Effect of del B drift on the H-mode power threshold in upper single null plasmas with ITER-like tungsten divertor on EAST

L. Chen, G. S. Xu*, Ning Yan, A. H. Nielsen, J. B. Liu, W. Gao, R. Chen, H. Qu, F. Ding, H. M. Mao, Zhenhua Sun, L. Zhang, M. H. Li, W. Zhang, G. H. Hu, L. M. Shao, X. Q. Wu, H. F. Du, J. C. Xu, Y. L. LiN. Zhao, H. Lan, Y. Ye, H. Zhang, H. Q. Wang, S. Y. Ding, L. Wang, B. N. Wan, EAST Team

*Corresponding author for this work

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Abstract

In this paper, we will experimentally investigate the power threshold (PL-H) in upper single null plasmas with an ITER-like tungsten divertor under different ∇B drift directions on EAST [F. Ding et al., Commissioning and PSI Behavior of the ITER-Like W/Cu Divertor in EAST 22nd PSI, Rome (2016)]. The power threshold for the low (L) to high (H) confinement mode has a clear and positive toroidal magnetic field, BT, dependence when the ∇ B drift points toward the primary X-point (Bx∇B↑). A factor of 2-3 increase in PL-H is observed for the ∇B drift away from the primary X-point (Bx∇B↓). The edge and core impurities quantified by spectroscopy measurements show comparable levels for the transitions for both drift directions. On the other hand, it is found that the divertor Dα emission just prior to the L-H transition is lower for Bx∇B↑, compared with that for Bx∇B↓. The upper in-out divertor asymmetry, as manifested by particle fluxes measured by the divertor triple Langmuir probe, is most marked for Bx∇B↓, and with significantly more particle flux to the outer divertor. The reversing field increases the particle flux into the upper inner and lower outer divertor, reducing the in-out asymmetry. One important distinction between the two field directions has been observed, with respect to the amplitude of the scrape-off layer (SOL) parallel flow. A dedicated experiment under similar target plasma conditions shows a lower SOL density and thus a steeper density gradient slightly inside the separatrix, where a lower PL-H is found for the Bx∇B↑, compared to that for Bx∇B↓. We, therefore, conclude that the fielddependent SOL plasma conditions play an important role in the transition physics.
Original languageEnglish
Article number072504
JournalPhysics of Plasmas
Volume25
Issue number7
Number of pages12
ISSN1070-664X
DOIs
Publication statusPublished - 2018

