Development and characterization of a compact nanodosimetric detector

Nanodosimetry has the goal of modelling the biological effectiveness of different radiation qualities by using physical quantities based on ionization cluster size distributions. With the Frequency of Ion Registration (FIRE) detector a compact nanodosimeter was built and tested. Within the FIRE detector, an alpha particle ionizes propane gas molecules, which drift towards a dielectric plate hole. Inside the hole they are accelerated strongly towards the cathode and produce an electron avalanche through impact ionization. The process is similar to that of Gaseous Electron Multipliers (GEM), although positive ions are detected. However, there are several limitations with the original design, such as vacuum seal issues, fixed anode height and limited data acquisition capabilities. Consequently, an improved prototype FIRE-V2 was developed to address these constraints, along with a completely new data acquisition system. The sensitive detector volume was measured experimentally with FIRE-V2 by shifting the alpha beam laterally relative to the dielectric plate hole. Furthermore, with the new data acquisition system the signal amplitude and area as a function of experimental parameters, such as drift and cathode voltage and gas pressure were studied and compared to previous simulations.

The results presented in this work offer further insights into the inner workings of the FIRE-V2 detector and the sensitive volume of the detector was measured for the first time.