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Diii D Experiments And Modeling Of Core Confinement In Quiescent Double Barrier Plasmas
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Book Synopsis DIII-D Experiments and Modeling of Core Confinement in Quiescent Double Barrier Plasmas by :
Download or read book DIII-D Experiments and Modeling of Core Confinement in Quiescent Double Barrier Plasmas written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We continue to explore Quiescent Double Barrier (QDB) operation on DIII-D to address issues of critical importance to internal transport barrier (ITB) plasmas. QDB plasmas exhibit both a core transport barrier and a quiescent, H-mode edge barrier. Both experiments and modeling of these plasmas are leading to an increased understanding of this regime and it's potential advantages for advanced-tokamak (AT) burning-plasma operation. These near steady plasma conditions have been maintained on DIII-D for up to 4s, times greater than 35[tau][sub E], and exhibit high performance with [beta][sub N]> 2.5 and neutron production rates S[sub n] [approx] 1 x 10[sup 16]s[sup -1]. Recent experiments have been directed at exploring both the current profile modification effects of electron cyclotron current drive (ECCD) and electron cyclotron (ECH) heating-induced changes in temperature, density and impurity profiles. We use model-based analysis to determine the effects of both heating and current drive on the q-profile in these QDB plasmas. Experiments based on predictive modeling achieved a significant modification to the q-profile evolution [1] resulting from the non-inductive current drive effects due to direct ECCD and changes in the bootstrap and neutral beam current drive components. We observe that the injection of EC power inside the barrier region changes the density peaking from n[sub e]/n[sub e] = 2.1 to 1.5 accompanied by a significant reduction in the core carbon and high-Z impurities, nickel and copper.
Book Synopsis DIII-D Experiments and Modeling of Core Confinement in Quiescent Double Barrier Plasmas by : T. H. Osborne
Download or read book DIII-D Experiments and Modeling of Core Confinement in Quiescent Double Barrier Plasmas written by T. H. Osborne and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We continue to explore Quiescent Double Barrier (QDB) operation on DIII-D to address issues of critical importance to internal transport barrier (ITB) plasmas. QDB plasmas exhibit both a core transport barrier and a quiescent, H-mode edge barrier. Both experiments and modeling of these plasmas are leading to an increased understanding of this regime and it's potential advantages for advanced-tokamak (AT) burning-plasma operation. These near steady plasma conditions have been maintained on DIII-D for up to 4s, times greater than 35{tau}{sub E}, and exhibit high performance with {beta}{sub N}> 2.5 and neutron production rates S{sub n} {approx} 1 x 10{sup 16}s{sup -1}. Recent experiments have been directed at exploring both the current profile modification effects of electron cyclotron current drive (ECCD) and electron cyclotron (ECH) heating-induced changes in temperature, density and impurity profiles. We use model-based analysis to determine the effects of both heating and current drive on the q-profile in these QDB plasmas. Experiments based on predictive modeling achieved a significant modification to the q-profile evolution [1] resulting from the non-inductive current drive effects due to direct ECCD and changes in the bootstrap and neutral beam current drive components. We observe that the injection of EC power inside the barrier region changes the density peaking from n{sub e}/n{sub e} = 2.1 to 1.5 accompanied by a significant reduction in the core carbon and high-Z impurities, nickel and copper.
