Author: Publisher:
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Category :
Languages : en
Pages : 11
Book Description
Development of a Tokamak Plasma Optimized for Stability and Confinement
Author: Optimized Profiles for Improved Confinement and Stability in the DIII-D Tokamak
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 11
Book Description
Simultaneous achievement of high energy confinement, [tau]{sub E}, and high plasma beta, [beta], leads to an economically attractive compact tokamak fusion reactor. High confinement enhancement, H = [tau]{sub E}/[tau]{sub E-ITER89P} = 4, and high normalized beta [beta]{sub N} = [beta]/(I/aB) = 6%-m-T/MA, have been obtained in DIII-D experimental discharges. These improved confinement and/or improved stability limits are observed in several DIII-D high performance operational regimes: VH-mode, high l{sub i} H-mode, second stable core, and high beta poloidal. The authors have identified several important features of the improved performance in these discharges: details of the plasma shape, toroidal rotation or ExB flow profile, q profile and current density profile, and pressure profile. From the improved physics understanding of these enhanced performance regimes, they have developed operational scenarios which maintain the essential features of the improved confinement and which increase the stability limits using localized current profile control. The stability limit is increased by modifying the interior safety factor profile to be nonmonotonic with high central q, while maintaining the edge current density consistent with the improved transport regimes and the high edge bootstrap current. They have calculated high beta equilibria with [beta]{sub N} = 6.5, stable to ideal n = 1 kinks and stable to ideal ballooning modes. The safety factor at the 95% flux surface is 6, the central q value is 3.9 and the minimum in q is 2.6. The current density profile is maintained by the natural profile of the bootstrap current, and a modest amount of electron cyclotron current drive.
Scientific and Technical Aerospace Reports
Author: Plasma Shape Optimization for Steady-State Tokamak Development in DIII-D.
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 7
Book Description
For a more detailed account of the results summarized here and for references, see C.T. Holcomb et al., Phys. Plasmas 16, 056116 (2009). Advanced tokamak research on DIII-D is focused on developing a high fusion gain, steady-state scenario that would eliminate or greatly reduce the demands on an inductive transformer in future machines. Steady-state operation requires the inductively driven current density (j{sub Ind}) be zero everywhere. Most of the total current I{sub p} is typically from self-driven bootstrap current, with the remainder driven by external noninductive sources, such as neutral beam and radiofrequency current drive. This paper describes an extension of the fully noninductive condition (f{sub NI} ≈ 100%) to ≈0.7 current relaxation times that was achieved by a combination of more available ECCD and new scientific insights. The insights are an optimization of performance through variation of the plasma shape parameter known as squareness ([zeta]) and an optimization of divertor magnetic balance. These optimizations simultaneously improve stability, confinement, and density control. These are each essential for achieving fully noninductive operation.
New Ideas in Tokamak Confinement
Author: Marshall N. RosenbluthPublisher: Springer Science & Business Media
ISBN: 9781563961311
Category : Science
Languages : en
Pages : 514
Book Description
Market: Scientists and students involved in thermonuclear fusion research. Thermonuclear fusion research using the confinement device tokamak represents one of the most prominent science projects in the second half of the 20th century. International Tokamak Community is now committing significant effort and funds to experiments with burning plasma, hot and dense enough to produce significant nuclear fusion reactions. The methods used to enhance tokamak performance have a profound and immediate effect on machine design. This book provides an up-to-date account of research in tokamak fusion and puts forward innovative ideas in confinement physics.
Enhancement of Confinement in Tokamaks
Author: Publisher:
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Category :
Languages : en
Pages :
Book Description
A plausible interpretation of the experimental evidence is that energy confinement in tokamaks is governed by two separate considerations: (1) the need for resistive MHD kink-stability, which limits the permissible range of current profiles - and therefore normally also the range of temperature profiles; and (2) the presence of strongly anomalous microscopic energy transport near the plasma edge, which calibrates the amplitude of the global temperature profile, thus determining the energy confinement time tau/sub E/. Correspondingly, there are two main paths towards the enhancement of tokamak confinement: (1) Configurational optimization, to increase the MHD-stable energy content of the plasma core, can evidently be pursued by varying the cross-sectional shape of the plasma and/or finding stable radial profiles with central q-values substantially below unity - but crossing from ''first'' to ''second'' stability within the peak-pressure region would have the greatest ultimate potential. (2) Suppression of edge turbulence, so as to improve the heat insulation in the outer plasma shell, can be pursued by various local stabilizing techniques, such as use of a poloidal divertor. The present confinement model and initial TFTR pellet-injection results suggest that the introduction of a super-high-density region within the plasma core should be particularly valuable for enhancing ntau/subE/. In D-T operation, a centrally peaked plasma pressure profile could possibly lend itself to alpha-particle-driven entry into the second-stability regime.
Advanced Tokamak Stability Theory
Author: Linjin ZhengPublisher: Iop Concise Physics
ISBN: 9781643278698
Category : Science
Languages : en
Pages : 165
Book Description
This book describes the advanced stability theories for magnetically confined fusion plasmas, especially in tokamaks. As the fusion plasma sciences advance, the gap between the textbooks and cutting-edge researches gradually develops. This book fills in
Fusion Technology 1996
Author: C. VarandasPublisher: Elsevier
ISBN: 0444599754
Category : Science
Languages : en
Pages : 1057
Book Description
The objective of these proceedings was to provide a platform for the exchange of information on the design, construction and operation of fusion experiments. The technology which is being developed for the next step devices and fusion reactors was also covered.
Advanced Tokamak Research on the DIII-D Tokamak
Author: Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
The objective of the planned research in advanced tokamak development on DIII-D at General Atomics, San Diego, USA. is to establish improved tokamak operation through significant improvements in the stability factor, confinement quality, and bootstrap current fraction using localized radio frequency (rf) current profile control, rf and neutral beam heating for pressure profile control, as well as control of plasma rotation and optimization of the plasma boundary conditions. Recent research results in H-mode confinement, modifications of current profiles to achieve higher confinement and higher [beta], a new regime of improved confinement (VH-mode), and rf noninductive current drive are encouraging. In this talk, arguments will be presented supporting the need for improved performance in tokamak reactors. Experimentally observed advanced performance regimes on DIII-D will be discussed. Confinement improvement up to H = 4, where H is the ratio of energy confinement time to the ITER89-P scaling H[triple-bond] [Tau][sub E]/[Tau][sub E-ITER89-P], has been achieved. In other discharges [beta][sub N] = [beta]/(I/aB), [%-m[center-dot][Tau]/MA] [approx-gt] 6 has been obtained. These values have so far been achieved transiently and independently. Techniques, will be described which can extend the high performance to quasi-steady-state and sustain the high H and [beta][sub N] values simultaneously. Two high performance regimes, one in first stable regime and the other in second stable regime, have been simulated br self-consistently evolving a magnetohydrodynamic (MHD) equilibrium-transport code. Finally, experimental program plans and outstanding important physics issues will be discussed.
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