Study On Ex-situ Alignment For A Beam Splitting Instrument Used For Single Shot X-ray FEL 3D Imaging

Beam splitting instrument is designed to realize 3D imaging based on Shanghai soft Xray Free Electron Laser(FEL)Facility.FEL has been used for three-dimensional imaging.However,the 3D imaging can only be performed for samples with special symmetry because the flux of the FEL single pulse is very high and sample will be destroyed.In our new designed system a single pulse was split into two bunches,and the two bunches are focused at the same point from two different angles at the same time.To make sure the two bunches will hit the sample at the same time and the same position,off-line alignment is an important step to make sure the final in-situ alignment with FEL beam.The work of this paper is to establish an ex-situ time and space alignment experimental system.The main results of the thesis are shown in the following:1.An ex-situ time and space alignment instrument is designed based on white visible light interference principle.Theoretical simulation is performed on the alignment based on wave optics.Linear relation between displacement of the aplanatic point and variation of optical path difference is acquired.The feasibility of time and space alignment based on white visible light interference is verified.2.The experimental system is established according to the design,and the time and space alignment is realized.The experimental results are in good agreement with the theoretical simulations.The resolution of time alignment is 48.1fs.By changing the focusing lens the instrument can be directly used for the in-situ FEL alignment.