High-Energy and High-Rate X-Ray Measurements Using HfO₂ Nanoparticle-Loaded Plastic Scintillator

• Published in: IEEE transactions on nuclear science 2021-02, Vol.68 (2), p.165-172
• Main Authors: Kishimoto, Shunji, Toda, Akehiro
• Format: Article
• Language: English
• Subjects: Biphenyl; Count rate; detection efficiency; Detectors; Diameters; Efficiency; Energy; Hafnium oxide; Heavy metals; Loading; Nanoparticles; Photomultiplier tubes; Photons; plastic scintillator (PLS); Polymers; Polystyrene; Polystyrene resins; Pulse amplitude; Scintillation counters; Scintillators; Synchrotron radiation; Synchrotrons; time resolution; X ray detectors; X-ray detector; X-rays
• ISSN: 0018-9499; 1558-1578
• DOI: 10.1109/TNS.2020.3048943

The detection efficiency of a plastic scintillator (PLS) can be enhanced by loading with heavy metal nanoparticles to measure high-energy X-rays at a high count rate exceeding 10^{{7}}\,\,\text{s}^{{-1}} using a fast scintillation detector. We successfully polymerized up to 60 wt% HfO 2 nanoparticle-loaded PLSs (Hf-PLSs) by mixing with polystyrene and 2-(4-tert-butylphenyl)-5-(4-biphenyl)-1,3,4-oxadiazole as a fluorophore. Loading 40 wt% HfO 2 maintained a light yield of 79% of a commercially available 5 wt% lead-loaded PLS (EJ-256) with a much higher high- {Z} loading. We tested the 40 wt% Hf-PLS (8 mm in diameter, 3 mm in thickness) mounted on a photomultiplier tube using a synchrotron X-ray beam at beamline BL-14A of the photon factory (PF) ring. The detection efficiency of the X-ray detector reached 44.3 ± 0.2% at 50.0 keV. Counting rates of up to 2.76\times 10^{{7}}\,\,\text{s}^{{-1}} were recorded at input photon rates of up to 3.74\times 10^{{8}}\,\,\text{s}^{{-1}} in the multibunch mode of the PF ring. The pulse height and time spectra were observed using the 40 wt% Hf-PLS at 67.4 keV for application to synchrotron radiation nuclear resonant scattering on 61 Ni. The detection efficiency was 49.2 ± 0.2% at 67.4 keV, 7.2 times greater than that of EJ-256. A time resolution (full-width at half-maximum) of 0.32 ± 0.06 ns was obtained in the time spectrum but with a time resolution of 0.46 ns at best using EJ-256. The Hf-PLS is promising for applications in counting and timing measurements within the high-energy X-ray regions.