Cesium Iodide Research Articles

SPECTROMETRIC REGISTRATION OF X-RAY AND GAMMA RADIATION BY DETECTING MODULES “SILICON PLANAR DETECTOR–SCINTILLATOR”

The use of detection modules based on a silicon planar uncooled detector and a scintillator in combination with readout electronics makes it possible to create detection complexes for spectrometric detection of X-ray and gamma radiation in various fields of research, including nuclear physics, nuclear power engineering, high-energy physics, medicine, etc. The results of a study of detection complexes with silicon detectors with an active area of 22 and 55 mm and cesium iodide scintillators doped with thallium in the energy range from 50 keV to 0.662 MeV are presented.

Growth and Evaluation of Improved CsI:Tl and NaI:Tl Scintillators

Scintillators play an important role in radiation detection and imaging. Thallium-doped cesium iodide (CsI:Tl) and sodium iodide (NaI:Tl) are two of the major scintillators that have been used for many applications for many decades. In this paper, we will present an improved scintillation performance of Bridgman method-grown CsI(Tl) and NaI(Tl) crystals developed by Xtallized Intelligence, Inc. (XI, Inc.), and we will compare the performance with commercially available CsI:Tl and NaI:Tl. In a preliminary testing using MicroFJ−60035−TSV silicon photomultipliers (ON Semiconductor), the newly developed and improved 12.5 × 12.5 × 6 mm3 CsI:Tl crystal has shown an energy resolution of 4.8% (FWHM) at 662 keV, compared to 7.2% obtained by a commercially available CsI:Tl with a size of 12.5 × 12.5 × 25 mm3. The energy resolution of 5.4% (FWHM) at 662 keV is obtained for the newly improved NaI:Tl crystal, compared to 7% obtained by a commercially available ∅1″ × 1″ NaI(Tl). The comparison of the photo peak channel locations shows that the improvements in both CsI:Tl and NaI:Tl, developed by XI, Inc., have produced much larger signal amplitudes (roughly double), when compared to the commercially available CsI(Tl) and NaI:Tl. Improved decay time constants are presented as well.

Экспериментальные исследования характеристик фотокатодов ультрафиолетового диапазона спектра

Photoemission cells with high sensitivity to photons in the ultraviolet (UV) range of the spectrum have a wide range of practical applications in accelerator technology and generators of ultrashort electromagnetic pulses in the microwave range. The potential benefits of using UV photocathodes in these areas of technology are determined by such a combination of their properties as high electrical strength and high quantum efficiency. The report presents the results of experimental studies of the characteristics of photocathodes based on magnesium-barium (Mg-Ba) alloys and cesium iodide (CsJ). Photocathodes were fabricated by thermal vacuum sputtering on polished stainless steel substrates. It is shown that the dielectric strength of vacuum gaps with UV cathodes is significantly higher than with antimony-cesium cathodes in the visible range of the spectrum (for CsJ cathodes – 2.5 times, for Mg-Ba cathodes – more than three times). The quantum efficiency of Mg-Ba cathodes is ~1% at a wavelength of 247 nm, and that of CsJ cathodes is 7.5% at a wavelength of 196 nm. The results of studies of the dynamics of a decrease in the quantum efficiency of photocathodes under repetitively pulsed irradiation with laser pulses with a fluence 6 μJ/cm2. The characteristics of photocathodes are compared from the point of view of their practical applications.

Theoretical comparison of energy-resolved and digital-subtraction angiography.

