Development of a proton bunch monitor for treatment verification in particle therapy

Treatment verification is a key element in future online-adaptive particle therapy. As a light-weight, collimator-free technique, Prompt γ-Ray Timing is a promising candidate for this purpose. The development of such a system for clinical application is challenging due to instabilities in the accelerator phase relation. We present two proton bunch monitors which are capable of measuring and ultimately correct for these instabilities. Firstly, a diamond detector to be placed at the beam energy degrader was investigated. It was found to exhibit an excellent time resolution 82(6) ps and to be able to monitor the phase instability with sufficient precision in a realistic geometry. Secondly, a phase pick-up installed in the low level radio frequency module of the accelerator was used. The data acquired with this monitor showed a very good agreement with the diamond detector with smaller statistical fluctuations. In conclusion, both proton bunch monitors were shown to resolve phase instabilities in Prompt γ-Ray Timing and are expected to strengthen the potential of this system for clinical application.