The different physical models, computational methods, and results describing the properties of a plasma produced by an ultrashort laser pulse interacting with a solid target at different laser intensities are presented. The basic issues affecting the laser-plasma interaction are considered, including: the different absorption mechanisms; the formation of a transient, nonequilibrium, asymmetric electron distribution function; the energy losses; the role of instabilities and the ponderomotive force; ion expansion and acceleration; and surface wave propagation along the boundary of the plasma. The article concludes with a discussion of the range of applicability of the different approximations and future perspectives for the field.

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.

Channeling by a train of laser pulses into homogeneous and inhomogeneous plasmas is studied using particle-in-cell simulation. When the pulse duration and the interval between the successive pulses are appropriate, the laser pulse train can channel into the plasma deeper than a single long-pulse laser of similar peak intensity and total energy. The increased penetration distance can be attributed to the repeated actions of the ponderomotive force, the continuous between-pulse channel lengthening by the inertially evacuating ions, and the suppression of laser-driven plasma instabilities by the intermittent laser-energy cut-offs.

We have developed a new soft x-ray spectrometer covering the photon energy range 50–500 eV. It employs a free-standing transmission grating coupled to a microchannelplate detector. The performance of the device was tested by using radiation from a synchrotron with a continuous spectrum. The detector shows a rather flat response over most of the useful spectral range, with an abrupt decrease in the sensitivity at the short-wavelength end. Its simplicity of operation makes the device attractive for such applications as the study of soft x-ray emission from laser-produced plasmas.

This paper presents a scheme of terahertz radiation generation based on beating of two dark hollow laser beams with different frequencies, the same electric field amplitudes, in actual plasma with spatially periodic density that electron–neutral collisions have taken into account. The main feature of considered hollow laser beams is, having the same power at different beam orders. Because of special distribution in beam intensity gradient in dark hollow laser beam, the produced terahertz radiation has special field profile. The effects of laser and plasma parameters on terahertz radiation generation are investigated analytically. It can be deduced that by increasing beating frequency, efficiency of terahertz generation decreases which can be compensated by manipulating density ripple magnitudes and dark-size adjusting parameter. The intensity of the emitted radiations is found to be highly sensitive to the beam order. Based on the results of this paper, optimization of laser and plasma parameters can increase the efficiency of terahertz radiation generation strongly.

A scheme capable of enhancing the energy of monoenergetic protons in high intensity laser-plasma interactions is proposed and demonstrated by two dimensional particle-in-cell simulations. The focusing of laser light pulse and the guiding of surface current via the high Z material cone-shaped substrate increase the temperature of hot electrons, which are responsible for the electrostatic field accelerating protons. Moreover, the sub-micron proton layer coated on the cone-shaped substrate makes the total proton beam experience the same accelerating field, thus the monochromaticity is maintained. Compared to the normal film double layer target, the energy of monoenergetic proton beams can be improved about three times.

Particle-in-cell (PIC) simulation of a two-foil magnetoinsulated vircator is carried out. Evolution of electron phase portrait has been studied. Formation of two regions with a squeezed state of electron beam is observed, separated from each other by an electronic phase vortex. The power of two-foil vircator's microwave generation was calculated. It is demonstrated that in the phase vortex mode, the power of vircator's microwave radiation may excel the outcome power of a usual one-foil vircator by two times. The spectral characteristics of two-foil vircators were studied. It was found that it is necessary to change the energy of electrons for the variation of primary microwave generation frequency.

Laser Wake Field Acceleration of relativistic electron bunches is a promising method to produce a large amount of energetic particles with table top equipment. One of the possible methods to inject particles in the appropriate acceleration phase of the wake behind the pulse takes advantage of the partial longitudinal breaking of the wake crests across a density downramp. In this paper results of 2.5D PIC simulations, showing the production of an electron bunch with reduced energy spread, are reported. Also, a possible method to produce the required plasma density transition by laser explosion of a suitable couple of thin foils is discussed.

