Sapphire Window Research Articles

Focal point technology: Controlling treatment depth and pattern of skin injury by a novel highly focused laser

Selective photothermolysis has limitations in efficacy and safety for dermal targets. We describe a novel concept using scanned focused laser microbeams for precise control of dermal depth and pattern of injury, using a 1550nm laser that generates an array of conical thermal zones while minimizing injury to the epidermis. To characterize the conical thermal zones invivo and determine safe starting parameters to transition to a second phase to explore potential clinical indications. A focused toroidal (ring) laser beam was delivered through a cold sapphire window, sparing epidermal injury in a central zone. Pulse energy, lesion depth, density, and energy delivery were titrated in exvivo human skin and subsequently on the backs of 21 human subjects. Histology showed microscale patterns of thermal injury, which varied predictably with laser parameters. Time-course healing through histology and skin surface imaging demonstrated the ability of the device to deliver high energies without sequelae. Clinical data are currently being collected to further explore the safety and efficacy of the device. The 1550nm laser with focal point technology enables precise control of lesion depth while simultaneously sparing a large portion of the epidermis, lowering the risk of adverse effects.

Ultrasonic micro-injection moulding: characterisation of interfacial friction by varying feedstock shape and high-speed thermal imaging for microneedle feature replication

This study explores the interfacial friction in ultrasonic micro-injection moulding by using different polymer feedstock shapes, characterisation of micromoulding melts through thermal imaging and assessing microneedle feature replication. Industry standard polypropylene pellets and discs with different thicknesses were used for varying the amount of interfacial friction during sonication. High-speed thermal imaging and tooling containing sapphire windows were used to visualise the melt characteristics. Moulded products were characterised using laser-scanning confocal microscopy to quantify microneedle replication. The study demonstrates that (i) the interfacial area for the different feedstock shapes affects the heating in ultrasonic micro-injection moulding significantly, (ii) disc-shaped feedstocks result in initially higher flow front velocities and exhibit dominance of viscoelastic heating over interfacial friction and (iii) industrial pellet feedstocks provide a good combination interfacial friction and viscoelastic heating and more viscosity reduction in overall leading to better microreplication efficiency. The results presented could have a significant impact on the process development of ultrasonic micro-injection moulding where process repeatability can be improved by controlling the interfacial friction. The research provides an essential contribution to the development of this process, where interfacial frictional heating can be tailored specifically for miniature functional components, offering improved precision and reduced energy use when compared with conventional methods.

Terahertz refractometry of hard-to-access objects using the sapphire endoscope suitable for harsh environments

While terahertz (THz) technology offers a variety of applications in medical diagnosis, nondestructive testing, and quality control, its acceptance in these practical fields is hampered by the absence of endoscopic systems, capable of sensing the complex refractive index of the hard-to-access objects. In this paper, we develop the THz endoscope based on the hollow-core antiresonant waveguide, formed by a polytetrafluoroethylene (PTFE)-coated sapphire tube with the outer end closed by a monolithic sapphire window. The endoscope is attached to the backward wave oscillator spectrometer to measure the sample reflectivity. By studying the well-known liquid and solid samples, we demonstrate that analysis of the Fabry–Pérot resonance in the measured reflection spectra makes it possible to quantify the complex refractive index of an analyte. Thanks to the advanced chemical inertness and thermal strength of sapphire and PTFE, the developed endoscope is capable of operation in harsh environments, which broadens the range of its applications. Our findings pave the way for the THz technology use in a number of demanding practical fields.

