Three-dimensional hot-spot x-ray emission tomography from cryogenic deuterium–tritium direct-drive implosions on OMEGA

• Published in: Review of scientific instruments 2022-09, Vol.93 (9), p.093530-093530
• Main Authors: Churnetski, K., Woo, K. M., Theobald, W., Radha, P. B., Betti, R., Gopalaswamy, V., Igumenshchev, I. V., Ivancic, S. T., Michalko, M., Shah, R. C., Stoeckl, C., Thomas, C. A., Regan, S. P.
• Format: Article
• Language: English
• Subjects: Asymmetry; Deuterium; Emission analysis; Illumination; Image reconstruction; Implosions; Inertial confinement fusion; Lasers; Perturbation; Scientific apparatus & instruments; Spherical harmonics; Steady state models; Three dimensional models; Tritium
• ISSN: 0034-6748; 1089-7623
• DOI: 10.1063/5.0098977

A three-dimensional model of the hot-spot x-ray emission has been developed and applied to the study of low-mode drive asymmetries in direct-drive inertial confinement fusion implosions on OMEGA with cryogenic deuterium–tritium targets. The steady-state model assumes an optically thin plasma and the data from four x-ray diagnostics along quasi-orthogonal lines of sight are used to obtain a tomographic reconstruction of the hot spot. A quantitative analysis of the hot-spot shape is achieved by projecting the x-ray emission into the diagnostic planes and comparing this projection to the measurements. The model was validated with radiation-hydrodynamic simulations assuming a mode-2 laser illumination perturbation resulting in an elliptically shaped hot spot, which was accurately reconstructed by the model using synthetic x-ray images. This technique was applied to experimental data from implosions in polar-direct-drive illumination geometry with a deliberate laser-drive asymmetry, and the hot-spot emission was reconstructed using spherical-harmonic modes of up to ℓ = 3. A 10% stronger drive on the equator relative to that on the poles resulted in a prolate-shaped hot spot at stagnation with a large negative A2,0 coefficient of A2,0 = −0.47 ± 0.03, directly connecting the modal contribution of the hot-spot shape with the modal contribution in laser-drive asymmetry.