This paper reviews the physical phenomena that accompany the emission of electrons and ions from plasma. The development of plasma emission electronics as an independent research field is closely associated with the name of its founder, Professor Kreindel Yu. E. The well-known advantages of plasma electron emitters (plasma cathodes) are the higher emission current density, the pulsed emission capability, and the wider range of residual gas pressures. A peculiar property of the plasma cathode is the possibility of extracting practically all electrons from plasma. The parameters of an ion and electron beam extracted from plasma carry information about the physical processes occurring in the plasma. This makes it possible to invoke emission methods to study the fundamental phenomena that take place in plasma of vacuum arc and low-pressures gas discharges.

In this paper, authors have studied the growing interaction of the rippled laser beam with upper hybrid mode leading to enhanced Raman scattering for collisional plasma. The presence of ripple leads to additional coupling between the rippled laser beam and electrostatic upper hybrid mode via modified background density. Computational results show the focusing of the upper hybrid wave for the chosen set of plasma parameters. With coupling being strong, the excited upper hybrid wave further interacts with rippled laser beam and give rise to enhanced Raman scattering. The significant role of collisional parameter S is also highlighted in the present investigation. An expression for the scattered power is derived and the effect of the externally applied static magnetic field on enhancement of scattered power is observed. We conclude from present analysis that the effect of the increased magnetic field is useful in suppressing the growth of the ripple.

Extensive numerical simulations have been carried out to design a viable solid graphite wheel shaped production target for the super conducting fragment separator experiments (Super-FRS) at the future Facility for Antiprotons and Ion Research (FAIR) using an intense uranium beam. In this study, generation, propagation and decay of deviatoric stress waves induced by the beam in the target, have been investigated. Maximum beam intensities that the target can tolerate using different focal spot sizes that are determined by requirements of good isotope resolution and transmission of the secondary beam through the fragment separator, have been calculated. It has been reported elsewhere that the tensile strength of graphite significantly increases with temperature. To take advantage of this effect, calculations have also been done in which the target is preheated to a higher temperature, that in practice can be achieved, for example, by irradiating the target with a defocused ion beam before the experiments are performed. We report results of a few examples using an initial temperature of 2000 K. This study has shown that employing such a configuration, one may use a solid graphite production target even for the maximum intensity of the uranium beam (5 × 1011 ion per bunch) at the Super-FRS.

The radiation hydrodynamics of material layers for energy conversion of intense ion beams into black body radiation is investigated, both analytically and numerically. Conversion efficiency and hydrodynamic losses are the main topics. The basic scaling relations are derived and compared with computer simulations. Although the analysis is done for slab geometry, a generalization to converters of arbitrary shape and deposition geometry is outlined. The code MINIRA is briefly described. The influence of varying layer density, optical thickness and beam power on radiation emission as well as the effect of Bragg peak deposition are discussed in detail. High conversion efficiencies of more than 50% can be obtained provided that the converter is operated in the radiative regime. For typical beam intensities, this requires low-density layers. Another essential feature is supersonic heat transport which occurs in the radiative regime.

A simple model is presented for the thermodynamic and hydrodynamic behaviour of solid targets heated by intense charged particle beams. The model gives the temperature and pressure generated by the beam and allows a direct comparison with the pressure generated by laser beams. The model is in good agreement with a coupled thermodynamic hydrodynamic computer simulation.

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.

Our recent estimates are that the energy-gains for cryogenic single-shell targets are close to those of similar double-shelled targets. However, the peak-power requirements for single-shell targets are still about a factor of two higher.

Energetic ion beams are produced during the interaction of ultrahigh-intensity, short laser pulses with plasmas. These laser-produced ion beams have important applications ranging from the fast ignition of thermonuclear targets to proton imaging, deep proton lithography, medical physics, and injectors for conventional accelerators. Although the basic physical mechanisms of ion beam generation in the plasma produced by the laser pulse interaction with the target are common to all these applications, each application requires a specific optimization of the ion beam properties, that is, an appropriate choice of the target design and of the laser pulse intensity, shape, and duration.

