Surface Microhole Modified Fiber-enhanced Raman Spectroscopy And Sulfur Hexafluoride Decomposition Gases Detection

The concentration of SF₆ decomposition gas（SO₂F₂,SO₂,CF₄,COS,CO₂,CO）is an important characteristic that reflects the failure and aging state of Gas Insulated Equipment.Research on high-sensitivity and high-accuracy detection methods for multi-component characteristic gases is of great significance for Gas Insulated Equipment safe and reliable operation.Raman spectroscopy can simultaneously detect multi-component gases at a single wavelength,and has the advantages of strong anti-interference ability,resistance to aging.However,the weak Raman scattering effect of gas limits the application of Raman spectroscopy in trace gas detection.In this thesis,Fiber-enhanced Raman spectroscopy for SF₆ decomposed gas detection is carried out,the influence of side micro-hole modification parameters on gas equilibrium time is studied,and the optimal micropore parameters is determined;The Fiber-enhanced Raman spectroscopy gas detection platform modified with side microholes is designed and built,achieving simultaneous detection of SF₆;The Raman spectrum peak characteristics of the SF₆decomposition gas are obtained;the Raman spectrum gas quantitative analysis method based on the multi-factor correction with the internal standard gas is established.The specific research results in this paper are as follows:The effect of surface microhole parameters on the gas equilibrium time is studied.A simulation model of a hollow-core fiber with surface micropores was established,and the influence of micropore layout,micropore diameter,and number of micropores on the gas equilibrium time is studied,and the optimal micropore parameters were determined.Comparing the effects of focused ion beam exposure and femtosecond laser processing technology on the surface micro-hole modification of the hollow core anti-resonance fiber,the surface micro-hole modification of the hollow core fiber is finally realized.The Fiber-enhanced Raman spectroscopy SF₆ decomposition gas detection platform modified with side microholes is designed and built.Coupling lens,and spatial filter are optimized,combined with method of adding a mirror to fiber end to increase the gas Raman signal intensity and signal-to-noise ratio by more than 40 times;The influence of fiber length on gas Raman signal strength and signal-to-noise ratio is studied.The equilirum time of each gas is determined by the free diffusion experiments The limits of detection of SO₂F₂,SO₂,CF₄,COS,CO₂,CO are 48.4、12.3、41.9、25.3、18.9、57.1μL/L respectively with 0.1 MPa total pressure,0.3 m hollow-core fiber and 60 s of integration time.The gas partial pressure characteristics,laser power characteristics and temperature characteristics of the Raman peaks of SO₂F₂,SO₂,CF₄,CO₂,CO and internal standard gas（SF₆）are studied.The peak height and peak area of characteristic Raman spectrum increase linearly with the partial pressure of the gas and the laser power,and decrease approximately linearly with the increase of temperature.A multi-factor correction method based on the internal standard gas（SF₆）is eatablished for the quantitative analysis of gas Raman spectroscopy;The gas detection characteristics of Fiber-enhanced Raman spectroscopy,such as accuracy,repeatability,are studied,and the high-accuracy detection of SF₆ decomposition gas is realized with the detection accuracy higher than 95%for each gas and repeatability deviation is less than 5%.The research of the thesis lays the foundation for the on-line monitoring of SF₆decomposition gas Raman spectroscopy,and promotes the application of fiber-enhanced Raman spectroscopy in the field of trace gas detection.