Isothermal, mass-limited rarefactions in planar and spherical geometry

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98660/1/PhysPlasmas_18_104506.pd

The design of laboratory experiments to produce collisionless shocks of cosmic relevance

Naturally occurring shocks transport energy and accelerate particles throughout the cosmos. The problem of producing collisionless shocks in the laboratory that are of relevance to such cosmic shocks is considered. Such an experiment must meet a number of constraints, several of which can be expressed by algebraic scaling relations. The relations for magnetization, plasma beta, Alfvén Mach number, temperature, magnetic field, and collisionality are described here. Taken together, the limits imposed by these constraints upon possible experiments are specified. The growth of magnetohydrodynamic (MHD) turbulence and the degree of particle acceleration are examined, demonstrating that it is feasible to contemplate studies of such phenomena in the laboratory. Finally, some discussion of how an experiment might meet the other qualitative constraints, and of how a laser might be used to drive the shock, is also included. © 2000 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70054/2/PHPAEN-7-11-4690-1.pd

Ion plasma waves induced by frustrated Debye shielding

The oscillation of electrons, in a sufficiently intense pump wave, frustrates Debye shielding in the direction of the oscillation. One finds that such oscillating electrons cannot shield charge fluctuations over distances smaller than the distance they sample in a plasma period. One consequence is that the frequency of ion waves can be increased from the ion acoustic frequency to the ion plasma frequency in the presence of large enough oscillations. This may explain a number of observations in laser experiments. More generally, any phenomenon involving Debye shielding will be altered by an intense pump wave. © 2002 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69595/2/PHPAEN-9-1-267-1.pd

Hydrodynamic instabilities in astrophysics and in laboratory high-energy–density systems

High-energy–density systems and astrophysical systems both involve hydrodynamic effects, including sources of pressure, shock waves, rarefactions and plasma flows. In the evolution of such systems, hydrodynamic instabilities naturally evolve. As a result, a fundamental understanding of hydrodynamic instabilities is necessary to understand their behaviour. This paper discusses the validity of a hydrodynamic description in both cases, and, from the common perspective of the basic mechanisms at work, discusses the instabilities that appear in astrophysics and at high energy density. The high-energy–density research facilities of today, built to pursue inertial fusion, can accelerate small but macroscopic amounts of material to velocities above 100 km s−1, can heat such material to temperatures above 100 eV and can produce pressures far above a million atmospheres (1012 dyn cm−2 or 0.1 TPa). In addition to enabling inertial fusion research, this enables these facilities to do experiments under the conditions that address basic physics issues including issues from astrophysics. One can devise experiments aimed directly at important processes such as the Rayleigh Taylor instability at an ablating surface or at an embedded interface that is accelerating, the Richtmeyer Meshkov evolution of shocked interfaces and the Kelvin–Helmholtz instability of shear flows. The paper includes examples of such phenomena from the laboratory and from astrophysics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/49111/2/ppcf5_12B_S30.pd

Imaging X-ray crystal spectrometer for laser-produced plasmas

X-ray Thomson scattering (XRTS) is a powerful technique for measuring state variables in dense plasmas. In this paper, we report on the development of a one-dimensional imaging spectrometer for use in characterizing spatially nonuniform, dense plasmas using XRTS. Diffraction of scattered x-rays from a toroidally curved crystal images along a one-dimensional spatial profile while simultaneously spectrally resolving along the other. An imaging spectrometer was fielded at the Trident laser at Los Alamos National Laboratory, yielding a FWHM spatial resolution of 3 mm. A geometrical analysis is performed yielding a simple analytical expression for the throughput of the imaging spectrometer scheme. The SHADOW code is used to perform a ray tracing analysis on the spectrometer fielded at the Trident Laser Facility understand the alignment tolerances on the spatial and spectral resolutions. The analytical expression for the throughput was found to agree well with the results from the ray tracing.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90829/1/1748-0221_6_04_P04004.pd

Magnetohydrodynamic scaling: From astrophysics to the laboratory

During the last few years, considerable progress has been made in simulating astrophysical phenomena in laboratory experiments with high-power lasers. Astrophysical phenomena that have drawn particular interest include supernovae explosions; young supernova remnants; galactic jets; the formation of fine structures in late supernovae remnants by instabilities; and the ablation-driven evolution of molecular clouds. A question may arise as to what extent the laser experiments, which deal with targets of a spatial scale of ∼100 μm and occur at a time scale of a few nanoseconds, can reproduce phenomena occurring at spatial scales of a million or more kilometers and time scales from hours to many years. Quite remarkably, in a number of cases there exists a broad hydrodynamic similarity (sometimes called the “Euler similarity”) that allows a direct scaling of laboratory results to astrophysical phenomena. A discussion is presented of the details of the Euler similarity related to the presence of shocks and to a special case of a strong drive. Constraints stemming from the possible development of small-scale turbulence are analyzed. The case of a gas with a spatially varying polytropic index is discussed. A possibility of scaled simulations of ablation front dynamics is one more topic covered in this paper. It is shown that, with some additional constraints, a simple similarity exists. © 2001 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71174/2/PHPAEN-8-5-1804-1.pd

Mini-conference and related sessions on laboratory plasma astrophysics

This paper provides a summary of some major physics issues and future perspectives discussed in the Mini-Conference on Laboratory Plasma Astrophysics. This mini-conference, sponsored by the Topical Group on Plasma Astrophysics, was held as part of the American Physical Society’s Division of Plasma Physics 2003 Annual Meeting (October 27–31, 2003). Also included are brief summaries of selected talks on the same topic presented at two invited paper sessions (including a tutorial) and two contributed focus oral sessions, which were organized in coordination with the mini-conference by the same organizers. © 2004 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70409/2/PHPAEN-11-5-2976-1.pd