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

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.

Clustering of Diamond Nanoparticles, Fluorination and Efficiency of Slow Neutron Reflectors

Neutrons can be an instrument or an object in many fields of research. Major efforts all over the world are devoted to improving the intensity of neutron sources and the efficiency of neutron delivery for experimental installations. In this context, neutron reflectors play a key role because they allow significant improvement of both economy and efficiency. For slow neutrons, Detonation NanoDiamond (DND) powders provide exceptionally good reflecting performance due to the combination of enhanced coherent scattering and low neutron absorption. The enhancement is at maximum when the nanoparticle diameter is close to the neutron wavelength. Therefore, the mean nanoparticle diameter and the diameter distribution are important. In addition, DNDs show clustering, which increases their effective diameters. Here, we report on how breaking agglomerates affects clustering of DNDs and the overall reflector performance. We characterize DNDs using small-angle neutron scattering, X-ray diffraction, scanning and transmission electron microscopy, neutron activation analysis, dynamical light scattering, infra-red light spectroscopy, and others. Based on the results of these tests, we discuss the calculated size distribution of DNDs, the absolute cross-section of neutron scattering, the neutron albedo, and the neutron intensity gain for neutron traps with DND walls.

Absolute cross section measurements of 238U(n,f) and 237Np(n,f) in the neutron energy range 1-2.4 MeV

New standard (n,f) cross sections other than 235U are important to study the relevant cross sections for Generation-IV power plants. A specific need for such standards is for performing new experiments with quasimonoenergetic neutron beams, such as those produced by Van de Graaf accelerators. Neutrons down-scattered to low energies in the experimental environment, so called room-return, become relevant for this type of measurements. Hence, a standard (n,f) cross section with a fission threshold is of great interest, in order to suppress the contribution from room-return background. For this reason we have performed two experiments at the VDG of the National Physical Laboratory to measure absolutely the (n,f) cross sections of 235U, 238U and 237Np in the fast neutron energy region. Our preliminary results are in agreement with the most up-to-date evaluations.

Measurement of cross sections and isomeric cross-section ratios for the (n,2n) reactions on 85,87Rb in energies between 13 and 15 MeV

The (n,2n) cross sections and their isomeric cross-section ratios (σm/σg) in the neutron energy range 13–15 MeV have been measured for 85,87Rb by an activation and off-line γ-ray spectrometric technique using the Pd-300 Neutron Generator at the Chinese Academy of Engineering Physics (CAEP). The natural Rb samples and Nb monitor foils were activated together to determine the reaction cross section and the incident neutron flux. The neutrons were produced via the 3H(d,n)4He reaction. The pure cross section of the ground-state was derived from the absolute cross section of the metastable state and the residual nuclear decay analysis. The 85Rb(n,2n)84m,gRb and 87Rb(n,2n)86m,gRb reaction excitation functions and their isomeric cross-section ratios were also calculated theoretically using the TALYS-1.8 code with different level density options. Results are discussed and compared with the corresponding literature data.