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Book Full Wave Simulations of Fast Wave Efficiency and Power Losses in the Scrape off Layer of Tokamak Plasmas in Mid high Harmonic and Minority Heating Regimes

Download or read book Full Wave Simulations of Fast Wave Efficiency and Power Losses in the Scrape off Layer of Tokamak Plasmas in Mid high Harmonic and Minority Heating Regimes written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Several experiments on different machines and in different fast wave (FW) heating regimes, such as hydrogen minority heating and high harmonic fast waves (HHFW), have found strong interaction between radio-frequency (RF) waves and the scrape-off layer (SOL) region. This paper examines the propagation and the power loss in the SOL by using the full wave code AORSA, in which the edge plasma beyond the last closed flux surface (LCFS) is included in the solution domain and a collisional damping parameter is used as a proxy to represent the real, and most likely nonlinear, damping processes. 2D and 3D AORSA results for the National Spherical Torus eXperiment (NSTX) have shown a strong transition to higher SOL power losses (driven by the RF field) when the FW cut-off is removed from in front of the antenna by increasing the edge density. Here, full wave simulations have been extended for 'conventional' tokamaks with higher aspect ratios, such as the DIII-D, Alcator C-Mod, and EAST devices. DIII-D results in HHFW regime show similar behavior found in NSTX and NSTX-U, consistent with previous DIII-D experimental observations. In contrast, a different behavior has been found for C-Mod and EAST, which operate in the minority heating regime.

Book Full Wave Simulations of Fast Wave Mode Conversion and Lower Hybrid Wave Propagation in Tokamaks

Download or read book Full Wave Simulations of Fast Wave Mode Conversion and Lower Hybrid Wave Propagation in Tokamaks written by John C. Wright and published by . This book was released on 2004 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fast Wave (FW) studies of mode conversion (MC) processes at the ion -- ion hybrid layer in toroidal plasmas N must capture the disparate scales of the FW and mode converted ion Bernstein (IBW) and ion cyclotron waves (ICW). Correct modeling of the MC layer requires resolving wavelengths on the order of k pi~1 which leads to a scaling of the maximum poloidal mode number, Mmax, proportional to 1/p (p=pi/L). The computational resources needed a scale with the number of radial (Nr), poloidal (No), and toroidal (No) elements as Nr * No * N3o. Two full wave codes, a massively-parallel-processor (MPP) version of the TORIC-2D finite Larmor radius code [M. Brambilla, Plasma Phys. Controlled Fusion 41, 1 (1999)] and also an all orders spectral code AORSA2D [E. F. Jaeger et al., Phys. Plasmas 9, 1873 (2002) ], have been developed which for the first time are capable of achieving the resolution and speed necessary to address mode conversion phenomena in full two-dimensional (2-D) toroidal geometry. These codes have been used in conjunction with theory and experimental data from the Alcator C-Mod [I. H. Hutchinson et al., Phys. Plasmas 1, 1511 (1994)] to gain new understanding into the nature of FWMC in tokamaks. The MPP version of TORIC is also now capable of running with sufficient resolution to model planned lower hybrid range of frequencies (LHRF) experiments in the Alcator C-Mod.

Book Fast Wave Heating of a Reactor Plasma

Download or read book Fast Wave Heating of a Reactor Plasma written by Thomas Howard Stix and published by . This book was released on with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Fast Wave Heating and Current Drive in Tokamak Plasmas with Negative Central Shear

Download or read book Fast Wave Heating and Current Drive in Tokamak Plasmas with Negative Central Shear written by and published by . This book was released on 1996 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fast waves provide an excellent tool for heating electrons and driving current in the central region of tokamak plasmas. In this paper, we report the use of centrally peaked electron heating and current drive to study transport in plasmas with negative central shear (NCS). Tokamak plasmas with NCS offer the potential of reduced energy transport and improved MHD stability properties, but will require non-inductive current drive to maintain the required current profiles. Fast waves, combined with neutral beam injection, provide the capability to change the central current density evolution and independently vary {ital T{sub e}}, and {ital T{sub i}} for transport studies in these plasmas. Electron heating also reduces the collisional heat exchange between electrons and ions and reduces the power deposition from neutral beams into electrons, thus improving the certainty in the estimate of the electron heating. The first part of this paper analyzes electron and ion heat transport in the L-mode phase of NCS plasmas as the current profile resistively evolves. The second part of the paper discusses the changes that occur in electron as well as ion energy transport in this phase of improved core confinement associated with NCS.

