Proposed pulsed neutron source for radiotherapy and radiography

Conventional radiation therapy involves low Linear Energy Transfer (LET) radiations like high energy electrons and photons. The basic effects of these ionizing radiations are to destroy the ability of cells to divide, by damaging their DNA strands. For low LET radiations, the damage is induced primarily by activated radicals produced from atomic interactions. Over the energy range of therapeutically used X-rays, typically 100 keV to 25 MeV, approximately the same physical dose needs to be delivered at different energies to reach a given biological endpoint, resulting in similar Relative Biological Effectiveness (RBEs). High LET radiations such as protons, neutrons, however, result in biological damage that is generally larger per unit dose than for X-rays, resulting in an elevated RBE. In case of neutrons, the recoils and nuclear disintegration product contributes to the dose are responsible for a high energy transfer to the biologically active molecules and destroy them in turn. High RBE, LET characteristics and comparatively good Dose Distribution Advantage (DDA), are the main attractive feature of the neutron therapy. As the biological effectiveness of neutrons is high, the required tumor dose is about one third the dose required with photons. Moreover, the tumor cell damaged by low LET radiation has a good chance to repair and continue to grow, while for tumors treated by neutrons the chance for repairing of tumor is very small. Therefore, the neutron therapy is presently realized in two versions: Neutron Capture Therapy (NCT) and the Fast Neutron Therapy (FNT). In NCT, the isotope with large absorption cross-section for thermal/epithermal neutrons is introduced into the body mainly through the blood, while FNT uses fast neutron with high penetrability and treats the malignant tumors of the head, neck, dairy gland, osteogeneous sarcomas, etc. Therefore, in the present paper, considering the importance of the field, the 6 MeV electron accelerator based pulsed neutron source is proposed for radiography and radiotherapy. In this case, various electron-gamma-neutron targets are simulated by Monte Carlo based computer code and obtained the neutron spectra through (γ,n) reaction. Integrated neutron flux is also measured experimentally and subsequently compared with the theoretical one