The design and constructional aspects of a novel pulse power generator for use in dense plasma research presently under construction are presented. The generator consists of two Marx capacitor banks, each of 0.25 μF, 480 kV, and 28.8 kJ. Each Marx generator drives a water transmission line, in which the live electrode is the central conductor. The transmission lines consist of a constant impedance section followed by a multielectrode gas linegap followed by an exponential taper to the load section. The novel feature is the use of an auxiliary exponential line coupled at the load. This line controls both the voltage and the effective impedance at the load section. In addition, by leaving this line circuit open, energy not coupled to the plasma in the initial high-impedance phase may be reflected back and deposited into the discharge, increasing the peak current by 50%. Circuit simulations using a real-time-varying load impedance show that the current pulse rises in an approximately linear way to a maximum of 1.2 MA at 250 ns. The current falls to zero in the following 250 ns. The current waveform may be flattened simply by disconnecting the auxiliary line, giving a rectangular pulse of 350 ns with a maximum value of 950 kA. The overall impedance of the entire system may be adjusted by varying the separation between the conductors. The equivalent source impedance at the load is 0.8 Ω. This low value is by virtue of the auxiliary line, which limits the voltage at the load section and reduces the insulator constraints. We present simulations of the generator under real load conditions. The model also is checked against analytical solutions of exponential line behavior and against other published models of pulse power generators.

Fast ignition of inertial fusion targets driven by quasi-monoenergetic ion beams is investigated by means of numerical simulations. Light and intermediate ions such as lithium, carbon, aluminum and vanadium have been considered. Simulations show that the minimum ignition energies of an ideal configuration of compressed Deuterium-Tritium are almost independent on the ion atomic number. However, they are obtained for increasing ion energies, which scale, approximately, as Z2, where Z is the ion atomic number. Assuming that the ion beam can be focused into 10 µm spots, a new irradiation scheme is proposed to reduce the ignition energies. The combination of intermediate Z ions, such as 5.5 GeV vanadium, and the new irradiation scheme allows a reduction of the number of ions required for ignition by, roughly, three orders of magnitude when compared with the standard proton fast ignition scheme.

In the present research work, the authors have investigated the self-focusing and defocusing of Hermite-cosh-Gaussian laser (HChG) beam in an inhomogeneous rippled density plasmas. By taking the relativistic non-linearity into account, an equation for envelope is set up and solved using Wentzel–Kramers–Brillouin and the paraxial ray approximation. An ordinary non-linear differential equation governing the beam width parameter as a function of propagation distance is set up for different mode structures of the beam. Further, a numerical study of this differential equation is carried for suitable set of plasma and laser parameters. The beam undergoes periodic self-focusing/defocusing due to relativistic non-linearity. We also report the comparison between self-focusing/defocusing of HChG beam in the absence and presence of density ripple. Presence of ripple does not only leads to substantial increase in self-focusing length, but also results in oscillatory character with decreasing f. In a relativistic case, strong oscillatory self-focusing and defocusing is observed. Further, self-focusing is enhanced with increased value of decentered parameter.

A very intense laser field polarizes the virtual electron-positron pairs that populate the vacuum. This provides for a coupling between different modes of the electromagnetic field, giving rise to effects such as scattering of light by light, a refractive index of the vacuum, vacuum birefringence, etc. Given enough energy in a sufficiently small spacetime region, the virtual pairs can become real, which leads to pair production in the intense field under the action of a third agent. These, as well as related effects, are summarized with respect to their orders of magnitude and conditions under which they might become accessible to experiment. Some other processes that are normally mentioned in this context, such as Thomson (Compton) scattering at high intensities, are considered, too, even though they are unrelated to the vacuum structure of quantum electrodynamics.