We describe the evolution of the large-scale coherent structure of bubbles and spikes in the Richtmyer–Meshkov instability. Our multiple harmonic analysis accounts for a non-local character of the nonlinear dynamics. A new type of the evolution of the bubble front is found. A comparison to so-called “Layzer-type” local models is performed.

The results on study of light sources based on spontaneous radiation of molecules KrCl* (λ ∼ 222 nm) and XeCl* (λ ∼ 308 nm) excited by a glow discharge are presented. It is demonstrated that additions of light inert gases (He and Ne) lead to increase in emission of radiation power and efficiency in mixtures Kr(Xe)-Cl2. A high-power cylindrical multi-section excilamp was built and energy, time, and spectrum characteristics have been studied. Average output power obtained in the UV spectral range were 1,9 kW at λ ∼ 222 nm and 1,1 kW at λ ∼ 308 nm with efficiencies with respect to the excitation power of up to 14%.

Numerical analysis of the compression of a cylindrical cryogenic hydrogen sample surrounded by a high-density metallic shell driven by a heavy ion beam has been performed. The beam power profile is assumed to be parabolic in time and Gaussian in space and is made of uranium ions with a kinetic energy of 2.7 GeV/u. The beam center is positioned off axis and rotates around the target axis to provide a uniform annular energy deposition area. An acceptable symmetry in pressure is achieved if the number of revolutions is equal to or larger than 10. The maximum density and pressure of the hydrogen sample is studied as a function of the spread of the beam power Gaussian distribution and the rotation radius. This configuration leads to compressions of the order of 10 and a temperature of a few thousand Kelvin in hydrogen.

A commercial mode locked cavity dumped Nd:YAG dye laser operating at 10 Hz repetition rate is modified to produce a high contrast (>5000:1) single laser pulse while maintaining the energy stability and high beam quality. A trigger generator biases the cavity dumping photodiode, which is triggered externally by a pulse from the microprocessor-based control unit controlling a ∼2 J/200 ps laser chain. In the laser chain, the high contrast (>5000:1) is achieved by an external pulse selector based on single Pockel's cell to select a single laser pulse of high contrast, which is a prerequisite for experimental study of the equation of state. Laser-induced shock velocity measurement in thin aluminum, gold on aluminum, and copper on aluminum foil targets using this modified laser system are also presented. The equation of state of Al, Au, and Cu obtained using an impedance matching technique are in agreement with the reported results of SESAME and simulation results.

Acceleration-driven fluid mixing is studied here from a theoretical point of view. Considerable progress has been achieved in the understanding of mix. Theories of the authors are reviewed that allow prediction of the edge of the mixing zone, in agreement with experimental data. Theories that describe the distribution of masses within the mixing region are also reviewed. The theory we present describes a chunk mix regime, in which two phases are mixed at a chunk level, but for which there is no atomic mixing. Thus the two phases are segregated into disjoint regions of space.

The actual situation with respect to the use of an RF linac driver for heavy ion inertial fusion (HIF) is discussed. At present, there is no high current heavy ion linac under construction. However, in the course of linac projects for e−, p, d, or highly charged ions several developments were made, which may have some impact on the design of a HIF driver. Medium- and low-β superconducting structures suited for pulsed high current beam operation are actually designed and investigated at several laboratories. A superconducting 40 MeV, 125 mA cw linac for deuteron acceleration is designed for the Inertial Fusion Material Irradiation Facility (IFMIF). The Institute for Applied Physics (IAP) is developing a superconducting 350-MHz, 19-cell prototype CH-cavity for β = 0.1. The prototype cavity will be ready for tests in 2004. A superconducting main HIF driver linac would considerably reduce the power losses. Moreover, it would allow for an efficient linac operation at a higher duty factor.

The 1.4-AMeV room-temperature High Current Injector HSI at Gesellschaft für Schwerionenforschung (GSI) has been in routine operation for more than 2 years now. With a mass-to-charge ratio of up to 65, a current limit of 15 mA for U4+, and an energy range from 2.2 AkeV up to 1.4 AMeV, this linac is suited to gain useful experience on the way toward the design of a HIF RF driver. The status and technical improvements of that A/q ≤ 65, 91-MV linac are reported. Beam dynamics calculations for Bi1+-beams show that powerful focusing elements at the linac front end are the bottleneck with respect to a further increase in beam current. Besides superconducting and pulsed wire quadrupoles, the potential of the Gabor-plasma lenses is investigated.

We present a Rayleigh–Taylor mixing rate simulation with an acceleration rate falling within the range of experiments. The simulation uses front tracking to prevent interfacial mass diffusion. We present evidence to support the assertion that the lower acceleration rate found in untracked simulations is caused, at least to a large extent, by a reduced buoyancy force due to numerical interfacial mass diffusion. Quantitative evidence includes results from a time-dependent Atwood number analysis of the diffusive simulation, which yields a renormalized mixing rate coefficient for the diffusive simulation in agreement with experiment. We also present the study of Richtmyer–Meshkov mixing in cylindrical geometry using the front tracking method and compare it with the experimental results.

