Characterization of the Charge Collection Efficiency in Silicon 3-D-Detectors for Microdosimetry

New silicon 3-D-microdetectors have been developed to perform microdosimetry measurements for applications in hadron therapy. In this work, the charge collection efficiency (CCE) of an improved second generation of microdetectors having two different thicknesses (10 and 20 μm) and a diameter of 25 μm has been studied by means of the ion beam induced charge (IBIC) technique. New methods to study the active volume and the CCE of microdosimeters are proposed and verified here. The results show that, for this new generation of microdetectors, the CCE is 100% for radial distances up to 10.2 μm from the center of the device, and it rapidly decays between 10.2 μm and the detector edge. The characterization of the CCE conducted here will allow us to completely explain the energy spectra obtained during the microdosimetry studies performed in clinical centers.