Independent Temperature Measurements Research Articles

Temperature-Compensated Solution Concentration Measurements Using Photonic Crystal Fiber-Tip Sensors.

We demonstrate fiber optic sensors with temperature compensation for the accurate measurement of ethanol concentration in aqueous solutions. The device consists of two photonic crystal (PhC) fiber-tip sensors: one measures the ethanol concentration via refractive index (RI) changes and the other one is isolated from the liquid for the independent measurement of temperature. The probes utilize an optimized PhC design providing a Lorentzian-like, polarization-independent response, enabling a very low imprecision (pm-level) in the wavelength determination. By combining the information from the two probes, it is possible to compensate for the effect that the temperature has on the concentration measurement, obtaining more accurate estimations of the ethanol concentration in a broad range of temperatures. We demonstrate the simultaneous and single-point measurements of temperature and ethanol concentration in water, with sensitivities of 19 pm/°C and ∼53 pm/%, in the ranges of 25 °C to 55 °C and 0 to 50% (at 25 °C), respectively. Moreover, a maximum error of 1.1% in the concentration measurement, with a standard deviation of ≤0.8%, was obtained in the entire temperature range after compensating for the effect of temperature. A limit of detection as low as 0.08% was demonstrated for the concentration measurement in temperature-stable conditions.

Independent measurement of refractive index and temperature using D-gapped dual-channel structure in a photonic crystal fiber

Independent measurement of refractive index and temperature using D-gapped dual-channel structure in a photonic crystal fiber

Health checkup test of the standard cosmological model in view of recent cosmic microwave background anisotropies experiments

We present an updated data-analysis comparison of the most recent observations of the Cosmic Microwave Background temperature anisotropies and polarization angular power spectra released by four different experiments: the Planck satellite on one side, and the Atacama Cosmology Telescope (ACTPol) and the South Pole Telescope (SPT-3G), combined with the WMAP satellite 9-years observation data in order to be "Planck-independent" on the other side. We investigate in a systematic way 8 extended cosmological models that differ from the baseline $\Lambda$CDM case by the inclusion of many different combinations of additional degrees of freedom, with the aim of finding a viable minimal extended model that can bring all the CMB experiments in agreement. Our analysis provides several hints for anomalies in the CMB angular power spectra in tension with the standard cosmological model that persist even in these multi-parameter spaces. This indicates that either significant unaccounted-for systematics in the CMB data are producing biased results or that $\Lambda$CDM is an incorrect/incomplete description of Nature. We conclude that only future independent high-precision CMB temperature and polarization measurements could provide a definitive answer.

Combined use of conventional and clumped carbonate stable isotopes to identify hydrothermal isotopic alteration in cave walls

Alteration of conventional carbonate stable isotopes (δ18O, δ13C) in cave walls has been shown to be a useful tool to identify cave formation driven by deep-seated processes, i.e., hypogene karstification. If combined with a prior information on the paleowater stable isotope composition, further insights can be obtained on the temperature and the source of the paleowater. Clumped isotope composition (Δ47) of carbonates is an independent measurement of temperature, and if combined with the conventional stable isotopes, can provide information on the paleowater stable isotope composition. On the example of Provalata Cave (N. Macedonia), we apply for the first time, both conventional and clumped stable isotope analysis, and identify two different isotope alteration trends, reflecting two distinct hydrothermal events: an older, hotter one, where isotope alteration was likely related to isotope diffusion, lowering the δ18O values of the carbonate; and a younger one, related to the cave formation by low-temperature CO2-rich thermal waters, with dissolution-reprecipitation as the alteration mechanism, causing decrease in δ18O values, and unexpected increase in δ13C values. The findings are further corroborated by additional insight from optical petrography and cathodoluminescence microscopy, as well as fluid inclusion analysis of secondary calcite crystals related to the cave forming phase.

