Experimental consolidation and absolute measurement of the natC(p,x)11C nuclear activation cross section at 100MeV for particle therapy physics

The C-nat(p,x)C-11 reaction has been discussed in detail in the past [EXFOR database, Otuka et al. (Nuclear Data Sheets 120:272-276, 2014)]. However, measured activation cross sections by independent experiments are up to 15% apart. The aim of this study is to investigate underlying reasons for these observed discrepancies between different experiments and to determine a new consensus reference cross section at 100 MeV. Therefore, the experimental methods described in the two recent publications [Horst et al. (Phys Med Biol , 2019) and Backer et al. (Nuclear Instrum Methods Phys Res B 454:50-55, 2019)] are compared in detail and all experimental parameters are investigated for their impact on the results. For this purpose, a series of new experiments is performed. With the results of the experiments a new reference cross section of (68 +/- 3) mb is derived at (97 +/- 3) MeV proton energy. This value combined with the reliably measured excitation function could provide accurate cross section values for the energy region of proton therapy. Because of the well-known gamma-ray spectrometer used and the well-defined beam characteristics of the treatment machine at the proton therapy center, the experimental uncertainties on the absolute cross section could be reduced to 3%. Additionally, this setup is compared to the in-beam measurement setup from the second study presented in the literature (Horst et al. 2019). Another independent validation of the measurements is performed with a PET scanner.

Automated summary

The study investigates discrepancies in activation cross sections between different experiments for the C-nat(p,x)C-11 reaction and determines a new consensus reference cross section at 100 MeV, providing accurate values for proton therapy. By performing a series of new experiments and comparing experimental methods and parameters, a new reference cross section is derived, with experimental uncertainties reduced to 3% through well-defined equipment and procedures. An independent validation of the measurements is also conducted using a PET scanner.