Data recording system of a dispersion interferometer based on a CO2 laser

The data recording system of a multichannel double-pass dispersion interferometer based on a CO2 laser is described. This system has been designed to record the linear density of plasmas in a real-time mode with a time discreteness of 4 μs and resolution 〈N e L〉 ∼ 0.34 × 1013 cm−2 (N e is the electron component of the plasma density, and L is the plasma size in the wave propagation direction) in the range of linear density variations of up to 1017 cm−2. The system is built from unified recording modules that use fast ADCs to record the shape of photodetector and modulator signals and FPGA-based digital units of dataflow processing to form results of measurements. The single-channel recording module of the dispersion interferometer has been tested under actual experimental conditions of the GDL gas-dynamic trap and the TEXTOR tokamak (Julich, Germany).