Methodology Improvements for Three-Dimensional UAV-Based Travel-Time Acoustic Atmospheric Tomography

Abstract This paper describes a method for measuring continuous, three-dimensional temperature and wind velocity patterns in the atmospheric surface layer (ASL) using unmanned aerial vehicle–based acoustic atmospheric tomography (UBAAT). An unmanned aerial vehicle (UAV) is flown over an array of microphones on the ground. The travel time for sound rays between the UAV and each microphone is used to reconstruct 3D temperature and wind velocity fields, with the continuous motion of the UAV generating far more ray paths over much greater volumes of atmosphere than can be obtained using static speakers and microphones. Significant improvements over previous UBAAT techniques include the use of a synthetic tone rather than the natural sound generated by the UAV, use of vertical temperature and wind profiles to improve modeling of sharp changes near the ground, normalization of observations to incorporate weighted least squares techniques within Tikhonov regularization, and normalization of the model matrix to reduce bias in estimating modeling parameters when using Tikhonov regularization. This is the first case where UBAAT has been performed in three dimensions and also compared with independent temperature and wind velocity measurements. A summary of the results of simulation studies and trials results is provided, which shows that UBAAT can estimate three-dimensional temperature and wind velocity fields in the ASL with useful accuracy (approximately 1°C for temperature and 1 m s−1 for wind speed). Significance Statement This paper describes a method that is capable of providing a set of continuous 3D estimates of the temperature and wind velocity patterns in the first few hundreds of meters above the ground. It is like performing an ultrasound or MRI on the atmosphere. There is a need for good wind speed measurements to identify and examine the properties of the atmospheric surface layer (ASL). Features of interest include the nocturnal low-level jet, elevated inversions and temperature structures, wind flow over complex terrain, gravity waves, and wave propagation through a turbulent atmosphere.

Multiparameter Distributed Fiber Sensor Based on Optical Frequency-Domain Reflectometry and Bandwidth-Division Multiplexing

We demonstrate a multiparameter distributed sensing system based on optical frequency-domain reflectometry (OFDR) with a bandwidth-division multiplexing (BDM) technique. With the BDM-assisted OFDR, the sensor system can help interrogate multiple parallel sensing optical fibers by scanning the fibers within distinct spectral ranges without any cross talk. A dual-parameter distributed sensing system was set up by multiplexing two types of sensing fibers for the simultaneous independent measurement of strain and temperature. The rms deviations between the applied and measured values of the two parameters are <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$19~ {\mu } {\varepsilon } $ </tex-math></inline-formula> and 1.4 °C, respectively, for a sensing spatial resolution of 10 cm. The proposed multiparameter distributed sensor system offers inexpensive potential solution to continuously monitor various parameters and is effective for the health monitoring of complex distributed structures.

B-OTDR Solution for Independent Temperature and Strain Measurement in a Single Acquisition

Distributed optical fiber sensors using Brillouin scattering have already demonstrated their ability to measure changes in strain and temperature over long distance. However, the simultaneous sensitivity of the Brillouin scattering to these two parameters is a real disadvantage during the instrumentation and monitoring of structures, such as for civil engineering, oil industry applications (i.e. instrumentation of pipelines or wells) or electrical power cables monitoring. In this article, we present a new instrument enabling independently measurement of temperature or strain using a unique fiber in a single measurement. This method, which we will call B-OTDR DSTS for “Distributed Strain and Temperature Sensing”, is based on the measurement of frequency (as a standard BOTDR) but also intensity of Brillouin scattering. However, as the measurement of the latter requires an accurate measurement of power levels along the fiber, it is necessary to correct the losses by a Rayleigh OTDR measurement. The architecture of the BOTDR-DSTS allows simultaneous measurement of the Brillouin and Rayleigh backscatters. We will detail the validation results of this new device and show the interest of such a measurement on the instrumentation of a cable into a 2 km deep observation well.

Tilted fiber Bragg grating design for a simultaneous measurement of temperature and strain

Bragg wavelength is sensitive to both temperature and strain changes. Therefore, in sensors that are designed using a fiber Bragg grating (FBG), it is not possible to discriminate the cross-sensitivity of temperature and strain. The design of tilted fiber Bragg gratings (TFBG), which is a family of short-period gratings, has been one of the solutions to this problem. The core mode resonance (LP01) and cladding resonances (LPmn) appear simultaneously in the transmission spectrum. It is possible to perform the simultaneous, independent measurement of temperature and strain using only a TFBG. In this study, the design of a TFBG sensor with a tilt angle of 5° were performed by using the Optigrating 4.2.2 software in order to measure the temperature and strain simultaneously. While the varying temperature was applied to the TFBG in the first stage, the varying strain was applied to it in the second stage, and simultaneously varying temperature and strain were applied to it in the third stage, and linear shifts occurring in wavelengths were calculated using Optigrating. In the design stage of the temperature sensor, research was conducted with different thermal expansion and thermo-optic coefficients, the amounts of shifts caused by these coefficients in the wavelength were examined. It was observed that the change in the wavelength caused by the simultaneous application of temperature and strain was equal to the total change in wavelength that occurred in the non-simultaneous application of temperature and strain.

