Performance of Optical Coupling Materials in Scintillation Detectors Post Temperature Exposure

Romanchek, Gregory R.; Wang, Yuli; Marupudi, Harsha; Abbaszadeh, Shiva

doi:10.3390/s20216092

Cited by 14 publications

(3 citation statements)

References 16 publications

(15 reference statements)

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“…Further on, many scintillator based high energy detectors use optical coupling for direct contact of scintillator pixel with the CMOS camera or even special design of the pixel which promotes wave-guiding of the scintillated light. In such cases the scintillated light does not need to couple to free space radiation [42], [43]. Finally, in broader picture, the high-Q approach opens new possibilities, otherwise not accessible.…”

Section: Discussionmentioning

confidence: 99%

Large-Area Photonic Bound State in the Continuum for Ultraviolet and Deep-Blue Emission for Organic, Inorganic, and Perovskite Scintillators

Kowal

Wong

Birowosuto

2023

IEEE Trans. Nucl. Sci.

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Optimizing the emission properties of materials in ultraviolet and deep blue (UV-DB) is interesting in development of new scintillator devices for the detection of X-ray, γ-ray and radiation particles as those materials can be strong candidates for high light yield and fast scintillators. While their intrinsic material properties are already well studied, photonic enhancement generated through optical confinement could significantly improve their emission characteristics, however one needs to overcome the problem of relatively low refractive indices contrast resulting in poor confinement of UV-DB light. This motivates the search for resonator structures built from readily accessible materials that can boast strong confinement in this spectral regime. Here, we present such a structure, leveraging bound states in the continuum (BICs) to realize large-area confinement of UV-DB light with ultra-high quality factors up to Q ∼10 7 . These ultra-high Q-factors in turn result in strong enhancements in light emission via the Purcell effect. We demonstrate the operation of such a design by simulating the mode shape, Qfactor and emission behaviour in organic, hybrid perovskite and III-V scintillating materials. By tailoring the structure geometry, it can be robustly tuned to match the emission characteristics of chosen materials. We start with considering ideal infinite structure supporting perfect BIC and we extend our model on finite sized structures and we discuss the limitations associated with the self-absorption and thickness of the structure. Our findings pave the way to cost-effective and efficient designs for scintillators in the UV-DB regime.

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Section: Discussionmentioning

confidence: 99%

Large-Area Photonic Bound State in the Continuum for Ultraviolet and Deep-Blue Emission for Organic, Inorganic, and Perovskite Scintillators

Kowal

Wong

Birowosuto

2023

IEEE Trans. Nucl. Sci.

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“…One of the two 3 × 3 mm 2 surfaces of each BGO pixel was optically coupled with NUV-HD MT silicon photomultipliers (SiPMs, FBK, Italy) (Merzi et al 2023) using silicone optical grease (BC-630, Saint-Gobain, USA). The silicone optical grease has a flat transmittance of ∼95% for wavelengths down to 280 nm with a refractive index of 1.465 (Kwon et al 2016, Romanchek et al 2020. The NUV-HD MT SiPMs have a square cell pitch of 40 μm and an area of 3.2 × 3.2 mm 2 .…”

Section: Bgo Scintillators and Colored Ptfe Tapesmentioning

confidence: 99%

Colored reflectors to improve coincidence timing resolution of BGO-based time-of-flight PET detectors

Lee,

Cherry,

Kwon

2023

Phys. Med. Biol.

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Time-of-flight (TOF) positron emission tomography (PET) detectors improve the signal-to-noise ratio of PET images by limiting the position of the generation of two 511-keV gamma-rays in space using the arrival time difference between the two photons. Unfortunately, bismuth germanate (BGO), widely used in conventional PET detectors, was limited as a TOF PET scintillator due to the relatively slow decay time of the scintillation photons. However, prompt Cerenkov light in BGO has been identified in addition to scintillation photons. Using Cerenkov photons for timing has significantly improved the coincidence timing resolution (CTR) of BGO. Based on this, further research on improving the CTR for a BGO-based TOF PET system is being actively conducted.Wrapping materials for BGO pixels have primarily employed white reflectors to most efficiently collect scintillation light. White reflectors have customarily been used as reflectors for BGO pixels even after Cerenkov light began to be utilized for timing calculations in pixel-level experiments. However, when the arrival-time differences of the two 511-keV annihilations photons were measured with pure Cerenkov radiators, painting the lateral sides of the radiators black can improve CTR by suppressing the reflection of Cerenkov photons. The use of BGO for TOF PET detectors requires simultaneously minimizing scintillation loss for good energy information and suppressing reflected Cerenkov photons for better timing performance. Thus, reflectors for BGO pixels should be optimized for better timing and energy performance.In this study, colored polytetrafluoroethylene (PTFE) tapes with discontinuous reflectance values at specific wavelengths were applied as a BGO reflector. We hypothesized that CTR could be enhanced by selectively suppressing reflected Cerenkov photons with an optimum colored reflector on the BGO pixel while minimizing scintillation photon loss. CTRs were investigated utilizing white and three colors (yellow, red, and green) PTFE tapes as a reflector. In addition, black-painted PTFE tape and enhanced specular reflector (ESR) film were investigated as reference reflector materials. When 3 × 3 × 20 mm3 BGO pixels were wrapped with the yellow PTFE reflector, the CTR was significantly improved to 365±5 ps from 403±14 ps measured with the conventional white PTFE reflector. Adequate energy information was still obtained with only 4.1% degradation in light collection compared to the white reflector. Colored reflectors show the possibility to further improve CTR for BGO pixels with optimum reflectance design. 

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“…In general, the SiPM and scintillator can be integrated using commercially available optical coupling gels or grease. More details on the performance parameters of optical coupling materials can be found in [42]. A typical readout architecture, whether in integrated circuits or discrete off-the-shelf components, is composed of a number of modules, and is shown in Figure 3.…”

Section: Introductionmentioning

confidence: 99%

A Comprehensive Survey of Readout Strategies for SiPMs Used in Nuclear Imaging Systems

2021

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Silicon photomultipliers (SiPMs) offer advantages such as lower relative cost, smaller size, and lower operating voltages compared to photomultiplier tubes. A SiPM’s readout circuit topology can significantly affect the characteristics of an imaging array. In nuclear imaging and detection, energy, timing, and position are the primary characteristics of interest. Nuclear imaging has applications in the medical, astronomy, and high energy physics fields, making SiPMs an active research area. This work is focused on the circuit topologies required for nuclear imaging. We surveyed the readout strategies including the front end preamplification topology choices of transimpedance amplifier, charge amplifier, and voltage amplifier. In addition, a review of circuit topologies suitable for energy, timing, and position information extraction was performed along with a summary of performance limitations and current challenges.

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Performance of Optical Coupling Materials in Scintillation Detectors Post Temperature Exposure

Cited by 14 publications

References 16 publications

Large-Area Photonic Bound State in the Continuum for Ultraviolet and Deep-Blue Emission for Organic, Inorganic, and Perovskite Scintillators

Large-Area Photonic Bound State in the Continuum for Ultraviolet and Deep-Blue Emission for Organic, Inorganic, and Perovskite Scintillators

Colored reflectors to improve coincidence timing resolution of BGO-based time-of-flight PET detectors

A Comprehensive Survey of Readout Strategies for SiPMs Used in Nuclear Imaging Systems

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