Development status of the in-situ measurement system for ortho-to-parahydrogen fractions for the ESS cryogenic moderator system

The Cryogenic Moderator System (CMS) is equipped with a catalyst to convert hydrogen from the ortho state to the para state in order to keep desirably high parahydrogen fractions of 99.5%. An in-situ measurement system for the ortho and para fractions of liquid hydrogen (OPMS) by means of a Raman spectroscopy with an accuracy of 0.1% is being developed to detect any undesirable shift towards a high orthohydrogen fraction caused by neutron scattering driven para-to-ortho back conversion. We have demonstrated that our developed sapphire window, through which the laser and backscattered photon travel, has endured the required pressure and thermal cycles in a liquid hydrogen environment. Meanwhile, a Raman optics system has been developed using normal hydrogen. Eventually, we have succeeded in detecting the parahydrogen peak at J = 4, which is our primary goal, because the peak ratio of parahydrogen at 1245 cm−1 to ortho hydrogen at 587 cm−1 corresponds to 0.5%. It can be expected that it would achieve our requirement for liquid hydrogen with higher density.

Post-process annealing of MgAl2O4 spinel optics for high energy laser windows

Magnesium aluminate (spinel) has been investigated as a low-absorption material for applications such as high-strength windows, armor, and high energy laser (HEL) apertures. To develop spinel for HEL applications, it is critical to lower the absorption of the lasing medium at the operating wavelength to reduce optical path distortion. In this work, post-processing of spinel via annealing is investigated to lower the absorption at 1.064 μm. Specifically, spinel optics are annealed in ambient air, oxygen, and nitrogen at temperatures of 1000–1400 °C and their transmission, absorption and photoluminescence properties are measured. This annealing process reduces the absorption by 73% from 463 ppm/cm to 126 ppm/cm and results in optics that have transmission within 1% of the Fresnel limit over the 1.0–2.0 μm wavelength range. The resulting optical characterizations imply a direct oxidation of Fe2+ to Fe3+ and the formation of VO1+ at distorted octahedral sites to mediate this reaction that results in lower optical absorption in the near-IR (NIR). Further, performance of equibiaxial flexure testing and corresponding Weibull analysis indicates that spinel manufactured using this method can outperform sapphire windows from a design strength perspective.

Effects of the thermal treatments on the optical properties of SiO2 anti-reflective coatings on sapphire windows

The SiO2 films were deposited on sapphire substrates using radio frequency (RF) magnetron sputtering to enhance the mid-wave infrared (IR) transmittance. The effects of thermal treatments by annealing and in-situ heating on the SiO2 films were investigated. After annealing at 600 °C, the surface morphology, microstructure, chemical states, and optical constants were investigated. No obvious microcracks or delamination were observed on the film surfaces, indicating excellent adhesion to the sapphire substrates. With an increase in the annealing time, gradual oxidation of Si atoms within the SiO2 thin films occurred, resulting in the release of OH groups and evaporation of moisture. The refractive index exhibited slight changes, while the extinction coefficient showed a significant reduction, thus the transmittance was improved. According to the in-situ heating tests from the annealed samples, it revealed a slight increase in average transmittance with prolonged annealing time. Finally, we assessed the performance of the annealed samples by rapid heat shock to 600 °C at a very short time, which demonstrated outstanding optical performance and heat-resistant properties. The present work supports the feasibility of applying the SiO2 films under harsh high-temperature environments.

Hydrogen concentration measurements using spark induced breakdown spectroscopy in a real engine

This study develops spark induced breakdown spectroscopy (SIBS) for measurements of direct injected hydrogen concentration in a multi-cylinder engine operated at real conditions. To this end, calibration is performed in the air excess ratio (λ) range of 2.1 ∼ 2.9 and simultaneously, high-speed schlieren imaging of laminar hydrogen flame propagation is performed in an optical high-pressure constant volume combustion chamber (CVCC). To achieve real engine applications, the SIBS is further developed using a modified conventional spark plug for sapphire window insertion onto the positive electrode and guided arc formation via a newly designed nipple type ground electrode. Specifically, the peak spectra intensity ratio of Hα (656 nm) to O (777 nm) is used for calibration, which shows a linear correlation with λ. For the first time, the calibrated SIBS is applied to a real engine operated at 46.2 ∼ 63.9 Nm load and 2000 rpm with 3.5 MPa hydrogen direct injection. The results show lower local λ than the global λ despite early injection timing of 165 crank angles before top dead centre, indicating a significant influence of in-cylinder flow motion on the spatial distribution of hydrogen-air mixtures.

