Estimate of pre-thermal quench non-thermal electron density profile during Ar pellet shutdowns of low-density target plasmas in DIII-D

Embréus, Ola, 1991 (author): Chalmers tekniska högskola,Chalmers University of Technology

Hoppe, Mathias, 1993 (author): Chalmers tekniska högskola,Chalmers University of Technology

Svenningsson, Ida, 1996 (author): Chalmers tekniska högskola,Chalmers University of Technology

(creator_code:org_t)

AIP Publishing, 2021
2021
English.
In: Physics of Plasmas. - : AIP Publishing. - 1089-7674 .- 1070-664X. ; 28:7

Related links:: https://research.cha... (primary) (free); show more...; https://research.cha...; https://research.cha...; https://doi.org/10.1...; show less...

Abstract Subject headings

The radial density profile of pre-thermal quench (pre-TQ) early-time non-thermal (hot) electrons is estimated by combining electron cyclotron emission and soft x-ray data during the rapid shutdown of low-density (ne≲1019m−3) DIII-D target plasmas with cryogenic argon pellet injection. This technique is mostly limited in these experiments to the pre-TQ phase and quickly loses validity during the TQ. Two different cases are studied: a high (10 keV) temperature target and a low (4 keV) temperature target. The results indicate that early-time, low-energy (∼10 keV) hot electrons form ahead of the argon pellet as it enters the plasma, affecting the pellet ablation rate; it is hypothesized that this may be caused by rapid cross field transport of argon ions ahead of the pellet or by rapid cross field transport of hot electrons. Fokker-Planck modeling of the two shots suggests that the hot electron current is quite significant during the pre-TQ phase (up to 50% of the total current). Comparison between modeled pre-TQ hot electron current and post-TQ hot electron current inferred from avalanche theory suggests that hot electron current increases during the high-temperature target TQ but decreases during the low-temperature target TQ. The uncertainties in this estimate are large; however, if true, this suggests that TQ radial loss of hot electron current could be larger than previously estimated in DIII-D.

By the author/editor: Hollmann, E M; Austin, M.; Bykov, I.; Eidietis, N. W.; Embréus, Ola, 19 ...; Herfindal, J.; show more...; Hoppe, Mathias, ...; Lvovskiy, A.; Parks, P.; Paz-Soldan, C.; Shiraki, D.; Svenningsson, Id ...; show less...

About the subject

NATURAL SCIENCES: NATURAL SCIENCES; and Physical Science ...; and Atom and Molecul ...

NATURAL SCIENCES: NATURAL SCIENCES; and Physical Science ...; and Fusion Plasma an ...

NATURAL SCIENCES: NATURAL SCIENCES; and Physical Science ...; and Condensed Matter ...

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