The interaction of a cylindrical converging shock wave with an initially perturbed gaseous interface is studied experimentally. The cylindrical converging shock is generated in an ordinary shock tube but with a specially designed test section, in which the incident planar shock wave is directly converted into a cylindrical one. Two kinds of typical initial interfaces involving gas bubble and gas cylinder are employed. A high-speed video camera combined with schlieren or planar Mie scattering photography is utilized to capture the evolution process of flow structures. The distribution of baroclinic vorticity on the interface induced by the cylindrical shock and the reflected shock from the center of convergence results in distinct phenomena. In the gas bubble case, the shock focusing and the jet formation are observed and the turbulent mixing of two fluids is promoted because of the gradually changed shock strength and complex shock structures in the converging part. In the gas cylinder case, a counter-rotating vortex pair is formed after the impact of the converging shock and its rotating direction may be changed when interacting with the reflected shock for a relatively long reflection distance. The variations of the interface displacements and structural dimensions with time are further measured. It is found that these quantities are different from those in the planar counterpart because of the shock curvature, the Mach number effect and the complex shock reflection within the converging shock tube test section. Therefore, the experiments reported here exhibit the great potential of this experimental method in study of the Richtmyer-Meshkov instability induced by converging shock waves.

A fluid description is used to study the properties of two-stream instability due to interaction of a non-relativistic electron beam with quantum magnetized plasma and transverse wiggler magnetic field. It is assumed that the background plasma provides charge and current neutralization of the electron beam. The dispersion relation is obtained by solving and linearizing fluid-Maxwell equations. The resulting dispersion equation is analyzed numerically over a wide range of system parameters. The results of quantum and classical treatments are compared numerically, with including the effects of wiggler on the dispersion relation. It is found that the transverse wiggler magnetic field can strongly improve the instability of quantum plasma as well as classical plasma.

In the present paper, measurement of various plasma parameters during pulsed laser deposition of ruby thin film on quartz substrate is reported. The variation of electron temperature and ion density with laser fluence and ambient pressure is recorded via Langmuir probe technique. The structural and optical properties of ruby thin films were analyzed using photo-luminescence and atomic force microscopy, and then correlated with the plasma parameters to find optimum conditions for deposition of high quality ruby thin film.

Hundred picoseconds laser pulse with high energy and high peak power has broad application prospects such as inertial confinement fusion shock ignition. But it is hard to get effective amplification through MOPA or chirped pulse amplification method. Through simulated Brillouin scattering method, 100 picoseconds laser pulse can be amplified efficiently. To be able to meet the need of high energy and high-intensity laser pulse amplification, scalable two cell structure and four different FC series liquid were used to fulfill this experiment. The results indicate that the magnification of Stokes energy and efficiency of energy extraction are closely related to medium parameters and energy parameters. The minimum width of 340 ps Stokes pulse was amplified by 13.5 times in this experiment.

Resonant excitation of terahertz (THz) radiation by nonlinear coupling of two filamented spatial-Gaussian laser beams of different frequencies and wave numbers is studied in plasma having transverse static electric field. The static ponderomotive force due to filamented lasers is balanced by the pressure gradient force which gives rise to transverse density ripple, while, the nonlinear ponderomotive force at frequency difference of beating lasers couples with density ripple giving rise to stronger transverse nonlinear current which results into the excitation of THz radiation at resonance. The coupling is further enhanced by the presence of static electric field and spatial-Gaussian nature of laser beams. An increase of six-fold in the normalized amplitude of THz is observed by applying a direct current field of about 50 KV. Effects of frequency, laser beam width, and periodicity factor of modulated laser amplitude are studied for the efficient THz radiation generation. These results can be utilized for generating controlled tunable THz sources for medical applications using low filament intensities (~ 1014 W/cm2) of beating lasers.

Laser generated plasmas from target normal sheath acceleration produce energetic ions from the rear side of the target due to the formation of a high directive electric field. Fast electrons are ejected from the rear side of the target and a successive Coulomb explosion is driven by the fast electrons generating a high electric field of double layer. The ion acceleration is mainly controlled by the laser intensity and by the square of the laser wavelength. Literature reports that at intensities of the order of 1018 W/cm2 and at wavelengths of about 1 µm the ion energy is of the order of 5 MeV/nucleon. The use of advanced targets realized with the aim to reduce the surface reflection, to increase the laser absorption coefficient and, with an optimal thickness, to increase the electric field of the double layer, permits to enhance the ion energy acceleration, so that the energy of 5.0 MeV per charge state can be reached at about 1016 W/cm2, as it will be presented and discussed.

