Multiple-view spectrally resolved x-ray imaging observations of polar-direct-drive implosions on OMEGA

Abstract

We present spatially, temporally, and spectrally resolved narrow-and broad-band x-ray images of polar-direct-drive (PDD) implosions on OMEGA. These self-emission images were obtained during the deceleration phase and bang time using several multiple monochromatic x-ray imaging instruments fielded along two or three quasi-orthogonal lines-of-sight including equatorial and polar views. The instruments recorded images based on K-shell lines from a titanium tracer located in the shell as well as continuum emission. These observations constitute the first such data obtained for PDD implosions. The image data show features attributed to zero-order hydrodynamics. Equatorial view synthetic images obtained from post-processing a 2D hydrodynamic simulation are consistent with the experimental observation. Polar view images show a pentagonal pattern that correlates with the PDD laser illumination used on OMEGA, thus revealing a 3D aspect of these experiments not previously observed.

Assessment of transient effects on the x-ray spectroscopy of implosion cores at OMEGA

“…Significant advances made in inertial confinement fusion (ICF) research have been enabled by x-ray spectroscopy, thus contributing to a better interpretation of the underlying physics and target performance, and to improvements in the predictive capability of simulation codes [1,2]. Among these achievements are: the measurement of target preheat due to fast electrons by means of Kα emission spectroscopy [3][4][5]; the extraction of spatially averaged electron temperature and density in implosion cores of direct-and indirect-drive implosions by analyzing Starkbroadened K-and L-shell line emissions [6][7][8][9][10][11][12][13][14]; the use of K-shell absorption spectroscopy to infer the conditions of the relatively cold imploding shell that confines the core [15][16][17][18][19]; the simultaneous determination of time-and space-averaged conditions for both core and shell in thick-wall targets by accounting for the attenuation of core x-ray emission in the compressed shell [20]; the time-resolved characterization and energy balance analysis of implosion core in shock-ignition experiments [21]; the quantitative evaluation of mixing of ablator material into the hot-spot of ignition-scale targets from the K-shell emission of mid-Z dopant elements [22][23][24]; the extraction of spatial profiles of temperature and density from the analysis of x-ray spectra and narrow-band images [25][26][27]; the asymmetry measurement of plasma temperature and density spatial profiles from pinhole space-resolved spectra [28]; and the observation of three-dimensional and laser imprinting effects in polar-drive implosions with gated spectrally resolved x-ray imaging [29]. Furthermore, the conditions achieved in laser-driven ICF capsules are similar to those in stellar interior environments, so this progress in ICF research is also likely to benefit applications in astrophysics [30].…”