X-ray four-quadrant diamond phase-retarder system to compensate for off-axis and chromatic aberrations

Abstract

An X-ray transmission-type double phase-retarder system that can compensate for off-axis aberration (phase-shift inhomogeneity due to angular divergence of incident X-rays) has been developed and its advantage over a conventional single transmission-type X-ray phase retarder was demonstrated. However, it was noticed that the transmission-type X-ray phase retarder suffers from not only off-axis aberration but also chromatic aberration (phase-shift inhomogeneity due to energy spread of incident X-rays). In this paper, a transmissiontype X-ray four-quadrant phase-retarder system is proposed that can compensate for both off-axis and chromatic aberrations. The X-ray fourquadrant phase-retarder system is composed of four transmission-type X-ray phase retarders. The scattering planes of four phase-retarder diamond crystals are set to be inclined by 45 HH angular divergence (FWHM) of incident X-rays, the X-ray fourquadrant phase-retarder system created 0.98 degree of vertical-linear polarization from horizontal-linear polarization. This value was favorably compared to 0.89 and 0.96, which were obtained by the single and double phase-retarder systems, respectively. The principle of the X-ray four-quadrant phase-retarder system will be described together with its advantage over the single and double phase-retarder systems.

Development and application of aberration-compensating x-ray phase retarder systems

“…9(c) with a condition that horizontal beam divergence and energy spread of incident x rays were 45 arcsec and 1.5 eV, respectively. 20 In the cases of Figs. 9(a) and 9(b), the maximum degrees of vertical polarization were 0.89 and 0.96, respectively.…”

“…9(a) and 9(b), the maximum degrees of vertical polarization were 0.89 and 0.96, respectively. 20 It is clear that the two-quadrant geometry corresponding to the two-quadrant phase retarder system 19 creates higher degrees of vertical polarization than the one-quadrant geometry corresponding to a single phase retarder. This is owing to the effect of compensation for off-axis aberration.…”

“…Rate of residual horizontally polarized component of x rays which was converted from the horizontal polarization by the four-quadrant phase retarder system. 20 This was measured at station BL-15C of the Photon Factory whose distance from radiation source is about 30m. The angular divergence and energy spread of incident x rays were 20 arcsec and 0.5 eV, respectively, The abscissa is ∆θ4.…”

“…Bragg-reflected x rays from four phase retarders are monitored by four PIN photo-diodes. 20 The energy of x rays was adjusted to be 7709 eV (cobalt K-absorption edge). Throughput of x rays transmitted by the four phase retarders was 0.13.…”

“…In parts (Q1), (Q2), (Q3) and (Q4), dispersion surfaces corresponding to phase retarders giving Bragg reflections in the directions of the first, second, third and fourth quadrants, respectively, viewed from the downstream direction, are drawn 20. …”