Download or read book Effects of Particle Fueling and Plasma Wall Interactions on DIII D Discharges written by and published by . This book was released on 1994 with total page 55 pages. Available in PDF, EPUB and Kindle. Book excerpt: DIII-D has successfully operated with an all-graphite first wall, including the first observations of VH-mode without boronization. A major goal of this, and other recent upgrades, was to control impurity influxes and hydrogenic fueling. Graphite tiles were carefully pre-conditioned, first by ex situ preparation and then by baking and helium glow conditioning. No deuterium or hydrogen was used until tokamak operation commenced. With the all graphite wall, both impurity and deuterium influxes during tokamak discharges were lower than previous boronized discharges; central nickel impurity line radiation, NiXXV and NiXXVI, was an order of magnitude lower than previous discharges during the ELM free beam heated phase. The effect of reduced particle fueling on plasma performance, particularly H- and VH-mode discharges, will be presented.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 548 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book STAR written by and published by . This book was released on 1965 with total page 2216 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Particle Flows in Pumped DIII D Discharges written by and published by . This book was released on 2000 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The dynamics of particle flows in the DIII-D tokamak for two divertor configurations is considered. Fuel and intrinsic carbon impurity flows are analyzed using experimental data and 2D fluid plasma simulations. The flows in puff and pump experiments done in an open and a closed divertor geometry are described. It is shown that the flow of fuel particles is sensitive to divertor geometry. The pumping efficiency of the DIII-D cryopumps is a factor of 2 higher in a closed geometry than an open. The core refueling rate of an open divertor is a factor of 2 higher than that of a closed divertor. In contrast, the flow of impurity carbon particles is insensitive to divertor geometry. Both the core carbon content and the fraction of the carbon source which penetrates to the core is unchanged between an open and closed divertor. In addition, the core impurity content is found to be insensitive to the amplitude of gas puffing in the simulations.
Download or read book Wall Conditioning and Plasma Surface Interactions in DIII D written by and published by . This book was released on 1990 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: Wall conditioning is used in DIII-D for both reduction of impurity influxes and particle control. The methods used include: baking, pulsed discharge cleaning, hydrogen glow cleaning, helium and neon glow conditioning, and carbonization. Helium glow wall conditioning applied before every tokamak discharge has been effective in impurity removal and particle control and has significantly expanded the parameter space in which DIII-D operates to include limiter and ohmic H-mode discharges and higher [beta]{sub T} at low q. The highest values of divertor plasma current (3.0 MA) and stored energy (3.6 MJ) and peaked density profiles in H-mode discharges have been observed after carbonization. Divertor physics studies in DIII-D include sweeping the X-point to reduce peak heat loads, measurement of particle and heat fluxes in the divertor region, and erosion studies. The DIII-D Advanced Divertor has been installed and bias and baffle experiments will begin in the fall of 1991. 15 refs., 4 figs.
Download or read book Government Reports Announcements Index written by and published by . This book was released on 1995 with total page 614 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Recycling and Particle Control in DIII D written by and published by . This book was released on 1991 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt: Particle control of both hydrogen and impurity atoms is important in obtaining reproducible discharges with a low fraction of radiated power in the DIII-D tokamak. The main DIII-D plasma facing components are graphite tiles and Inconel. Hydrogenic species desorbed from graphite during a tokamak discharge can be a major fueling source, especially in unconditioned graphite where these species can saturate the surface regions. In this case the recycling coefficient can exceed unity, leading to an uncontrolled density rise. In addition to removing volatile hydrocarbons and oxygen, DIII-D vessel conditioning efforts have been directed at the reduction of particle fueling from the graphite tiles. Conditioning techniques include: baking to (less-than or equal to) 400°C, low power pulsed discharge cleaning, and glow discharges in deuterium, helium, neon, or argon. Helium glow wall conditioning, is now routinely performed before every tokamak discharge. The effects of these techniques on hydrogen recycling and impurity influxes will be presented. The Inconel walls, while not generally exposed to high heat fluxes, nevertheless represent a source of metal impurities which can lead to impurity accumulation in the discharge and a high fraction of radiated power, particularly in H-mode discharges at higher plasma currents, I{sub p}> 1.5 MA. To reduce metal influx a thin ((approximately)100 nm) low Z film has been applied on all plasma facing surfaces in DIII-D. The application of the boron film, referred to as boronization has the additional benefit over a carbon film of further reducing the oxygen influx. Following the first boronization in DIII-D a regime of very high confinement (VH-mode) was observed, characterized by low ohmic target density, low Z{sub eff}, and low radiated power.
