[Introduction] Use of solid-state sensors for measuring microdosimetric quantities has been increasing recently due to advantages such as its size, portability and its lack of high voltage biasing to work properly. However, these devices do not lack drawbacks; drift and diffusion phenomena affect partial charge collection, modifying the microdosimetric spectra depending on the geometry of the site, operation conditions and readout electronic noise. [Methods] Drift and diffusion processes are very relevant when micrometric active sites are considered. A perturbation in the pulse height detected spectrum respect to the ideal imparted energy within the considered site geometry is produced. Effects in silicon micro-dosimeters built by IMB-INM (CSIC, Spain) were evaluated. To parametrize the charge collection effi ciency an IBIC test at CNA (Seville, Spain) was performed and results were compared with TCAD simulations. The device model used together with FLUKA Monte Carlo simulations has been compared with experimental micro-dosimetric spectra of a clinical 12C ion beam at Fondazione CNAO (Pavia, Italy). [Results] Smeared Monte Carlo spectra reproduce the main features of the experimental spectra taken with the silicon microdosimeters affected by partial charge collection events. The perturbation on the frequency and dose averaged lineal energy as a function of micro-dosimeter size was evaluated. Additionally, the minimum detectable lineal energy for no intrinsic gain devices was evaluated considering a general model of readout electronics as a function of the fl uence averaged mass thickness of solid-state micro-dosimeters. [Conclusions] Solid-state devices can be employed to measure microdosimetric spectra, but large collection and electronic noise pose limitations on their performance. The perturbation on the microdosimetric spectra has been evaluated in this work to set a general benchmark for the expected performance of a micro-dosimeter depending on geometry and sensitive media.

Trabajo presentado en el 3rd International Conference on Dosimetry and its Applications, celebrado en Lisboa, del del 27 al 31 de mayo de 2019

Peer reviewed