Optimization and analysis of neutron distribution on 30 MeV cyclotron-based double layer beam shaping assembly (DLBSA)

Abstract

Design and optimization of double layer Beam Shaping Assembly (DLBSA) has been conducted using the MCNPX code. The BSA is configured to comply with such a construction having typically a double moderator, a reflector, a collimator, and a filter. The optimization of various combinations of materials that compose the moderator, reflector, and filter yields such quality and intensity of radiation beams that conform to the requirements for Boron Neutron Capture Therapy. The composing materials are aluminum and BiF 3 for moderator, lead and graphite for the reflector, nickel and polyethylene borate for the collimator, and iron and cadmium for the filter. Typical beam parameters measured at the exit of the collimator are epithermal neutron flux of 1.110 9 n/(cm 2 s), the ratio of epithermal neutron flux to thermal neutron and fast neutron flux 344 and 85, respectively, and the values of fast neutron and gamma dose to epithermal neutron flux 1.0910-13 Gycm 2 and 1.8210-13 Gycm 2 , respectively. Analysis of epithermal neutron flux and neutron beam spectrum using the PHITS code reveals that the distribution of epithermal neutron spreads out in the DLBSA. The highest intensity is found in the moderator and decline downstream of the collimator and filter. The spectrum of neutron beams displays a narrow spike with that peaks at 10 keV.

DOSIMETRY ANALYSIS OF BORON NEUTRON CAPTURE THERAPY (BNCT) ON THYROID CANCER USING PHITS CODE WITH NEUTRON FROM 30 MeV CYCLOTRON

“…The energy spectrum of the neutrons produced by DLBSA is the thermal, epithermal, and fast neutrons, with epithermal neutrons dominating with an energy range of 10 -6 to 10 -2 MeV. The neutrons produced by DLBSA have a neutron flux characteristic of 1.1 x 10 9 n/cm 2 .s, the ratio of epithermal neutron flux to thermal neutron flux of 344, the ratio of epithermal neutron flux to fast neutron flux of 85, the ratio of dose rate of fast neutrons to epithermal flux is 1.09 x 10 -13 Gy.cm 2 , and the ratio of gamma dose rate to epithermal neutron flux is 1.85 x 10 -13 Gy.cm 2 [15].…”

Dose analysis of Boron Neutron Capture Therapy (BNCT) on head cancer using PHITS code with neutron source from accelerator

“…The neutron source in this study is an accelerator with a cyclotron type of 30 MeV. The resulting fast energy is processed using Double Layer Beam Shaping Assembly (DLBSA) [8]. The characteristics of neutrons produced from DLBSA are epithermal neutron flux of 1.1  10 9 n/cm 2 .s, ratio of epithermal neutron flux and thermal neutron flux of 344, ratio of epithermal neutron flux and fast neutron flux of 85, ratio of dose rate of fast and the epithermal flux of 1.09  10 13 Gy.cm 2 , and the ratio of the gamma dose rate and the epithermal neutron flux of 1.82  10 13 Gy.cm 2 .…”