Ping-Rey Jang

Optical diagnostics of a low power?low gas flow rates atmospheric-pressure argon plasma created by a microwave plasma torch

We employ a suite of optical techniques, namely, visual imaging, optical emission spectroscopy and cavity ringdown spectroscopy (CRDS), to characterize a low power, low gas flow rates, atmospheric-pressure argon microwave induced plasma. The plasma is created by a microwave plasma torch, which is excited by a 2.45 GHz microwave with powers ranging from 60 to 120 W. A series of plasma images captured in a time-resolution range of as fine as 10 µs shows that the converging point is actually a time-averaged visual effect and the converging point does not exist when the plasma is visualized under high time resolution, e.g. <2 ms. Simulations of the emission spectra of OH, N2 and in the range 200–450 nm enable the plasma electronic excitation temperature (Texc) to be determined at 8000–9000 K, while the vibrational temperature (Tv), the rotational temperature (Tr) and the gas temperature (Tg) at different locations along the axis of the plasma column are all determined to be in the range 1800–2200 K. Thermal equilibrium properties of the plasma are discussed. OH radical concentrations along the plasma column axis are measured by CRDS and the concentrations are in the range 1.6 × 1013–3.0 × 1014 cm−3 with the highest density at the tail of the plasma column. The upper limit of electron density ne is estimated to be 5.0 × 1014 cm−3 from the Lorentzian component of the broadened lineshape obtained by ringdown spectral scans of the rovibrational line S21 of the OH A–X (0–0) band.

Optical Properties of Gaseous 2,4,6-Trinitrotoluene in the Ultraviolet Region

The absorption spectrum of gaseous 2,4,6-trinitrotoluene (TNT) was recorded by conventional absorption spectroscopy (AS) as well as cavity ringdown spectroscopy (CRDS) methods in the spectral regions 195–300 and 225–235 nm, respectively. These spectra were normalized by using the saturated TNT vapor-number density for the measured cell temperature to obtain the absorption cross section of TNT. No spectral features were found in the spectra; this result is consistent with a repulsive electronic excited state of TNT. The temperature dependence of the absorption coefficient of saturated TNT vapor was measured within the temperature range 5–110 °C. The limit of detection of TNT vapor by CRDS is less than 1 ppb. Real-time CRDS measurements of the TNT vapor density at 21 and 37 °C are presented. The TNT evaporation rates were found to be 7 × 108 and 4 × 1010 molecules/cm2 × s at 21 and 37 °C, respectively.

USE OF OPTICAL AND IMAGING TECHNIQUES FOR INSPECTION OF OFF-LINE JOULE-HEATED MELTER AT THE WEST VALLEY DEMONSTRATION PROJECT

The West Valley melter has been taken out of service. Its design is the direct ancestor of the current melter design for the Hanford Waste Treatment Plant. Over its eight years of service, the West Valley melter has endured many of the same challenges that the Hanford melters will encounter with feeds that are similar to many of the Hanford double shell tank wastes. Thus, inspection of the West Valley melter prior to its disposal could provide valuable — even crucial — information to the designers of the melters to be used at the Hanford Site, particularly if quantitative information can be obtained. The objective of Mississippi State University’s Diagnostic Instrumentation and Analysis Laboratory’s (DIAL) efforts is to develop, fabricate, and deploy inspection tools for the West Valley melter that will (i.) be remotely operable in the West Valley process cell; (ii.) provide quantitative information on melter refractory wear and deposits on the refractory; and (iii.) indicate areas of heterogeneity of deposits, requiring more detailed characterization. A collaborative arrangement has been established with the West Valley Demonstration Project (WVDP) to inspect their melter.Copyright

Evaluation of Fourier Transform Profilometry Performance: Quantitative Waste Volume Determination Under Simulated Hanford Waste Tank Conditions

