Speaker
Description
Fiber-coupled scintillators are known to exhibit a nonlinear response to high-LET beams, i.e. ionization quenching. Although corrections may be applied using e.g. Birks’ empirical formula such procedures are challenging and may even introduce errors.
Recent studies suggest that Cerenkov light produced in optical fiber cables may be used to circumvent the ionization quenching. The distribution of emitted Cerenkov photons as a function of depth correlates well with the depth-dose profile for electron beams, whereas the agreement is less clear-cut in a proton beam with much fewer charged particles above the Cerenkov energy threshold. Nonetheless, excellent experimental agreements between the Cerenkov radiation and dose distributions have been reported in both electron and proton beams which furthermore motivates this work.
A Geant4 model of the guidance of the Cerenkov photons is in excellent agreement with Cerenkov measurements in an electron beam. The experimentally validated Monte Carlo code is subsequently used to investigate the Cerenkov photon distribution in a proton beam, where the main contribution is from scattered, secondary electrons. Results indicate, that the reported Cerenkov Bragg-peak actually arises from fluorescence.
The Cerenkov light in optical fibers can be used to measure the depth profile of electron beams. The situation is more subtle in proton beams, where hardly any Cerenkov photons are guided to the photomultiplier tube, and the fluorescence signal is orders of magnitude larger.
