MICRODOSIMETRIC INVESTIGATIONS IN REALISTIC FIELDS

Microdosimetric measurements have been obtained in different complex f ields: behind concrete with a primary beam of 200 MeV protons to estim ate the efficiency of the shielding, the neutron yield and the respons e of different kinds of detectors; and reference fields behind shieldi ng with a high energy primary beam to simulate the radiation at aircra ft altitude. In general, the LET spectra are composed of a low LET par t which represents the photons and the muons and a high LET part corre sponding to neutrons, the latter being the most important one. The val ue of the mean quality factor (deduced from the ICRP 21) has been foun d to be between 3 and 5 with concrete shielding and higher than 6 with iron shielding. The application of ICRP 60 has an important effect on the estimations of the ambient dose equivalent and the quality factor increases up to 60% depending on the field.