Multi-Channel FIR HCN Laser Interferometer on HT-7 Tokamak

A Five-channel far-infrared (FIR) hydrogen cyanide (HCN) laser interferometer was developed to measure plasma electron density profile on the HT-7 superconducting tokamak. The structure of the five-channel FIR laser interferometer is described. The laser source used in the interferometer was a continuous wave glow discharge HCN laser with 3.4 m cavity length and 100 mW power output at 337 μm wavelength. The temporal resolution was 0.1 ms and the detection sensitivity was 1/12 fringe. Preliminary experimental results measured by the interferometer on HT-7 tokamak are reported.