Medipix3 proton and carbon ion measurements across full energy ranges and at clinical flux rates in MedAustron IR1

Abstract

The Medipix3, a hybrid pixel detector with a silicon sensor, has been evaluated as a beam instrumentation device with proton and carbon ion measurements in the non-clinical research room (IR1) of MedAustron Ion Therapy Center. Protons energies are varied from 62.4 to 800 MeV with 104 to 108 protons per second impinging on the detector surface. For carbon ions, energies are varied from 120 to 400 MeV/amu with 107 to 108 carbon ions per second. Measurements include simultaneous high resolution, beam profile and beam intensity with various beam parameters at up to 1000 FPS (frames per second), count rate linearity and an assessment of radiation damage after the measurement day using an x-ray tube to provide a homogeneous radiation measurement. The count rate linearity is found to be linear within the uncertainties (dominated by accelerator related sources due to special setup) for the measurements without degraders. Various frequency components are identified within the beam intensity over time firstly including 49.98 Hz with standard deviation, σ = 0.29, secondly 30.55 Hz σ = 0.55 and thirdly 252.51 Hz σ = 0.83. A direct correlation between the number of zero counting and noisy pixels is observed in the measurements with the highest flux. No conclusive evidence of long term radiation damage was found as a result of these measurements over one day.

Medipix3 for dosimetry and real-time beam monitoring: first tests at a 60 MeV proton therapy facility

“…As mentioned in section 2.5, the change to a proton therapy service required the nominal arc current (of the order of mA) of the ion source to be limited such that the beam currents produced were practical for treatment (nA range). Only the 50 Hz component was observed in later measurements performed at MedAustron [45] which is a significantly different facility and operates a synchrotron. As such, it is presumed that these other frequency peaks are specifically associated with the CCC cyclotron or may be due to interactions with beamline elements.…”