A non-contact method for vacuum degree detection in simulant vacuum interrupters using coaxial optical path laser-induced plasma

This paper proposes a non-contact vacuum degree detection method for vacuum interrupters based on coaxial optical path laser-induced plasma (LIP), aiming to overcome the limitations of conventional techniques in accuracy and on-line applicability. A coaxial optical configuration was employed, in which the excitation laser and plasma emission collection shared the same optical axis, thereby improving signal acquisition efficiency and imaging consistency. An oxygen-free copper target was irradiated by pulsed laser under different pressures, and the plasma images were recorded for quantitative analysis of integrated radiation intensity. The results demonstrate that, in the low-vacuum range below 10 Pa, the integrated radiation intensity increases as pressure decreases, exhibiting strong correlation with vacuum degree. Although higher laser energy enhances plasma intensity, it does not alter the fundamental dependence on pressure; moreover, increasing the laser energy appropriately improves image stability and reduces measurement uncertainty. In summary, the proposed approach achieves non-contact, quantitative, and image-based detection of vacuum degree in operating vacuum interrupters. The coaxial optical path design significantly enhances the stability and reliability of signal acquisition, providing a promising new pathway for on-line monitoring of vacuum switchgear. A new non-contact method detects vacuum quality in interrupters using laser light and images. The coaxial optical setup improves signal stability and reduces alignment errors. Results show a clear link between light intensity and vacuum level, enabling online monitoring.