Cite this

Chen, L. ; Xu, G. S. ; Yan, Ning ; Nielsen, A. H. ; Liu, J. B. ; Gao, W. ; Chen, R. ; Qu, H. ; Ding, F. ; Mao, H. M. ; Sun, Zhenhua ; Zhang, L. ; Li, M. H. ; Zhang, W. ; Hu, G. H. ; Shao, L. M. ; Wu, X. Q. ; Du, H. F. ; Xu, J. C. ; Li, Y. L. ; Zhao, N. ; Lan, H. ; Ye, Y. ; Zhang, H. ; Wang, H. Q. ; Ding, S. Y. ; Wang, L. ; Wan, B. N. ; Team, EAST. / Effect of del B drift on the H-mode power threshold in upper single null plasmas with ITER-like tungsten divertor on EAST. In: Physics of Plasmas. 2018 ; Vol. 25, No. 7.
@article{913f73bcf07248e0b54aaa77c72afe8a,
title = "Effect of del B drift on the H-mode power threshold in upper single null plasmas with ITER-like tungsten divertor on EAST",
abstract = "In this paper, we will experimentally investigate the power threshold (PL-H) in upper single null plasmas with an ITER-like tungsten divertor under different ∇B drift directions on EAST [F. Ding et al., Commissioning and PSI Behavior of the ITER-Like W/Cu Divertor in EAST 22nd PSI, Rome (2016)]. The power threshold for the low (L) to high (H) confinement mode has a clear and positive toroidal magnetic field, BT, dependence when the ∇ B drift points toward the primary X-point (Bx∇B↑). A factor of 2-3 increase in PL-H is observed for the ∇B drift away from the primary X-point (Bx∇B↓). The edge and core impurities quantified by spectroscopy measurements show comparable levels for the transitions for both drift directions. On the other hand, it is found that the divertor Dα emission just prior to the L-H transition is lower for Bx∇B↑, compared with that for Bx∇B↓. The upper in-out divertor asymmetry, as manifested by particle fluxes measured by the divertor triple Langmuir probe, is most marked for Bx∇B↓, and with significantly more particle flux to the outer divertor. The reversing field increases the particle flux into the upper inner and lower outer divertor, reducing the in-out asymmetry. One important distinction between the two field directions has been observed, with respect to the amplitude of the scrape-off layer (SOL) parallel flow. A dedicated experiment under similar target plasma conditions shows a lower SOL density and thus a steeper density gradient slightly inside the separatrix, where a lower PL-H is found for the Bx∇B↑, compared to that for Bx∇B↓. We, therefore, conclude that the fielddependent SOL plasma conditions play an important role in the transition physics.",
author = "L. Chen and Xu, {G. S.} and Ning Yan and Nielsen, {A. H.} and Liu, {J. B.} and W. Gao and R. Chen and H. Qu and F. Ding and Mao, {H. M.} and Zhenhua Sun and L. Zhang and Li, {M. H.} and W. Zhang and Hu, {G. H.} and Shao, {L. M.} and Wu, {X. Q.} and Du, {H. F.} and Xu, {J. C.} and Li, {Y. L.} and N. Zhao and H. Lan and Y. Ye and H. Zhang and Wang, {H. Q.} and Ding, {S. Y.} and L. Wang and Wan, {B. N.} and EAST Team",
year = "2018",
doi = "10.1063/1.5033983",
language = "English",
volume = "25",
journal = "Physics of Plasmas",
issn = "1070-664X",
publisher = "American Institute of Physics",
number = "7",

}

Chen, L, Xu, GS, Yan, N, Nielsen, AH, Liu, JB, Gao, W, Chen, R, Qu, H, Ding, F, Mao, HM, Sun, Z, Zhang, L, Li, MH, Zhang, W, Hu, GH, Shao, LM, Wu, XQ, Du, HF, Xu, JC, Li, YL, Zhao, N, Lan, H, Ye, Y, Zhang, H, Wang, HQ, Ding, SY, Wang, L, Wan, BN & Team, EAST 2018, 'Effect of del B drift on the H-mode power threshold in upper single null plasmas with ITER-like tungsten divertor on EAST', Physics of Plasmas, vol. 25, no. 7, 072504. https://doi.org/10.1063/1.5033983

Effect of del B drift on the H-mode power threshold in upper single null plasmas with ITER-like tungsten divertor on EAST. / Chen, L.; Xu, G. S.; Yan, Ning; Nielsen, A. H.; Liu, J. B.; Gao, W.; Chen, R.; Qu, H.; Ding, F.; Mao, H. M.; Sun, Zhenhua; Zhang, L.; Li, M. H.; Zhang, W.; Hu, G. H.; Shao, L. M.; Wu, X. Q.; Du, H. F.; Xu, J. C.; Li, Y. L.; Zhao, N.; Lan, H.; Ye, Y.; Zhang, H.; Wang, H. Q.; Ding, S. Y.; Wang, L.; Wan, B. N.; Team, EAST.

In: Physics of Plasmas, Vol. 25, No. 7, 072504, 2018.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Effect of del B drift on the H-mode power threshold in upper single null plasmas with ITER-like tungsten divertor on EAST

AU - Chen, L.

AU - Xu, G. S.

AU - Yan, Ning

AU - Nielsen, A. H.

AU - Liu, J. B.

AU - Gao, W.

AU - Chen, R.

AU - Qu, H.

AU - Ding, F.

AU - Mao, H. M.