X-ray coronary angiography is a sub-optimal vascular imaging technique because it cannot suppress un-enhanced anatomy that may obscure the visualization of coronary arterydisease. The purpose of this paper is to evaluate the theoretical image quality of energy-resolved x-ray angiography (ERA) implemented with spectroscopic x-ray detectors (SXDs), which may overcome limitations of x-ray coronaryangiography. We modeled the large-area signal-difference-to-noise (SDNR) of contrast-enhanced vasculature in ERA images and compared with that of digital-subtraction angiography (DSA), which served as a gold standard vascular imaging technique. To this end, we used calibrated numerical models of the response of cadmium telluride SXDs including the effects of charge sharing, electronic noise, and energy thresholding. Our models assumed zero scatter, no pulse pile up and small signals such that image contrast is approximately linear in the area density of contrast agents. For DSA, we similarly modeled x-ray detection by cesium iodide energy-integrating detectors using validated numerical models. For ERA, we investigated iodine and gadolinium (Gd) contrast agents, two-material and three-material decompositions, analog charge summing for charge sharing correction, and optimized image quality with respect to the tube voltage and energy thresholds assuming cadmium telluride SXDs with three energybins. Our analysis reveals that a three-material decomposition using iodine contrast agents will require x-ray exposures that are approximately 400 times those of DSA to achieve the same SDNR as DSA in coronary applications, and is therefore not feasible in a clinical setting. However, three-material decompositions with Gd contrast agents have the potential to provide SDNR that is ∼45% of that of DSA for matched patient air kerma. For two-material decompositions that suppress soft-tissue, ERA has the potential to produce images with SDNR that is 50%-75% of that of DSA for matched patient air kermas but lower levels of tube loading. Achieving these SDNR levels will require the use of analog charge summing for charge sharing correction, which increased SDNR by up to a factor of 1.7 depending on the contrast agent and whether or not a two-material or three-material decomposition wasassumed. We conclude that three-material ERA implemented with Gd contrast agents and two-material ERA implemented with either iodine or Gd contrast agents, should be investigated as alternatives to DSA in situations where motion artifacts preclude the use of DSA, such as in coronaryimaging.

Optimized perovskite active layer morphologies and crystallization by doping cesium iodide for high-performance bulk heterojunction solar cells and X-ray detectors

Organic-inorganic hybrid methylammonium lead iodide perovskite (MAPbI 3 ) has attracted widespread attention for its potential use in a range of optoelectronic devices. In this paper, we describe the fabrication of inverted-type perovskite/fullerene planar heterojunction perovskite solar cells and X-ray detectors where a small amount of cesium iodide (CsI) was added to the MAPbI 3 precursor solution. The appearance and crystal structure of the constructed perovskite active layer were carefully studied by microscope and X-ray diffraction measurements, respectively. The results reveal that the CsI additive can control the size and aggregation behavior of the perovskite crystals, helping to form a smoother perovskite film. Thus, the constructed perovskite solar cell with its Cs 0.1 MA 0.9 PbI 3 active layer (AC) revealed a power conversion efficiency (PCE) of 11.16 ± 0.13%, which is a significant improvement over conventional planar heterojunction devices that use pristine MAPbI 3 AC (PCE 9.12 ± 0.11%). We also fabricated an X-ray detector using the same Cs 0.1 MA 0.9 PbI 3 , this achieved a maximum sensitivity of 3.26 mA/Gy cm 2 . Density functional theory calculations investigate the origin of the enhancement of device performance characteristics. Interestingly, the results show that perovskite surfaces constructed with a suitable amount of CsI can effectively enhance charge extraction and reduce charge carrier recombination. This work provides an efficient way to improve carrier transfer, which will inspire other perovskites optoelectronic applications. • We have synthesized smooth and highly crystalline perovskite thin films by incorporating an appropriate amount of CsI. • We fabricated inverted-type perovskite/PCBM hybrid solar cells and X-ray detectors using cesium-doped perovskites. • Competitive efficiency of 11.16 ± 0.13% was achieved for constructed perovskite solar cell with Cs 0.1 MA 0.9 PbI 3 AC. • Invented X-ray detector with Cs 0.1 MA 0.9 PbI 3 AC exposed a high sensitivity of 3.26 mA/Gy·cm 2 .

Impact of the Dresden-II and COHERENT neutrino scattering data on neutrino electromagnetic properties and electroweak physics

Coherent elastic neutrino-nucleus scattering (CEνNS) represents a powerful tool to investigate key electroweak physics parameters and neutrino properties since its first observation in 2017 by the COHERENT experiment exploiting the spallation neutron source at Oak Ridge National Laboratory. In light of the recent detection of such a process with antineutrinos produced by the Dresden-II reactor scattering off a germanium detector, we revisit the limits so far set on the neutrino magnetic moments, charge radii and millicharges as well as on the weak mixing angle. In order to do so, we also include the contribution of elastic neutrino-electron scattering, whose effect becomes non negligible in some beyond the Standard Model theories. By using different hypotheses for the germanium quenching factor and the reactor antineutrino flux, we provide a measurement of the weak mixing angle at the low-energy scale of the Dresden-II reactor experiment and, thanks to a combined analysis with the latest cesium iodide and argon data set released by the COHERENT Collaboration, we deliver updated limits for the neutrino electromagnetic properties. Interestingly, we are able to set a new best upper limit on the electron neutrino charge radius and significantly improve the other CEνNS-related limits on the neutrino electric charge and magnetic moment.

