In this work, a laser-produced plasma source was used to create xenon (Xe) photoionized plasmas. An extreme ultraviolet (EUV) radiation beam was focused onto a gas stream, injected into a vacuum chamber synchronously with the EUV pulse. Energies of photons exceeding 100 eV allowed for inner-shell ionization of Xe atoms. Creation of N-shell vacancies resulted in N-shell fluorescence and was followed by multiple ionization. Time-integrated EUV spectra, corresponding to excited states in Xe II–V ions, were recorded. Several emission lines detected in the 39–65 nm wavelength range were not reported earlier. They were not identified due to lack of a corresponding information in published databases. Except spectral measurements in the EUV range, time resolved ultraviolet and visible spectra, originating from Xe II and III ions, were recorded. For spectral lines, corresponding to radiative transitions in Xe II ions, electron temperature was calculated based on a Boltzmann plot method. Based on this method the temperature was measured for different time delays according to the driving EUV pulses.

Dynamics and organization of laser-generated three-dimensional (3D) Richtmyer–Meshkov (RMI) and Rayleigh–Taylor instabilities (RMI and RTI) on metal target in the semiconfined configuration are different in the central region (CR) (Lugomer, 2016), near central region (NCR) (Lugomer, 2017) and the near periphery region (NPR) of the Gaussian-like spot. The RMI/RTI in the NPR evolve from the shock and series of reshocks associated with lateral expansion and increase of the vapor density, decrease of the Atwood number and momentum transfer. Scanning electron micrographs show irregular (chaotic) web of the base-plane walls, and mushroom spikes on its nodal points with disturbed two-dimensional (2D) lattice organization. Lattice disturbance is caused by the incoherent wavy motion of background fluid due to fast reshocks, which after series of reflections change their strength and direction. Reconstruction of the disturbed lattice reveals rectangular lattice of mushroom spikes with p2mm symmetry. The splitting (bifurcation) of mushroom diameter distribution on the large and small mushroom spikes increases with radial distance from the center of Gaussian-like spot. Dynamics of their evolution is represented by the orbits or stable periods in 2D phase space. The constant mushroom diameter – stable circulation or the stable periodic orbits – are the limit cycles between the unstable spiral orbits. Those with increasing periods represent supercritical Hopf bifurcation, while those leading to decrease and disappearance represent subcritical Hopf bifurcation. The empirical models of RMI, although predict dependence of the growth rate on radial distance (distance the reshocks travel to reach the interface), show many limitations. More appropriate interpretation of the simultaneous growth and lattice organization of small and large spikes give the fundamental model based on the interference of the perturbation modes depending on their amplitude, relative phase, and the symmetry. The late-time instability in the base-plane evolves into line solitons, vortex filaments and wave–vortex structures with chaotic rather than stochastic features.

The interaction of femtosecond laser with initially cold solid metallic targets (Al, Au, Cu, Mo, Ni) was investigated in a wide range of laser intensity with focus on the laser energy absorption efficiency. Our developed simulation code (FEMTO-2D) is based on two-temperature model in two-dimensional configuration, where the temperature-dependent optical and thermodynamic properties of the target material were considered. The role of the collisional processes in the ultrashort pulse laser–matter interaction has been carefully analyzed throughout the process of material transition from the cold solid state into the dense plasma state during the pulse. We have compared the simulation predictions of the laser pulse absorption with temperature-dependent reflectivity and optical penetration depth to the case of constant optical parameters. By considering the effect of the temporal and spatial (radial) distribution of the laser intensity on the light absorption efficiency, we obtained a good agreement between the simulated results and available experimental data. The appropriate model for temperature-dependent optical parameters defining the laser absorption efficiency will allow more accurate simulation of the target thermal response in the applications where it is critical, such as prediction of the material damage threshold, laser ablation threshold, and the ablation profile.

