Measurements of impurity and heat dynamics during noble gas jet-initiated fast plasma shutdown for disruption mitigation in DIII-D

Hollmann, E. M.; Jernigan, T. C.; Groth, M.; Whyte, D.G.; Gray, D.S.; Austin, M. E.; Bray, B.D.; Brennan, D. P.; Brooks, N.H.; Evans, T.E.; Humphreys, D. A.; Lasnier, C.J.; Moyer, R. A.; McLean, A.G.; Parks, P.B.; Rozhansky, V.; Rudakov, D. L.; Strait, E. J.; West, W.P.

doi:10.1088/0029-5515/45/9/003

Cited by 81 publications

(96 citation statements)

References 34 publications

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“…The DIII-D team is now developing the physics basis of this technique for extrapolation to ITER. Recent studies suggest that the transport of the impurities introduced by MGI is a multi-stage process in which MHD mixing of the impurities is an essential component [11]. These studies have shown conclusively that the injected impurities are ionized very near the plasma surface, consistent with the expectations of theory and indicating that other processes must be responsible for the inward transport of the impurities.…”

Section: Disruption Mitigationsupporting

confidence: 71%

Development in the DIII-D tokamak of advanced operating scenarios and associated control techniques for ITER

Wade

2007

Nucl. Fusion

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Abstract. Significant progress has been made on the DIII-D tokamak in the capability to control key plasma features and using such control to expand the operational limits of stationary and steady-state tokamak operation. Recent experiments have demonstrated the capability to suppress the key plasma instabilities of concern for ITER, including edge localized modes, neoclassical tearing modes, and resistive wall modes. In addition, the ability to regulate the rotation and current density profiles through feedback control has been demonstrated. The use of these control techniques has allowed an expansion of the envelope of viable, stationary tokamak operation, highlighted by the demonstration of sustained (~2 s) operation of ! N_ 4 (50% above the no-wall stability limit) as well as fully noninductive operation with !_ 3.5%. This development is supported by a vigorous basic physics program, which has provided new insights into turbulence dynamics over a large range in spatial scales, new measurements of the structure of fast-ion instabilities and their effect on the fast ion population, and important information on the transport of carbon and associated tritium co-deposition on plasma facing surfaces.

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Section: Disruption Mitigationsupporting

confidence: 71%

Development in the DIII-D tokamak of advanced operating scenarios and associated control techniques for ITER

Wade

2007

Nucl. Fusion

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“…Thus, a mitigation technique has to provide a reliable suppression of this avalanche mechanism. Presently, massive gas injection is discussed as a technique to mitigate forces and heat loads and also to suppress runaway generation [20][21][22][23][24][25][26]15]. However, the latter aim might have severe implications which are not easily overcome.…”

Section: Runaway Dynamics and Wall Interactionmentioning

confidence: 99%

Runaway generation during disruptions in JET and TEXTOR

Lehnen¹,

Abdullaev²,

Arnoux

et al. 2009

Journal of Nuclear Materials

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Runaway electrons generated during ITER disruptions are of concern for the integrity of the plasma facing components. It is expected that a power of up to 8 GW is exposed to ITER PFCs. We present in this article observations from JET and TEXTOR on the generation of runaways and the heat load deposition. Suppression techniques like massive gas injection and resonant magnetic perturbations are discussed.

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“…Tore Supra shows, that puffs of helium (< 10 23 atoms) suppress REs in the disruptions where the RE generation would otherwise occur [36]. DIII-D reports on a weak runaway population I RE < 0.1 · I p for helium, neon and argon [37,38]. In experiments in ASDEX Upgrade REs are rare and appear only in discharges with densities below 4 · 10 19 m −3 and B t > 2 T. Runaway electrons were not specifically addressed in ASDEX Upgrade [12].…”

Section: Electrons (Equation 2)mentioning

confidence: 99%

Generation and suppression of runaway electrons in disruption mitigation experiments in TEXTOR

Bozhenkov¹,

Lehnen²,

Finken³

et al. 2008

Plasma Phys. Control. Fusion

122

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Abstract. Runaway electrons represent a serious problem for the reliable operation of the future experimental tokamak ITER. Due to the multiplication factor of exp(50) in the avalanche even a few seed runaway electrons will result in a beam of high energetic electrons that is able to damage the machine. Thus suppression of runaway electrons is a task of high importance, for which reason we present here a systematic study of runaway electrons following massive gas injection in TEXTOR. Argon injection can cause generation of runaways carrying up to 30% of the initial plasma current, while disruptions triggered by injection of helium or of mixtures of argon (5, 10, 20%) with deuterium are runaway free. Disruptions caused by argon injection finally become runaway free for very large amounts of injected atoms. The appearance/absence of runaway electrons is related to the fraction of atoms delivered to the plasma center. This so called mixing efficiency is deduced from a 0D model of the current quench. The estimated mixing efficiency is: 3% for argon, 15% for an argon/deuterium mixture and about 40% for helium. A low mixing efficiency of high-Z impurities can have a strong implication for the design of the disruption mitigation system for ITER. However, a quantitative prediction requires a better understanding of the mixing mechanism.

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Measurements of impurity and heat dynamics during noble gas jet-initiated fast plasma shutdown for disruption mitigation in DIII-D

Cited by 81 publications

References 34 publications

Development in the DIII-D tokamak of advanced operating scenarios and associated control techniques for ITER

Development in the DIII-D tokamak of advanced operating scenarios and associated control techniques for ITER

Runaway generation during disruptions in JET and TEXTOR

Generation and suppression of runaway electrons in disruption mitigation experiments in TEXTOR

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