Quartz Window Research Articles

Numerical analysis of the thermal and mechanical effects of laser windows of a high-power all-solid-state 2-μm laser system

The output window of a high-power laser system is vulnerable to damage, and this is the main limiting factor on the power scaling and structure integrity of the laser system. In endeavoring to obtain higher output powers from the laser system, the impact of the thermal and mechanical effects and the damage mechanism of the output window must be considered. In order to study these issues, a thermal model of the laser window is established based on the heat transfer and thermoelastic theories, and the expressions for the transient thermal and mechanical stress distributions of the output window are deduced in terms of the integral-transform method. Taking the infrared quartz window material as an example, the temperature and mechanical field distributions of a high-power all-solid-state 2-μm laser system window are simulated, and the laser-induced damage mechanism is deeply analyzed. The calculation results show that the laser window-induced damage is mainly caused by melting damage when the temperature exceeds the melting point of the material. The presented theoretical analysis and numerical simulation results are significant for the design and optimization of high-power laser windows. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this

Corrigendum to “Integrated miniature fluorescent probe to leverage the sensing potential of ZnO quantum dots for the detection of copper (II) ions” [Talanta 116 (2013) 514–519

Quantum dots are fluorescent semiconductor nanoparticles that can be utilised for sensing applications. This paper evaluates the ability to leverage their analytical potential using an integrated fluorescent sensing probe that is portable, cost effective and simple to handle. ZnO quantum dots were prepared using the simple sol-gel hydrolysis method at ambient conditions and found to be significantly and specifically quenched by copper (II) ions. This ZnO quantum dots system has been incorporated into an in-house developed miniature fluorescent probe for the detection of copper (II) ions in aqueous medium. The probe was developed using a low power handheld black light as excitation source and three photo-detectors as sensor. The sensing chamber placed between the light source and detectors was made of 4-sided clear quartz windows. The chamber was housed within a dark compartment to avoid stray light interference. The probe was operated using a microcontroller (Arduino Uno Revision 3) that has been programmed with the analytical response and the working algorithm of the electronics. The probe was sourced with a 12V rechargeable battery pack and the analytical readouts were given directly using a LCD display panel. Analytical optimisations of the ZnO quantum dots system and the probe have been performed and further described. The probe was found to have a linear response range up to 0.45mM (R(2)=0.9930) towards copper (II) ion with a limit of detection of 7.68×10(-7)M. The probe has high repeatable and reliable performance.

Heat Transfer Modeling and Analysis of Solar Thermo-chemical Reactor for Hydrogen Production from Water

A solar thermo-chemical reactor is modeled and analyzed for the solar thermal dissociation of zinc oxide into zinc and oxygen involved in the thermo-chemical cycle for hydrogen production. The reactor consists of a cavity surrounded by a rotating insulation layer made of alumina. The granular zinc oxide particles are fed into the cavity and are directly exposed to the solar radiation entering the cavity through a quartz window. A three dimensional numerical model coupling the multiphase particle dynamics in gravitational field, multiphase heat transfer, k-ɛ turbulence model, discrete ordinates radiation model, Arrhenius reaction rate model is developed. The cavity temperature and oxygen molar flow rate at the outlet of the reactor which is the indicator of the reaction rate has been validated with a 10kW reactor prototype. An energy balance study of thermal performance parameters including the various losses occurring from the reactor and efficiency is also done. The major losses were contributed by re-radiation (46%) and sensible heating of reactor components (35.5%), while the minor losses were contributed by convection by argon (1%) and conduction through insulation (2%).The thermal efficiency of the reactor is calculated to be 15.5%.

Nonthermal Inactivation of Soy (Glycine Max Sp.) Lipoxygenase by Pulsed Ultraviolet Light

This study investigated pulsed ultraviolet (PUV) illumination at different distances from the PUV source on soybean lipoxygenase (LOX) (0.4 mg/mL in 0.01 M Tris-HCl buffer, pH 9) activity. Samples (5 mL) were illuminated for 1, 2, 4, 8, and 16 s at 3 distances 6, 8.5, and 11 cm from the PUV lamp's quartz window. The temperature of 33.5 ± 1.8°C was observed for the highest treatment time of 16 s at the shortest distance of 6 cm, and resulted in a 3.5 log reduction (99.95%) in initial LOX activity. Illumination time and distance from the lamp significantly (P ≤ 0.05) affected LOX inactivation. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) was performed on treated LOX samples and further protein profile for treated LOX filtrate (≤10 kDa), was analyzed by reverse phase high-performance liquid chromatography (RP-HPLC). The protein profile analysis revealed that LOX protein degradation was influenced significantly (P ≤ 0.05) by PUV illumination time.

