Download or read book Poloidal Asymmetries in the Scrape off Layer Plasma of the Alcator C Tokamak written by Brian LaBombard and published by . This book was released on 1986 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Poloidal Asymmetries in the Limiter Shadow Plasma of the Alcator C Tokamak written by Brian LaBombard and published by . This book was released on 1986 with total page 499 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Radial and Poloidal ExB Drifts in the Scrape off Layers of Adivertor Tokamak written by A. V. Chankin and published by . This book was released on 1995 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fusion Energy Update written by and published by . This book was released on 1986 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Response to Comment on Magnetic Topology Effects on Alcator C mod Scrape off Layer Flow written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent interest in the experimental study of tokamak plasma flow for different magnetic field geometries calls for theoretical understanding of the effects of tokamak magnetic topology changes on the flow. The consequences of total magnetic field reversal and/or X-point reversal on divergence-free plasma flow within magnetic flux surfaces are considered and the results are applied to interpret recent Alcator C-Mod scrape-off layer flow measurements. In his comment to that work, Aydemir asserted that poloidal plasma flow reversal is not a valid response to toroidal magnetic field reversal in an up-down symmetric tokamak, and that the toroidal plasma flow must reverse instead. We show that this assertion is wrong due to his misunderstanding of the corresponding symmetry transformation.

Download or read book New Ideas in Tokamak Confinement written by Marshall N. Rosenbluth and published by Springer Science & Business Media. This book was released on 1997-05-08 with total page 514 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Radical and Poloidal ExB Drifts in the Scrape off Layers of a Divertor Tokamak written by P. C. Stangeby and published by . This book was released on 1995 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Local Impurity Puffing as a Scrape off Layer Diagnostic on the Alcator C Mod Tokamak written by David F. Jablonski and published by . This book was released on 1996 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effects of RF Power on SOL Density Profiles and RF Coupling on the Alcator C Mod Tokamak written by Cornwall HongMan Lau and published by . This book was released on 2013 with total page 203 pages. Available in PDF, EPUB and Kindle. Book excerpt: A 100-146GHz swept-frequency X-mode reflectometer constructed and installed at three poloidal locations adjacent to the lower hybrid (LH) launcher and one location adjacent to the new field aligned ion cyclotron range of frequencies (ICRF) antenna has been used to measure the scrape-off-layer (SOL) density profiles under a wide range of plasma parameters in order to study plasma-antenna coupling and non-linear RF-SOL interactions on Alcator C-Mod. After validating the reflectometer density profiles with other density profile diagnostics in easily diagnosed and well understood plasma conditions, detailed reflectometer density profile measurements in plasmas with application of ICRF, LH and ICRF+LH power will be shown in order to understand the physical mechanisms for RF-induced density profile modifications. Results indicate that both ICRF and LH power create significant poloidal density profile asymmetries that are correlated with video camera emissivity measurements. These results will be shown to depend on various plasma parameters such as launched nll of the LH waves, ICRF antenna location, and toroidal magnetic field direction. Both LH and ICRF power have been experimentally observed to modify the poloidal flow in the SOL. These flows are reminiscent of LH and ICRF induced convective cells that have been discussed in the literature. A 2-D diffusive-convective model has been applied to quantify the effects of these RF-induced ExB drifts on the SOL density profiles. For the LH case, the simulation reproduces the experimental trends at all three reflectometer poloidal locations adjacent to the LH launcher and indicates that LH-induced ExB drifts is the dominant physical mechanism producing the experimentally measured density profile modifications. Understanding this RF-induced transport helps elucidate these nonlinear RF-SOL mechanisms. One consequence of these density profile modifications is a change in LH coupling efficiency. A 2-D slab LH coupling model has also been used to quantify the effects of the density profile modifications on LH coupling. It will be shown that LH coupling is extremely sensitive to the edge density profile and to poloidal asymmetries in the density profiles. The inclusion of LH and ICRF-induced ExB drift effects on the observed density profile asymmetries is necessary to understand the experimentally measured LH coupling results during LH only and LH+ICRF operations.