Book Application of Very High Harmonic Fast Waves for Off axis Current Drive in the DIII D and FNSF AT Tokamaks

Download or read book Application of Very High Harmonic Fast Waves for Off axis Current Drive in the DIII D and FNSF AT Tokamaks written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Fast waves at frequencies far above the ion cyclotron frequency and approaching the lower hybrid frequency (also called "helicons" or "whistlers") have application to off-axis current drive in tokamaks with high electron beta. The high frequency causes the whistler-like behavior of the wave power nearly following field lines, but with a small radial component, so the waves spiral slowly toward the plasma center. The high frequency also contributes to strong damping. Modeling predicts robust off-axis current drive with good efficiency compared to alternatives in high performance discharges in DIII-D and Fusion Nuclear Science Facility (FNSF) when the electron beta is above about 1.8%. Detailed analysis of ray behavior shows that ray trajectories and damping are deterministic (that is, not strongly affected by plasma profiles or initial ray conditions), unlike the chaotic ray behavior in lower frequency fast wave experiments. Current drive was found to not be sensitive to the launched value of the parallel index of refraction n.

Book Simulation of the Scrape off Layer Plasma During a Disruption

Download or read book Simulation of the Scrape off Layer Plasma During a Disruption written by and published by . This book was released on 1996 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: The evolution of the scrape-off layer (SOL) during a disruption in the DIII-D tokamak is modeled using the 2-D UEDGE transport code. The focus is on the thermal quench phase when most of the energy content of the discharge is rapidly transported across the magnetic separatrix where it then flows to material surfaces or is radiated. Comparisons between the simulation and an experiment on the DIII-D tokamak are made with the heat flux to the divertor plate, and temperature and density profiles at the SOL midplane. The temporal response of the separate electron and ion heat-flux components to the divertor plate is calculated. The sensitivity of the solution to assumptions of electron heat-flux models and impurity radiation is investigated.

Book Detached Scrape off Layer Tokamak Plasmas

Download or read book Detached Scrape off Layer Tokamak Plasmas written by Jay Kesner and published by . This book was released on 1995 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Scrape off Layer Plasma Modeling for the DIII D Tokamak

Download or read book Scrape off Layer Plasma Modeling for the DIII D Tokamak written by and published by . This book was released on 1994 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: The behavior of the scrape-off layer (SOL) region in tokamaks is believed to play an important role determining the overall device performance. In addition, control of the exhaust power has become one of the most important issues in the design of future devices such as ITER and TPX. This paper presents the results of application of 2-D fluid models to the DII-D tokamak, and research into the importance of processes which are inadequately treated in the fluid models. Comparison of measured and simulated profiles of SOL plasma parameters suggest the physics model contained in the UEDGE code is sufficient to simulate plasmas which are attached to the divertor plates. Experimental evidence suggests the presence of enhanced plasma recombination and momentum removal leading to the existence of detached plasma states. UEDGE simulation of these plasmas obtains a bifurcation to a low temperature plasma at the divertor, but the plasma remains attached. Understanding the physics of this detachment is important for the design of future devices. Analytic studies of the behavior of SOL plasmas enhance our understanding beyond that achieved with fluid modeling. Analysis of the effect of drifts on sheath structure suggest these drifts may play a role in the detachment process. Analysis of the turbulent-transport equations indicate a bifurcation which is qualitatively similar to the experimentally different behavior of the L- and H-mode SOL. Electrostatic simulations of conducting wall modes suggest possible control of the SOL width by biasing.

Book Controlled Fusion and Plasma Physics

Download or read book Controlled Fusion and Plasma Physics written by Kenro Miyamoto and published by Taylor & Francis. This book was released on 2006-10-23 with total page 393 pages. Available in PDF, EPUB and Kindle. Book excerpt: Resulting from ongoing, international research into fusion processes, the International Tokamak Experimental Reactor (ITER) is a major step in the quest for a new energy source.The first graduate-level text to cover the details of ITER, Controlled Fusion and Plasma Physics introduces various aspects and issues of recent fusion research activ

Book Course and Workshop an Applications of RF Waves to Tokamak Plasmas

Download or read book Course and Workshop an Applications of RF Waves to Tokamak Plasmas written by Course and Workshop on Applications of RF Waves to Tokamak Plasmas and published by . This book was released on 1985 with total page 454 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Full wave Calculation of Fast wave Current Drive in Tokamaks Including K Sub Parallel Variations

Download or read book Full wave Calculation of Fast wave Current Drive in Tokamaks Including K Sub Parallel Variations written by and published by . This book was released on 1991 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: When fast waves propagate inward from the edge of a tokamak toward the plasma center, the k(up tack) spectrum produced by the antenna is not maintained but is shifted and deformed due to the presence of the finite poloidal magnetic field. This k(up tack) shift causes a variation in the parallel phase speed of the wave and can therefore have a strong effect on electron damping and current drive efficiency. In this paper, we include this effect in a new full-wave calculation (PICES) which represents the wave fields as a superposition of poloidal modes, thereby reducing k(up tack) to an algebraic operator. The wave equation is solved in general flux coordinates, including a full (non-perturbative) solution for E(up tack) and a reduced-order dielectric formulation to eliminate short-wavelength ion Bernstein modes. A simplified current drive model which includes particle trapping is used to estimate the effect of the k(up tack) shift on current drive efficiency in ITER and D3-D. Results suggest that when single-pass absorption is weak, reflected power may drive current nearly as efficiently as that absorbed on the first pass. 15 refs., 5 figs.