Impurity Emission Research Articles

Methodological Design and Commissioning of an Experimental Stand for the Study of the Spread of Harmful Substances in the Air of Work Areas during the Processing of Metals in Industry

The present publication presents preliminary advances about the experimental design related with the emission of impurities in the work environment during processing of metals, so as to study the result of thermal destruction of substances used in the optimization of technological processes. These results will be the basis for the design of new experimental models based on techniques and tools of computational simulation in order to set up a mathematical model describing the spread of harmful substances into the environment during the application of lubricating cooling technical means during the cutting and processing of metals in the industry.

Fast imaging diagnostics on the C-2U advanced beam-driven field-reversed configuration device.

The C-2U device employed neutral beam injection, end-biasing, and various particle fueling techniques to sustain a Field-Reversed Configuration (FRC) plasma. As part of the diagnostic suite, two fast imaging instruments with radial and nearly axial plasma views were developed using a common camera platform. To achieve the necessary viewing geometry, imaging lenses were mounted behind re-entrant viewports attached to welded bellows. During gettering, the vacuum optics were retracted and isolated behind a gate valve permitting their removal if cleaning was necessary. The axial view incorporated a stainless-steel mirror in a protective cap assembly attached to the vacuum-side of the viewport. For each system, a custom lens-based, high-throughput optical periscope was designed to relay the plasma image about half a meter to a high-speed camera. Each instrument also contained a remote-controlled filter wheel, set between shots to isolate a particular hydrogen or impurity emission line. The design of the camera platform, imaging performance, and sample data for each view is presented.

EMC3‐EIRENE Simulation of Impurity Transport in Comparison with EUV Emission Measurements in the Stochastic Layer of LHD: Effects of Force Balance and Transport Coefficients

AbstractThe transport properties and line emissions of the intrinsic carbon in the stochastic layer of the Large Helical Device have been investigated with the three‐dimensional edge transport code EMC3‐EIRENE. The simulations of impurity transport and emissivity have been performed to study the dedicated experiment in which the carbon emission distributions are measured by a space‐resolved EUV spectrometer system. A discrepancy of the CIV impurity emission between the measurement and simulation is obtained, which is studied with the variation of the ion thermal force, friction force and the perpendicular diffusivity in the impurity transport model. An enhanced ion thermal force or a reduced friction force in the modelling can increase the CIV impurity emission at the inboard X‐point region. Furthermore, the impact of the perpendicular diffusivity Dimp is studied which shows that the CIV impurity emission pattern is very sensitive to Dimp. It is found that the simulation results with the increased Dimp tend to be closer to the experimental observation. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The emission properties of bmimBF4 determined using an HPLC system. Significant influence of emission of impurities

Abstract Determination of the real emission properties of imidazolium room temperature ionic liquids (RTILs) is highly desirable because many of their applications are based on the exact knowledge of their emission properties. Unfortunately, it has not been possible to obtain even two identical emission spectra for any of imidazolium RTILs! In this study an innovative use of a high performance liquid chromatography (HPLC) system coupled with a PDA spectrophotometer and fluorescence detector has been employed. This system allows a separation of impurities from 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF 4 ), and to a high degree, a separation of bmimBF 4 -related species, which makes it an irreplaceable setup for determining real absorption and emission properties of a compound studied. Thus, it was possible to calculate the emission quantum yield, Φ E −4 (HPLC system) which is by about ten times (!) smaller than Φ E ∼ 10 ‐2 (spectrofluorometer). It was also possible to calculate the contribution of the emission of impurities to the total emission observed, which was as high as ≥70%. This clearly shows that the influence of emission of impurities on the emission spectrum and the Φ E of bmimBF 4 is astoundingly great.

