Abstract
This study presents an acoustics-based method for helium leakage detection and validates the method by measuring the acoustic wave transmission time in a mixture of helium and air. As acoustic waves have different speeds in helium and air, the helium/air ratio in a mixture should affect the traveling time of waves transmitting through the mixture. To understand the sensing mechanism, we theoretically investigated the relation between the acoustic wave traveling time and the helium/air ratio using two different models, where helium and air are assumed to be unmixed and well-mixed, respectively. Moreover, experiments are performed to validate the theoretical prediction for the model of the unmixed case. The experimental setup consists of a U-shaped waveguide, an acoustic transmitter with 20 kHz resonant frequency, and an acoustic receiver. The acoustic waveguide was filled with a mixture of helium and air as the carrier medium for acoustic wave propagation. The experimental result reveals a monotonic trend between the wave traveling time and the helium/air ratio. Furthermore, the trend observed from the experimental result is consistent with the theoretical prediction. We expect that this study can inspire future research for developing acoustics-based helium leakage detection methods.
