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

Abstract

Small (2–3 mm, 0.9–2 Pa · m 3) 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. Lastly, 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.

Authors:
 [1];  [2];  [1];  [3];  [4];  [1];  [3];  [3];  [5];  [3];  [1];  [2]
  1. Univ. of California, San Diego, CA (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  3. General Atomics, San Diego, CA (United States)
  4. Univ. of Texas, Austin, TX (United States). Inst. for Fusion Studies
  5. Univ. of Strathclyde, Glasgow (United Kingdom). Dept. of Physics
Publication Date:
Research Org.:
General Atomics, San Diego, CA (United States)
Sponsoring Org.:
USDOE
Contributing Org.:
University of California—San Diego, 9500 Gilman Dr, La Jolla, CA 92093-0417, USA Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, TN 37831, USA Institute for Fusion Studies, University of Texas at Austin, 2100 San Jacinto Blvd, Austin, TX 78712-1047, USA Department of Physics, University of Strathclyde, Glasgow GW ONG, UK
OSTI Identifier:
1372061
Grant/Contract Number:  
FC02-04ER54698; FG02-07ER54917; AC05-00OR22725; AC52-07NA27344; AC05-06OR23100
Resource Type:
Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 57; Journal Issue: 1; Related Information: E.M. Hollmann, N. Commaux, R.A. Moyer, P.B. Parks, M.E. Austin, I. Bykov, C. Cooper, N.W. Eidietis, M. OMullane, C. Paz-Soldan, D.L. Rudakov, D. Shiraki, "Use of Ar pellet ablation rate to estimate initial runaway electron seed population in DIII-D rapid shutdown experiments", Nuclear Fusion, 57, 1, 2016; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; tokamak; disruptions; runaway electrons

Citation Formats

Hollmann, E. M., Commaux, N., Moyer, R. A., Parks, P. B., Austin, M. E., Bykov, I., Cooper, C., Eidietis, N. W., O’Mullane, M., Paz-Soldan, C., Rudakov, D. L., and Shiraki, D. Use of Ar pellet ablation rate to estimate initial runaway electron seed population in DIII-D rapid shutdown experiments. United States: N. p., 2016. Web. doi:10.1088/0029-5515/57/1/016008.
Hollmann, E. M., Commaux, N., Moyer, R. A., Parks, P. B., Austin, M. E., Bykov, I., Cooper, C., Eidietis, N. W., O’Mullane, M., Paz-Soldan, C., Rudakov, D. L., & Shiraki, D. Use of Ar pellet ablation rate to estimate initial runaway electron seed population in DIII-D rapid shutdown experiments. United States. doi:10.1088/0029-5515/57/1/016008.
Hollmann, E. M., Commaux, N., Moyer, R. A., Parks, P. B., Austin, M. E., Bykov, I., Cooper, C., Eidietis, N. W., O’Mullane, M., Paz-Soldan, C., Rudakov, D. L., and Shiraki, D. Mon . "Use of Ar pellet ablation rate to estimate initial runaway electron seed population in DIII-D rapid shutdown experiments". United States. doi:10.1088/0029-5515/57/1/016008. https://www.osti.gov/servlets/purl/1372061.
@article{osti_1372061,
title = {Use of Ar pellet ablation rate to estimate initial runaway electron seed population in DIII-D rapid shutdown experiments},
author = {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.},
abstractNote = {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. Lastly, 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.},
doi = {10.1088/0029-5515/57/1/016008},
journal = {Nuclear Fusion},
number = 1,
volume = 57,
place = {United States},
year = {2016},
month = {10}
}

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