基于红外TDLAS技术的高精度CO2同位素检测系统的研制

对天然气分布监测，高精度地检测CO₂同位素是非常重要的。采用可调谐二极管激光吸收光谱(TDLAS)技术，通过13CO₂/12CO₂在4.3 μm处的吸收谱线，实现高精度CO₂同位素检测。该检测系统由工作在连续波模式下的中红外间带级联激光器(ICL)、长光程多通池(MPGC)和中红外碲镉汞(MCT)探测器组成。针对13CO₂和12CO₂两条吸收谱线强度受温度影响的问题，研制了MPGC高精度温度控制系统。实验中，配置5种不同浓度的CO₂气体对检测系统进行标定，响应线性度可达0.999 6。结果表明，当积分时间为92 s时，同位素检测精度低至0.013 9‰，具备实际应用价值。

Development on high precision CO2 isotope measurement system based on infrared TDLAS technology

For natural gas distribution monitoring, it is very important to measure the CO₂ isotope with high precision. In this paper, the tunable diode laser absorption spectrum (TDLAS) technology was adopted to realize the high precision CO₂ isotope measurement through the absorption spectrum line of 13CO₂/12CO₂ at 4.3 μm. The measurement system consisted of a mid-infrared interband cascade laser (ICL) operating in a continuous wave mode, a long-path multipass cell (MPGC) and a mid-infrared mercury cadmium telluride (MCT) detector. Aiming at the problem that the intensity of 13CO₂ and 12CO₂ absorption spectra was affected by the temperature, an MPGC high precision temperature control system was developed. In the experiment, five CO₂ gases of different concentrations were configured to calibrate the measurement system, and the response linearity was up to 0.999 6. The results show that when the integral time is 92 s, the isotope measurement precision is as low as 0.013 9‰, which has practical application value.