The journal of Laser and Particle Beams wants to take this opportunity to congratulate Dr. Max Tabak and Dr. Joseph D. Kilkenny on the occasion of being selected by the American Nuclear Society as winners of the 2005 Edward Teller award. Both scientists were recognized for their pioneering work in the field of fusion research. Nuclear fusion and especially inertial confinement fusion constitutes a specific field of interest which is frequently discussed in this Journal. Both scientists have previously contributed to this journal, and we are very proud that our recent December 2005 issue carried an article by Kilkenny et al. (2005), related to this topic. The same issue carries articles by two former Teller Award winners (Hora, 2005; Miley et al., 2005).

The Second International Conference on the Frontiers of Plasma Physics and Technology was held in Goa, India, from February 21–25, 2005. This conference explored a number of fundamental and applied plasma physics topics. Special attention was focused on the exploration of frontiers in physics and technology of high energy density plasmas—a topic growing at a very fast pace due to the emergence of extremely powerful laser sources. Reviews on activities and new opportunities for large laser facilities in prominent laboratories of Asia, Europe, and Canada were presented. Talks on recent advances on laser driven Wakefield particle acceleration scheme were very exciting. This technology has a strong potential of revolutionizing the existing accelerator physics, technology, and radiation sources such as synchrotrons and X-ray free-electron lasers. Discussions were also given on the generation of extreme physical conditions similar to those existing in astrophysical objects, under laboratory conditions using intense lasers. This technique may lead to an easy and inexpensive way to simulate and understand a variety of astrophysical phenomena. This aspect of realization of astrophysical conditions in a laboratory has now become reality, and soon may lead to routine experiments. New applications of laser in the designs of light-crafts may soon become reliable.

Fast electrons are effectively generated from solid targets of cone-geometry by irradiating intense laser pulses, which is applied to fast ignition scheme. For realizing optimal core heating by those electrons, understanding the characteristics of electrons emitted from cone targets is crucial. In this paper, in order to understand the generation and transport processes of hot electrons inside the cone target, two-dimensional (2D) particle-in-cell (PIC) simulations were carried out. It is shown that hot electrons form current layers which are guided by self-generated surface magnetic field, which results in effective energy transfer from laser pulse to hot electrons. When the hot electrons propagate through the steep density gradient at the cone tip, electrostatic field is induced via Weibel instability. As a result, hot electrons are confined inside and emitted gradually from the target, as an electron beam of long duration. Energy spectrum and temporal profile of hot electrons are also evaluated at the rear side of the target, where the profile of rear side plasma is taken from the fluid code and the result is sent to Fokker-Planck code.

Very good absorption of ultra short laser pulses by clusters is a well established fact. Efficient collisional absorption occurs only in the initial phase of the pulse. However, experiments and numerical simulations show that even after collisional absorption becomes inefficient subsequent to heating of the electrons, strong absorption continues. There have been a few attempts to model this phenomenon in terms of driven “linear” oscillator models with time dependent eigen-frequencies. Here we propose a nonlinear oscillator model and show that nonlinear resonance is the leading mechanism responsible for the collisionless absorption. Further it is demonstrated, on the basis of Lyapunov spectra, that laser-cluster interaction, under certain conditions, exhibits chaotic behavior.

In this paper we present the analytical description of two processes dealing with the skin-layer ponderomotive acceleration method of fast ion generation by a short laser pulse: ion density rippling in the underdense plasma region and generation of ion beams by trapped electromagnetic field in plasma. Some numerical examples of hydrodynamic simulation illustrating these processes are shown. The effect of using the laser pulse consisting of different frequency components on the ion density rippling and on phenomena connected with trapped electromagnetic field is analyzed.

