We present in this paper a theoretical modeling and a numerical simulation devoted to the problem of transport and energy deposition profile of high current light ion beams interacting with dense matter. A numerical code, named MBC-ITFIP, is used to follow the trajectories of light atomic or molecular ions inside plasma targets with non-uniform density, temperature and composition profiles. MBC-ITFIP has been more specifically optimized for application of ion beams generated by the new high intensity laser sources, such as radiography and isochoric heating of dense plasmas.

Since their discovery, laser accelerated ion beams have been the subject of great interest. The ion beam peak power and beam emittance is unmatched by any conventionally accelerated ion beam. Due to the unique quality, a wealth of applications has been proposed, and the first experiments confirmed their prospects. Laser ion acceleration is strongly linked to the generation and transport of hot electrons by the interaction of ultra-intense laser light with matter. Comparing ion acceleration experiments at laser systems with different beam parameters and using targets of varying thickness, material and temperature, some insight on the underlying physics can be obtained. The paper will present experimental results obtained at different laser systems, first beam quality measurement on laser accelerated heavy ions, and ion beam source size measurements at different laser parameters. Using structured targets, we compare information obtained from micro patterned ion beams about the accelerating electron sheath, and the influence of magnetic fields on the electron transport inside conducting targets.

We present the current status-of-the-art in Stark broadening theory as a theoretical basis for diagnostics of low temperature plasmas in gas discharges, and of high temperature laser produced or z-pinch dense plasmas. The diagnostics abilities vary depending on the parameters of the gas discharges, or on the range of intensity, and duration of the laser or z-pinch pulses. In the case of high temperature plasmas, besides the conventional diagnostics based on the Stark broadening, the contemporary possibilities of UV and XUV interferometry for plasma density measurements and of tomography reconstruction of the macroscopic gradients of temperature and densities in laser produced plasmas are discussed.

Recently, warm dense matter has emerged as an interdisciplinary field that draws increasing interest in plasma physics, condensed matter physics, high pressure science, astrophysics, inertial confinement fusion, as well as material science under extreme conditions. To allow the study of well-defined warm dense matter states, we introduced the concept of idealized slab plasma (ISP) that can be realized in the laboratory via (1) the isochoric heating of a solid and (2) the propagation of a shock wave in a solid. The application of this concept provides new means for probing AC conductivity, equation of state, ionization, and opacity. These approaches are presented here using results derived from numerical simulations.

The electromagnetic acceleration of a metallic ring carrying a high current, combined with the mutual interaction of a concentrical conductor carrying the same current, in the presence of a DC magnetic field, results in a converging beam of particles reaching a velocity above 1000 km/s. Lithium, gold, and uranium rings are considered and transient temperatures ranging from 108 to 1010 °K are expected. In the presence of deuterium and tritium fusion reactions will occur and the capture of the released neutrons may result in the synthesis of heavier elements. The considered device lends itself to a varied treatment allowing to consider velocities in the range of 2000 km/s.

The paper presents the first experimental results obtained by using new gamma-quantum diagnostics for ion beam induced high energy density matter. Registration of γ-quantum output from the region of beam-target interaction with time resolution enables to pick-up information on density evolution of the target even if the ionization state of matter involved is unknown.

The paper gives a review of investigations on generation of soft X-rays and EUV using a gas puff target irradiated with high-power laser pulses performed during last few years. In the studies a newly developed double-stream gas puff target approach was used. The gas puff targets were irradiated with various lasers, including Nd:glass, Kr:F, Nd:YAG, and iodine lasers. The aim of the studies was to develop efficient and debris-free laser plasma X-ray and EUV sources for applications in microscopy, lithography, micro- and nanotechnology.

The recently proposed backward Raman laser amplification scheme utilizes the stimulated Raman backscattering in plasma of a long pumping laser pulse to amplify a short, and frequency downshifted seed pulse. The output intensity for this scheme is limited by the development of forward Raman scattering (FRS) or modulational instabilities of the highly amplified seed. Theoretically, focused output intensities as high as 1025 W/cm2, and pulse lengths of less than 100 fs, could be accessible by this technique for 1 μm lasers—an improvement of 104–105 in focused intensity over current techniques. Simulations with the particle-in-cell (PIC) code Zohar are presented, which investigate the effects of FRS and modulational instabilities, and of Langmuir wave breaking on the output intensity for Raman amplification. Using the intense seed pulse to photoionize the plasma simultaneous with its amplification (and hence avoid plasmas-based instabilities of the pump) is also investigated by PIC simulations. It is shown that both approaches can access focused intensities in the 1025 W/cm2 range.

