Effective suppression of transverse stimulated Raman scattering (TSRS) in a large-aperture potassium dihydrogen phosphate (KDP) crystal is an important scientific and technical problem in high-intensity laser research and applications. In this work, a method to suppress TSRS using pulse stacking is proposed. The method suppresses TSRS significantly, with greater numbers of subpulses producing more obvious suppression effects, and the threshold intensity growth rate of the 3ω laser in the KDP crystal reaches up to about 1.9 when the stacked pulse contains four subpulses. This suppression effect is attributed to the fact that the polarization directions of adjacent subpulses are perpendicular to each other. The method can be used to suppress other nonlinear effects, including transverse stimulated Brillouin scattering in large-aperture optical devices and stimulated rotational Raman scattering in long air paths.

Study of even harmonic generation resulting from propagation of whistler pulse in homogeneous high-density quantum plasma immersed in an externally applied magnetic field, using the recently developed quantum hydrodynamic model is presented. The effects of quantum Bohm potential, quantum statistical pressure, and electron spin have been taken into account. The field amplitude of even harmonic of the whistler with respect to fundamental wave and the conversion efficiency for phase-mismatch has been analyzed. The conversion efficiency of harmonic radiation depends on the plasma electron density, magnetic field strength as well as the intensity of whistler pulse. The efficiency increases significantly with an increase in plasma density, magnetic field and whistler wave intensity. Higher conversion efficiency is observed in degenerate plasma for lower values of the static magnetic field as compared with classical plasma.

The generation of high-order harmonics in ultraviolet spectral range by targets of periodic modulation interacting with relativistic, high contrast laser pulse (Iλ2 = 1020 W/cm2 · μm2) was investigated experimentally and numerically. The spectral intensity of the 2nd- and 3rd-order harmonic emission from grating of different periodicities (250, 410, and 480 nm) is presented. The enhancement of the 3rd harmonic order compared with 2nd was observed for a grating of 480 nm periodicity. The experimental results indicate the role of the grating periodicity on the emission efficiency of different higher order harmonics in the UV spectral range. The higher order harmonics are emitted at the grating surface separated from the specular reflection of the laser pulse, due of the interference effects. In addition, 2D numerical PIC simulations demonstrate a complex angular distribution of the higher harmonics (HH) spectral intensity and confirm the strong dependence of the HH efficiency of a specific order on the grating periodicity, as observed experimentally. These special features of the high harmonic emission by periodically modulated targets open the route toward the control of HH spectral composition and of the emission efficiency of the lower order harmonics.

Research results of luminescence spectra of noble gases and Ar–Xe, Ar–Kr, and Kr–Xe mixtures under the excitation by products of nuclear reaction in the core of a stationary nuclear reactor with 0.87 × 1014 n/cm2s thermal neutron flux are described in the article. The emission spectra of noble gases are similar to the obtained spectrum under the excitation by the 40Ar+7 ion beam from the DC-60 accelerator. Bands in spectra of the binary mixtures of noble gases are connected with the radiation on heteronuclear ion molecule transitions. The appearance of the lines of alkali metal atoms at the temperature increase of gas chamber is explained by sputtering of the lithium layer via nuclear reaction products as well as ionized and excited particles of the buffer gas.

The cryogenic system for maintaining a target at a constant temperature in the range 5–25 K after shutting off the pulse tube (PT) cryogenic refrigerator is developed and tested. The temperature stability at the sample is ±2 mK for at least 20 hours. The cryogenic setup consists of cryostat, PT cryocooler, liquid helium vessel, helium gas supply, thermo-radiation shield, thermal resistance. The system provides 0.25 W of cooling power at the target. The appropriate thermal resistance should be used for different temperatures. The designed operation mode is 3 minutes off and 15 minutes on. The deactivation of PT cryocooler allows to achieve the target position stability of 1 micrometer or less during the X-ray characterization. The effect of neutron-shield was estimated using Monte-Carlo simulation.

We study the effect of magnetic field in an implosion process achieved by radiation. A time-varying sinusoidal magnetic field is seen to affect the continuous transition of space-like detonation to time-like detonation at the core of implosion region. The oscillating varying magnetic field has a significant effect in increasing the volume of the time-like detonation of the core of implosion and also modifies the time of the implosion process. This transition can have significant outcome both theoretically and experimentally in the areas of high-energy hadronization of quark–gluon plasma matter and inertial confinement fusion efforts of fuels.

