Predictive multi-channel integrated modeling of a reversed magnetic shear H-mode discharge with internal transport barrier in EAST

Shi, Shengyu; Chen, Jiale; Bourdelle, C.; Xiang, Jian; Wu, Mingfu; Zhang, Tao; Qian, J.; Garofalo, A. M.; Gao, Xiang; Wan, Yuanxi

doi:10.1088/1741-4326/ac32f0

Cited by 6 publications

(5 citation statements)

References 118 publications

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“…For the hybrid scenario discharge, the experimental density, temperature and toroidal rotation profiles of the bulk plasma at 4.65 s are used as the inputs to predict the core W transport. The modeling of the background plasmas, as usually performed with transport codes, has been done in the separate paper [74]. As can be seen in figure 6, the ion and electron temperature are relatively low (T i0 2.1 keV, T e0 1.7 keV).…”

Section: Theoretical Modeling Of Core W Transportmentioning

confidence: 99%

“…The central Mach number of D and W can be as high as 0.3 and 2.6, respectively. The safety factor q has been presented in reference [74], where a reverse magnetic shear q profile with minimum value q min 1 can be seen.…”

Section: Theoretical Modeling Of Core W Transportmentioning

confidence: 99%

“…The physics that determine the characteristics of the W transport, specifically, the dominant role of the neoclassical transport, have been preliminarily outlined in reference [74]. A detailed explanation will be given later in this paper.…”

Section: Main Reasons For W Accumulationmentioning

confidence: 99%

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Understanding core heavy impurity transport in a hybrid discharge on EAST

et al. 2022

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The behavior of heavy/high-Z impurity tungsten (W) in the core of hybrid (high normalized beta β_N plasmas) scenario on EAST with ITER-like divertor (ILD) is analyzed. W accumulation is often observed and seriously degrades the plasma performance (Xiang Gao et al 2017 Nucl. Fusion 57 056021). The dynamics of the W accumulation process of a hybrid discharge are examined considering the concurrent evolution of the background plasma parameters. It turns out that the toroidal rotation and density peaking of the bulk plasma are usually large in the central region, which is particularly prone to the W accumulation. A time slice during the W accumulation phase is modeled, accounting for both neoclassical and turbulent transport components of W, through NEO with poloidal asymmetry effects induced by toroidal rotation, and TGLF, respectively. This modeling reproduces the experimental observations of W accumulation and identifies the neoclassical inward convection/pinch velocity of W due to the large density peaking of the bulk plasma and toroidal rotation in the central region as one of the main reasons for the W accumulation. In addition, the NEO+TGLF+STRAHL modeling can not only predict the core W density profile but also closely reconstruct the radiated information mainly produced by W in the experiment.

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Section: Theoretical Modeling Of Core W Transportmentioning

confidence: 99%

Section: Theoretical Modeling Of Core W Transportmentioning

confidence: 99%

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Understanding core heavy impurity transport in a hybrid discharge on EAST

et al. 2022

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“…For W turbulent convection, there are several components including the thermo-diffusion, roto-diffusion, pure convection [44] (the centrifugal force effects on these terms are not considered in TGLF (low Mach number approximation) [38]). Based on the reference [45], in the condition of reversed magnetic shear, it is possible to make the turbulent convection reversed, but we have not achieved the large positive turbulent convection in the reversed magnetic shear region as shown in references [26,46]. The relative imbalance between the various turbulent convection terms depends on the local parameters sensitively.…”

Section: Conclusion and Discussionmentioning

confidence: 92%

Understanding core tungsten (W) transport and control in an improved high-performance fully non-inductive discharge on EAST

