considered in this paper the dispersion rate of the D-crystals ($n=2,3$) is much larger than those of the C- and W-crystals ($n=1,4$), see Tables \[tab1\] and \[tab14\]. In this case, the cumulative dispersion rate can be approximated by ${{{\mathcal D}}_{\cup_{{_{4}}}}}
\simeq
b_{{_{4}}}b_{{_{3}}}{s}_{{_{2}}}{{\mathcal D}}_{{_{2}}}+b_{{_{4}}}{s}_{{_{3}}}{{\mathcal D}}_{{_{3}}}=b_{{_{4}}}(b_{{_{3}}}{s}_{{_{2}}}{{\mathcal D}}_{{_{2}}}+{s}_{{_{3}}}{{\mathcal D}}_{{_{3}}})$. The largest dispersion rates can be achieved in systems, in which the product is ${s}_{{_{2}}}{s}_{{_{3}}}{{\mathcal D}}_{{_{2}}}{{\mathcal D}}_{{_{3}}}<0$.

There are four high-dispersion-rate CDDW configurations featuring ${{\mathcal D}}_{{_{2}}}{{\mathcal D}}_{{_{3}}}>0$ and ${s}_{{_{2}}}{s}_{{_{3}}}<0$: $(\pi+,\pi-,\pi+,0+)$; $(\pi+,\pi+,\pi-,0-)$; $(\pi+,0-,0+,0-)$; and $(\pi+,0+,0-,0-)$. These configurations are especially interesting because of the incident and transmitted x-rays being parallel (in-line scheme).

There are four other high-dispersion-rate CDDW configurations featuring ${{\mathcal D}}_{{_{2}}}{{\mathcal D}}_{{_{3}}}<0$ and ${s}_{{_{2}}}{s}_{{_{3}}}>0$: $(\pi+,\pi-,0-,0-)$; $(\pi+,\pi+,0+,0-)$; $(\pi+,0-,\pi-,0-)$; and $(\pi+,0+,\pi+,0-)$. However, they are not in-line. The angle between the incident and reflected beams is $4(\theta_{\mathrm D}-\pi/2)$.

In the present paper, we have chosen the in-line high-dispersion-rate CDDW optic in the ($\pi+$,$0-$,$0+$,$0-$) configuration, as a dispersing element D$_{{_{\mathrm {{D}}}}}$ of the defocusing system $\hat{O}_{{_{\mathrm {{D}}}}}$, see Figs. 3 and \[fig00399\]. The in-line high-dispersion-rate CDDW optic in the ($\pi+$,$\pi+$,$\pi-$,$0-$) configuration, was chosen as a dispersing element D$_{{_{\mathrm {{R}}}}}$ of the refocusing system $\hat{O}_{{_{\mathrm {{R}}}}}$, see Figs. 4 and \[fig0049\].

Tables \[tab1\] and \[tab14\] present crystal parameters and cumulative 