High-intensity electron linacs have severe space-charge effects that lead to the production of beam halo which degrade the beam quality. For a given charge per bunch, hollow beams have a weaker nonlinear space-charge force. In this paper, we have investigated the possibility of using hollow beam to control halo growth in linacs. We simulate the dynamics of such a beam in a 17 MeV radio frequency linac using ASTRA beam dynamics code and show that it experiences a smaller emittance growth as well as reduced beam halo. The results suggest that using a hollow beam, high charge per bunch could be propagated and accelerated in a radio frequency linac.

Irradiation of gases with intense pulses of extreme ultraviolet (EUV) can result in the formation of low-temperature plasmas. During the time of irradiation, various non-thermal processes driven by the EUV photons and photoelectrons take place, leading to the creation of excited states of atoms and ions. Fast relaxation of these states should result in EUV emission within a time comparable to the driving EUV pulse. On the other hand, from our earlier works, a time duration of the emission in an optical range is over an order of magnitude longer. It can be thus expected that the time of EUV emission can be also relatively long. In this work, time-resolved measurements of the EUV emission from low-temperature plasmas induced in He, Ne, and Ar gases were performed. Due to a low intensity of the emitted radiation, a specially prepared detection system, based on an EUV collector and an EUV sensitive photodiode, was employed. In all cases, a time duration of the EUV emission was much longer compared with the driving EUV pulse. Time profiles of the corresponding signals were specific for particular gases. In case of He and Ne plasmas, these time profiles varied with initial densities of gases to be ionized. The corresponding dependence was especially visible in case of plasmas induced in helium. In case of Ar plasmas, such dependence was not revealed.

A fundamental problem for the realization of laser fusion through the implosion of a spherical target is Kidder's E−1/6 law, where E is the energy needed for ignition, proportional to the 6th power of the ratio R/R0, where R0 and R are the initial and final implosion radii, respectively. This law implies that the ignition energy is very sensitive to the ratio R0/R, or vice versa, the ratio R0/R is very insensitive to the energy input, with R0/R limited by the Rayleigh–Taylor instability. According to still classified data of the Centurion–Halite experiment at the Nevada Test Site, ignition would require an energy of ${\rm E}\simeq 50\,{\rm MJ}$, 25 times larger than the 2 MJ laser at the National Ignition Facility (NIF) reported in the New York Times. This means that even a tenfold increase from 2 to 20 MJ would only decrease the R/R0 ratio by an insignificant factor of 10−1/6 ≃ 0.7. To overcome this problem, it is proposed that the spherical target is replaced with a hollowed-out, rapidly rotating, cm-size ferromagnetic target, accelerated by a rotating traveling magnetic wave to a rotational velocity of ~1 km/s, at the limit of its tensile strength. In a rotating reference system, the general theory of relativity predicts the occurrence of negative gravitational field masses in the center of rotation, with their source located in the Coriolis force field. The density of this negative gravitational field mass can be larger than the magnitude of the positive mass density of a neutron star. The repulsive gravitational force causes the centrifugal force. For a magnetized plasma placed in the rapidly spinning, hollowed-out target chamber, this repulsive force can be balanced by the magnetic force generated by thermomagnetic currents of the Nernst effect. Such a configuration does not suffer from the Rayleigh–Taylor instability, but becomes a small magnetohydrodynamic generator, amplifying the magnetic field to values about equal to those of the Nernst effect, axially confining the plasma. By placing the spinning target in the center of a lithium vortex, the fusion neutrons absorbed in the vortex can breed tritium, and at the same time remove heat from the target chamber to sustain the Nernst effect. A hot spot is thereby produced in the target chamber, which launches a thermonuclear burn wave into a cylindrical deuterium–tritium configuration. With the stability of a rapidly rotating target greatly increased, and the range of 10 MeV electrons in the wall of the cm-size ferromagnetic target, an intense 10 MeV relativistic electron beam drawn from a 10 MJ Marx generator should be sufficient to implode the target for thermonuclear ignition.

Two-photon absorption (TPA) of Au-ion irradiated glasses in the femtosecond regime has been analyzed by an open-aperture Z scan technique. Three types of glasses, namely GIL49, BK7, and Glass B were irradiated by using 1700 keV Au+ ion beams. Samples were post-annealed at 600°C for 5 h. Penetration depth and distribution of Au+ ions having 1700 keV energy within glass substrates were estimated by transport of ions in matter (TRIM) simulations. Detailed calculations with full-damage cascades were performed for each sample, taking into account the chemical composition of glass substrates. TRIM results reveal that there is no significant change in ion range, straggling, and ion distribution with the change in the substrate composition. However, Z scan results showed a difference in TPA coefficients for all three glasses. Extent of crosslinking within each of irradiated sample, owing to its chemical composition, may have affected their TPA coefficients.