Book Synopsis DIII-D Quiescent Double Barrier Regime Experiments and Modeling by :
Download or read book DIII-D Quiescent Double Barrier Regime Experiments and Modeling written by and published by . This book was released on 2002 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: Discharges characteristic of the quiescent double barrier (QDB) regime [1] are attractive for development of advanced tokamak (AT) scenarios relevant to fusion reactors [2] and they offer near term advantages for exploring and developing control techniques. We continue to explore the QDB regime in DIII-D to improve understanding of formation and control of these discharges and to explore scaling to steady-state reactors. The formation of an internal transport barrier (ITB) provides a naturally peaked core pressure profile. This peaking in density in combination with the H-mode-like edge barrier and pedestal provide a path to high performance. We have achieved [beta]{sub N}H{sub 89P} H"7 for several energy confinement times (d"25 [tau]{sub E}). We discuss here a combination of modeling and experiments using electron cyclotron heating (ECH) and current drive (ECCD) to demonstrate steady state, current-driven equilibria and control of the current distribution, safety factor q, and density profile. Experimental conditions leading to formation of the QDB discharge require establishing two distinct and separated barrier regions, a core region near [rho] H"0.5 and an edge barrier outside [rho]> 0.95, [rho] is the square root of toroidal flux (radial coordinate). A region of higher transport due to a change in polarity of the E x B shearing rate [1] separates the core barrier from the H-mode edge. It is this separation in barriers that so far has required use of counter-NBI to establish QDB conditions. Balanced NBI should also allow this separation of barriers. The edge corresponds to the quiescent H-mode (QH) conditions [3]. In this quiescent edge region, the normally observed transient loss associated with edge-localized-mode (ELM) activity is replaced with a steady particle loss driven by a coherent oscillation residing outside the pedestal region. This edge harmonic oscillation (EHO) [2] typically exhibits 2 or 3 harmonics of a fundamental frequency near 10 kHz. We find this combination of a core ITB and the QH-mode edge to be extremely robust and to produce slowly varying, high performance discharge parameters, Fig. 1, for long durations H"3 s. These conditions are generally limited by the duration of the NBI system and a slow evolution to lower q values as the Ohmic current moves inward on the resistive time scale for diffusion.
Book Synopsis Fernere Bekräftigung der nöthigen Beilage und gründliche Erinnerungen zu dem ersten Abschnitt des 5. Bandes der teutschen Staatskanzlei des Herrn Dr. Reuss, vom Jahrgang 1799, den Rechtsstreit zwischen dem Gräflich-Limburgischen Allodialerben und den von ... betreffend by :
Download or read book Fernere Bekräftigung der nöthigen Beilage und gründliche Erinnerungen zu dem ersten Abschnitt des 5. Bandes der teutschen Staatskanzlei des Herrn Dr. Reuss, vom Jahrgang 1799, den Rechtsstreit zwischen dem Gräflich-Limburgischen Allodialerben und den von ... betreffend written by and published by . This book was released on 1802 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis CURRENT DRIVE AND PRESSURE PROFILE MODIFICATION WITH ELECTRON CYCLOTRON POWER IN DIII-D QUIESCENT DOUBLE BARRIER EXPERIMENTS. by :
Download or read book CURRENT DRIVE AND PRESSURE PROFILE MODIFICATION WITH ELECTRON CYCLOTRON POWER IN DIII-D QUIESCENT DOUBLE BARRIER EXPERIMENTS. written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: OAK-B135 High confinement mode (H-mode) operation is a leading scenario for burning plasma devices due to its inherently high energy-confinement characteristics. The quiescent H-mode (QH-mode) offers these same advantages with the additional attraction of more steady edge conditions where the highly transient power loads due to edge localized mode (ELM) activity is replaced by the steadier power and particle losses associated with an edge harmonic oscillation (EHO). With the addition of an internal transport barrier (ITB), the capability is introduced for independent control of both the edge conditions and the core confinement region giving potential control of fusion power production for an advanced tokamak configuration. The quiescent double barrier (QDB) conditions explored in DIII-D experiments exhibit these characteristics and have resulted in steady plasma conditions for several confinement times ([approx] 26[tau][sub E]) with moderately high stored energy, [beta][sub N]H[sub 89][approx] 7 for 10[tau][sub E].