Thermal behaviour of the NaYF4:Yb3+,R3+ materials

The NaYF4:Yb3+,R3+ (R: none, Pr, Nd, Sm, Eu, Tb or Dy) materials were prepared with selected dopant concentrations, using co-precipitation synthesis, to study the effect of the dopant and its concentration on the structure of these materials. The thermal behaviour of the as-prepared materials was studied with differential scanning calorimetry (DSC) and thermogravimetry. The structures prior to and after annealing were identified with X-ray powder diffraction. The materials were mainly hexagonal with occasional slight cubic impurity. The DSC curves revealed the cubic-to-hexagonal phase transition at 400–450 °C which temperature changes irregularly with the R3+ dopant and its concentration. The specific enthalpy of this transition varies also in a complicated way but may be correlated with the completeness of the transition. The hexagonal-to-cubic transition temperature (ca. 670 °C) is rather constant regardless of the R3+ dopant or its concentration. The temperatures and specific enthalpies of the phase transitions are useful when choosing the optimum dopant concentrations. It is also possible to estimate the structure prior to annealing with significant savings in use of resources. Only with Sm3+ and Dy3+ doping, no visible up-conversion luminescence was observed—in addition to the Er3+ and Tm3+ impurity emission. Eventually, it was found that the hexagonal form gives much stronger up-conversion luminescence and changes in the rare earth concentration allows the formation of this form.

Impurity Emission Behavior in the Soft X-Ray and Extreme Ultraviolet Range on EAST**supported by National Natural Science Foundation of China (Nos. 11175208, 11275231 and 11305207), the National Magnetic Confinement Fusion Science Program of China (Nos. 2012GB101001 and 2013GB112004), Scientific Instrument Development Project of Chinese Academy of Sciences (No. YZ200922) and JSPS-NRF-NSFC A3 Foresight Program in the Field of Plasma Physics

Spectroscopy in the soft X-ray and extreme ultraviolet (XEUV) region is very important in magnetic fusion research. Recently, two flat-field spectrometers that utilize a varied line spacing grating to image the spectra of 1-13 nm and 5-50 nm were installed on EAST for core impurity emission monitoring and impurity transport study. The instruments were proven to be capable of observing spectral lines from low-Z impurities (Li, C, O, N, Ar, etc.) and highly ionized medium- and high-Z impurities (Fe, Cr, Ni, Cu, Mo, etc.). For example, spectra in the wavelength intervals of 1-2 nm and 5-13 nm contained strong metal lines, especially molybdenum lines during H-mode phases. Argon and nitrogen lines were also observed, which were injected for diagnostic purposes. Impurity lines were identified and compared to measurements on other magnetic fusion research devices. Detailed measurements of radial emission profiles from various impurity line emissions were also presented.

Ammonia borane confined by poly(methyl methacrylate)/multiwall carbon nanotube nanofiber composite, as a polymeric hydrogen storage material

In this work, poly(methyl methacrylate)/ammonia borane/multiwall carbon nanotube (PMMA/AB/MWCNT) nanofiber composites have been fabricated and the synergetic nanoconfinement effect of nanofiber and CNT components on dehydrogenation temperature and liberating unwanted byproducts of AB (NH3BH3) have been studied. The results of dehydrogenation of PMMA/AB and PMMA/AB/MWCNT samples show 112 and 85 °C exothermic reaction temperatures, which are dramatically lower than pure AB (120 °C). Furthermore, by capture and interaction of AB molecules in the MWCNT and PMMA nanofiber structures, the enthalpy of exothermic decomposition decreases from −21.00 to −1.83 kJ mol−1 H2, suggesting that this type of AB nanofiber composite can provide a convenient reversible hydrogen storage material. The utilization of MWCNT as carbon catalyst and confining of AB result in a decrease of ammonia borane weight loss from 60.00 to 2.88 wt% which in turn can vigorously decline the emission of byproduct impurities. The synthesis process of PMMA/AB/MWCNT nanofiber composites causes the crystal structure of AB particles changed to the amorphous structure which has been clearly confirmed by X-ray diffraction analyses. The strategy of combining nanofiber structure and MWCNT as carbon catalyst with AB particles can be presented as a practicable solution to reach lower operational temperature and to decline undesirable volatile products.

Analysis of impurity effects on the coloration of corundum by laser-induced breakdown spectroscopy (LIBS).

