Simple, high-resolution method for measurement of the natural relative energy bandwidth of Si(111) double crystal monochromators

Abstract

Measurement of photon energy resolution, an important operational parameter of X-ray double-crystal monochromators (DCMs), is complicated by the coupled relationship between energy bandwidth and diffraction angle. This paper reports two methods of analyzing the natural relative energy bandwidth of DCMs at fixed photon energy. The first is based on measurement of the post-DCM beam using a monolithic double channel-cut monochromator (MDCM), while the second uses measurements of the K absorption edge of copper (Cu) in the post-DCM beam as a small vertical angular slice of the source is scanned. Both analysis methods eliminate the effects of synchrotron radiation (SR) vertical angular divergence. The natural relative energy bandwidth values for the Si(111) DCM measured by the MDCM and Cu K-edge absorption methods are 1.59×10−4 at 12.763 keV and 1.61×10−4 at 8.979 keV, respectively. This result demonstrates that the two methods offer nearly the same level of precision for determining the natural relative energy bandwidth of Si(111) DCMs. However, the Cu K-edge absorption method has the advantages of requiring simpler experimental equipment and significantly shorter data acquisition time.