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Author : Martin Greenwald
Publisher :
ISBN 13 :
Total Pages : 9 pages
Book Rating : 4.:/5 (441 download)
Download or read book Studies of EDA H-mode in Alcator C-Mod written by Martin Greenwald and published by . This book was released on 1999 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Earl S. Marmar
Publisher :
ISBN 13 :
Total Pages : 6 pages
Book Rating : 4.:/5 (65 download)
Download or read book Enhanced D-Alpha H-mode Studies in the Alcator C-Mod Tokamak written by Earl S. Marmar and published by . This book was released on 2000 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: A favorable regime of H-mode confinement, seen on the Alcator C-Mod tokamak is described. Following a brief period of ELM-free H-mode, the plasma evolves into the Enhanced D-Alpha (EDA) H-mode which is characterized by very good energy confinement, the complete absence of large, intermittent type I ELMs, finite impurity and majority species confinement, and low radiated power fraction. Accompanying the EDA H-mode, a quasi-coherent (QC) edge mode is observed, and found to be responsible for particle transport through the edge confinement barrier. The QC-mode is localized within the strong density gradient region, and has poloidal wavenumber and lab-frame frequency of 100 kHz. Parametric studies show that the conditions which promote EDA include moderate safety factor, high triangularity (d>0.35) and high target density (ne>1.2x20 m-3). EDA H-mode is readily obtained in purely ohmic and well as in ICRF auxiliary-heated discharges.
Author : Martin Greenwald
Publisher :
ISBN 13 :
Total Pages : 39 pages
Book Rating : 4.:/5 (361 download)
Download or read book H Mode Confinement in Alcator C-Mod written by Martin Greenwald and published by . This book was released on 1996 with total page 39 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Amanda E. Hubbard
Publisher :
ISBN 13 :
Total Pages : 16 pages
Book Rating : 4.:/5 (641 download)
Download or read book Comparisons of Small Edge Localized Mode H-Mode Regimes on the Alcator C-Mod and JFT-2M Tokamaks written by Amanda E. Hubbard and published by . This book was released on 2005 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: Comparisons of H-mode regimes were carried out on the Alcator C-Mod and JFT-2M tokamaks. Shapes were matched apart from aspect ratio, which is lower on C-Mod. The High Recycling Steady (HRS) H-mode on JFT-2M and Enhanced D-alpha (EDA) regime on C-Mod, which both feature very small or no ELMs, are found to have similar access conditions in q95-nu* space, occurring for pedestal collisionality nu* greater than 1. Differences in edge fluctuations were found, with lower frequencies but higher mode numbers on C-Mod. In both tokamaks an attractive regime with small ELMs on top of an enhanced D-alpha baseline was obtained at moderate nu* and higher pressure. The JFT-2M shape favoured the appearance of ELMs on C-Mod, and also resulted in the appearance of a lower frequency component of the quasicoherent mode during EDA.
