[en] Until now the thermodynamic and structural properties of hydrogen continue to be understood unsatisfactory. A number of complex high pressure phases at relatively low temperatures has been confirmed (1). However, conclusive answers on the existence of a plasma phase transition, the dissociation of hydrogen molecules at high densities, the metallization in the solid, and the melting line for pressures above 70GPa are still missing. A particularly interesting behavior has been predicted for the melting line at high pressures where it has a maximum and its slope changes sign (2). In Ref. (3), we have shown that these states can be created using cylindrical compression driven by heavy ion beams. Employing ab initio simulations (4) and experimental data, a new wide range equation of state for hydrogen was constructed (3). This new hydrogen EOS combined with hydrodynamic simulations is then used to describe the compression of hydrogen in LAPLAS targets (5) driven by heavy ion beams to be generated at the FAIR. The results shown in Fig. 1 indicate that the melting line up to its maximum as well as the transition from molecular fluids to fully ionized plasmas can be tested. By carefully tuning the number of particles in the beam, the compression can be adjusted to yield states at the solid-liquid phase transition (compare panels (a) and (b) in Fig. 1). This allows one to test the shape of the melting line beyond its maximum. It was demonstrated (3) that x-ray scattering (6) can be used to distinguish between the molecular solid and liquid phases as well as the metallic states. Hydrodynamic simulations have also highlighted the importance of temperature diagnostics, as it is more sensitive to the EOS than the density based diagnostic methods. Different materials have been considered as absorber. Although lead might seem to be the natural choice, the simulations show that aluminium is also a feasible option if slightly less compression is sufficient. Moreover, aluminium offers further options for testing by x-ray scattering and, thus, might be favorable compared to lead drivers. In summary, valuable information on the properties of high-density hydrogen can be obtained by dynamic compression with heavy ion beams. The long standing questions of the plasma phase transition, melting, and metallization can be addressed. The calculated Jupiter isentrope shown in Fig. 1 indicates that such experiments would be also highly beneficial for the giant planet modeling

[en] Full Text:Underwater wire electrical discharges (OWED) generated by pulsed high-current nanosecond and microsecond generators can be considered as sources of non-ideal plasma. In our experiments with UWED we used microsecond (T1/4 = 2ns, Imax=100kA, dI/dt = 5 x 10¹⁰A/s, W=3.3 kJ) and nanosecond (T_1/4 = 60ns, Imax = 80kA, df/dt = 2 x 10¹²A/s, W = 0.6 kJ) generators. The parameters of the generated SW were obtained using different pressure gauges and shadow photography with fast frame and streak cameras. The discharge channel plasma parameters were obtained by the analysis of the evolution of the discharge channel and pressure waves generated in water combined with equation of state of wire material. Also, time resolved spectroscopic data of the discharge plasma light emission was obtained for determination of the discharge plasma parameters. An attempt to receive total energy balance was made. Performances of nanosecond and microsecond UIWED are compared

[en] Full Text: Experimental and magneto-hydro-dynamic simulation results of micro- and nanosecond time scale underwater electrical Al, Cu and W wires explosions are presented. A capacitor bank with stored energy up to 6 kJ was used in microsecond time scale experiments and water forming line generator with current amplitude up to 100 k A and pulse duration of 100 ns were used in nanosecond time scale experiments. Extremely high energy deposition of up to 60 times the atomization enthalpy was registered in nanosecond time scale explosions. A discharge channel evolution and surface temperature were analyzed by streak shadow imaging and using fast photo-diode with a set of interference filters, respectively. Microsecond time scale electrical explosion of cylindrical wire array showed extremely high pressure of converging shock waves at the axis, up to 0.2 Mbar. A 1D and 2D magneto hydro- dynamic simulation demonstrated good agreement with such experimental parameters as discharge channel current, voltage, radius, and temperature

[en] Results and analysis of a microsecond time scale underwater electrical wire explosion are presented. Experiments were carried out with a Cu wire exploded by a current pulse ≤100 kA with microsecond time duration. The analysis is based on shadow and spectrally resolved streak photography which were used to monitor the evolution of the discharge channel and the shock wave. The obtained data were used for hydrodynamic calculation of the generated water flow parameters, such as pressure and flow velocity distribution between the discharge channel and the shock wave. In particular, the pressure at the discharge channel boundary and the energy transferred to the water were estimated. The results of the calculation have been verified by comparing the measured and calculated trajectories of the shock wave. Based on the results of the calculation the energy transferred to the water was estimated. In addition, the analysis shows that the energy initially deposited in the discharge channel continues to produce mechanical work after the deposition of the electrical energy has ended

