1. University of Duisburg‐Essen Technical Chemistry I, (CENIDE), (ZMB) 45141 Essen Germany
2. TU Dortmund University Department of Physics 44227 Dortmund Germany
3. West German Proton Therapy Centre Essen (WPE) West German Cancer Centre (WTZ) University Hospital Essen 45147 Essen Germany
4. German Cancer Consortium (DKTK) 69120 Heidelberg Germany
5. Faculty of Medicine University of Duisburg‐Essen Department of Particle Therapy University Hospital Essen 45147 Essen Germany