Humidity enhanced N2O photoacoustic sensor with a 4.53 μm quantum cascade laser and Kalman filter

A high-sensitivity N2O photoacoustic sensor using a 4.53 mu m quantum cascade laser was developed. Sharply enhancement of photoacoustic signal of N2O with the increasing of humidity was investigated experimentally. Finally, 2.3 % water vapor was added to the analyzed sample to improve the vibrational-translational (V-T) relaxation rate of N2O molecule transition, and therefore enhance the N2O photoacoustic signal. High performance with a minimum detection limit of 28 ppbv in 1 s and a measurement precision of 34 ppbv have been achieved, respectively. Kalman adaptive filtering was used to remove the shot-to-shot variability related to the real-time noise in the measurement data and further improve the measurement precision. Without sacrificing the time resolution of the system, the Kalman adaptive filtering improves the measurement precision of the system by 2.3 times. The ability of the N2O photoacoustic sensor was demonstrated by continuous measurement of atmospheric N2O concentration for a period of 7 h.

Automated summary

A high-sensitivity N2O photoacoustic sensor was developed using a 4.53 μm quantum cascade laser, which showed improved signal enhancement with the addition of 2.3% water vapor. The sensor achieved a minimum detection limit of 28 ppbv and a measurement precision of 34 ppbv, and utilized Kalman adaptive filtering to improve measurement precision by 2.3 times without sacrificing time resolution. Continuous measurements over 7 hours demonstrated the sensor's capabilities in monitoring atmospheric N2O concentrations.