Two novel high-dispersion, high-resolution spectroscopic methods are described. The properties of the vertical dispersion variants of the double-crystal spectrometer and the Johann spectrometer with a cylindrically bent crystal are discussed and compared with those of standard spectroscopic schemes. Preliminary experimental data demonstrate the good luminosity and extreme spectral and 1-D spatial resolution of these methods, which should prove useful in high-precision X-ray spectroscopic measurements of laser-produced plasmas.

X-ray emission spectra in the 5–22 nm range were recorded from planar and structured (meshlike groove surface) gold targets at 45° and 90° to the laser axis. A laser beam of 10-ns duration with EL ≤ 700 mJ and 1.06-μm wavelength was used for the experiment. Experimental results indicate an enhanced X-ray yield from a structured target as compared to a planar target under identical experimental conditions. Increased X-ray emission is attributed to plasma confinement and the possibility of conversion of kinetic energy into localized thermal energy of the plasma. Results are analyzed explicitly on the incident laser energy.

The generation of high harmonics in laser–plasma interactions on the steep density gradients is discussed, especially by using short-pulse UV laser radiation. Low intensity experiments with 5·1015 W/cm2 generate harmonics in the VUV range, and the efficiency can be optimized by modifying the density gradient. To obtain higher harmonics and to clear some disagreements among different results concerning polarization properties of harmonics we switched for higher intensities. Our experimental arrangement makes it possible to obtain a 5·1017 W/cm2 intensity with a prepulse as low as 107 W/cm2 using a table-top system. Preliminary results and future trends for high-harmonics generation with this method are given.

This paper presents a model for excitation of electron plasma wave and resulting stimulated Raman scattering due to presence of a laser beam carrying null intensity in center (hollow Gaussian beam) in a collisionless plasma. We have studied the self-focusing of the hollow Gaussian beam and its effect on back stimulated Raman scattering process in the presence of ponderomotive nonlinearity. To understand the nature of propagation of the hollow Gaussian beam, electron plasma wave and back reflectivity, a paraxial-ray approximation has been invoked. It is predicted that self-focusing and back reflectivity reduces for higher order of hollow Gaussian beam.

The progress of the experimental research program at GSI for studying beam-plasma interaction phenomena is reported. Heavy-ion beams from the new accelerator facility SIS/ESR at GSI-Darmstadt are now available for experiments, and will soon deliver ≥ 109 particles per pulse in 100 ns. Focused on a small sample of matter, the beams will be able to produce a high-density plasma and to permit investigation of interaction processes of heavy ions with hot ionized matter.

For the intense beam from the new heavy-ion synchrotron (SIS), a fine-focus system has been designed to produce a high specific deposition power beam for target experiments with a beam-spot radius of 100 μm. We further discuss improvements of this lens system by nonconventional focusing devices such as plasma lenses.

Intense-beam experiments at the RFQ Maxilac accelerator at GSI have already produced the first heavy-ion-induced plasma with a temperature of 0.75 eV. New diagnostic techniques for investigating ion-beam-induced plasmas are presented. The low-intensity beam from the GSI UNILAC has been used to measure energy deposition profiles of heavy ions in hot ionized matter. In this experiment an enhancement of the stopping power for heavy ions was observed. The current experimental research program tests basic plasma theory and addresses key issues of inertial confinement fusion driven by intense heavy-ion beams.

If plasmas are considered fully ionized, the electronic stopping of a charged particle that traverses them will only be due to free electrons. This stopping can be obtained in a first view through the random phase approximation (RPA). But free electrons interact between them affecting the stopping. These interactions can be taken into account in the dielectric formalism by means of two different ways: the Mermin function or the local field corrections (LFCs). LFCs produce an enhancement in stopping before the maximum and recover the RPA values just after it. Mermin method also produces firstly a high increase at very low energies, then a small enhancement at low energies and finally decreases below RPA values before and after the maximum. Differences between the two methods are very important at very low energies and by 30% around the stopping maximum.