We present a numerical study to late times of a Richtmyer–Meshkov environment: a weak shock (M = 1.095) interacting with a heavy cylindrical bubble. The bubble interface is modeled as a diffuse interfacial transition layer (ITL) with finite thickness. Our simulation with the piecewise parabolic method (PPM) yields very good agreement in large- and intermediate-scale features with Jacobs' experiment (Jacobs, 1993). We note the primary circulation enhancement deposited baroclinically upon the incident shock wave, and significant secondary baroclinic circulation enhancement, first observed in Zabusky and Zhang (2002). We propose that this vortex-accelerated circulation deposition is universal. These baroclinic processes are mediated by a strong gradient intensification and stretching of the ITL and result in close-lying vortex bilayers (VBLs) and the emergence of vortex projectiles (VPs). These account for the elongated, kidney-shaped morphology of the rolled up bubble domain at late times.

An ion source for generation of low-charged heavy ions has been developed using low-power KrF excimer and frequency-doubled Nd:YAG lasers. The ion source was examined with two experimental modes of low-voltage DC extraction at ∼20 kV and high-voltage pulse extraction at 150 kV. Normalized emittance of extracted beams composed of Cu+ and Cu2+ ions was measured to be about 0.05 and 0.8 πmm-mrad for the DC extraction and the pulse extraction, respectively. Electron temperature was observed by means of a single probe method to be 0.8 to 2.5 eV, depending on the intensity of the KrF laser.

We suggest an easily obtained laboratory configuration to observe jet and vortex flows for the Richtmyer–Meshkov (accelerated inhomogeneous flow) environment. A hemispherical bubble in air with density ratio of 5 is placed against an ideally reflecting wall and struck by a planar shock. This also models a spherical bubble struck symmetrically by two identical approaching shocks, that is, a “reshock” configuration. For all Mach numbers (M = 1.2, 1.5, and 2.0), our axisymmetric simulations show that the heavy hemispherical bubble expands axially away from the wall as a jet, and a weaker vortex ring moves radially along the wall. In addition, when M = 1.5, a ringlike vortex projectile (VP) of small diameter follows closely behind the reflected shock and is associated with its moving triple point. This VP contains an entrained shocklet and quadrupole structure of dilatation. Various methods are applied to quantify the emerging coherent structures.

We have performed simulations of the evolution of the turbulent Rayleigh–Taylor instability with an arbitrary Lagrange–Eulerian code. The problem specification was defined by Dimonte et al. (2003) for the “alpha group” code intercomparison project. Perfect γ = 5/3 gases of densities 1 and 3 g/cm3 are accelerated by constant gravity. The nominal problem uses a 2562 × 512 mesh with initial random multiwavelength interface perturbations. We have also run three-dimensional problems with smaller meshes and two-dimensional (2D) problems of several mesh sizes. Under-resolution lowered linear growth rates of the seed modes to 5-60% of the analytic values, depending on wavelength and orientation to the mesh. However, the mix extent in the 2D simulations changed little with grid refinement. Simulations without interface reconstruction gave penetration only slightly reduced from the case with interface reconstruction. Energy dissipation differs little between the two cases. The slope of the penetration distance versus time squared, corresponding to the α parameter in h = αAgt2, decreases with increasing time in these simulations. The slope, α, is consistent with the linear electric motor data of Dimonte and Schneider (2000), but the growth is delayed in time.

We continue our previous investigations (Yang, Zabusky, & Chern, 1990; Zabusky & Zhang, 2002) of the interaction of a shock with a planar, inclined curtain (slow/fast/slow) to a wider Mach number range (M = 1.5, 2.0, and 5.0) and longer times. In all cases, the generic features may be explained in terms of the opposite-signed vortex layers (deposited by the shock wave), which approach and collide to form a complex vortex bilayer (VBL). At M ≤ 2.0, the VBL traverses the shock tube and eventually collides with the opposite horizontal boundary and evolves into upstream and downstream moving inhomogeneous vortex projectiles (VPs) (Zabusky & Zeng, 1998). This is manifested as early-time “breakthrough” (Yang, Zabusky, & Chern, 1990). During the traversal, we observe and scale a strong secondary baroclinic circulation enhancement. We track and quantify the VPs and show that their velocities compare well to that from a simple vortex model. We also display turbulent domains and a new rapid early time turbulization at M = 5, when the VBL is narrower.

We examine the interaction of both cylindrical and spherical bubbles (2D) and a complex blast wave, which consists of an approaching shock/contact discontinuity/shock (Kang et al., 2001a, 2001b). Such configurations may arise following a supernova explosion, for example, SN 1987A, where a complex blast wave is presently approaching a high density “circumstellar ring” (CR) (Borkowski et al., 1997). Using simulations with the piecewise parabolic method algorithm (Colella & Woodward, 1984), we emphasize the appearance of vortex bilayers, vortex projectiles, and turbulent domains on the downstream and upstream sides of the bubble. We believe that the interfacial deformation of the CR is associated with a strong blast-wave driven accelerated inhomogeneous flow instability in a high density medium and thus will have a different character than the more common planar shock-driven Richtmyer–Meshkov instability.