Laser-induced breakdown spectroscopy has been exploited to investigate the laser-produced lead plasma with and without external magnetic field. Plasma on the lead surface was generated by focusing a beam of a Nd:YAG laser (532 nm). An external magnetic field was applied across the laser-produced plasma; its value was varied from 0.3 to 0.7 T and the time-integrated spectra were captured at different time delays. Maximum enhancement in the neutral and ionic line intensities have been observed at 130 mJ laser energy. The neutral line of Pb at 368.34 nm reveals an enhancement factor of nearly 1.3, 1.6, and 2.3 at 0.3, 0.5, and 0.7 T, whereas the Pb ionic line at 424.49 nm shows enhancement factor of approximately 2.8 and 4.2 at 0.3 and 0.7 T. The magnetic field effects on various plasma parameters such as plasma temperature, electron number density, and emission line intensities have also been investigated. The plasma parameter “β” is found to be <1 in all the experimental conditions which signifies that the enhancement in the signal intensity is due to the plasma confinement. The increase in the emission signal intensity, number density as well as plasma temperature is observed with increasing laser energy and magnetic field. The spatial and temporal behavior reveals that the plasma temperature and electron number density decrease slowly in the applied magnetic field due to the deceleration of the plasma plume. The optimized conditions for the maximum plasma confinement and the emission intensity enhancement are observed at 130 mJ laser energy at 0.7 T magnetic field.

In this paper, the scheme of generation of second harmonics of incident electromagnetic wave having a Hermite–Gaussian intensity profile in an under dense relativistic plasma has been presented. The relativistic mass variation of electrons by the intense electric field of incident beam generates the density gradients in background plasma which further excites the electron plasma wave (EPW) at resonant frequency and coupling of the EPW with the incident beam results in the generation of second harmonics of incident beam. Propagation dynamics of the Hermite–Gaussian laser beam in plasma has been studied by the formulation of differential equation for the spot size of the laser beam with the help of method of moments. Numerical simulations have been carried out to solve the differential equation for the dimensionless beam width parameters. Solution of the nonlinear wave equation for the electric field vector of second harmonics of incident beam gives the expression for second-harmonic yield. It has been observed that second-harmonic yield is affected by the different modes of Hermite–Gaussian laser beam in relativistic plasma.

The present work is motivated by the numerous applications of short lasers–ceramics interaction. It aims at applying a newly developed model to investigate the dynamic of laser-induced plasmas from a ceramic material into a helium gas under atmospheric pressure. To have a better understanding of the link between the material properties, the plume characteristics and its interaction with the laser beam, a thorough examination of the entire ablation processes is conducted. Comparison with the behavior of laser-induced plumes under the same conditions from a pure material is shown to have a key role in shedding the light on what monitors the plume expansion in the background environment. Plume temperatures, velocities, ionization rates as well as elemental composition have been presented and compared under carefully chosen relevant conditions. This study is of interest for laser matter applications depending on the induced plasmas dynamics and composition.

This study investigates the interaction of picosecond laser pulses with sapphire and brass in air using scanning electron microscopy. A picosecond laser system operating at a wavelength of 785 nm, pulse width of 110 ps, and variable repetition rate (1–1000 Hz) was used in this study. The pulse width applied in this work was not widely investigated as it lies in the gap between ultrashort (femtosecond) and long (nanosecond) pulse width lasers. Different surface morphologies were identified using secondary electron and backscattered electron imaging of the ablated material. Thermal ablation effects were more dominant in brass than in sapphire. Exfoliation and fractures of sapphire were observed at high laser fluence. Compared with brass, multiple laser pulses were necessary to initiate ablation in sapphire due to its poor absorption to the incident laser wavelength. Ablation rate of sapphire was lower than that of brass due to the dissipation of a portion of the laser energy due to heating and fracturing of the surface.

This paper introduces recent activities on Marx-based compact repetitive pulsed power generators at the Institute of Applied Electronics (IAE), China Academy of Engineering Physics (CAEP), over the period 2010–2018. A characteristic feature of the generators described is the use of a simplified bipolar charged Marx circuit, in which the normal isolation resistors or inductors to ground are removed to make the circuit simpler. Several pulse-forming modules developed to generate a 100 ns square wave output are introduced, including thin-film dielectric lines of different structures, a pulse-forming line based on a Printed Circuit Board, and non-uniform pulse-forming networks. A compact repetitive three-electrode spark gap switch with low-jitter, high-voltage, and high-current was developed and is used in the generators. A positive and negative series resonant constant current power supply with high precision and high power is introduced. As an important part of the repetitive pulse power generator, a lower jitter pulse trigger source is introduced. Several typical high-power repetitive pulsed power generators developed at IAE are introduced including a 30 GW low-impedance Marx generator, a compact square-wave pulse generator based on Kapton-film dielectric Blumlein line, a 20 GW high pulse-energy repetitive PFN-Marx generator, and a coaxial Marx generator based on ceramic capacitors. The research of key technologies and their development status are discussed, which can provide a reference for the future development and application of miniaturization of compact and repetitive Marx generators.

