Recently, a synthetic formic-acid laser diagnostic system has been deployed in HL-2A tokamak. However, the main electronics of the subsystems were discrete devices, and multimodal data analysis remained out of reach. In this work, we developed a novel compact high sensitivity Phasemeter (CHSP) system to integrate interferometer, far-forward collective scattering diagnostic (FCS), and Faraday effect polarimeter. It provides a framework for real-time intelligent diagnosis such as plasma disruptions prediction. We also propose a Synchronous Fast Fourier Transform (SFFT) method for suppression of spectral leakage and noise reduction. Experimental results indicate that the electronics system accuracy is about 1.0× 1015/m-3, which fully meets the requirements of HL-2A. This work represents a crucial step toward a high-performance intelligent diagnosis in HL-2A.

A novel two-laser Polarimeter-Interferometer (PIer) diagnostic scheme, in which Faraday rotation angle (αF) and electron density (ne) can be simultaneously measured by taking advantage of two lasers and two detectors for each channel, has been successfully demonstrated on HL-2A tokamak through upgrading one channel of existing monofunctional Faraday-effect polarimeter. In comparison with the conventional three-laser PIer diagnostic, two-laser PIer generates only one intermediate frequency (IF), avoiding the overlap of IF frequency bands, so as to increase the time resolution and decrease the phase noise of system. The single channel two-laser PIer was firstly put into operation in 2016 HL-2A experimental campaign, and both Faraday rotation angle and electron density phase have been measured with a fast time resolution of 1.0 μs and a phase resolution of 0.1̂ and 1.0̂, respectively. This work is valuable for next step far-infrared (FIR) laser PIer construction on HL-2M tokamak, as well as the future International Thermonuclear Experimental Reactor (ITER).