Author: Yusuke Kosuga
Publisher:
ISBN: 9781267401243
Category :
Languages : en
Pages : 134
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Book Description
Aspects of the macroscopic phenomenology of tokamak plasmas - relaxation, transport, and flow generation - are analyzed in the context of phase space dynamics. Particular problems of interest are: i) fluctuation entropy evolution with turbulence driven flows and its application to flow generation by heat flux driven turbulence, and ii) dynamical coupling between phase space structures and zonal flows and its implication for macroscopic relaxation and transport. In chapter 2, intrinsic toroidal rotation drive by heat flux driven turbulence in tokamak is analyzed based on phase space dynamics. In particular, the dynamics of fluctuation entropy with turbulence driven flows is formulated. The entropy budget is utilized to quantify tokamaks as a heat engine system, where heat flux is converted to macroscopic flows. Efficiency of the flow generation process is defined as the ratio of entropy destruction via flow generation to entropy production via heat input. Comparison of the results to experimental scaling is discussed as well. In chapter 3, dynamics of a single phase space structure (drift hole) is discussed for a strongly magnetized 3D plasma. The drift hole is shown to be dynamically coupled to zonal flows by polarization charge scattering. The coupled dynamics of the drift hole and zonal flow is formulated based on momentum budget. As an application, a bound on the self-bound drift hole potential amplitude is derived. The results show that zonal flow damping appears as a controlling parameter. In chapter 4, dynamics of both a single structure and multi-structures in phase space are discussed for a relevant system, i.e. trapped ion driven ion temperature gradient turbulence. The structures are dynamically coupled to zonal flows, since they must scatter polarization charge to satisfy the quasi-neutrality. The coupled evolution of the structures and flows is formulated as a momentum theorem. An implication for transport process is discussed as well. The transport flux is prescribed by dynamical friction exerted by structures on flows. The dynamical friction exerted by zonal flow is a novel effect and reduces transport by algebraically competing against other fluxes, such as a quasilinear diffusive flux.
Author: Julien Medina
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
One of the most promising approach to controlled nuclear fusion is the tokamak. It is a toroidal machine confining a fusion plasma using magnetic fields. Transport of particles and heat, from the core toward the edges happens spontaneously, degrades the efficiency of the tokamak, and is driven by turbulence. We use a bounce-averaged 4D gyrokinetic code which solves the Vlasov-Quasi-neutrality system. The code is based on a reduced model which averages out the cyclotron and the bounce motion of the trapped particles to reduce the dimensionality. In this work we developed and tested a new module for the code, allowing to track test particle trajectories in phase space. As a first result obtained with test particles, we achieved to separate the diffusive contribution to the radial particle flux in energy space, from the non-diffusive contributions. Both fluxes present an intense peak indicating resonant particles dominate transport. On short period of time the test particles undergo a small scale advection, but on longer times, they follow a random walk process. We then explored with greater accuracy the fluxes in energy space. Furthermore we compared the obtained fluxes with quasi-linear predictions and found a qualitative agreement, although there was a ~50% discrepancy in the peak magnitude.
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 652
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Book Description
Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Author:
Publisher:
ISBN:
Category : Controlled fusion
Languages : en
Pages : 310
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Book Description
Author:
Publisher: Allied Publishers
ISBN: 9788170237112
Category : Laser plasma
Languages : en
Pages : 500
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Book Description
Author:
Publisher:
ISBN:
Category : Power resources
Languages : en
Pages : 582
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Book Description
Author:
Publisher:
ISBN:
Category : Physics
Languages : en
Pages : 1212
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Book Description
Author:
Publisher:
ISBN:
Category : Nuclear energy
Languages : en
Pages : 938
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Book Description
Author: United States. National Aeronautics and Space Administration. Scientific and Technical Information Branch
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 1080
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Book Description
Author: Tjerk P. Straatsma
Publisher: CRC Press
ISBN: 1351999249
Category : Computers
Languages : en
Pages : 607
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Book Description
Describes practical programming approaches for scientific applications on exascale computer systems Presents strategies to make applications performance portable Provides specific solutions employed in current application porting and development Illustrates domain science software development strategies based on projected trends in supercomputing technology and architectures Includes contributions from leading experts involved in the development and porting of scientific codes for current and future high performance computing resources