In this work, the effect of electron trapping on the self-similar expansion of electron-ion laser plasma into vacuum, combined with the effect of non-thermal (energetic) electrons is studied. For this, a mono-dimensional, non-relativistic model where the ions are cold and governed by fluid equations is used. In the approximation of quasi-neutrality of charge, the obtained self-similar solution shows that for ion (plasma) behavior, the presence of an important number of non-energetic trapped electrons in the plasma potential wells has the effect of slowing down the expansion, whereas the phenomenon of presence of energetic electrons makes the influence of trapping effect on the self-similar expansion very weak even in the case of a very small number of energetic electrons. This study is of interest in the context of the investigation of mono-energetic ion beams from intense laser interactions with plasmas.

We have performed extensive one dimensional particle-in-cell (PIC) simulations to explore generation of electrostatic waves driven by two-stream instability (TSI) that arises due to the interaction between two symmetric counterstreaming electron beams. The electron beams are considered to be cold, collisionless and magnetic-field-free in the presence of neutralizing background of static ions. Here, electrons are described by the non-extensive q-distributions of the Tsallis statistics. Results shows that the electron holes structures are different for various q values such that: (i) for q > 1 cavitation of electron holes are more visible and the excited waves were more strong (ii) for q < 1 the degree of cavitation decreases and for q = 0.5 the holes are not distinguishable. Furthermore, time development of the velocity root-mean-square (VRMS) of electrons for different q-values demonstrate that the maximum energy conversion is increased upon increasing the non-extensivity parameter q up to the values q > 1. The normalized total energy history for a arbitrary entropic index q = 1.5, approves the energy conserving in our PIC simulation.

Fusion reactions of solid density boron-11 with protons after initiation of a fusion flame by very powerful picosecond laser pulses were derived for plane geometry. The problem of lateral energy losses with laser beams was solved by using spherical geometry, where however the gains are limited. The other elimination of losses now available by cylinder-axis symmetric 10 kilotesla magnetic fields is possible needing laser powers in the exawatt range. Estimations are presented by varying parameters for reducing the necessary laser pulse powers to lower values by up to a factor 100.

An ultra-wideband radiation source based on the excitation of a 64-element array of combined antennas by a generator of bipolar voltage pulses with the length of 1 ns, amplitude of 200 kV and pulse repetition rate of 100 Hz has been designed and studied. The peak power of the voltage pulse was 3.2 GW. The effective potential of the ultra-wideband source radiation reached 4.3 MV.

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.

This paper describes the spatial and temporal investigation of laser ablated plasma plume of cerium oxide target using Langmuir probe. Cerium oxide target was ablated using a KrF (λ ~ 248 nm) gas laser. Experimental studies confirmed that oxygen partial pressure of 2 × 10−2 mbar is sufficient enough to get good quality films of cerium oxide. At this pressure, plume was diagnosed for their spatial and temporal behavior. Spatial distribution was investigated at a distance of 15 mm, 30 mm, and up to a maximum distance of 45 mm from the target, whereas temporal behavior has been recorded in the range of 0 to 50 µS with an interval of 0.5 µS. The average electron densities are found to be maximum at 30 mm from the target position and the plasma current of the laser ablated ceria is found to be maximum at 22 µS.

In order to use two paralleled X-pinches as X-ray sources for the time-resolved backlighting of wire-array Z-pinch plasma, it is necessary to make these two X-pinches emit X-rays at different but roughly preset time instants. The timing of the X-ray burst from an X-pinch independence of the current, and the wire mass of the X-pinch was investigated. The currents flowing through two paralleled X-pinches were measured and it was found that the total current is almost equally divided between these two X-pinches no matter how different the wires for these two X-pinches are. The reason for the equal current division between two paralleled X-pinches was given based on the inductance calculation of the X-pinch circuit.

The diode closure velocity has been investigated in pulsed high-power diodes operating with the mode of space-charge-limed bipolar flow. A combination of time-resolved electrical and optical diagnostics has been employed to study the basic phenomenon of the temporal and spatial evolutions of the diode plasmas. The results from the two diagnostics were compared. Since anode plasma rapidly expands, the diode closure speed vd increases in the end of the current pulse. The diode closure speed vd can be divided into three stages with a U-like whole shape. The obtained results can be used in various applications, for instance, the high-power microwave sources, electron-beam plasma heating, and material treating.

This research reports the increased electron energy gain from laser wakefield acceleration in density-modulated plasma with an external magnetic field. Periodic plasma density- modulation can excite higher harmonics of different phase velocities of fundamental wakefield that can assist in improving the self-trapping of pre-accelerated electrons to accelerate them for higher energy. Furthermore, the applied magnetic field assisted self-injection can also contribute in electron energy enhancement during the acceleration. The physical mechanism is described with a theoretical formulation for this scheme. Results of two-dimensional particle-in-cell simulations are reported to understand the proposed idea.

