In our earlier papers, we demonstrated that plasma pressure decreases with the growing atomic number of the target material. That experimentally confirmed fact brought about a question whether it would be possible to collimate the Al plasma outflow by using plastic plasma as a compressor. To prove that idea we used in our next experiments a plastic target with an Al cylindrical insert of 400 µm in diameter. The measurements were carried out at the Prague Asterix Laser System iodine laser facility. The laser provided a 250 ps (full width at half maximum (FWHM)) pulse with energy of 130 J at the third harmonic frequency (λ3 = 0.438 µm). The focal spot diameters (ΦL) 800, 1000, and 1200 µm ensured predominance of the plastic plasma amount high enough for the effective Al plasma compression. To study the Al plasma stream propagation and its interaction with plastic plasma a three-frame interferometric system and an X-ray camera were used. The experiment provided a proof that creation of the collimated Al plasma jet by action of outer plastic plasma is feasible. In order to discuss of the experimental results a thorough theoretical analysis was carried out.

Gyrating ion beams, produced by quick ionization of neutral beams, employed for plasma heating, are susceptible to ion Bernstein and ion cyclotron instabilities. The Bernstein wave, having large parallel phase velocity, is excited via cyclotron interaction whereas the ion cyclotron wave with lower parallel phase velocity could be driven by Cerenkov interaction as well. The maximally growing modes have transverse wave number of the order of inverse ion Larmor radius. The nonlocal effects cause reduction in the growth rate.

In this paper, a scheme of compound optical limiting based on nonlinear material dissolved into Brillouin medium is proposed. Both nonlinear material and Brillouin medium used as the solvent play roles of optical limiting, so the proposed optical limiting scheme presents a lower output clamp value and flatter output energy compared with the single stimulated Brillouin scattering (SBS). Compound optical limiting of F16PCCu/acetone is prepared and output energy characteristic based on it is studied in this paper. Both the theoretical and experimental results indicate that the output clamp value and output energy based on the compound method is lower and flatter than that based on single SBS optical limiting. Some properties of the compound optical limiting, such as limiting energy range, limiting waveband, response speed, limiting threshold and damage threshold, also are analyzed and discussed in the later part of this paper.

A high-current electron-beam accelerator for pumping of a Xe2 lamp was developed. It is intended for injection of an electron beam into cylindrical gas cavity (diameter of 400 mm, length of 1600 mm, and the absolute pressure up to 3 bars). Two electron diodes in parallel are used in the accelerator. Each diode is connected to a linear transformer driver with vacuum insulation of a secondary turn. The next parameters of the accelerator have been obtained: diode voltage — 550–600 kV, diode current — 276–230 kA, current rise time — 160 ns, maximum power of the electron beam — 130 GW, pulse width on half maximum — 160 ns, electron beam energy at power level not less than half of maximum value — 20 kJ. The total energy of electrons, which pass through a 40 µm Ti foil into the Xe cell, is 8–9 kJ in the 150–160 ns pulse (full width at half maximum) mean specific power of energy input into gas cavity is about 330 kW/cm3. Design of the accelerator and test results are presented and discussed in this paper.

The hot spot heating process by an assumed deuteron beam is evaluated in order to estimate the contribution of the energy produced by the deuteron beam-target fusion to the heating process. The deuteron beam energy versus the number of deuterons is evaluated through the experimentally achieved proton beam energy distribution using the TRIDENT short pulse laser at the Los Alamos National Laboratory (LANL). The corresponding hot spot heating is then calculated using this assumed deuteron beam spectrum. The resulting first order heating dynamics is employed in the expanded “bonus” energy calculation, and a 12.73% extra energy from deuteron beam-target fusion was found with the assumed deuteron spectrum when ρrb = 4.5 g/cm2 is considered, where ρ is the fuel density, and rb is the ion beam focusing radius on the target. The results provide further insight into the contribution of the extra heat produced by deuteron beam-target fusion to the hot spot ignition process. A further analysis of how a converter foil using ultra-high-density cluster materials can help to achieve the yield requirements for ignition is presented.

