Advances in target design and fabrication for experiments on NIF

Abstract

The ability to build target platforms for National Ignition Facility (NIF) is a key feature in LANL's (Los Alamos National Laboratory) Target Fabrication Program. We recently built and manufactured the first LANL targets to be fielded on NIF in March 2011. Experiments on NIF require precision component manufacturing and accurate knowledge of the materials used in the targets. The characterization of foams and aerogels, the Be ignition capsule, and machining unique components are of main material focus. One important characterization metric the physics' have determined is that the knowledge of density gradients in foams is important. We are making strides in not only locating these density gradients in aerogels and foams as a result of how they are manufactured and machined but also quantifying the density within the foam using 3D confocal micro x-ray fluorescence (XRF) imaging and 3D x-ray computed tomography (CT) imaging. In addition, collaborative efforts between General Atomics (GA) and LANL in the characterization of the NIF Ignition beryllium capsule have shown that the copper in the capsule migrates radially from the capsule center. 1. ELEMENTAL DIFFUSION THROUGH IGNITION CAPSULES Recent collaborations with LANL and General Atomics (GA) have focused on analysis of ignition capsules, specifically elemental migration throughout the ignition capsules. Currently, the leading choice in the point design for the ignition capsules are graded doped Cu-Be capsules with the secondary design being Ge doped CH capsules. Both of these capsule types were analyzed using 3D confocal XRF imaging and 3D x-ray CT imaging for possible elemental migration. 1.1 Analysis of copper migration in graded doped Cu-Be ignition capsules Previous studies at GA using contact radiography indicated migration of the Cu dopant in the capsule shell. In addition, SEM (scanning electron microscopy) images of pre- and post-pyrolysis indicates formation of domes on the surface of the capsules post-pyrolysis. We believe this is due to thermal migration of copper during the pyrolysis step. It is well known and documented in materials science literature that copper readily migrates when subjected to higher thermal conditions. (1) Since the dome features are seen on the capsule surface after pyrolysis, we believe these domes are that of copper migrating to the surface. To determine if the Cu migration occurred radially throughout the capsule, a few ignition capsules were given to LANL to study. Using a combination of 3D x-ray CT imaging and