Alfvén eigenmodes and fast ion transport in negative triangularity DIII-D plasmas

M. A. Van Zeeland; C. S. Collins; W. W. Heidbrink; M. E. Austin; X. D. Du; V. N. Duarte; A. Hyatt; G. Kramer; N. Gorelenkov; B. Grierson; D. Lin; A. Marinoni; G. McKee; C. Muscatello; C. Petty; C. Sung; K. E. Thome; M. Walker; Y. B. Zhu

doi:10.1088/1741-4326/ab2488

Alfvén eigenmodes and fast ion transport in negative triangularity DIII-D plasmas

M. A. Van Zeeland, C. S. Collins, W. W. Heidbrink, M. E. Austin, X. D. Du, V. N. Duarte, A. Hyatt, G. Kramer, N. Gorelenkov, B. Grierson, D. Lin, A. Marinoni, G. McKee, C. Muscatello, C. Petty, C. Sung, K. E. Thome, M. Walker, Y. B. Zhu

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Abstract

The first energetic particle experiments in negative triangularity tokamak plasmas have been carried out on DIII-D. Alfvén eigenmode (AE) activity and associated fast ion transport comparable to that in positive triangularity is observed during the current ramp portion of all plasmas with early beam heating indicating negative triangularity does not confer a special advantage with respect to AE induced transport. In these discharges, a range of mode activity driven by the sub-Alfvénic (V_beam/V_A < 0.5) 80 kV neutral beams is found including beta induced Alfvén acoustic eigenmodes, beta induced Alfvén eigenmodes, reversed shear Alfvén eigenmodes (RSAEs) and toroidicity induced Alfvén eigenmodes (TAEs). Mode intermittency and possibly chirping appears to be more common than comparable positive triangularity and/or oval discharges but overall, the unstable spectra and mode amplitudes observed on magnetics, CO2 interferometry, and electron cyclotron emission in a set of matched positive and negative triangularity cases at moderate beam power is similar. Large levels of Alfvén eigenmode induced fast ion transport are found in both positive and negative triangularity with up to 70% central fast ion pressure deficits relative to classical predictions early during the current ramp phase for discharges with 3 MW injected 80 kV neutral beam power. The deficit in both cases is reduced toward zero as the current penetrates and eventually reaches classical levels during current flattop with q_min≈ 1. Fast ion transport in negative triangularity plasmas measured using a beam modulation technique show very similar levels to those measured in oval plasmas over the range of tested beam powers (P_beam≈ 2 7 MW). This similarity is found despite quite different unstable spectra in the highest beam power case where a mixture of coherent and quasi-coherent modes in the TAE frequency range are observed in negative triangularity and a spectrum of more typical narrowband TAEs and RSAEs is observed for the oval plasmas.

Original language	English
Article number	086028
Journal	Nuclear Fusion
Volume	59
Issue number	8
DOIs	https://doi.org/10.1088/1741-4326/ab2488
State	Published - Jun 27 2019
Externally published	Yes

Keywords

Alfven waves
MHD stability
fusion products effects
magnetohydrodynamic waves
plasma heating by particle beams
tokamaks

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

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10.1088/1741-4326/ab2488

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Van Zeeland, M. A., Collins, C. S., Heidbrink, W. W., Austin, M. E., Du, X. D., Duarte, V. N., Hyatt, A., Kramer, G., Gorelenkov, N., Grierson, B., Lin, D., Marinoni, A., McKee, G., Muscatello, C., Petty, C., Sung, C., Thome, K. E., Walker, M., & Zhu, Y. B. (2019). Alfvén eigenmodes and fast ion transport in negative triangularity DIII-D plasmas. Nuclear Fusion, 59(8), Article 086028. https://doi.org/10.1088/1741-4326/ab2488

