Improvement of transmittance using groove structured surface for microwave imaging diagnostics in tokamak plasmas

Groove plate with triangle structure has been designed and fabricated to improve the microwave transmittance in W band. The parameters of the triangle structure has been optimized via the Effective Medium Theory (EMT) and FDTD program. The antireflection surface in W band has been verified in lab, the experimental results are qualitatively consistent with the theoretical results.