Plasmas were generated by 3 ns pulsed lasers at 1064 nm wavelength using intensities of about 1010 W/cm2 irradiating solid targets with a different composition. The ion emission was investigated with time-of-flight measurements giving information of the ion velocity, charge state generation, and ion energy distribution. Measurements use a coil to generate a magnetic field suitable to deflect ions toward a Faraday cup and/or a secondary electron multiplier.

Ion acceleration of the order of hundred eV per charge state, plasma temperature of the order of tens eV, charge states up to about 4+, and Boltzmann energy distributions were obtained in carbon, aluminum, and copper targets.

The presented results represent useful plasma characterization methods for many applications such as the new generation of laser ion sources, pulsed laser deposition techniques, and post ion acceleration systems.

Generation of collimated proton beams by linearly and circularly polarized (CP) lasers from magnetized near-critical plasmas has been investigated with the help of three-dimensional (3D) particle-in-cell (PIC) simulations. Due to cyclotron effects, the transverse proton momentum gets significantly reduced in the presence of an axial magnetic field which leads to an enhancement in collimation. Collimation is observed to be highest in case of a linearly polarized (LP) laser in the presence of magnetic field. However, protons accelerated by a right CP laser in the presence of magnetic field are not only highly collimated but are also more energetic than those accelerated by the LP laser. Although, the presence of an axial magnetic field enhances the collimation by reducing the transverse proton momentum, the maximum proton energy gets reduced since the transverse proton momentum has a significant contribution towards proton energy.

The Weibel instability driven by temperature anisotropy is investigated in a two-dimensional (2D) particle-in-cell simulation in non-extensive statistics in the relativistic regime. In order to begin the simulation, we introduced a new 2D anisotropic distribution function in the context of non-extensive statistics. The heavy ions considered to be immobile and form the neutralizing background. The numerical results show that non-extensive parameter q plays an important role on the magnetic field saturation time, the time of reduction temperature anisotropy, evolution time to the quasi-stationary state, and the peak energy density of magnetic field. We observe that the instability saturation time increases by increasing the non-extensive parameter q. It is shown that structures with superthermal electrons (q < 1) could generate strong magnetic fields during plasma thermalization. The simulation results agree with the previous simulations for an anisotropic Maxwellian plasma (q = 1).

In this work, the stopping power of a partially ionized helium plasma due to its free and bound electrons is analyzed for an electron temperature and density in which local thermal equilibrium (LTE) or non-local thermal equilibrium (NLTE) regimes can be possible. In particular by means of collisional-radiative models, the average ionization of the plasma as well as the abundances of different helium species (HeI, HeII, and HeIII) are analyzed in both LTE and NLTE thermodynamic states. The influence of this ionization and of the different ion abundances on the stopping power of the helium plasma is shown to be quite significant. Finally, our theoretical model is compared with experimental results on slowing down of swift argon ions in helium plasma.

We have analyzed the effects of the wiggler error due to the electron beam's emittance, energy spreads, and higher-order modes in a free-electron laser (FEL) oscillator by using two electron beams of different energies based on the proposed FEL facility which is operated at a far-infrared and infrared regions. The three-dimensional (3D) effects in a FEL oscillator due to the wiggler error were calculated and an evaluation of the effect of the beam's emittance and energy spread was performed for the case of the coupled two-beam oscillator for phase shift errors and wiggler errors. The mode construction was studied on the higher-order modes of the wiggler for the various wiggler error parameters for FEL performance which is required for the high-quality electron beam. The radiation intensity at the fundamental mode was calculated for the rms phase shake in wiggler errors with sinus type, constant type, and parabolic type in the two-beam oscillator system using the 3D calculations. The results are compared with those of the fundamental modes without wiggler errors.

In this paper, we present the application of partially spatially coherent extreme ultraviolet (EUV) radiation from xenon plasma from a laser-plasma source, based on a double stream gas puff target, in coherent imaging. The radiation at the wavelength of 13.5 ± 0.5 nm was employed to record Gabor-type holograms. An iterative algorithm, based on a phase retrieval technique, was developed and used to remove the twin image from the reconstructed EUV image of test objects. Using partially coherent radiation from a compact, laser-plasma source based on a double stream gas puff target, which is intrinsically incoherent, a Gabor EUV holography was successfully demonstrated.

