In the last decade, the development of more compact and lightweight radiation detection systems led to their application in handheld and small unmanned systems, particularly air-based platforms. Examples of improvements are: the use of silicon photomultiplier-based scintillators, new scintillating crystals, compact dual-mode detectors (gamma/neutron), data fusion, mobile sensor networks, cooperative detection and search. Gamma cameras and dual-particle cameras are increasingly being used for source location. This study reviews and discusses the research advancements in the field of gamma-ray and neutron measurements using mobile radiation detection systems since the Fukushima nuclear accident. Four scenarios are considered: radiological and nuclear accidents and emergencies; illicit traffic of special nuclear materials and radioactive materials; nuclear, accelerator, targets, and irradiation facilities; and naturally occurring radioactive materials monitoring-related activities. The work presented in this paper aims to: compile and review information on the radiation detection systems, contextual sensors and platforms used for each scenario; assess their advantages and limitations, looking prospectively to new research and challenges in the field; and support the decision making of national radioprotection agencies and response teams in respect to adequate detection system for each scenario. For that, an extensive literature review was conducted.

The cross section of the reaction ${}^{197}\mathrm{Au}$($n,\gamma$) was measured with the time-of-flight technique at the n_TOF (neutron time-of-flight) facility in the unresolved resonance region between 5 and 400 keV using a pair of ${\mathrm{C}}_6$D${}_6$ (where D denotes ${}^2\mathrm{H}$) liquid scintillators for the detection of prompt capture $\gamma$ rays. The results with a total uncertainty of $3.9\%–6.7$ $\%$ for a resolution of 20 bins per energy decade show fair agreement with the Evaluated Nuclear Data File Version B-VII.0 (ENDF/B-VII.0), which contains the standard evaluation. The Maxwellian-averaged cross section (MACS) at 30 keV is in excellent agreement with the one according to the ENDF/B-VII.0 evaluation and 4.7$\%$ higher than the MACS measured independently by activation technique. Structures in the cross section, which had also been reported earlier, have been interpreted as being due to clusters of resonances.

The neutron capture cross section of ${}^{209}\mathrm{Bi}$ has been measured at the CERN n_TOF facility by employing the pulse-height-weighting technique. Improvements over previous measurements are mainly because of an optimized detection system, which led to a practically negligible neutron sensitivity. Additional experimental sources of systematic error, such as the electronic threshold in the detectors, summing of γ-rays, internal electron conversion, and the isomeric state in bismuth, have been taken into account. γ-Ray absorption effects inside the sample have been corrected by employing a nonpolynomial weighting function. Because ${}^{209}\mathrm{Bi}$ is the last stable isotope in the reaction path of the stellar $s$-process, the Maxwellian averaged capture cross section is important for the recycling of the reaction flow by α decays. In the relevant stellar range of thermal energies between $\mathit{kT}=5$ and 8 keV our new capture rate is about 16% higher than the presently accepted value used for nucleosynthesis calculations. At this low temperature an important part of the heavy Pb-Bi isotopes are supposed to be synthesized by the $s$-process in the He shells of low mass, thermally pulsing asymptotic giant branch stars. With the improved set of cross sections we obtain an $s$-process fraction of 19±3% of the solar bismuth abundance, resulting in an $r$-process residual of 81±3%. The present ($n,\gamma$) cross-section measurement is also of relevance for the design of accelerator driven systems based on a liquid metal Pb/Bi spallation target.

We have measured the neutron capture reaction yield of ${}^{232}\mathrm{Th}$ at the neutron time-of-flight facility n_TOF at CERN in the energy range from 1 eV to 1 MeV. The average capture cross section has been extracted in the energy range from 4 keV up to 1 MeV with an overall accuracy better than 4%. An independent IAEA evaluation shows good agreement with the data. The average cross section has been expressed in terms of average resonance parameters using the partial waves $\ell =0,1,$ and 2.

The precise determination of the neutron capture cross sections of ${}^{186}\mathrm{Os}$ and ${}^{187}\mathrm{Os}$ is important to define the $s$-process abundance of ${}^{187}\mathrm{Os}$ at the formation of the solar system. This quantity can be used to evaluate the radiogenic component of the abundance of ${}^{187}\mathrm{Os}$ due to the decay of the unstable ${}^{187}\mathrm{Re}$ ($t_{1/2}=41.2$ Gyr) and from this to infer the time duration of the nucleosynthesis in our galaxy (Re/Os cosmochronometer). The neutron capture cross sections of ${}^{186}\mathrm{Os}$, ${}^{187}\mathrm{Os}$, and ${}^{188}\mathrm{Os}$ have been measured at the CERN n_TOF facility from 1 eV to 1 MeV, covering the entire energy range of astrophysical interest. The measurement has been performed by time-of-flight technique using isotopically enriched samples and two ${\mathrm{C}}_6$D${}_6$ scintillation detectors for recording the prompt $\gamma$ rays emitted in the capture events. Maxwellian averaged capture cross sections have been determined for thermal energies between $\mathit{kT}=5$ and 100 keV corresponding to all possible $s$-process scenarios. The estimated uncertainties for the values at 30 keV are 4.1, 3.3, and $4.7\%$ for ${}^{186}\mathrm{Os}$, ${}^{187}\mathrm{Os}$, and ${}^{188}\mathrm{Os}$, respectively.