High-temperature Fluidized Receiver for Concentrated Solar Radiation by a Beam-down Reflector System

This study proposes a novel fluidized receiver for absorbing concentrated solar light at high temperatures. Previously, a tubular receiver and a volumetric receiver were developed to make high-temperature air for a solar gas turbine system. The aim was to combine these elements with a tower reflector; however, it was challenging to install these heavy receivers on the top of the tower. Currently, a fluidized receiver prototype is tested by a 3 kWh solar simulator in preparation for a field test at the Miyazaki beam-down reflector system. The fluid dynamics of the prototype receiver is numerically investigated. The currently treated receiver is an inner-circulating fluidized bed spouted by concentric gas streams with high and low velocities in the center and outer annulus, respectively. The draft tube is submerged in the particles to organize particle circulation. Concentrated light irradiates the particles through a quartz window at the top of the receiver container. Such a fluidized bed was first adopted by Kodama et al. for thermochemical reactions; however, it is currently pursued for its potential as a high-temperature receiver aimed at concentrated solar power generation. Experiments of the prototype receiver (inner diameter = 45mm) demonstrated that the inner particles are heated to a temperature greater than 900°C and that an increase of the central gas velocity removes the excess temperature near the particle bed surface. A numerical computation suggests that the large-scale circulation of particles leads to the activation of thermal mixing. The currently proposed receiver is thus expected to attenuate re-radiation losses likely to occur in a conventional volumetric porous receiver. The scale-up of the receiver is being considered by the numerical computation for a field test in the Miyazaki 100 kWh beam-down reflector system.

Structural transformation of liquid water under shock compression condition

Using shock wave loading and real time optical transmission measurements, the transmission spectra of liquid water compressed between the quartz windows under pressures in a range of 1-1.6 GPa are obtained. A discontinuity of liquid water at nearly 0.9 GPa during the shock is observed. Combining the phase diagram of water with calculation results, it is suggested that the discontinuity of liquid water is due to a possible phase transition from low density water to high density water under the experimental conditions. The method can also be used to study other transparent molecular liquids in shock compression experiments.

Design Space Exploration of a 5 MWth Small Particle Solar Receiver

We present a design space exploration of a 5 MWth Small Particle Solar Receiver for solar tower power plants. This new solar receiver, developed under the support of the U.S. Department of Energy's SunShot Program, aims to volumetrically absorb concentrated solar irradiation using an air-particle mixture to drive a gas turbine or a combined cycle at much higher temperature than the state-of-the-art molten salt receivers. Among other advantages, the thermodynamic efficiency of the power block and the overall efficiency of the plant would considerably increase with this technology. The design space consists of the wall angle of the receiver, the geometry of the window (necessary to allow the solar irradiation to enter into the receiver) and the radiative properties of the walls. The constraints are based on material limits, ensuring the mechanical integrity of the quartz window, and other technical issues; though some of them are imposed via a penalty method. The design space is explored through parametric studies and a multidisciplinary approach is adopted. The aluminum oxide walls, the 45° spherical-cap window and the 45° wall- angle receiver are preferred due to their best compromise between thermal efficiency and wall temperature.

Optimization of Solar Tower Hybrid Pressurized Air Receiver Using CFD and Mathematical Optimization

