Comparison of Particle Transport in the Scrapeoff Layer Plasmas of Alcator C-Mod and DIII-D PDF Download
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Author: B. Lipschultz Publisher: ISBN: Category : Languages : en Pages : 50
Book Description
Scrapeoff Layer (SOL) data from DIII--D and C--Mod have been acquired and analyzed for radial particle transport based on a particle balance model. This has allowed a detailed comparison for L--mode plasmas. The inferred radial particle flux, ... , is parameterized in terms of diffusive [ ... ] and convective particle transport [ ... ]. The magnitude of the inferred Deff or veff increases across the SOL for both tokamaks. The inferred Deff or veff in the 'far' SOL (one density e-folding length from the separatrix and beyond) are essentially unchanged by changes in core density by factors of 2-3. This corresponds to changes in the far SOL density, collisionality (v*), and radial fluxes of a factor of 10 or more. Thus v* does not appear to be an important parameter in determining the radial particle transport in that region. The dimensionlessly-scaled SOL plasma profiles from the two tokamaks overlay for similar dimensionless plasma parameters. The SOL density profile near the separatrix is steeper than in the 'far' SOL. The scaled Deff and veff are slightly larger on DIII-D than C-Mod. This difference appears to be within experimental uncertainties. Neutral ionization in the SOL does not appear to affect radial transport but may be related to the observed flattening of the density profiles with increasing ... .
Author: B. Lipschultz Publisher: ISBN: Category : Languages : en Pages : 50
Book Description
Scrapeoff Layer (SOL) data from DIII--D and C--Mod have been acquired and analyzed for radial particle transport based on a particle balance model. This has allowed a detailed comparison for L--mode plasmas. The inferred radial particle flux, ... , is parameterized in terms of diffusive [ ... ] and convective particle transport [ ... ]. The magnitude of the inferred Deff or veff increases across the SOL for both tokamaks. The inferred Deff or veff in the 'far' SOL (one density e-folding length from the separatrix and beyond) are essentially unchanged by changes in core density by factors of 2-3. This corresponds to changes in the far SOL density, collisionality (v*), and radial fluxes of a factor of 10 or more. Thus v* does not appear to be an important parameter in determining the radial particle transport in that region. The dimensionlessly-scaled SOL plasma profiles from the two tokamaks overlay for similar dimensionless plasma parameters. The SOL density profile near the separatrix is steeper than in the 'far' SOL. The scaled Deff and veff are slightly larger on DIII-D than C-Mod. This difference appears to be within experimental uncertainties. Neutral ionization in the SOL does not appear to affect radial transport but may be related to the observed flattening of the density profiles with increasing ... .
Author: C Wendell Horton, Jr Publisher: #N/A ISBN: 9813225904 Category : Science Languages : en Pages : 522
Book Description
For a few seconds with large machines, scientists and engineers have now created the fusion power of the stars in the laboratory and at the same time find the rich range of complex turbulent electromagnetic waves that transport the plasma confinement systems. The turbulent transport mechanisms created in the laboratory are explained in detail in the second edition of 'Turbulent Transport in Magnetized Plasmas' by Professor Horton.The principles and properties of the major plasma confinement machines are explored with basic physics to the extent currently understood. For the observational laws that are not understood — the empirical confinement laws — offering challenges to the next generation of plasma students and researchers — are explained in detail. An example, is the confinement regime — called the 'I-mode' — currently a hot topic — is explored.Numerous important problems and puzzles for the next generation of plasma scientists are explained. There is growing demand for new simulation codes utilizing the massively parallel computers with MPI and GPU methods. When the 20 billion dollar ITER machine is tested in the 2020ies, new theories and faster/smarter computer simulations running in near real-time control systems will be used to control the burning hydrogen plasmas.
Author: James L. Terry Publisher: ISBN: Category : Languages : en Pages : 12
Book Description
The intermittent turbulent transport in the scrape-off-layers of Alcator C-Mod, DIII-D, and NSTX is studied experimentally. On DIII-D the fluctuations of both density and temperature have strongly non-Gaussian statistics, and events with amplitudes above 10 times the mean level are responsible for large fractions of the net particle and heat transport, indicating the importance of turbulence on the transport. In C-Mod and NSTX the turbulence is imaged with a very high density of spatial measurements. The 2-D structure and dynamics of emission from a localized gas puff are observed, and intermittent features (also sometimes called 3blobs4) are typically seen. On DIII-D the turbulence is imaged using BES and similar intermittent features are seen. The dynamics of these intermittent features are discussed. The experimental observations are compared with numerical simulations of edge turbulence. The electromagnetic turbulence in a 3-D geometry is computed using non-linear plasma fluid equations. The wavenumber spectra in the poloidal dimension of the simulations are in reasonable agreement with those of the C-Mod experimental images once the response of the optical system is accounted for. The resistive ballooning mode is the dominant linear instability in the simulations.
Author: Brian LaBombard Publisher: ISBN: Category : Languages : en Pages : 46
Book Description
(Cont) Small gradients and larger fluctuation levels with longer correlation times are found outside this region (far SOL). Deff in the near SOL increases strongly with local plasma collisionality normalized to the magnetic connection length. As the discharge density limit is approached, Deff and associated fluctuation levels become large across the entire SOL and cross-field heat convection everywhere exceeds parallel conduction losses, impacting the power balance of the discharge.
Author: Publisher: ISBN: Category : Aeronautics Languages : en Pages : 610
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: United States. Congress. House. Committee on Appropriations. Subcommittee on Energy and Water Development Publisher: ISBN: Category : Federal aid to energy development Languages : en Pages : 1364
Author: Noah M. Smick Publisher: ISBN: Category : Languages : en Pages : 234
Book Description
(Cont.) Toroidal rotation, Pfirsch-Schlilter and transport-driven contributions are unambiguously identified. Parallel flows are found to dominate the high-field particle fluxes; the total poloidally-directed flow carries one half of the particle flux arriving on the inner divertor. As a result, convection is also found to be an important player in high-field side heat transport. In contrast, E_r x B plus parallel flows yield a mostly-toroidal flow component in the low-field SOL. The magnitude of the transport-driven flow component is found to be quantitatively consistent with radial fluctuation-induced particle fluxes measured on the low-field side, identifying this as the primary driver. In contrast, fluctuation-induced flux measurements on the high-field side midplane are found to be essentially zero, thereby excluding an 'inward pinch' effect as the mechanism that closes the mass-flow loop in this region.
Author: B. Lipschultz
Author: B. Lipschultz
Author: C Wendell Horton, Jr
Author: James L. Terry
Author: 
Author: Brian LaBombard
Author: 
Author: 
Author: United States. Congress. House. Committee on Appropriations. Subcommittee on Energy and Water Development
Author: Noah M. Smick
Author: J. W. Connor