Realization of thousand-second improved confinement plasma with Super I-mode in Tokamak EAST

Song, Yuntao; Zou, X. L.; Gong, Xianzu; Bécoulet, A.; Buttery, R. J.; Bonoli, P. T.; Hoang, T.; Maingi, R.; Qian, J.; Zhong, Xing; Liu, A.D.; Li, Erzhong; Ding, Rui; Huang, J.; Zang, Qing; Liu, Haiqing; Wang, Liang; Zhang, Ling; Li, G.; Sun, Yuan; Garofalo, A. M.; Osborne, T.H.; Leonard, A. W.; Baek, Seung Gyou; Wallace, G. M.; Xu, Liqing; Zhang, Bin; Wang, Shouxin; Chu, Yuqi; Zhang, Tao; Duan, Yanmin; Lian, H.; Zhang, Xuexi; Jin, Yifei; Zeng, Long; Lyu, Bo; Xiao, B. J.; Huang, Yao; Wang, Yong; Shen, Biao; Xiang, Nong; Wu, Yu; Wu, Ji; Wang, Xiaojie; Ding, Bojiang; Li, Miaohui; Zhang, Xinjun; Qin, Chengming; Wang, Xi; Zhang, Jian; Huang, Liansheng; Yao, Damao; Hu, Yanlan; Zuo, Guizhong; Yuan, Q.P.; Zhou, Zhiwei; Wang, M.; Xu, Handong; Xie, Yahong; Wang, Zhengchu; Chen, Jun-ling; Xu, G. S.; Hu, Jiansheng; Lü, Kun; Liu, Fukun; Xin-chao, WU; Wan, Baonian; Li, Jiangang

doi:10.1126/sciadv.abq5273

Cited by 46 publications

(34 citation statements)

References 70 publications

(48 reference statements)

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“…The heat load on the edge-beveled W plate was decreased by 36% after rough calculation using an optical approximation of the heat flux distribution [24]. No visible damage was observed and inspected after the following winter plasma campaign of 2021, and EAST also achieved the longest pulse discharge (#106915) [49]. However, two new melting locations on the sharp edge of the beveled W plates were found after the spring campaign of 2022.…”

Section: Severe Melting On W/cu Flat-type Components At Horizontal Ta...mentioning

confidence: 98%

In situ melting phenomena on W plasma-facing components for lower divertor during long-pulse plasma operations in EAST

et al. 2023

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Tungsten (W) is one of the most promising plasma-facing materials (PFMs) for future fusion device. Although its melting point is the highest among all the metals, it still has great risk of melting under extremely high plasma heat fluxes, which is a big concern for the ITER and future reactors. Actively-cooled W plasma-facing components (PFCs) with both monoblocks and flat-type structure have been successfully installed in the lower divertor of the EAST tokamak since 2021, which provide a good opportunity for direct comparison of damage mechanism for the two types of PFCs. Various in-situ melting phenomena on the lower divertor have been observed by CCD cameras, which are further verified by Post-mortem inspections. Severe melting even exfoliation of the edge beveled W plates on some W/Cu flat-type components at horizontal outer targets were observed. A large number of droplets were ejected during long-pulse operations, which induced the significant increase of W impurity and total irradiation in the core plasma, and thus greatly deteriorated the plasma performance and even cause disruptions. Two different shaping structures of flat-type PFCs show different position of melting and corresponding mechanisms. Few slight melting has been found on the sharp leading edges of W/Cu monoblocks at the inter-cassette modules for horizontal targets with small droplets ejection, which is much improved compared to that occurred on the upper W divertor, illustrating that the application of large-sized bevel chamfer at inter-cassette modules was generally effective. In addition, an unexpected melting phenomenon on the dome plate was attributed to the extreme transient heat flux during disruption with runaway electrons. The application of both types of W/Cu PFCs for divertor provides important experiences and lessons for engineering design and optimization of divertor PFCs in future fusion devices.