We will consider relativistic electron beam interacting with plasma and study the electromagnetic instabilities obtained for arbitrarily oriented wave vectors ranging from two-stream to filamentation instabilities. For these unstable modes, we will study every temperature effects, namely beam and plasma normal, and parallel temperatures. Temperatures are supposed to be non-relativistic and modeled through water bag distributions. It is found that only normal beam temperature and parallel plasma temperature have a significative influence over the growth rates for wave vector making an angle with the beam larger than a critical angle θc which is determined exactly. The largest growth rate being reached for a wave vector making an angle with the beam smaller than θc, it is not damped by any kind of temperatures. We finally explore collisions effects and show they can reduce the largest growth rate.

A new theory for the nuclear forces for confining the nucleons in a nucleus was derived from a generalization of the Debye layer as known from the plasma ablation at laser irradiation where the temperature is substituted by the Fermi energy of the statistics of nucleons. The first convincing proof is by using the empirical density of the nucleons defining their Fermi energy to arrive at a Debye length of about 3 fm as measured by Hofstadter for the decay of the nucleon density at the surface of heavy nuclei. Taking then the surface tension of plasmas with the same steps of substituting temperature by Fermi energy, the surface energy of nuclei is always too small against the nucleon enthalpy to confine the nucleons until equilibrium is reduced at about such high densities reproducing the well known radii of nuclei. The Hofstadter decay can be interpreted as the inhomogeneous wave of the nucleons by Wigner scattering at the nuclear surface similar to the Goos-Haenchen effect. By this way, nuclei are possible only until uranium or curium by a Boltzmann equilibrium process explaining the endothermic generation of heavy nuclei. At about six times higher nucleon density, the Fermi statistics changes into its relativistic branch resulting in a surface energy always smaller than before, and the mass and density independence indicates that one cannot distinguish between the state as in a neutron star or as a quark-gluon plasma. The steps from the ablation of laser produced plasma via a quantum theory of the surface tension in metals to the new nuclear force theory are explained. A consideration of the magic numbers indicates a quark-shell structure of nuclei.

For biological hard tissues as well as for artificial restoration materials, ultra-short laser pulses (USLP) have proven their suitability for ablation with negligible collateral damage providing many advantages. For this paper, it was the aim to investigate the suitability of scanned USLP for the ablation of dental restorative materials compared to the microsecond pulses of conventional Erbium lasers. Scanning electron microscopy allowed analyzing the quality of the cavity surfaces with respect to structural properties as well as temperature exposition. Quantitative results about the ablation efficiency are given for different laser parameters on dental hard tissue and a broad variety of dental restoration materials, the latter being reported for the first time.

This paper reports the formation of low-energy low-divergence pulsed indium atomic beam via ablation of thin film by illumination from the rear side with second harmonic of Q-switched Nd:YAG laser under high vacuum (∼10−5 Torr). Angular divergence of ablated indium atomic, reflectivity modulation of thin film due to ablation, and longitudinal atomic velocity of ablated beam were studied as a function of laser fluence. Atomic force microscope scans of the deposited multiple shots of pulsed atomic beams show the formation of “nano-hills.”

This paper presents theoretical results for the influence of plasma electron-electron collisions in correlated proton stopping forces. First calculations of the effects of these collisions on the vicinage forces for plasma matter are shown. In particular, these effects are studied in a Te = 10 eV and n = 1023 cm−3 plasma yielding a self-retarding proton force increased more than 11% at maximum value. Also vicinage forces enhances more than 15% in the analyzed cases. All this implies that plasma electron-electron collisions play an important role both in non and correlated ion stopping and must be considered for any application of ion energy deposition in plasma matter.

Starting from the Riemann-Silberstein formulation of classical electrodynamics the Schrödinger equation for the photon energy wave function is discussed. Hereafter, a propagator description of the space-time emission of a polychromatic photon from an atom is presented, paying particular attention to the near-field electrodynamics. When the atom is embedded in a solid-state plasma the photon emission process can be dramatically modified. Limiting the analyses to solid-state plasmas exhibiting translational and rotational symmetry, the near-field atom-photon-plasma interaction is studied paying particular attention to the plasmariton and plasmon excitation processes. It is shown that the transverse and longitudinal parts of the plasma-screened field propagator link in a direct manner to the free-photon propagator and the longitudinal near-field photon propagator. The necessity of keeping both the transverse and longitudinal parts of the plasma screening in a rigorous description of near-field electrodynamics is demonstrated.