Inertial Confinement Fusion is a promising option to provide massive, clean, and affordable energy for mankind in the future. The present status of research and development is hindered by hydrodynamical instabilities occurring at the intense compression of the target fuel by energetic laser beams. A recent patent combines advances in two fields: Detonations in relativistic fluid dynamics (RFD) and radiative energy deposition by plasmonic nano-shells. The initial compression of the target pellet can be decreased, not to reach the Rayleigh–Taylor or other instabilities, and rapid volume ignition can be achieved by a final and more energetic laser pulse, which can be as short as the penetration time of the light across the pellet. The reflectivity of the target can be made negligible as in the present direct drive and indirect drive experiments, and the absorptivity can be increased by one or two orders of magnitude by plasmonic nano-shells embedded in the target fuel. Thus, higher ignition temperature and radiation dominated dynamics can be achieved with the limited initial compression. Here, we propose that a short final light pulse can heat the target so that most of the interior will reach the ignition temperature simultaneously based on the results of RFD. This makes the development of any kind of instability impossible, which would prevent complete ignition of the target.

In this work, extreme ultraviolet (EUV) emission, from EUV induced, low-temperature microplasmas, were investigated. To perform temporal measurements of the EUV pulses of low intensity, in a medium vacuum, under the pressure of the order of 0.1–0.01 mbar a special detection system was prepared. The system was based on an EUV collector and a semiconductor detector, sensitive for the EUV photons. The collector consisted of two identical grazing incidence, paraboloidal mirrors, and allowed to focus a part of the radiation emitted from the microplasma onto the detector surface. An absorption filter, mounted between the collector and the detector, allowed for selection of an interesting wavelength range. Plasmas were created by irradiation of small portions of gases, injected into the vacuum chamber, using a laser produced plasma EUV source. Three gases were used for the EUV induced plasma formation: neon, krypton, and xenon. Low-temperature plasmas, created in these gases, contained multiply charged ions, emitting radiation in similar wavelength ranges. Two detectors, AXUV20HS1 and AXUVHS5, were used for the measurements. It was shown that differences between the corresponding signal profiles, obtained using both detectors, were not very significant. Moreover, it was demonstrated that the duration of the EUV emission from plasmas, created in different gases, were comparable with the duration of the driving EUV pulse. The longest EUV emission was observed for Kr plasmas, approximately 1.5 times the full width half maximum of the driving EUV pulse.

Kinetic modeling of laser-ion beam generation from the “break-out afterburner” (BOA) has been modeled for several deuteron-rich solid-density target foils. Modeling the transport of these beams in a beryllium converter shows as much as a fourfold increase in neutron yield over the present state of the art through the use of alternative target materials. Additionally, species-separation dynamics during the BOA can be exploited to control the hardness of the neutron spectra, of interest for, for example, enhancing penetrability in shielded material in active neutron interrogation settings.

The paper presents an investigation on self-focusing of cosh-Gaussian (ChG) laser beam in a relativistic–ponderomotive non-uniform plasma. It is observed numerically that the selection of decentered parameter and initial beam radius determines the focusing/defocusing of ChG laser beam. For given value of these parameters, the plasma density ramp of suitable length can avoid defocusing and enhance focusing effect significantly. Focusing length and extent of focusing may also be controlled by varying slope of the ramp density. A comparison with Gaussian beam has also been attempted for optimized set of parameters. The results establish that ChG beam focuses earlier and sharper relative to Gaussian beam. We have setup the non-linear differential equation for the beam width parameter using Wentzel–Kramers–Brillouin and paraxial ray approximation and solved it numerically using Runge–Kutta method.

The experimental study of damage to tungsten (W), molybdenum (Mo), and silicon carbide (SiC) surfaces induced by focused extreme ultraviolet laser radiation (λ ~ 47 nm/~1.5 ns/21–40 µJ) is presented. It was found that W and Mo behaved similarly: during the first shot, the damaged area is covered by melted and re-solidified material, in which circular holes appear – residua of just opened pores/bubbles, from which pressurized gas/vapors escaped. Next cracks and ruptures appear and the W has a tendency to delaminate its surface layer. Contrary, single-crystalline SiC has negligible porosity and sublimates; therefore, no escape of “pressurized” gas and no accompanying effects take place. Moreover, SiC at sublimating temperature decomposes to elements; therefore, the smooth crater morphology can be related to local laser energy density above ablation threshold. When more shots are accumulated, in all three investigated materials, the crater depth increases non-linearly with number of these shots. The surface morphology was investigated by an atomic force microscope, the surface structure was imaged by a scanning electron microscope (SEM), and the structure below the surface was visualized by SEM directed into a trench that is milled by focused ion beam. Additionally, structural changes in SiC were revealed by Raman spectroscopy.

