Basic Research On Plasma Imaging System For Holographic Parameter Diadnostics

Due to certain technical limitations,the traditional microwave diagnostic method can only diagnose the local plasma distribution.In order to obtain a more comprehensive plasma distribution,this thesis proposes a plasma imaging technology for holographic parameter diagnostics by combining microwave holographic imaging technology and microwave diagnostic technology.Based on the basic principle of microwave holographic imaging technology,this thesis designs and builds an imaging system with a scanning frequency range of 8.5-12.5 GHz.In order to verify the feasibility of this system,the simple structural objectives are used to carry experiment in this thesis and the image reconstruction is achieved successfully.At the meantime,based on the basic electromagnetic properties of plasma,the transmission and reflection models of electromagnetic waves in plasma in free space are constructed and the relationship between characteristics of plasma,such as electron density and collision frequency,and parameters,including S11 and S21,is derived.A new method for plasma wide-band microwave diagnostics is proposed.The method mentioned is proved to increase confidence level by diagnosing the plasma in the low-voltage vacuum discharge tube.Based on the research of these two technologies,this thesis proposes a plasma diagnostic technology for holographic imaging system by combining microwave holographic imaging technology and microwave diagnostic technology and establishes a corresponding algorithm model.The image reconstruction of both collision frequency and electron density distribution of the target plasma is performed by using the vacuum discharge No.? as a diagnostic object.In addition,for the problem that the resolution of the imaging space is not very good as the result of comparatively small amount of information in the effective scanning aperture by using the mentioned plane scanning method,in order to enlarge the scanning aperture and improve the imaging precision,a spherical scanner is proposed in this thesis.In summary,the plasma imaging technology for holographic parameter diagnostics proposed in this thesis not only broadens the application field of microwave holographic imaging,but also promotes the development of plasma diagnostic technology.