Author: Jian Wang
Publisher:
ISBN:
Category :
Languages : en
Pages : 196

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Author: Xiaoxin Ren
Publisher:
ISBN: 9781369201437
Category :
Languages : en
Pages :

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The Tokamak is one of the most-researched candidates for producing controlled thermonuclear fusion power. Its confinement quality is highly limited by micro-scale as well as MHD turbulence in plasma. The UC Davis Millimeter-Wave group is dedicated to the development of tools, mainly Electron Cyclotron Emission Imaging (ECEI) and Microwave Imaging Reflectometry (MIR) to diagnose turbulence in plasmas. Here, ECEI and MIR are used to diagnose temperature and density fluctuations in the cross section of a Tokamak. In this dissertation, the focus is on the development of the MIR system, and more specifically, on the development and applications of a synthetic MIR diagnostic. The synthetic MIR helps in the design stage by optimizing and validating optical lens parameters of the imaging system. It also helps to determine the possible operating space of a MIR system. With the help of synthetic MIR, an MIR system was successfully installed on the DIII-D Tokamak. MIR then achieved great performance in measuring a wide range of MHD instabilities, for instance, strong inter-ELM modes in H-mode operation plasmas. Synthetic MIR then helps to interpret experimental data, and was used for edge harmonic oscillation studies and provides a proxy between the plasma simulation codes and real plasma. This dissertation first emphasizes the importance of fusion and fusion turbulence diagnostics; it then covers the principles of the MIR system, the hardware of the DIII-D MIR system, and then goes deeply into the process of synthetic MIR. Afterwards, the dissertation focuses on the analytical results from synthetic MIR simulations for defining the MIR instrumental function, and also how it helped to calibrate the DIII-D MIR system and interpret experimental data. Then, the dissertation concludes with future software and hardware upgrades for both synthetic and real MIR systems.

Author: Hyeon Keo Park
Publisher:
ISBN:
Category : Fluctuations (Physics)
Languages : en
Pages : 20

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Author:
Publisher: ScholarlyEditions
ISBN: 1464964114
Category : Science
Languages : en
Pages : 1751

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Book Description
Issues in Applied, Analytical, and Imaging Sciences Research: 2011 Edition is a ScholarlyEditions™ eBook that delivers timely, authoritative, and comprehensive information about Applied, Analytical, and Imaging Sciences Research. The editors have built Issues in Applied, Analytical, and Imaging Sciences Research: 2011 Edition on the vast information databases of ScholarlyNews.™ You can expect the information about Applied, Analytical, and Imaging Sciences Research in this eBook to be deeper than what you can access anywhere else, as well as consistently reliable, authoritative, informed, and relevant. The content of Issues in Applied, Analytical, and Imaging Sciences Research: 2011 Edition has been produced by the world’s leading scientists, engineers, analysts, research institutions, and companies. All of the content is from peer-reviewed sources, and all of it is written, assembled, and edited by the editors at ScholarlyEditions™ and available exclusively from us. You now have a source you can cite with authority, confidence, and credibility. More information is available at http://www.ScholarlyEditions.com/.

Author: Xing Hu
Publisher:
ISBN: 9780355149487
Category :
Languages : en
Pages :