CURRENT STATE OF METHODS AND MEANS OF REGISTRATION OF HIGH TEMPERATURES AND MECHANICAL STRESSES IN STRUCTURES

An analytical review of physically possible methods and available achievements in registering hydrostatic pressure or mechanical stresses using fiber optic fibers and sensors based on them based on published works that can be used in harsh environmental conditions is carried out. The results of the review show that fully distributed or quasidistributed fiber-optic systems for recording hydrostatic pressure or mechanical stress can be implemented on the following physical principles and apparatus with measures to compensate or suppress the influence of temperature: polarizing sensors on birefringent single- mode light guides and OTDR equipment; micro-flexible sensors with OTDR equipment on conventional multimode fibers; measuring systems on fiber Bragg gratings; on discrete sensors, in particular, on sealed fiber Fabry–Perot interferometers; Brillouin distributed sensors on single-mode fibers that are not sensitive to temperature changes. It is shown that single-mode birefringent fibers with hollow holes in the shell and fiber Bragg gratings written in the core have a good linear sensitivity to hydrostatic pressure and a weak dependence on temperature. Lattices in phosphorous-containing single-mode light guides have increased high-temperature properties up to ~500 C and higher. A number of discrete fiber sensors’ structures and pressure recorders are investigated. Various structures of sensitive elements of pressure sensors on sealed fiber Fabry–Perot interferometers and fiber gratings in spherical and cylindrical small-sized cases are investigated. Sensors based on Fabry–Perot fiber interferometers soldered into a glass capillary and protected from water by external high-temperature hermetic coatings showed good linearity in the pressure range of 0…540 ATM at temperatures up to ~200 C. The sensors are efficient at temperatures up to 600 °C and are promising for use in severe and special external conditions. The possibility of compensating the temperature sensitivity by selecting external coatings is shown. Pressure sensors were tested on local areas with microbends and it was shown that they can measure pressures up to ~24 МPа at temperatures up to ~450 C, but to compensate for the dependence of the readings on temperature, it must be measured by an independent sensor. The possibility of independent and simultaneous measurement of hydrostatic pressure and temperature along a single fiber using spontaneous Brillouin scattering is shown. Pressure is measured by the frequency shift of Brillouin scattering, and temperature by its intensity. The operation of the Brillouin recorder in the pressure range 0…34 MРа is demonstrated. The pressure resolution was ~0,2 МРа. New methods are proposed for detecting Brillouin scattering – a heterodyne signal with a high signal-to-noise ratio and based on frequency modulation of a semiconductor single-frequency distributed feedback laser. The measurement range has been increased by more than 10 km and the coordinate resolution has been increased. The Brillouin scattering method is promising for creating distributed systems for measuring hydrostatic pressure or mechanical stress for severe physical conditions, including temperatures of ≥3000 C.

Microstructured Multilayered Surface-Acoustic-Wave Device for Multifunctional Sensing

A multifunctional sensor based on a surface-acoustic-wave (SAW) device is fabricated. It allows independent measurements of temperature and applied magnetic field. Optimization of the multilayered device structure leads to a temperature-coefficient frequency of the Love-wave resonance reduced to zero. The sensitivity to an applied magnetic field is obtained through magnetostriction of a $\mathrm{Co}$-$\mathrm{Fe}$-$\mathrm{B}$ layer. By use of shape anisotropy, the variation of intrinsic magnetic anisotropy with temperature is strongly reduced. On one hand, interrogating the device at the Love-wave-resonance frequency allows us to extract the applied magnetic field independently of the temperature in a [130--370 K] range. On the other hand, the Rayleigh or Leaky waves are less or not sensitive to applied fields but have a high temperature coefficient of frequency. So interrogating the device at the Rayleigh resonance frequency allows us to extract the temperature independently of the magnetic field. In addition, the used resonator geometry offers the possibility for future batteryless and wireless interrogation.

