Use of Ar pellet ablation rate to estimate initial runaway electron seed population in DIII-D rapid shutdown experiments

Hollmann, E. M. and Commaux, N. and Moyer, R. A. and Parks, P. B. and Austin, M. E. and Bykov, I. and Cooper, C. and Eidietis, N. W. and O'Mullane, M. and Paz-Soldan, C. and Rudakov, D. L. and Shiraki, D. (2016) Use of Ar pellet ablation rate to estimate initial runaway electron seed population in DIII-D rapid shutdown experiments. Nuclear Fusion, 57 (1). 016008. ISSN 0029-5515 (https://doi.org/10.1088/0029-5515/57/1/016008)

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Abstract

Small (2-3 mm, 0.9-2 Pa • m3) argon pellets are used in the DIII-D tokamak to cause rapid shutdown (disruption) of discharges. The Ar pellet ablation is typically found to be much larger than expected from the thermal plasma electron temperature alone; the additional ablation is interpreted as being due to non-thermal runaway electrons (REs) formed during the pellet-induced temperature collapse. Simple estimates of the RE seed current using the enhanced ablation rate give values of order 1-10 kA, roughly consistent with estimates based on avalanche theory. Analytic estimates of the RE seed current based on the Dreicer formula tend to significantly underestimate it, while estimates based on the hot tail model significantly overestimate it.

  • Item type:Article
    ID code:60325
    Dates:
    Date
    Event
    3 October 2016
    Published
    4 August 2016
    Accepted
    Subjects:Science > Physics
    Department:Faculty of Science > Physics
    Depositing user: Pure Administrator
    Date deposited:28 Mar 2017 09:02
    Last modified:08 Apr 2024 23:25
    Related URLs:
    URI:https://strathprints.strath.ac.uk/id/eprint/60325
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