# State-of-the-Art Mobile Radiation Detection Systems for Different Scenarios
## 4 Mobile Radiation Detection Systems
### Combination of Neutron and Gamma Detection Systems
On the other hand, uranium samples are much more difficult to detect by passive techniques due to their low neutron yield and the ease of shielding gamma-rays (e.g., heavy metals); therefore, active techniques must be used. In a later work, [PERSON] et al. [206] developed a compact gamma/neutron detector using the liquid scintillator EJ-309 coupled to a flat panel PMT. This detector has the advantage of lower toxicity and higher flash point compared to NE-213, making it more suitable for portable applications. [PERSON] et al. [207] developed a specific modular detection system, carried by a van, for the detection of SNM and other radioactive sources. It consists of a set of detectors based on high-pressure cells using noble gas scintillators filled with \({}^{4}\)He for fast neutrons (better STN than \({}^{3}\)He proportional counters with polyethylene moderator) and Xe for gamma-rays. It was also developed \({}^{6}\)Li-lined \({}^{4}\)He tubes, allowing to detect (using PSD techniques) either fast and thermal neutrons. A set of eight fast neutron detectors (FND) and two \({}^{6}\)Li-lined thermal neutron detectors (TND) were used. Xe-based scintillator was chosen mainly because of its robustness, vibration insensitivity, non-hygroscopic properties, volumes available, and better energy resolution than NaI (6.7% at 662 keV). Additionally, there was a NaI(Tl) scintillator (125 \(\times\) 125 \(\times\) 250 mm\({}^{3}\)) to maximize the detection efficiency at energies above 1 MeV. The detection system is capable of detecting and identifying gamma sources (NORM included) and neutron sources, like \({}^{252}\)Cf, Am/Be, Pu/Be, and SNM, as well as the presence of hydrogen-rich or lead shielding surrounding neutron sources. The detection system was tested according to ANSI 42.43, complemented with field tests using moving sources (\"drive by\" mode) and maritime cargo containers. The field tests allowed to pinpoint the importance of natural background variations which had an impact on the measurements (e.g., occasional triggering of false alarms). The mobile urban radiation search (MURS) project [208] consists of a real-time detection, identification and localization of radiological and nuclear sources in urban environments. The detection system is mounted in a car (Figure 15) and is composed by a six 5.08 \(\times\) 10.16 \(\times\) 40.64 cm\({}^{3}\) NaI(Tl) scintillators and a \({}^{6}\)Li neutron sensitivity layer. Additional contextual sensors, like visible and near-infrared cameras, were used to improve scene awareness. A GPS stabilized by an INS helped to have position information in case of GPS failure. Other features presented were temperature control and radionuclide list mode. For the passive neutron detection and localization of SNM, [PERSON] et al. [209] proposed a containerized detection system carried by a truck (Figure 16a) and composed by two separate subsystems: i) for TND, 24 BF3 (diam. 11.4 \(\times\) 183 cm, 93.2 kPa) and six \({}^{3}\)He detectors (diam. 14.7 \(\times\) 64 cm, 279 kPa) were considered, both surrounded by 2.5 cm high dense polyethylene (HDPE), and, ii) for FND, a 6 \(\times\) 8 array of EJ-309 liquid scintillator detectors (15.2 \(\times\) 15.2 \(\times\) 15.2 cm\({}^{3}\)) coupled to PMT. HDPE shielding was placed around the array except on one side for electronics access. Other features included a pair of GPS, a temperature and humidity control, a diesel generator to guarantee autonomy for 5 days, and a UPS to protect from power fluctuations. Static and in motion measurements were performed using a \({}^{252}\)Cf source (775,000 neutrons/s).