In the field of target diagnostics for Initial Confinement Fusion experiment, high resolution X-ray imaging system is
seriously necessary to record the evolution details of target ablation-front disturbance at different energy points of backlight
conditions. Kirkpatrick-Baez mirror is a wide used imaging system to achieve a large efficient field of view with high
spatial resolution and energy transmitting capability. In this paper, we designed a novel type of reflective microscope based
on Kirkpatrick-Baez structure, and this system can achieve 5μm spatial resolution at 600μm field of view specific energy
point in one dimension.
A large-field high-resolution x-ray microscope was developed for multi-keV time-resolved x-ray imaging diagnostics of laser plasma at the Shenguang-III prototype facility. The microscope consists of Kirkpatrick–Baez amélioré (KBA) bimirrors and a KB single mirror corresponding to the imaging and temporal directions of a streak camera, respectively. KBA bimirrors coated with an Ir single layer were used to obtain high spatial resolutions within the millimeter-range field of view, and a KB mirror coated with Cr/C multilayers was used to obtain a specific spectral resolution around 4.3 keV. This study describes details of the microscope with regard to its optical design, mirror coatings, and assembly method. The experimental imaging results of the grid with 3 to 5 μm spatial resolution are also shown.
The radial structure of core temperature and density is very important to benchmark theory simulation codes in Inertial confinement fusion (ICF) studies. In this article, we gave a method to determinate the radial structure of core temperature and density by using the normalized intensity of core experimental x-ray image. The core emission model uses the average atom model (AA) and the radiation transport model assumes the local thermo dynamic equilibrium model (LTE). Calculated results show that: the full width at half maximum of core temperature is about 39.4μm which indicate that the hot spot diameter is such value and the full width at half maximum of core density is about 5μm. The hot spot convergence and the shell in-flight aspect ratio (IFAR) can be deduced approximately 7 and 7.5 respectively. The above assist us to better understand the implosion physics, and provide more information for benchmarking the simulation codes.
An auxiliary visible imaging method was introduced to solve the axial and pointing
alignment of x-ray Kirkpatrick-Baez optics. Through ZEMAX simulation and x-ray imaging
experiments, the axial and pointing alignment accuracy were determined to be ±300μm and
±20μm respectively. The numerical aperture of x-ray Kirkpatrick-Baez optics is rather small, so
it's impossible to adjust Kirkpatrick-Baez system by visible imaging directly. An auxiliary visible
lens was designed, which was equivalent to x-ray Kirkpatrick-Baez optics on conjugate
relationship and accuracy control. The comparative experiments of visible imaging and x-ray
imaging indicate that this auxiliary system could meet the alignment accuracy of Kirkpatrick-Baez
A micro-channel plate (MCP) transmissivity is calibrated using the 3B3 medium energy X-ray beamline (from 2.0 to 5.5keV) on Beijing Synchrotron Radiation Facility (BSRF). MCP transmissivity near the two ends of low-energy 2.0keV and high-energy 5.5keV is higher than the middle part. We calculate reflectivity and transmission in the pores array of MCP respectively, and take the experiment result into account synthetically. It uncovers that the grazing incident X-ray
in pores results in the total reflection, and the reflectivity rises as the X-ray energy decreases, which successfully explains the peculiar phenomena of the high transmissivity in low energy.