A Calculation Model for Density Limits in Auxiliary Heated, Gas Fueled Tokamaks and Application to DIII-D Model Problems PDF Download
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Author: Weston M. Stacey
Publisher:
ISBN:
Category : Plasma density
Languages : en
Pages : 34
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Author: Weston M. Stacey
Publisher:
ISBN:
Category : Plasma density
Languages : en
Pages : 34
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Book Description
Author: Weston M. Stacey
Publisher:
ISBN:
Category : Plasma density
Languages : en
Pages : 31
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Author:
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ISBN:
Category : Power resources
Languages : en
Pages : 1224
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Author: DG. WHYTE
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Category :
Languages : en
Pages : 5
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OAK-B135 Density limit disruptions set an upper bound on the electron density in tokamaks and are important for future reactor-size tokamaks, which will typically need to operate at high densities to achieve ignition. In the standard picture of disruptions, a large MHD mode, or combination of MHD modes, causes a mixing of previously nested magnetic flux surfaces across much of the profile. Rapid heat and particle transport across the separatrix result, and the thermal energy of the discharge is lost along open field lines into the divertor on a millisecond time scale or faster. In this work, a density limit disruption is initiated by ramping up the density in a lower single-null discharge in the DIII-D tokamak. As in most disruptions, a large MHD precursor is observed. However, in contrast with the disruption scenario described above, it is found that the plasma thermal energy, rather than being conducted into the divertor, is dominantly lost by radiation to the main chamber walls. This has been referred to as self-mitigation of the disruption, in comparison to the intentional mitigation of localized heat loads in disruptions by the introduction of pellets or liquid or gas jets to enhance radiation. The self-mitigation effect appears to result from a release of neutrals (deuterium and carbon) from the graphite vacuum vessel walls. These results could have favorable implications for the severity of divertor heat loads during density limit disruptions in future large tokamaks.
Author:
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Category : Physics
Languages : en
Pages : 568
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Author:
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Category : Nuclear energy
Languages : en
Pages : 988
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Author:
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ISBN:
Category :
Languages : en
Pages :
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Author: Weston Monroe Stacey
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ISBN:
Category : Plasma injection
Languages : en
Pages : 43
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Author:
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ISBN:
Category :
Languages : en
Pages : 31
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Discharges with negative central magnetic shear (NCS) hold the promise of enhanced fusion performance in advanced tokamaks. However, stability to long wavelength magnetohydrodynamic modes is needed to take advantage of the improved confinement found in NCS discharges. The stability limits seen in DIII-D experiments depend on the pressure and current density profiles and are in good agreement with stability calculations. Discharges with a strongly peaked pressure profile reach a disruptive limit at low beta, [beta]{sub N} = [beta] (I/aB)−1 d"2.5 (% m T/MA), caused by an n = 1 ideal internal kink mode or a global resistive instability close to the ideal stability limit. Discharges with a broad pressure profile reach a soft beta limit at significantly higher beta, [beta]{sub N} = 4 to 5, usually caused by instabilities with n> 1 and usually driven near the edge of the plasma. With broad pressure profiles, the experimental stability limit is independent of the magnitude of negative shear but improves with the internal inductance, corresponding to lower current density near the edge of the plasma. Understanding of the stability limits in NCS discharges has led to record DIII-D fusion performance in discharges with a broad pressure profile and low edge current density.
Author: Michael Tendler
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ISBN:
Category :
Languages : en
Pages : 26
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