Microdosimetric Investigations in Realistic Fields

Microdosimetric measurements have been obtained in different complex fields: behind concrete with a primary beam of 200 MeV protons to estimate the efficiency of the shielding, the neutron yield and the response of different kinds of detectors; and reference fields behind shielding with a high energy primary beam to simulate the radiation at aircraft altitude. In general, the LET spectra are composed of a low LET part which represents the photons and the muons and a high LET part corresponding to neutrons, the latter being the most important one. The value of the mean quality factor (deduced from the ICRP 21) has been found 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.