Evaluation of performance for the EAST upgraded divertor targets during type I ELMy H-mode

Qian, Xinyuan; Peng, Xuebing; Wang, L.; Song, Yuntao; Ye, M.Y.; Zhang, J.W.; Li, Weixing; Zhu, Caoxiang

doi:10.1088/0029-5515/56/2/026010

Cited by 16 publications

(6 citation statements)

References 28 publications

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“…As a result, the peak temperature on the UO W divertor target plate surface saturated at t = 12 s and was maintained stably with T ~ 500 °C during the rest of the discharge. The peak heat flux of steady state is estimated to be about 3.3 MW m −2 using the IR-measured target temperature, augmented by the 3D finite element code ANSYS 7 analysis on the water-cooled W divertor [10], which is about 0.5 MW m −2 less than the peak heat flux for the 60 s H-mode achieved in the EAST 2016 campaign [11].…”

Section: Divertor Strike Point Splitting and Footprint Broadening By ...mentioning

confidence: 86%

Advances in plasma–wall interaction control for H-mode operation over 100 s with ITER-like tungsten divertor on EAST

et al. 2019

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A total power injection up to 0.3 GJ has been achieved in EAST long pulse H-mode operation of 101.2 s with an ITER-like water-cooled tungsten (W) mono-block divertor, which has steady-state power exhaust capability of 10 MWm−2. The peak temperature of W target saturated at 12 s to the value T ~ 500 °C with a heat flux ~3.3 MW m−2 being maintained during the discharge. By tailoring the 3D divertor plasma footprint through edge magnetic topology change, the heat load was broadly dispersed and thus peak heat flux and W sputtering were well controlled. Active feedback control of H-mode detachment with D2 fuelling or divertor impurity seeding has been achieved successfully, with excellent compatibility with the core plasma performance. Active feedback control of radiative power utilizing neon seeding was achieved with f rad = 18%–41% in H-mode operation, exhibiting potential for heat flux reduction with divertor and edge radiation. This has been further demonstrated in DIII-D high β P H-mode scenario within the joint DIII-D/EAST experiment using impurity seeding from the divertor volume. Steady-state particle control and impurity exhaust has been achieved for long pulse H-mode operation over 100 s with the W divertor by leveraging the effect of drifts and optimized divertor configuration, coupled with strong pumping and extensive wall conditioning. Approaches toward the reduction of divertor W sourcing, which is of crucial importance for a metal-wall tokamak, are also explored. These advances provide important experimental information on favourable core-edge integration for high power, long-pulse H-mode operation in EAST, ITER and CFETR.

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Section: Divertor Strike Point Splitting and Footprint Broadening By ...mentioning

confidence: 86%

Advances in plasma–wall interaction control for H-mode operation over 100 s with ITER-like tungsten divertor on EAST

et al. 2019

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“…Since the energy associated with plasma instabilities can be delivered to the material with a time profile that can substantially differ from a rectangular distribution, interest in the constant need to test the response of materials to different thermal load conditions is continuously increasing [33]. For this purpose, we exploit a Nd:YAG laser with a Gaussian time distribution, which can mimic the nonuniform transient thermal load temporal profiles that are found in experimental fusion devices [33][34][35]. Bulk W samples are firstly irradiated under different laser irradiation conditions, i.e.…”

Section: Introductionmentioning

confidence: 99%

Nanosecond laser pulses for mimicking thermal effects on nanostructured tungsten-based materials

et al. 2018

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In this work, we exploit nanosecond laser irradiation as a compact solution for investigating the thermomechanical behavior of tungsten materials under extreme thermal loads at the laboratory scale. Heat flux factor thresholds for various thermal effects, such as melting, cracking and recrystallization, are determined under both single and multishot experiments. The use of nanosecond lasers for mimicking thermal effects induced on W by fusionrelevant thermal loads is thus validated by direct comparison of the thresholds obtained in this work and the ones reported in the literature for electron beams and millisecond laser irradiation. Numerical simulations of temperature and thermal stress performed on a 2D thermomechanical code are used to predict the heat flux factor thresholds of the different thermal effects. We also investigate the thermal effect thresholds of various nanostructured W coatings. These coatings are produced by pulsed laser deposition, mimicking W coatings in tokamaks and W redeposited layers. All the coatings show lower damage thresholds with respect to bulk W. In general, thresholds decrease as the porosity degree of the materials increases. We thus propose a model to predict these thresholds for coatings with various morphologies, simply based on their porosity degree, which can be directly estimated by measuring the variation of the coating mass density with respect to that of the bulk.

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“…Thus, it is impossible to generate a crack by a single thermal shock. However, during the cyclic plasma operations, the cyclic heat loading and cooling might cause fatigue cracks [39].…”

Section: Thermal-mechanical Analysis and Discussionmentioning

confidence: 99%

In situ leading-edge-induced damages of melting and cracking W/Cu monoblocks as divertor target during long-term operations in EAST

Zhu¹,

Li²,

Gao³

et al. 2022

Nucl. Fusion

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Leading-edge-induced thermal loading effect due to assembly tolerance between neighboring castellated plasma facing components is a critical issue in fusion devices. Actively-cooled ITER-like W/Cu monoblocks were successfully installed for upper divertor target in EAST which significantly increases the ability of divertor power exhaust. The misalignment between neighboring monoblocks was formed inevitably during manufacturing and assembly processes, providing a possibility to demonstrate the leading-edge-induced thermal damages. Indeed, the leading-edge-induced melting phenomena of W/Cu monoblocks on upper divertor targets were observed during plasma discharges with a large number of droplets ejected from divertor target using CCD camera, which were also identified at the leading edges of W/Cu monoblocks. Not only that, but also many macro cracks with width of ~70 m and depth of < 5 mm along radial and toroidal directions were also found universally at the leading edges of W/Cu monoblocks by post-mortem inspection after plasma campaigns. Thermal-mechanical analysis by means of the finite element simulation demonstrated that the maximum temperature could reach W melting point under current projected heat load of ~3 MWm-2 on flat top surface with large misalignment up to 3 mm at the leading edges. Meanwhile, the high temperature also induced high thermal stress and strain concentration at the center of leading edges, at which the thermal fatigue cracking could be initially generated. Such kind of cracks at leading edges on W/Cu monoblocks may be unavoidable due to the long-term pulsed fatigue effects. However, the influence of these cracks seems to be acceptable thanks to the limited propagated distance by self-castellation effect, which still need long-term tracking. The in-situ leading-edge-induced damages of melting and cracking on W/Cu monoblocks of EAST upper divertor target provide significant reference to understand the leading-edge-induced thermal effect in ITER and future fusion devices.

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Evaluation of performance for the EAST upgraded divertor targets during type I ELMy H-mode

Cited by 16 publications

References 28 publications

Advances in plasma–wall interaction control for H-mode operation over 100 s with ITER-like tungsten divertor on EAST

Advances in plasma–wall interaction control for H-mode operation over 100 s with ITER-like tungsten divertor on EAST

Nanosecond laser pulses for mimicking thermal effects on nanostructured tungsten-based materials

In situ leading-edge-induced damages of melting and cracking W/Cu monoblocks as divertor target during long-term operations in EAST

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