Is Multistep Necessary?

Kallman, J S

Lawrence Livermore National Laboratory

关键词: Diffraction;    99 General And Miscellaneous//Mathematics, Computing, And Information Science;    Wavelengths;    Refractive Index;    36 Materials Science;   

DOI  :  10.2172/15016783
RP-ID  :  UCRL-TR-207667
RP-ID  :  W-7405-ENG-48
RP-ID  :  15016783

美国|英语

来源: UNT Digital Library

【 摘 要 】

In looking at simulations for the x-ray microscope the question ''Is it necessary to use the multislice method to adequately model the transmission of x-rays through the target?'' has been raised. Another question that has been raised is ''Is it necessary to include diffraction effects in our simulations?'' The purpose of this report is to lay these questions to rest. The short answer to both of these questions is ''No''. The multislice method (also known as the beam propagation method (BPM)) is used to solve the paraxial wave equation. The paraxial wave equation is what the Helmholtz equation reduces to in the limit of small index of refraction deviations and small angular deviations. It lies in the middle ground between full wave simulation and ray tracing (a short wavelength limit). The BPM takes a region and cuts it into strips. The method then propagates a wavefront through the region one strip at a time. For each strip, the method first propagates the wavefront the width of the strip as if through free space (diffraction step), then the method applies a phase correction based on the index of refraction distribution in the strip (refraction step). In this way the method marches the wavefront through the region of interest.