中红外驻波V型腔衰荡14co2光谱检测

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Abstract： To address the pressing need for highly sensitive detection of gaseous pollutants in nuclear facili ties，a detection technique employing cavity-enhanced absorption spectroscopy of 14CO2 was developed. This method incorporates a standing wave V-shaped cavity alongside a quantum cascade laser. A mid-infrared absorption spectroscopy detection system was constructed， successfully achieving highly sensitive detection of 14CO2 gas. The system utilizes a standing wave V-shaped cavity comprising three high-reflectance mirrors，which effectively doubles the spectral resolution without necessitating an increase in the physical length of the optical cavity. By incrementally scanning the laser wavelength to sequentially provoke the absorption events of adjacent cavity modes，comprehensive molecular spectral measurements are obtained while maintaining a high signal-to-noise ratio of cavity absorption spectroscopy signals. Furthermore，to mitigate variations in trigger positions caused by fluctuations in cavity length and laser frequency drift，dynamic correction of the step voltage values was implemented during the experiment，resulting in long-term stability of 14CO2 spectral measurements. Allan variance analysis revealed that the detection limit of this system is 2.5×10-10cm-1 ，corresponding to a minimum detectable concentration of 1.2×10-12 for 14CO2 . This technology holds significant promise for monitoring the emission of radioactive carbon dioxide in the exhaust gases from nuclear power plants.

Key words： spectral detection; laser absorption spectrum；cavity ring-down spectrum； radiocarbon

1引言

碳 14（14C） 是碳的一种放射性同位素，半衰期为5730年，它的自然来源是基于宇宙射线与地球大气层中氮原子的核反应[1]。（剩余11350字）