Engineering topics

Wu, K. J.

Publications and source records attributed to Wu, K. J..

4 records

DOE OSTI2016

Equation of state, adiabatic sound speed, and Gruneisen coefficient of boron carbide along the principal Hugoniot to 700 GPa

We describe a new equation of state (EOS) experimental technique that enables the study of thermodynamic derivatives into the TPa regime and apply it to boron carbide (B4C). The data presented here are the first principal Hugoniot sound speed measurements reported using a laser-driven shock platform, providing a new means to explore the high-pressure off-Hugoniot response of opaque materials. Furthermore, the extended B4C Hugoniot suggests the presence of a new high-pressure phase, as recently predicted by molecular dynamics simulations, adding to the complexity of the existing phase diagram.

36 MATERIALS SCIENCE↗

DOE OSTI2015

Performance and Mix Measurements of Indirect Drive Cu-Doped Be Implosions

The ablator couples energy between the driver and fusion fuel in inertial confinement fusion (ICF). Because of its low opacity, high solid density, and material properties, beryllium has long been considered an ideal ablator for ICF ignition experiments at the National Ignition Facility. We report here the first indirect drive Be implosions driven with shaped laser pulses and diagnosed with fusion yield at the OMEGA laser. The results show good performance with an average DD neutron yield of ~2 × 10⁹ at a convergence ratio of R₀/R ~ 10 and little impact due to the growth of hydrodynamic instabilities and mix. In addition, the effect of adding an inner liner of W between the Be and DD is demonstrated.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2013

Thin Oxides as a Cu Diffusion Barrier for NIF Be Ablator Capsules

The NIF point design uses a five-layer capsule to modify the X-ray absorption in order to achieve optimized shock timing. A stepped copper dopant design defines the layer structure. The production of the capsule involves pyrolysis to remove the inner plastic mandrel. Copper atoms diffuse radially and azimuthally throughout the capsule during pyrolysis. This diffusion significantly diminishes the capsule performance during implosion. Thermal and coated oxide barrier layers employed between layers mitigate the diffusion of copper during the mandrel removal process. The copper atoms do not diffuse through this barrier during pyrolysis. A capsule fabrication method that produces a capsule with a thin oxide layer will be discussed.

42 ENGINEERING↗

DOE OSTI2010

Fusion Application Targets

Complex target structures are necessary to take full advantage of the unique laboratory environment created by inertial confinement fusion experiments. For example, uses-ofignition targets that contain a thin layer of a low density nanoporous material inside a spherical ablator shell allow placing dopants in direct contact with the DT fuel. The ideal foam for this application is a low-density hydrocarbon foam that is strong enough to survive wetting with cryogenic hydrogen, and low enough in density (density less than ~30 mg/cc) to not reduce the yield of the target. Here, we discuss the fabrication foamlined uses-of-ignition targets, and the development of low-density foams that can be used for this application.

36 MATERIALS SCIENCE↗