Dangzhong Gao

White-Light Interferometry for Measuring Fuel Pressure in ICF Polymer-Microsphere Targets

Abstract A new technique based on a vertical scanning white-light interferometry is developed for measuring fuel pressure in inertial confinement fusion (ICF) multiple-shell polymer-microsphere targets. Nuclear fuel pressure is an essential parameter for estimating fusion efficiency in ICF experiments. This parameter is difficult to determine because of complicated target structures, short measurement time, relatively short optical path length changes, and expansion of the target after pressurization. To reduce the effects due to changes in diameter, a model is proposed to correct for the expansion at the radial orientation for multiple-shell polymer microspheres. The model is compared to a destructive method, and D2 fill pressure accuracy is confirmed within a 10% error of uncertainty.

Determination of Doped Concentrations in ICF Shells by X-Ray Equivalent Absorption

Abstract An X-ray equivalent absorption technique is developed to determine the doped concentrations of the inertial confinement fusion shells. Doped atoms in the shells are used to increase the opacity for radiation, to improve the absorptive capacity of the shell wall for X-ray, and to restrain the growth of hydromechanics instability. The doped concentrations in the shells are difficult to determine for the relatively thick shell wall and the spatial resolution. A novel model is proposed to determine the doped concentrations by a theory of X-ray equivalent absorption. The advantage of this model is that optical density (D) and the exposure curve [D = Φ(I)] of film plates are not necessary to calculate the doped concentrations. The model is validated with a thickness error of 2% by the polypropylene step wedge, the aluminum step wedge, and the polystyrene sphere. The error of results for doped concentration between this method and the energy-dispersive spectroscopy method is less than 0.1 at. %. The uncertainty also is analyzed and the combined expanded uncertainty is better than 0.2 at. % for the Ge-doped glow discharge polymer shell (k = 2).

Theoretical and experimental investigation of surface acoustic wave propagation on a hollow spherical shell using laser ultrasound

An analytical model of surface acoustic waves on the surface of a hollow spherical shell generated by a pulsed laser source is proposed using the Legendre polynomials expansion and contour integration method. The model predicts two interesting phenomena. The dispersive characteristic of thick spherical shells is mainly determined by the spherical Rayleigh waves, but the corresponding characteristic of thin spherical shells is dominated by zero-order anti-symmetric plate waves; The hollow spherical spheres with the same ratio of thickness to radius have the same dispersive characteristic. Using laser ultrasound technique, the proposed model is confirmed experimentally on a hollow polymer sphere of mm-sized diameter.