# State-of-the-Art Mobile Radiation Detection Systems for Different Scenarios
## 4 Mobile Radiation Detection Systems
### Combination of Neutron and Gamma Detection Systems
[202, 204] described the radiological multi-sensor analysis platform (Rad_MAP) system carried by a vehicle (Figure 14b) and composed by three types of radiation detectors: a gamma-ray imager with 10 \(\times\) 10 array of NaI(Tl) detectors with a coded lead mask, an array of 14-24 HPGe detectors (for isotope identification), and an array of 16 liquid scintillators (EJ-209) for fast neutron detection. The Rad_MAP goal is to study variations in the natural background radiation and to serve as a development platform to mobile detection systems and imaging. To achieve this goal, it uses the information from several contextual sensors, like a panoramic video, a LiDAR (for data fusion of 3D scene reconstruction with gamma-ray images), a weather station, and a hyperspectral sensor, to analyze the impact of certain environmental parameters in the background. For example, it is known that the neutron background is mainly cosmogenic, and so it is lower and less variable than gamma-ray background. However, if weak sources of SNM are present, even small systematic variations in the background can influence its detection. The main contributor for the fast neutron background variability is the atmospheric pressure (affects the development and attenuation of the cosmic ray showers), followed by the \"sky-view factor\" (fraction of the sky that is not blocked by buildings), which is important in urban areas since there are more buildings and consequently more attenuation of the cosmogenic neutrons (lower neutron background). The authors concluded that there is a strong correlation between the surrounding environment and the background radiation and that the use of context and/or environment specific detection thresholds and background models could allow for improved detection sensitivity at a constant false alarm rate. Within the scope of the project SLIMPORT, a sistema mobile per analisi non distruttive e radiometriche (SMANDRA, in English, stands for mobile system for non-destructive radiometric analysis) is being developed [205]. This mobile inspection system is divided into a passive unit for gamma-rays and thermal and fast neutrons detection and identification of radioactive material and SNM and an active unit composed by a sealed neutron generator to produce tagged neutron beams (the first unit is used to detect resulting radiation originated from the active unit). The photon spectrometry is accomplished by NaI(TI) and LaBr\({}_{3}\)(Ce) detectors. The latter, despite the good resolution, due to internal activity, has some limitations in the detection and identification of weak \({}^{40}\)K sources. Moreover, the volumes available are still limited. Therefore, a large NaI(TI) is necessary to detect energetic gammas (6 MeV) originated by active techniques (inelastic excitation of oxygen and carbon). For weak and un-moderated sources, there is the interest of detecting fast neutrons since the STN ratio is higher compared to thermal neutrons, due to the dependence of 1/E of the cosmic-ray induced background. Therefore, an organic liquid scintillator NE-213 is used for fast neutrons and a \({}^{3}\)He proportional counter for thermal neutrons. First results are  
Figure 14: Examples of gamma and neutron detection systems: **(a)** Multi-rotor UAV with a dual-mode CLYC sensor and a manipulator. Reproduced, with permission, from Reference [201]; published by MDPI, 2019, under the terms of the [[https://creativecommons.or](https://creativecommons.or)]([https://creativecommons.or](https://creativecommons.or)) g/licenses/by/4.0/CC BY 4.0 license. **(b)** Radiological multi-sensor analysis platform (RadMap) system carried by a truck showing the lead coded mask (NaI detectors behind), high-purity Ge (HPGe) detectors, and EJ-309 liquid scintillators. Reproduced, with permission, from Reference [204]; copyright Elsevier (2016). in line with other studies [5], showing that small plutonium samples can be detected by using passive techniques.