Solar receivers used for central tower Concentrated Solar Plants (CSPs) use either a surface-based or volumetric heat transfer region. Volumetric receivers are more efficient but require more sophisticated and expensive materials that can withstand the elevated temperatures (in excess of 1000°C). If pressurized air is used as heat transfer fluid (HTF) in order to increase both the density and heat capacity of the HTF, the volumetric receiver needs to be located in a pressure vessel with a pressurized quartz window located at the aperture of the concentrator. An alternative approach to utilize pressurized air in a pseudo-volumetric fashion is to populate a volumetric region with piped pressurized air (Kretzschmar & Gauché, 2012). This tubular-type volumetric receiver provides the challenge of enabling maximum heat transfer without causing hot spots on the side of the solar irradiation source. Heat transfer would not be as effective as for a true volumetric receiver because the heat transfer area is limited by the tube wall. A Computational Fluid Dynamics (CFD) model is generated of the solar receiver cavity. The commercial CFD code ANSYS Fluent v14.5 is used to evaluate the heat transfer between the incoming solar flux and the HTF. The incoming solar irradiation is modeled using the Discrete Ordinates (DO) radiation model ANSYS Fluent. The DO model also predicts the resulting thermal radiation in the conjugate heat transfer problem. The geometry is parameterized in order to allow for the selection of design variables in a formal design optimization formulation. Results include typical CFD results of a candidate geometry to illustrate the solar irradiation input, the effect of tubular layout as well as temperature and heat flux distributions that provide candidate objective functions for optimization. Recommendations are made for the implementation of the optimization process.

Improvement of multilayer graphene synthesis on copper substrate by microwave plasma process using helium at low temperatures

A pretreatment method for copper foil substrates for graphene synthesis with microwave plasma has been developed using a helium and hydrogen gas mixture. Contaminants on the surface of the substrate, particularly copper oxides, were effectively removed by this method, which was confirmed by X-ray photoelectron spectroscopy (XPS). Graphene was grown by microwave-plasma-assisted chemical vapor deposition (MWCVD) subsequent to the pretreatment of the substrate in the same apparatus. Using the hydrogen and helium gas mixtures as the diluent gas for methane, the contamination in the deposited graphene by undesirable impurities from the ambient in the reaction apparatus, particularly silicon etched from the quartz window by microwave plasma, was successfully suppressed. The multilayer graphene films synthesized at low temperatures on the pretreated copper foil substrates exhibited higher crystallinity, as shown in transmission electron microscopy (TEM) images and Raman scattering spectra, than those on the untreated substrates.

Numerical simulation and experimental validation of a solar metal oxide reduction system under vacuum

A metal oxide reduction solar reactor is developed to operate in vacuum. Thermal and structural analyses of the system supported the design. Two calculation packages were used for the thermal analysis and another one was applied for stress analysis of the quartz window. Experiment in an empty, inert system was carried during the initial testing steps and used for the simulations validation. The models predictive capabilities were established, and can be now safely used in further improving and extending the design.

Dynamic Modeling of a Solar Reactor for Zinc Oxide Thermal Dissociation and Experimental Validation Using IR Thermography

A dynamic numerical model of a solar cavity-type reactor for the thermal dissociation of ZnO is formulated based on a detailed radiative heat transfer analysis combining the Monte Carlo ray-tracing technique and the radiosity enclosure theory. The quartz window is treated as a semitransparent glass layer with spectrally and directionally dependent optical properties. Model validation is accomplished by comparison with experimental results obtained with a 10-kW solar reactor prototype in terms of cavity temperatures, reaction extents, and quartz window temperature distribution measured by IR thermography. The solar-to-fuel energy conversion efficiencies obtained experimentally are reported, and the various energy flows are quantified.

Ultra-fast intensified frame images from an electron cyclotron resonance hydrogen plasma at 2.45 GHz: Some space distributions of visible and monochromatic emissions

First results from an ultra-fast frame image acquisition diagnostic coupled to a 2.45 GHz microwave hydrogen discharge are presented. The plasma reactor has been modified to include a transparent doubled shielded quartz window allowing to viewing the full plasma volume. Pictures describing the breakdown process at 1 μs exposure time have been obtained for integrated visible light signal, Balmer-alpha, Balmer-beta lines, and Fulcher-band. Several different plasma emission distributions are reported. The distribution depends on the magnetic field configuration, incident microwave power, and neutral gas pressure.