Shi¹,

Chen²,

Bourdelle³

et al. 2022

Nucl. Fusion

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The behavior of heavy/high-Z impurity tungsten (W) in an improved high-performance fully non-inductive discharge on EAST with ITER-like divertor (ILD) is analyzed. It is found that W could be well controlled. The causes of no W accumulation are clarified by analyzing the background plasma parameters and modeling the W transport. It turns out that the electron temperature (T_e) and its gradient are usually high while the toroidal rotation and density peaking of the bulk plasma are small. In this condition, the modeled W turbulent diffusion coefficient is big enough to offset the total turbulent and neoclassical pinch, so that W density profile for zero particle flux will not be very peaked. Combining NEO and TGLF for the W transport coefficient and the impurity transport code STRAHL, not only the core W density profile is predicted but also the radiated information mainly produced by W in the experiment can be closely reconstructed. At last, the physics of controlling W accumulation by electron cyclotron resonance heating (ECRH) is illustrated considering the effects of changed T_e by ECRH on ionization balance and transport of W. It shows that the change of ionization and recombination balance by changed T_e is not enough to explain the experimental observation of W behavior, which should be attributed to the changed W transport. By comparing the W transport coefficients in two kinds of plasmas with different T_e profiles, it is shown that high T_e and its gradient play a key role to generate large turbulent diffusion through increasing the growth rate of linear instability so that W accumulation is prevented.

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“…It is very important to investigate the toroidal rotational effects on W transport in the EAST because when the central toroidal rotational velocity attains about 50 km s −1 , which usually corresponds to a NBI-dominant heated H-mode discharge [67], core W accumulation has often been observed. Such an accumulation degrades the plasma performance and gives rise to radiative collapse or even leads to the loss of the H-mode.…”

Section: Dependence On Toroidal Rotationmentioning

confidence: 99%

Illustrating the physics of core tungsten (W) transport in a long-pulse steady-state H-mode discharge on EAST

Shi¹,

Chen²,

Xiang³

et al. 2022

Nucl. Fusion

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The behavior of core tungsten (W) in a pure radio frequency (RF) heated long-pulse steady-state H-mode discharge on experimental advanced superconducting tokamak (EAST) with ITER-like divertor (ILD) is analyzed with experimental diagnostics data and modeled with a combination of drift-kinetic neoclassical and gyro-fluid turbulent codes. In the stationary state, the experimental core line-averaged W concentration (C_W) is about 〖2×10〗^(-5), which is evaluated by the intensity of the W unresolved transition array (W-UTA) spectral structure in the region of 45-70 Å, composed of W^(27+)-W^(45+) line emissions through the spectroscopic method in extreme ultraviolet (EUV) region. W produces a peak of the radiated power density profile around normalized radius ρ~0.3. Therefore, W does not centrally accumulate in the experiment. A time slice of the stationary state is modeled, accounting for both neoclassical and turbulent transport components of W based on the self-consistent background plasma profiles simulated by TGYRO (J. Candy et al 2009 Phys. Plasmas 16 060704). It is found that turbulent transport dominates over neoclassical transport for W, what is more, turbulent diffusion coefficient is large enough to offset the sum of neoclassical and turbulent pinch (convection) velocity, so that the W density profile for zero particle flux will not be very peaked. Combining TGLF (G.M. Staebler et al 2017 Nucl. Fusion 57 066046) and NEO (E. Belli and J. Candy 2008 Plasma Phys. Control. Fusion 50 095010, 2012 Plasma Phys. Control. Fusion 54 015015) for the W transport coefficient with the impurity transport code STRAHL (R. Dux 2006 STRAHL User Manual), the experimental C_W and radiated information caused by W can be reproduced closely. In addition, the effect of toroidal rotation on the W transport is also clarified.

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Predictive multi-channel integrated modeling of a reversed magnetic shear H-mode discharge with internal transport barrier in EAST

Cited by 6 publications

References 118 publications

Understanding core heavy impurity transport in a hybrid discharge on EAST

Understanding core heavy impurity transport in a hybrid discharge on EAST

Understanding core tungsten (W) transport and control in an improved high-performance fully non-inductive discharge on EAST

Illustrating the physics of core tungsten (W) transport in a long-pulse steady-state H-mode discharge on EAST

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