Transverse stimulated Raman scattering (TSRS) is strongly generated in the third-harmonic-generation crystal potassium dihydrogen phosphate (KDP) and can even damage the KDP crystal in inertial confinement fusion drivers. In this work, a method to suppress TSRS is proposed in which the polarization control plate (PCP) is moved to a new position in the existing optical path. The proposed method can suppress TSRS significantly and doubles the laser threshold intensity in KDP crystal when the order of the PCP is 16. This result is attributed to the reduction of the gain length for the Stokes radiation. The proposed method may also be used to suppress other nonlinear effects, including transverse stimulated Brillouin scattering in large-aperture optical components.

The paper presents experimental and theoretical research data on the generation, transport, and extraction of a large cross-section (750 × 150 mm2) electron beam into the air through a thin metal foil in an accelerator with a mesh plasma cathode on the bases of a low-pressure arc and with a multi-aperture two-electrode electron-optical system. When the burning conditions of the arc discharge, responsible for the generation of the emission plasma, is changed, the characteristics of this plasma were investigated, including under the conditions of the selection of electrons from it. Our experiments show that at an accelerating voltage of 200 kV, current in the accelerating gap of up to 30 A, and full width at half maximum of up to 100 µm, the average extracted power is ≈4 kW and the extracted beam current is ≈85% from the common current into the accelerating gap. Our numerical estimates give a good correlation between the arc and emission plasma parameters depending on the electrode configuration in the discharge system and on the mechanism of electron beam generation. Analysis of the emission plasma parameters under different arc conditions and of the mechanisms responsible for the beam energy loss suggests that most of the energy in the accelerator is lost at the support grid and at the output foil due to defocusing of the beam and partial electron reflection from the foil. Other mechanisms that decrease the extracted beam energy are discussed.

Collisionless shocks have been the subject on many studies in recent years, due to their ability to accelerate particles. In order to do so, a shock must fulfill three criteria. First, it must be strong enough to accelerate particles efficiently. Second, both the upstream and the downstream must be collisionless. Third, the shock front must be surrounded by electromagnetic turbulence capable of scattering particles back and forth. We here consider the encounter of two identical plasma shells with initial density, temperature, and velocity n0, T0, v0, respectively. We translate the three criteria to the corresponding requirements on these parameters. A non-trivial map of the allowed region for particle acceleration emerges in the (n0, T0, v0) phase space, especially at low velocities or high densities. We first assess the case of pair plasma shells, before we turn to electrons/protons.

Detailed knowledge of dissociation behavior and dissociation products is necessary to understand the stability, sensitivity, and the reactive mechanism of explosives under laser initiation. A time-of-flight mass spectrometer was utilized to detect the transient products of 1,1-diamino-2,2-dinitroethylene (FOX-7) produced under 532 nm pulse laser ablation, the possible attribution of intermediate ion fragments were confirmed. The laser fluence threshold for detectable fragments is about 3.6 J/cm2. The peak intensities of main ions (CN, CNO/C2H4N, NO2, C2N2O, HCN, C2NH2, etc.) increase with the increasing of laser fluence, and reach the maximum at 11.5 J/cm2. Moreover, time-depend changes of ion intensity indicate that the type and degree of reactions are different in different periods. According to the molecular structure of FOX-7 and the intermediate ions, the laser-induced dissociation mechanisms were proposed to illustrate the cause of the fragments which might throw some light on the laser initiation of FOX-7.

The parameters of X-ray radiation and runaway electron beams (RAEBs) generated at long-pulse discharges in atmospheric-pressure air were investigated. In the experiments, high-voltage pulses with the rise times of 500 and 50 ns were applied to an interelectrode gap. The gap geometry provided non-uniform distribution of the electric field strength. It was founded that at the voltage pulse rise time of 500 ns and the maximum breakdown voltage Um for 1 cm-length gap, a duration [full width at half maximum (FWHM)] of a RAEB current pulse shrinks to 0.1 ns. A decrease in the breakdown voltage under conditions of a diffuse discharge leads to an increase in the FWHM duration of the electron beam current pulse up to several nanoseconds. It was shown that when the rise time of the voltage pulse is of 500 ns and the diffuse discharge occurs in the gap, the FWHM duration of the X-ray radiation pulse can reach ≈100 ns. It was established that at a pulse-periodic diffuse discharge fed by high-voltage pulses with the rise time of 50 ns, an energy of X-ray quanta and their number increase with increasing breakdown voltage. Wherein the parameter Um/pd is saved.