[en] A numerical and self-similar analysis of the generation of implosion in water medium in cylindrical and spherical geometries is presented. The following interaction of the implosion wave with a deuterium-tritium mixture target is analyzed. It was found that the established converging cumulative water flow is self-similar, in spite of the complexity of the implied equations of state. Results of an idealized model indicate that, using a spherical geometry setup with 7.5 mm external radius of the water layer and ∼35 kJ total deposited energy, a ∼1.5x10¹⁴ neutron yield during ∼1.5 ns time can be achieved. The obtained results suggest that ignition of deuterium-tritium target by implosion in water medium can be considered as a promising method for inertial confinement fusion

[en] Full Text:Experimental and magneto-hydro-dynamic simulation results of nanosecond time scale underwater electrical Al, Cu and W wires explosions are presented. A water forming line generator with current amplitude up to 100 kA was used. Maximal current rise rate and maximal Joule heating power achieved during wire explosions were 500 Ga/s and 6 GW, respectively. Extremely high energy deposition of up to 60 times the atomization enthalpy was registered comparing to the best reported result of energy deposition obtained in vacuum wire explosion of 20 times the atomization enthalpy. A discharge channel evolution and surface temperature were analyzed by streak shadow imaging and using fast photo-diode with a set of interference filters, respectively. A 1D magneto-hydro-dynamic simulation demonstrated good agreement with such experimental parameters as discharge channel current, voltage, radius, and temperature. Material conductivity has been calculated to produce best correlation of the simulated and experimentally obtained voltage. It has been shown that conductivity may significantly vary as a function of energy deposition rate in nanosecond time scale underwater electrical wire explosions

[en] We re-investigate some classical approaches for collisional absorption of laser radiation in dense plasmas and compare them to quantum theories. The typical break-down of the classical approaches can be avoided by using the quantum dielectric function in the seminal Dawson and Oberman formula which is equivalent to recently published quantum theories of collisional absorption. Strong electron-ion scattering can however be included more easily in classical approaches

[en] A new one-dimensional hydrodynamic code for simulation of experiments involving the creation of high energy density in matter by means of laser or heavy ion beam irradiation is described. The code uses well-tested second order Lagrangian scheme in combination with the flux-limited van Leer convection algorithm for re-mapping to an arbitrary grid. Simple test cases with self-similar solutions are examined. Finally, the heating of solid targets by lasers and ions beams is investigated as examples.

[en] Analysis of time- and space-resolved spectrum of radiation emitted from the discharge channel generated by an underwater electrical wire explosion is reported. The purpose of this investigation was to detect a possible shunting corona discharge. During careful analysis of the emitted radiation no evidence for such discharge was found. Discharge temperature of 7 eV was estimated by quantitative analysis of the emitted spectra

[en] Complete text of publication follows. The talk will review the importance of energetic ions in different inertial confinement fusion scenarios: i) heavy ion beams are very efficient drivers that can deliver the energy for compression in indirect as well as direct drive approaches; ii) the interaction of α-particles, that are created in a burning plasma, with the surrounding cold plasma is essential for creating a burn wave; iii) laser-produced ion beams are also a strong candidate to create the hot spot needed for fast ignition. In all applications the ions interact with dense matter that is characterized by strongly coupled ions and (possibly) partially degenerate electrons. Moreover, the coupling between beam ions and target electrons can be strong as well. Under these conditions, standard approaches for the beam-plasma interactions process are known to fail. The presentation will demonstrate how advanced models for the energy loss of ions in dense plasmas can resolve the issues mentioned above. These models are largely built on quantum kinetic theory that is able to describe degeneracy and strong coupling in a systematic way. In particular, strong interactions require a quantum description for electron-ion collisions in dense plasma environments, which is done by direct solutions of the Schroedinger equation. Degeneracy and collective excitations can be included via the Lenard-Balescu description where strong interactions may be included via a pseudo-potential approach. Finally, results are shown for all three fusion applications described above. The effects related to strong coupling and degeneracy mainly concern the end of the stopping range where the beam ion dose not have enough energy to excite all possible degrees of freedom and, thus, certain processes are frozen out. However, we also find a significant reduction of the range for swift heavy ions in the GeV-range when stopping in dense matter is considered. The stopping range of α-particles in the highly compressed matter around the burning fusion core is however strongly increased due to degeneracy of the target electrons. This result implies the need for much larger hot spots than predicted by standard models. Similarly, the range of light ions considered for fast ignition is increased. This makes success of this efficient ICF approach harder to achieve, but already reflects the need for larger hot spots due to the larger spread of the α-particles heating. Acknowledgements: This work is funded by the Engineering and Physical Sciences Research Council of the UK.