Coupled Stratospheric Chemistry–Meteorology Data Assimilation. Part I: Physical Background and Coupled Modeling Aspects

A coupled stratospheric chemistry–meteorology model was developed by combining the Canadian operational weather prediction model Global Environmental Multiscale (GEM) with a comprehensive stratospheric photochemistry model from the Belgian Assimilation System for Chemical ObsErvations (BASCOE). The coupled model was called GEM-BACH for GEM-Belgian Atmospheric CHemistry. The coupling was made across a chemical interface that preserves time-splitting while being modular, allowing GEM to run with or without chemistry. An evaluation of the coupling was performed by comparing the coupled model, refreshed by meteorological analyses every 6 h, against the standard offline chemical transport model (CTM) approach. Results show that the dynamical meteorological consistency between meteorological analysis times far outweighs the error created by the jump resulting from the meteorological analysis increments at regular time intervals, irrespective of whether a 3D-Var or 4D-Var meteorological analysis is used. Arguments in favor of using the same horizontal resolution for chemistry, meteorology, and meteorological and chemical analysis increments are also presented. GEM-BACH forecasts refreshed by meteorological analyses every 6 h were compared against independent measurements of temperature, long-lived species, ozone and water vapor. The comparison showed a relatively good agreement throughout the stratosphere except for an upper-level warm temperature bias and an ozone deficit of nearly 15%. In particular, the coupled model simulation during an ozone hole event gives better ozone concentrations than a 4D-Var chemical assimilation at a lower resolution.

Thin Filament Pyrometry Field Measurements in a Medium-Scale Pool Fire

This paper presents the development of a thin filament pyrometry method to characterize the time-varying temperature field in a medium-scale pool fire burning in a quiescent environment. A digital camera with optical filters and zoom lens was used to record the high temperature emission intensity of 14 μm diameter, Silicon-Carbide filaments oriented horizontally at various heights above the center of a steadily burning 0.30 m diameter methyl alcohol (methanol; CH3OH) pool fire. Experiments collected 30 Hz video of the planar filament array. In a separate experiment, a 50 μm diameter thermocouple was used to acquire independent temperature measurements in the high temperature zone of the fire. A correlation was developed between the probability density functions of the radiation-corrected thermocouple measurements and the camera grayscale pixel intensity of the filaments. This arrangement enables measurement of the time-varying temperature field over a temperature range from about 1150 K to 1900 K with a spatial resolution of 160 μm, a temporal resolution of 0.033 s, and an expanded uncertainty of about 150 K (at a mean temperature of 1300 K). Measurements of the grayscale pixel intensities of the filaments were obtained. False color maps of the temperature field were produced to characterize the high temperature field as a function of time. Using statistical analysis, the local time-averaged temperatures and their variance for each location on the filaments were determined. Time-averaged temperatures were compared favorably to previously reported measurements. The dominant frequency of the puffing fire was determined. The temperature field time series was transformed to consider its character during consecutive phases of the fire's puffing cycle. The analysis emphasizes the cyclic nature of a pool fire, providing insight on its complex dynamic structure.

A Three‐Dimensional Array for the Study of Infrasound Propagation Through the Atmospheric Boundary Layer

AbstractThe Royal Netherlands Meteorological Institute (KNMI) operates a three‐dimensional microbarometer array at the Cabauw Experimental Site for Atmospheric Research observatory. The array consists of five microbarometers on a meteorological tower up to an altitude of 200 m. Ten ground‐based microbarometers surround the tower with an array aperture of 800 m. This unique setup allows for the study of infrasound propagation in three dimensions. The added value of the vertical dimension is the sensitivity to wind and temperature in the atmospheric boundary layer over multiple altitudes. In this study, we analyze infrasound generated by an accidental chemical explosion at the Moerdijk petrochemical plant on 3 June 2014. The recordings of the tower microbarometers show two sequential arrivals, whereas the recordings on the ground show one wavefront. This arrival structure is interpreted to be the upgoing and downgoing wavefronts. The observations are compared with propagation modeling results using global‐scale and mesoscale atmospheric models. Independent temperature and wind measurements, which are available at the Cabauw Experimental Site for Atmospheric Research, are used for comparison with model output. The modeling results explain the signal arrival times; however, the tower wavefront arrivals are not explained. This study is important for understanding the influence of the atmospheric boundary layer on infrasound detections and propagation.