The properties of an electron beam (e-beam) formed in air under atmospheric pressure are reported. The nanosecond generators RADAN-303 (two devices) and RADAN-220, producing nanosecond voltage pulses with amplitude of up to 400 kV and subnanosecond rise time were used in the experiments. It was shown for the first time that the duration of e-beam current of gas diode behind the foil does not exceed 0.1 ns. The maximum amplitude of current of a supershort avalanche electron beam (SAEB) behind the foil was ∼400 A. The data on the influence of various parameters on e-beam current amplitude measured behind the foil were obtained. An electron beam with energy less than 60 keV and powerful X-ray radiation were formed in discharge gap simultaneously with SAEB.

We investigate intermediate unstable modes between two stream and filamentation instabilities. We detail the problem of the angle between the wave vector and its electric field and use an electromagnetic formalism allowing for any value for this angle. We display analytical results for 3 different models: cold beam-cold plasma, cold beam-hot plasma and cold relativistic beam-hot plasma. We demonstrate that plasma temperature prompts a critical angle for which waves are unstable at any k and show that for a relativistic beam, the most unstable waves are obtained for wave vectors which are neither normal nor perpendicular to the beam.

Explicit relations are developed to estimate the outflux of migrating isotopomers iQF6 to the outskirts of a supersonic supercooled free jet whose core is irradiated by a co-axial laser beam and intercepted by a skimmer that separates core gas from peripheral gases. The QF6 target gas is diluted in carrier gas G (G = He, N2, Ar, Xe, SF6, etc.) which determines the jet's supersonic characteristics and forms QF6:G dimers at low temperatures. Under isotope-selective laser excitation, excited iQF6* convert their vibrational energy V into kinetic energy T after forming transient iQF6*:G dimers that dissociate in sub-microseconds. Three migrating groups with different transport parameters are created in the jet: thermal monomers, faster-moving epithermal monomers, and slower-moving dimers. Jet-core-fleeing QF6 is enriched in iQF6 due to enhanced outwards migration of iQF6! epithermals and reduced escape of jQF6:G dimers in the jet. Isotope enrichments in the rim gases are highest for heavier carrier gases such as G = Xe or G = SF6.

A beam combination laser with stimulated Brillouin scattering-phase conjugate mirrors (SBS-PCMs), which is expected to produce a high output energy and power with a repetition rate over 10 Hz, is a candidate for a practically useful laser fusion driver in the future. In order to develop the beam combination laser with SBS-PCMs, it is necessary to control the phase of each SBS wave whose phases are known as inherently random. We have proposed a new phase control technique and demonstrated experimentally that the relative phase difference between two SBS waves can be controlled to a certain value and locked to it with an accuracy less than λ/4. Additionally we have proposed and demonstrated a new technique to preserve the pulse shape of the SBS wave. Based on these experimental results, we have proposed two schemes of the new schemes for the high repetition and high energy/power beam combination laser system (laser fusion driver) using the SBS-PCMs of amplitude division and wave-front division techniques, which can operate with repetition rate over 10 Hz, in this paper.

The gas discharge in a gas peaking switch was experimentally studied and numerically simulated. For simulation, the discharge was divided into two phases, gas breakdown and voltage collapse. The criterion for an electron avalanche to transit to streamer was considered as the criterion of gas breakdown. The spark channel theory developed by Rompe-Weizel was used to calculate the spark resistance. It was found that the prepulse considerably lowers the voltage pulse applied to the gap. Even for a given input pulse, the voltage pulse applied to a peaking gap is different for different gap distance due to existence of a different prepulse. In this case, the breakdown voltage of a gas peaking gap depends on gas pressure and gap distance, individually. For nitrogen pressure varying from 3 MPa to 10 MPa and gap distance from 0.6 mm to 1.2 mm, the peak electric field higher than 2 MV/cm was achieved when breakdown. The output 10% to 90% rise time, tr, varies from 145 ps to 192 ps. As gas pressure increases, tr decreases, which can be explained by the fact that the breakdown field increases with the increase of gas pressure. It was found in experiment that the jitter in tr could be attributed to the jitter in breakdown field. Instead of getting longer, the averaged experimental tr gets shorter as gap distance increases from 0.6 mm to 1.2 mm, which differs from the results of calculation and indicates there may exist something, other than electric field, that is also related to tr. The reason for this difference may lies in the inverse coefficient of spark resistance varying with gap distance. On the whole, the results from the calculations agree with the experimental ones.