Corundum was analyzed using laser-induced breakdown spectroscopy (LIBS) for impurity effects in their multiple colorings. Qualitative measurements were attained for impurities of chromium, magnesium, iron, and titanium in red, yellow, and blue samples. Moreover, treatment with a beryllium diffusion, which can modify corundum to obtain an attractive color, was tested in the yellow sample. In this work, most of the measurements were acquired using a laser pulse energy of 5 mJ and impurity emissions were appreciable. The signal-to-noise ratios were 11, 6.5, 10, and 4 for the Cr 425.44 nm, Fe 404.58 nm, Be 313.04 nm, and Mg 285.21 nm lines, respectively, for five laser shots. The amount of damage to the corundum samples was also monitored by measuring the craters after laser analysis. It was found that the crater size was about 30 μm after 10 laser shots. As such, the damage to corundum sample is almost imperceptible after the LIBS analysis.

Evaluation of Poloidal Distribution from Edge Impurity Emissions Measured at Different Toroidal Positions in Large Helical Device

Evaluation of Poloidal Distribution from Edge Impurity Emissions Measured at Different Toroidal Positions in Large Helical Device

VUV/XUV measurements of impurity emission in plasmas with liquid lithium surfaces on LTX

The VUV/XUV spectrum has been measured on the Lithium Tokamak eXperiment (LTX) using a transmission grating imaging spectrometer (TGIS) coupled to a direct-detection x-ray charge-coupled device camera. TGIS data show significant changes in the ratios between the lithium and oxygen impurity line emission during discharges with varying lithium wall conditions. Lithium coatings that have been passivated by lengthy exposure to significant levels of impurities contribute to a large O/Li ratio measured during LTX plasma discharges. Furthermore, previous results have indicated that a passivated lithium film on the plasma facing components will function as a stronger impurity source when in the form of a hot liquid layer compared to a solid lithium layer. However, recent TGIS measurements of plasma discharges in LTX with hot stainless steel boundary shells and a fresh liquid lithium coating show lower O/Li impurity line ratios when compared to discharges with a solid lithium film on cool shells. These new measurements help elucidate the somewhat contradictory results of the effects of solid and liquid lithium on plasma confinement observed in previous experiments.

Luminescence properties of solid solutions of borates doped with rare-earth ions

The structural and luminescence properties of Lu x Y1 − x BO3 solid solutions doped with Ce3+ or Eu+3 have been investigated. It has been found that the solid solutions crystallize in the vaterite phase with a lutetium concentration x < 0.5. For a higher lutetium concentration x, the solid solutions contain an additional calcite phase with a content less than 5 wt %. The luminescence spectra are characterized by intensive impurity emission under excitation with the synchrotron radiation in the X-ray and ultraviolet spectral ranges. It has been shown that, as the lutetium concentration x in the Lu x Y1 − x BO3: Ce3+ solid solutions increases, the emission intensity smoothly decreases, which is associated with a gradual shift of the Ce3+ 5d(1) level toward the bottom of the conduction band, as well as with a decrease in the band gap. It has been established that, in the Lu x Y1 − x BO3: Eu3+ solid solutions with intermediate concentrations x, the efficiency of energy transfer to luminescence centers increases. This effect is explained by the limited spatial separation of electrons and holes in the solid solutions. It has been demonstrated that the calcite phase adversely affects the luminescence properties of the solid solutions.

Electrospun PMMA/AB nanofiber composites for hydrogen storage applications

AbstractIn this work, poly(methyl methacrylate) (PMMA)/ammonia borane (AB) nanofiber composites were fabricated and the synergetic nanoconfinement effect of nanofibers on dehydrogenation temperature and the removal of unwanted by-products of AB (NH3 BH3) were studied. The results of the dehydrogenation of PMMA/AB samples showed an exothermic reaction temperature of 112°C, which is significantly lower than that of pure AB (120°C). Furthermore, the interaction between AB molecules and PMMA nanofiber structures decreased the enthalpy of exothermic decomposition, from -21.00 to -10.66 kJ/mol H2, suggesting that this type of AB nanofiber composite can provide a convenient reversible hydrogen storage material. Based on the thermogravimetric analysis curves, the use of PMMA to support AB in composite structures resulted in a decrease in AB weight loss from 60.00 to 11.10 wt.% which, in turn, could vigorously reduce the emission of by-product impurities. Based on the obtained results, the strategy of supporting AB in nanofiber structures can be presented as a practical solution to maintain lower operational temperatures and to reduce undesirable volatile products in the dehydrogenation process of AB.

