Monte Carlo tools to supplement experimental microdosimetric spectra.

Tissue-equivalent proportional counters (TEPCs) are widely used in experimental microdosimetry for characterising the radiation quality in radiation protection and radiation therapy environments. Generally, TEPCs are filled with tissue-equivalent gas mixtures, at low gas pressure, to simulate tissue site sizes similar to the cell nucleus (1 or 2 µm). The TEPC response using Monte Carlo (MC) codes can be applied to supplement experimental measurements. Most of general-purpose MC codes currently available recourse to the condensed-history approach to model the electron transport and do not transport low-energy electrons (<1 keV), which can lead to systematic errors, especially in thin layers and in gas-condensed medium interfaces. In this work, a comparison between experimental microdosimetric spectra of (60)Co and (137)Cs radiation at different simulated sizes (from 1.0 to 3.0 μm) in pure propane versus simulated spectra obtained with two general-purpose codes FLUKA and PENELOPE, which include a detailed simulation of electron-photon transport in arbitrary materials, including gases, is presented.