X-ray radioluminescent battery with near milliwatt output power using CsI:Tl single crystal scintillator

Low output power has long been the bottleneck of micro-radioisotope batteries as power supplies for the wireless sensor network, implantable medical equipment, and outer space exploration. Recently, x-ray radioluminescent batteries demonstrated the great potential to break the deadlock. In this work, we fabricated an x-ray radioluminescent battery with near milliwatt output power and demonstrated various potential applications. A 100% improvement on the conversion efficiency of 2.46% and the highest output power of 136.1 μW/cm2 were achieved when adopting a thallium doped cesium iodide (CsI:Tl) single-crystal scintillator in the battery. Subsequently, a 2 × 2 battery array was fabricated with a maximum output power of 466.9 μW and was used to power devices including micro-LEDs and a wireless sensor system with temperature monitoring. This demo system shows the feasibility of x-ray radioluminescent batteries as a long-lifetime micropower. The tremendous progress will draw broad attention on micro-nuclear batteries and inspire further exploration on the applications in the field of medical devices, space explorations, and Internet of Things.

Multimodality system of x-ray and fluorescence based on Fourier single-pixel imaging for small animals.

.Significance: The multimodality imaging system has become a powerful tool for in-vivo biomedical research. However, a conventional multimodality system generally employs two independent detectors, which is costly and bulky. Meanwhile, the geometric cocalibration and image registration between the imaging modalities are also complicated.Aim: To acquire the multimodality images for small animals with only one visible light sensed single-pixel detector.Approach: The system is built based on a structured detection Fourier single-pixel imaging architecture. A cesium iodide doped with thallium [CsI(Tl)] scintillator plate is placed behind the sample in x-ray imaging, so the x-ray images can be converted to be visible and sensed with the same single-pixel detector as applied in fluorescence imaging.Results: The spatial resolution of x-ray imaging was measured to be 1.81 mm, the sensitivity and the imaging depth of fluorescence imaging was evaluated to be and 4 mm, respectively. In vivo multimodality imaging of a C57BL/6 female mouse bearing tumor targeted with mCherry was carried out.Conclusions: We proposed an x-ray and fluorescence multimodality imaging system for small animals via the structured detection FSI architecture. The system is low cost, with a more compact structure, and free of image registration from different modalities. In vivo multimodality imaging results of a mouse bearing tumor demonstrate its capability for small animal research.

Colloidal synthesis of cesium iodide nanocrystals for visible-enhanced photodetection applications

In this study, cesium iodide (CsI) nanoparticles were synthesized for the first time by pulsed laser ablation in ethanol at various laser fluences . The structural and optical properties of the CsI nanoparticles were studied as a function of laser fluence. The x-ray diffraction (XRD) results confirm the formation of crystalline CsI with a cubic structure along (110) plane. The optical absorbance spectra showed two absorption peaks at 291 and 363 nm. The optical energy gap of CsI NPs decreases as laser fluence increases. Transmission electron microscope studies show that the synthesized nanoparticles have a spherical shape and the mean particle size prepared at 22.9, 33.1 and 43.3 J/cm 2 was 23, 25, and 28 nm, respectively. Scanning electron microscope results reveal the formation of nanosized spherical CsI nanoparticles. The fluorescence emission data of CsI shows two main bands centered at 339 nm and 387 nm. Raman spectra show three Raman peaks located at 15, 26 and 44 cm −1 . The zeta potential results confirm that the CsI NPs prepared at 33.1 J/cm 2 have good stability. The current-voltage characteristics of CsI/Si heterojunctions show rectification properties, and the illuminated current-voltage shows that the maximum photocurrent was found for a photodetector fabricated at 33.1 J/cm 2 . The maximum responsivity and detectivity of the photodetector are 1.66 A/W and 5.5 × 1012 Jones at 400 nm, respectively, for a photodetector prepared at 33.1 J/cm 2 . A quantum efficiency of 5.16 × 10 2 % at 400 nm is reached for a photodetector prepared at 33.1 J/cm 2 . The Hall effect shows that the synthesized CsI NPs are p-type and the highest hole mobility was found for a sample prepared at 33.1 J/cm 2 . • Colloidal Cesium iodide nanoparticles were synthesized by laser ablation in liquid. • The effect of laser fluence on the properties of CsI was investigated. • Different morphologies of CsI nanocrystals were obtained. • High performance CsI nanostructure/Si photodetector was fabricated.