First measurements of highly ionized impurity emission distribution by grazing-incidence flat-field extreme ultraviolet spectrometer in HL-2A.

A space-resolved grazing-incidence flat-field extreme ultraviolet (EUV) spectrometer has been developed in the HL-2A tokamak to measure vertical impurity emission profiles with simultaneous spectral, temporal, and spatial resolution. The spectrometer working in the wavelength range of 30-500 Å has been equipped with a gold-coated varied-line-spacing holographic grating with curvature of 5606 mm and a back illuminated charge-coupled device with size of 6.6 × 26.6 mm(2) (255 × 1024 pixels). A lower half of the HL-2A plasma with averaged minor radius of 40 cm is observed when the spectrometer with horizontal dispersion is placed at a distance of 7.5 m away from the plasma center. An excellent spatial resolution of 12 mm is achieved when a space-resolved slit with vertical width of 0.5 mm is adopted. The radial profiles of intrinsic impurities in several ionization stages have been measured with high throughput and extremely low stray light.

Near-infrared spectroscopy for divertor plasma diagnosis and control in DIII-D tokamak.

New near infrared (NIR) spectroscopic measurements performed in the DIII-D tokamak divertor plasma suggest new viable diagnostic applications: divertor recycling and low-Z impurity flux measurements, a spectral survey for divertor Thomson scattering (DTS) diagnostic, and Te monitoring for divertor detachment control. A commercial 0.3 m spectrometer coupled to an imaging lens via optical fiber and a InGaAs 1024 pixel array detector enabled deuterium and impurity emission measurements in the range 800-2300 nm. The first full NIR survey identified D, He, B, Li, C, N, O, Ne lines and provided plasma Te, ne estimates from deuterium Paschen and Brackett series intensity and Stark line broadening analysis. The range 1.000-1.060 mm was surveyed in high-density and neon seeded divertor plasmas for spectral background emission studies for λ = 1.064 μm laser-based DTS development. The ratio of adjacent deuterium Paschen-α and Brackett Br9 lines in recombining divertor plasmas is studied for divertor Te monitoring aimed at divertor detachment real-time feedback control.

Electrical characteristics of Au/Ti/n-GaAs contacts over a wide measurement temperature range

We have fabricated Au/Ti/n-GaAs/In Schottky barrier diodes using the magnetron dc sputter technique. The capacitance–temperature (C–T) measurements with bias voltage as a parameter and the current–voltage (I–V) and capacitance–voltage (C–V) measurements have been made in the temperature range of 60–300 K. The temperature-dependent capacitance measurements have been made at 1.0 MHz. The capacitance versus temperature curve at each bias voltage has four regions with slopes different from each other. The capacitance decreases with a decrease in temperature at each bias voltage. Such a temperature-dependent behavior could be attributed to modulation of the space charge region caused by the emission of deep-level impurities or interface states. The carrier concentration calculated in the −1.0 to −2.0 V range of C−2–V plots was close to the value of 7.43 × 1015 cm−3 given by the manufacturer around room temperature. The ideality factor value from the I–V characteristics has remained almost unchanged between 1.07 and 1.10 in the temperature range of 150–300 K, indicating that the current across the device obeys the thermionic emission current model quite well over the whole bias range at temperatures above 150 K. Therefore, the conventional Richardson plot in this temperature range has given a Richardson constant of 8.21 A (cm K)−2, within experimental error, which is in very close agreement with the theoretical value of 8.16 A (cm K)−2 for n-type GaAs. Again, it has been seen that the ideality factor with the values of 1.10 at 150 K and 1.22 at 60 K does not show a considerable decrease. The experimental parameters show that the Au(90 nm)/Ti(10 nm)/n-GaAs contact is a good candidate for electronic device applications.