A linearly polarized laser pulse has been employed as a wiggler in a free-electron laser (FEL) in the presence of a plasma background for generating short wavelength radiation down to the extreme ultraviolet ray and X-ray spectral regions. Introducing plasma background in the FEL interaction region would lessen the beam energy requirement and also enhance both the beam current and the electron-bunching process. This configuration affords the possibility of scaling the device to more compact FELs and would have a higher tunability by changing the plasma density and the temperature of the electron beam. Electron trajectories have been analyzed using single-particle dynamics. The effect of plasma density on electron orbits has been investigated. A polynomial dispersion relation considering longitudinal thermal motion has been derived, by employing perturbation analysis. Numerical studies indicate that by increasing plasma density, the growth rate for groups I and II decreases, while the growth rate for group III increases. In addition, the effect of beam temperature and cyclotron frequency on the growth rate has been discussed. It has been found that by increasing the thermal velocity of the electron beam, the growth rate for groups I and III trivially decreases, while it increases for group II orbits. Besides, an increase in cyclotron frequency cause growth enhancement for group I orbits, while it present a growth decrement for group II and III orbits.

The mathematical model for the propagation of intense laser pulse in a plasma having Gaussian profile is investigated. The model has been formulated considering that the relativistic–ponderomotive nonlinearity dominates over other nonlinearities in the plasma. Model equation for self-compression and self-focusing properties of the laser pulse has been set up and solved by both semi-analytical and numerical methods. The result indicates that due to the effect of group velocity dispersion, diffraction of the laser pulse and the nonlinearity of medium, the pulse width parameter as well as beam width parameter of pulse gets focused at a different normalized distance, and hence the normalized intensity is also deferred at those points. Numerical simulation shows an oscillatory behavior of intensity during propagation in the plasma either having minimum beam radius (r 0) or having minimum pulse duration (t 0) depending on the normalized distance.

The possibilities of electron acceleration by ponderomotive force of a circularly polarized laser pulse in magnetized quantum plasma have been explored. The basic mechanism involves acceleration of electron by the axial gradient in the ponderomotive potential of the laser. The quantum effects have been taken into account for a high-density plasma. The ponderomotive force of the laser is resonantly enhanced when Doppler up-shifted laser frequency equals the cyclotron frequency.

The paper presents the result of investigation gas emission from anode polymer coating of applied – Br magnetically insulated ion diode. The gas pressure value for any polymer type was determined. The investigations of the pressure variation were carried out during the pulse repetition rate of ion beam from 1 to 4 pps. The residual gas pressure value variation inside the vacuum chamber influenced on the ion beam parameters. The mass content of ion beam injected into the transition area did not depend on the residual gas pressure value. The breakdown of residual gas pressure by eddy electric field of magnetic coils was investigated.

A novel method to generate shock waves in small tubes is demonstrated. A femtosecond laser is applied to generate an optical breakdown an aluminum film as target. Due to the sudden appearance of this non-equilibrium state of the target, a shock wave is induced. The shock wave is further driven by the expanding high-pressure plasma (up to 10 Mbar), which serves as a quasi-piston, until the plasma recombines. The shock wave then propagates further into a glass capillary (different square capillaries with hydraulic diameter D down to 50 µm are applied). Shock wave propagation is investigated by laser interferometry. Although the plasma is an unsteady driver, due to the geometrical confinement of the capillaries, rather strong micro shocks can still propagate as far as 35 times D. In addition to the experiments, the initial conditions of this novel method are investigated by hydrocode simulations using MULTI-fs.

Production of high dynamic pressure using a strong shock wave is a topic of high relevance for high-energy-density physics, inertial confinement fusion, and materials science. Although the pressures in the multi-Mbar range can be produced by the shocks generated with a large variety of methods, the higher pressures, in the sub-Gbar or Gbar range, are achievable only with nuclear explosions or laser-driven shocks. However, the laser-to-shock energy conversion efficiency in the laser-based methods currently applied is low and, as a result, multi-kJ multi-beam lasers have to be used to produce such extremely high pressures. In this paper, the generation of high-pressure shocks in the newly proposed collider in which the projectile impacting a solid target is driven by the laser-induced cavity pressure acceleration (LICPA) mechanism is investigated using two-dimensional hydrodynamic simulations. A special attention is paid to the dependence of shock parameters and the laser-to-shock energy conversion efficiency on the impacted target material and the laser driver energy. It has been found that both in case of low-density and high-density solid targets, the shock pressures in the sub-Gbar range can be produced in the LICPA-based collider with the laser energy of only a few hundreds of joules, and the laser-to-shock energy conversion efficiency can reach values of 10–20%, by an order of magnitude higher than the conversion efficiencies achieved with other laser-based methods used so far.

