The Upgrade of EAST Divertor

Zhou, Zibo; Yao, Damao; Cao, Lei

doi:10.1007/s10894-014-9765-7

Cited by 32 publications

(13 citation statements)

References 10 publications

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“…EAST, outfitted with an advanced divertor configuration and heating scheme in support of ITER and future reactors, is equipped with a molybdenum first wall, an ITER-like monoblock tungsten upper divertor and a carbon lower divertor. The dome of the upper divertor is relatively flat, while the dome of the lower divertor with a W-shaped physically separates the inner and outer divertor chambers in order to minimize the leakage of neutrals to the main chamber [28]. The machine is flexibly operated in single null (SN) and double null (DN) divertor configurations using the advanced iso-flux control technique.…”

Section: Methodsmentioning

confidence: 99%

Dependence of upstream SOL density shoulder on divertor neutral pressure observed in L-mode and H-mode plasmas in the EAST superconducting tokamak

Niu

Chen

et al. 2021

Nucl. Fusion

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Upstream density profiles in the scrape-off layer (SOL) have been examined in low-confinement mode (L-mode) and high-confinement mode (H-mode) plasmas in the EAST superconducting tokamak. A weak density shoulder forms in the near SOL region in upper single-null configurations when the neutral pressure measured at the lower divertor exceeds a threshold value of 2 × 10−2 Pa in L-mode plasmas. When the neutral pressure is below this threshold, the weak density shoulder is absent and the sidebands of the lower hybrid waves associated with SOL parametric instabilities are reduced. Active detachment control with neon–deuterium seeding demonstrate that the weak density shoulder can form before the onset of the outer divertor detachment as long as the neutral pressure is above the threshold. Furthermore, no remarkable expansion of a shoulder is observed during divertor detachment, suggesting that divertor detachment is not a necessary condition for the formation or growth of a density shoulder. Through the increase in neutral pressure in the lower divertor by an order of magnitude, the weak shoulder was observed to expand into the far SOL and reach the leading edge of the limiter. The results in L-mode discharges identified the neutral pressure in the lower divertor as a primary factor for the formation of an SOL density shoulder in the upper single-null discharges. For the type-I ELMy H-mode plasmas, a similar density shoulder was detected during the inter-ELM phase when the neutral pressure in the lower divertor exceeded a threshold value of 4 × 10−2 Pa. On the other hand, the shoulder was absent when the divertor neutral pressure went below this threshold even though the plasma discharge was conducted with a higher core line-averaged density and divertor collisionality. This is consistent with the observations in L-mode plasmas. The neutral particle ionization of the working gas is thus believed to play a key role during the formation of the SOL density shoulder in the EAST tokamak.

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Section: Methodsmentioning

confidence: 99%

Dependence of upstream SOL density shoulder on divertor neutral pressure observed in L-mode and H-mode plasmas in the EAST superconducting tokamak

Niu

Chen

et al. 2021

Nucl. Fusion

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“…In 2014, the upper divertor was upgraded to full tungsten, while the lower divertor was conserved to be carbon. [24] Consequently, all high-performance discharges were in the upper single null shape to reduce the carbon impurities entering the main plasma. [25] Thus, operations most frequently have a clockwise toroidal field, such that the ion B × ∇B drift directs away from the active X point, which provides a large amount of discharges for the I-mode investigation.…”

Section: Introductionmentioning

confidence: 99%

I-mode investigation on the Experimental Advanced Superconducting Tokamak

et al. 2019

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By analyzing large quantities of discharges in the unfavorable ion B ×∇B drift direction, the I-mode operation has been confirmed in EAST tokamak. During the L-mode to I-mode transition, the energy confinement has a prominent improvement by the formation of a high-temperature edge pedestal, while the particle confinement remains almost identical to that in the L-mode. Similar with the I-mode observation on other devices, the E r profiles obtained by the eight-channel Doppler backscattering system (DBS8)[1] show a deeper edge E r well in the I-mode than that in the L-mode. And a weak coherent mode (WCM) with the frequency range of 40-150 kHz is observed at the edge plasma with the radial extend of about 2-3 cm. WCM could be observed in both density fluctuation and radial electric field fluctuation, and the bicoherence analyses showed significant couplings between WCM and high frequency turbulence, implying that the E r fluctuation and the caused flow shear from WCM should play an important role during I-mode. In addition, a low-frequency oscillation with a frequency range of 5-10 kHz is always accompanied with WCM, where GAM intensity is decreased or disappeared. Many evidences show that the a low-frequency oscillation may be a arXiv:1902.04750v3 [physics.plasm-ph]

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“…Over the past few years, the EAST has been upgraded with an ITER-like active water-cooling tungsten divertor ( Figure 2 C) and is capable of handling a power load up to 10 MW/m 2 for long-pulse steady-state operation with high power injection. 20 …”

Section: The East Project and Related Activitiesmentioning

confidence: 99%