Progress in Fast and Red Plastic Scintillators

Abstract

Radiological detection where Cherenkov residual background can be prominent requires scintillators with increased emission wavelength. Cherenkov residual background precludes the use of UV-emitting sensors such as plastic scintillators. However, the literature is scarce in red-emitting plastic scintillators and only one commercial scintillator is currently available (BC-430, from Saint-Gobain Crystals and Detectors). In addition, X-ray imaging or time-of-flight positron emission tomography (ToF-PET) applications are also demanding on this type (color) of scintillators, but such applications also require that the material displays a fast response, which is not particularly the case for BC-430. We present herein our latest developments in the preparation and characterization of fast and red plastic scintillators for this application. Here, ‘fast’ means nanosecond range decay time and ‘red’ is an emission wavelength shifted towards more than 550 nm. At first, the strategy to the preparation of such material is explained by decomposing the scintillator to fundamental elements. Each stage is then optimized in terms of decay time response, then the elemental bricks are arranged to give plastic scintillator formulations that are compatible with the abovementioned characteristics. The results are compared with the red-emissive BC-430 commercial plastic, and the ultra-fast, violet-emitting BC-422Q 1% plastic. In particular, the first-time use of trans-4-dimethylamino-4′-nitrostilbene in the scintillation field as a red wavelength shifter allowed preparing plastic scintillators with the following properties: λemmax 554 nm, photoluminescence decay time 4.2 ns, and light output ≈ 6100 ph/MeV. This means a scintillator almost as bright as BC-430 but at least three times faster. This new sensor might provide useful properties for nuclear instrumentation.