Technique for diagnosing x-ray laser beam quality by use of the moire signal

摘要

We present what we believe is a novel technique based on the moire effect for fully diagnosing the beam quality of an x-ray laser. Using Fresnel diffraction theory, we investigated the intensity profile of the moire pattern when a general paraxial beam illuminates a pair of Ronchi gratings in the quasi-far field. Two formulas were derived to determine the beam quality factor M~(2) and the effective radius of curvature R_(e) from the moire patultern. On the basis of the results, the far-field divergence, the waist location, and the radius can be calculated further, Finally, we verified the approach by use of numerical simulation.