Growth and testing of vertical external cavity surface emitting lasers (VECSELs) for intracavity cooling of Yb:YLF

Optically-pumped vertical external cavity surface emitting lasers (VECSELs) have unique characteristics that make them attractive for use in intracavity optical cooling of rare earth doped crystals. We present the development of high power VECSELs at 1020nm for cooling ytterbium-doped yttrium lithium fluoride (Yb:YLF). The VECSEL structures use AlAs/GaAs distributed Bragg reflectors and InGaAs/GaAsP resonant periodic gain epitaxially grown by metal-organic vapor phase epitaxy. To achieve the necessary output power, we investigated thinning the substrate to improve the thermal characteristics. We demonstrated a VECSEL structure that was grown inverted, bonded to the heat sink, and the substrate removed by chemical etching. The inverted structure allows us to demonstrate 15W output with 27% slope efficiency. Wavelength tuning of 30nm around 1020nm was achieved by inserting a birefringent quartz window into the cavity. The window also narrows the VECSEL emission, going from a FWHM of 5nm to below 0.5nm at a pump power of 40W.

Integrated miniature fluorescent probe to leverage the sensing potential of ZnO quantum dots for the detection of copper (II) ions

Quantum dots are fluorescent semiconductor nanoparticles that can be utilised for sensing applications. This paper evaluates the ability to leverage their analytical potential using an integrated fluorescent sensing probe that is portable, cost effective and simple to handle. ZnO quantum dots were prepared using the simple sol–gel hydrolysis method at ambient conditions and found to be significantly and specifically quenched by copper (II) ions. This ZnO quantum dots system has been incorporated into an in-house developed miniature fluorescent probe for the detection of copper (II) ions in aqueous medium. The probe was developed using a low power handheld black light as excitation source and three photo-detectors as sensor. The sensing chamber placed between the light source and detectors was made of 4-sided clear quartz windows. The chamber was housed within a dark compartment to avoid stray light interference. The probe was operated using a microcontroller (Arduino Uno Revision 3) that has been programmed with the analytical response and the working algorithm of the electronics. The probe was sourced with a 12V rechargeable battery pack and the analytical readouts were given directly using a LCD display panel. Analytical optimisations of the ZnO quantum dots system and the probe have been performed and further described. The probe was found to have a linear response range up to 0.45mM (R2=0.9930) towards copper (II) ion with a limit of detection of 7.68×10−7M. The probe has high repeatable and reliable performance.

Researches on a new type of solar surface cladding reactor with concentration quartz window

With the aim to increase incoming solar intensity and decrease focus spot radius, a new type of solar surface cladding reactor with concentration quartz window is put forward in this paper. The comparisons of dimensionless heat flux distribution on working surface between the solar surface cladding reactor with concentration quartz window and the cladding reactor with plane quartz window are investigated by Monte Carlo ray tracing method. Besides, the impacts of refractivity and characteristic parameter of concentration quartz window on focus spot radius and peak solar intensity are also studied.

Photochemical Aging of Light-Absorbing Secondary Organic Aerosol Material

Dark reactions of methylglyoxal with NH4(+) in aqueous aerosols yield light-absorbing and surface-active products that can influence the physical properties of the particles. Little is known about how the product mixture and its optical properties will change due to photolysis as well as oxidative aging by O3 and OH in the atmosphere. Here, we report the results of kinetics and product studies of the photochemical aging of aerosols formed by atomizing aqueous solutions of methylglyoxal and ammonium sulfate. Experiments were performed using aerosol flow tube reactors coupled with an aerosol chemical ionization mass spectrometer (Aerosol-CIMS) for monitoring gas- and particle-phase compositions. Particles were also impacted onto quartz windows in order to assess changes in their UV-visible absorption upon oxidation. Photooxidation of the aerosols leads to the formation of small, volatile organic acids including formic acid, acetic acid, and glyoxylic acid. The atmospheric lifetime of these species during the daytime is predicted to be on the order of minutes, with photolysis being an important mechanism of degradation. The lifetime with respect to O3 oxidation was observed to be on the order of hours. O3 oxidation also leads to a net increase in light absorption by the particles due to the formation of additional carbonyl compounds. Our results are consistent with field observations of high brown carbon absorption in the early morning.

레이저 점화에 의한 고체추진제 Strand Burner 실험

Basically, in order to apply solid propellant as ignition source to high energy metal particle combustion system, we analyzed combustion characteristics of the HTPB/AP/Al, HTPE/AP/Al propellants by using a strand burner. The propellants were tested in a high-pressure windowed strand burner, which was pressurized up to 300 psia with pure argon gas. Strand burner was visualized with two quartz windows and ignition was accomplished by a 10 W laser. The burning rate of propellant was measured with high-speed camera method for frame analysis and photodiode method for combustion time analysis. Emission spectrum was measured with spectrometer at 300 nm ~ 800 nm and 1500 nm ~ 5000 nm and then we analyzed species during propellant combustion.

