This issue of Laser and Particle Beams includes papers presented at the 8th Workshop on Fast Ignition of Fusion Targets, held in Tarragona, Spain, from June 29 to July 1, 2005 as part of the 32nd Conference on Plasma Physics organized by the European Physical Society.

Since 2003, the journal of Laser and Particle Beams no longer publishes conference proceedings. Even of those conferences where the topics are very closely related to the research fields discussed in this journal. Authors are instead encouraged to submit a regular paper dealing with the topic presented during a conference. The advantage for authors is that there is no page limit as long as the paper passes the peer review process. The discussion of the presented research during the conference helps reviewers to evaluate the quality of the paper and this usually leads to a speedy publication process. Every year in June, the ISI Web of Knowledge releases the Journal Citation Reports. The publication policy adopted by the Laser and Particle Beams editorial board was obviously quite successful since we experienced a substantial increase in the impact factor and in the immediacy index. Thus the Journal Citation Report lists Laser and Particle Beams now as a leading journal in the field of applied physics. This is an opportunity to thank authors for their high quality contributions to this journal. The publisher and the editorial board will try to continue to improve the service to readers and authors during the upcoming years.

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 primary goal of Laser and Particle Beams as part of the Cambridge University Press is the dissemination of knowledge in our research field. How effective we are in this respect is not easy to determine. But the impact factor published annually in June by Thomson ISI® 2005 Journal Citation Reports (JCR), gives at least an indication and a method to compare other journals in the field. In this respect, Laser and Particle Beams is a journal with a very high ranking in the field of applied physics, but it also compares very well to journals in other field of physics. The impact factor of a journal gives an account of how often an average paper in the journal is referred to, in a two year time span after publication. The current impact factor of 2.59 is based on an evaluation conducted in 2005 of Laser and Particle Beams publications of 2003 and 2004. During the evaluation period (2005), Laser and Particle Beams publications were cited about 1000 times. The topics that attracted most attention were Fast Ignition (Deutsch, 2004; Mulser & Schneider, 2004a; Hora, 2004; Mulser & Bauer, 2004b), Inertial Fusion Targets (Borisenko et al., 2003), and Ion and Electron Acceleration in laser plasma and Ultrashort Pulses (Shorokhov & Pukhov, 2004; Osman et al., 2004; Malka & Fritzler, 2004; Limpouch et al., 2004; Pegoraro et al., 2004). However, the editorial boards of Laser and Particle Beams strongly encourage authors to submit their results in High Energy Density Physics, the emerging field of Warm Dense Matter, Pulsed Power and Accelerator Physics and Technology.

The chlorine Heα radiation of polyvinyl chloride (PVC) was investigated with respect to X-ray scattering experiments on dense plasmas. The X-ray source was a laser-produced plasma that was observed with a highly reflective highly oriented pyrolytic graphite (HOPG) crystal spectrometer as it is used in current x-ray scattering experiments on dense plasmas. The underlying dielectronic satellites of Heα cannot be resolved, therefore the plasma was observed at the same time with a focusing spectrometer with spatial resolution. To reconstruct the spectrum a simple model to calculate the spectral line emission based on dielectronic recombination and inner shell excitation of helium- and lithium-like ions was used. The analysis shows that chlorine dielectronic satellite emission is intense compared to Heα in laser-produced chlorine plasmas with a temperature of 300 eV in this wavelength range of Δλ = 0.07 Å (ΔE = 43 eV). The method proposed in this paper allows deducing experimentally the role of the underlying dielectronic satellites in the scatter spectrum measured with a HOPG crystal spectrometer. It is shown that the dielectronic satellites can be neglected when the scattering is measured with low spectral resolution in the non-collective regime. They are of major importance in the collective scatter regime where a high spectral resolution is necessary.

Peculiarities of the technique of the laser-induced film transfer (LIFT) are investigated. Possible mechanisms of tearing-off and transference of the films from the donor substrate (target) to the acceptor one are investigated. The main fields of LIFT applications are considered. One of the most interesting directions of LIFT applications—decontamination of radioactive surfaces—is investigated in detail. The main peculiarities and regimes of the processing are defined.

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.

We present a novel experiment for the generation of sculpted pulsed indium atomic beams of regular arrays in one and two-dimensions via rear side ablation of indium by two and four beams interference pattern using second harmonic of high power Nd: YAG laser under high vacuum (10−5 Torr).