Experimental observation of oblique shock waves in steady non-ideal flows

Steady oblique shock waves are observed for the first time in non-ideal supersonic flows of single-phase organic vapors. A diamond-shaped airfoil with semi-aperture 7.5^{circ } at the leading edge and 10^{circ } at the trailing edge is placed within a uniform supersonic stream (Mach number M = 1.5) of siloxane fluid MDM (octamethyltrisiloxane, hbox {C}_8hbox {H}_{24}hbox {O}_2hbox {Si}_3). Oblique shock waves are observed at varying stagnation conditions in the pre-shock state, for a set of flow deviation angles obtained by changing the attitude of the model with respect to the wind tunnel axis. Stagnation temperatures and pressures reduced by critical values range from 0.928 to 0.979 and from 0.200 to 0.615, respectively. Oblique shock waves are characterized through independent measurements of pressure, temperature and Mach number. Stagnation pressure and temperature are measured in the wind-tunnel settling chamber, while the pre-shock, post-shock and post-expansion static pressures are measured at selected locations close to the airfoil. Direct measurement of the flow Mach number is provided by schlieren visualizations. Experimental results agree with the shock wave theory for two-dimensional steady flows, complemented with state-of-the-art thermodynamic models, and deviate from their well-known, dilute-gas predictions. In particular, measurements show the non-ideal dependence of the pressure ratio across the shock on stagnation conditions in addition to the well-known dependence on the pre-shock Mach number, specific heat ratio and flow deviation angle typical of dilute gas conditions.Graphical abstract

Influence of the North Atlantic Oscillation on δD and δ18O in meteoric water in the Armenian Highland

The stable hydrogen (δD) and oxygen (δ18O) isotope composition of modern meteoric water are influenced by changes in global temperature, Rayleigh distillation processes, and moisture transport history. However, on a global scale the relative influence of these different meteorological variables is spatially heterogeneous. We collected daily precipitation samples from meteorological stations in the Armenian Highlands for a period of one year in order to determine the constraints on δD and δ18O and relationship to broader climatic conditions. These data are coupled with HYSPLIT back-trajectory analysis to determine how these compositions relate to moisture source and transport path. Multivariate analysis shows the strongest relationship between δD and δ18O and climate variables is temperature at the sampling site. Along with temperature, the intensity of the North Atlantic Oscillation, a pattern of atmospheric circulation which determines the strength and location of Northern Hemisphere midlatitude westerlies, is significant (p < 0.05) for both δ18O and δD values of precipitation. This correlation between NAO and isotopes in precipitation is also observed in four nearby GNIP stations from 2008 to 2015. Negative NAO phases are associated with weakened westerlies, which allows precipitation enriched in heavy isotopes from the Mediterranean and southerly sources to penetrate into the Armenian Highlands, whereas positive NAO phases are associated with stronger westerlies bringing more negative precipitation from the Black Sea. This relationship is most significant (p < 0.001) during the winter and spring months (December to May). These data demonstrate that paleo-archives of δD and δ18O in the Armenian Highlands could serve as a tool to measure changes in the NAO in the past, particularly when coupled with independent measurements of temperature.

