[en] The EAST tungsten divertor was designed and manufactured in 2012-2014 shut down. First commissioning is during EAST 2014 plasma summer operation due May to July. Some weak points exposed and brought damages on some divertor modules. Reasons were analyzed and optimization was made. Around half year spent for analysis, divertor modules structure optimized manufacturing and reconstruction. The optimized divertor operated during 2015 summer plasma operation and demonstrate optimizations are efficiency. There is no issue for tungsten divertor during operation. EAST plasma heating power increased step by step and will up to 20MW in 2015 winter campaign plasma operation and will validate tungsten divertor heat exhausting capability. (author)

[en] The EAST upper divertor was updated to tungsten divertor in 2014, but the lower divertor was still left carbon divertor. The upper divertor heat load exhausting capability can be up to 10MW/m² , but only 2MW/m² for the lower divertor. To meet the device high performance plasma operation and high plasma heating power. The lower divertor planed to be updated to tungsten divertor. The lower tungsten divertor concept design started from 2016. Considering plasma configurations, neuter particles exhausting, field expansion, cost reduction and so on, geometry of lower divertor was optimized and will be different from upper tungsten divertor geometry.

[en] Full text: Technical R&D is essential for optimized design of the EAST lower tungsten divertor planning to finish assembly in the mid-term of 2019. This poster presents the most urgent technical R&D work that had been recently finished or is expected to be launched in the near-future. In order to improve quality control of contact or welding bond between the armour and the heat-sink of the divertor prior to its installation into the vacuum vessel, a non-destructive examination method by transient infrared thermography is being developed and had been applied to test the lower graphite strike target. To likely use the Mo material in the lower heat flux area, the structure of Mo tile with bolt was tested by electron beam testing facility. The result shows the structure can sustain the heat flux of more than 2.5 MW/m² . Later, a welding structure using resistance welding with solder method is being carried out to raise the capacity of heat flux and increase the interface strength. To eliminate the weld lines between CuCrZr plate and 316L tubes, a new explosive welding method manufacturing the hollow plate of a typical CuCrZr/316L heat-sink plate will replace other welding methods like HIP, laser or electron beam. The explosive welding structure manufactures basically through the process of milling the groove, filling the mould and the explosive welding, and analyzes the interface by mechanical shearing, bending test, bond interface analysis and SEM scanning, and then tests the pressure resistance of flow paths within. To find a more economic or a new method to fabricate the tungsten flat tile or monoblock structure, the explosive welding and direct bonding differ from the HIP method is being studied. The explosive welding of tungsten is an innovation method relies on brittle ductile transition theory of tungsten and suitable constraint of specimen in the explosive process. The direct bonding method without using interlayer metals is used to construct the metallurgical interface directly between Cu and W and make the tensile strength of Cu/W bond close to the Cu.