Unraveling Effects of Current Density and Silicon on Silicon-Graphite Composite Anodes By in-Situ Synchrotron X-Ray Diffraction

The development of lithium-ion batteries (LIBs) with high capacity and rate capabilities is imperative to meet energy demands for both transport and grid storage in the future. Due to its relative abundance and excellent cycling stability, state of the art LIBs contains graphite as the main anode component. However, graphite suffers from a low theoretical specific capacity of 372 mAhg-1 [ 1 ]. Alternatively, silicon (Si) has emerged as a promising energy-dense anode material with a theoretical specific capacity 10 times higher than graphite, but their widespread application is impeded by low electrical conductivity and extremely poor cycling stability due to large volume variations when alloying with lithium during electrochemical cycling [ 2 ]. Interestingly, silicon-graphite (SiG) composites have been pinpointed as promising options for producing improved anodes, which aims to combine graphite’s high electronic conductivity and structural stability with silicon’s high specific capacity. As expected, increasing the silicon content of SiG anodes reduces the cycling stability [3]. Optimization of SiG with respect to silicon content and utilization of silicon is not straightforward, and a comprehensive analysis on the effect of variations of silicon content and current density on SiG andoes is key. To investigate these interactions, in-situ synchrotron X-ray diffraction (XRD) analysis of composite anodes with varying silicon content at increasing c-rates was performed.In situ experiments were performed at BM01 of the European Synchrotron Radiation Facility (ESRF). An in-situ electrochemical cell consisting of two current collectors, in which the lower current collector is made of brass and the upper current collector is made of stainless steel, was utilized [ 4 ]. A half-cell was then assembled between the two current collectors in a coin cell configuration using lithium metal as the counter electrode and a glass fiber separator. 1M LIFSI in 1:1 vol EC: DMC was used as the liquid electrolyte. The current collectors each have a thin single crystal sapphire window that is mostly transparent to X-ray but have distinct signals that can be masked out in post-processing. To avoid diffraction signal from the underlying copper current collector of the electrode, the composite anode consists of electrodes cast on copper foil as well as a free-standing section. The assembled cell was galvanostatically cycled between 1 V and 50 mV while XRD data was acquired. In this study 4 different electrodes containing 0, 20 %wt., 30 %wt. and 70 %wt. of Si in the active material of the electrode were cycled at C/5, C/2, 1C and 2C rates.Analysis of the XRD results showed that tracking of the evolution of graphite main reflections during electrochemical cycling while completely avoiding the copper signal has been achieved. The degree of graphite lithiation was tracked by following the distinct 002, 100 and 110 peaks of graphite where phase transitions to LiC12 and LiC6 can be identified. Consistent with the results of other studies, graphite has been found to be both lithiated and delithiated at lower potentials than silicon [ 3 ]. Increasing silicon content was found to decrease the degree of graphite lithiation as silicon will be preferentially lithiated. Increasing the current density was found to reduce the overall degree of lithiation of graphite as the specific capacity decreases and the material is not sufficiently lithiated to undergo the expected phase transitions. This study has therefore unraveled the effect of silicon content and current density on composite anode behavior which could allow for the design of better next-generation composite anodes. Tarascon, J.-M. & Armand, M. Issues and challenges facing rechargeable lithium batteries. Nature 414, 359–367 (2001). Ashuri, M., He, Q. & Shaw, L. L. Silicon as a potential anode material for Li-ion batteries: where size, geometry and structure matter. Nanoscale 8, 74–103 (2015). Moyassari, E. et al. The Role of Silicon in Silicon-Graphite Composite Electrodes Regarding Specific Capacity, Cycle Stability, and Expansion. J. Electrochem. Soc. 169, 010504 (2022). Drozhzhin, O. A. et al. An electrochemical cell with sapphire windows for operando synchrotron X-ray powder diffraction and spectroscopy studies of high-power and high-voltage electrodes for metal-ion batteries. J. Synchrotron Radiat. 25, 468–472 (2018). Figure 1