Plasma focus is one type of ion source with energy up to few MeV. While some efforts have been made to understand the physics of ion beam acceleration in plasma focus devices (PFD), an acceptable clarification does not exist yet. In this work, the procedure of ions) electrons) acceleration in PFDs to the MeV energy is investigated theoretically. Moreover, the trajectory of electrons (ions) and their angular distribution are studied. The simulations are carried out by COMSOL Multiphysics version 5.2 for a 4.5 kJ Mather type PFD. The results of simulations and calculations show that trapped ions in the negative potential of electrons, their movement toward the top of the anode and the drift motion due to electrical and magnetic fields near the top of the anode are the main causes of high energy electrons (ions) production and acceleration.

A laser ion source (LIS) is a promising candidate as an ion source for heavy-ion inertial fusion (HIF), where a pulsed ultra-intense and low-charged heavy ion beam is required. It is a key development for a LIS to transport laser-produced plasma with a magnetic field to achieve a high-current beam. The effect of a tapered magnetic field on laser-produced plasma is demonstrated by comparing the results with a straight solenoid magnet. The magnetic field of interest is a wider aperture on a target side and narrower aperture on an extraction side. Based on the experimentally obtained results, the performance of a scaled LIS for HIF was estimated.

Laser-induced damage threshold (LIDT) is an important parameter used to describe the resistance of optical thin films to laser damage. The service life and cost of optical systems depend on the LIDT of the film. Thus, the precision with which the film's LIDT can be measured impacts how well the service life and cost of the system can be predicted. Therefore, it is important to find a precise approach to diagnose a film's laser-induced damage. In this paper, characteristics of the peak sound pressure of laser-induced plasma shock waves from thin films have been systematically investigated experimentally. We found that the peak sound pressure decays rapidly with propagation distance during air transmission. Based on a theoretical analysis of the relationship between the peak sound pressure and the laser damage to a film, we propose a method for diagnosing laser damage using the peak sound pressure of a thin film's shock wave. Our results show that this method can simplify implementation, which will provide a new method with which to diagnose laser damage to thin films.

The energy spectra of protons generated by ultra-intense (1020 W cm−2) laser interactions with a preformed plasma of scale length measured by shadowgraphy are presented. The effects of the preformed plasma on the proton beam temperature and the number of protons are evaluated. Two-dimensional EPOCH particle-in-cell code simulations of the proton spectra are found to be in agreement with measurements over a range of experimental parameters.

K α X-ray sources generated from the interaction of ultra-short laser pulses with solids are compact and low-cost source of ultra-short quasi-monochromatic X-rays compared with synchrotron radiation source. Development of collimated ultra-short K α X-ray source by the interaction of 45 fs Ti:sapphire laser pulse with Cu wire target is presented in this paper. A study of the K α source with laser parameters such as energy and pulse duration was carried out. The observed K α X-ray photon flux was ~2.7 × 108 photons/shot at the laser intensity of ~2.8 × 1017 W cm−2. A model was developed to analyze the observed results. The K α radiation was coupled to a polycapillary collimator to generate a collimated low divergence (0.8 mrad) X-ray beam. Such sources are useful for time-resolved X-ray diffraction and imaging studies.

The evolution of the spot size and amplitude of a circularly polarized laser beam propagating in a plasma channel embedded in an obliquely applied magnetic field has been investigated. The wave equation describing the evolution of the radiation field is set up and a variational technique is used to obtain the equations governing the evolution of the spot size and amplitude. Numerical methods are used to analyze the evolution of the laser beam spot size and amplitude. It is seen that the amplitudes of the two transverse components of the electric field of the laser beam evolve differently, since they are driven by unequal current densities. This leads to the conversion of a circularly polarized laser beam into an elliptically polarized beam, under appropriate conditions.

