The X-ray image of a compressed shell (enhanced by high-Z doping) was used in recent experiments to diagnose the effect of shell-fuel mixing. The emission ring (due to the limb effect) moves toward smaller radii due to mixing. We show here that using backlighting imaging can greatly enhance future imaging experiments. In addition to the emission ring, a backlighting absorption ring can appear around it. The absorption ring is virtually unaffected by mixing. Thus, the relative position of the two rings constitutes a mixing signature. In other words, the absorption ring delineates the colder part of the shell and is a true signature of the compression, whereas the emission ring reflects the shell material motion due to mixing.

The main objective of the experimental plasma physics activities at the Gesellschaft für Schwerionenforschung (GSI) is the interaction processes of heavy ions with dense ionized matter. Gas discharge plasma targets were used for energy loss and charge state measurements in a regime of electron density and temperature up to 1019 cm-3 and 20 eV, respectively. Progress has been achieved in the understanding of charge-exchange processes in fully ionized hydrogen plasma. An improved model taking excitation-autoionization processes into account has removed most of the discrepancies of previous theoretical descriptions. Furthermore, it was found that the energy loss of the ion beam serves as an excellent diagnostic tool for measuring the electron density in partially ionized plasmas such as argon. The experience with these methods will be used in the future to diagnose dense laser produced plasmas. A setup with a 100 J/5 GW Nd:glass laser, currently under construction, will provide access to density range up to 1021 cm-3 and temperatures of more than 100 eV. To reach electron densities near solid-state density (1023 cm-3), heavy ion heated frozen rare gas crystals were used. The first hydrodynamic motion of ion heated solid material was observed. Vacuum-ultraviolet (VUV) spectroscopy was applied to diagnose these strongly coupled nonideal plasmas.

The aluminium side of two-layer Al-Plastic targets were irradiated with a long pulse (∼ 2.4 ns FWHM) 1.06-μm laser light at intensities up to 7 × 1013 W/cm2. The time history of the thermal emission of the confined rear surface of the aluminum was measured. Visible emission only occurs for a short time after the arrival of the laser-generated shock waves. Over the range of the measurements, the duration and the intensity of the emission reduce with increasing laser intensity. The experimental results are in good agreement with the results of a simple phenomenological model that assumes a linear temperature and density profile on the shock front. The values of shock velocity and maximum temperature and density that were used in the model were found using the hydrodynamic simulation code MEDUSA. From the model the shock width was measured for different conditions by matching the emission of the experiment and model. It is found that the time history of the emission is strongly sensitive to the ionization potential of the plastic that is assumed to change with density from ∼ 4 eV at zero pressure to zero at high densities. The technique provides a way to measure the pressure metallization of large band gap insulators.

The problem of matching an ion beam delivered by a high-intensity ion source with an accelerator is considered. The experimental results of highly charged ion beam transport with space-charge compensation by electrons are presented. A tungsten thermionic cathode is used as a source of electrons for beam compensation. An increase of ion beam current density by a factor of 25 is obtained as a result of space-charge compensation at a distance of 3 m from the extraction system. The process of ion beam space-charge compensation, requirements for a source of electrons, and the influence of recombination losses in a spacecharge-compensated ion beam are discussed.

Parametric electron-ion potential for fast estimation of atomic data required for “on-line” calculations in inertial confinement fusion (ICF) driven by heavy ions is presented. Comparisons of our results (outer- and inner-shell ionization energies, oscillator strengths, and logarithmic mean excitation energies) with experimental and self-consistent-field (SCF) calculation values are made. Using the wave functions generated by the previously mentioned potential, generalized oscillator strengths and integrated inelastic collision cross sections are computed within the frame of Born approximation.

We discuss two different approaches for observing induced gamma-ray emission of nuclei, departing from known attempts to use the Moessbauer transitions that have so far proven unsuccessful. Both approaches (presented at the 11th and 12th International Conferences on Laser Interaction and Related Plasma Phenomena) are based on the elimination of pernicious influence of Doppler line-broadening in ensembles of free nuclei, particularly in atom and ion beams.

Results are presented of experiments on ion production from Ta targets using a short pulse (350–600 ps in focus) illumination with focal power densities exceeding 1014 Wcm-2 at the wavelength of an iodine photodissociation laser (1.315 μm) and its harmonics. Strong evidence of the existence of tantalum ions with the charge state +45 near the target surface was obtained by X-ray spectroscopy methods. The particle diagnostics point to the existence of frozen high charge states (<53+) of Ta ions in the far expansion zone at about 2 m from the target. The measured charge state-ion energy distribution indicates the highest energy (>4 MeV) for the highest observed charge states. A tentative theoretical explanation of the observed anomalous charge state freezing phenomenon in the expanding plasma produced by a subnanosecond laser pulse is given.

The experimental progress of laser equation of state (EOS) studies at Shanghai Institute of Laser Plasma (SILP) is discussed in this paper. With a unique focal system, the uniformity of the laser illumination on the target surface is improved and a laser-driven shock wave with good spatial planarity is obtained. With an inclined aluminum target plane, the stability of shock waves are studied, and the corresponding thickness range of the target of laser-driven shock waves propagating steadily are given. The shock adiabats of Cu, Fe, SiO2 are experimentally measured. The pressure in the material is heightened remarkably with the flyer increasing pressure, and the effect of the increasing pressure is observed. Also, the high-pressure shock wave is produced and recorded in the experimentation of indirect laser-driven shock waves with the hohlraum target.