The effects of laser incidence angle on lateral fast electron transport at front target surface, when a plasma is preformed, irradiated by intense (>1018 W/cm2) laser pulses, are studied by Kα imaging technique and electron spectrometer. A horizontally asymmetric Kα halo, resulting from directional lateral electron transport and energy deposition, is observed for a large incidence angle (70°). Moreover, a group of MeV high energy electrons is emitted along target surface. It is believed that the deformed preplasma and the asymmetrical distribution of self-generated magnetic field, at large incidence angle, play an important role in the directional lateral electron transport.

We report on experiments aimed at the generation and characterization of solid density plasmas at the free-electron laser FLASH in Hamburg. Aluminum samples were irradiated with XUV pulses at 13.5 nm wavelength (92 eV photon energy). The pulses with duration of a few tens of femtoseconds and pulse energy up to 100 µJ are focused to intensities ranging between 1013 and 1017 W/cm2. We investigate the absorption and temporal evolution of the sample under irradiation by use of XUV and optical spectroscopy. We discuss the origin of saturable absorption, radiative decay, bremsstrahlung and atomic and ionic line emission. Our experimental results are in good agreement with simulations.

This work demonstrates the patterning of polymethylmethacrylate (PMMA) by ablation with Ar8+ ion laser (λ = 46.9 nm) pumped by pulse, high-current, capillary-discharge. For focusing a long-focal spherical mirror (R = 2100 mm) covered by 14 double-layer Sc-Si coating was used. The ablated focal spots demonstrate not only that the energy of our laser is sufficient for such experiments, but also that the design of focusing optics must be more sophisticated: severe aberrations were revealed — an irregular spot shape and strong astigmatism with astigmatic difference as large as 16 mm. In some cases, on the bottom of ablated spots a laser-induced periodic surface structure appeared. Finally, an illumination of the sample through quadratic hole 7.5 × 7.5 µm, standing in contact with PMMA substrate ablated from the surface a strongly developed two-dimensional diffraction pattern (period in the center about 125 nm).

The results of the development of the ITEP accelerator carbon ion injector based on a repetition-rate CO2 laser ion source are described. The improvement includes a modified pulsed HV-feeding generator for the discharge formation in the laser gas mixture. The advanced discharge module ensures essential increase of the laser active volume and specific electrical deposition energy. The comparative computer simulations of the discharge characteristics for the improved and the prototype lasers are applied. The design and the output spatial-temporal parameters of the free-running laser “Malish-M” are shown, so the significant increase of the laser power is reached. The spatial characteristics of the laser beam obtained with diffraction calculations are compared to measured radial distribution of the energy density. The target laser intensity and the different channels of the energy loss of the laser beam in the optical scheme are estimated. Finally, the output C4+ current trace of heavy ion injector as well as the injector scheme are shown.

The effect of temporal pulse-shape on the characterization of the longitudinal electric field resulting from the tight-focusing of an ultrashort few-cycle TM01 laser beam in free space is investigated analytically and numerically. The longitudinal field is found to be sensitive to the pulse-shape of the driving field. The temporal pulse-shapes considered are Gaussian, Lorentzian, and hyperbolic secant having identical full width at half maximum of intensity. Analytical calculations are made beyond the paraxial and slowly varying envelope approximations. From the numerical results we find that due to finite duration of the signal, the evolution of the pulse envelope before the waist is faster (negative time-delay) but slowed down (positive time-delay) after the waist. This time-delay, for single-cycle pulses of wavelength λ0, and for spot-size w0f in the range 0.6λ0 > w0f > 0.25λ0, is pulse-shape dependent. The time delay is maximum for the Gaussian pulse and minimum for the Lorentzian pulse. The carrier frequency shift depends on the temporal profile of the pulse, beam spot size, axial propagating distance and also on the number of cycles in a pulse. In addition, a comparative study of the variation of the corrected axial Gouy- phase of the longitudinal electric field of single-cycle pulse (spot size w0f = 0.5λ0) with normalized retarded time shows that the phase variation is maximum for Gaussian and minimum for the Lorentzian pulse shape.

