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Title: Development of high poloidal beta, steady-state scenario with ITER-like tungsten divertor on EAST

Abstract

Recent experiments on EAST have achieved the first long pulse H-mode (61 s) with zero loop voltage and an ITER-like tungsten divertor, and have demonstrated access to broad plasma current profiles by increasing the density in fully-noninductive lower hybrid current-driven discharges. These long pulse discharges reach wall thermal and particle balance, exhibit stationary good confinement (H 98y2~1.1) with low core electron transport, and are only possible with optimal active cooling of the tungsten armors. In separate experiments, the electron density was systematically varied in order to study its effect on the deposition profile of the external lower hybrid current drive (LHCD), while keeping the plasma in fully-noninductive conditions and with divertor strike points on the tungsten divertor. A broadening of the current profile is found, as indicated by lower values of the internal inductance at higher density. A broad current profile is attractive because, among other reasons, it enables internal transport barriers at large minor radius, leading to improved confinement as shown in companion DIII-D experiments. These experiments strengthen the physics basis for achieving high performance, steady state discharges in future burning plasmas.

Authors:
 [1];  [2];  [2];  [2];  [2];  [2];  [2];  [2];  [3];  [4];  [2];  [5];  [2];  [4];  [2];  [6];  [2];  [1];  [1];  [1] more »;  [2];  [2];  [7];  [8];  [2];  [3];  [1];  [2];  [2] « less
  1. General Atomics, San Diego, CA (United States)
  2. Chinese Academy of Sciences (CAS), Hefei (China). Inst. of Plasma Physics
  3. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Plasma Science and Fusion Center
  4. Univ. of California, Los Angeles, CA (United States). Dept. of Physics and Astronomy
  5. Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
  6. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  7. Oak Ridge Associated Univ., Oak Ridge, TN (United States)
  8. Alternative Energies and Atomic Energy Commission (CEA), Saint-Paul-Les-Durance Cedex (France). Inst. de Recherche sur la Fusion par confinement Magnetique (IRFM)
Publication Date:
Research Org.:
General Atomics, San Diego, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Fusion Energy Sciences (FES) (SC-24)
OSTI Identifier:
1374823
Grant/Contract Number:
FC02-04ER54698; SC0010685; SC0010492; FG02-01ER54615; AC02-09CH11466; AC52-07NA27344
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Nuclear Fusion
Additional Journal Information:
Journal Volume: 57; Journal Issue: 7; Journal ID: ISSN 0029-5515
Publisher:
IOP Science
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; magnetic fusion; steady-state tokamak; current profile control; lower hybrid

