We have studied the potential of hard X-ray radiography as a diagnostic in high energy density experiments, proposed for the future Facility for Antiproton and Ion Research (FAIR). We present synthetic radiographic images generated from hydrodynamic simulations of the target evolution. The results suggest that high-resolution density measurements can be obtained from powerful hard X-ray sources driven by a PW-class high-energy laser system. Test measurements of a prototype hard X-ray imaging detector for photon energies above 100 keV are presented.

An approach to an alternative laser fusion in a magnetic field with an intense laser of exa watt level will be discussed. Such a strong field in an exa watt laser will induce enhanced nuclear tunneling through the propagation in plasma. This causes an enhanced nuclear reaction for fusion. We discuss the possibilities to apply this to nuclear fusion energy and to obtain break even in a 100 kJ laser.

Stochastic instabilities are studied considering the motion of one particle in a very high intensity wave perturbed by one or two low intensity traveling waves. Resonances are identified and conditions for resonance overlap are studied. PIC code simulation results confirm the stochastic heating.This paper was presented at the 28th ECLIM conference in Rome, Italy.

The effects of axial magnetic field on the properties of the ions ejected from Nd:YAG laser (wavelength = 1064 nm, pulse duration = 6 ns) produced expanding Cu plasma were investigated. A plane Cu target, without and with 0.23 T axial magnetic field at its surface, was irradiated in the fluence range of 2–24 J/cm2. The ions emitted along the target surface normal were analyzed with the help of ion collector and time-of-flight electrostatic ion energy analyzer. The integrated ion yield, highest ion charge state, average ion energy, and energy of individual ion charge states were found to increase by application of the magnetic field. The initial parameters of the non-equilibrium plasma such as average ion charge, equivalent potential, electron temperature, electron density, Debye length, and transient electric field were estimated from the experimental results obtained without and with application of the magnetic field. The increase of ion yield and ion charge state by application of magnetic field are most probably due to the trapping of electrons in front of the target surface, which boosts up the electron impact ionization process. The ion energy increment due to the magnetic field is discussed in the frame work of electrostatic model for ion acceleration in laser plasma.

This paper presents an investigation on the self-focusing of a cosh-Gaussian laser beam in the thermal quantum plasma (TQP) by taking into account the effects of relativistic nonlinearity. An appropriate nonlinear Schrödinger equation has been solved analytically by applying the variational approach. The self-focusing and the self-phase modulation are examined under a variety of parameters. The self-trapping of a cosh-Gaussian laser beam is further studied at various values of the decentered parameter, b with different absorption levels, ${k}^{\prime}_i$. Numerical analysis shows that these parameters play a vital role in propagation characteristics. The significant contribution of the quantum effects to enhance the self-focusing and minimize the longitudinal phase has been observed. Further, a comparison has been made with the classical relativistic (CR), the relativistic cold quantum (RCQ), and the thermal quantum (TQ) regimes. The self-focusing is found to occur earlier and is strongest for the case of TQP in the present analysis.

The assembly of the Paul Trap Simulator Experiment (PTSX) is now complete and experimental operations have begun. The purpose of PTSX, a compact laboratory facility, is to simulate the nonlinear dynamics of intense charged particle beam propagation over a large distance through an alternating-gradient transport system. The simulation is possible because the quadrupole electric fields of the cylindrical Paul trap exert radial forces on the charged particles that are analogous to the radial forces that a periodic focusing quadrupole magnetic field exert on the beam particles in the beam frame. By controlling the waveform applied to the walls of the trap, PTSX will explore physics issues such as beam mismatch, envelope instabilities, halo particle production, compression techniques, collective wave excitations, and beam profile effects.

A new version of the numerical code KALOS has been developed to solve the Vlasov-Fokker-Planck equation for electrons as well as EM wave propagation. KALOS represents the electron distribution function in momentum space by an expansion in spherical harmonics. Its unique features make possible simultaneous investigations of fast electron generation and transport and the collisional evolution of thermal particles, including the return current of cold electrons. We report here on results obtained in one spatial dimension. Absorption of 100fs, 1015 W/cm2 laser pulses has been studied at normal incidence in sharp-edged dense plasmas. We have studied the effect on absorption of energy transport into the target as well as the deviation of the electron distribution function from Maxwellian. It is shown that it is necessary to take into account collisional heat transport into the target in order to correctly model the absorption rate at the front surface.

