A versatile integrating sphere based photoacoustic sensor for trace gas monitoring

TL;DR

This paper introduces a compact, versatile photoacoustic sensor using an integrating sphere and organ pipe tube to enhance trace gas detection sensitivity across various wavelengths, suitable for environmental and industrial monitoring.

Contribution

The study demonstrates a novel PA sensor design with an integrating sphere and organ pipe tube, achieving over 1200 times signal enhancement and effective background noise attenuation.

Findings

PA signal enhancement factor exceeds 1200

Effective attenuation of background signals due to material properties

Sensor applicable across ultraviolet to near-infrared wavelengths

Abstract

A compact versatile photoacoustic (PA) sensor for trace gas detection is reported. The sensor is based on an integrating sphere as the PA absorption cell with an organ pipe tube attached to increase the sensitivity of the PA sensor. The versatility and enhancement of the sensitivity of the PA signal is investigated by monitoring specific ro-vibrational lines of CO2 in the 2 mm wavelength region and of NO2 in the 405 nm region. The measured enhancement factor of the PA signal exceeds 1200, which is due to the acoustic resonance of the tube and the absorption enhancement of the integrating sphere relatively to a non-resonant single pass cell. It is observed that the background absorption signals are highly attenuated due to the thermal conduction and diffusion effects in the polytetrafluoroethylene cell walls. This demonstrates that careful choice of cell wall materials can be highly beneficial to the sensitivity of the PA sensor. These properties makes the sensor suitable for various practical sensor applications in the ultraviolet to the near infrared wavelength region, including climate, environmental and industrial monitoring.