Citation Formats

Garofalo, Andrea M., Gong, X. Z., Qian, J., Chen, J., Li, G., Li, K., Li, M. H., Zhai, X., Bonoli, P., Brower, D., Cao, L., Cui, L., Ding, S., Ding, W. X., Guo, W., Holcomb, Christopher, Huang, J., Hyatt, Alan, Lanctot, Matthew, Lao, Lang L., Liu, H., Lyu, B., McClenaghan, J., Peysson, Y., Ren, Q., Shiraiwa, S., Solomon, Wayne, Zang, Q., and Wan, B. Development of high poloidal beta, steady-state scenario with ITER-like tungsten divertor on EAST. United States: N. p., 2017. Web. doi:10.1088/1741-4326/aa7186.
Garofalo, Andrea M., Gong, X. Z., Qian, J., Chen, J., Li, G., Li, K., Li, M. H., Zhai, X., Bonoli, P., Brower, D., Cao, L., Cui, L., Ding, S., Ding, W. X., Guo, W., Holcomb, Christopher, Huang, J., Hyatt, Alan, Lanctot, Matthew, Lao, Lang L., Liu, H., Lyu, B., McClenaghan, J., Peysson, Y., Ren, Q., Shiraiwa, S., Solomon, Wayne, Zang, Q., & Wan, B. Development of high poloidal beta, steady-state scenario with ITER-like tungsten divertor on EAST. United States. doi:10.1088/1741-4326/aa7186.
Garofalo, Andrea M., Gong, X. Z., Qian, J., Chen, J., Li, G., Li, K., Li, M. H., Zhai, X., Bonoli, P., Brower, D., Cao, L., Cui, L., Ding, S., Ding, W. X., Guo, W., Holcomb, Christopher, Huang, J., Hyatt, Alan, Lanctot, Matthew, Lao, Lang L., Liu, H., Lyu, B., McClenaghan, J., Peysson, Y., Ren, Q., Shiraiwa, S., Solomon, Wayne, Zang, Q., and Wan, B. Wed . "Development of high poloidal beta, steady-state scenario with ITER-like tungsten divertor on EAST". United States. doi:10.1088/1741-4326/aa7186.
@article{osti_1374823,
title = {Development of high poloidal beta, steady-state scenario with ITER-like tungsten divertor on EAST},
author = {Garofalo, Andrea M. and Gong, X. Z. and Qian, J. and Chen, J. and Li, G. and Li, K. and Li, M. H. and Zhai, X. and Bonoli, P. and Brower, D. and Cao, L. and Cui, L. and Ding, S. and Ding, W. X. and Guo, W. and Holcomb, Christopher and Huang, J. and Hyatt, Alan and Lanctot, Matthew and Lao, Lang L. and Liu, H. and Lyu, B. and McClenaghan, J. and Peysson, Y. and Ren, Q. and Shiraiwa, S. and Solomon, Wayne and Zang, Q. and Wan, B.},
abstractNote = {Recent experiments on EAST have achieved the first long pulse H-mode (61 s) with zero loop voltage and an ITER-like tungsten divertor, and have demonstrated access to broad plasma current profiles by increasing the density in fully-noninductive lower hybrid current-driven discharges. These long pulse discharges reach wall thermal and particle balance, exhibit stationary good confinement (H98y2~1.1) with low core electron transport, and are only possible with optimal active cooling of the tungsten armors. In separate experiments, the electron density was systematically varied in order to study its effect on the deposition profile of the external lower hybrid current drive (LHCD), while keeping the plasma in fully-noninductive conditions and with divertor strike points on the tungsten divertor. A broadening of the current profile is found, as indicated by lower values of the internal inductance at higher density. A broad current profile is attractive because, among other reasons, it enables internal transport barriers at large minor radius, leading to improved confinement as shown in companion DIII-D experiments. These experiments strengthen the physics basis for achieving high performance, steady state discharges in future burning plasmas.},
doi = {10.1088/1741-4326/aa7186},
journal = {Nuclear Fusion},
number = 7,
volume = 57,
place = {United States},
year = {Wed Jun 07 00:00:00 EDT 2017},
month = {Wed Jun 07 00:00:00 EDT 2017}
}

