Talbot-Lau x-ray interferometry for high energy density plasma diagnostic

Abstract

High resolution density diagnostics are difficult in high energy density laboratory plasmas (HEDLP) experiments due to the scarcity of probes that can penetrate above solid density plasmas. Hard x-rays are one possible probe for such dense plasmas. We study the possibility of applying an x-ray method recently developed for medical imaging, differential phase-contrast with Talbot-Lau interferometers, for the diagnostic of electron density and small-scale hydrodynamic instabilities in HEDLP experiments. The Talbot method uses micro-periodic gratings to measure the refraction and ultra-small angle scatter of x-rays through an object and is attractive for HEDLP diagnostic due to its capability to work with incoherent and polychromatic x-ray sources such as the laser driven backlighters used for HEDLP radiography. Our paper studies the potential of the Talbot method for HEDLP diagnostic, its adaptation to the HEDLP environment, and its extension of high x-ray energy using micro-periodic mirrors. The analysis is illustrated with experimental results obtained using a laboratory Talbot interferometer.

Talbot-Lau based Moiré deflectometry with non-coherent sources as potential High Energy Density plasma diagnostic

“…Unlike attenuation methods, x-ray refraction based imaging techniques provide stronger contrast for HED laboratory plasma experiments 12 since in low-Z matter the real part of the complex index of refraction n ¼ d þ ib (related to refraction) is much larger than the imaginary part (related to attenuation). 6,13 The effects of x-ray refraction have been observed previously in HED studies of jets, as well as in laser-shocked material imaging. 14,15 Thus, phase-contrast techniques have been developed, 16 for example, a refraction based density gradient diagnostic utilized the propagation phase-contrast method to enhance the visibility of particular features of interest with a small focal spot, quasi-coherent backlighter of several keV.…”

“…These densities will strongly refract x-rays depending on their energies, e.g., for x-rays of 10-20 keV, angles of up to $100 lrad are expected. 6 The aforementioned ICF characteristics impose certain conditions on the diagnostics used to characterize these implosion plasmas. In particular, the TL system should allow for high object magnification (M > 10) configurations in order to achieve high resolutions as well as high Talbot magnifications.…”

“…It can be used to characterize material interfaces as well as internal density gradients, thus making it an attractive tool for a wide range of applications in material science, energy research, biomedical imaging, and High Energy Density (HED) plasma studies. [1][2][3][4][5][6][7][8] The TL interferometer can be adapted from a standard medical setup 8 according to the requirements of HED experiments, 6 particularly for Inertial Confinement Fusion (ICF) 9 diagnostics. ICF capsules are compressed from a few millimeters diameter to a tens of microns diameter hot spot, hence creating high density regions with sharp gradients; thus, the description of a typical HED plasma feature requires a spatial resolution of $10 lm, achievable by means of large object magnifications.…”

Single-shot Z_eff dense plasma diagnostic through simultaneous refraction and attenuation measurements with a Talbot–Lau x-ray moiré deflectometer

“…The phase shifts of a system where the real part of the refractive index is proportional to the electron density, can be measured through TXD [4][5][6], which is the case for plasmas that follow the dispersion relation for nonmagnetized plasmas. In the TXD technique, the fringe shift obtained from the moiré image is proportional to the electron density.…”

“…Recently, we have made the technique suitable for high energy density (HED) diagnostics of electron density [4][5][6] in the moiré deflectometry configuration motivated by the single-shot restriction of these experiments. Attenuation x-ray radiography, based on photoabsorption and Compton scattering of x rays, is the most common density diagnostic in HED experiments [7][8][9].…”