Fused silica as an anti-fouling material for oil sands optical instruments

Optical instruments have application in many chemical industries for use in inline observation, measurement, and process control for product and waste streams. Typically, these instruments are fitted with sapphire windows which offer extreme hardness, optical transparency and inertness but can be susceptible to fouling with hydrocarbons in the streams. This work explored the potential of fused silica as an alternative anti-fouling material for optical instrument windows for use in aqueous streams containing hydrocarbons. The advantage of fused silica is that it offers adequate hardness and transparency while retaining chemically reactive silanol groups on its surface. Closed loop experiments conducted with oil sands mature fine tailings (MFT) containing residual bitumen, a hydrocarbon known to cause severe fouling of optical windows, demonstrated no fouling issue on fused silica. The hydrophilicity of the optical surface increased following exposure to the mildly alkaline MFT. We hypothesized that in alkaline aqueous streams the silanol groups are deprotonated to create a negatively charged surface, thereby introducing a repulsive force between the surface and the negatively charged hydrocarbon droplets and increasing the hydrophilicity of both materials. Contrarily, the relatively inert sapphire is limited in its capacity to form negative surface charges and consistently fouled with bitumen. When silanol groups on the fused silica were removed via fluoro-functionalization, it resulted in complete fouling of the optical surface. Finally, bitumen fouling was observed on both fused silica and sapphire surfaces in neutral aqueous environments compared to none on the fused silica in an alkaline environment.

Toward Understanding Interfacial Phenomena of Anion Exchange Membrane Water Electrolyzers: Investigating the Role of Electrolyte pH Gradient with Operando Raman Spectroscopy

There is growing industrial appeal of anion exchange membrane water electrolyzers (AEMWEs) to produce hydrogen. A significant challenge remains that AEMWE durability testing is not standardized, and more minute interfacial degradation mechanisms between ionomer, catalyst, membrane, and electrolyte are not well characterized. Of particular interest is the impact of electrolyte selection on the polarization performance. There is a general desire to achieve reliable operation with environmentally obtained saltwater as the electrolyte, although this presents numerous challenges manifesting in typically poor long-term durability. Saltwater presents complexities in determining electrolyzer component interfacial phenomena.Performance of AEMWEs is typically benchmarked with hydroxide or carbonate solutions, therefore providing more direct opportunities to study fundamental mechanisms with regards to interactions between surfaces. Of particular interest is the presence of electrolyte anion concentration gradients that depend on the polarization state of the oxygen evolution reaction electrode (OER). We demonstrated in our early work with operando Raman probing of a custom designed spectroelectrochemical cell that there is initial evidence of spatially resolved anion gradients from the OER electrode surface into bulk electrolyte in a half cell configuration. We hypothesize that local pH changes near an electrode surface may impact the polarization via transport limited ion exchange and the relative overpotential of the overall cell, ultimately leading to an iterative and long-term contribution to decaying cell durability.We continue our work with a series of in-situ Raman experiments with a full cell configuration: OER electrode with PGM free catalyst, hydrogen evolution reaction (HER) electrode with PGM free catalyst, and anion conductive polymer membrane. Both electrodes also contain an ionically conductive polymer, or ionomer, that serves as a binder. By increasing the complexity of the system to match that of an industrially relevant configuration, we aim to probe the spatially resolved pH gradient with both potassium hydroxide and potassium carbonate solutions of varying concentrations. We utilized a custom, 3D printed, flow cell design comprising a sapphire observation window and isolated electrolyte flow chambers.Operando Raman spectroscopy measurements were conducted primarily with potassium carbonate solutions by tracking the spatially resolved changes in relative peak intensity of carbonate and bicarbonate signatures. With regards to the carbonate-bicarbonate equilibrium, we calculate changes in pH as the probe approaches the surface of an electrode. We finally connect our findings to a proposed mechanism for the interfacial phenomena relative to cell durability as a function of concentration changes and operating voltages.

