Determination of some parameters for pion radiobiology studies

Uniform depth dose distribution for biological irradiation using negative pions

A simple, flexible technique has been developed to generate uniform depth dose profiles for the biomedical pion beam at TRIUMF using dynamic momentum control and linear programming. Either the entrance dose or the irradiation time required for a certain dose over the uniform region can be minimised. The dynamic momentum control can operate automatically under computer control even with a highly unstable beam. Cell survival profiles have been obtained for this uniform dose distribution using the gelatin technique. The RBE increases with increasing depth through the uniform dose region.

Effects of negative pions and neutrons on the growth of Vicia faba bean roots

Vicia faba bean roots have been irratiated with neutrons of various energies and with negative pi-mesons, and the effect on the ten-day growth of the roots has been determened. The neutron irratiations were made in beams of 400 and 600 MeV maximum energy, as well as with neutrons from a plutonium-beryllium source (mean energy 4.4 MeV) and from a 14 MeV neutron generator. The bean roots have also been irradiated at various points along the depth-dose curve of negative pi-mesons, including the gegion where the pions annihilate on coming to rest. The results show a maximum relative biological effectiveness (RBE) of 3.7 for 50% reduction in ten days growth for stopped negative pions and values up to 3.3 for high-energy neutrons, compared to 5.5 for 14 MeV neutrons. The biological effectiveness of high-energy neutrons and stopped pions shows a more pronounced dependence on dose than does the effect with lower-energy neutrons.