Neutron energy spectra of d (49)‐Be and p (41)‐Be neutron radiotherapy sources

Abstract

Zero-degree neutron energy spectra for the p(41)-Be and d(49)-Be reactions were measured by time-of-flight for neutrons with energies above 1.9 and 1.4 MeV, respectively. Spectral changes resulting from the addition of copper, aluminum, and polyethylene filters to unfiltered beams were determined. Integral yields, average energies, filter material attenuation coefficients, and kerma fractions were computed for these spectra. Calculated spectra for neutron beams filtered by various thicknesses of polyethylene compared favorably with experimental results

Fast neutron and proton therapy sources

“…The main features of these spectra were consistent with the measurements of Meulders et al [87]. Graves et al [58] measured thick-target d + Be neutron spectra at E d = 49 MeV at 0 • using different filters. These data are also consistent with the E d = 50 MeV measurements of Meulders et al [87].…”

“…An exception has been the d(48.5) + Be(48.5) 1 superconducting isocentric cyclotron at the Harper Hospital, Detroit MI [53], the small size of which has permitted installation in a hospital. Measurements of p + Be broad neutron spectra in air for proton energies greater than 35 MeV have been made most often by the pulsed-beam time-of-flight (TOF) technique [18,39,[54][55][56][57][58][59][60][61][62], but recoil spectrometry [63,64] has also been used. A method that involved the iterative fitting of water-attenuation data has also been employed to derive a spectrum [65].…”

The effects of hydrogenous and nonhydrogenous filters on the quality of a p(66)Be(49) neutron beam

“…The hardening effect of hydrogenous filters on p-Be produced neutron beams has been well documented;G-ll a similar effect is also present in d-Be produced beams, 12 due to the preferential scattering of lower energy neutrons. 13 The penetration of p-Be beams can also be improved by making the target thinner, 6114115 but, above a residual energy of about 20 MeV, exiting protons still produce low energy neutrons in all practical backing materials, 16 thus limiting the effect of this approach. The best compromise would then be achieved using a semi-thick target and additional filtration.…”

The Influence of Target Thickness and Backstop Material on Proton Produced Neutron Beams for Radiotherapy

“…10 uncertainties due to accuracy 'for an overall uncertainty of 7.7 -9.0%. These error limits cover uncertainties in chamber calibration in a 60 co beam and uncertainties in neutron beam conversion factors in addition to the previously discussed precision limits.RESULTSIn all, four target thicknesses were investigated:"A" a pure beryllium target, 1 21. cm thick, which would stop 42 MeV protons completely; "B" syntered materia1 11 , HP-10, 0.81 cm thick, which would remove 22.6 MeV from a 42 MeV proton beam; "C" syntered material, HP-10, 0.60 cm thick, which would remove 15.3 MeV from a 42 MeV proton beam; "D" syntered material, HP-10, O .35 cm thick, which would remove 8.3 MeV from a 42 MeV proton beam.…”