Raman Spectroscopy Detection Of SF₆ Decomposition Gas Based On All Phase Tunable Optical Feedback Frequency Locked Cavity Enhancement Technology

The accurate detection of SF₆ decomposition characteristic gases（SO₂,CF₄,SO₂F₂,COS,CO,CO₂）is the key to realize the operation state assessment of gas insulated equipment,and is an important technical support to ensure its safe and reliable operation.It is difficult to realize simultaneous detection and analysis of decomposed gas under the background of high concentration of SF₆ by conventional methods such as gas chromatography.In this paper,combined with the National Natural Science Foundation Project"micro gas optical feedback frequency locked V-shaped cavity enhanced Raman spectroscopy detection technology research",we carried out the research on SF₆ decomposition gas Raman spectroscopy detection based on all phase tunable optical feedback frequency locked cavity enhancement.The method of all phase tunable V-shaped cavity enhanced Raman spectrum frequency locking was studied.The gas detection platform of all phase tunable V-shaped cavity enhanced Raman spectrum was built.The Raman spectrum of SF₆ decomposed gas was detected and analyzed at the same time,and the detection characteristics of SF₆ decomposed gas by optical feedback frequency locking V-shaped cavity enhanced Raman spectrum were obtained.The main work is as follows:（1）The relationship between the free operating frequency and the coupling frequency of the laser is studied.The influence of the feedback efficiency and the feedback phase on the optical feedback frequency of the Raman V-shaped cavity is obtained,and the mode matching method is determined;An optical feedback frequency locking phase adjustment method based on cavity film symmetry and cavity mode intensity is proposed,which realizes all phase adjustment of optical feedback frequency locking and avoids the adjustment trap area.（2）The influence of scanning range,feedback efficiency,feedback phase and high-order transverse mode on optical feedback frequency locking is studied,and the appropriate scanning range and feedback frequency are determined.The experimental results show that the proposed algorithm is effective,and the all phase adjustable optical feedback frequency locking method is realized,which improves the stability of optical feedback frequency locking.（3）The signal-to-noise ratio（SNR）of the cavity is about 2300 times.The Raman spectra of nitrogen,oxygen,SF₆ and their decomposed gases in ambient air are detected and analyzed.The characteristic shifts and detection limits of Raman spectra of various gases are determined.The effects of gas partial pressure,laser power,temperature and other factors on the spectral characteristics（peak height,Raman frequency shift）of the characteristic Raman peaks were studied.This paper lays a foundation for on-line monitoring of SF₆ decomposition gas in gas insulated equipment.At the same time,the proposed optical feedback frequency locked V-shaped cavity enhanced Raman spectroscopy gas detection method is also suitable for other areas of gas detection.