A novel compact gas-based nanodosimeter detector for proton therapy applications

The major goal in the metrology of micro- or nanodosimetry is to provide physical quantities that are well suited to represent the biological effectiveness of radiation, to model it, and assess it by measurement. Absorbed dose, which has been consistently used in "macroscopic" dosimetry up to now, turns out to be unsuitable when applied to the microscale; for example, when modeling radiation effects on cells and DNA.

Especially for densely ionizing particles such as low energy protons, ionization clusters occur on the nanometer scale. The quantity considered suitable for nanodosimetry is the ionization cluster size distribution, i.e., the probability distribution of ionization cluster sizes. From a metrological point of view, nanodosimeters are used to determine the ionization cluster size distributions produced by the mixed radiation field.

There is an urgent need to measure and predict the formation of large ionization clusters, which are biologically most important, using a gas-based compact nanodosimeter as well as Monte Carlo track-structure simulations. Nanodosimetric quantities might replace or complement the dosimetric quantities currently in use, and could then be used in treatment planning and radiation protection. Thus, further design and testing of a compact nanodosimeter for mixed radiation fields is the objective of this work.