Experimental consolidation and absolute measurement of the $$^\text {nat}$$C(p,x)$$^{11}$$C nuclear activation cross section at 100 MeV for particle therapy physics

Abstract

The $$^\text {nat}$$ nat C(p,x)$$^{11}$$ 11 C 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 https://doi.org/10.1088/1361-6560/ab4511, 2019) and Bäcker 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.

In Regard to Kato et al

“…As the presented study featured a high-purity germanium detector, which facilitates a high accuracy level in terms of count rate and geometric efficiency, 4 the calculation of cross sections may help to improve the reliability of simulations. In the past, the reliability of the cross-section data were questioned 5 , 6 , 7 (and references therein), and thus, experimentally determined cross-section data are of high interest. Uncertainties of cross sections directly translate in uncertainties of Monte Carlo simulations.…”