@article{a00d019433c347bcb1993b785a98360b,

title = "Alfv{\'e}n eigenmodes and fast ion transport in negative triangularity DIII-D plasmas",

abstract = "The first energetic particle experiments in negative triangularity tokamak plasmas have been carried out on DIII-D. Alfv{\'e}n eigenmode (AE) activity and associated fast ion transport comparable to that in positive triangularity is observed during the current ramp portion of all plasmas with early beam heating indicating negative triangularity does not confer a special advantage with respect to AE induced transport. In these discharges, a range of mode activity driven by the sub-Alfv{\'e}nic (Vbeam/VA < 0.5) 80 kV neutral beams is found including beta induced Alfv{\'e}n acoustic eigenmodes, beta induced Alfv{\'e}n eigenmodes, reversed shear Alfv{\'e}n eigenmodes (RSAEs) and toroidicity induced Alfv{\'e}n eigenmodes (TAEs). Mode intermittency and possibly chirping appears to be more common than comparable positive triangularity and/or oval discharges but overall, the unstable spectra and mode amplitudes observed on magnetics, CO2 interferometry, and electron cyclotron emission in a set of matched positive and negative triangularity cases at moderate beam power is similar. Large levels of Alfv{\'e}n eigenmode induced fast ion transport are found in both positive and negative triangularity with up to 70% central fast ion pressure deficits relative to classical predictions early during the current ramp phase for discharges with 3 MW injected 80 kV neutral beam power. The deficit in both cases is reduced toward zero as the current penetrates and eventually reaches classical levels during current flattop with qmin≈ 1. Fast ion transport in negative triangularity plasmas measured using a beam modulation technique show very similar levels to those measured in oval plasmas over the range of tested beam powers (Pbeam≈ 2 7 MW). This similarity is found despite quite different unstable spectra in the highest beam power case where a mixture of coherent and quasi-coherent modes in the TAE frequency range are observed in negative triangularity and a spectrum of more typical narrowband TAEs and RSAEs is observed for the oval plasmas.",

keywords = "Alfven waves, MHD stability, fusion products effects, magnetohydrodynamic waves, plasma heating by particle beams, tokamaks",

author = "{Van Zeeland}, {M. A.} and Collins, {C. S.} and Heidbrink, {W. W.} and Austin, {M. E.} and Du, {X. D.} and Duarte, {V. N.} and A. Hyatt and G. Kramer and N. Gorelenkov and B. Grierson and D. Lin and A. Marinoni and G. McKee and C. Muscatello and C. Petty and C. Sung and Thome, {K. E.} and M. Walker and Zhu, {Y. B.}",

year = "2019",

month = jun,

day = "27",

doi = "10.1088/1741-4326/ab2488",

language = "English",

volume = "59",

journal = "Nuclear Fusion",

issn = "0029-5515",

publisher = "IOP Publishing",

number = "8",

}

Van Zeeland, MA, Collins, CS, Heidbrink, WW, Austin, ME, Du, XD, Duarte, VN, Hyatt, A, Kramer, G, Gorelenkov, N, Grierson, B, Lin, D, Marinoni, A, McKee, G, Muscatello, C, Petty, C, Sung, C, Thome, KE, Walker, M & Zhu, YB 2019, 'Alfvén eigenmodes and fast ion transport in negative triangularity DIII-D plasmas', Nuclear Fusion, vol. 59, no. 8, 086028. https://doi.org/10.1088/1741-4326/ab2488

TY - JOUR

T1 - Alfvén eigenmodes and fast ion transport in negative triangularity DIII-D plasmas

AU - Van Zeeland, M. A.

AU - Collins, C. S.

AU - Heidbrink, W. W.

AU - Austin, M. E.

AU - Du, X. D.

AU - Duarte, V. N.

AU - Hyatt, A.

AU - Kramer, G.

AU - Gorelenkov, N.

AU - Grierson, B.

AU - Lin, D.

AU - Marinoni, A.

AU - McKee, G.

AU - Muscatello, C.

AU - Petty, C.

AU - Sung, C.

AU - Thome, K. E.

AU - Walker, M.

AU - Zhu, Y. B.

