In situ areal mass measurement of laser shock-loaded aluminum using point-projection x-ray backlighting.

X-ray backlighting is been widely used today in dynamic phenomena observation. By applying proper synchronizing techniques, the in-situ data of the intensity distribution of the fragments in laser-driven shock-loaded aluminum were obtained for a particular moment using x-ray backlighting imaging. The image resolution was better than 40 µm in this context by introducing a pinhole. In order to obtain the areal mass of the fragments, a set of reference Al step wedges with certain thicknesses was employed. Furthermore, a novel, to the best of our knowledge, calibration method is introduced to calibrate the x-ray intensity distribution. It was effective to decrease the non-uniformity influence of the x-ray intensity with this calibration method by simulating a light field. After calibration, the standard deviation of 30 regions of interest reduced to 4.17%. In consequence, the areal mass distribution of the fragments is well quantified. It should be noted that the uncertainty in the areal mass conversion mainly comes from the non-uniformity of the x-ray intensity distribution with about 5% and the measurement uncertainty of the step thicknesses with less than 10%.

A new nonlinear reconstruction method based on total variation regularization of neutron penumbral imaging.

Neutron penumbral imaging is a significant diagnostic technique in laser-driven inertial confinement fusion experiment. It is very important to develop a new reconstruction method to improve the resolution of neutron penumbral imaging. A new nonlinear reconstruction method based on total variation (TV) regularization is proposed in this paper. A TV-norm is used as regularized term to construct a smoothing functional for penumbral image reconstruction in the new method, in this way, the problem of penumbral image reconstruction is transformed to the problem of a functional minimization. In addition, a fixed point iteration scheme is introduced to solve the problem of functional minimization. The numerical experimental results show that, compared to linear reconstruction method based on Wiener filter, the TV regularized nonlinear reconstruction method is beneficial to improve the quality of reconstructed image with better performance of noise smoothing and edge preserving. Meanwhile, it can also obtain the spatial resolution with 5 µm which is higher than the Wiener method.