一种具有高稳定性和高敏感度的紧凑型仪器, 能精确、 实时、 实地连续测量和显示环境空气中的痕量甲烷(CH4)浓度。 仪器采用了已集成热电制冷器激射波长为7.5μm的法布里-珀罗量子级联激光器(QCL)在室温脉冲工作模式下的最新技术, 以覆盖CH4位于ν4附近基频特征吸收谱带。 同时, 采用高品质液氮制冷碲镉汞中红外探测器, 配合全反射镀金椭球反射镜一同使用, 在20 cm单路径开放式光路吸收气室环境下, 确保被测甲烷气体浓度为200 μmol·mol-1的实验条件下保持稳定度高达5.2×10-3。 此仪器所集成的软件算法通过时间鉴别电子技术实现对QCL控制, 能够在无需校准的情况下, 提供连续痕量甲烷气体检测。 实验表明, 仪器可以用于环境监测中的实地痕量气体测量, 并且操作人员可以通过替换在不同波长下运行的QCL来测量其他气体。

Presented is a compact instrument developed for in situ high-stable and sensitive continuous measurement of trace gases in air, with results shown for ambient methane (CH4) concentration accurate, real-time and in-situ. This instrument takes advantage of recent technology in thermoelectrically cooling(TEC) pulsed Fabry-Perot (FP) quantum cascaded laser (QCL) driving in a pulse mode operating at 7.5 μm ambient temperature to cover a fundamental spectral absorption band near ν4 of CH4. A high quality Liquid Nitrogen (LN) cooled Mercury Cadmium Telluride (HgCdTe) mid-infrared (MIR) detector is used along with a total reflection coated gold ellipsoid mirror offering 20 cm single pass optical absorption in an open-path cell to achieve stability of 5.2×10-3 under experimental condition of 200 μmol·mol-1 measured ambient CH4. The instrument integrated software via time discriminating electronics technology to control QCL provides continuous quantitative trace gas measurements without calibration. The results show that the instrument can be applied to field measurements of gases of environmental concern. Additional, operator could substitute a QCL operating at a different wavelength to measure other gases.