High-intensity lasers are an effective source for the acceleration of high-energy particles. Using different interaction configurations, such facilities can be optimized for the acceleration of electrons, protons, heavy ions, high-energy photons, or neutrons. The shielding of these facilities to ensure the safety of personnel has always been a critical requirement and is a fundamental step within the design phase. The knowledge of radiation source terms through both experiments and modelling is now well understood and for the most part can be dealt with through the use of shielding and specialized beam dumps. Unlike most other particle accelerators most high-power laser facilities are still accessed by personnel post shot with little or no remote handling capabilities. As a result, the secondary activation and control of components that lie around the interaction is of great importance to safety. In this paper, we present a 10 year history of activation data on the Vulcan petawatt facility and discuss the primary sources of activation and the potential impact on future laser facilities.

For a Megawatt class accelerator, classical safety measures may not be sufficient. Precise knowledge of beam loss location and power deposition in the most various scenarios is crucial for the definition of appropriate protection systems. In this work, the case of the Linear IFMIF Prototype Accelerator is studied, where, due to its very high continuous wave beam intensity, the high power part concerns almost the whole accelerator. Beam dynamics simulations are performed to allow the ability to estimate beam losses in all the different situations of the accelerator lifetime: starting from scratch, beam commissioning, tuning or exploration, routine operation, sudden failures. All the results of these studies are given, establishing the catalogue of losses. Recommendations for hot point protection, beam stop speed, beam power limitation are given accordingly.

High voltage, high current inductors are required for many high pulsed power systems, incorporating capacitor banks. Those inductors simultaneously serve both as a pulse shaping and protection element in R-L-C circuits. A 25 kV/70 kA protection inductor on inductance of 1 mH with low stray field was designed, manufactured, and tested. It was designed as a quasi-toroidal system, consisting of four coils (with 0.25 mH inductance each) evenly distributed in the perimeter of a square. The structure of coils was optimized to withstand a huge electromagnetic force produced by a 70 kA current. The 0.25 mH coil is made as multi-layer solenoid (six layers) from a copper wire (6 × 4 mm2 net cross-section) with fiberglass insulation. Layers are connected in parallel in order to decrease active resistance of the coil. This 0.25 mH coil was tested at 70 kA peak current with a pulse length of about 20 ms, which corresponds to the action integral at about 32 × 106 A2s. Maximum magnetic field inside the coil is about 12 T. A finite element analysis with the ELCUT software was used to calculate the magnetic field, temperature rise, and stresses in the protection inductor. The typical maximum stresses in our design are 100 MPa in copper coils and 140 MPa in fiberglass body tubes; these are both below the yield strength for these materials. Simulations results are compared with the experimental tests and good agreement is observed.

We prove that the radiation damping force and the rate of change of the damping energy, in the Landau-Lifshitz forms, in interactions between very intense laser beams and relativistic electron beams, are periodic functions of only one variable, that is the phase of the electromagnetic field. The property is proved without using any approximation, in the most general case, when the degree of polarization of the electromagnetic field, the initial phase of the incident field and the initial energy of the electron have arbitrary values. This property leads to a strong simplification of the calculation of the radiation reaction parameters and of their dependence on the initial electron energy and angular frequency of the laser beam. Our analysis is performed in the proper inertial system of the electron. The radiation reaction is significant for laser beam intensities of the order 1022 W/cm2, and for electron energy greater than 1 GeV. The calculations reveal limitations of the method of generating hard radiations by interactions between laser beams and relativistic electron beams.

The problem of initial thermal velocity and the space charge effect of electron guns in numerical simulations have been investigated deeply. In general, the current software can meet the engineering requirements. However, the electron's initial thermal velocity and the space charge effect lack sufficient consideration. The above two factors significantly limit the performances of electron guns. Moreover, the parameters of electron guns are approximated based on a limited number of electron trajectories. Thus, the statistical distribution of the beam electron resulting from its initial thermal velocity is not considered adequately in present software. This paper introduces the equivalent meridional projected trajectory equation and the curvilinear axis evolution theory of the current density of toroidal electron sub-beam, and subsequently the current and charge density distributions in electron guns can be derived through iteration calculation. Based upon, the virtual crossover of an electron gun is determined by its current density distribution. As well as, a relevant numerical algorithm is developed and the related program is modified based on the popular commercial software SOURCE. Tungsten cathode guns, LaB6 cathode guns, field mission guns and Pierce guns are simulated respectively by examples. The calculations prove that the modified software is effective and practical.