Book Synopsis Core and Edge Aspects of Quiescent Double Barrier Operation on DIII-D. WITH Relevance to Critical Itb Physics Issues by :
Download or read book Core and Edge Aspects of Quiescent Double Barrier Operation on DIII-D. WITH Relevance to Critical Itb Physics Issues written by and published by . This book was released on 2003 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: OAK-B135 Recent results from DIII-D address critical internal transport barrier (ITB) research issues relating to sustainability, impurity accumulation and ITB control, and have also demonstrated successful application of general profile control tools. In addition, substantial progress has been made in understanding the physics of the Quiescent Double Barrier (QDB) regime, increasing the demonstrating operating space for the regime and improving performance. Highlights include: (1) a clear demonstration of q-profile modification using electron cyclotron current drive (ECCD); (2) successful use of localized profile control using electron cyclotron heating (ECH) or ECCD to reduce central high-Z impurity accumulation associated with density peaking; (3) theory-based modeling codes are now being used to design experiments; (4) the operating space for Quiescent H-mode (QH-mode) has been substantially broadened, in particular higher density operation has been achieved; (5) absolute ([beta] 3.8%, neutron rate S{sub n} d"5.5 x 1015 s−1) and relative ([beta]{sub N}H9 = 7 for 10 [tau]{sub E}) performance has been increased; (6) with regard to sustainment, QDB plasmas have been run for 3.8 s or 26 [tau]{sub E}. These results emphasize that it is possible to produce sustained high quality H-mode performance with an edge localized mode (ELM)-free edge, directly addressing a major issue in fusion research, of how to ameliorate or eliminate ELM induced pulsed divertor particle and heat loads.
Book Synopsis 108-1 Hearings: Energy and Water Development Appropriations For 2004, Part 4, 2003, * by :
Download or read book 108-1 Hearings: Energy and Water Development Appropriations For 2004, Part 4, 2003, * written by and published by . This book was released on 2003 with total page 3122 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Energy and Water Development Appropriations For 2006, Part 4B, 109-1 Hearings, *. by :
Download or read book Energy and Water Development Appropriations For 2006, Part 4B, 109-1 Hearings, *. written by and published by . This book was released on 2005 with total page 1444 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :United States. Congress. House. Committee on Appropriations. Subcommittee on Energy and Water Development Publisher : ISBN 13 : Total Pages :1440 pages Book Rating :4.3/5 ( download)
Book Synopsis Energy and water development appropriations for 2005 by : United States. Congress. House. Committee on Appropriations. Subcommittee on Energy and Water Development
Download or read book Energy and water development appropriations for 2005 written by United States. Congress. House. Committee on Appropriations. Subcommittee on Energy and Water Development and published by . This book was released on 2004 with total page 1440 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :United States. Congress. House. Committee on Appropriations. Subcommittee on Energy and Water Development Publisher : ISBN 13 : Total Pages :3132 pages Book Rating :4.:/5 (8 download)
Book Synopsis Energy and Water Development Appropriations for 2004 by : United States. Congress. House. Committee on Appropriations. Subcommittee on Energy and Water Development
Download or read book Energy and Water Development Appropriations for 2004 written by United States. Congress. House. Committee on Appropriations. Subcommittee on Energy and Water Development and published by . This book was released on 2003 with total page 3132 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis QUIESCENT H-MODE, AN ELM-FREE HIGH-CONFINEMENT MODE ON DIII-D WITH POTENTIAL FOR STATIONARY STATE OPERATION. by : L. ZENG
Download or read book QUIESCENT H-MODE, AN ELM-FREE HIGH-CONFINEMENT MODE ON DIII-D WITH POTENTIAL FOR STATIONARY STATE OPERATION. written by L. ZENG and published by . This book was released on 2003 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: OAK-B135 The quiescent H-mode (QH-mode) is an ELM-free and stationary state mode of operation discovered on DIII-D. This mode achieves H-mode levels of confinement and pedestal pressure while maintaining constant density and radiated power. The elimination of edge localized modes (ELMs) and their large divertor loads while maintaining good confinement and good density control is of interest to next generation tokamaks. This paper reports on the correlations found between selected parameters in a QH-mode database developed from several hundred DIII-D counter injected discharges. Time traces of key plasma parameters from a QH-mode discharge are shown. On DIII-D the negative going plasma current (a) indicates that the beam injection direction is counter to the plasma current direction, a common feature of all QH-modes. The D{sub {alpha}} time behavior (c) shows that soon after high powered beam heating (b) is applied, the discharge makes a transition to ELMing H-mode, then the ELMs disappear, indicating the start of the QH period that lasts for the remainder of the high power beam heating (3.5 s). Previously published work showing density and temperature profiles indicates that long-pulse, high-triangularity QH discharges develop an internal transport barrier in combination with the QH edge barrier. These discharges are known as quiescent, double-barrier discharges (QDB). The H-factor (d) and stored energy (c) rise then saturate at a constant level and the measured axial and minimum safety factors remain above 1.0 for the entire QH duration. During QDB operation the performance of the plasma can be very good, with {beta}{sub N}*H{sub 89L} product reaching 7 for> 10 energy confinement times. These discharges show promise that a stationary state can be achieved.