The interaction of electromagnetic radiation with plasmas is studied in relativistic four-vector formalism. A gauge and Lorentz invariant ponderomotive four-force is derived from the time dependent nonlinear three-force of Hora (1985). This four-force, due to its Lorentz invariance, contains new magnetic field terms. A new gauge and Lorentz invariant model of the response of plasma to electromagnetic radiation is then devised. An expression for the dispersion relation is obtained from this model. It is then proved that the magnetic permeability of plasma is unity for a general reference frame. This is an important result since it has been previously assumed in many plasma models.

The aim of this paper is to describe the influence of target plasma nuclei on the correlated motion of H2+ protons traversing classical plasma matter. Electronic stopping of the protons pair is treated by means of the dielectric formalism, while nuclear collisions are dealt within the classical dispersion theory through a Monte Carlo method. It is shown that vicinage electronic forces screen Coulomb repulsion between the two protons from H2+ ion decelerating the increase of their relative distance. Vicinage forces also align the interproton vector along the motion direction. However, proton interactions with plasma nuclei mask most of these vicinage effects. These nuclear collisions hide the screening effect produced by the vicinage forces, increasing the proton relative distance even faster than for bare Coulomb repulsion. The interproton vector along motion direction is also misaligned due to nuclear collisions. Nuclear collisions effects are more significant in reducing projectile velocity. In particular, all these effects are studied in a deuterium (D) plasma with temperature Te = 10 eV and electronic density n = 1023 cm−3.

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.

Theoretical studies have been performed on the interaction of short laser pulse with metals. The results of the theoretical model indicate that heat conduction would not be uniform from focal spot or crater at the surface of target metal, when an ultra short laser will interact with the metal. The electromagnetic radiations of laser induce electric field inside the target that is responsible for the induction of current density, which causes electronic heat conduction in the direction of current density. Such an effect is dominant for laser pulse having duration less than of the order of sub-picoseconds. This mode will open a new significant field of study to discuss laser metal interaction for ultra short laser pulses.

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.

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.

Recent experiments of fast electron heating of aluminum foil targets have been analyzed by means of hybrid PIC simulations. A suitable initial angular distribution of fast electrons has been used and the diameter of the fast electron source has been fitted to reproduce with the same simulation parameters the beam divergence, Kα yields and temperatures at the target rear surface measured in the experiments. This results in a consistent description of the fast electron propagation that can be useful in general for simulations of laser-driven fast electron transport in dense media.

An electron-beam accelerator, which consists of a primary storage capacitor system, an air core spiral strip transformer, water Blumlein line of water dielectric, and a field-emission diode, is described. The experimental results show that the diode voltage is more than 400 kV, electron beam current is about 40 kA, and the pulse duration is more than 80 ns. This accelerator is very compact and works stably and reliably.

A ∼500 kV/400 kA/100 ns pulsed power generator (PPG-I) for x-pinch experiments was designed and constructed at Tsinghua University. It is composed of a Marx generator, a combined pulse forming line (PFL), a gas-filled V/N field distortion switch, a transfer line, and a copper-sulphate resistive load for testing. The PPG-I implements a novel design in lines that four pieces of waterline with impedance 5Ω in parallel constitute a combined PFL with 1.25Ω, and incorporate each other by a common self-break V/N switch on a matched 1.25Ω transfer line. At the peak charging voltage of the PFL, the V/N switch breaks down in multi-channel discharge mode, and electric energy is fed into the testing load through the 1.25Ω transfer line. This article presents the design and test of the PPG-I generator.

In the first part, the theoretical model of the stochastic heating effect is presented briefly. Then, a numerical resolution of the Hamilton equations highlights the threshold of the stochastic effect. Finally, Particle-In-Cell (PIC) code simulations results, for experimentally relevant parameters, are presented in order to confirm the acceleration mechanism predicted by the one-particle theoretical model. This paper gives the conditions on the different experimental parameters in order to have an optimization of the stochastic heating.

In order to realize an effective implosion, the beam illumination non-uniformity and implosion non-uniformity must be suppressed to less than a few percent. In this paper, a direct-indirect mixture implosion mode is proposed and discussed in heavy ion beam (HIB) inertial confinement fusion (HIF) in order to release sufficient fusion energy in a robust manner. On the other hand, the HIB illumination non-uniformity depends strongly on a target displacement (dz) in a reactor. In a direct-driven implosion mode dz of ∼20 μm was tolerance and in an indirect-implosion mode dz of ∼100 μm was allowable. In the direct-indirect mixture mode target, a low-density foam layer is inserted, and radiation is confined in the foam layer. In the foam layer the radiation transport is expected in the lateral direction for the HIB illumination non-uniformity smoothing. Two-dimensional implosion simulations are performed and show that the HIB illumination non-uniformity is well smoothed. The simulation results present that a large pellet displacement of ∼300 μm is tolerable in order to obtain sufficient fusion energy in HIF.

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.