An FFT overlap method for high bandwidth far-infrared laser Interferometer in HL-2A

Abstract

A novel Real-Time High Bandwidth Phasemeter (RHBP) system has been developed for far-infrared laser interferometer in HL-2A tokamak. To meet the requirement of high-precision electron density fluctuation diagnostics, the system is based on the FFT overlap method, which can suppress the measurement error in high-bandwidth mode. The system consists of four Real-time Signal Conditioning (RSC) Modules and four RHBP Modules for high spatial resolution. Benefiting from the field-programmable gate array (FPGA) platform, the proposed method can be implemented with low noise and low cost. Experimental results suggest that the density resolution is 1.79× 1015/m-3 in high-bandwidth mode, which indicates that the proposed RHBP system achieves high performance for high-frequency fluctuation measurement.

Electron density measurement by the three boundary channels of HCOOH laser interferometer on the HL-3 tokamak

“…Firstly, the probing beat signal (P) and reference beat signal (R) output from detectors pass through band-pass filter and then are treated by 16-bit analogto-digital converter (ADC) with sampling frequency of 10 MHz. Here, Field Programmable Gate Array (FPGA) is the key module used to compute the phase difference between P and R, based on the digital phase comparator technique [17][18][19]. The raw beat signals and phase data are temporarily saved in the DDR-III and then uploaded to HL-3 database through fast PXIe bus for offline data analysis.…”

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

“…The flowchart of the data processing system is illustrated in figure 3. The data processing system includes As a reconfigurable device, the FPGA offers rapid prototyping capabilities for constructing digital processing systems [22,23]. It also enables high-speed, real-time, multichannel, parallel processing of the signals outputted by the infrared detectors.…”

Compact phase comparison system for the synthetic HCOOH laser diagnostic system in HL-2A

“…and has achieved remarkable success [16][17][18]. Furthermore, the reverse shear Alfvén eigenmode (RSAE) has been successfully observed in HL-2A using a far-forward collective scattering diagnostic scheme [19].…”