We study optical properties of optomagnetic metamaterials produced by regular arrays of double gold dots (nanopillars). Using combined data of spectroscopic ellipsometry, transmission and reflection measurements, we identify localized plasmon resonances of a nanopillar pair and measure their dependences on dot sizes. We formulate the necessary condition at which an effective field theory can be applied to describe optical properties of a composite medium and employ interferometry to measure phase shifts for our samples. A negative phase shift for transmitted green light coupled to an antisymmetric magnetic mode of a double-dot array is observed.

Perturbations of inertial confinement fusion hotspots from spherical symmetry cause an increase in the implosion velocity required for ignition, as investigated analytically by [R. Kishony and D. Shvarts, Phys. Plasmas 8, 4925 (2001)] and in numerical studies by many authors. In this paper, we analyse the mechanisms behind this effect by comparing fully 3D fluid simulations of National Ignition Facility targets to a novel analytic model of the thermal energy balance of the hotspot. The analytic model takes into account the radial variation of the state variables within the hotspot and provides an accurate relationship between the hotspot's 0D parameters (ρc, Tc, R, uR, and q) and its heating and cooling rates. The dominant effect of perturbations appears to be an increase in the inflow velocity at the hotspot's surface due to transverse flow of material between perturbation structures, causing premature thermalisation of kinetic energy before the hotspot is fully compressed. In hotspots with a broad perturbation spectrum, thermalisation of energy is inhibited by nonradial motion introduced by mode-mode interaction, reducing the yield further.

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Abstract. ICF simulations were carried out with the amplitude of perturbations from spherical symmetry treated as a free parameter with the aim of reproducing experimentally observed yields. The simulations began at peak velocity and multi-wavelength perturbations were imposed in the velocity field. It was found that increasing the perturbation caused the gamma bang time to lag behind the xray bang time. Fluid motion broadening of the neutron spectrum was also examined. The effect of perturbation amplitude on alpha particle losses was investigated.

The products of nuclear reactions in a plasma have high energies and non-Maxwellian distributions. These introduce difficulties when modeling burning plasmas. In this work we describe a suite of tools developed to include the effects of reaction products in computational models. In particular, we focus on alpha particle transport and heating and on neutron emission. Our goal is to accurately model these two species in 3D Gorgon simulations of NIF and MagLIF implosions.Confinement and slowing down of alpha particles is important for ignition in all inertial fusion schemes. The alpha species is modeled kinetically, by coupling a PIC code with Gorgon. This model fully resolves the dependence of the alpha slowing-down rate on the alpha particle energy and allows for an anisotropic distribution of alpha particles in a computational cell. This facilitates an accurate determination of the regions undergoing alpha heating in 3D ICF simulations. In the case of MagLIF, the unique magnetic field topology in a Z-pinch results in significant nonlocal transport and heating by the alpha particles. Such effects can be difficult to include using a diffusion model of alpha transport and can affect the burn dynamics in MagLIF.Neutrons emitted by a thermal plasma undergo a Doppler broadening that can be used to infer the plasma temperature. However, in dense plasmas there are a number of other effects, including fluid velocity and neutron scattering, that can affect the emitted neutron spectrum. We have developed a post-processing tool incorporating these effects that generates synthetic neutron spectra from 3D simulations of NIF experiments. ________________________________ * Work supported by Sandia National Laboratories