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Development of the B-Stark motional Stark effect diagnostic for measurements of the internal magnetic field in the DIII-D tokamak
Get PDFA new diagnostic, B-Stark, has been developed at the DIII- D tokamak for measurements of the magnitude and direction of the internal magnetic field. The B-Stark system is a version of a motional Stark effect (MSE) diagnostic based on the Stark split D/[alpha] emission from injected neutral beams. This diagnostic uses the spacing of the Stark lines to measure the magnitude of the magnetic field, and the intensities of the [pi]₃ and [sigma]₁ lines to measure the magnetic pitch angle. These lines originate from the same upper level, and are therefore not dependent on the n=3 level populations. The measurement of the magnetic pitch angle requires a specific viewing geometry with respect to the neutral beams, which is provided by the B-Stark diagnostic installation. The B-Stark technique may have advantages over MSE polarimetry diagnostics in future devices with high densities and temperatures, such as ITER. Under these conditions coatings on the plasma facing mirrors are expected, which can cause changes in the polarization state of the reflected light. The B-Stark technique is insensitive to the polarization direction, and can calibrate for polarization dependent transmission by using an in-situ beam-into-gas calibration. This dissertation describes the development and characterization of the B-Stark diagnostic. The hardware design and spectral fitting techniques are discussed in detail. Calibration procedures are described including the in-situ determination of the beam emission line profiles, viewing geometry and properties of the collection optics. The performance of the system is evaluated over the range of plasma conditions accessible at DIII-D. Measurements of the magnetic field have been made with toroidal fields in the range 1.2 - 2.1Tesla, plasma currents in the range 0.5 - 2.0MA, densities between 1.7 - 9.0 x 10¹⁹m⁻³, and neutral beam voltages between 50 - 81keV. These results are compared to values found from plasma equilibrium reconstructions (EFIT) and the MSE polarimetry system on DIII-D. The B-Stark system has been shown to provide measurements with a random errors as low as 0.2-0.3° in the magnetic pitch angle and 0.001-0.002T in [B]. Finally, proposed future improvements for the B-Stark diagnostic are presente
Modeling and Measurement of Fast Ion Losses in Wendelstein 7-X
No full textThe confinement of fast ions, whether produced by fusion in a reactor or by heating methods such as neutral beam injection (NBI) and ion cyclotron resonance heating (ICRH), is crucial to the efficient operation of a fusion reactor or other plasma device. In stellarators, the lack of toroidal symmetry leads to poor confinement unless the magnetic geometry is optimized. The largest optimized stellarator in operation, Wendelstein 7-X (W7-X), was designed for good fast ion confinement at high plasma pressure ⟨β⟩ and high mirror ratio Bmax/Bmin by targeting a feature known as quasi-omnigeneity, in which the bounce-averaged radial drifts of trapped particles are minimized. To confirm the success of this optimization, diagnostics such as fast ion loss detectors (FILDs) are used to measure the losses of fast ions from W7-X.
This work concerns the design of a scintillating FILD (S-FILD) for steady-state operation in W7-X, which will make use of a pair of pinhole-and-slit collimators, a phosphor-coated scintillator plate, a Faraday Cup, and a fast video camera to measure energy-and-pitch-resolved losses of NBI-produced fast ions. Because the 3D structure of the magnetic field means that the loss pattern is strongly localized, going from a measurement of losses at a single location to an assessment of overall confinement is non-trivial. A method has been developed for determining expected FILD signals from Monte Carlo simulations of fast ions in the plasma and their overall losses. This method is first used to reproduce experimental measurements made by a multi-channel Faraday Cup FILD (NIFS-FILD) currently in use on W7-X, finding the first quantitative agreement between simulation and measurement of fast ion losses on this device. The method is then used to predict both total ion flux to the S-FILD as well as the spatial distribution of this flux on the scintillator plate. Finally, based on these results, a potential update to the S-FILD design is suggested in order to improve the ability to measure counter-going fast ions
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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