Download or read book Energy Research Abstracts written by and published by . This book was released on 1995 with total page 782 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Plasma Physics and Controlled Nuclear Fusion Research written by and published by . This book was released on 1994 with total page 838 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Plasma Surface Interactions in Controlled Fusion Devices written by and published by . This book was released on 1978 with total page 658 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Metals Abstracts written by and published by . This book was released on 1996 with total page 1628 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Far SOL Transport and Main Wall Plasma Interaction in DIII D written by and published by . This book was released on 2004 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: Far scrape-off layer (SOL) and near-wall plasma parameters in DIII-D depend strongly on the discharge parameters and confinement regime. In L-mode discharges cross-field transport increases with the average discharge density and flattens far SOL profiles, thus increasing plasma-wall contact. In H-mode between edge localized modes (ELMs), plasma-wall contact is generally weaker than in L-mode. During ELMs plasma fluxes to the wall increase to, or above the L-mode levels. Depending on the discharge conditions ELMs are responsible for 30-90% of the ion flux to the outboard chamber wall. Cross-field fluxes in far SOL are dominated by large amplitude intermittent transport events that may propagate all the way to the outer wall and cause sputtering. A Divertor Material Evaluation System (DiMES) probe containing samples of several ITER-relevant materials including carbon, beryllium and tungsten was exposed to a series of upper single null (USN) discharges as a proxy to measure the first wall erosion.
Download or read book Fusion Technology 1990 written by B.E. Keen and published by Elsevier. This book was released on 2012-12-02 with total page 1039 pages. Available in PDF, EPUB and Kindle. Book excerpt: The aim of the biennial series of symposia on Fusion Technology, organized by the European Fusion Laboratories, is the exchange of information on the design, construction and operation of fusion experiments. The coverage of the volume includes the technology aspects of fusion reactors to provide a link to the technology of new developments and form a guideline for the definition of future work. These proceedings comprise two volumes and contain both the invited lectures and contributed papers presented at the Symposium, which was attended by 556 participants from around the globe. The 312 papers in this volume, including 17 invited papers, give a broad and current overview of the progress and trends fusion technology is experiencing now, and the future for fusion devices.
Download or read book In situ Measurement of Plasma Surface Interactions and Diagnostic Development for Fusion Applications written by Soren David Harrison and published by . This book was released on 2008 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book ELM Induced Plasma Wall Interactions in DIII D written by and published by . This book was released on 2008 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: Intense transient fluxes of particles and heat to the main chamber components induced by edge localized modes (ELMs) are of serious concern for ITER. In DIII-D, plasma interaction with the outboard chamber wall is studied using Langmuir probes and optical diagnostics including a fast framing camera. Camera data shows that ELMs feature helical filamentary structures localized at the low field side of the plasma and aligned with the local magnetic field. During the nonlinear phase of an ELM, multiple filaments are ejected from the plasma edge and propagate towards the outboard wall with velocities of 0.5-0.7 km/s. When reaching the wall, filaments result in 'hot spots'--regions of local intense plasma-material interaction (PMI) where the peak incident particle and heat fluxes are up to 2 orders of magnitude higher than those between ELMs. This interaction pattern has a complicated geometry and is neither toroidally nor poloidally symmetric. In low density/collisionality H-mode discharges, PMI at the outboard wall is almost entirely due to ELMs. In high density/collisionality discharges, contributions of ELMs and inter-ELM periods to PMI at the wall are comparable. A Midplane Material Evaluation Station (MiMES) has been recently installed in order to conduct in situ measurements of erosion/redeposition at the outboard chamber wall, including those caused by ELMs.
Download or read book Fusion Energy Update written by and published by . This book was released on 1980 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Edge Plasma Effects in DIII D Impurity Seeded Discharges written by and published by . This book was released on 2002 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: DIII-D, ELMing H-mode radiating mantle discharges have been obtained with electron density near the Greenwald density limit and a large fraction of the input power radiated inside the last closed flux surface, significantly reducing peak divertor heat fluxes. In these ''puff and pump'' discharges, the introduction of argon reduces particle flux to divertor tiles by a factor of 4 while peak heat flux is half of the no impurity value, suggesting that impurity seeding may be a useful control tool to reduce wall heat and particle fluxes in fusion reactors. A robust H-mode transport barrier is maintained and there is little change in the ELM energy or in the ELM frequency.