The requirements of matching shell ICF target parameters, parameters of compressing, and triggering drivers under direct (fast) ignition are developed. Thin shell target, which represents a shell-ablator with a DT-ice layer, frosted on the inner surface of the shell are considered. Design of a target which ensures the energy supply from the triggering driver to the central part of thermonuclear fuel, in both spherical and cylindrical geometry is developed. Spherical target is furnished with one or two conical channels for the injection of the triggering driver radiation. The ends of the cylindrical target are protected by heavy material walls that have the holes of the radius equal to the final radius of compressed fuel. It was found that the parameters of fast ignition spherical and cylindrical targets, which provide high thermonuclear gain of 500–2000 in the range of the compressing driver energy of 1–10 MJ, may be matched with the drivers parameters at low aspect ratios of the targets, 10–20. The operation of spherical targets at the moderate radius convergence ratio of 15–20, may be provided at the triggering driver energy not higher than 30 kJ. The operation of cylindrical target with spin-oriented DT-fuel at radius convergence ratio of 20–25 may be provided at 150–200 kJ of the triggering driver energy.

This paper reports on the status of the PHELIX petawatt laser which is built at the Gesellschaft fuer Schwerionenforschung (GSI) in close collaboration with the Lawrence Livermore National Laboratory (LLNL), and the Commissariat à l'Energie Atomique (CEA) in France. First experiments carried out with the chirped pulse amplification (CPA) front-end will also be briefly reviewed.

We investigated the optical properties of pure copper irradiated by a femtosecond laser pulse. Self-absorption of 50-fs laser pulses at 800 nm and 400 nm wavelengths (below and above the interband absorption threshold, respectively) is studied for peak laser intensities up to 1015 W/cm2. Theoretical description of laser interaction with copper target is developed, solving numerically the energy balance equations for electron and ion subsystems together with Maxwell equations for laser radiation field inside the target. The theory accounts for both intraband and interband absorption mechanisms. We treated in detail the changes in electron structure and distribution function with an increase in electron temperature, as well as the ensuing changes in thermodynamic properties, collision frequencies, optical and transport coefficients. Experimental work on self-absorption of femtosecond laser pulses in copper targets at 800 nm and 400 nm wavelengths is ongoing. Results for 800 nm wavelength are reported. Theory and experiment are in good agreement.

A joule level of XeF(C-A) laser optically pumped by a sectioned surface discharge was developed. The irradiative intensity of pumping source was diagnosed by calculating XeF2 photo-dissociation wave evolvement which was photographed by a framing camera. The photon flux in the wavelength region of 140 to 170nm is about 5 × 1023 photon s−1cm−2, that corresponds to the irradiative brightness temperature of more than 25000 K. The laser experiments were carried out in different conditions. The maximum laser output energy of 2.5 J was obtained with the total conversion efficiency of 0.1%.

Inertial fusion energy (IFE) research indicates that the energy generation by means of cryogenic fuel target compression requires that targets must be injected to the target chamber center at a rate of about 6 Hz. This requirement can be fulfilled only if the targets are free-standing. The most interesting results concerning the activity of the Lebedev Physical Institute in the area of free-standing targets (FST) fabrication, characterization and delivery are presented.

Volume 23, Number 1, Pages 47–53, 2005

Below is the complete Reference citation for Neumayer et al. (2005).

Neumayer, P., Bock, R., Borneis, S., Brambrink, E., Brand, H., Caird, J., Campbell, E.M., Gaul, E., Goette, S., Haefner, C., Hahn, T., Heuck, H.M., Hoffmann, D.H.H., Javorkova, D., Kluge, H.-J., Kuehl, Th., Kunzer, S., Merz, T., Onkels, E., Perry, M.D., Reemts, D., Roth, M., Samek, S., Schaumann, G., Schrader, F., Seelig, W., Tauschwitz, A., Thiel, R., Ursescu, D., Wiewior, P., Wittrock, U. & Zielbauer, B. (2005). Status of PHELIX laser and first experiments. Laser Part. Beams23, 87–93.

Volume 23, Number 1, Pages 5–8, 2005

Below is the complete Reference citation for Bret et al. (2005).

Bret, A., Firp, M.-C. & Deutsch, C. (2005). Bridging the gap between two stream and filamentation instabilities. Laser Part. Beams23, 373–381.