Comparison of the microdosimetric event-size method and the twin-chamber method of separating dose into neutron and gamma components

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Abstract
Microdosimetric measurements of event-size spectra, made with a proportional counter, are used increasingly for separation of dose components in mixed n-.gamma. fields. Measurements in fields produced by 8.3 MeV deuteron bombardment of thick Be and deuterium targets were made in air and at 6 and 12 cm depth in water with a spherical tissue-equivalent (TE) proportional counter and with a pair of calibrated ion chambers (TE-TE and Mg-Ar). The 2 methods gave similar dose results for the neutron components, but the .gamma. components do not demonstrate consistent agreement. An important source of error in the microdosimetric method is the matching of the spectra measured at different gain settings to cover the large range of event sizes. The effect of this and other sources of error are analyzed.