Thermal quench mitigation and current quench control by injection of mixed species shattered pellets in DIII-D

D. Shiraki; N. Commaux; L. R. Baylor; N. W. Eidietis; E. M. Hollmann; C. J. Lasnier; R. A. Moyer

doi:10.1063/1.4954389

Thermal quench mitigation and current quench control by injection of mixed species shattered pellets in DIII-D

D. Shiraki, N. Commaux, L. R. Baylor, N. W. Eidietis, E. M. Hollmann, C. J. Lasnier, R. A. Moyer

Research output: Contribution to journal › Article › peer-review

57 Scopus citations

Abstract

Injection of large shattered pellets composed of variable quantities of the main ion species (deuterium) and high-Z impurities (neon) in the DIII-D tokamak demonstrates control of thermal quench (TQ) and current quench (CQ) properties in mitigated disruptions. As the pellet composition is varied, TQ radiation fractions increase continuously with the quantity of radiating impurity in the pellet, with a corresponding decrease in divertor heating. Post-TQ plasma resistivities increase as a result of the higher radiation fraction, allowing control of current decay timescales based on the pellet composition. Magnetic reconstructions during the CQ show that control of the current decay rate allows continuous variation of the minimum safety factor during the vertically unstable disruption, reducing the halo current fraction and resulting vessel displacement. Both TQ and CQ characteristics are observed to saturate at relatively low quantities of neon, indicating that effective mitigation of disruption loads by shattered pellet injection (SPI) can be achieved with modest impurity quantities, within injection quantities anticipated for ITER. This mixed species SPI technique provides a possible approach for tuning disruption properties to remain within the limited ranges allowed in the ITER design.

Original language	English
Article number	062516
Journal	Physics of Plasmas
Volume	23
Issue number	6
DOIs	https://doi.org/10.1063/1.4954389
State	Published - Jun 1 2016

Funding

The authors thank D. Humphreys for many helpful discussions on halo current modeling. This material is based upon the work supported by U.S. Department of Energy, Office of Science, Office of Fusion Energy Sciences, using the DIII-D National Fusion Facility, a DOE Office of Science user facility, under Award Nos. DE-FC02-04ER54698, DE-AC05-00OR22725, DE-FG02-07ER54917, and DE-AC52-07NA27344.

Funders	Funder number
DOE Office of Science	DE-AC05-00OR22725, DE-FC02-04ER54698, DE-AC52-07NA27344, DE-FG02-07ER54917
U.S. Department of Energy
Office of Science
Fusion Energy Sciences

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

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10.1063/1.4954389

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abstract = "Injection of large shattered pellets composed of variable quantities of the main ion species (deuterium) and high-Z impurities (neon) in the DIII-D tokamak demonstrates control of thermal quench (TQ) and current quench (CQ) properties in mitigated disruptions. As the pellet composition is varied, TQ radiation fractions increase continuously with the quantity of radiating impurity in the pellet, with a corresponding decrease in divertor heating. Post-TQ plasma resistivities increase as a result of the higher radiation fraction, allowing control of current decay timescales based on the pellet composition. Magnetic reconstructions during the CQ show that control of the current decay rate allows continuous variation of the minimum safety factor during the vertically unstable disruption, reducing the halo current fraction and resulting vessel displacement. Both TQ and CQ characteristics are observed to saturate at relatively low quantities of neon, indicating that effective mitigation of disruption loads by shattered pellet injection (SPI) can be achieved with modest impurity quantities, within injection quantities anticipated for ITER. This mixed species SPI technique provides a possible approach for tuning disruption properties to remain within the limited ranges allowed in the ITER design.",

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AU - Eidietis, N. W.

AU - Hollmann, E. M.

AU - Lasnier, C. J.

AU - Moyer, R. A.

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Thermal quench mitigation and current quench control by injection of mixed species shattered pellets in DIII-D

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UN SDGs

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