This paper presents an investigation into the behavior of a laser beam of finite diameter in plasma with respect to forces and optical properties, which lead to self-focusing of the beam. The transient setting of ponderomotive nonlinearity in a collisionless plasma has been studied, and consequently the self-focusing of the pulse, and the focusing of the plasma wave occurs. The description of a self-focusing mechanism of laser radiation in the plasma due to nonlinear forces acting on the plasma in the lateral direction, relative to the laser has been investigated in the nonrelativistic regime. The behavior of the laser beams in plasma, which is the domain of self-focusing at high or moderate intensity, is dominated by the nonlinear force. The investigation of self-focusing processes of laser beams in plasma results from the relativistic mass and energy dependency of the refractive index at high laser intensities. Here, the relativistic effects are considered to evaluate the relativistic self-focusing lengths for the Nd glass radiation, at different plasma densities of various laser intensities. A numerical program in c++ that incorporates both the ponderomotive force in self-focusing mechanism and relativistic effects has been developed to explore in depth self-focusing over a wide range of parameters.

We have studied a suite of cylindrical, polystyrene targets, both unperturbed and with mode-28, 1.5 μm initial-amplitude sinusoidal perturbations imposed azimuthally along the target length. All targets are driven by direct laser illumination at 3ω using the University of Rochester OMEGA laser facility. Our numerical simulation and experimental data demonstrate the proof of principle for direct-drive studies of complex hydrodynamic phenomena in convergent geometry. We obtain high-quality, time-dependent data, that demonstrate good implosion symmetry and against which numerical simulations show promising agreement within currently assessed error bars. Our results identify operational space for continuing experiments.

The aim of the reported research is to contribute to investigation of new processes and methods interlinking nuclear and laser-plasma physics. With respect to requirements of nuclear experiments at medium-size high-power lasers, the selection of proper candidates for studying the excitation and decay of low-lying nuclear states is reviewed. An experimental approach to the identification of low-energy nuclear transitions is discussed, simple estimates of the 181Ta excitation yield in the laser-generated plasma provide a theoretical basis for planning future work. First tests and results of the experiments at the laser facility PALS are presented.

Cosmic plasma physics and our concept of the universe is in a state of rapid revision. This change started with in-situ measurements of plasmas in Earth's ionosphere, cometary atmospheres, and planetary magnetospheres; the transition of knowledge from laboratory experiments to astrophysical phenomena; discoveries of helical and filamentary plasma structures in the Galaxy and double radio sources; and the particle simulation of plasmas not accessible to in-situ measurement. Because of these, Birkeland (field-aligned) currents, double layers, and magnetic-field aligned electric fields are now known to be far more important to the evolution of space plasma, including the acceleration of charged particles to high energies, than previously thought. This paper reviews the observational evidence for a plasma universe threaded by Birkeland currents and particle beams.

Key issues of heavy ion beam (HIB) inertial confinement fusion (ICF) include an efficient stable beam transport, beam focusing, uniform fuel pellet implosion, and so on. To realize a HIB fine focus on a fuel pellet, space-charge neutralization of incident focusing HIB is required at the HIB final transport just after a final focusing element in an HIB accelerator. In this article, an insulator annular tube guide is proposed at the final transport part, through which a HIB is transported. The physical mechanism of HIB charge neutralization based on an insulator annular guide is as follows: A local electric field created by HIB induces local discharges, and plasma is produced on the insulator inner surface. Then electrons are extracted from the plasma by the HIB net space charge. The electrons emitted neutralize the HIB space charge well.

Radiation transfer in low-density foam is influenced by the external radiation field which impacts on the foam when the size of plasma created in laboratory is not large to be opatical thick. The radiation transfers of different photon groups are sensitive probes of the conditions of the medium through which they propagate. The temporal behavior of photon groups to which the plasma is optical thin is quite different from that of photon groups to which the plasma is optical thick. The breakout times of different photon groups through the foam are distinguishable different in experiment when we measures them at the end of foam. The multi-group supersonic radiation transfer behavior in low-density foam is studied both by multi-group transfer numerical simulation and experiments. Two characteristic photon groups are chosen to do experimental research on the multi-group transfer behavior in low-density CH foam. A time-resolved chromatic streaked X-ray spectrometer measure the breakout of the two photon group from the far end of the foam cylinder. The distinguishable transfer time delay between two groups is observed.

Experiments have been performed to investigate charge state and energy loss of 5.9-MeV/u uranium ions in a partially ionized dense argon plasma with 1017 ≤ ne ≤ 1019 cm−3 and 1 ≤ Te ≤ 10 eV. The charge state of the ions was found to be equal to the equilibrium charge state in cold gas. The energy loss offered a useful tool for plasma density diagnostics. Spectroscopic measurements using the electron collision broadening of ArII- and ArIII-lines in the visible and UV spectral region confirm this plasma density data.

