Recent Progress on dispersion interferometers for nuclear fusion and low-temperature plasmas

Abstract

A dispersion interferometer (DI) is known to be less sensitive to mechanical vibrations, which is one of the main sources of error for conventional interferometers. A simple optical configuration is also one of the advantages of the DI approach. Since the first application of a homodyne DI on a nuclear fusion plasma device in the 1990s, several interferometer techniques have improved the operation of the DI. Improvements in nonlinear crystals have also improved the performance and availability of the DI. Immunity to neutral gas density changes, which is needed 1Corresponding author.

Progress of CO2 Dispersion Interferometer on EAST

“…There are two modulation methods, as described in [10]; the DI on EAST uses the PEM and lock-in amplifier method. As shown in figure 1(b), the real-time processing system [11] obtains the signs of the fundamental I ω m and second harmonics I 2ωm from the amplifier, and the line density calculation is as follows:…”

Real-time data processing method for CO2 dispersion interferometer on EAST

“…The configuration of the CO 2 -DI is illustrated in figure 1. It mainly consists of a CO 2 laser, two nonlinear crystals, a photoelastic modulator (PEM), an optical filter, an infrared detector, and the real-time data processing system [7,19].…”

First results of CO2 dispersion interferometer on EAST tokamak

“…Additionally, Akiyama et al enhanced the traditional DI on LHD in 2014 by incorporating a photoelastic modulator and extracting the amplitude using a lock-in amplifier [11]. Subsequently, DI systems have been installed on other devices such as DIII-D [12], HL-2A [13], and KSTAR [14], and a DI has been designed as a complementary density diagnostic for ITER [15]. Advances in DIs demonstrate their broad applicability and effectiveness in plasma devices [16].…”