Plasma Shape Optimization for Steady-State Tokamak Development in DIII-D. PDF Download
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Author: Publisher: ISBN: Category : Languages : en Pages : 7
Book Description
For a more detailed account of the results summarized here and for references, see C.T. Holcomb et al., Phys. Plasmas 16, 056116 (2009). Advanced tokamak research on DIII-D is focused on developing a high fusion gain, steady-state scenario that would eliminate or greatly reduce the demands on an inductive transformer in future machines. Steady-state operation requires the inductively driven current density (j{sub Ind}) be zero everywhere. Most of the total current I{sub p} is typically from self-driven bootstrap current, with the remainder driven by external noninductive sources, such as neutral beam and radiofrequency current drive. This paper describes an extension of the fully noninductive condition (f{sub NI} ≈ 100%) to ≈0.7 current relaxation times that was achieved by a combination of more available ECCD and new scientific insights. The insights are an optimization of performance through variation of the plasma shape parameter known as squareness ([zeta]) and an optimization of divertor magnetic balance. These optimizations simultaneously improve stability, confinement, and density control. These are each essential for achieving fully noninductive operation.
Author: Publisher: ISBN: Category : Languages : en Pages : 7
Book Description
For a more detailed account of the results summarized here and for references, see C.T. Holcomb et al., Phys. Plasmas 16, 056116 (2009). Advanced tokamak research on DIII-D is focused on developing a high fusion gain, steady-state scenario that would eliminate or greatly reduce the demands on an inductive transformer in future machines. Steady-state operation requires the inductively driven current density (j{sub Ind}) be zero everywhere. Most of the total current I{sub p} is typically from self-driven bootstrap current, with the remainder driven by external noninductive sources, such as neutral beam and radiofrequency current drive. This paper describes an extension of the fully noninductive condition (f{sub NI} ≈ 100%) to ≈0.7 current relaxation times that was achieved by a combination of more available ECCD and new scientific insights. The insights are an optimization of performance through variation of the plasma shape parameter known as squareness ([zeta]) and an optimization of divertor magnetic balance. These optimizations simultaneously improve stability, confinement, and density control. These are each essential for achieving fully noninductive operation.
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: T. C. Luce Publisher: ISBN: Category : Languages : en Pages :
Book Description
Significant progress in the development of burning plasma scenarios, steady-state scenarios at high fusion performance, and basic tokamak physics has been made by the DIII-D Team. Discharges similar to the ITER baseline scenario have demonstrated normalized fusion performance nearly 50% higher than required for Q = 10 in ITER, under stationary conditions. Discharges that extrapolate to Q {approx} 10 for longer than one hour in ITER at reduced current have also been demonstrated in DIII-D under stationary conditions. Proof of high fusion performance with full noninductive operation has been obtained. Underlying this work are studies validating approaches to confinement extrapolation, disruption avoidance and mitigation, tritium retention, ELM avoidance, and operation above the no-wall pressure limit. In addition, the unique capabilities of the DIII-D facility have advanced studies of the sawtooth instability with unprecedented time and space resolution, threshold behavior in the electron heat transport, and rotation in plasmas in the absence of external torque.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Significant progress in the development of burning plasma scenarios, steady-state scenarios at high fusion performance, and basic tokamak physics has been made by the DIII-D Team. Discharges similar to the ITER baseline scenario have demonstrated normalized fusion performance nearly 50% higher than required for Q = 10 in ITER, under stationary conditions. Discharges that extrapolate to Q (almost equal to) 10 for longer than one hour in ITER at reduced current have also been demonstrated in DIII-D under stationary conditions. Proof of high fusion performance with full noninductive operation has been obtained. Underlying this work are studies validating approaches to confinement extrapolation, disruption avoidance and mitigation, tritium retention, ELM avoidance, and operation above the no-wall pressure limit. In addition, the unique capabilities of the DIII-D facility have advanced studies of the sawtooth instability with unprecedented time and space resolution, threshold behavior in the electron heat transport, and rotation in plasmas in the absence of external torque.
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Author: C. E. Kessel
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Author: C. E. Kessel
Author: T. C. Luce
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Author: Amor Tahari