The nice high-energy neutron facility: dosimetry intercomparisons

Neutron dosimetry intercomparison studies have been undertaken at the Nice neutron-therapy facility with the staff at Louvain-la-Neuve which has had wide experience in both dosimetric and radiobiological intercomparisons. Tissue equivalent (TE) ionization chambers were first calibrated in 60Co beams and then exposed in the neutron beam at different depths in a water phantom; the largest difference observed in neutron beam measurements with all the chambers tested was 0.89 %, and most of them agreed to within less than 0.5 %. The gamma component at four depths was derived from measurements with Geiger-Mueller counters; the results obtains with the two counters (Nice and Louvain-la-Neuve), expressed as a percentage of the dose (neutron + gamma), agreed to within less that 0.03 % and the value increased from 1.4 to 4 % between 2 and 20 cm in depth. (author)