AU - Sun, Zhenhua

AU - Zhang, L.

AU - Li, M. H.

AU - Zhang, W.

AU - Hu, G. H.

AU - Shao, L. M.

AU - Wu, X. Q.

AU - Du, H. F.

AU - Xu, J. C.

AU - Li, Y. L.

AU - Zhao, N.

AU - Lan, H.

AU - Ye, Y.

AU - Zhang, H.

AU - Wang, H. Q.

AU - Ding, S. Y.

AU - Wang, L.

AU - Wan, B. N.

AU - Team, EAST

PY - 2018

Y1 - 2018

N2 - In this paper, we will experimentally investigate the power threshold (PL-H) in upper single null plasmas with an ITER-like tungsten divertor under different ∇B drift directions on EAST [F. Ding et al., Commissioning and PSI Behavior of the ITER-Like W/Cu Divertor in EAST 22nd PSI, Rome (2016)]. The power threshold for the low (L) to high (H) confinement mode has a clear and positive toroidal magnetic field, BT, dependence when the ∇ B drift points toward the primary X-point (Bx∇B↑). A factor of 2-3 increase in PL-H is observed for the ∇B drift away from the primary X-point (Bx∇B↓). The edge and core impurities quantified by spectroscopy measurements show comparable levels for the transitions for both drift directions. On the other hand, it is found that the divertor Dα emission just prior to the L-H transition is lower for Bx∇B↑, compared with that for Bx∇B↓. The upper in-out divertor asymmetry, as manifested by particle fluxes measured by the divertor triple Langmuir probe, is most marked for Bx∇B↓, and with significantly more particle flux to the outer divertor. The reversing field increases the particle flux into the upper inner and lower outer divertor, reducing the in-out asymmetry. One important distinction between the two field directions has been observed, with respect to the amplitude of the scrape-off layer (SOL) parallel flow. A dedicated experiment under similar target plasma conditions shows a lower SOL density and thus a steeper density gradient slightly inside the separatrix, where a lower PL-H is found for the Bx∇B↑, compared to that for Bx∇B↓. We, therefore, conclude that the fielddependent SOL plasma conditions play an important role in the transition physics.

AB - In this paper, we will experimentally investigate the power threshold (PL-H) in upper single null plasmas with an ITER-like tungsten divertor under different ∇B drift directions on EAST [F. Ding et al., Commissioning and PSI Behavior of the ITER-Like W/Cu Divertor in EAST 22nd PSI, Rome (2016)]. The power threshold for the low (L) to high (H) confinement mode has a clear and positive toroidal magnetic field, BT, dependence when the ∇ B drift points toward the primary X-point (Bx∇B↑). A factor of 2-3 increase in PL-H is observed for the ∇B drift away from the primary X-point (Bx∇B↓). The edge and core impurities quantified by spectroscopy measurements show comparable levels for the transitions for both drift directions. On the other hand, it is found that the divertor Dα emission just prior to the L-H transition is lower for Bx∇B↑, compared with that for Bx∇B↓. The upper in-out divertor asymmetry, as manifested by particle fluxes measured by the divertor triple Langmuir probe, is most marked for Bx∇B↓, and with significantly more particle flux to the outer divertor. The reversing field increases the particle flux into the upper inner and lower outer divertor, reducing the in-out asymmetry. One important distinction between the two field directions has been observed, with respect to the amplitude of the scrape-off layer (SOL) parallel flow. A dedicated experiment under similar target plasma conditions shows a lower SOL density and thus a steeper density gradient slightly inside the separatrix, where a lower PL-H is found for the Bx∇B↑, compared to that for Bx∇B↓. We, therefore, conclude that the fielddependent SOL plasma conditions play an important role in the transition physics.

U2 - 10.1063/1.5033983

DO - 10.1063/1.5033983

M3 - Journal article

VL - 25

JO - Physics of Plasmas

JF - Physics of Plasmas

SN - 1070-664X

IS - 7

M1 - 072504

ER -