The distributions of dose in linear energy transfer have been measured for three primary beams of neutrons being developed for radiotherapy applications. The neutron beams, collimated to$15\times 15\ {\rm cm}^{2}$, were produced by 16-, 30-, and 50-MeV deuterons impinging upon a beryllium target. The relative changes in the distributions have been correlated with incident deuteron energy, depth in tissue, and scattering media. Thicker beryllium targets decreased the dose distributions of the resultant beam. Spectral distributions of scattered beams taken in air out of the primary field exhibited considerable shift to lower values. Dose average LET values over the limited range of 1-500 keV μm were determined as a function of depth for each energy beam. The results were favorable in relation to the anticipated use of higher energy neutron beams for radiation therapy.

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