Energy balance, radiation and stability during rapid plasma termination via impurity pellet injections on DIII-D

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Injections of impurity {open_quotes}killer{close_quotes} pellets on DIII-D have demonstrated partial mitigation of undesirable disruption phenomena; namely reducing the convected heat loss to the wall, and the halo current`s magnitude and toroidal asymmetry. However, the appearance of a runaway electron population and large magnetic fluctuations (B/B{sub T} {approx} 1%) is coincident with the measured rapid loss of the plasma`s thermal energy ({approx}1 MJ in 1 ms) due to impurity radiation. A numerical code is developed to simulate the impurity radiation and predict the rapid plasma cooling observed. The simulation predicts two mechanisms for the generation of runaway electrons: the {open_quotes}slideaway{close_quotes} of ... continued below

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6 p.

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Whyte, D. G.; Jernigan, T. C. & Luckhardt, S. L. June 1997.

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Description

Injections of impurity {open_quotes}killer{close_quotes} pellets on DIII-D have demonstrated partial mitigation of undesirable disruption phenomena; namely reducing the convected heat loss to the wall, and the halo current`s magnitude and toroidal asymmetry. However, the appearance of a runaway electron population and large magnetic fluctuations (B/B{sub T} {approx} 1%) is coincident with the measured rapid loss of the plasma`s thermal energy ({approx}1 MJ in 1 ms) due to impurity radiation. A numerical code is developed to simulate the impurity radiation and predict the rapid plasma cooling observed. The simulation predicts two mechanisms for the generation of runaway electrons: the {open_quotes}slideaway{close_quotes} of hot tail electrons due to rapid cooling or the transport of hot electrons into the thermally collapsed plasma due to instabilities. Pressure gradients caused by the rapid non-adiabatic cooling of the impurity are identified as the probable source of these instabilities which also lead to convective heat losses. Results of a modeling effort to optimize pellet content, impurity species and cooling time for the avoidance of instabilities and runaway electrons are shown.

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6 p.

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INIS; OSTI as DE97007045

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  • 24. EPS conference on controlled fusion and plasma physics, Berchtesgaden (Germany), 9-13 Jun 1997

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  • Other: DE97007045
  • Report No.: GA--A22639
  • Report No.: CONF-9706131--12
  • Grant Number: AC03-89ER51114;AC05-96OR22464;FG03-95ER54294
  • Office of Scientific & Technical Information Report Number: 513523
  • Archival Resource Key: ark:/67531/metadc689732

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Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

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  • June 1997

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  • Aug. 14, 2015, 8:43 a.m.

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  • April 18, 2016, 5:39 p.m.

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Whyte, D. G.; Jernigan, T. C. & Luckhardt, S. L. Energy balance, radiation and stability during rapid plasma termination via impurity pellet injections on DIII-D, article, June 1997; San Diego, California. (digital.library.unt.edu/ark:/67531/metadc689732/: accessed January 23, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.