The results of lead ion generation with charge state from Pb10+ to Pb35+ from laser-heated plasma are presented. CO2 lasers producing 10.6-μm wavelength radiation at power densities in the range 4.1011-6.1014 W/cm2 in TBKI and CERN were used. Results of detailed numerical simulations presented in the paper are in good agreement with the experimental data. Work done in collaboration with CERN, ITEP, and TBKI was aimed at the specification of requirements for a laser system that will be able to drive an ion source for the hadron collider (LHC) at CERN.

To determine the peak pressure induced versus the incident intensity of a neodymium (Nd) glass pulsed laser, with a duration of 25 ns in glass confined geometry, two methods have been comparatively used. Free surface velocity measurements have been performed using an electromagnetic gauge. The results are compared with pressure measurements realized at the back of irradiated aluminum targets with the use of polyvinylidene fluoride (PVDF) gauges. Both diagnostics provide consistent results. The measurements of peak pressure as a function of laser irradiance are used to determine the calibration curve (current density versus loading pressure) for new VF2/VF3 copolymer shock gauges used in this lasermatter interaction configuration. These experimental set-up deliver time resolved measurements that are interpreted by the shock-propagation phenomena.

In this paper we determine the inelastic contribution to the energy losses by swift heavy ions in dense matter. At equilibrium, the charge transfer stopping is determined by a simple energy balance and the excitation stopping is determined by the photons emission. Using an average atom model, we determine the density influence on these inelastic stoppings.

Broad-band random-phase (BRP) irradiation is one of the beam smoothing techniques for KrF laser drivers. We have introduced this technique into the KrF laser system ASHURA. By one-dimensional (ID) BRP smoothing, the speckle pattern in conventional random-phase irradiation has been removed. Two BRP beams were overlap-focused on the target incoherently. Although the obtained profile is rather smooth, some low-frequency nonuniformity remains. To improve the uniformity, a new technique for two-dimensional (2D) smoothing has been proposed. In this technique, a wedged etalon is used to get angular dispersion to the orthogonal direction to the ID BRP effect. The preliminary experiment has been carried out.

Experiments are presented that demonstrate the high stopping power of fully ionized hydrogen plasma for low-energy heavy ions. A plasma with electron densities up to 7.1016 cm–3 at temperatures above 1 eV was created by an electrical discharge. In the described experiment, a stopping power of 1.08 GeV/(mg/cm2) was measured using singly charged krypton ions at 45–keV/u energy. The measured stopping power exceeds the corresponding value in cold hydrogen gas by a factor of 35. These measurements confirm the theoretical stopping power predictions close to the expected maximum in a fully ionized plasma.

The simple physical model of highly charged ion generation in plasma produced by laser irradiation with long pulse duration (>1 ns) and moderate intensities (<1015/λ2 W/cm2μm2) is presented. In the frame of a single theory, most of the experimental results on plasma diagnostics are described in total. It is shown that plasma temperatures, ion charge states, and ion velocities as well as angular distributions of highly charged ions can be explained with good accuracy by collisional absorption of laser energy, hydrodynamic acceleration of forming plasma, and three-body recombination through highly exited levels during plasma expansion into vacuum. The general scalings for plasma parameters are derived on the basis of the model proposed.

At the Karlsruhe Light Ion Facility (KALIF) high-power proton beams with power densities up to ∼ 1 TW/cm2 are generated depositing up to 40 kJ of ion energy in a focal spot of 6∼8-mm diameter. With peak proton energies of ∼ 1.7 MeV, specific power densities of up to 200 TW/g and energy densities of several MJ/g can be realized. This is a regime in which experiments providing information on the equation of state (EOS), dynamics of the beam interaction with condensed targets, and properties of solids and plasma at high-energy densities are of particular interest. In the present paper we report on shock-wave experiments using solid targets and high-resolution laser-Doppler velocimetry. The empirical data provided are used to verify code simulations and the used EOS-data in these calculations, to investigate the beam-target interaction, and to perform series of shock-wave measurements of properties of different materials. The ∼40-ns FWHM proton beam can be used to generate, by material ablation or impact of ablatively accelerated flyers, intense shock waves, permitting the investigation of shock compressibility, dynamic failure of solids under nanosecond load duration, phase transitions, and viscosity at strain rates up to ∼108 s-1. Recently an improved line-imaging velocimeter was set up to measure the spatial velocity variation with a maximum resolution of < 10 μm, opening the possibility to address new issues like growth of instabilities or local dynamics of the spall fracture.

Classical molecular dynamics of the ions and quantum treatment of the electrons are combined in the study of the properties of hot, dense plasmas. An effective ionic interaction potential is used in the molecular dynamics simulations. The electronic density of states is calculated using the equation of motion method. Special attention is given to the broadening of resonances in the electronic density of states, which may have important effects on the thermodynamic properties of the plasma.

Demonstration of matching a laser ion source to the GSI RFQ-Maxilac linear accelerator and the acceleration of a 1.8-mA current beam of Ta10+ ions up to 45 keV/u energy is presented. A 10J/μs CO2 laser has been used to produce a hot plasma plume, emitting highly charged tantulum ions. The correct geometry and potential distribution of the matching section has been designed in accordance with the results of computer simulations by using the AXCEL code. Measurements of the charge state distribution of the accelerated beam indicate that it contains about 70% Ta10+ and 30% Ta11+ ions.

Experimental results are presented on shock-wave generation in solid samples, irradiated directly by optically smoothed laser beams. Random phase plates and phased zone plates have been successfully used. In particular, the last technique allowed the production of uniform shock fronts that have been used for equation of state experiments at pressures above 10 Mbar. Pressures higher than 35 Mbar were achieved in gold, by using laser pulses with energy E ≈ 100 J, and structured, two-step, two-material targets.