(Invited) Raman Thermography of β-Ga2­O3 Nanomembrane FETs on Diamond

Despite the extremely low thermal conductivity of Ga2O3, remarkable progress in device technology has been achieved in a very short time since commercial HVPE epilayers were first introduced by Novel Crystal Technology, Japan. For example, Schottky barrier diodes with a forward current of 2 A were recently demonstrated, and thicker, low-doped epi has pushed breakdown voltage beyond 2 kV [1, 2]. Recent demonstrations of Raman thermography in Ga2O3 transistors, however, have proven that a heat spreading solution must be developed in order to realize the potential of Ga2O3 for high power operation [3]. As all devices eventually become thermally limited, effective heat dissipation will also assist in improving reliability and eventual commercialization of Ga2O3 devices. A number of approaches have been devised for GaN HEMTs in the past, where heat generated by the 2DEG under high electric field near the gate can push device temperatures above GaN reliability limits [4, 5]. In this work, we show for the first time that a reasonable operating temperature can be achieved in a Ga2O3 device at a practical power density. While wafer-scale thermal management solutions for Ga2O3 are still being developed, we have exploited the natural (100) cleave plane of Ga2O3 to mechanically exfoliate a highly-doped Ga2O3 membrane onto an insulating single-crystalline CVD diamond substrate and subsequently fabricate a Ga2O3-channel FET using standard electron-beam lithography techniques. Thermal characterization in the transistor channel was performed using a Raman thermography setup by first calibrating the Raman shift of the 169 cm-1 line as a function of temperature on a thermal chuck. This phonon line was chosen as its temperature dependent shift is relatively linear [6]. Independent measurements of the Au contact temperature using thermoreflectance imaging and modeling of the device produced a good agreement with the data [7, 8]. The combination of a thin, highly Sn-doped (2.7x1018 cm-3) Ga2O3 channel, high quality ALD Al2O3 gate dielectric, high thermal conductivity diamond substrate, and a very high critical field for both the channel and substrate (8 MV/cm for Ga2O3, 10 MV/cm for diamond) allowed for a high current density to be maintained under high drain bias. As a result, a maximum DC power density of about 60 W/mm and channel temperature of about 160 °C were simultaneously obtained before destructive failure occurred in the Ga2O3 FET channel. To the authors’ best knowledge, this is the highest power density demonstrated by any semiconductor device. [1] J. Yang et al., IEEE Trans. Electr. Dev., vol. 65, no. 7, pp. 2790, 2018. [2] J. Yang et al., ECS Jour. Solid State Sci. and Technol., vol. 7, no. 5, pp. Q92-Q96, 2018. [3] J.W. Pomeroy et al., IEEE Electr. Dev. Lett., 2018. DOI: 10.1109/LED.2018.2887278. [4] M.J. Tadjer et al., IEEE Electron Dev. Lett., vol. 33, no. 1, pp. 23-25, 2012. [5] K.D. Chabak et al., IEEE Electr. Dev. Lett., vol. 31, no. 2, pp. 99-101, 2010. [6] D. Dohy, G. Lucazeau, A. Revcolevschi, J. Solid State Chem. 45, 180-192 (1982). [7] J. Noh et al., Proc. Dev. Res. Conf., 2018. DOI: 10.1109/DRC.2018.8442276. [8] J. Noh et al., “High Performance β-Ga2O3 Nano-membrane Field Effect Transistors on a High Thermal Conductivity Diamond Substrate,” IEEE Jour. Electr. Dev. Soc., under review.

Overview of the ECE measurements on EAST

Radiometer systems and a Michelson interferometer, have been operated routinely to detect the elec-tron cyclotron emission (ECE) from EAST plasmas for diagnosing the local electron temperature. A common quasi-optical antenna placed inside the vacuum vessel is employed to collect and focus the plasma emission, and the line of sight is along a radial chord. All of the systems are located in a diagnostic room where the plasma emission is transmitted by overmoded corrugated waveguide. In-situ absolute intensity calibration has been carried out for both the radiometer systems and the Michelson interferometer independently, to ensure that the ECE diagnostic provides an independent electron temperature measurement. In order to diagnose the small-amplitude electron temperature fluctuation, a correlation ECE (CECE) diagnostic has been designed and commissioned recently. The CECE diagnostic employs an independent antenna system which has improved poloidal resolution. A synthetic diagnostic is realized by using the simulation code SPECE to interpret the ECE data in plasmas with non-Maxwellian distribution, and preliminary results imply that the ECE data could be still useful as a localized measurement in plasmas with non-thermal electrons, such as the LHW-heated plasmas on EAST.

