7th International Conference on Matter and Radiation at Extremes (ICMRE2024)

X-ray spectroscopy is widely used in many fields such as astronomy, materials science, and high energy density physics. In these applications, there are many cases of weak signals, such as X-ray Thomson scattering, characterization of doped elements for inertial confinement fusion (ICF) implosion, picosecond time-resolved diagnostics, and extended X-ray absorption fine structure (EXAFS) spectroscopy. Conventional energy spectroscopy methods fail to obtain observable signals in these cases.  However，the diagnosis of such weak signals can provide key physical quantities of complex processes with high temporal resolution, addressing urgent related needs. Internationally, various bent crystal-based diagnostic techniques have been developed based on this requirement, but they all have certain limitations. In this study, we explore a multi-cone crystal diagnostic technique that uses a special focusing principle to continuously adjust the curvature radius and the angle of curvature tilt at each position of the crystal, enabling the spectrum to have a flat focusing detection surface and achieve efficient X-ray energy spectroscopy diagnostics. In terms of numerical simulations, we use the newly developed X-ray diagnostic simulation platform XCD to simulate the optical path of the multi-cone crystal, which can achieve over a hundred times more light collection efficiency compared to similar flat crystals. Through continuous exploration and practice, the modeling accuracy, manufacturing processes, and detection techniques of complex curved crystals have all been improved, resulting in significantly improved focusing effects. In X-ray diffraction laboratories, Xingguang-III, and Shenguang-III prototype Facilities, high signal-to-noise experimental images have been obtained, with a focal efficiency about 150 times higher than that of flat crystals. The focusing scale of the Ti He-α characteristic spectrum line reaches 88 micrometers, far surpassing the international best results. In experiments on the implosion of doped elements on a 100-kilojoule laser facility, aiming at the Ar element beta line emission, which has a thin optical depth of plasma, we have designed and developed a multi-cone crystal diffraction system coupled with an X-ray stripe camera. This system tackles a series of engineering problems related to the restricted space coupling between the multi-cone crystal and the stripe camera, precise focusing and alignment, and online auxiliary observation. The experiment obtained high temporal resolution spectroscopic images in the tens of picoseconds level, whereas no signal could be observed using a flat crystal. For the first time, crucial spectral line information from the hot-spot plasma in the thick shell target has been obtained, enabling the deduction of the temporal evolution process of the plasma state in the implosion fusion hot-spot, providing data support for numerical simulations and physical understanding. This diagnostic technique can be adapted to different experimental layouts and energy ranges, and can be coupled with various types of recording devices, providing a high light collection efficiency diagnostic solution for various weak X-ray physical processes, and has broad prospects for applications.
 

X-ray diagnostic,spectrometer,high sensitivity,multi-cone crystal,time resolution