Characterization of Flexible Amorphous Silicon Thin-Film Transistor-Based Detectors with Positive-Intrinsic-Negative Diode in Radiography.

Low-dose exposure and work convenience are required for mobile X-ray systems during the COVID-19 pandemic. We investigated a novel X-ray detector (FXRD-4343FAW, VIEWORKS, Anyang, Korea) composed of a thin-film transistor based on amorphous silicon with a flexible plastic substrate. This detector is composed of a thallium-doped cesium iodide scintillator with a pixel size of 99 μm, pixel matrix of 4316 × 4316, and weight of 2.95 kg. The proposed detector has the advantages of high-noise characteristics and low weight, which provide patients and workers with an advantage in terms of the dose and work efficiency, respectively. We performed a quantitative evaluation and an experiment to demonstrate its viability. The modulation transfer function, noise power spectrum, and detective quantum efficiency were identified using the proposed and comparative detectors, according to the International Electrotechnical Commission protocol. Additionally, the contrast-to-noise ratio and coefficient of variation were investigated using a human-like phantom. Our results indicate that the proposed detector efficiently increases the image performance in terms of noise characteristics. The detailed performance evaluation demonstrated that the outcomes of the use of the proposed detector confirmed the viability of mobile X-ray devices that require low doses. Consequently, the novel FXRD-4343FAW X-ray detector is expected to improve the image quality and work convenience in extended radiography.

Present outcome from the NUMEN R&D phase

The NUMEN experiment aims at measuring double charge exchange reaction cross sections using heavy-ion beams of unprecedented intensity on specific isotopes. In order to get data-sets with good statistical significance from challengingly low cross sections it asks for the upgrade of the pre-existing magnetic spectrometer MAGNEX at INFN-LNS, in Catania. These reactions prove to be a way of getting information on the nuclear matrix elements of the neutrino-less double beta decay, the most promising probe to establish the Majorana or Dirac nature of the neutrino, and to evaluate the effective neutrino mass. A new setup for the target system is under development and adequate detectors are under study for the tracking and the identification of heavy ions at the expected rate up to 5 Mpps and for gamma-ray measurements. The tracker is a time projection chamber with electron amplification based on a triple Thick Gas Electron Multiplier (THGEM) foil, the particle identification is performed with telescopes composed of Silicon Carbide (SiC) and Thallium doped Cesium Iodide (CsI(Tl)) sensors, the gamma-ray detection is sustained with Cerium doped Lantanum Bromide (LaBr3(Ce)) scintillator detectors. Here a selection of results of the R&D phase and the integration study are presented.

CRYSTAL CONFIGURATION DEPENDENCE OF CSI(TL) SCINTILLATION DETECTORS ON ENVIRONMENTAL DOSE RATE MEASUREMENT.

The crystal configuration dependence of thallium-doped caesium iodide (CsI(Tl)) scintillation detectors was analysed on an ambient dose equivalent (H*(10)). H*(10) were systematically calculated in various crystal conditions for aspect ratios and sizes in a virtual environment contaminated by radionuclides to investigate directional characteristics by comparing the H*(10)s with the typical irradiation geometries in anterior-posterior (AP), lateral (LAT), rotational (ROT) and isotropic (ISO). The simulation revealed that H*(10) obviously changes according to the crystal configuration and cuboidal CsI(Tl) scintillation detectors with specific aspect ratios could be applied to environmental dose rate measurement without further changes in the calibration procedure.

Decoupling engineering of formamidinium-cesium perovskites for efficient photovoltaics.