Author : Dmitri A. Mossessian
Publisher :
ISBN 13 :
Total Pages : 32 pages
Book Rating : 4.:/5 (66 download)
Download or read book H-mode Pedestal Characteristics and MHD Stability of the Edge Plasma in Alcator C-Mod written by Dmitri A. Mossessian and published by . This book was released on 2002 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt: Under most operational conditions of Alcator C-Mod the dominant type of H-mode is the steady state enhanced Da mode (EDA), characterized by good energy confinement, continuously degraded impurity confinement and absence of regular ELMs. In this regime a quasicoherent (QC) electromagnetic mode ... is observed, localized in the region of the density pedestal. Experimental evidence suggests that the mode is responsible for enhancement of particle transport. It is shown experimentally that the QC mode can exist in a well defined region in edge temperature-safety factor space, favoring high edge q values ... and requiring moderate pedestal temperatureTeped ... As edge temperature and pressure gradient increase, the quasicoherent mode is replaced by broadband low frequency fluctuations (f
Author : Joseph Allan Snipes
Publisher :
ISBN 13 :
Total Pages : 10 pages
Book Rating : 4.:/5 (65 download)
Download or read book The Quasi-coherent Signature of Enhanced D Alpha H-mode in Alcator C-Mod written by Joseph Allan Snipes and published by . This book was released on 2001 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: The steady-state H-mode regime found at moderate to high density in Alcator C-Mod, known as Enhanced D alpha H-mode (EDA), appears to be maintained by a continuous quasi-coherent (QC) mode in the edge steep gradient region. Large amplitude density and magnetic fluctuations with typical frequencies of %7E100 kHz are driven by the QC mode. These fluctuations are measured in the steep edge gradient region by inserting a fast scanning probe containing two poloidally separated Langmuir probes and a poloidal field pick-up coil. As the probe approaches the plasma edge, clear magnetic fluctuations were measured within %7E 2 cm of the last closed flux surface (LCFS). The mode amplitude falls off rapidly with distance from the plasma center with an exponential decay length of kr approximately equal to 1.5 cm-1, measured 10 cm above the outboard midplane. The root-mean-square amplitude of the poloidal field fluctuation extrapolated to the LCFS was approximately 5 G. The density fluctuations, on the other hand, were visible on the Langmuir probe only when it was within a few mm of the LCFS. The potential and density fluctuations were sufficiently in phase to enhance particle transport at the QC mode frequency. These results show that the quasi-coherent signature of the EDA H-mode is an electromagnetic mode that appears to be responsible for the enhanced particle transport in the plasma edge.
Author : Dmitri A. Mossessian
Publisher :
ISBN 13 :
Total Pages : 34 pages
Book Rating : 4.:/5 (52 download)
Download or read book H-mode Edge Stability of Alcator C-mod Plasmas written by Dmitri A. Mossessian and published by . This book was released on 2002 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: For steady state H-mode operation, a relaxation mechanism is required to limit build-up of the edge gradient and impurity content. C-Mod sees two such mechanisms - EDA and grassy ELMs, but not large type I ELMs. In EDA the edge relaxation is provided by an edge localized quasicoherent electromagnetic mode that exists at moderate pedestal temperature T400 eV, high pedestal density and high edge safety factor ...3.5, and does not limit the build up of the edge pressure gradient. The q boundary of the operational space of the mode depends on plasma shape, with the q95 limit moving down with increasing plasma triangularity. At high edge pressure gradients and temperatures the mode is replaced by broadband fluctuations (f
Author :
Publisher : ScholarlyEditions
ISBN 13 : 1490107819
Total Pages : 1198 pages
Book Rating : 4.4/5 (91 download)
Download or read book Issues in Nuclear, High Energy, Plasma, Particle, and Condensed Matter Physics: 2013 Edition written by and published by ScholarlyEditions. This book was released on 2013-05-01 with total page 1198 pages. Available in PDF, EPUB and Kindle. Book excerpt: Issues in Nuclear, High Energy, Plasma, Particle, and Condensed Matter Physics: 2013 Edition is a ScholarlyEditions™ book that delivers timely, authoritative, and comprehensive information about High Energy Physics. The editors have built Issues in Nuclear, High Energy, Plasma, Particle, and Condensed Matter Physics: 2013 Edition on the vast information databases of ScholarlyNews.™ You can expect the information about High Energy Physics in this book to be deeper than what you can access anywhere else, as well as consistently reliable, authoritative, informed, and relevant. The content of Issues in Nuclear, High Energy, Plasma, Particle, and Condensed Matter Physics: 2013 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 :
Publisher :
ISBN 13 :
Total Pages : 512 pages
Book Rating : 4.:/5 (318 download)
Download or read book Fusion Science and Technology written by and published by . This book was released on 2008 with total page 512 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : John Wesson
Publisher : Oxford University Press
ISBN 13 : 0199592233
Total Pages : 828 pages
Book Rating : 4.1/5 (995 download)
Download or read book Tokamaks written by John Wesson and published by Oxford University Press. This book was released on 2011-10-13 with total page 828 pages. Available in PDF, EPUB and Kindle. Book excerpt: The tokamak is the principal tool in controlled fusion research. This book acts as an introduction to the subject and a basic reference for theory, definitions, equations, and experimental results. The fourth edition has been completely revised, describing their development of tokamaks to the point of producing significant fusion power.
