUMO
In this paper we present our cyclotron based neutron source with average energy 6.3 MeV generated during the 13.6 MeV deuterons interactions with beryllium target, neutron field dosimetry, and dosimetry of attendant gamma fields. We also present application of our neutron source for cancer treatment.