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

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.

doi:10.1088/0029-5515/57/1/016008

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

Journal Article · Mon Oct 03 00:00:00 EDT 2016 · Nuclear Fusion

DOI:https://doi.org/10.1088/0029-5515/57/1/016008· OSTI ID:1372061

Hollmann, E. M. ^[1]; Commaux, N. ^[2]; Moyer, R. A. ^[3]; Parks, P. B. ^[4]; Austin, M. E. ^[5]; Bykov, I. ^[3]; Cooper, C. ^[4]; Eidietis, N. W. ^[4]; O’Mullane, M. ^[6]; Paz-Soldan, C. ^[4]; Rudakov, D. L. ^[3]; Shiraki, D. ^[2]

Univ. of California, San Diego, CA (United States); General Atomics
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Univ. of California, San Diego, CA (United States)
General Atomics, San Diego, CA (United States)
Univ. of Texas, Austin, TX (United States). Inst. for Fusion Studies
Univ. of Strathclyde, Glasgow (United Kingdom). Dept. of Physics

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.

View Accepted Manuscript (DOE)

Research Organization:: General Atomics, San Diego, CA (United States)

Sponsoring Organization:: USDOE

Contributing Organization:: 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

Grant/Contract Number:: AC05-00OR22725; AC05-06OR23100; AC52-07NA27344; FC02-04ER54698; FG02-07ER54917

OSTI ID:: 1372061

Alternate ID(s):: OSTI ID: 22925547

Journal Information:: Nuclear Fusion, Journal Name: Nuclear Fusion Journal Issue: 1 Vol. 57; ISSN 0029-5515

Publisher:: IOP ScienceCopyright Statement

Country of Publication:: United States

Language:: English

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