Combined OSL-RL measurements for dosimetry in mixed LET proton fields

The present work displays the progress in dose and dose rate measurements in proton beams using the luminescence of beryllium oxide (BeO). Preceding experiments carried out in a 190 MeV scattered proton beam have shown that the responses of the optically stimulated luminescence (OSL) and radio-luminescence (RL) of BeO differ in their LET dependency. This can be exploited to perform accurate dose measurements as well as the determination of the LET value within the depth dose profile of a mono-energetic proton beam. In the current work a redesigned and optimized OSL-RL measurement setup is used to perform both OSL and RL readings sequentially with the very same BeO detector with a high optical stimulation and detection efficiency. The BeO detector (<; 1 mm ³ ) is stimulated and read out remotely using a pure silica core optical light guide coupling which transmits the stimulation light of a blue high power LED as well as the luminescence light that is detected by a single photon sensor. Additional optical filtering and a beam splitter are applied to separate the high intensity stimulation from the luminescence light. The system was tested measuring depth dose profiles of a mono-energetic proton beam and in the mixed LET field of a spread out Bragg peak similar to clinical conditions in proton therapy. Further investigations with a monochromator setup show the LET dependency of the RL spectrum.