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Section: Severe Melting On W/cu Flat-type Components At Horizontal Ta...mentioning

confidence: 98%

In situ melting phenomena on W plasma-facing components for lower divertor during long-pulse plasma operations in EAST

et al. 2023

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“…In 2014, a 4.6 GHz/6.0 MW high power system (referred to as LH2) with a FAM launcher was developed. Significant progress has been achieved recently with the combination of LH2 and Electron Cyclotron (EC) waves, including 1056 s I-mode (injected LH energy ∼1.1 GJ) [11] and 403 s H-mode [12] plasmas. Other parameters for I-(H) mode are: P LH2 = 1.1 (1.6) MW, P EC = 0.55 (1.75) MW, I p = 330 (300) kA, ne = 1.8 (3.6) × 10 19 m −3 .…”

Section: Introductionmentioning

confidence: 99%

Design and analysis of a PAM launcher at 4.6 GHz for a new LHCD system on EAST

Li,

Liu,

Yang

et al. 2024

Nucl. Fusion

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To improve the current drive (CD) capability in long-pulse (up to ~ 1000 s) H-mode operation, it has been decided to develop a new lower hybrid current drive (LHCD) system at 4.6 GHz with an active cooling passive active multijunction (PAM) launcher on EAST. In this paper, both the RF and the physical properties of this PAM are studied numerically. The same nominal parallel refractive index (N|| = k||c/ω, where k|| is the parallel wavenumber, c the velocity of light, and ω the wave frequency) of 2.04 as the existing 4.6 GHz full active multijunction (FAM) is chosen. Ray-tracing calculations indicate that good accessibility could be achieved when the LH waves radiate with this nominal N|| in typical long-pulse H-mode plasmas. The coupling performance in terms of power reflection coefficient (RC), power spectrum, maximum electric field, power directivity (DP) and global CD capability is evaluated with the ALOHA code based on the linear coupling theory. Good coupling performance with averaged RC ≦ 1% and DP ~ 70% could be expected with the density (ne) in front of the PAM close to the cut-off value (ne_co). The simulated RC remains below 6.5% over a wide density range 0.5 ≦ ne/ne_co ≦ 10, which is similar to the plasma edge conditions produced by edge localized mode (ELM) activity. A detailed comparison with the existing 4.6 GHz FAM launcher is also performed.

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“…LHCD system is also proposed on ITER [18] and CFETR [19] for off-axis current profile control. [23], and a super I-mode plasma characterized by both edge transport barriers and internal transport barriers with a pulse length of 1056 s was achieved recently (other parameters are: I p = 330 kA, ne = 1.8 × 10 19 m −3 , divertor configuration) [24].…”

Section: Introductionmentioning

confidence: 99%

Plasma heating by electron cyclotron wave and the temperature effects on lower hybrid current drive on EAST

Xu²,

Wang³

et al. 2023

Nucl. Fusion

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This paper presents the progress in the long - pulse operation of the electron cyclotron (EC) system and the achievements in high - electron temperature plasmas by the combined EC and lower hybrid (LH) waves heating since the EC system was built in 2015. An electron temperature of up to 12 keV with a duration over 100 s was realized by the simultaneous heating of EC and LH waves at the line-averaged density n ̅_e ~ 1.8 *10^19/m^3. The plasma heating effect strongly depends on the location of EC power deposition. H-mode plasmas with solely EC wave auxiliary heating have been obtained on EAST for the first time. These H-mode discharges show an enhanced confinement factor H98(y,2) around 1.0, which is higher than the previous H-mode using LH power alone [G.S. Xu et al Nucl. Fusion 51 (2011) 072001]. The total heating power is very close to the threshold value for L-H transition according to the international tokamak scaling. In addition to the temperature effects inside the separatrix, higher electron temperature produced by EC wave is found to reduce the LH power loss in the scrape-off layer (SOL) due to collisional absorption, which is beneficial to further increase the lower hybrid current drive (LHCD) efficiency. Ray-tracing/Fokker-Planck modeling results indicate that higher electron temperature can shorten the LH wave propagation on EAST in a multiple-pass regime, thus decreasing the collisional dissipation.

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Realization of thousand-second improved confinement plasma with Super I-mode in Tokamak EAST

Cited by 46 publications

References 70 publications

In situ melting phenomena on W plasma-facing components for lower divertor during long-pulse plasma operations in EAST

In situ melting phenomena on W plasma-facing components for lower divertor during long-pulse plasma operations in EAST

Design and analysis of a PAM launcher at 4.6 GHz for a new LHCD system on EAST

Plasma heating by electron cyclotron wave and the temperature effects on lower hybrid current drive on EAST

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