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Optimization of a neutron production target and a beam shaping assembly based on the 7Li(p,n)7Be reaction for BNCT

✍ Scribed by A.A. Burlon; A.J. Kreiner; A.A. Valda; D.M. Minsky; H.R. Somacal; M.E. Debray; P. Stoliar


Publisher
Elsevier Science
Year
2005
Tongue
English
Weight
845 KB
Volume
229
Category
Article
ISSN
0168-583X

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✦ Synopsis


In this work a thick LiF target was studied through the 7 Li(p,n) 7 Be reaction as a neutron source for Accelerator-Based Boron Neutron Capture Therapy (AB-BNCT) to provide a testing ground for numerical simulations aimed at producing an optimized neutron production target and beam shaping assembly design. Proton beams in the 1.88-2.0 MeV energy range were produced with the tandem accelerator TANDAR (TANDem ARgentino) at the Comisio Β΄n Nacional de EnergΔ± Β΄a Ato Β΄mica (CNEA) in Buenos Aires, Argentina. A cylindrical water-filled head-phantom, containing a boric acid sample, was irradiated to study the resulting neutron flux. The dose deposited in the boric acid sample was inferred through the Compton-suppressed detection of the gamma radiation produced from the 10 B(n, ac) 7 Li capture reaction. The thermal neutron flux was evaluated using bare and Cd-covered activation gold foils. In all cases, Monte Carlo simulations have been done showing good agreement with the experimental results. Extensive MCNP simulation trials have then been performed after the preliminary calculation tool validation in order to optimize a neutron beam shaping assembly. These simulations include a thick Li metal target (instead of LiF), a whole-body phantom, two different moderator-reflector assemblies (Al/AlF 3 /LiF, Fluental Γ’ , as moderator and lead as reflector and a combination of Al, PTFE (polytetrafluoroethylene) and LiF as moderator and lead as reflector) and the treatment room. The doses were evaluated for proton bombarding energies of 1.92 MeV (near to the threshold of the reaction), 2.0 MeV, 2.3 MeV (near the reaction resonance) and 2.5 MeV, and for three Fluental Γ’ and Al/PTFE/LiF moderator thicknesses (18, 26 and 34 cm). In a later instance, the effect of the specific skin radiosensitivity (an RBE of 2.5 for the 10 B(n,a) 7 Li reaction) and a 10 B uptake 50% greater than the healthy tissue one, was considered for the scalp.


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