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Effects of Particle Fueling and Plasma Wall Interactions on DIII-D Discharges

Effects of Particle Fueling and Plasma Wall Interactions on DIII-D Discharges PDF Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 55

Book Description
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.

Effects of Particle Fueling and Plasma Wall Interactions on DIII-D Discharges

Effects of Particle Fueling and Plasma Wall Interactions on DIII-D Discharges PDF Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 55

Book Description
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.

Scientific and Technical Aerospace Reports

Scientific and Technical Aerospace Reports PDF Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 548

Book Description


STAR

STAR PDF Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 2216

Book Description


Particle Flows in Pumped DIII-D Discharges

Particle Flows in Pumped DIII-D Discharges PDF Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :

Book Description
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.

Government Reports Announcements & Index

Government Reports Announcements & Index PDF Author:
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 614

Book Description


Recycling and Particle Control in DIII-D.

Recycling and Particle Control in DIII-D. PDF Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 25

Book Description
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.

Energy Research Abstracts

Energy Research Abstracts PDF Author:
Publisher:
ISBN:
Category : Power resources
Languages : en
Pages : 782

Book Description


Plasma Physics and Controlled Nuclear Fusion Research

Plasma Physics and Controlled Nuclear Fusion Research PDF Author:
Publisher:
ISBN:
Category : Controlled fusion
Languages : en
Pages : 838

Book Description


Metals Abstracts

Metals Abstracts PDF Author:
Publisher:
ISBN:
Category : Metallurgy
Languages : en
Pages : 1628

Book Description


Fusion Technology 1990

Fusion Technology 1990 PDF Author: B.E. Keen
Publisher: Elsevier
ISBN: 0444600655
Category : Technology & Engineering
Languages : en
Pages : 1039

Book Description
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.