Abstract: The expression for reflectivity of a whispering gallery mirror (WGM) for a nontangential beam is obtained. It is shown that the effective critical angle for this mirror is $theta$-w$/ $APEQ $theta$+3/2$/$-c$//$psi$+1/2$/, where $theta$-c$/ is the critical angle for coating material, and $psi is the angle at which the beam is turned. The overview of WGM reflectivity is given for various materials in a wide spectral range. The coatings utilizing light elements enable one to provide good reflectivity at shortwavelength and longwavelength sides of XUV range. Intermediate spectral interval $lambda $APEQ 50 $DIV 300 angstroms may be covered by heavier elements due to the presence of minima and dips in their photoabsorption cross section.!16
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