Evaluating the effects of tungsten on CFETR phase I performance

Shi, Shengyu; Xiang, Jian; Chan, V. S.; Gao, Xiang; Liu, Xiaoju; Shi, Nan; Chen, Jiale; Liu, Li; Wu, Mengfan; Zhu, Yiren; Team, Cfetr Physics

doi:10.1088/1741-4326/aae397

“…Since electron particle transport can be driven not only by normalized electron density gradient a/L ne , but also by coupling with the energy transport channel, we cannot use a simple form like (equation 1) to represent turbulent electron particle flux. The following more representative equation for electron particle flux is used [38]: (5) In this equation, positive Γ means outward particle flux, D Te and D Ti are non-diagonal turbulent electron particle transport coefficients related to a/L Te and a/L Ti respectively, while the 'residual' term, which is composed of the roto-diffusion term and other pure pinch terms, will be left out of our discussion. According to this equation, some important information can be obtained through scan over the normalized 5.…”

Section: Foot Regionmentioning

confidence: 99%

“…Comprehensive physics and engineering design for China Fusion Engineering Test Reactor (CFETR), with target fusion power of 1 GW and fusion gain Q > 10 to demonstrate tritium self-sufficiency and reactor relevant conditions, is underway [1]. The physics design covers a broad range of topics, such as improving the core plasma performance with optimization of heating and current drive [2,3], and evaluation of impurity effects on the CFETR fusion performance [4,5]. In the boundary, heat and particle exhaust solutions under conditions more severe than ITER are explored [6,7].…”

Section: Introductionmentioning

confidence: 99%

Effects of triangularity on the fusion performance of CFETR

Zhou

¹

,

Chen

²

,

Chan

³

et al. 2020

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An important task of the China Fusion Engineering Test Reactor physics design is to develop operation scenarios with high fusion power (1 GW), high bootstrap current fraction for steady-state and a plasma edge compatible with heat and particle exhaust. To achieve these goals, triangularity (δ) effects on the fusion performance of two candidate scenarios, with or without reversed magnetic shear (RS), namely conventional H-mode and RS H-mode, are evaluated using core-edge coupled integrated modeling in this paper. For fixed pedestal density, it is shown that higher δ is favorable for higher fusion performance in the conventional H-mode scenario while the fusion performance decreases with increasing δ in the RS H-mode scenario. In conventional H-mode, the higher fusion performance at high δ mainly comes from a higher pedestal temperature as predicted by EPED in combination with stiff core kinetic profiles. In the RS H-mode scenario with a local reversed shear region, the profiles are non-stiff and a strong internal transport barrier (ITB) exists at low δ. This results in higher density and temperature inside the ITB for low δ, leading to higher fusion power. If the pedestal temperature is kept fixed, in both scenarios the significant increase in pedestal density, which extends into the core, dominates at high δ and leads to much higher fusion power. For conventional H-mode, destabilization from increasing δ is partially balanced by stabilization due to increasing ν*. Since the normalized heat sources are quite similar, it results in minimal changes in the temperature profiles except for the lowest density case. For RS H-mode, destabilization from increasing δ is approximately balanced by stabilization due to increasing ν* in foot region, but a strong temperature ITB is still evident for low δ. The ability to take advantage of the high pedestal density in conventional H-mode and reversed shear scenario depends on its compatibility with edge density requirements from efficient heat and particle exhaust. Transport analysis is presented to elucidate the roles of δ, collisionality and magnetic shear in altering the profiles and the ITB, which contribute to the different behavior in the two scenarios.

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“…It is found that the neoclassical transport dominates over turbulent transport for W and neoclassical pinch of W causes its central accumulation. This could be understood as: in the region of ρ < 0.2 will enlarge the factor of poloidal asymmetries of heavy impurities, which could enhance the neoclassical transport of these species by several times, especially for the negative neoclassical convection [77][78][79][80][111][112][113][114][115][116][117].…”

Section: Simulated the Core W Transportmentioning

confidence: 99%

“…(a) Background turbulence (neoclassical transport) is weak (strong) in the ITB region (ρ < 0.4) as shown in figures 16 and 18, and ITG turbulent mode is the dominant mode as can be seen in figure16and reference[58]. These are not beneficial for removing core heavy impurities[79,80,[111][112][113][114][115][116][117] by increasing the turbulent diffusion. (b) Peaked main ion profile (n D ) mainly contributed by beam particle source (figures 9 and 11) will lead to the large negative neoclassical convection [77-80, 111-117].…”

mentioning

confidence: 99%

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

Shi

¹

,

Chen

²

,

Bourdelle

³

et al. 2021

Self Cite

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A reversed magnetic shear high plasma performance H-mode discharge with internal transport barrier (ITB) has been realized and modeled on experimental advanced superconducting tokamak (EAST) in deuterium (D) plasmas with an ITER-like tungsten (W) upper divertor. In this shot (#71326), the dimensionless parameter G ( H 89 β N / q 95 2 ) can reach to 0.25 (H 89 ⩽ 2, β N ⩽ 2, q 95 ∼ 4, I p ⩽ 450 kA, B T ⩽ 1.6 T). The ITB has been observed in the channels of particle (electron density n e), electron and ion temperature (T e and T i) and toroidal rotation velocity (V t). However, in the formation process of V t and n e ITBs, the heavy impurities accumulate in the core plasmas, which may be one of the most important reasons for the limitation of the improvement of plasma performance. A time slice (t = 4.65 s) of the high plasma performance phase with n e, T i and V t ITBs has been analyzed. It is found that the position of minimum safety factor (q min) is at about normalized radius ρ = 0.4 where may be the location of ion ITB foot, during equilibrium reconstruction from EFIT using external magnetic and internal polarimeter-INTferometer (POINT) measurement constraints. Based on this equilibrium, the source is self-consistently calculated by ONETWO and NUBEAM. Then the n e, T e, T i and V t have been modeled predictively and simultaneously by TGYRO utilizing the reconstructed equilibrium, the self-consistent source and the experimental radiated power for the first time in EAST. This modeling well reproduces the experimental n e and T i profiles in the reversed magnetic shear plasmas. In addition, it is shown that reversed magnetic shear rather than shear of radial electric field (E r) mainly produced by V t plays a key role to the formation of n e and T i ITBs. The reasons for central accumulation of W impurity are also clarified by computing both neoclassical and turbulent transport components of W. It turns out that the neoclassical transport dominates over turbulent transport for W and neoclassical pinch of W causes its central accumulation.

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