Measurement Module of Dispersion Interferometer Based on the CO2 Laser for Plasma Density Control

This article discusses a measurement module of a dispersion interferometer based on a CO2 laser for integral plasma density measurements with a resolution of 4 x 10(11) cm(-2) with a time discreteness of 4 mu s. Such characteristics of the device make it possible to use the results of its measurements in feedback loops for plasma density control. The main elements of the measurement module are crystals of analog-to-digital converters (ADCs) and a digital streaming data processing node based on a field-programmable gate array (FPGA). The algorithm for calculating the plasma density implemented in the digital node is based on the harmonic analysis of interferometer signals and is resistant to noise and changes in the modulation depth. The measurement module under consideration is a prototype of the system of monitoring and automatic control of plasma density at the Globus-M2 facility (St. Petersburg, Russia).