Book Synopsis QUIESCENT H-MODE, AN ELM-FREE HIGH-CONFINEMENT MODE ON DIII-D WITH POTENTIAL FOR STATIONARY STATE OPERATION. by :
Download or read book QUIESCENT H-MODE, AN ELM-FREE HIGH-CONFINEMENT MODE ON DIII-D WITH POTENTIAL FOR STATIONARY STATE OPERATION. written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: OAK-B135 The quiescent H-mode (QH-mode) is an ELM-free and stationary state mode of operation discovered on DIII-D. This mode achieves H-mode levels of confinement and pedestal pressure while maintaining constant density and radiated power. The elimination of edge localized modes (ELMs) and their large divertor loads while maintaining good confinement and good density control is of interest to next generation tokamaks. This paper reports on the correlations found between selected parameters in a QH-mode database developed from several hundred DIII-D counter injected discharges. Time traces of key plasma parameters from a QH-mode discharge are shown. On DIII-D the negative going plasma current (a) indicates that the beam injection direction is counter to the plasma current direction, a common feature of all QH-modes. The D[sub[alpha]] time behavior (c) shows that soon after high powered beam heating (b) is applied, the discharge makes a transition to ELMing H-mode, then the ELMs disappear, indicating the start of the QH period that lasts for the remainder of the high power beam heating (3.5 s). Previously published work showing density and temperature profiles indicates that long-pulse, high-triangularity QH discharges develop an internal transport barrier in combination with the QH edge barrier. These discharges are known as quiescent, double-barrier discharges (QDB). The H-factor (d) and stored energy (c) rise then saturate at a constant level and the measured axial and minimum safety factors remain above 1.0 for the entire QH duration. During QDB operation the performance of the plasma can be very good, with[beta][sub N]*H[sub 89L] product reaching 7 for> 10 energy confinement times. These discharges show promise that a stationary state can be achieved.