Although pure formamidinium iodide perovskite (FAPbI3) possesses an optimal gap for photovoltaics, their poor phase stability limits the long-term operational stability of the devices. A promising approach to enhance their phase stability is to incorporate cesium into FAPbI3. However, state-of-the-art formamidinium–cesium (FA–Cs) iodide perovskites demonstrate much worse efficiency compared with FAPbI3, limited by the different crystallization dynamics of formamidinium and cesium, which result in poor composition homogeneity and high trap densities. We develop a novel strategy of crystallization decoupling processes of formamidinium and cesium via a sequential cesium incorporation approach. As such, we obtain highly reproducible, highly efficient and stable solar cells based on FA1–xCsxPbI3 (x = 0.05–0.16) films with uniform composition distribution in the nanoscale and low defect densities. We also revealed a new stabilization mechanism for Cs doping to stabilize FAPbI3, i.e. the incorporation of Cs into FAPbI3 significantly reduces the electron–phonon coupling strength to suppress ionic migration, thereby improving the stability of FA–Cs-based devices.

Atomic Layer Deposition of CsI and CsPbI3

Cesium iodide (CsI) is a well-established scintillator material that also serves as a precursor for all-inorganic halide perovskite solar absorbers, such as CsPbI3. However, the lack of conformal and scalable methods to deposit halide perovskite thin films remains a major challenge on their way to commercialization. In this work, we employ atomic layer deposition (ALD) as the key method due to its inherent scalability to large areas and complex-shaped surfaces. We demonstrate two new ALD processes for the deposition of CsI and CsPbI3 thin films. The CsI process relies on cesium bis(trimethylsilyl) amide (Cs(btsa)) and tin(IV) iodide (SnI4) as precursors and yields high-purity, uniform, and phase-pure thin films. This process works in a wide temperature range (140–350 °C) and exhibits a large growth per cycle value (GPC) of 3.3 Å (85% of a CsI monolayer). Furthermore, we convert CsI into CsPbI3 perovskite by exposing a CsI film to our earlier PbI2 ALD process. We demonstrate the deposition of phase-pure γ- or δ-CsPbI3 perovskite thin films, depending on the applied deposition temperature and number of PbI2 cycles. We believe that the ALD-based approach described in this work will offer a viable alternative for depositing perovskite thin films in applications that involve complex high aspect ratio structures or large substrate areas.

A two-dimensional array detector for determining the direction to gamma-ray source

With increasing demand in the nuclear technology field for locating isolated radioactive sources, numerous studies have focused on the array detector. Given the concerns over the limited performance that only determined the horizontal direction of traditional direction algorithms, an improved algorithm based on the two-dimensional (2D) array detector is proposed for determining the gamma-source direction in the full 2π hemisphere field of view. Coupling a 2 × 2 Cesium Iodide Thallium [CsI(Tl)] crystal array with a silicon photomultiplier array, a prototype of the array detector was designed and implemented. For verification of its directional performance, Geant4 simulations and experiments were performed. The results verified that the detector is capable of simultaneously determining the horizontal and vertical direction of gamma-ray source with an accuracy around 1∘∼5∘. In addition, the simulation results showed that the detector can determine the direction of gamma-ray sources with a wide energy range from 30 keV to 3000 keV.

Dual-Resistance of Ion Migration and Moisture Erosion via Hydrolytic Crosslinking of Siloxane Functionalized Poly(Ionic Liquids) for Efficient and Stable Perovskite Solar Cells

Dual-Resistance of Ion Migration and Moisture Erosion via Hydrolytic Crosslinking of Siloxane Functionalized Poly(Ionic Liquids) for Efficient and Stable Perovskite Solar Cells

Aerial and Collimated Sensor Radiological Mapping Following Dispersal of Activated Potassium Bromide.

The exposure rate distribution was quantified over a site of three activated potassium bromide radiological dispersal device detonations at the Idaho National Laboratory Radiological Response Training Range with unmanned aerial vehicle (UAV) and ground-based methods. Discussions on the methods' survey characteristics, such as survey time, data spatial resolution, and area coverage, serve to inform those concerned with radiological response and cleanup efforts. Raster scans over the site at 4 m s-1 with 6 m between passes at an altitude of 4 m above ground level were executed with a 2.54 cm × 2.54 cm × 7.62 cm cesium iodide, sodium-doped [CsI(Na)] sensor mounted to a UAV. Exposure rates were calculated from the spectra obtained by the CsI(Na) using a flux unfolding method. Data obtained from the UAV raster were interpolated to produce a continuous exposure rate map across the site. The activity on the ground, inferred from collimated, ground-based sensor (Nomad) measurements in previous work, was used to calculate exposure rate distributions at the same altitude as the UAV-mounted CsI(Na) sensor. Agreement between Nomad and UAV exposure rate distributions is observed at rates up to 1.0 mR h-1 after corrections for ground effects were implemented on the Nomad data. Discrepancies in exposure rate contours are present at higher rates, directly above the detonation locations. In areas of high exposure rate gradients, it is anticipated that a faster UAV-mounted sensor and more refined scans by the UAV will improve characterization of the distribution.

