A new model of the L–H transition and H-mode power threshold

Xingquan WU (伍兴权); Guosheng XU (徐国盛); Baonian WAN (万宝年); Jens Juul RASMUSSEN; Volker NAULIN; Anders Henry NIELSEN; Liang CHEN (陈良); Ran CHEN (陈冉); Ning YAN (颜宁); Linming SHAO (邵林明)

doi:10.1088/2058-6272/aabb9e

Plasma Science and Technology > 2018 > 20(9): 94003-094003. > DOI: 10.1088/2058-6272/aabb9e

Xingquan WU (伍兴权), Guosheng XU (徐国盛), Baonian WAN (万宝年), Jens Juul RASMUSSEN, Volker NAULIN, Anders Henry NIELSEN, Liang CHEN (陈良), Ran CHEN (陈冉), Ning YAN (颜宁), Linming SHAO (邵林明). A new model of the L–H transition and H-mode power threshold[J]. Plasma Science and Technology, 2018, 20(9): 94003-094003. DOI: 10.1088/2058-6272/aabb9e

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A new model of the L–H transition and H-mode power threshold

1 Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, People’s Republic of China 2 Department of Physics, Technical University of Denmark, Fysikvej, DK-2800 Kgs.-Lyngby, Denmark

Funds: This work was supported by National Natural Science Foundation of China under Contract Nos. 11575235 and 11422546, China Postdoctoral Science Foundation under Contract No. 2016M602043 and the National Magnetic Confinement Fusion Science Program of China under Con- tract No. 2015GB101002, Key Research Program of Frontier Sciences, CAS, Grant No. QYZDB-SSW-SLH001 and K C Wong Education Foundation.

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Received Date: January 10, 2018

Graphical Abstract

Abstract

Abstract

In order to understand the mechanism of the confinement bifurcation and H-mode power
threshold in magnetically confined plasma, a new dynamical model of the L–H transition based
on edge instability phase transition (EIPT) has been developed. With the typical plasma
parameters of the EAST tokamak, the self-consistent turbulence growth rate is analyzed using
the simplest case of pressure-driven ballooning-type instability, which indicates that the L–H
transition can be caused by the stabilization of the edge instability through EIPT. The weak
E×B flow shear in L-mode is able to increase the ion inertia of the electrostatic motion by
increasing the radial wave number of the tilted turbulence structures, which play an important
role for accelerating the trigger process of EIPT rather than directly to suppress the turbulent
transport. With the acceleration mechanism of E×B flow shear, fast L–H and H–L transitions
are demonstrated under the control of the input heating power. Due to the simplified scrape-off-
layer boundary condition applied, the ratio between the heating powers at the H–L and L–H
transition respectively differs from the ratio by Nusselt number. The results of the modeling
reveal a scaling of the power threshold of the L–H transition, P_L−H ∝ n^0.76 B ^0.8 for deuterium
plasma. It is found finite Larmor radius induces an isotope effect of the H-mode power threshold.
- L–H transition,
- power threshold,
- E × B flow shear,
- turbulence suppression,
- edge instability

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References (89)

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