PY - 2019/6/27

Y1 - 2019/6/27

N2 - The first energetic particle experiments in negative triangularity tokamak plasmas have been carried out on DIII-D. Alfvén eigenmode (AE) activity and associated fast ion transport comparable to that in positive triangularity is observed during the current ramp portion of all plasmas with early beam heating indicating negative triangularity does not confer a special advantage with respect to AE induced transport. In these discharges, a range of mode activity driven by the sub-Alfvénic (Vbeam/VA < 0.5) 80 kV neutral beams is found including beta induced Alfvén acoustic eigenmodes, beta induced Alfvén eigenmodes, reversed shear Alfvén eigenmodes (RSAEs) and toroidicity induced Alfvén eigenmodes (TAEs). Mode intermittency and possibly chirping appears to be more common than comparable positive triangularity and/or oval discharges but overall, the unstable spectra and mode amplitudes observed on magnetics, CO2 interferometry, and electron cyclotron emission in a set of matched positive and negative triangularity cases at moderate beam power is similar. Large levels of Alfvén eigenmode induced fast ion transport are found in both positive and negative triangularity with up to 70% central fast ion pressure deficits relative to classical predictions early during the current ramp phase for discharges with 3 MW injected 80 kV neutral beam power. The deficit in both cases is reduced toward zero as the current penetrates and eventually reaches classical levels during current flattop with qmin≈ 1. Fast ion transport in negative triangularity plasmas measured using a beam modulation technique show very similar levels to those measured in oval plasmas over the range of tested beam powers (Pbeam≈ 2 7 MW). This similarity is found despite quite different unstable spectra in the highest beam power case where a mixture of coherent and quasi-coherent modes in the TAE frequency range are observed in negative triangularity and a spectrum of more typical narrowband TAEs and RSAEs is observed for the oval plasmas.

AB - The first energetic particle experiments in negative triangularity tokamak plasmas have been carried out on DIII-D. Alfvén eigenmode (AE) activity and associated fast ion transport comparable to that in positive triangularity is observed during the current ramp portion of all plasmas with early beam heating indicating negative triangularity does not confer a special advantage with respect to AE induced transport. In these discharges, a range of mode activity driven by the sub-Alfvénic (Vbeam/VA < 0.5) 80 kV neutral beams is found including beta induced Alfvén acoustic eigenmodes, beta induced Alfvén eigenmodes, reversed shear Alfvén eigenmodes (RSAEs) and toroidicity induced Alfvén eigenmodes (TAEs). Mode intermittency and possibly chirping appears to be more common than comparable positive triangularity and/or oval discharges but overall, the unstable spectra and mode amplitudes observed on magnetics, CO2 interferometry, and electron cyclotron emission in a set of matched positive and negative triangularity cases at moderate beam power is similar. Large levels of Alfvén eigenmode induced fast ion transport are found in both positive and negative triangularity with up to 70% central fast ion pressure deficits relative to classical predictions early during the current ramp phase for discharges with 3 MW injected 80 kV neutral beam power. The deficit in both cases is reduced toward zero as the current penetrates and eventually reaches classical levels during current flattop with qmin≈ 1. Fast ion transport in negative triangularity plasmas measured using a beam modulation technique show very similar levels to those measured in oval plasmas over the range of tested beam powers (Pbeam≈ 2 7 MW). This similarity is found despite quite different unstable spectra in the highest beam power case where a mixture of coherent and quasi-coherent modes in the TAE frequency range are observed in negative triangularity and a spectrum of more typical narrowband TAEs and RSAEs is observed for the oval plasmas.

KW - Alfven waves

KW - MHD stability

KW - fusion products effects

KW - magnetohydrodynamic waves

KW - plasma heating by particle beams

KW - tokamaks

UR - http://www.scopus.com/inward/record.url?scp=85070912109&partnerID=8YFLogxK

U2 - 10.1088/1741-4326/ab2488

DO - 10.1088/1741-4326/ab2488

M3 - Article

AN - SCOPUS:85070912109

SN - 0029-5515

VL - 59

JO - Nuclear Fusion

JF - Nuclear Fusion

IS - 8

M1 - 086028

ER -

Alfvén eigenmodes and fast ion transport in negative triangularity DIII-D plasmas

Abstract

Keywords

UN SDGs

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