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  • In this study, transport modeling of a proposed ITER steady-state scenario based on DIII-D high poloidal-beta (more » $${{\beta}_{p}}$$ ) discharges finds that ITB formation can occur with either sufficient rotation or a negative central shear q-profile. The high $${{\beta}_{p}}$$ scenario is characterized by a large bootstrap current fraction (80%) which reduces the demands on the external current drive, and a large radius internal transport barrier which is associated with excellent normalized confinement. Modeling predictions of the electron transport in the high $${{\beta}_{p}}$$ scenario improve as $${{q}_{95}}$$ approaches levels similar to typical existing models of ITER steady-state and the ion transport is turbulence dominated. Typical temperature and density profiles from the non-inductive high $${{\beta}_{p}}$$ scenario on DIII-D are scaled according to 0D modeling predictions of the requirements for achieving a $Q=5$ steady-state fusion gain in ITER with 'day one' heating and current drive capabilities. Then, TGLF turbulence modeling is carried out under systematic variations of the toroidal rotation and the core q-profile. A high bootstrap fraction, high $${{\beta}_{p}}$$ scenario is found to be near an ITB formation threshold, and either strong negative central magnetic shear or rotation in a high bootstrap fraction are found to successfully provide the turbulence suppression required to achieve $Q=5$.« less
    Cited by 1
  • Cited by 5
  • Systematic experimental and modeling investigations on DIII-D and EAST show attractive transport properties of fully non-inductive high β p plasmas. Experiments on DIII-D show that the large-radius internal transport barrier (ITB), a key feature providing excellent confinement in the high β p regime, is maintained when the scenario is extended from q 95 ~ 12 to 7 and from rapid to near-zero toroidal rotation. The robustness of confinement versus rotation was predicted by gyro fluid modeling showing dominant neoclassical ion energy transport even without E B shear effect. The physics mechanism of turbulence suppression, we found, is the Shafranov shift,more » which is essential and sets a β p threshold for large-radius ITB formation in the high β p scenario on DIII-D. This is confirmed by two different parameter-scan experiments, one for β N scan and the other for q 95 scan. They both give the same p threshold at 1.9 in the experiment. Furthermore, the experiment trend of increasing thermal transport with decreasing β p is consistent with transport modeling. The very first step of extending high β p scenario on DIII-D to long pulse on EAST is to establish long pulse H-mode with ITB on EAST. Our paper shows the first 61 sec fully non-inductive H-mode with stationary ITB feature and actively cooled ITER-like tungsten divertor in the very recent EAST experiment. The successful use of lower hybrid wave (LWH) as a key tool to optimize current profile in EAST experiment is also introduced. Results show that as the electron density is increased, the fully non-inductive current profile broadens on EAST. The improved understanding and modeling capability is also used to develop advanced scenarios for CFETR. These results provide encouragement that the high β p regime can be extended to lower safety factor and very low rotation, providing a potential path to high performance steady state operation in future devices.« less
  • Recent studies on the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] have elucidated key aspects of the dependence of stability, confinement, and density control on the plasma magnetic configuration, leading to the demonstration of nearly noninductive operation for >1 s with pressure 30% above the ideal no-wall stability limit. Achieving fully noninductive tokamak operation requires high pressure, good confinement, and density control through divertor pumping. Plasma geometry affects all of these. Ideal magnetohydrodynamics modeling of external kink stability suggests that it may be optimized by adjusting the shape parameter known as squareness ({zeta}). Optimizing kink stability leadsmore » to an increase in the maximum stable pressure. Experiments confirm that stability varies strongly with {zeta}, in agreement with the modeling. Optimization of kink stability via {zeta} is concurrent with an increase in the H-mode edge pressure pedestal stability. Global energy confinement is optimized at the lowest {zeta} tested, with increased pedestal pressure and lower core transport. Adjusting the magnetic divertor balance about a double-null configuration optimizes density control for improved noninductive auxiliary current drive. The best density control is obtained with a slight imbalance toward the divertor opposite the ion grad(B) drift direction, consistent with modeling of these effects. These optimizations have been combined to achieve noninductive current fractions near unity for over 1 s with normalized pressure of 3.5<{beta}{sub N}<3.9, bootstrap current fraction of >65%, and a normalized confinement factor of H{sub 98(y,2)}{approx}1.5.« less
  • Recent studies on the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)] have elucidated key aspects of the dependence of stability, confinement, and density control on the plasma magnetic configuration, leading to the demonstration of nearly noninductive operation for >1 s with pressure 30% above the ideal no-wall stability limit. Achieving fully noninductive tokamak operation requires high pressure, good confinement, and density control through divertor pumping. Plasma geometry affects all of these. Ideal magnetohydrodynamics modeling of external kink stability suggests that it may be optimized by adjusting the shape parameter known as squareness ({zeta}). Optimizing kink stability leadsmore » to an increase in the maximum stable pressure. Experiments confirm that stability varies strongly with {zeta}, in agreement with the modeling. Optimization of kink stability via {zeta} is concurrent with an increase in the H-mode edge pressure pedestal stability. Global energy confinement is optimized at the lowest {zeta} tested, with increased pedestal pressure and lower core transport. Adjusting the magnetic divertor balance about a double-null configuration optimizes density control for improved noninductive auxiliary current drive. The best density control is obtained with a slight imbalance toward the divertor opposite the ion grad(B) drift direction, consistent with modeling of these effects. These optimizations have been combined to achieve noninductive current fractions near unity for over 1 s with normalized pressure of 3.5<{beta}{sub N}<3.9, bootstrap current fraction of >65%, and a normalized confinement factor of H{sub 98(y,2)}{approx_equal}1.5.« less