Research And Key Techniques On The Polarized Scattering Characterisitcs Of Atmoshperical Particles

Optical detection method has advantages of non-destructive,fast detection and real-time online.With the development of laser light source and detector technology,optical detection methods have become more and more widely used in the filed of atmosphere.Polarization scattering detection develops form non-polarization methods,and polarized method has the characteristics of large particle information acquisition,high compati-bility with existing non-polarization devices,and sensitivity to small diameter particles.Polarization methods are increasingly used in atmospheric detection,such as satellite polarization ground mapping,aerosol optical property detection,and lidar measurement of aerosol overall optical thickness and optical thickness and so on.The existing optical scattering methods for measuring atmospheric particles mainly include lidar based on the optical properties of aggregate particles and online measurement instruments based on single particle scattering.In this paper,the optical properties of atmospheric particles were characterized by polarization scattering method.The Monte Carlo simulation for the aggregate particles and the particle size distribution scattering program for single particles were established,then an integral polarization scattering simulation system was established.At the same time a verification experiment setup was built and completed the feasibility demonstration.Specifically,the main research of this paper includes the following three parts:In this thesis,the Monte Carlo simulation program for atmospheric particles was developed based on the back-scattering measurement of particle clusters by the polarized lidar,and the concentration changes,composition changes,and refractive index changes were simulated.Two-component and multi-angle scattering,in the presence of some changes in concentration and composition,provided preliminary insights into the polar-ization characterization of the optical behavior of the aggregation of particulate matters,and initially captured the influence of atmospheric particles on the polarization parameters.Subsequently,the paper focused on single particle scattering method to develop a simulation program for the polarization scattering behavior of single particle.The selection and characterization of polarization parameters for different particle sizes and refractive indices of different components were discussed,and the specific characterization parameters for the strong absorption properties of carbon black,such as wavelength,detection solid angle,and particle size distribution,were further analysed.The discussion of the parameters to obtain the conclusion that this parameter has stability and reliability is a special supplement of soot to distinguish the different components of particulate matter.Finally,in order to be able to verify the parameters of the above single particle polarization characterization,a single particle polarization scattering measurement setup was built.By overcoming the key technical challenges such as particulate air injection,receiving channel simultaneity to acquire polarization components,and setting inspection windows to filter invalid signals,we compared the processed data with the previous simulation data and passed the existing accepted online measurement charcoal.On the one hand,the comparison of the results with the OC/EC instrument proved the correctness of the previous simulation results and provided a theoretical basis for the subsequent exploration of more parameters.On the other hand,it verified the reliability of the experimental device built,and further integrated more.The function laved a good foundation.