Preliminary R&D on flat-type W/Cu plasma-facing materials and components for Experimental Advanced Superconducting Tokamak

To upgrade the Experimental Advanced Superconducting Tokamak dome and first-wall, flat-type W/Cu plasma-facing components will be installed in the coming years in order to exhaust the increasing heat flux. Mock-ups with an interlayer of oxygen-free Cu (OFC) made by vacuum hot pressing have been developed and the bonding strength was found to be over 100 MPa. The behavior of the mock-ups under steady-state high heat flux loads has been studied. No crack or exfoliation occurred on the W surface and W/OFC/CuCrZr interfaces after screening tests with heat fluxes of 2.24-7.73 MW m(-2). The mock-up survived up to 1000 cycles heat load of 3.24 MW m(-2) with cooling water of 4 m s(-1), 20 degrees C. However, cracks appeared in W around the gaps at about the 300th cycle under a heat load of 5.37 MW m(-2). We have also studied the chemical vapor deposition W coated CuCrZr with an OFC interlayer. It has been found that: (i) the OFC interlayer plays a significant role in achieving coatings without any crack, (ii) the deposition rate was about 0.3-0.5 mm h(-1) at 490-580 degrees C and (iii) a bonding strength of 53.7 MPa was achieved with laser surfi-sculpt.