Dispersion interferometer based on a CO2 laser for TEXTOR and burning plasma experiments

A dispersion interferometer based on a continuous-wave CO2 laser source (λ=9.57 μm) with double plasma passage for measurements of the line-integrated electron density in the TEXTOR tokamak and the GDT linear system has been developed and tested in experiments. A sensitivity of 〈nel〉min=2×1017 m−2 and a temporal resolution of 1 ms have been achieved. The interferometer does not need any rigid frame for vibration insulation. Its basic components are installed compactly on an optical bench placed on a stable support outside of the torus. The possibility for the development of a multichannel dispersion interferometer for the next generation of fusion devices (e.g., W7-X, ITER) is discussed.