The transport of high-current heavy-ion beams in plasma channels is a promising option for the final transport in a heavy-ion fusion reactor, since it simplifies the construction of the reactor chamber significantly. Our experiments at the Gesellschaft für Schwerionenforschung demonstrate the creation of 1 m long stable plasma channels and the transport of heavy-ion beams. The article outlines the experimental setup used at GSI and reports the results of beam transport measurements using these long channels. The experiments demonstrate good beam transport properties of the channel, indicating that channel transport is a viable alternative to neutralized-ballistic transport.

We study the details of a gradual change in electron properties from those of a nearly-free-electron (NFE) metal to those of a strongly-coupled plasma, in ultrashort pulse energy deposition in solid metal targets. Time scales shorter than those of a target surface layer expansion are considered. Both the case of an optical laser (visible or near infrared wavelengths range) and of a free electron laser (vacuum ultraviolet or X-ray) are treated. The mechanisms responsible for the change in electron behavior are isochoric melting, lattice charge disordering, and electron mean free path reduction. We find that the transition from metal to plasma usually occurs via an intermediate stage of a charge-disordered solid (solid plasma), in which ions are at their lattice sites but the ionization stages of individual ions differ due to ionization from localized bound states. Charge disordered state formation is very rapid (typically, few femtoseconds or few tens of femtoseconds). Pathway to charge-disordered state differs in simple metals and in noble metals. Probabilities are derived for electron impact ionization and 3-body recombination of a bound ionic state in solid-density medium, applicable both in metal and in plasma regime. An evolution of energy coupling between electron and ion subsystems, from metallic electron-phonon (e-ph) to plasma electron-ion (e-i) coupling, is considered. Substantial increase in coupling parameter is expected as a result of charge disorder.

We have demonstrated the acceleration of a monoenergetic electron beam by a laser-produced wakefield. Experiments were performed by focusing 2-TW laser pulses of 50 fs on supersonic gas-jet targets. The focused intensity was 5 × 1018 W/cm2 (a0 = 1.5). At an electron density of 1.5 × 1020 cm−3, the clear monoenergetic electron beam from the plasma was obtained at 7 to 15 MeV. The Stokes satellite peak in the forward scattering explained the energy spectra of electrons at various plasma densities well. Although the wakefield propagated 500 microns, which was far beyond the dephasing length, monoenergetic electron beams were obtained.

We describe here the present status of the Advanced Laser Light Source (ALLS) facility, a state-of-the-art multi-beam Ti:sapphire laser system presently under construction in Canada. ALLS is a national user facility to be commissioned in 2005 at the INRS campus near Montreal. The 25 fs ALLS multi-beam laser system has three components, each with different repetition rate and output energy. These multiple laser beams will be used to generate a “rainbow” of femtosecond pulses from the far infrared to hard X-rays, which can be combined to perform unique experiments, such as dynamic molecular imaging. In this paper, we describe two examples of experiments that are planned by our group with the ALLS facility. The first is the highly efficient generation of high-order harmonics using ablation medium. We demonstrate the generation of up to the 53rd harmonics (λ = 15 nm) of a Ti:sapphire laser pulse (150 fs, 10 mJ), using pre-pulse (210 ps, 24 mJ) produced boron ablation as the nonlinear medium. The second example is the demonstration of in-line phase-contrast imaging with an ultrafast (300 fs) laser-based hard X-ray source (Mo K-α line). Images of biological samples have shown great enhancement of contrast due to this technique, distinguishing details that are barely observable or even undetectable in absorption images.