Rapid Production of Ultralow Dielectric Constant Porous Polyimide Films via CO2-tert-Amine Zwitterion-Induced Phase Separation and Subsequent Photopolymerization

Porous polymeric films are promising materials for the production of ultralow-dielectric constant materials. A high porosity polyimide thin film was prepared via the phase separation of a polyimide precursor in an N,N-dimethylacetamide (solvent)/2-(diethylamino)ethyl methacrylate/photoinitiator system. A novel technique involving high-pressure CO2 (5 MPa) gas injection was used to form CO2-2-(diethylamino)ethyl methacrylate zwitterion salt and induce the immediate phase separation and solvent droplet formation (within 60 s) of a wet precursor film on a metal substrate. The film was exposed to UV light through quartz windows for 30 s to polymerize the 2-(diethylamino)ethyl methacrylate while maintaining a constant CO2 pressure. The cured thin film containing numerous pores with an average diameter of approximately 1 μm ± 1.0 μm was treated at 320 °C for 1 h under a continuous flow of nitrogen. The obtained film was 30 μm thick and exhibited pores with an average diameter of approximately 1 μm ± 0.9 μm. The...

Chromium oxide loaded silica aerogels: Novel visible light photocatalytic materials for environmental remediation

Abstract Various photocatalytic systems have been reported for degradation of harmful air pollutants. Most of the reported catalysts are based on well-known semiconducting material, titanium dioxide (TiO 2 ), while some are based on other materials such as silicon dioxide (SiO 2 ), various zeolites. However, titania based systems are very popular in this regard and the most of the photocatalytic processes that involve titania are considered non-localized. Thus, to study the photocatalytic ability of a localized system, novel aerogel based samples were studied using silica and chromium and tested for photocatalytic activities. The new photocatalytic systems were prepared to obtain aerogel silica as the matrix material by co-hydrolyzing silica precursor with chromium(III) ions to obtain chromium loaded silica materials. Later, these prepared samples were compared to chromium loaded titania and mixed TiO 2 –SiO 2 systems. All the prepared systems have high surface areas compared to the systems that have been reported in literature. Samples were characterized by X-ray diffraction, diffusive reflectance UV spectroscopy, and BET surface analysis methods. The kinetics of photocatalytic degradation of a model pollutant, acetaldehyde, was performed using a Shimadzu GCMS-QP 5000 instrument and a glass reactor with a quartz window. Change in photocatalytic activity was found with various molar ratios of SiO 2 to TiO 2 . From all the systems, chromium loaded pure SiO 2 showed the highest activity towards acetaldehyde degradation compared to mixed TiO 2 –SiO 2 systems and TiO 2 based systems. The interesting photocatalytic activity of silica based materials occurs due to the efficient insertion of chromium ions into silica matrix to generate reactive sites. The photo excitation is believed to occur at molecular orbital level at localized chromium sites.

Recording Spatially Resolved Plasma Parameters in Microwave-Driven Plasmas

In an almost cubical reactor 90 l in volume which is intended to deposit organic polymers by plasma-enhanced chemical vapor deposition (PECVD), microwave power is coupled into the volume via a quartz window which extends to approximately 1/10 of the sidewall area. Since the plasma is excited locally, plasma parameters like electron temperature and plasma density are expected to exhibit a spatial variation. The compilation of these plasma quantities has been accomplished with a bendable single Langmuir probe. To isolate the tungsten wire against its grounded housing tube, it was coated with polyparylene. After having compared this construction with our Langmuir probe, which has been now in use for more than a decade, we have taken data of more than half the volume of the reactor with argon and have found a definitive radial inhomogenity for all plasma parameters. To investigate whether this conduct can be determined applying optical emission spectroscopy, we improved our spectrometer which had been used for endpoint detection purposes and plasma diagnostics in chlorine-containing ambients where we could detect also a spatial dependence. This behavior is discussed in terms of Lieberman's global model.