Optimizing Stability, Transport, and Divertor Operation Through Plasma Shaping for Steady-state Scenario Development in DIII-D. PDF Download
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Author: Publisher: ISBN: Category : Languages : en Pages : 33
Book Description
Recent studies on the DIII-D tokamak [J.L. Luxon, Nucl. Fusion 42, 614 (2002)] have elucidated key aspects of the dependence of stability, confinement, and density control on the plasma magnetic configuration, leading to the demonstration of nearly noninductive operation for>1 s with pressure 30% above the ideal no-wall stability limit. Achieving fully noninductive tokamak operation requires high pressure, good confinement, and density control through divertor pumping. Plasma geometry affects all of these. Ideal magnetohydrodynamics modeling of external kink stability suggests that it may be optimized by adjusting the shape parameter known as squareness ([zeta]). Optimizing kink stability leads to an increase in the maximum stable pressure. Experiments confirm that stability varies strongly with [zeta], in agreement with the modeling. Optimization of kink stability via [zeta] is concurrent with an increase in the H-mode edge pressure pedestal stability. Global energy confinement is optimized at the lowest [zeta] tested, with increased pedestal pressure and lower core transport. Adjusting the magnetic divertor balance about a double-null configuration optimizes density control for improved noninductive auxiliary current drive. The best density control is obtained with a slight imbalance toward the divertor opposite the ion grad(B) drift direction, consistent with modeling of these effects. These optimizations have been combined to achieve noninductive current fractions near unity for over 1 s with normalized pressure of 3.5[beta]{sub N}
Author: Publisher: ISBN: Category : Languages : en Pages : 33
Book Description
Recent studies on the DIII-D tokamak [J.L. Luxon, Nucl. Fusion 42, 614 (2002)] have elucidated key aspects of the dependence of stability, confinement, and density control on the plasma magnetic configuration, leading to the demonstration of nearly noninductive operation for>1 s with pressure 30% above the ideal no-wall stability limit. Achieving fully noninductive tokamak operation requires high pressure, good confinement, and density control through divertor pumping. Plasma geometry affects all of these. Ideal magnetohydrodynamics modeling of external kink stability suggests that it may be optimized by adjusting the shape parameter known as squareness ([zeta]). Optimizing kink stability leads to an increase in the maximum stable pressure. Experiments confirm that stability varies strongly with [zeta], in agreement with the modeling. Optimization of kink stability via [zeta] is concurrent with an increase in the H-mode edge pressure pedestal stability. Global energy confinement is optimized at the lowest [zeta] tested, with increased pedestal pressure and lower core transport. Adjusting the magnetic divertor balance about a double-null configuration optimizes density control for improved noninductive auxiliary current drive. The best density control is obtained with a slight imbalance toward the divertor opposite the ion grad(B) drift direction, consistent with modeling of these effects. These optimizations have been combined to achieve noninductive current fractions near unity for over 1 s with normalized pressure of 3.5[beta]{sub N}
Author: Publisher: ISBN: Category : Languages : en Pages : 8
Book Description
DIII-D is using its flexibility and diagnostics to address the critical science required to enable next step fusion devices. We have adapted operating scenarios for ITER to low torque and are now being optimized for transport. Three ELM mitigation scenarios have been developed to near-ITER parameters. New control techniques are managing the most challenging plasma instabilities. Disruption mitigation tools show promising dissipation strategies for runaway electrons and heat load. An off axis neutral beam upgrade has enabled sustainment of high [beta]N capable steady state regimes. Divertor research is identifying the challenge, physics and candidate solutions for handling the hot plasma exhaust with notable progress in heat flux reduction using the snowflake configuration. Our work is helping optimize design choices and prepare the scientific tools for operation in ITER, and resolve key elements of the plasma configuration and divertor solution for an FNSF.
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 : 1490
Author: Y. Nakamura Publisher: Nova Publishers ISBN: 9781594544866 Category : Science Languages : en Pages : 294
Book Description
Nuclear fusion is a process in which two nuclei join, forming a larger nucleus and releasing or absorbing energy. With some exceptions, nuclei lighter than iron release energy when they fuse, while heavier nuclei absorb energy; this is because iron has the largest binding energy. Nuclear fusion of light elements is the energy source which causes stars to shine and hydrogen bombs to explode. Nuclear fusion of heavy elements is part of the process that triggers supernovae. Nuclear fusion as an energy source has several advantages: It is vast, new source of energy; Fuels are plentiful; Inherently safe since any malfunction results in a rapid shutdown; No atmospheric pollution leading to acid rain or "greenhouse" effect; Radioactivity of the reactor structure, caused by the neutrons, decays rapidly and can be minimised by careful selection of low-activation materials. Provision for geological time-span disposal is not needed. This book brings together leading research in this field which will play a major role in the 21st century.
Author: Publisher: ISBN: Category : Languages : en Pages : 15
Book Description
Recent experiments on DIII-D have been carried out to understand and explore optimized tokamak operating modes by exploiting control of the plasma current and pressure profiles using new RF current drive and divertor technology. DIII-D emphasizes plasma shape and divertor experiments using a digital plasma control system and extensive diagnostics to develop improved understanding and control of transport barriers in high performance plasmas. The emphasis of the program is to extend the duration of high performance operating modes beyond the plasma current relaxation time by using ICRF and ECH current drive. Engineering features of the new RF systems being developed for these experiments as well as new divertor results are described. DIII-D employs multi-element ICRF antennas for fast-wave electron heating and on-axis current drive and is beginning 110 GHz ECH experiments with MW-level gyrotrons for off-axis current drive. DIII-D employs active cryogenic divertor neutral particle pumping for plasma density and plasma pressure profile control. A divertor modification is now being implemented on DIII-D to pump higher triangularity plasmas and to better baffle neutral backflow from the recycling divertor region.
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Author: United States. Congress. House. Committee on Appropriations. Subcommittee on Energy and Water Development
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Author: Y. Nakamura
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