High-performance Self-powered Perovskite Photodetector Based On Cesium Iodide Doped Spiro-OMeTAD Hole Transport Material

Hole transport materials play an essential role in the performance of perovskite detectors (PDs). Therefore, hole transport materials with excellent performance can significantly promote photoinduced holes' extraction rate and mobility. Spiro-OMeTAD, a small organic molecular material, has high solubility and excellent film-forming properties and is ideal for the hole transport layer (HTL) of photodetectors. In this work, a small amount of CsI is introduced into Spiro-OMeTAD together with Li-TFSI and TBP as additives. It is found that CsI and TBP formed a complex, which inhibited the agglomeration of Li-TFSI in Spiro-OMeTAD, thus preventing the rapid evaporation of TBP from leaving some cracks Spiro-OMeTAD. The photodetectors exhibit broadband response from near-ultraviolet to near-infrared (300–800 nm), achieving fast response (rise/fall time is 54.1/10.7 μs) and low dark current density (9.72 ×10−10 A cm−2). The detector can be self-powered at zero bias voltage, the external quantum efficiency (EQE) is 88%, the Responsivity (R) is 0.48 A W−1, and the detectivity (D*) is close to 2.7 × 1013 Jones. When the photovoltaic detector is placed in a nitrogen-filled glove box without special packaging for more than two months, the EQE remains 98.1% of the original. This study provides a simple method for fabricating a large area of high-performance planar PDs.

Phase transformation barrier modulation of CsPbI3 films via PbI3− complex for efficient all-inorganic perovskite photovoltaics

Cesium lead iodide (CsPbI3) has gained great attention due to its thermal stability and appropriate bandgap (≈1.73 eV) at black (γ) phase potentially suitable for tandem solar cells. However, it is challenging to obtain CsPbI3 film with desired black phase. Herein, we fabricate kinetically favorable γ-CsPbI3 thin films by stoichiometry modulation, where in-situ 2D GIWAXS measurement was innovatively performed to illustrate the phase transition process of the precursor films, to aid a full picture study on the entire film evolution process. Conceptually different from introducing other extrinsic species, the cogenetic doping by excessive cesium iodide is found to tailor energy barriers for phase transformations during both the film formation and ageing process simultaneously. During film growth, excessive CsI affects the formation of Pb−I complex in the precursor solution, which facilitates the δ to γ phase transformation. Also, the Cs-rich resultant film could suppress γ to δ phase transformation. The corresponding CsPbI3 solar cells deliver a PCE of 16.68% without performance loss at continuous maximum power point output (MPP) for ~175 h under continuous illumination in a N2 glovebox. This work highlights the importance of precursors chemistry and provides guidelines to adjust the phase transformation barrier in CsPbI3 films without any foreign additives.

Ambient air processed highly oriented perovskite solar cells with efficiency exceeding 23% via amorphous intermediate

The preparation of perovskite solar cells (PSCs) in ambient air can effectively reduce the production cost and is more conducive to commercial production. However, ambient air fabrication of perovskite film always causes rough surface and nonuniform coverage which increase non-radiative recombination in PSCs. In this work, we adopted an amorphous intermediate strategy in lead iodide (PbI2) film to prepare the oriented perovskite film under ambient air condition. This amorphous intermediate formed by the interaction force between cesium iodide (CsI) and PbI2, which promotes perovskite phase inversion in perovskite precursor film and finally the perovskite grains grow perpendicular to the substrate in the ambient air. As a result, this ambient air processed-PSCs with the perovskite film passivated with butylammonium iodide (BAI) obtained a power conversion efficiency (PCE) of 23.46%, which is equivalent to that of two-step preparation in glovebox. Furthermore, the PSC maintains 85% of its initial efficiency under more than 1000 h of continuous illumination and processes a recoverable PCE at temperatures below 65 °C under photothermal cycling stress.