Test of prototype ITER vacuum ultraviolet spectrometer and its application to impurity study in KSTAR plasmas.

To optimize the design of ITER vacuum ultraviolet (VUV) spectrometer, a prototype VUV spectrometer was developed. The sensitivity calibration curve of the spectrometer was calculated from the mirror reflectivity, the grating efficiency, and the detector efficiency. The calibration curve was consistent with the calibration points derived in the experiment using the calibrated hollow cathode lamp. For the application of the prototype ITER VUV spectrometer, the prototype spectrometer was installed at KSTAR, and various impurity emission lines could be measured. By analyzing about 100 shots, strong positive correlation between the O VI and the C IV emission intensities could be found.

Time-resolved Photoluminescence Characterisation of GaAs/AlxGa1–xAs Structures Designed for Microwave and Terahertz Detectors

The time-resolved photoluminescence of donor Si-doped GaAs/AlxGa1-xAs (x = 0.3 0.25, 0.2, 0.1) structures designed for microwave and terahertz detectors have been investigated at T = 3.6 K temperature. The excitonic, impurity and defect related emission lifetimes are revealed for these structures. Possible mechanisms of carrier recombination are discussed. Concentration of acceptor, carbon and silicon, are evaluated from measured lifetimes in the structures. DOI: http://dx.doi.org/10.5755/j01.ms.20.2.6317

First results of flowing liquid lithium limiter in HT-7

Two different types of flowing liquid lithium limiters were firstly installed and successfully tested in HT-7 tokamaks in 2012 and some encouraging results were obtained. Two limiters of the first type, called FLiLi limiters, used a thin lithium layer flowing under gravity. The other type had lithium-metal infused trenches (LIMIT) for thermoelectric magnetohydrodynamic drive of the liquid metal flow. The surface of one of the FLiLi limiters was coated by evaporated lithium before liquid lithium was injected by Ar pressure into a special distributor of the limiter. Then the liquid lithium could slowly move along the plasma facing guide surface of the limiter due to gravity. For LIMIT, it was found that liquid lithium could flow along the trenches as expected with a velocity of about 3.7 ± 0.5 cm s−1 driven by the electromagnetic force, which came from the interaction between the thermoelectric current and magnetic field. Use of flowing liquid lithium limiters in HT-7 resulted in reduction of particle recycling, suppression of impurity emission and improvement of the confinement.

THE ASSESSMENT OF THE POLLUTANT EMISSION FROM THE SELF IGNITION ENGINE IN ITS DIFFERENT OPERATING STATES

Paper presents the results of pollutant emission tests from the self ignition engine in various states of its operation. Engine operating states were obtained on the engine test stand. The investigations were conducted in static and dynamic tests, both standard used in the type approval procedures as special ones, simulating specific engine operating conditions. The specific brake emission of carbon monoxide as well as those of hydrocarbons, nitrogen oxides and particulate matter, averaged during the tests, have been determined. The influence of the engine operating states on the pollutant emission of impurities has been evaluated. Very high sensitivity was established of the pollutant specific brake emission on the operating states of the engine, both static ones and dynamic.

Ion temperature and radial profile of CII-CV located in the edge and divertor plasmas of large helical device

Space-resolved vacuum ultraviolet (VUV) spectroscopy using a 3-m normal incidence spectrometer is utilized to measure the impurity emission profile in the edge and divertor plasmas of the Large Helical Device (LHD). It measures the vertical profile of VUV lines emitted in the wavelength range of 300–3200 °A. CII, CIII, CIV, and CV lines emitted from carbon ions are successfully measured, and their ion temperatures are derived from the Doppler broadening. Vertical profiles of the emission intensity and the ion temperature are measured simultaneously for the CIV line. The emission intensity profile, which has several peak structures, is reasonably explained by considering the relation between the C3+ ion distribution and the geometry used for the observations.