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A homodyne Mach–Zehnder (M-Z) optical fiber interferometer (OFI) based on the optical coupler demodulation with 1.55 μm wavelength is firstly developed for high plasma density measurement on the theta pinch (IMP-θ) plasmas in the Institute of Modern Physics for the research on magnetic-inertial fusion. The evolutions of center line-averaged electron density in the theta pinch discharges are measured by the interferometer. The OFI is full-fiber structure and the line-average electron number density resolution is 10 18 m -2 . The minimum time resolution of OFI is 1ns, depended on the bandwidth of terminal InGaAs detectors. Finally, the dynamics of theta pinch plasmas are reported, which are analyzed from the density waveforms under different gas pressures and charging voltages of capacitor banks. It shows the OFI is a highly reliable and flexible routine high plasma density diagnostic tool for theta pinch 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.

KTX (Keda Torus eXperoment) is a new reversed field pinch magnetic confinement device which is designed in University of Science and Technology of China. Its main parameter is between RFX and MST. The vacuum vessel system of KTX is designed to keep plasma in a high vacuum and guarantee the enough mechanical strength to resist stress loads in different working conditions. The main design work has been already completed while the R&D work and preparation for manufacturing and assembling is going on. With the purpose of getting a prediction of the mechanical behavior of KTX vacuum vessel and its supports, electromagnetic and structural finite element models from three different considerations are built. This article presents the calculation methods of mechanical behavior respectively due to the electromagnetic force during plasma disruption, the buckling of elongated support legs and vacuum vessel separating. Furthermore, in accordance with the results, a comprehensive cognition to the relationship between mechanical structure and strength is indicated, so as to complete the detailed and optimization design.