An Investigation into the Effects of Pressure on Gas Detection Using an Integrating Sphere as Multipass Gas Absorption Cell: Analysis and Discussion

Abstract

The approach adopted in the present work was to increase the pressure within an integrating sphere system to increase the number density of molecules in the gas cell and hence to obtain a significant absorption in order to improve the sensitivity of the measurement system. This feasibility study has allowed an assessment of the net absorption gain with the rise of pressure and highlights the validity domain of the linear operating regime relative to Beer's law. Experiments were conducted on the oxygen A-band. The absorption peaks of oxygen at 760 nm typically were measured with a 50 mm diameter integrating sphere system under various pressures. Tests were performed up to 200 bar, the pressure for which the linear regime was operative, and analysed from a theoretical and experimental point of view. An experimental net absorption gain of 160 was achieved in this pressure range with the possibility of up to 650 bar while remaining in the linear regime. Finally, the experimental data obtained, in particular the absorption evolution due to the contribution of oxygen gas, seem consistent with the simulated results and are discussed in this paper.

Investigating the Relation between Absorption and Gas Concentration in Gas Detection Using a Diffuse Integrating Cavity

“…To improve the detection sensitivity, a long optical path length is necessary for trace gas measurement because the signal to noise ratio (SNR) improves with increasing optical path length in absorber [1]. Many methods have been developed to extend the optical path length, such as multi-pass cells [2,3], cavity ring-down spectroscopy (CRDS) [4], gas in media absorption spectroscopy (GASMAS) and applications of diffuse integrating cavities [5][6][7]. Among these methods, integrating cavities have proven advantageous in good stability, effortless laser beam alignment, few interference fringes, and low cost [8,9].…”