Development and assessment of a calorimeter data acquisition and evaluation software for ionizing particles

Abstract

Hadron therapy, the irradiation of cancerous tissue with ions, is an already well established medical treatment, as it affects less healthy tissue than conventional radiotherapy due to the very localised energy deposition of accelerated ions. Yet, treatment planning is still done with conventional computer tomography, which has the drawback of a required conversion that is still slightly inaccurate. A direct proton computer tomography (pCT) would eliminate the need for such conversion. With the recently opened MedAustron in Wiener Neustadt the HEPHY Vienna has thus started researching into a demonstrative pCT set-up. In this project a measurement software for the calorimeter, that measures the residual energy of protons, has been developed. The software allows for automatized evaluation including pedestal subtraction and automatic calibration, offers various live data visualizations and produces output files that are easy to work with in Python or CERN’s ROOT framework. The evaluation measurements with this new software have been conducted at the HEPHY and at MedAustron and have provided more insight in the current state of the calorimeter. Especially the two modes, range telescope and sampling calorimeter have been assessed, and it has been found that only the range telescope mode is feasible in the current state of the calorimeter. It has further been shown that this is due to resolution problems in the proximity of the Bragg peak that are difficult to correct. Additionally, a new combined single proton range determination method has been proposed, compared and discussed. This method is a combination of the standard "last slice over threshold method" and a proposed "first slice under threshold minus one" method. The combined method overall exhibits the smallest deviations from the expected range.