Book Synopsis Density and Temperature Profile Modifications with Electron Cyclotron Power Injection in Quiescent Double Barrier Discharges on DIII-D. by : D. M. Thomas
Download or read book Density and Temperature Profile Modifications with Electron Cyclotron Power Injection in Quiescent Double Barrier Discharges on DIII-D. written by D. M. Thomas and published by . This book was released on 2005 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quiescent double barrier (QDB) conditions often form when an internal transport barrier is created with high-power neutral-beam injection into a quiescent H-mode (QH) plasma. These QH-modes offer an attractive, high-performance operating scenario for burning plasma experiments due to their quasi-stationarity and lack of edge localized modes (ELMs). Our initial experiments and modeling using ECH/ECCD in QDB shots were designed to control the current profile and, indeed, we have observed a strong dependence on the q-profile when EC-power is used inside the core transport barrier region. While strong electron heating is observed with EC power injection, we also observe a drop in the other core parameters; ion temperature and rotation, electron density and impurity concentration. These dynamically changing conditions provide a rapid evolution of T{sub e} T{sub i} profiles accessible with 0.3
Book Synopsis New Amplifications of the North American Piperaceae by : William Trelease
Download or read book New Amplifications of the North American Piperaceae written by William Trelease and published by . This book was released on 1934 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Operational Enhancements in DIII-D Quiescent H-Mode Plasmas by : D. M. Thomas
Download or read book Operational Enhancements in DIII-D Quiescent H-Mode Plasmas written by D. M. Thomas and published by . This book was released on 2005 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent DIII-D experiments, we concentrated on extending the operating range and improving the overall performance of quiescent H-mode (QH) plasmas. The QH-mode offers an attractive, high-performance operating mode for burning plasmas due to the absence of pulsed edge-localized-mode-driven losses to the divertor (ELMs). Using counter neutral-beam injection (NBI), we achieve steady plasma conditions with the presence of an edge harmonic oscillation (EHO) replacing the ELMs and providing control of the edge pedestal density. These conditions have been maintained for greater than 4s ({approx}30 energy confinement times, {tau}{sub E}, and 2 current relaxation times, {tau}{sub R} [1]), and often limited only by the duration of auxiliary heating. We discuss results of these recent experiments where we use triangularity ramping to increase the density, neutral beam power ramps to increase the stored energy, injection of rf power at the electron cyclotron (EC) frequency to control density profile peaking in the core, and control of startup conditions to completely eliminate the transient ELMing phase.
Book Synopsis DIII-D Experimental Plan for FY-1989 by :
Download or read book DIII-D Experimental Plan for FY-1989 written by and published by . This book was released on 1988 with total page 27 pages. Available in PDF, EPUB and Kindle. Book excerpt: This document summarizes the Experimental Plan for the DIII-D tokamak facility for the fiscal year 1989. The long-range DIII-D 5 yr plan is directed ultimately at the goal of achieving good confinement at high beta in a plasma with non-inductively driven current. This is important to the design of a steady-state reactor. This program may be thought of as occurring in two phases. In the first phase of the program we axe separately investigating high beta plasma confinement in inductively-driven plasmas, and non-inductive current drive. In the second phase we will combine these two elements to investigate high beta plasma confinement with non-inductive current drive. The FY 89 plan continues the first phase of the DIII-D experimental effort that contains a strong focus on beta and confinement in non-circular plasma configurations and in the divertor configuration in particular. Important work also continues in the development of rf heating systems for heating, profile control, and current drive. This research is coupled to theoretical efforts at General Atomics. The FY 89 research program outlined herein is diverse and multifaceted. However, it is also characterized by a greater synthesis of techniques toward a common goal. An example is the application of ECH for sawtooth suppression that would improve the low q confinement and allow higher [beta] to be obtained. We believe this research program will provide a solid foundation for the continued development of the tokamak toward high beta steady-state reactor application. The DIII-D FY 89 research program will provide results that will help resolve many CIT and ITER Physics R & D issues. In addition, DIII-D confinement studies will be an important input to the newly formed National Transport Task Force.
Book Synopsis Comprehensive Measurements and Modeling of SOL, and Core Plasma Fueling and Carbon Sources in DIII-D. by : J. Watkins
Download or read book Comprehensive Measurements and Modeling of SOL, and Core Plasma Fueling and Carbon Sources in DIII-D. written by J. Watkins and published by . This book was released on 2005 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: Plasma boundary modeling of low density, low confinement plasmas in DIII-D has been benchmarked against a comprehensive set of measurements and indicates that recycling of deuterium ions at the divertor targets, and chemical sputtering at the divertor target plates and walls, can explain the poloidal core fueling profile and core carbon density. Key measurements included the 2-D intensity distribution of deuterium neutral and low-charge state carbon emission in the divertor and around the midplane of the high-field scrape-off layer (SOL). Chemical sputtering plays an important role in producing carbon at the divertor targets and walls, and was found to be a prerequisite to reproduce the measured emission distribution.