To diagnose the implosion of a laser-driven-fusion target such as the symmetry, the hydrodynamic instability at the interface, a high-resolution, large field-of-view kilo-electron-volt X-ray imaging is required. A Kirkpatrick-Baez (K-B) microscope is commonly used, but its field of view is limited to a few hundred microns as the resolution decreases rapidly with the increase of the field of view. A higher resolution could be realized by using a Fresnel zone plate (FZP) for imaging. Presented in this work is a numerical study on the imaging properties of an FZP at Ti-Kα wavelength of 0.275 nm, and a comparison to a K-B imager. It is found that the FZP can realize not only a resolution better than 1 µm, but also a field-of-view larger than 20 mm when the FZP is illuminated by X-rays of spectral bandwidth less than 1.75%. These results indicate the feasibility of applying the FZP in high-resolution, large field-of-view X-ray imaging.

We investigated generation of pre-formed plasma on plates and inside cone targets due to a pre-pulse before the arrival of the main ultra-intense laser pulse in the fast-ignition scheme of the inertial confinement fusion. We estimated the pre-pulse level to be 130 mJ for LFEX laser used in the 2009 FIREX experiment, and the density gradient scale length of the pre-formed plasma inside the cone target to be 27–47 microns between the critical and 1/10 of the critical density, based on the two-dimensional radiation hydrodynamic simulations. In order to reduce the generation of pre-formed plasma, we investigated a thin CH foil pre-pulse absorber, and proposed using a cone target with a pointed tip. We simulated CH plasma expansion to show that the CH foils works as a pre-pulse absorber. We also show the aluminum pointed tip of the cone target can delay the shock arrival time by 20 ps, much longer than the delay for the 10 micron thickness gold tip used in the typical implosion of GXII at Osaka University.

Long-scale preformed plasmas are generated inside the cone by the pre-pulse of the heating laser in the cone-guided fast ignition scheme and it is found that coupling efficiency from the heating laser to fast electrons especially suitable for core heating is drastically reduced by the preformed plasmas. To mitigate this serious problem, an extremely thin film is suggested to cover the entrance of the cone. This method, however, introduces long rarefied plasmas around the entrance of the cone and the main pulse must propagate through these plasmas. Therefore, fast electron characteristics produced by the main pulse could be affected, and effects of long rarefied plasmas on fast electron generation are investigated. It is found that the electron beam intensity becomes larger than that without the rarefied plasma, but the energy coupling rate from the heating laser to the core decreases due to lack of appropriate electrons for core heating. To achieve less than 10% degradation of the core electron temperature, the thin film must be expanded by irradiation of the pre-pulse so that the length and the density of rarefied plasmas become less than 500 µm and one-tenth of the critical density. A thickness of the thin film can be determined by these criteria and the intensity of the pre-pulse.

The electromagnetic field structures and transport properties of laser produced relativistic beam electrons propagating through Au+25, Cu+20, Al+10, and C+5 plasma foils are investigated. Simulations show that high plasma resistivity as well as high collision rate of the beam electrons with gold and copper plasmas can hinder the forward motion of the beam electrons inside the targets. However, the beam electrons can propagate for a relatively long distance in aluminum and carbon plasma targets. They are well collimated by the strong self-generated resistive magnetic field, resulting in higher sheath electric fields behind the target. The use of low-Z target material is therefore more efficient for collimating beam electrons as well as generating higher-energy ions.

The current trends in stimulated Brillouin scattering and optical phase conjugation are overviewed. This report is formed by the selected papers presented in the “Fifth International Workshop on stimulated Brillouin scattering and phase conjugation 2010” in Japan. The nonlinear properties of phase conjugation based on stimulated Brillouin scattering and photo-refraction can compensate phase distortions in the high power laser systems, and they will also open up potentially novel laser technologies, e.g., phase stabilization, beam combination, pulse compression, ultrafast pulse shaping, and arbitrary waveform generation.