SIMULTANEOUS MEASUREMENT OF SHOCK-WAVE VELOCITY AND ULTRA-HIGH DENSITY WITH PENUMBRAL X-RAY BACKLIGHT TECHNIQUE

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The ultra-high pressure-density equation of state (EOS) must be accurately known for inertial fusion energy (IFE) study, astrophysics and other related fields. Hugoniot measurement with impedance-mismatching method is not the best for low-Z materials such as hydrogen/deuterium or plastics. High-resolution radiography allows us to obtain absolute Hugoniot parameters; the shock-wave velocity, particle (pusher) speed, and ultra-high density. We suggest Penumbral coded-aperture-imaging (CAI) as high magnification and resolution radiography. Since EOS experiment need one-dimensional compression by planar shock-waves, the 2-D resolution in space is not required. Thus, we can use a streak camera system as a detector, and also a simple knife-like aperture.In this study, we report a proof of principle experiment to develop an advanced penumbral x-ray backlight technique, streaked penumbral coded-aperture-imaging (SP-CAI). We obtained time-resolved penumbral image of x-ray from laser plasma for the first time. The improved algorithms of two digital inverse filters were tested. The parametric Wiener inverse filter provided a better reconstruction. A 23μm source size at a full width half maximum (FWHM) is measured with a 0.07μm two-point spatial and a 25ps temporal resolutions (1.27 μm overall spatial resolution). Compared to the size of the x-ray light source observed simultaneously with an x-ray pinhole camera, a typical size of the reconstructed source is about half (FWHM) which is the 23μm. This clearly represents a time-integration effect of the pinhole camera image.This imaging method potentially has temporal and spatial resolutions for future high-compressibility measurements in equation-of-state (EOS) studies.