Optimization of the photoneutron target geometry for e-accelerator based BNCT

Abstract

Background and aimToday, electron accelerators are taken into consideration as photoneutron sources. Therefore, for maximum production of epithermal neutron flux, designing a photoneutron target is of significant importance. In this paper, the effect of thickness and geometric shape of a photoneutron target on neutron output were investigated.MethodsIn this study, a pencil photon source with 13, 15, 18, 20 and 25 MeV energies and a diameter of 2 mm was investigated using Monte Carlo simulation method using MCNP code. To optimize the design of the photoneutron target, the tungsten target with various geometries and thicknesses was investigated.ResultsThe maximum neutron flux produced for all target geometries and thicknesses occurred at neutron energy peak of around 0.46 MeV. As the thickness increased to 2 cm, neutron flux increased and then a decreasing trend was observed. For various geometrical shapes, the determining factor in photoneutron output was the effective target thickness in the photon interaction path that increased by the increase in the area of interaction. Another factor was the angle of the photon’s incidence with the target surface that resulted in a significant decrease in photoneutron output in cone-shaped targetsConclusionThree factors including the total neutron flux, neutrons energy spectrum, and convergence of neutrons plays an important role in the selection of geometry and shape of the target that should be investigated considering beam shaping assembly (BSA) shape.

Dose equivalent consideration from neutron contamination in modified radiotherapy vault: a Monte Carlo study

“…Uterine cervical cancer, the prevalent lethal gynecologic malignancy in women worldwide, benefits from standard adjuvant pelvic radiotherapy with highenergy photons [1][2][3]. While photons with energies above 10 MV provide increased penetration depth and skin-sparing for deep-seated tumors [4], their interaction with metal components at the linear accelerator (LINAC) causes photoneutron contamination [5][6][7][8][9][10].…”

“…Previous MC simulation studies have evaluated neutron contamination from the LINAC head [5][6][7][8][9][10] and the laminated barrier during total body irradiation (TBI) [11], considering different field sizes, energy levels, LINAC models, number and thickness of reconstructed walls with metal sheets [13,14,17].…”