Author : J. W. Hughes
Publisher :
ISBN 13 :
Total Pages : 50 pages
Book Rating : 4.:/5 (66 download)
Download or read book Observations and Empirical Scalings of the High-confinement Mode Pedestal on Alcator C-Mod written by J. W. Hughes and published by . This book was released on 2002 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt: On the Alcator C-Mod tokamak [Phys. Plasmas 1, 1511, (1994)], radial profiles of electron temperature (Te) and density (ne) are measured at the plasma edge with millimeter resolution Thomson scattering [Rev. Sci. Instrum. 72, 1107 (2001)]. Edge transport barriers in the high confinement regime (H-mode) exhibit Te, ne pedestals with typical widths of 2-6 mm, with the Te pedestal on average slightly wider than and inside the ne pedestal. Measurements at both the top and the base of the pedestal are consistent with profiles obtained using other diagnostics. The two primary H-mode regimes on C-Mod, enhanced Da (EDA) and edge-localized mode free (ELM-free), have been examined for differences in pedestals. EDA operation is favored by high edge collisionality n*, in addition to high edge safety factor q95. Scaling studies at fixed shape yield little systematic variation of pedestal widths with plasma parameters, though higher triangularity is seen to increase the ne pedestal width dramatically. Pedestal heights and gradients show the clearest dependencies on plasma control parameters. Pedestal ne and Te both scale linearly with plasma current IP, while pedestal Te depends strongly on power flowing from the core plasma into the scrape-off layer PSOL. The electron pressure (pe) pedestal and pe gradient both scale with IP2 PSOL1/2. Plasma stored energy WP scales with pedestal pe, implying that pedestal scalings may in large part determine global confinement scalings.
Author : Alexandre Parisot
Publisher :
ISBN 13 :
Total Pages : 26 pages
Book Rating : 4.:/5 (642 download)
Download or read book Ion Cyclotron Range of Frequencies Loading Studies on Alcator C-Mod written by Alexandre Parisot and published by . This book was released on 2004 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: Rapid changes in the loading resistance of fast wave antennas can limit high power operations of heating systems in the Ion Cyclotron Range of Frequencies (ICRF). Although novel matching techniques are being developed to reduce their effects, understanding the physics involved in these variations is of interest to guide and facilitate the design effort. We have studied the dependence of the loading resistance upon plasma parameters for the three ICRF antennas in the Alcator C-Mod tokamak. In contrast with similar studies in JET and Tore Supra, the evanescent decay term was not found to play an important role. The dominant variations could be related to changes in the shape of the electron density profiles in the propagating region. In H-mode, the loading resistance decreases as the density at the top of the pedestal is increased, and increases for higher Scrape-Off Layer densities. This dependency on global plasma parameters is generally identical for the three antennas, up to a proportionality constant, while local changes in front of an individual antennas could explain the residual discrepancy. To link the observations with theory, the surface impedance at the Faraday shield was calculated by solving the wave equation in a slab geometry using experimental radial density profiles. This approach leads to a good agreement with measurements over a wide range of operating conditions in L-mode, ELM-free and EDA H-mode plasmas, and it can be interpreted qualitatively in terms of impedance transformation in the scrape-off layer region. Implications for more complex modeling approaches are also discussed.
