1,720,956 research outputs found
Advanced Thomson scattering techniques as diagnostics for fusion plasmas
Full text linkThe content of this thesis was carried out within the framework of the global magnetic confinement fusion (MCF) effort. The flagship project for MCF is the International Thermonuclear Experimental Reactor (ITER), currently under construction and due for commissioning in 2025. ITER is an unprecedented device that pushes the limits of technology and physics across all sectors, and the field of plasma diagnostics is no exception.
Thomson scattering (TS) is one of the most powerful diagnostics available to fusion devices, providing high resolution spatial and temporal profiles of the plasma electron temperature and electron density, which are measurements vital to the understanding of the plasma. Although conventional TS is a well proven method and used in almost all MCF devices in current operation, it too must advance and adapt to the demanding environment of ITER. In this thesis we explore two advanced Thomson scattering techniques which aim to address some of the challenges of ITER TS, through three independent experiments performed on three separate devices.
Chapter 1 provides a brief introduction to MCF as part of the solution to the current global energy crisis.
Chapter 2 introduces the general theory of Thomson scattering and a description of the advanced techniques under investigation.
Chapter 3 describes the dual-laser TS experiment performed in RFX-mod, Padova, during the first year of the PhD. To the author’s knowledge, this was the first successful practical testing of this advanced technique.
Chapter 4 describes the polarimetric TS experiment performed in JET, Oxford, during the second year of the PhD. To the author’s knowledge, this was the first successful practical testing of this advanced technique.
Chapter 5 describes the dual-laser TS experiment performed in LHD, Japan, during the second year of the PhD. To the author’s knowledge, this was the second successful practical testing of this technique.
The experiments performed and described in this thesis demostrate the feasibility of these two previously untested advanced TS techniques, which are both of great interest for application in the next generation of fusion devices.I contenuti di questa tesi sono stati svolti nella cornice della ricerca globale sulla Fusione nucleare a Confinamento Magnetico (FCM). Il progetto guida per la FCM è ITER (International Thermonuclear Experimental Reactor), in costruzione a Cadarache, nel sud della Francia, e con messa in esercizio prevista per il 2025. ITER è una macchina senza precedenti, che spinge all’estremo i limiti della tecnologia e della scienza in tutti i settori, e il campo della diagnostica di plasma non fa eccezione.
Lo scattering Thomson (ST) è una delle diagnostiche più potenti tra quelle disponibili su una macchina a fusione, ed è in grado di misurare con elevata risoluzione spaziale e temporale la temperatura e la densità degli elettroni, misure chiave per lo studio dei plasmi. Sebbene lo ST sia una diagnostica già collaudata e in uso su quasi tutte le macchine a fusione esistenti, anch’esso deve essere migliorato e reso adatto agli esigenti requisiti di ITER. In questo lavoro di tesi sono state esplorate due tecniche di scattering Thomson avanzato che hanno lo scopo di risolvere alcune delle sfide dello ST di ITER attraverso tre esperimenti indipendenti svolti su tre macchine separate.
Capitolo 1 fornisce una breve introduzione alla FCM vista come parte della soluzione all’attuale crisi globale dell’energia.
Capitolo 2 introduce la teoria generale dello scattering di Thomson e una descrizione delle tecniche avanzate trattate in questo lavoro di tesi.
Capitolo 3 descrive l’esperimento di ST con laser duale svolto su RFX-mod, Padova, durante il primo anno di dottorato. Questo è stato per l’autore il primo esperimento svolto con successo su questa tecnica avanzata.
Capitolo 4 descrive l’esperimento di ST polarimetrico svolto su JET, Oxford, durante il secondo anno di dottorato. Questo è stato per l’autore il primo esperimento svolto con successo su questa tecnica avanzata.
Capitolo 5 descrive l’esperimento di ST con laser duale svolto su LHD, Giappone, durante il secondo anno di dottorato. Questo è stato per l’autore il secondo esperimento svolto con successo su questa tecnica avanzata.
Gli esperimenti svolti, descritti in questo lavoro di tesi, dimostrano la fattibilità di queste due tecniche di ST avanzato, mai testate prima, e che sono entrambe di grande interesse per l’applicazione sulla prossima generazione di macchine a fusione
Dual-laser, self-calibrating Thomson scattering measurements in RFX-mod
No full textA self-calibrating Thomson scattering technique, based on using two lasers of different wavelength and never implemented before in a fusion experiment, is tested for the first time in RFX-mod. The method employs two laser systems, Nd:YAG (λ = 1064 nm) and Nd:YLF (λ = 1053 nm), fired in sync through the same plasma volume. The combination of the two scattered spectra, individually recorded, is used to simultaneously obtain the measurements of the electron temperature Te and the relative calibration coefficients of the polychromator spectral channels sensitivities Ci. This work is a continuation of the dual-angle technique, a similar alternative method. Due to the small difference in the wavelengths of the two lasers, the sensitivity of this method is low in RFX-mod and reliable measurements of the calibration coefficients could not be obtained on a shot-to-shot basis, but only with a statistical analysis of a reasonable number of pairs of laser shots with good signal-to-noise ratio. The dual-laser method can be applied to most fusion devices and could provide continuous online monitoring of the spectral transmission of the detection system. This may prove essential in larger devices (ITER), where access for traditional calibration is difficult
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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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