High-resolution X-ray monochromatic imaging for laser plasma diagnostics based on toroidal crystal

Abstract Monochromatic X-ray imaging is an essential method for plasma diagnostics related to density information. Large-field high-resolution monochromatic imaging of a He-like iron (Fe XXV) Kα characteristic line (6.701 keV) for laser-plasma diagnostics was achieved with the developed toroidal crystal X-ray imager. A high-index crystal orientation Ge <531> wafer with a Bragg angle of 75.37° and the toroidal substrate was selected to obtain sufficient diffraction efficiency and compensate for astigmatism under oblique incidence. The precise offline assembly method of the toroidal crystal imager based on energy substitution was proposed, and a spatial resolution of 3–7 μm was obtained by toroidal crystal imaging of a 600 line-pairs/inch Au grid within the object field of view larger than 1.0 mm. The toroidal crystal X-ray imager has been successfully tested through the side-on backlight imaging experiments of the sinusoidal modulation target and 1000 line-pairs/inch Au grid with a linewidth of 5 μm using the online alignment method based on the dual positioning balls to indicate the target and backlighter. This paper describes the optical design, adjustment method, and experimental results of a toroidal crystal system in a laboratory and laser facility.