The vaporization of a spherically symmetric liquid droplet homogeneously heated by a high-intensity laser pulse is investigated on the basis of a hydrodynamic description of the system composed of the vapor and ambient gas. In the limit of convective vaporization, the boundary conditions at the fluid-gas interface are formulated by using the notion of a Knudsen layer across which translational equilibrium is established. Numerical solutions to the hydrodynamic equations exhibit the existence of two shock waves propagating in opposite directions with respect to the contact discontinuity that separates the ambient gas and vapor. 17 refs., 6 figs.

We have successfully constructed and tested a pair of high-field coils that is part of the magnet set of the Mirror Fusion Test Facility (MFTF-B) at the Lawrence Livermore National Laboratory. Each coil consists of a multifilamentary Nb/sub 3/Sn magnet nested inside a multifilamentary NbTi magnet. During our test, these coils produced a central field of 12 T, with a peak conductor field of 12.5 T. The dimensions of the Nb/sub 3/Sn insert coil are: 1.34-m bore, 2.57-m outer diameter, and 1.14-m overall length. These coils were designed to be fully cryogenically stabilized and cooled by pool-boiling liquid helium. The operating current density of the Nb/sub 3/Sn coils is 2000 A/cm/sup 2/ and 2400 A/cm/sup 2/ for the NbTi magnet. In this paper, we present design considerations and details, construction techniques, and operational results of these coils.

An extended series of experiments has been used to investigate transition radiation in the x-ray spectral region. The x-rays were generated at the Lawrence Livermore National Laboratory electron-positron linear accelerator by 54 MeV electrons traversing multiple thin-foil targets. The measured angular and spectral distributions have shown excellent agreement with calculated predictions based on a simplified theoretical description of transition radiation. Recently, energy-resolved measurements of x-ray generation by targets consisting of multiple closely-spaced foils has clearly demonstrated the longitudinal coherence of transition radiation. This behavior might lead to a variety of applications such as tuneable narrow-band x-ray sources, measurement of x-ray dielectric constants, or particle beam diagnostics. These issues will be discussed, and recent results will be presented.