Design of Elliptical Reflection Zone Plate for Monochromatization of the Ultrafast Betatron Radiation at Low Energy Band

Abstract

The elliptical reflection zone plate is a kind of optical element in soft x-ray and x-ray ranges and has focusing and dispersion properties. Compared with a transmission zone plate, the required dispersion orders can be easily separated from zeroth order diffraction. It is fabricated on a bulk substrate and does not have much difficulty in the fabrication process. We design a 1000-zone off-axis elliptical reflection zone plate for the monochromatization of the ultrafast betatron radiation at the low energy band, at the designed wavelength of 2.478nm (500 eV) which is an important spectral part of the betatron radiation, with high spatial resolution, high spectral resolution. Moreover, we simulate the designed reflection zone plate properties. The simulation results show that the spatial resolutions in the spatial direction and the spectral direction are 6.4 μm and 7.3 μm (full width half maximum), respectively, and the spectral resolution reaches up to 496 for the well aligned point source system, which is in good agreement with the theoretical predictions. In addition, we discuss some factors influencing the spectral and spatial resolution, such as the zone number, zone area and the incidence wavelength. The elliptical reflection zone plate also has potential applications in investigating x-ray fluorescence spectra and other fields.