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Nuclear fusion is one of the promising ways to generate renewable energy to solve the current energy crisis. However, controlled nuclear fusion with net power gain has not yet been achieved due to the instabilities inside the fusion plasmas. In order to control and eliminate these instabilities, diagnostic tools have been developed to understand the physics. Most of the characteristic frequencies of fusion plasmas fall within the millimeter wave region of the electromagnetic spectrum, which makes microwave imaging systems excellent tools for visualizing the particle activities inside fusion plasmas. There are two types of microwave imaging diagnostic systems developed at the Plasma Diagnostic Group at UC Davis: one is the electron cyclotron emission imaging (ECEI) system, which measures the ECE radiation from the plasma to determine electron temperature fluctuation and the other is the microwave imaging reflectometer (MIR), which injects multi-frequency probing beams into the plasma and measures the reflected beams from different cutoff surfaces to determine the electron density fluctuation. In this dissertation, the hardware setup of both ECEI and MIR systems is discussed. Characterization of the ECEI system for the HL-2A tokamak at Chengdu, China, and the MIR system for the DIII-D tokamak at La Jolla, USA, are given as an introduction to the laboratory testing methods of these microwave imaging systems. The topic of particular emphasis in this dissertation is the development of the latest generation MIR system for the EAST tokamak at Hefei, China. This system consists of 8 radial channels separated by different probing frequencies ranging from 75 to 103 GHz, and 12 vertically separated receiving channels, providing 96 imaging pixels inside the fusion plasma. As an important protection to the receiver system, development of the frequency selective surface based notch filter is discussed. The improved notch filter resonating at 140 GHz for the EAST MIR system has reduced the pass band insertion loss by half while maintaining over 30 dB rejection at the stop band. The implementation of embedded microcontrollers and RF components with serial peripheral interface (SPI) enables the system to be remotely controlled over the Ethernet. Technology advancements for future MIR systems including the CMOS based transmitter on chip and the digital beam forming technology are briefly discussed at the end of this dissertation.

Author: Li Juan Lei
Publisher:
ISBN: 9781124508993
Category :
Languages : en
Pages :

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Microwave Imaging Reflectometry (MIR) systems have been used as diagnostic tools for characterization of fluctuating plasma density in large tokamaks. Such a technique has been implemented on the TEXTOR device [H. Park, et al., Review of Scientific Instruments, 2004] and is being continued on DIII-D and KSTAR. To develop a new MIR system for density fluctuation measurements for DIII-D and KSTAR, one requires an understanding of how to preserve phase information. The current design for an MIR optical system makes use of design tools in free space, which is great for evaluation of port access but not provide significant information when it comes to the plasma region. This thesis describes a numerical study of MIR in the presence of turbulent fluctuations by evaluating the effectiveness in coupling the reflection layer in the full wave region and the detector array in free space with respect to fluctuation levels. A synthetic diagnostic tool making use of 2D full-wave diffractive simulation in full plasma geometry is applied to couple an optical imaging system with different optical arrangements.

Author: Jian Wang
Publisher:
ISBN:
Category :
Languages : en
Pages : 396

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Author: E. Mazzucato
Publisher:
ISBN:
Category : Turbulence
Languages : en
Pages : 22

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Author: Lu Yang
Publisher:
ISBN:
Category :
Languages : en
Pages : 348

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Author: Fengqi Hu
Publisher:
ISBN: 9780355149494
Category :
Languages : en
Pages :

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Book Description
In recent years, the exponentially increasing energy requirements and the serious environmental problems caused by traditional fossil sources have drawn tremendous attention to the development of alternative energy sources. One of the most promising candidates is nuclear fusion energy. To study the fundamental physical phenomena inside the confined hot plasma of which the temperatures are in excess of 100 million Kelvin, advanced imaging systems are being developed with millimeter wave imaging systems of particular importance. The Microwave Imaging Reflectometry (MIR) developed at UC Davis is an active radar imaging system used to measure the electron density fluctuations. In the currently employed system, carefully designed optical lenses are used to shape the probing beam so that it would impinge upon the plasma cutoff surface with normal incidence. On the receiver side, another set of lenses are used to collect and further shape the beam to form an image of the cutoff surface. The focusing is done by motor controlled lenses, which not only take up more space but also are slow to adjust compared to many plasma times of interest. Phased array synthesis offers the ability to change the shaping and steering of the beam electronically for fast-tracking and remote tuning without the need for bulky lenses. Based on where in the system the phase shifting is performed, there are two major categories of phased array. One is the analog phased array where the beam shaping and steering are done in the analog domain with analog phase shifters. The other approach is digital beamforming where the amplitude scaling and the phase shifting are realized by mathematical operations in the digital domain. Compared to its analog counterpart, digital beam forming could be done much faster with great flexibility. The focus of this dissertation is the utilization of digital beam forming to realize high speed focusing with greater flexibility. The beam shaping, focusing/de-focusing, beam steering and beam translation with digital beam forming are demonstrated with a simplified W-band receiver system. The possibility of a V-band system-on-substrate with on-board LO feed is also explored.