Dosimetric Properties of d(80) + Be and d(80) + (Be + Ta) Neutrons

Dosimetric data were obtained for d(80) + Be and d(80) + (Be + Ta) neutrons with field size 9 × 11 cm at a 125-cm SSD impinging on a tissue-equivalent (TE) liquid phantom with density 1.10. Neutron production target thicknesses were 20 mm of Be, or 8 mm of Be plus 2.5 mm of Ta. Microdosimetric distributions in event size Y₁ and in L at depth 5 cm yielded $\overline{Y}_{1D}=63\ {\rm keV}/\mu {\rm m}$ and $\overline{L}_{D}=93\ {\rm keV}/\mu {\rm m}$ for d(80) + Be neutrons. The high LET component of absorbed dose is due mainly to secondary alpha particles and light spallation products, while the contribution from heavy ion recoils is less than with 14-MeV D-T neutrons. Dose rates measured with a Spokas $0.5\text{-}{\rm cm}^{3}$ ion chamber irradiated with d(80) + Be and d(80) + (Be + Ta) neutrons at depth 5 cm were 0.406 and 0.343 Gy/min-μA, respectively, while the corresponding depths for half-maximum doses in TE liquid were 15.5 and 17 cm. Neutron energy spectra in air showed corresponding mean neutron energies of 31.0 and 38.1 MeV.