1. Increasing Hydrodynamic Efficiency by Reducing Cross-Beam Energy Transfer in Direct-Drive-Implosion Experiments
- Author
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V. Yu. Glebov, F. J. Marshall, T. C. Sangster, Christian Stoeckl, D. H. Edgell, Igor V. Igumenshchev, C. Sorce, Jacek Kwiatkowski, S. Stagnitto, Dustin Froula, P. B. Radha, W. Seka, D. T. Michel, V. N. Goncharov, and Russell Follett
- Subjects
Physics ,Range (particle radiation) ,Amplitude ,Series (mathematics) ,law ,Transfer (computing) ,General Physics and Astronomy ,Implosion ,Absorption (logic) ,Radius ,Laser ,law.invention ,Computational physics - Abstract
A series of experiments to determine the optimum laser-beam radius by balancing the reduction of cross-beam energy transfer (CBET) with increased illumination nonuniformities shows that the hydrodynamic efficiency is increased by $\ensuremath{\sim}35%$, which leads to a factor of 2.6 increase in the neutron yield when the laser-spot size is reduced by $20%$. Over this range, the absorption is measured to increase by $15%$, resulting in a $17%$ increase in the implosion velocity and a $10%$ earlier bang time. When reducing the ratio of laser-spot size to a target radius below 0.8, the rms amplitudes of the nonuniformities imposed by the smaller laser spots are measured at a convergence ratio of 2.5 to exceed $8\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$ and the neutron yield saturates despite increasing absorbed energy, implosion velocity, and decreasing bang time. The results agree well with hydrodynamic simulations that include both nonlocal and CBET models.
- Published
- 2012