Optimization and complete characterization of a photoacoustic gas detector

We report the complete designing process and realization of a photoacoustic spectrometer. In a first step, the cell design is optimized in order to achieve maximum cell constant and working frequency using a finite element method. Technological and integration constraints are used to define dimensional constraints on the cell. In a second step, a dedicated optical bench is presented along with the photoacoustic cell. The resonator response is then measured using a quantum cascade laser for methane detection and condenser microphones as detectors. The system detection limit is also discussed as it depends not only on the cell response but is also a combination of parameters linked together: environmental noise, microphones characteristics and cell conception. The gas flow required in a dynamic operation of the sensor degrades the detection limit regardless of the microphones quality. Choices on cell conception to minimize gas flow noise are discussed.