The system of differential equations for the non-ablated mass, the average implosion velocity, and the ablation radius of an indirectly driven capsule in acceleration phase, has been obtained from conservation principles of hydrodynamics. Two phases are distinguished during acceleration, according to the uniformity of the velocity in the non-ablated shell. The results of the integration of this system are well compared with numerical simulation of optimized capsules. Assuming that the ablation pressure depends only on the Hohlraum temperature, the relations between the non-ablated mass, the implosion velocity, and the ablation radius are obtained for optimized temperature shape. These relations provide the maximum implosion velocity and the remaining non-ablated mass in terms of the initial capsule and the maximum temperature (or the initial capsule mass in terms of the remaining non-ablated mass) useful to determine the required ablator thickness for optimized capsules. These results are also compared with numerical simulations of different capsules.

This paper presents a simplified theoretical model for the study of emission from laser produced plasma to better understand the processes and the factors involved in the onset of saturation in plasma emission as well as in increasing emission due to plasma confinement. This model considers that plasma emission is directly proportional to the square of plasma density, its volume, and the fraction of laser pulse absorbed through inverse Bremsstrahlung in the pre-formed plasma plume produced by the initial part of the laser. This shows that plasma density and temperature (that means the electron-ion collision frequency νei) decide the threshold for saturation in emission, which occurs for νei ≥ 1013 s−1, beyond which plasma shielding effects become dominant. Any decrease in plasma sound (expansion) velocity shows drastic enhancement in emission supporting the results obtained by magnetic as well as spatial confinement of laser produced plasma. The temporal evolution of plasma emission in the absence and presence of plasma confinement along with the effect of laser pulse duration are also discussed in the light of this model.

A XUV Michelson interferometer has been developed by LIXAM/CEA/LCFIO and has been tested as a Fourier-transform spectrometer for measurement of X-ray laser line shape. The observed strong deformation of the interference fringes limited the interest of such an interferometer for plasma probing. Because the fringe deformation was coming from a distortion of the beam splitter (5 × 5 mm2 open aperture, about 150 nm thick), several parameters of the multilayer deposition used for the beam splitter fabrication have been recently optimized. The flatness has been improved from 80 nm rms obtained by using the ion beam sputtering technique, to 20 nm rms by using the magnetron sputtering technique. Over 3 × 3 mm2, the beam splitter has a flatness better than 4 nm rms.

We studied X-ray emission from laser plasmas produced by irradiation of thin plastic foils with 1.064-μm Nd laser light at intensity up to 2 x 1013 W/cm2 with 3-ns pulses. The level of X-ray emission at different spectral windows was measured versus laser intensity and foil thickness. The electron temperature of the X-ray source was also measured. At intensity above 6 x 1012 W/cm2 our data showed the formation of nonthermal tails in the X-ray spectrum, which has been related to two plasmon decay instability.

The main goals of this review article are to show, on the basis of the results accumulated in this field, achievements in simulating the processes in nuclear pumped laser (NPL) active media by experiments on e-beam pumping, and to give a number of characteristic experimental examples, when this simulation has improved understanding of the inversion population processes in NPL active media (Cd+, Xe-lasers) or generated interest in experiments with fission fragments excitation (Ne-laser). In the case of the population of laser operation levels in non-equilibrium recombinating plasma, one can say with sufficient accuracy that the inversion population mechanism is identical for both excitation types.

The influence of plasma shielding effect induced by ambient gas pressure and laser intensity on the laser-produced Cu plasma parameters, signal-to-background ratio (S/B) and expansion are experimentally and numerically investigated. A Q-switched Nd:YAG laser at 1064 nm at various intensities ranging from 2 to 7.1 GW/cm2 intensity (40–150 mJ) is used to produce Cu plasma in air, argon (Ar), helium (He), and neon (Ne) ambient gas at various pressures ranging from 5 to 1000 mbar. Laser-induced breakdown spectroscopy reveals that spectral radiation, S/B, electron temperature, number density, and front edge velocity of the plasma have an increasing trend up to a certain value of laser intensity and gas pressure. Afterwards, a saturation trend is achieved, which is attributed to the shielding and self-regulation effect. The numerical modeling of the laser-produced Cu plasma in the presence of air at atmospheric pressure is carried out using the MULTI radiation hydrodynamics code. We have shown that the feature of plasma shielding effect observed in the experiments can be reproduced using a continuum hydrodynamics model. Laser intensity at about 3.5 GW/cm2 is found to produce the highest S/B at 1000 mbar air. He, Ne, air, and Ar show the best S/B, respectively and the best S/B is found for air, Ar, He, and Ne at 10, 5, 10, and 20 mbar, respectively. The expansion of plasma plume is studied using a simple and effective technique based on probe laser absorption and scattering method. The plasma plume expansion through He, Ne, air, and Ar at 1000 mbar pressure has the highest velocity, respectively. The simulated results of strong shock wave model and Rankine–Hugoniot jump condition are fitted to the experimental data, which are then used to estimate the values of the ablation parameters.