Fluid phase equilibria of Brazilian presalt crude oil – CO2 systems at high pressure and high temperature

This paper aims to conduct an experimental investigation of the fluid phase behavior of a highly opaque Brazilian pre-salt crude oil-CO2 system, specifically focusing on the occurrence of highly dispersed liquid-liquid transitions. The study involves examining the phase behavior of five global mole compositions [zCO2= (37.9, 50.0, 76.6, 80.6, and 84.2) mol%] by using conventional PVT techniques as light scattering, pressure-volume curve, and direct fluid observation through sapphire windows. When other techniques were ineffective, a high-pressure microscope coupled with a short-wave infrared apparatus (SWIR camera and light source) was used for complex fluid inspection.

Elevating performance of AlOxFy anti-reflection coating via controllable HF vapor fluorination

The introduction of anti-reflective coatings (ARCs) to optical devices has provided a simple and effective solution to improve their power efficiency. Among the various methods of preparing ARCs, the solution process is widely applied due to its simplicity, scalability, and naturally formable pores embedded in the film, which effectively reduce the refractive index of the material. Additionally, since low refractive index materials are always preferred for an effective ARC, strategies of fluorine substitution have been considered. Herein, we successfully introduce fluorine into Al2O3 ARCs by controlled HF vapor through abundant pores in the film. The exposure and reaction conditions were finely tunable, resulting in a precisely controlled amount of fluorine in the AlOxFy ARC. Finally, the gaseous HF vapor fluorination resulted in an effective porous ARC on a sapphire window by matching the refractive index between the surrounding media; thus, fluorinated ARC improves transparency. The maximum and the average transmittances of the ARC-applied window reach ∼99.15% and ∼97.04%, respectively. The suggested fluorination method is anticipated to have broad applicability for situations where surface chemistry modification is necessary. Highly reliable and controllable, this strategy can be used with complicated architectures without causing structural damage.

Phase behavior of carbon dioxide + 2,4-dimethylpentane binary system at high pressures

The phase behavior of the branched alkane 2,4-dimethyl pentane (2,4-DMP) and carbon dioxide (CO2) binary mixture that has no published data, to the best of our knowledge, was studied. The liquid–vapor critical line was determined up to 121.4 bar and 422.35 K, as well as vapor–liquid equilibrium (VLE) data at different constant temperatures (323.15, 343.15, 363.15, and 383.15) K and pressures between (10.4 and 120.4) bar. Phase behavior investigation was carried out in a high-pressures (HP) cell fitted with a pair of sapphire windows, one acting as a piston, hence volume up to 60 cm3, utilizing a static-analytical approach with phases sampling by the so called ROLSI valves (rapid online sample injectors) connected to a gas chromatograph (GC) for composition determination. The isothermal and critical data points for the carbon dioxide + 2,4-dimethylpentane binary mixture were modeled with the cubic equations of state (EoSs), i.e., Soave–Redlich–Kwong (SRK), Peng–Robinson (PR), and General Equation of State (GEOS), in combination with van der Waals mixing rules (one- and two-parameter conventional mixing rules, 1PCMR and 2PCMR). The calculations demonstrated that the selected models are capable of correctly reproducing the phase behavior of the mixture under study.