In this paper, we study the excitation of Gould–Trivelpiece (TG) waves by streaming ions in dusty plasma and derive the dispersion relation of the excited waves using first-order perturbation theory. The motion of charged particles is controlled by electromagnetic fields in plasma. The energy transfer processes which occur in this collisionless plasma are believed to be based on wave–particle interactions. We have found that the TG waves may be generated in a streaming ion plasma via Cerenkov interaction, and the ions may be accelerated by TG waves via cyclotron interaction, which enable energy and momentum transfer. The variation in the growth rate of TG wave with dust grain size and relative density of negatively charged dust grains is also studied. The dust can cause an unstable TG mode to be stable in Doppler resonance, and can induce an instability in Cerenkov interaction.

The effect of laser fluence and nature of ambient environments on the sputtering yield, surface modifications, crater depth, UV-visible absorption spectra, chemical composition, and micro hardness of Zr has been investigated. Nd: YAG laser (532 nm, 10 Hz, 6 ns) at different fluences varying from 16 to 60.8 Jcm−2 was employed as an irradiation source. All measurements are performed under two ambient environments of Ar and O2 at a constant pressure of 10 Torr. Quartz crystal microbalance has been employed for the measurement of sputtering yield of laser irradiated Zr. It is revealed that sputtering yield increases monotonically with increasing fluence under both environments however, it is higher in Ar as compared to O2 environment. Scanning electron microscope (SEM) has been used to explore the surface morphology. SEM analysis exhibits the formation of cones, ridges, and cracks at the central ablated areas whereas, laser-induced periodic surface structures, periodic ridges and sharp cones are observed at inner boundaries in both environments of Ar and O2. Sharp spikes are observed in both environments, however, their height and distinctness are more pronounced in Ar as compared to O2. Cones are characteristic features in Ar, whereas, cavities and channels are dominant features in O2 environment at outer boundaries. The formation and growth of surface structures are dependent upon laser fluence and ambient gas nature. The depth profilometry has been used to measure the crater depth of irradiated Zr target by using an optical microscope. UV visible spectroscopy and energy-dispersive X-ray analyses reveal the oxide formation in the case of Zr irradiation in O2 environment. The Vicker Micro-hardness tester has been employed to measure the hardness. The higher observed values of sputtering yield, crater depth and hardness of laser ablated Zr in Ar as compared to O2 are well correlated with distinct surface structures.

In 1988 Professor Guillermo Velarde, founder of the Instituto de Fusión Nuclear (IFN), chaired the 19th European Conference on Laser Interaction with Matter held in Madrid on 3–7 October 1988. About 170 scientists from Europe, the Soviet Union, United States, Japan, Canada, Israel, Australia, China, and South Africa participated in the ECLIM 88. ECLIM 88 was among ECLIM's series a turning point in inertial confinement fusion (ICF) research. The work already performed by different laboratories in Europe, Japan, and around the world had reached a level such that without explicitly expressing it, the collective scientific consensus wanted a change in the existing close policies in several ICF areas at large Laboratories in the USA, Russia, France, and UK.

Dr. Erik Storm from the US Lawrence Livermore National Laboratory proposed to Professor Velarde to write a letter to be signed by the participants of the ECLIM in favor of having an open international collaboration in ICF. Professor Velarde then suggested drawing up a manifesto instead of a letter because the name manifesto had bigger historical connotations. The manifesto received a very successful response among the conference participants and was signed by more than 130 scientists. Our paper aims at twofold objective: (1) to put into account the positive repercussions derived from the MADRID MANIFESTO in the ICF research and (2) to remember the figure of Professor Guillermo Velarde, the most influential physicist in nuclear fusion energy by inertial confinement along the 20th century. His inspiration and leadership in science contributed to make this world a safer and secure place and for us, his disciples and colleagues, an irreplaceable personality in our lives.

Influence of backstreaming ions from the target on spot size of focused 2 MeV electron beam was considered. The 2D version of the particle-in-cell code KARAT was used to study the formation of the ions stream and dynamics of the electron beam. It was shown that light species emitted from the target can disrupt the beam. The emission of low-ionized states of tantalum cannot disrupt the beam during about 30 ns or longer. A few non-invasive techniques of mitigation of the beam disruption were considered. Final magnetic lens with fast variation of magnetic field of several hundred Ampere-turns per nanosecond is capable to stabilize initial spot size of the compressed beam at the target.