Feasibility Study for Implementing an Optical Thomson Scattering System for Studying Photoionized Plasmas on Z

Many astrophysical environments such as X-ray binaries, active galactic nuclei, and accretion disks of compact objects have photoionized plasmas. The strong photoionizing environment found near these bright X-ray sources can be produced in a scaled laboratory experiment, and direct measurements can form a testbed for spectroscopic models and photoionization codes used in analysis of these astrophysical objects. Such scaled experiments are currently being conducted using Ne filled gas cells on the Z-facility as part of the Z Astrophysical Plasma Properties (ZAPP) collaboration. The plasma is diagnosed using a pressure sensor for density and X-ray absorption spectroscopy for charge-state distribution. The electron temperature is presently inferred from a Li-like ion level population ratio, but it is necessary to obtain an independent temperature measurement, as photoionization alters the charge state distribution and can therefore cause errors in temperatures obtained via line ratio techniques. Optical Thomson scattering is a fitting diagnostic because it directly probes the distribution of plasma particle velocities with respect to a central probe frequency. It is a powerful diagnostic which can produce time and space resolved measurements of electron temperature, as well as, electron density, ion temperature, and average ionization. In this paper, we explore a possible design for an optical Thomson scattering system to supplement X-ray spectroscopic measurements. The proposed design will use equipment that is available on Z, though not yet assembled. Both the feasibility and impact of this new diagnostic are assessed by simulating expected spectra for a range of plasma parameters, thereby demonstrating the sensitivity of this diagnostic.

Hydrogen determination in welded specimens by carrier gas hot extraction—a review on the main parameters and their effects on hydrogen measurement

Carrier gas hot extraction (CGHE) is a commonly applied technique for determination of hydrogen in weld joints using a thermal conductivity detector (TCD) for hydrogen measurement. The CGHE is based on the accelerated hydrogen effusion due to thermal activation at elevated temperatures. The ISO 3690 standard suggests different specimen geometries as well as necessary minimum extraction time vs. temperature. They have the biggest influence on precise hydrogen determination. The present study summarizes the results and experience of numerous test runs with different specimen temperatures, geometries (ISO 3690 type B and small cylindrical samples), and factors that additionally influence hydrogen determination. They are namely specimen surface (polished/as-welded), limited TCD sensitivity vs. specimen volume, temperature measurement vs. effects of PI-furnace controller, as well as errors due to insufficient data assessment. Summarized, the temperature is the driving force of the CGHE. Two different methods are suggested to increase the heating rate up to the desired extraction temperature without changing the experimental equipment. Suggestions are made to improve the reliability of hydrogen determination depended on the hydrogen signal stability during extraction accompanied by evaluation of the recorded data. Generally, independent temperature measurement with dummy specimens is useful for further data analysis, especially if this data is used for calculation of trapping kinetics by thermal desorption analysis (TDA).

High-Altitude (0–100 km) Global Atmospheric Reanalysis System: Description and Application to the 2014 Austral Winter of the Deep Propagating Gravity Wave Experiment (DEEPWAVE)

AbstractA data assimilation system (DAS) is described for global atmospheric reanalysis from 0- to 100-km altitude. We apply it to the 2014 austral winter of the Deep Propagating Gravity Wave Experiment (DEEPWAVE), an international field campaign focused on gravity wave dynamics from 0 to 100 km, where an absence of reanalysis above 60 km inhibits research. Four experiments were performed from April to September 2014 and assessed for reanalysis skill above 50 km. A four-dimensional variational (4DVAR) run specified initial background error covariances statically. A hybrid-4DVAR (HYBRID) run formed background error covariances from an 80-member forecast ensemble blended with a static estimate. Each configuration was run at low and high horizontal resolution. In addition to operational observations below 50 km, each experiment assimilated 105 observations of the mesosphere and lower thermosphere (MLT) every 6 h. While all MLT reanalyses show skill relative to independent wind and temperature measurements, HYBRID outperforms 4DVAR. MLT fields at 1-h resolution (6-h analysis and 1–5-h forecasts) outperform 6-h analysis alone due to a migrating semidiurnal (SW2) tide that dominates MLT dynamics and is temporally aliased in 6-h time series. MLT reanalyses reproduce observed SW2 winds and temperatures, including phase structures and 10–15-day amplitude vacillations. The 0–100-km reanalyses reveal quasi-stationary planetary waves splitting the stratopause jet in July over New Zealand, decaying from 50 to 80 km then reintensifying above 80 km, most likely via MLT forcing due to zonal asymmetries in stratospheric gravity wave filtering.