MP35-08 HEAD-TO-HEAD ENERGY TRANSMISSION OF THE SUPER-PULSE THULIUM FIBER LASER VERSUS HOLMIUM LASER IN MULTIPLE FIBER SIZES AND SETTINGS

You have accessJournal of UrologyCME1 Apr 2023MP35-08 HEAD-TO-HEAD ENERGY TRANSMISSION OF THE SUPER-PULSE THULIUM FIBER LASER VERSUS HOLMIUM LASER IN MULTIPLE FIBER SIZES AND SETTINGS Kalon Morgan, Nitesh Katta, Andrew S. Afyouni, Allen Rojhani, Sina S. Zarandi, Kelvin Vo, Rohit Bhatt, Andrei D. Cumpanas, Sohrab N. Ali, Pengbo Jiang, Gagik Akopyan, Roshan M. Patel, Thomas Milner, Jaime Landman, and Ralph V. Clayman Kalon MorganKalon Morgan More articles by this author , Nitesh KattaNitesh Katta More articles by this author , Andrew S. AfyouniAndrew S. Afyouni More articles by this author , Allen RojhaniAllen Rojhani More articles by this author , Sina S. ZarandiSina S. Zarandi More articles by this author , Kelvin VoKelvin Vo More articles by this author , Rohit BhattRohit Bhatt More articles by this author , Andrei D. CumpanasAndrei D. Cumpanas More articles by this author , Sohrab N. AliSohrab N. Ali More articles by this author , Pengbo JiangPengbo Jiang More articles by this author , Gagik AkopyanGagik Akopyan More articles by this author , Roshan M. PatelRoshan M. Patel More articles by this author , Thomas MilnerThomas Milner More articles by this author , Jaime LandmanJaime Landman More articles by this author , and Ralph V. ClaymanRalph V. Clayman More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000003269.08AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: To date, the standard for laser lithotripsy has been the Holmium (Ho:YAG) laser; recently a second laser for lithotripsy, the Super-Pulse Thulium fiber laser (sTFL), has become available. To better understand the capabilities of these two competing lasers relating to lithotripsy procedures, we compared the percent energy transmission (PET) of the sTFL and Ho:YAG lasers when aimed at an energy meter, using an array of fiber diameters, energy settings, and target distances. METHODS: We compared the PET and pressure produced by the sTFL and Ho:YAG lasers at three settings (popcorn (0.5 J and 40 Hz), dusting (0.3 J and 60 Hz) and fragmentation (1.0 J and 10 Hz)), four fiber sizes (272 µm, 365 µm, 550 µm, and 940 µm), and two distances (1 mm and 2 mm). PET was calculated by normalizing the energy reading when the fiber was fired with and without an interposed sapphire window in a water tank; pressure was recorded with a pressure sensing probe placed in the water tank (Figure 1). The average PET for each condition was compared using a 2-tailed, unpaired t-test. RESULTS: At the 1 mm distance, the sTFL had a greater PET than Ho:YAG for popcorn with 550 µm and 940 µm fiber sizes (p-values <0.01), for dusting with 365 µm, 550 µm, and 940 µm (p-values <0.01), and for fragmentation with 940 µm (p-values <0.01). At 1mm, the Ho:YAG had a greater PET than the sTFL for popcorn with 272 µm (p-value <0.01), and for fragmentation with 272 µm, 365 µm, and 940 µm (p-values <0.01). At 2 mm, the sTFL had a greater PET for every fiber size at all three energy settings. In all tests, the sTFL yielded lower pressure spikes (Table 1). CONCLUSIONS: At 1 mm, sTFL transmits more energy through the 940 µm fiber in all three settings: popcorn, dusting, and fragmentation, and Ho:YAG transmits more energy through the 272 µm fiber in the popcorn and fragmentation settings. At 2 mm, the sTFL has greater energy transmission in all conditions evaluated. The sTFL also resulted in lower pressure spikes than the Ho:YAG across all fiber sizes and laser settings. Source of Funding: None © 2023 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 209Issue Supplement 4April 2023Page: e471 Advertisement Copyright & Permissions© 2023 by American Urological Association Education and Research, Inc.MetricsAuthor Information Kalon Morgan More articles by this author Nitesh Katta More articles by this author Andrew S. Afyouni More articles by this author Allen Rojhani More articles by this author Sina S. Zarandi More articles by this author Kelvin Vo More articles by this author Rohit Bhatt More articles by this author Andrei D. Cumpanas More articles by this author Sohrab N. Ali More articles by this author Pengbo Jiang More articles by this author Gagik Akopyan More articles by this author Roshan M. Patel More articles by this author Thomas Milner More articles by this author Jaime Landman More articles by this author Ralph V. Clayman More articles by this author Expand All Advertisement PDF downloadLoading ...