In this paper, the electrons energy spectrum produced by stochastic acceleration in the interaction of an intense laser pulse with the underdense plasma is described by employing the fully kinetic 1D-3 V particle-in-cell simulation. In this way, two finite laser pulses with the same length 200 fs and with two different rise times 30 and 60 fs are typically selected. It is shown that the maximum energy of electrons in the laser pulse with the short rise time (30 fs) is about eight times greater than the maximum energy of the electrons with the long rise time (60 fs). Furthermore, unlike the pulse with the short rise time, the shape of energy spectrum and the electrons temperature in the long rise time laser pulse are approximately unchanged over the time. These results originated from the fact that in the case of long rise time laser pulse, all electrons are accelerated by the one chaotic mechanism because of the scattered fields generated in the plasma, but in the case of short rise time laser pulse, three different mechanisms accelerate the electrons: first, the stochastic acceleration because of the nonlinear wave breaking via plasma-vacuum boundary effect; second, the stochastic acceleration initiated by the wave breaking; and third, the direct laser acceleration of the released electrons.

A compact nanosecond pulsed X-ray source is described. The X-ray source consists of two important subassemblies: a high-voltage pulse generator and an X-ray diode. The high-voltage pulse generator is designed based on the principle of triple resonance circuit producing a high-voltage pulse across the X-ray diode with amplitude of up to 500 kV. The X-ray diode is a sealed transmission target X-ray tube. Its cathode is comb structure formed from thin tungsten sheets with thickness 50 µm, while its target is made of 100 µm titanium film. The X-ray dose at a distance of 20 cm from the diode is 20 mR per pulse, while the diode voltage is 512 kV. In the case, the full-width at half-maximum of the X-ray pulse is ~5 ns.

The energy spectra of a sparse ensemble of electrons scattered by relativistically intense laser pulses are studied numerically by solving the relativistic Newton equations with the Lorentz force generated by an electromagnetic envelope in vacuum. The expressions for the envelope describe focused optical fields, include significant short-pulse corrections, and afford the representation of laser radiation with various types of transverse distributions of amplitude. The dependence of the character of the electron energy spectra on the type of the transverse distribution of laser amplitude is explored. For Gaussian pulses, the electron energy spectra within specific angular ranges tend to either include a relativistic maximum while being localized around it or to have the shapes of evanescent distributions dominated by the cold component. Conversely, the energy spectra of electrons ejected into certain angular ranges by laser pulses having first-order Laguerre profiles combine pronounced cold components and structured strongly relativistic features. The presumed laser pulse transverse structure and the shapes of the calculated electron energy spectra for first-order Laguerre amplitude distributions are shown to match, qualitatively, those reported in a recent experimental study by Kalashnikov et al. in 2015, which revealed the electron energy spectra spanning both the sub-relativistic and the markedly relativistic energy domains.

Using reductive perturbation technique, small-amplitude ion-acoustic solitary wave has been investigated in multi-component dense plasma, in which an electron beam propagates along the general streaming motion. The electrons in plasma have the q-exponential distribution. The positive and negative ions follow a regular Maxwellian distribution. It has been found that the positive and negative ion densities as well as the beam concentration have significant effect on the formation and properties of solitary structures. The streaming velocities of corresponding particles also have pronounced effect on the features of the solitons.

It was shown (Faenov et al., 2015b) that the energy of femtosecond laser pulses with relativistic intensity approaching to ~1021 W/cm2 is efficiently converted to X-ray radiation and produces exotic states in solid density plasma periphery. We propose and show by one-dimensional two-temperature hydrodynamic modeling, that applying two such unique ultra-bright X-ray sources with intensities above 1017 W/cm2 – allow to generate shock waves with strength of up to some hundreds Mbar, which could give new opportunities for studies of matter in extreme conditions.