Acceleration of quasineutral plasma blocks by ponderomotive force induced by normally incident short laser pulse is studied here via 1D3V Particle-In-Cell (PIC) simulations. Very high current densities 109–1011 Acm−2 of accelerated ions are observed for maximum laser intensities in the range 1016–1018 Wcm−2 on solid hydrogen target. Ion acceleration process is traced here via evolution of ion density and of ion velocity distribution. Basic parameters of the accelerated plasma blocks are determined from temporally integrated ion distributions. Our results provide more detailed information than the previous analytical estimates (Hora, 2003) and the two-fluid 1D hydrodynamic simulations (Glowacz et al., 2004).

Models for the prediction of electron pedestal temperatures at the edge of type I ELMy H-mode plasmas are developed. These models are based on theory motivated concepts for pedestal width and pressure gradient. The pedestal pressure gradient is assumed to be limited by high n ballooning mode instabilities, where both the first and second stability limits are considered. The effect of the bootstrap current, which reduces the magnetic shear in the steep pressure gradient region at the edge of the H-mode plasma, can result in access to the second stability of ballooning mode. In these pedestal models, the magnetic shear and safety factor are calculated at one pedestal width away from separatrix. The predictions of these models are compared with the experimental electron pedestal temperatures for type I ELMy H-mode discharges obtained from the latest public version (version 3.2) in the International Tokamak Physics Activity Edge (ITPA) Pedestal Database.

High-energy protons are generated by focusing an ultrashort pulsed high intensity laser at the Advanced Photon Research Center, JAERI-Kansai onto thin (thickness <10 μm) Tantalum targets. The laser intensities are about 4 × 1018 W/cm2. The prepulse level of the laser pulse is measured with combination of a PIN photo diode and a cross correlator and is less than 10−6. A quarter-wave plate is installed into the laser beam line to create circularly polarized pulses. Collimated high energy protons are observed with CH coated Tantalum targets irradiated with the circularly polarized laser pulses. The beam divergence of the generated proton beam is measured with a CR-39 track detector and is about 6 mrad.

Recent particle-in-cell simulations of the stimulated Brillouin backscattering (SBBS) of electromagnetic radiation have shown that even at sub-relativistic intensities (Iλ2 = 1016 Wμm2/cm2) non-drifting solitary waves, “solitons” for short, are easily produced, and remain almost unchanged all along the simulation time, typically for several thousands of optical cycles. They appear in the form of stable local concentrations of electromagnetic radiation trapped inside quasi-neutral density holes. The plasma density inhomogeneity associated with their presence disrupts the resonant SBBS amplification. The cavitation process is accompanied by strong electron and ion heating. The physical characteristics of such solitons are discussed and they are compared with the theoretical predictions of an analytical model for localized solution of the Maxwell equations in warm plasma.

This study deals with the simulation of the experimental study of Roth et al. (2000) on the interaction of energetic Zn projectiles in partially ionized laser produced carbon targets, and with similar type experiments. Particular attention is paid to the specific contributions of the K and L shell target electrons to electron recombination in the energetic Zn ionic projectile. The classical Bohr–Lindhard model was used for describing recombination, while quantum mechanical models were also introduced for scaling the L to K cross-section ratios. It was found that even for a hydrogen-like carbon target, the effect of the missing five bound electrons brings about an increase of only 0.6 charge units in the equilibrium charge state as compared to the cold target value of 23. A collisional radiative calculation was employed for analyzing the type of plasma produced in the experimental study. It was found that for the plasma conditions characteristic of this experiment, some fully ionized target plasma atoms should be present. However in order to explain the experimentally observed large increase in the projectile charge state a very dominant component of the fully ionized plasma must comprise the target plasma. A procedure for calculating the dynamic evolvement of the projectile charge state within partially ionized plasma is also presented and applied to the type of plasma encountered in the experiment of Roth et al. (2000). The low temperature and density tail on the back of the target brings about a decrease in the exiting charge state, while the value of the average charge state within the target is dependent on the absolute value of the cross-sections.