Design of a Device and System to Study the Liquid–Solid-Phase Equilibrium Experiment of CO2 in PLNG

Pressurized liquefied natural gas (PLNG) is a new natural gas liquefaction solution proposed in recent years for reducing the construction and operating costs of floating liquefied natural gas (FLNG). For natural gas, the liquefaction temperature is strongly influenced by the pressure; when the pressure increases, the liquefaction temperature of natural gas increases accordingly. The increase in the liquefaction temperature of natural gas leads to a higher solubility of impurities such as carbon dioxide, which means that the pretreatment standards for liquefied natural gas can be reduced. Therefore, the use of PLNG technology can simplify pretreatment plants and significantly reduce construction and operating costs. In order to better apply PLNG technology to FLNG, it is necessary to understand the solubility of carbon dioxide in pressurized LNG and the phase change during liquefaction. To achieve this, experimental setups are needed to simulate the temperature and pressure environment of the LNG to obtain the relevant data and observe the relevant phenomena. After a literature research and analysis of the advantages and disadvantages of previous experimental setups, several improvements are proposed in this paper, and based on this, a visualization device is designed for studying the liquid–solid-phase equilibrium experiment of CO2 in PLNG. The device has a pressure resistance of 20 MPa, a minimum operating temperature of 77 K, and a variable volume function. It is also equipped with a sapphire window to be able to observe the inside of the device. In order to verify the superiority of the device, experiments were conducted using the device to verify the pressure resistance, variable volume, and visualization functions of the device. The experimental results show that the experimental device designed in this paper does have a certain superiority.

Measurements and model of UV-induced oxidation of aluminum

We present measurements and a model of aluminum oxidation induced by ultraviolet (UV) radiation. Spots of oxide were grown by focusing synchrotron radiation onto a polycrystalline aluminum membrane in the presence of water vapor at pressures from 3 × 10−8 to 1 × 10−4 mbar (3 × 10−6 to 1 × 10−2 Pa). The UV radiation passed through a sapphire (Al2O3) window, which ensured that the UV interacted with only the aluminum metal and not the oxide overlayer. The oxide profile of each spot was then determined by measuring the membrane's transmission at a wavelength of 17.5 nm. The model combined descriptions of photoemission from the Al metal, electron-phonon scattering in the oxide, Al3+ ion transport in the oxide, and the adsorption and ionization of H2O on the oxide surface. It also accounted for UV-induced desorption of H2O and the effect of the Al3+ ion flux on the surface reactions. The model's five free parameters were fit to the laboratory measurements of UV-induced oxidation. Then, using those values, the model was used to describe and understand the oxidation of similar aluminum membranes that were used to filter extreme ultraviolet on the Solar Dynamics Observatory, a sun-observing satellite. This understanding will help prevent similar problems on future satellites. These results are the first experimental confirmation of a model of UV-induced oxidation.

