Protection of civilians and facilities against chemical, biological, radiological, nuclear, and explosives (CBRN-E) emerged after 9/11 events and remains since this date of particular importance for countries and states. When combined to the shortage of efficient detectors (e.g., 3He for thermal neutron detection) and a global, worldwide crisis, there is a real need of cheap, yet efficient detectors.
To detect illicit smuggling of gamma-ray sources, a first analysis requires fast gamma spectrometry. The abovementioned equation (increase in terrorists attack + need of cheap detectors for large-scale deployment) naturally leads one to use plastic scintillators (PS) as detectors to be embedded in radiation portal monitors. Despite its high gamma-ray sensitivity, this material is not perfectly suited for this, due mainly to the poor gamma resolution, Precluding therefore any subsequent gamma identification. In the case of gamma-rays emitters indeed, only the Compton continuum and Compton edge are obtained after interaction in the plastic scintillator, and no information of the full energy peak can be observed.
This chapter presents recent improvements concerning potential optimizations for the gamma-ray spectrometry using plastic scintillators as a detector, with a focus on:
Chemically modifying the nature of the PS. Due to its intrinsic low density and effective atomic number, this family of detectors is not well-suited for gamma-ray spectrometry. However, recent advances in the loading of plastic scintillators with organometallic complexes containing, for example, lead, tin, or bismuth, led to important breakthroughs in this field. As a perspective, nanomaterials are now being included in plastic scintillators, which can afford new and unrevealed specifications. All the advantages and drawbacks of the plastic scintillator loading with organometallics will be fully discussed.
Spectra classification and deconvolution methods based on specific smart algorithms have shown very promising results to identify gamma isotopes either alone or in mixtures. An important aspect for counterterrorism applications is real-time detection so algorithms which fulfill this requirement are of great interest.
This chapter mostly describes recent advances in the chemical modification of plastic scintillators for Pseudo-gamma spectrometry. The second part introduces dedicated algorithms for the processing of poorly resolved gamma-ray spectra, allowing therefore gamma identification with plastic scintillators. When available, some examples will be provided.