The Hanford Site is currently in the process of an extensive effort to empty and close its radioactive single-shell and double-shell waste storage tanks. Before this can be accomplished, it is necessary to know how much residual material is left in a given waste tank and the chemical makeup of the residue. The objective of Mississippi State University’s Institute for Clean Energy Technology’s (ICET) efforts is to develop, fabricate, and deploy inspection tools for the Hanford waste tanks that will (1) be remotely operable; (2) provide quantitative information on the amount of wastes remaining; and (3) provide information on the spatial distribution of chemical and radioactive species of interest. A collaborative arrangement has been established with the Hanford Site to develop probe-based inspection systems for deployment in the waste tanks. ICET is currently developing an in-tank inspection system based on Fourier Transform Profilometry, FTP. FTP is a non-contact, 3-D shape measurement technique. By projecting a fringe pattern onto a target surface and observing its deformation due to surface irregularities from a different view angle, FTP is capable of determining the height (depth) distribution (and hence volume distribution) of the target surface, thus reproducing the profile of the target accurately under a wide variety of conditions. Hence FTP has the potential to be utilized for quantitative determination of residual wastes within Hanford waste tanks. We have completed a preliminary performance evaluation of FTP in order to document the accuracy, precision, and operator dependence (minimal) of FTP under conditions similar to those that can be expected to pertain within Hanford waste tanks. Based on a Hanford C-200 series tank with camera access through a riser with significant offset relative to the centerline, we devised a testing methodology that encompassed a range of obstacles likely to be encountered “in-tank.” These test objects were inspected by use of FTP and the volume of the test objects determined. The volumes of nondescript test objects were independently determined and were not known to the FTP operators. Several stages of testing are ongoing with successive stages imposing aspects that present increasing difficulty and increasingly more accurate approximations of in-tank environments. We report the Stage 1 results of this multi-stage evaluation of FTP performance.Copyright

Technical Performance Characterization of Fourier Transform Profilometry for Quantitative Waste Volume Determination Under Hanford Waste Tank Conditions

The Hanford Site in western Washington state is currently in the process of an extensive effort to empty and close its radioactive single-shell and double-shell waste storage tanks. Before this can be accomplished, it is necessary to know how much residual material is left in a given waste tank and the chemical makeup of the residue. The Institute for Clean Energy Technology (ICET) at Mississippi State University is currently developing an quantitative in-tank inspection system based on F ourier T ransform P rofilometry, FTP. FTP is a non-contact, 3-D shape measurement technique. By projecting a fringe pattern onto a target surface and observing its deformation due to surface irregularities from a different view angle, FTP is capable of determining the height (depth) distribution (and hence volume distribution) of the target surface, thus reproducing the profile of the target accurately under a wide variety of conditions. Hence FTP has the potential to be utilized for quantitative determination of residual wastes within Hanford waste tanks. We report the results of a technical feasibility study to document the accuracy and precision of quantitative volume determination using the Fourier transform profilometry technique under simulated Hanford waste tank conditions.Copyright

OPTIMIZATION OF QUANTITATIVE WASTE VOLUME DETERMINATION TECHNIQUE FOR HANFORD WASTE TANK CLOSURE

The Hanford Site is currently in the process of an extensive effort to empty and close its radioactive single-shell and double-shell waste storage tanks. Before this can be accomplished, it is necessary to know how much residual material is left in a given waste tank and the uncertainty with which that volume is known. The Institute for Clean Energy Technology (ICET) at Mississippi State University is currently developing a quantitative in-tank imaging system based on Fourier Transform Profilometry, FTP. FTP is a non-contact, 3-D shape measurement technique. By projecting a fringe pattern onto a target surface and observing its deformation due to surface irregularities from a different view angle, FTP is capable of determining the height (depth) distribution (and hence volume distribution) of the target surface, thus reproducing the profile of the target accurately under a wide variety of conditions. Hence FTP has the potential to be utilized for quantitative determination of residual wastes within Hanford waste tanks. In this paper, efforts to characterize the accuracy and precision of quantitative volume determination using FTP and the use of these results to optimize the FTP system for deployment within Hanford waste tanks are described.Copyright

Characterization of a low temperature atmospheric-pressure argon microwave induced plasma using visual imaging, OES, and CRDS combined

