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Density And Temperature Profile Modifications With Electron Cyclotron Power Injection In Quiescent Double Barrier Discharges On Diii D
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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 Current Drive and Pressure Profile Modifications with Electron Cyclotron Power in DIII-D Quiescent Double Barrier Experiments by :
Download or read book Current Drive and Pressure Profile Modifications with Electron Cyclotron Power in DIII-D Quiescent Double Barrier Experiments written by and published by . This book was released on 2003 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 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 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 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 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 Den Norske Utstilling i Helsingfors 1911 by :
Download or read book Den Norske Utstilling i Helsingfors 1911 written by and published by . This book was released on 1911 with total page 11 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 :
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 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 Modification of the Current Profile in DIII-D by Off-Axis Electron Cyclotron Current Drive by :
Download or read book Modification of the Current Profile in DIII-D by Off-Axis Electron Cyclotron Current Drive written by and published by . This book was released on 1999 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: Localized non-inductive currents due to electron cyclotron wave absorption have been measured on the DIII-D tokamak. Clear evidence of the non-inductive currents is seen on the internal magnetic field measurements by motional Stark effect spectroscopy. The magnitude and location of the non-inductive current is evaluated by comparing the total and Ohmic current profiles of discharges with and without electron cyclotron wave power. The measured current agrees with Fokker-Planck calculations near the magnetic axis, but exceeds the predicted value as the location of the current drive is moved to the half radius.
Book Synopsis Welcome and Guide to Dunkeld Cathedral by :
Download or read book Welcome and Guide to Dunkeld Cathedral written by and published by . This book was released on 1976 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Nuclear Fusion written by and published by . This book was released on 2003-11 with total page 654 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis FWCD and ECCD Experiments on DIII-D. by :
Download or read book FWCD and ECCD Experiments on DIII-D. written by and published by . This book was released on 1994 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fast wave current drive and electron cyclotron current drive experiments have been performed on the DIII-D tokamak as part of the advanced tokamak program. The goal of this program is to develop techniques for controlling the profile of the current density in order to access regimes of improved confinement and stability. The experiments on fast wave current drive used a four strap antenna with 900 phasing between straps. A decoupler was used to help maintain the phasing, and feedback control of the plasma position was used to keep the resistive loading constant. RF pickup loops demonstrate that the directivity of the antenna is as expected. Plasma currents up to 0.18 MA were driven by 1.5 MW of fast wave power. Electron cyclotron current drive experiments at 60 GHz have shown 0.1 MA of plasma current driven by 1 MW of power. New fast wave and electron cyclotron heating systems are in development for DIII-D, so that the goals of the advanced tokamak program can be carried out.
Book Synopsis Modeling of Electron Cyclotron Current Drive Experiments on DIII-D. by :
Download or read book Modeling of Electron Cyclotron Current Drive Experiments on DIII-D. written by and published by . This book was released on 1999 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Electron Cyclotron Current Drive (ECCD) is considered a leading candidate for current profile control in Advanced Tokamak (AT) operation. Localized ECCD has been clearly demonstrated in recent proof-of-principle experiments on DIII-D. The measured ECCD efficiency near the magnetic axis agrees well with standard theoretical predictions. However, for off-axis current drive the normalized experimental efficiency does not decrease with minor radius as expected from the standard theory; the observed reduction of ECCD efficiency due to trapped electron effects in the off-axis cases is smaller than theoretical predictions. The standard approach of modeling ECCD in tokamaks has been based on the bounce-average calculations, which assume the bounce frequency is much larger than the effective collision frequency for trapped electrons at all energies. The assumption is clearly invalid at low energies. Finite collisionality will effectively reduce the trapped electron fraction, hence, increase current drive efficiency. Here, a velocity-space connection formula is proposed to estimate the collisionality effect on electron cyclotron current drive efficiency. The collisionality correction gives modest improvement in agreement between theoretical and recent DIII-D experimental results.
Book Synopsis Modeling of Trapped Electron Effects on Electron Cyclotron Current Drive for Recent DIII-D Experiments by :
Download or read book Modeling of Trapped Electron Effects on Electron Cyclotron Current Drive for Recent DIII-D Experiments written by and published by . This book was released on 1999 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: Owing to its potential capability of generating localized non-inductive current, especially off-axis, Electron Cyclotron Current Drive (ECCD) is considered a leading candidate for current profile control in achieving Advanced Tokamak (AT) operation. In recent DIII-D proof-of-principle experiments [1], localized off-axis ECCD has been clearly demonstrated for first time. The measured current drive efficiency near the magnetic axis agrees well with predictions of the bounce-averaged Fokker-Planck theory [2,3]. However, the off-axis current drive efficiency was observed to exceed the theoretical results, which predict significant degradation of the current drive efficiency due to trapped electron effects. The theoretical calculations have been based on an assumption that the effective collision frequency is much smaller than the bounce frequency such that the trapped electrons are allowed to complete the banana orbit at all energies. The assumption might be justified in reactor-grade tokamak plasmas, in which the electron temperature is sufficiently high or the velocity of resonant electrons is much larger than the thermal velocity, so that the influence of collisionality on current drive efficiency can be neglected. For off-axis deposition in the present-day experiments, the effect of high density and low temperature is to reduce the current drive efficiency, but the increasing collisionality reduces the trapping of current-carrying electrons, leading to compensating increases in the current drive efficiency. In this work, we use the adjoint function formulation [4] to examine collisionality effects on the current drive efficiency.
Book Synopsis The Franco-American Convention Relative to Double Taxation by : Emmet McCaffery
Download or read book The Franco-American Convention Relative to Double Taxation written by Emmet McCaffery and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
