{b_{\cup_{{_{{D}}}}}}^2
l_{{_{2}}}$, we estimate from Eq.  for the required cumulative dispersing rate ${|{{{\mathcal D}}_{\cup_{{_{{R}}}}}}|} \simeq
25~\mu$rad/meV in the defocusing dispersive element. These are relatively large values. Typically, in a single Bragg reflection, a maximum dispersion rate is ${{\mathcal D}}\simeq 6-8~\mu$rad/meV for photons with energy $E\simeq 10$ keV [@SLK06; @ShSS11]. As mentioned before, multi-crystal arrangements can be used to enhance the dispersion rate [@SSM13].

Such large dispersion rates ${{{\mathcal D}}_{\cup_{{_{}}}}}$, unfortunately, tend to decrease the transmission bandwidths $\Delta E_{{_{\cup}}}$ of the dispersing elements [@SSM13; @Shvydko15]. Achieving strong signals in IXS experiments, however, requires $\Delta E_{{_{\cup}}} \gg
\Delta {\varepsilon}$. Therefore, optical designs of the dispersing elements have to be found featuring both large ${{{\mathcal D}}_{\cup_{{_{}}}}}$ and $\Delta
E_{{_{\cup}}}$. Figures \[fig003\] and \[fig004\] show representative examples of multi-crystal CDDW-type inline dispersing elements [@ShSS11; @SSS13; @SSS14] of the defocusing and refocusing systems, respectively, with the required cumulative dispersion rates, asymmetry factors, and with bandwidths $\Delta E_{{_{\cup}}}\simeq
5.5-9$ meV, i.e., $\Delta E_{{_{\cup}}}/\Delta {\varepsilon}\simeq
55-90$, designed for use with 9.1-keV photons. These examples are modifications of the dispersing elements designs presented in [@Shvydko15]. The CDDW optic in the ($\pi+$,$0-$,$0+$,$0-$) scattering configuration is preferred for the defocusing dispersing element D$_{{_{\mathrm {{D}}}}}$ (Fig. \[fig003\]) as it provides the 