An ionization chamber for the dosimetry of 14 MeV neutron beams

A cylindrical ionization chamber with polythene walls, central electrode, and thin carbon conducting surfaces is described. Its calibration for measuring absorbed dose in a medium irradiated with a fast neutron beam is discussed. The dose to soft tissue is given by D T =0.79x c /R c R T , where R c is the reading obtained with the chamber given an exposure x c roentgens of 60 Co gamma -rays, and R T is the reading obtained in the neutron beam. It is estimated that the uncertainty on D T is +or-6%.