Monte Carlo track simulation with Geant4, Geant4-DNA and Garfield ++ studying feasibility and limitations of a GEM-based detector model

DNA damage is quantified on a nanometer scale, and nanodosimetry aims to quantify those interactions based on the frequency and size of the ionization clusters relevant to biological systems. Ionization clusters are the groups of resultant nanoparticles composed of radicles leading to DNA strand breaks after ionization irradiation. Radiation characteristics can assist in determining how often and how integral DNA damage from radiation can be on different tissues based on how hydrophilic molecules are. It has been observed that ionization events correlate to radiation effects which in turn correlate to the ionization cluster size.

GEMs, also known as Gas Electron Multipliers are a type of ionizing radiation detector with a foil coating over a polymer with microscopic holes in it, in a mesh-like pattern. The holes allow electrons to pass through and become multiplied when a charge is applied to them as they pass through and an extraction of charge produced in the gas permits characterization of the ionization events from primary radiation. Thick GEMs have been studied for nanodosimetry recently, and in this study we investigate the suitability of GEMs in other configurations, such as a drift chamber, for nanodosimetry. 

The aim of this project is to compare Monte Carlo track structures such as GEANT4, GEANT4-DNA, as well as Garfield ++, to evaluate the potential of GEMs at Jefferson Lab developed by the Radiation Detector and Imaging Group for nanodosimetry.