More are better, but the details matter: combinations of multiple Fresnel zone plates for improved resolution and efficiency in X-ray microscopy

Li, K.; Jacobsen, C.

doi:10.1107/S1600577518007208

Figure 4
While there might be practical limitations to the number of zone plates n_zp that can be stacked together, one can obtain gains in first-order diffraction efficiency $[\varepsilon_{1}]$ that go well beyond the simple thin zone plate expression of equation (1)

. In (a) we show the efficiency as a function of individual zone plate thickness t_i and cumulative thickness t, where n_zp = t/t_i zone plates are used with with a separation of $[\Delta z]$ = 10 µm (for d = 45 µm, and dr_N = 25 nm for the first zone plate at 10 keV). A single gold zone plate with the optimum thickness t_opt = 2.0 µm would give $[\varepsilon_{1}]$ = 32.7%, whereas much higher efficiencies can be obtained by using many more zone plates with slightly higher cumulative thickness. In (b) we show how the stacking of n_zp = 8 zone plates, each with a thickness t_i = 0.5 µm, leads to differences in diffraction efficiency as one changes the separation distance $[\Delta z]$ between zone plates. Smaller separation distances $[\Delta z]$ are preferable but might be impractical, but even with larger separation distances like $[\Delta z]$ = 1000 µm one can still obtain an efficiency of $[\varepsilon_{1}]$ = 36% if n_zp = 5 zone plates are used. All calculations were for gold zone plates at 10 keV.

JOURNAL OF
SYNCHROTRON
RADIATION

ISSN: 1600-5775

Volume 25| Part 4| July 2018| Pages 1048-1059

https://doi.org/10.1107/S1600577518007208

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