High resolution X-ray diagnosis is a significant method for obtaining ablation-front and trajectory measurements targeting Rayleigh-Taylor (RT)-instability growth in initial confinement fusion (ICF) experiments. In this paper, a novel Kirkpatrick-Baez-type structure, as a kind of essential X-ray micro-imaging apparatus, has been developed that realizes a large field of view (FOV) and images with high resolution and energy response. Zoned multilayer coating technology is applied to the Kirkpatrick-Baez mirrors to transmit two specific quasi-monochromatic light through the same mirror and enables a compact dual-channel structure. This microscope has been assembled in the laboratory and later implemented at the Chinese SG-III laser facility. The characterization results show that this imaging system can achieve a good spatial resolution of 5 µm in a large FOV of 500 µm, while maintaining a strong monochromatic performance with bandwidth of 0.5 keV at 2.5 keV and 4.3 keV respectively.
This article presents the development of an x-ray eight-image Kirkpatrick-Baez diagnostic system to be used at China's Shenguang-III (SG-III) laser facility in aspects of the optical design, multilayers, and online/offline tests. Six pieces of concave spherical substrates are used for constituting a special optical structure. Dual-periodic tungsten/carbon (W/C) multilayers are used for high reflectivity and large angular bandwidth of ∼0.1°. The global spatial resolution is ∼5 μm in the ±100 μm range. The schemes of system installation, transport, collimation, and image acquisition at China's SG-III facility are also discussed.
Direct intensity calibration of X-ray grazing-incidence microscopes is urgently needed in quantitative studies of X-ray emission from laser plasma sources in inertial confinement fusion. The existing calibration methods for single reflecting mirrors, crystals, gratings, filters, and X-ray detectors are not applicable for such X-ray microscopes due to the specific optical structure and the restrictions of object-image relation. This article presents a reliable and efficient method that can be performed using a divergent X-ray source and an energy dispersive Si-PIN (silicon positive-intrinsic-negative) detector in an ordinary X-ray laboratory. The transmission theory of X-ray flux in imaging diagnostics is introduced, and the quantities to be measured are defined. The calibration method is verified by a W/Si multilayer-coated Kirkpatrick-Baez microscope with a field of view of ∼95 μm at 17.48 keV. The mirror reflectance curve in the 1D coordinate is drawn with a peak value of 20.9% and an uncertainty of ∼6.0%.
High-precision x-ray imaging diagnostics of hotspot at the stagnation stage are essential for regulating implosion asymmetry and retrieving physical implosion parameters. With regard to 10–20 keV energy band imaging, existing diagnostic instruments such as Kirkpatrick–Baez microscopes and pinhole cameras are insufficient in terms of spatial resolution and collection efficiency. The situation is even worse when high-speed, time-resolved imaging diagnostics are performed by coupling framing cameras or line-of-sight imagers. This article presents the basic principles and optical system design of a 17.48 keV modified Wolter x-ray microscope, to resolve the problems encountered in high-energy imaging diagnostics. The proposed optical configuration offers a better spatial resolution, greater depth of field, and preliminary compliance with the requirements of high precision optical processing techniques. The spatial resolution is better than 1 µm in a field range ±150 µm, and is better than 3 µm in a total field of view ∼408 µm in diameter. The geometric solid angle is calculated as 3.0 × 10−5 sr and is estimated to be 1.2 × 10−6 sr, considering the reflectivity of the double mirrors. The proposed microscope is expected to effectively improve spatial resolution and signal-to-noise ratio for high-energy imaging diagnostics.
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