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Author : Nils Plesner Basse
Publisher :
ISBN 13 :
Total Pages : 96 pages
Book Rating : 4.:/5 (615 download)
Download or read book Characterization of Core and Edge Turbulence in L- and Enhanced D[alpha] H-mode Alcator C-Mod Plasmas written by Nils Plesner Basse and published by . This book was released on 2005 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt: The recently upgraded phase-contrast imaging (PCI) diagnostic is used to characterize the transition from the low (L) to the enhanced D[alpha] (EDA) high (H) confinement mode in Alcator C-Mod [I. H. Hutchinson, et al., Phys. Plasmas, 1511 (1994)] plasmas. PCI yields information on line integrated density fluctuations along vertical chords. The number of channels has been increased from 12 to 32, the sampling rate from 1 MHz to 10 MHz. This expansion of diagnostic capabilities is used to study broadband turbulence in L- and EDA H-mode and to analyze the quasi-coherent (QC) mode associated with EDA H-mode. Changes in broadband turbulence at the transition from L- to EDA H-mode can be interpreted as an effect of the Doppler rotation of the bulk plasma. Additional fluctuation measurements of D[alpha]-light and the poloidal magnetic field show features correlated with PCI in two different frequency ranges at the transition. The back transition from EDA H- to L-mode, the so-called enhanced neutron (EN) mode, is investigated by new high frequency (132 and 140 GHz) reflectometer channels operating in the ordinary (O) mode. This additional hardware has been installed in an effort to study localized turbulence associated with internal transport barriers (ITBs). The EN-mode is a suitable candidate for this study, since an ITB exists transiently as the outer density decreases much faster than the core density in this mode. The fact that the density decays from the outside inward allows us to study fluctuations progressing towards the plasma core. Our results mark the first localized observation of the QC-mode at medium density: 2.2 x 1020 m-3 (132 GHz). Correlating the reflectometry measurements with other fluctuating quantities provides some insight regarding the causality of the EN-mode development.
Author : Jerry Wayne Hughes
Publisher :
ISBN 13 :
Total Pages : 452 pages
Book Rating : 4.:/5 (641 download)
Download or read book Edge Transport Barrier Studies on the Alcator C-Mod Tokamak written by Jerry Wayne Hughes and published by . This book was released on 2005 with total page 452 pages. Available in PDF, EPUB and Kindle. Book excerpt: Edge transport barriers (ETBs) in tokamak plasmas accompany transitions from low confinement (L-mode) to high confinement (H-mode) and exhibit large density and temperature gradients in a narrow pedestal region near the last closed flux surface (LCFS). Because tokamak energy confinement depends strongly on the boundary condition imposed by the edge plasma pressure, one desires a predictive capability for the pedestal on a future tokamak. On Alcator C-Mod, significant contributions to ETB studies were made possible with edge Thomson scattering (ETS), which measures profiles of electron temperature (20 [leq] Te[eV] [leq] 800) and density (0.3 [leq] ne[10^20m^-3] [leq] 5) with 1.3-mm spatial resolution near the LCFS. Profiles of Te, ne, and pe = neTe are fitted with a parameterized function, revealing typical pedestal widths [delta] of 2-6mm, with [delta]Te [geq] [delta]ne , on average. Pedestals are examined to determine existence criteria for the enhanced D[alpha] (EDA) H-mode. A feature that distinguishes this regime is a quasi-coherent mode (QCM) near the LCFS. The presence or absence of the QCM is related to edge conditions, in particular density, temperature and safety factor q. Results are consistent with higher values of both q and collisionality [nu]* giving the EDA regime. Further evidence suggests that increased abs([nabla]pe) may favor the QCM; thus EDA may have relevance to low-[nu]* reactor regimes, should sufficient edge pressure gradient exist.