We employ a suite of optical techniques, visual imaging, optical emission spectroscopy (OES), and cavity ringdown spectroscopy (CRDS), to characterize a low power, low gas flow rates, atmospheric-pressure argon microwave induced plasma (MIP). A series of plasma images captured in a time resolution range of 10 µs – 0.05 s shows that the converging point is a visual effect of integrating the image of a rapidly rotating conical helix. The plasma electronic excitation temperature Texc, vibrational temperature Tv, rotational temperature Tr, and gas temperature Tg at different locations along the axis of the plasma column are determined from the simulations of the emission spectra of OH, N2 and N2+ in the range of 200 – 450 nm. Thermal equilibrium properties of the plasma are discussed. OH radical concentrations along the plasma column axis are measured by CRDS and the effects of plasma gas compositions on the generation of OH radicals are investigated. An upper limit of electron density ne is estimated from the Lorentzian component of the broadened lineshape obtained by ringdown spectral scans of the rovibrational line S21 of the OH A-X (0-0) band.

Fluorescence Spectral Imaging as a Tool for Locating Uranium Deposited on Surfaces

In the environment, metallic uranium readily oxidizes to form uranium compounds that contain the uranyl (UO2+2) moiety. For more than a hundred and fifty years, it has been known that when illuminated with ultraviolet (UV) light, uranyl compounds exhibit characteristic fluorescence in the visible region (450–650 nm). We report our efforts to develop a transportable, quantitative Fluorescence Spectral Imaging (FSI) system as a tool for locating and quantifying uranyl compounds dispersed in soils and on other surfaces. A project is underway to develop a set of sensors to locate expended depleted uranium (DU) rounds and to process soil and debris to recover the material from domestic firing ranges. The FSI system can also be utilized to monitor excavation of DU munitions and separation of uranyl compounds from soils. FSI images are acquired by illuminating a surface with a UV light and using a narrow bandpass filter on a camera, recording an image of the resulting fluorescence. The FSI image provides both spatial and spectral information. The FSI system is described and its performance characterized using field samples.Copyright

Ground-based imaging system for soil surface roughness measurement

Surface roughness is an important physical property of soil in agricultural applications. It is a key parameter affecting the optical reflectance of bare soils, which can be computed from imagery acquired with airborne or space-based remotesensing devices. Accurate ground-truth roughness data need to be collected before a correct computational interpretation can be made. This paper presents the development of a real-time, geo-referenced, ground-based imaging system that produces quantitative ground truth information of soil surface roughness. The system applies Fourier transform profilometry (FTP) to an image of a soil area under study to obtain relative height data of the surface. Then it computes parameters such as root mean square (RMS) and correlation length as measures of roughness. Measurement experiments have been carried out successfully both under simulated conditions in the laboratory and in the field. The results show that the system is capable of generating reliable ground-truth soil surface roughness information. In comparison with other approaches, this developed system is fast, efficient and inexpensive.

Gabor wavelet image analysis for soil texture classification

Soil texture is an important physical property of soil that affects many agricultural activities. It describes soil composition in terms of the relative proportion of three typical sized particles, i.e., clay, silt and sand. Traditional soil texture analysis methods involve inefficient physical and chemical processing procedures. To improve the efficiency for the analysis, previously we proposed a wavelet frame based image analysis system that related textural patterns observed at soil surface to the particle compositions. The system was capable of differentiating between 33 soil samples in terms of three categories with a 91% success rate. However, it required image acquisition under two camera settings. In this paper, we further our investigation with an improved image analysis approach, in which Gabor wavelets are utilized to generate textural features. Experiments showed that a combination of analysis results from two groups of Gabor wavelets yielded a 91% classification accuracy. Although the accuracy remained unchanged, the Gabor wavelet based system provided improved efficiency and flexibility over the previous system in that it needs only one set of images acquired under a fixed camera setting. Moreover, an improved consistency between individual classification votes was observed with the new system, indicating a greater potential for a finer categorization of soil textures.