No abstract

The divertor target components for the Chinese fusion engineering test reactor (CFETR) and the future experimental advanced superconducting tokamak (EAST) need to remove a heat flux of up to ∼20 MW m −2 . In view of such a high heat flux removal requirement, this study proposes a conceptual design for a flat-tile divertor target based on explosive welding and brazing technology. Rectangular water-cooled channels with a special thermal transfer structure (TTS) are designed in the heat sink to improve the flat-tile divertor target's heat transfer performance (HTP). The parametric design and optimization methods are applied to study the influence of the TTS variation parameters, including height (H), width (W * ), thickness (T), and spacing (L), on the HTP. The research results show that the flat-tile divertor target's HTP is sensitive to the TTS parameter changes, and the sensitivity is T>L>W * >H. The HTP first increases and then decreases with the increase of T, L, and W * and gradually increases with the increase of H. The optimal design parameters are as follows: H=5.5 mm, W * =25.8 mm, T=2.2 mm, and L=9.7 mm. The HTP of the optimized flat-tile divertor target at different flow speeds and tungsten tile thicknesses is studied using the numerical simulation method. A flat-tile divertor mock-up is developed according to the optimized parameters. In addition, high heat flux (HHF) tests are performed on an electron beam facility to further investigate the mock-up HTP. The numerical simulation calculation results show that the optimized flat-tile divertor target has great potential for handling the steady-state heat load of 20 MW m −2 under the tungsten tile thickness <5 mm and the flow speed 7 m s −1 . The heat transfer efficiency of the flat-tile divertor target with rectangular cooling channels improves by ∼13% and ∼30% compared to that of the flat-tile divertor target with circular cooling channels and the ITER-like monoblock, respectively. The HHF tests indicate that the flat-tile divertor mock-up can successfully withstand 1000 cycles of 20 MW m −2 of heat load without visible deformation, damage, and HTP degradation. The surface temperature of the flat-tile divertor mock-up at the 1000th cycle is only ∼930 °C. The flat-tile divertor target's HTP is greatly improved by the parametric design and optimization method, and is better than the ITER-like monoblock and the flat-tile mock-up for the WEST divertor. This conceptual design is currently being applied to the engineering design of the CFETR and EAST flat-tile divertors.

No abstract

No abstract

No abstract

No abstract

No abstract

In the EAST experiment, the extent of damages of the divertor is different in toroidal direction. One of the reasons is uneven of heat load of toroidal distribution, which may be caused by geometric errors of the divertor surface. The EAST lower divertor is cooled by 8 toroidal active water-cooling branches, and calorimetric system estimates the heat load and its distribution by measuring the cooling water temperature difference and flow rate. The non-uniformity of the heat load of 8 branches is -3.5% ∼ 4.5%. Besides, using the Leica AT960 / AT401 laser tracker to measure the profile deviation of the upgraded lower divertor, the non-uniformity of the geometric accuracy is -15% ∼ 25%. Besides, it's found that the annular heat load distribution is positively correlated with the comprehensive deviation of the divertor surface. The correlation coefficient is about 15%, and at least seven of the eight divertor regions meet this characteristic.