Download or read book Impurity Asymmetries in the Pedestal Region of the Alcator C Mod Tokamak written by Randy Michael Churchill and published by . This book was released on 2014 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt: In an effort to illuminate the effects of the strong plasma gradients in the pedestal region on impurity transport, research was conducted to measure complete sets of impurity density, poloidal and parallel velocity, and temperature at two separate poloidal locations in the pedestal region of the Alcator C-Mod tokamak. To this end, the diagnostic technique gas puff-CXRS was refined and expanded on, allowing for the first time in a tokamak complete measurements of impurities at the high-field side (HFS). Large in-out B5+ impurity density asymmetries were measured in H-mode plasmas with strong boundary electron density gradients, with a build-up of impurity density at the HFS. Impurity temperatures were also found to be asymmetric in the pedestal region, with larger temperatures at the low-field side (LFS). Such temperature asymmetries suggest a significant asymmetry in electron density near the separatrix. In contrast to these H-mode results, plasmas with low boundary electron density gradients, such as L-mode and I-mode, exhibit constant impurity density on a flux surface, even if strong electron temperature gradients are present. Mechanisms which could drive such poloidal asymmetries are explored. Experiments provide evidence against localized impurity sources and fluctuation-induced transport as primary causes. Particle transport timescales are compared, showing that the radial transport becomes comparable to or faster than the parallel transport in the pedestal region. Additionally, modelling of impurity transport using conventional, one-dimensional neoclassical physics fails to correctly reproduce the measured flux-surface averaged impurity density, suggesting along with the timescale estimates that a more complete two-dimensional treatment of impurity particle transport is required. The measured impurity velocities at the LFS and HFS are compared to the canonical form for particle flow velocity within the flux surface of a tokamak. Within the error bars of the measurement, agreement is found with the canonical form. The implications of exact matches to the canonical form are low radial transport, and the E x B drift dominating the perpendicular impurity flow. Further work is motivated into more precise velocity measurements to determine if the velocities exactly match this canonical form.

Download or read book Poloidal Rotation and Density Asymmetries in a Tokamak Plasma with Strong Toroidal Rotation written by Weston Monroe Stacey and published by . This book was released on 1992 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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:

Download or read book Impurity Plume Experiments in the Edge Plasma of the Alcator C Mod Tokamak written by Sanjay Gangadhara and published by . This book was released on 2003 with total page 86 pages. Available in PDF, EPUB and Kindle. Book excerpt: The physics of impurity transport in response to a local gas injection in the scrape-off-layer (SOL) of Alcator C-Mod is investigated. Carbon "plumes'' are formed at variable locations in the SOL -- up to the separatrix -- by puffing deuterated ethylene gas (C2D4) through the end of a reciprocating fast-scanning probe. CCD cameras are used to simultaneously record C+1 and C+2 emission patterns from two near-perpendicular views. The plume dispersal patterns are found to yield direct qualitative information about plasma flow, including the direction of VExB near the separatrix. Impurity transport and plasma-surface interaction physics implicit in the 3-D plume structure is explored in detail using a Monte Carlo impurity transport code, with the aim of extracting background plasma-flow quantities. A number of important local effects involving plasma-probe interaction have been identified: a vertical ExB drift near the probe surface, a parallel electric field above the probe tip arising from plasma recycling off the probe surface, and sputtering of a carbon layer that dynamically forms on the probe surface. The emission patterns are also found to yield important information on flows in the SOL: radial electric field (Er) in the near SOL and volume-averaged values of the parallel Mach number in the far SOL. Er values obtained from plume data compare favorably with estimates of Er based on the poloidal propagation velocity of edge plasma fluctuations measured by the scanning probe. Comparisons between parallel Mach numbers obtained from the plume data and probe measurements indicate that the probe over-estimates the parallel flow towards the divertor in the far SOL. This result supports the picture of particle balance in the SOL of Alcator C-Mod being dominated by main-chamber recycling, with weak plasma flow into the divertor.

Download or read book Physics Briefs written by and published by . This book was released on 1990 with total page 1022 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book INIS Atomindex written by and published by . This book was released on 1988 with total page 902 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Thermal Instabilities and Poloidal Asymmetries in the Tokamak Edge Plasma written by J. Neuhauser and published by . This book was released on 1985 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Vertical Poloidal Asymmetries of Low Z Element Radiation in the PDX Tokamak written by and published by . This book was released on 1983 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Vertical poloidal asymmetries of hydrogen isotopes and low-Z impurity radiation in the PDX tokamak may be caused by poloidally asymmetric sources of these elements at gas inlet valves, limiters or vacuum vessel walls, asymmetric magnetic field geometry in the region beyond the plasma boundary, or by ion curvature drifts. Low ionization states of carbon (C II- C IV) are more easily influenced by edge conditions than is CV. Vertical poloidal asymmetries of CV are correlated with the direction of the toroidal field. The magnitude of the asymmetry agrees with the predictions of a quasifluid neoclassical model. Experimental data and numerical simulations are presented to investigate different models of impurity poloidal asymmetries.