Author : Frederick B. Marcus
Publisher : Springer Nature
ISBN 13 : 3031177118
Total Pages : 484 pages
Book Rating : 4.0/5 (311 download)
Download or read book Systems Approaches to Nuclear Fusion Reactors written by Frederick B. Marcus and published by Springer Nature. This book was released on 2023-01-01 with total page 484 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book offers an overall review, applying systems engineering and architecture approaches, of the design, optimization, operation and results of leading fusion experiments. These approaches provide a unified means of evaluating reactor design. Methodologies are developed for more coherent construction or evaluation of fusion devices, associated experiments and operating procedures. The main focus is on tokamaks, with almost all machines and their important results being integrated into a systems design space. Case studies focus on DIII-D, TCV, JET, WEST, the fusion reactor prototype ITER and the EU DEMO concept. Stellarator, Mirror and Laser inertial confinement experiments are similarly analysed, including reactor implications of breakeven at NIF. The book examines the engineering and physics design and optimization process for each machine, analysing their performance and major results achieved, thus establishing a basis for the improvement of future machines. The reader will gain a broad historical and up-to-date perspective of the status of nuclear fusion research from both an engineering and physics point of view. Explanations are given of the computational tools needed to design and operate successful experiments and reactor-relevant machines. This book is aimed at both graduate students and practitioners of nuclear fusion science and engineering, as well as those specializing in other fields demanding large and integrated experimental equipment. Systems engineers will obtain valuable insights into fusion applications. References are given to associated complex mathematical derivations, which are beyond the scope of this book. The general reader interested in nuclear fusion will find here an accessible summary of the current state of nuclear fusion.
Author : Catherine L. Fiore
Publisher :
ISBN 13 :
Total Pages : 58 pages
Book Rating : 4.:/5 (569 download)
Download or read book Control of Internal Transport Barriers on Alcator C-Mod written by Catherine L. Fiore and published by . This book was released on 2003 with total page 58 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent studies of internal transport and double transport barrier regimes in Alcator C-Mod [I.H. Hutchinson, et al., Phys. Plasmas 1, 1511 (1994)] have explored the limits for forming, maintaining, and controlling these plasmas. C-Mod provides a unique platform for studying such discharges: the ions and electrons are tightly coupled by collisions and the plasma has no internal particle or momentum sources. The double-barrier mode comprised of an edge barrier with an internal transport barrier (ITB) can be induced at will using off-axis ion cyclotron range of frequency (ICRF) injection on either the low or high field side of the plasma with either of the available ICRF frequencies (70 or 80 MHz). When enhanced D [alpha] high confinement mode (EDA H-mode) is accessed in Ohmic plasmas, the double barrier ITB forms spontaneously if the Hmode is sustained for [approx.] high confinement times. The ITBs formed in both Ohmic and ICRF heated plasmas are quite similar regardless of the trigger method. They are characterized by strong central peaking of the electron density, and reduction of the core particle and energy ...
Author : George Neilson
Publisher : Woodhead Publishing
ISBN 13 : 0081003269
Total Pages : 634 pages
Book Rating : 4.0/5 (81 download)
Download or read book Magnetic Fusion Energy written by George Neilson and published by Woodhead Publishing. This book was released on 2016-06-02 with total page 634 pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnetic Fusion Energy: From Experiments to Power Plants is a timely exploration of the field, giving readers an understanding of the experiments that brought us to the threshold of the ITER era, as well as the physics and technology research needed to take us beyond ITER to commercial fusion power plants. With the start of ITER construction, the world’s magnetic fusion energy (MFE) enterprise has begun a new era. The ITER scientific and technical (S&T) basis is the result of research on many fusion plasma physics experiments over a period of decades. Besides ITER, the scope of fusion research must be broadened to create the S&T basis for practical fusion power plants, systems that will continuously convert the energy released from a burning plasma to usable electricity, operating for years with only occasional interruptions for scheduled maintenance. Provides researchers in academia and industry with an authoritative overview of the significant fusion energy experiments Considers the pathway towards future development of magnetic fusion energy power plants Contains experts contributions from editors and others who are well known in the field