Analysis of Mars 2020 Entry Vehicle Aerothermal Flight Data

The Mars 2020 entry vehicle’s thermal protection system included measurements of in-depth temperature on the heatshield and backshell, and surface heating on the backshell. This paper describes the flight data and resulting analysis: subsurface temperatures at 11 heatshield and 6 backshell locations, measured total heat flux at two backshell locations, and a radiometer on the backshell to measure shock layer radiation. All temperatures were within allowable material limits. Total surface heat flux was derived from the in-depth temperature measurements at the thermocouple locations. Turbulent boundary-layer conditions occurred at nine heatshield locations and the radiometer provided evidence that heating from shock layer radiation significantly exceeded convective heating on the backshell. Computational results on the reconstructed entry trajectory are compared to the flight data. After boundary-layer transition, total heat flux from algebraic turbulence model calculations qualitatively matches the reconstructed heating, but with lower peak magnitudes. On the backshell, laminar heat flux predictions generally exceed the as-flown values by less than , with shock layer radiation predicted to contribute the majority of heating. At the radiometer location, the maximum predicted radiative heat flux exceeds the measurement, with the measured value likely suppressed by ablation products on the sapphire window.

The wide-angle infrared diagnostic for the first wall monitoring of the WEST tokamak

A tangential infrared thermography system is installed in the WEST tokamak to observe the thermal scene of the first wall and the divertor components through a wide-angle tangential view. The goal is to provide and monitor the heat load deposition on the plasma facing components. About one-sixth of the chamber is observed, including sectors of the baffle, the lower and upper divertors, one inner bumper, vertical displacement event (VDE) protections, one ICRH antenna, and other parts of the wall. It is used for real time machine protection by monitoring temperature thresholds in delimited region of interest, and for analysis of normal or specific heat load events during operation such as VDE, ELM, disruption or runaways. This wide-angle view uses one aspherical and one on-axis plane mirrors, a sapphire window and three lenses for the objective of the camera. The optical line is optimized for two wavelengths 1.7 and 4 µm. The field of view is 60° on a 512×640 pixels Focal Plane Array. The endoscope is fully actively cooled. The thermal scene is complex to interpret given the fully metallic and radiative environment and the uncertainties on the emissivity which is angular-dependent and changes with the surface properties. This involves significant inaccuracy on the recovery of the real temperature. In this context, an interpretation by modeling approach is better suited, based on ray-tracing simulations taking into account the optical properties of materials. For instance, this allowed discriminating reflections patterns from real thermal events in the wide-angle view. A description of the wide-angle infrared diagnostic and its performances is presented as well as experimental measurements obtained in the WEST Tokamak.

Kinetics of Polymer Network Formation by Nitroxide-Mediated Radical Copolymerization of Styrene/Divinylbenzene in Supercritical Carbon Dioxide

The kinetics of nitroxide-mediated dispersion copolymerization with crosslinking of styrene (STY) and divinylbenzene (DVB) in supercritical carbon dioxide (scCO2) is addressed experimentally. 2,2,6,6-Tetramethylpiperidinyl-1-oxy (TEMPO) and dibenzoyl peroxide (BPO) were used as nitroxide controller and initiator, respectively. A high-pressure cell with lateral sapphire windows at 120 °C and 207 bar was used to carry out the polymerizations. The nitroxide-mediated homopolymerization (NMP) of STY, as well as the conventional radical copolymerization (FRC) of STY/DVB, at the same conditions were also carried out as reference and for comparison purposes. The effect of nitroxide content on polymerization rate, evolution of molecular weight averages, gel fraction, and swelling index was studied.

Temporal characterization of broadband femtosecond laser pulses by surface third-harmonic dispersion scan with ptychographic retrieval.

We present a new, to the best of our knowledge, variant of dispersion scan (d-scan) based on surface third-harmonic generation (STHG) and a ptychographic algorithm tailored for full retrieval (amplitude and phase) of broadband laser pulses. We demonstrate the technique by temporally measuring and compressing few-cycle pulses with 7 fs and 2.5 nJ from a Ti:sapphire oscillator, using a sapphire window as the nonlinear medium. The results are in very good agreement with standard second-harmonic d-scan measurements based on a nonlinear crystal. The intrinsically broadband and phase-matching-independent nature of STHG make this technique very suitable for the characterization of ultrashort laser pulses over a broad wavelength range extending into the mid-infrared.