Characterization Of Field Polarization And Spatial Coherence In A Diffraction Limited Visible Synchrotron Radiation Beam

The motivation of this thesis is to characterize the polarization state and spatial coherence of the diffraction-limited visible synchrotron radiation(SR)beam,and a two slits interferometer was developed to measure the electron beam size based on the beam polarization and spatial coherence properties.The diffraction-limited visible SR was produced from Stanfod Synchrotron Radiation Light Source(SSRL).The research work on beam polarization can provide valuable information for the design of diagnostic beamline,moreover,it's the requirement for research work on beam spatial coherence.Based on the beam polarization and spatial coherence properties,a two slits interferometer was designed for measuring the transverse electron beam size and rotation angle.The innovation of the thesis lies in these parts.(1)A continuous scan system was developed to accurately and efficiently characterize the SR polarization as a function of vertical observation angle relative to the accelerator mid-plane.(2)Determine the influence of Rh and Al reflective mirror to the visible beam polarization,and build the mathematic polarization model for the beam at the experiment hatch.(3)Compare and analysis the beam polarization model with the measured result on the Poincare sphere.(4)Develop an interferometer with two rotated slits,which can be used for measuring the electron beam size and roated angle.In order to characterize the visible beam polarization,a continuous scan was developed to measure the beam intensity accurately and efficiently.The Stokes parameters can be calculated from the measured beam intensity.Moreover,the theoretic beam polarizat:ion models at the source point and end station were built and compared with the measured results on poincare sphere.The results indicate that thin film Rh mirror has a significant influence on ? and ? beam amplitude and their phase difference.The measured beam polarization state agrees well with the polarization model which was built based on the theoretic ? and ? beam amplitude and the actual phase variation.In order to characterize the spatial coherence of visible SR beam,and measure the electron beam size based on its spatial coherence property,a detailed derivation of the Van-Cittert Zernike theorem is provided.The theorem demonstrates the origin of the Fourier transform relation between incoherent source intensity distribution and fringe contrast evaluated as a function of spatial frequency.The horizontal and vertical two slits interferometer were developed to measure the variation of spatial coherence as a function of spatial frequency.Moreover,a rotated two slits interferomter was developed for the first time,and it was used for measuring the degree of spatial coherence as a function of spatial frequency.The whole electron beam transverse size and rotated angle can be calculated from the rotated two slits measurement results.This was the first time that the interferometer slits had been rotated to map the transverse particle beam profile.The new rotation technique also provides the tilt angle of the electron beam,and it is an important diagnostic method for accelerator research.