Three types of multilayer flyer energy conversion elements (MFECEs) through integrating different laser pulse absorption/ablation layer of nano-film materials into a laser-driven flyer plates between thermal barrier of alumina and transparent substrate have been investigated in this study. The relationships among the velocity of flyer plates, initiation performance of hexanitrostilbene (HNS-IV), and initiation energy were analyzed, comparing with single-layer Al flyer plate. The photonics Doppler velocimetry and James criterion were utilized in the experiments to characterize the velocity of flyer plates and shock initiation of laser-driven flyer detonator, respectively. The surface reflectivity measurements of the Al, C/Al and Mg/Al layers were performed using laser reflectivity. HNS-IV without initiation was analyzed by scanning electron microscope and energy dispersive spectrometer. Caused by aluminum/alumina/aluminum (Al/Al2O3/Al) flyer plate, the residual fragments were found in the pit on the surface of charge. The results obtained were shows that three types of multilayer flyer plates can initiate HNS-IV successfully under the lower laser pulse energy, although all four kinds of flyer plates have successfully initiated HNS-IV with laser pulse energy in the range of 53.80–166.80 mJ. Changing the ablation layer structure and adding thermal insulation layer to the multilayer flyer plates, reduces the shock initiation laser pulse energy of HNS-IV to 53.80 mJ. The laser-driven flyer detonator has significant advantages in providing safety and reliability, especially in a strong electromagnetic environment. The MFECEs of laser-driven flyer detonator exhibited a high level of integration and proved to have promoted laser-driven energy coupling rate, which can significantly be used to improve the performance of the laser-driven flyer detonator in military and civilian applications.

High-energy electron radiography (HEER) has been proposed for time-resolved imaging of materials, high-energy density matter, and for inertial confinement fusion. The areal-density resolution, determined by the image intensity information is critical for these types of diagnostics. Preliminary experimental studies for different materials with the same thickness and the same areal-density target have been imaged and analyzed. Although there are some discrepancies between experimental and theory analysis, the results show that the density distribution can indeed be attained from HEER. The reason for the discrepancies has been investigated and indicates the importance of the uniformity in the transverse distribution beam illuminating the target. Furthermore, the method for generating a uniform transverse distribution beam using octupole magnets was studied and verified by simulations. The simulations also confirm that the octupole field does not affect the angle-position correlation in the center part beam, a critical requirement for the imaging lens. A more practical method for HEER using collimators and octupoles for generating more uniform beams is also described. Detailed experimental results and simulation studies are presented in this paper.

Energy gain of electron beams in bubble regime of the laser wakefield accelerator can be optimized by improving the acceleration length, radial accelerating and focusing force, number of monoenergetic electrons trapped inside the bubble, and increasing dephasing length. In order to enlarge the dephasing length, the phase velocity of the plasma wave can be increased by optimizing the plasma density profile. We report the estimation of dephasing length using plasma density distribution with the flat and linear-upward profile using two-dimensional particle-in-cell simulations. The size of wakefield bubble depends on the plasma density. With a positive plasma density gradient, the size of bubble decreases. The front and trail part of wake bubble will have different phase velocity in plasma density gradient region. After density transition in constant density region, the bubble elongates and the velocity of the back part of the bubble increases so that the accelerated electron phase synchronizes with the phase of the plasma wave. In a result, the electron acceleration length enhances to improve the beam quality.

Laser beat wave heating of magnetized plasma via electron cyclotron damping is proposed and analyzed. A plasma density ripple is presumed to exist across the magnetic field. Two collinear lasers propagating along the magnetic field exert a beat frequency ponderomotive force on electrons, driving a large amplitude Bernstein quasi-mode which suffers cyclotron damping on electrons. Finite Larmor radius effects play an important role in the heating. Electron temperature initially rises linearly with time. As the temperature rises cyclotron damping becomes stronger and temperature rises rapidly. The process, however, requires ripple wavelength shorter than the wavelength of the beat wave.