Achieved performance of and the future plan for the ASHURA, a 700-J KrF laser, are described. Nanosecond pulses (3–20 ns) with a bandwidth of 50 cm-1 have been produced by gain switching of a preamplifier. The pulses have been six-time angularly multiplexed and double-pass amplified by two electron-beam-pumped amplifiers. The output from the main amplifier is strongly saturated, and maximum energy of 660 J has been extracted in 90 ns with a stage gain of 40. Focused by an f = 1m spherical lens, maximum power density of 6 × 1014 W/cm2 can be obtained on target. The energy density ratio of prepulse on target has been suppressed below 1/107. The ASHURA is being upgraded by adding a next-stage amplifier that aims at 10-kJ output energy in 270 ns.

Relativistic fluid dynamics and the theory of relativistic detonation fronts are used to estimate the space–time dynamics of the burning of the Deuterium–Tritium fuel in laser-driven pellet fusion experiments. The initial “High foot” heating of the fuel makes the compressed target transparent to radiation, and then a rapid ignition pulse can penetrate and heat up the whole target to supercritical temperatures in a short time, so that most of the interior of the target ignites almost simultaneously and instabilities will have no time to develop. In these relativistic, radiation-dominated processes both the interior, time-like burning front, and the surrounding space-like part of the front will be stable against Rayleigh–Taylor instabilities. To achieve this rapid, volume ignition the pulse heating up the target to supercritical temperature should provide the required energy in less than 10 ps.

The interaction of relativistic electrons produced by ultrafast lasers and focussing them on strongly precompressed thermonuclear fuel is analytically modelled. Energy loss to target electrons is treated through binary collisions and Langmuir wave excitation. The overall penetration depth is determined by quasielastic and multiple scattering on target ions. Thus, it appears possible to ignite efficient hot spots in a target with density larger than 300 g/cc.

We present an overview of the performance of the Neutralized Drift Compression Experiment-II (NDCX-II) accelerator at Berkeley Lab, and report on recent target experiments on beam-driven melting and transmission ion energy loss measurements with nanosecond and millimeter-scale ion beam pulses and thin tin foils. Bunches with around 1011 ions, 1 mm radius, and 2–30 ns full width at half maximum duration have been created with corresponding fluences in the range of 0.1–0.7 J/cm2. To achieve these short pulse durations and mm-scale focal spot radii, the 1.1 MeV [megaelectronvolt (106 eV)] He+ ion beam is neutralized in a drift compression section, which removes the space charge defocusing effect during final compression and focusing. The beam space charge and drift compression techniques resemble necessary beam conditions and manipulations in heavy ion inertial fusion accelerators. Quantitative comparison of detailed particle-in-cell simulations with the experiment plays an important role in optimizing accelerator performance.

We consider the symmetry of cylindrical implosions of laser targets with parameters corresponding to experiments proposed for the LIL laser facility at Bordeaux: eight laser beams in octahedrical configuration, delivering a total of 50 kJ of 0.35 µm laser light in 5 ns, impinging on 1.26 mm diameter polystyrene cylindrical shells filled with deuterium at 30 bar and 5.35 mg cm−3; this configuration allows to place diagnostics along the symmetry axis to evaluate directly the uniformity of implosion. Numerical studies have been carried out by using the hydrodynamic computer codes MULTI and CHIC, including one-dimensional, and two-dimensional R–Z and R–θ simulations. Deuterium is compressed into a 1 mm long and 50 µm diameter filament, with density ranging from 2 to 6 g cm−3 and temperatures above 1000 eV. In spite of the reduced numbers of beams, a good symmetry can be achieved with a careful choice of the irradiation pattern. The heat transport smoothing between laser absorption zone and ablation layer plays a fundamental role in the attenuation of residual non-uniformities. Also, it has been found that the radiation transport determines the radial structure of the compressed filament.

The physics of muon-catalyzed fusion is summarized and discussed in the perspective of energy production by high density muon beams.

In this work, we present the spectroscopic studies of the plasma generated at the surface of manganese sulfate by the fundamental (1064 nm) and second harmonic (532 nm) of a Q-switched Nd:YAG laser. The 4s4p 4F7/2→ 4s 2H9/2 at 438.80 nm, 4p 2I11/2 → 4s22I11/2 at 440.80 nm, 4p 4G11/2 → 4s 2H9/2 at 464.27 nm, 4p 4F5/2→ 4s 4D7/2 at 467.16, 4p 4F5/2 → 4s24G 7/2 at 515.08 nm, and 4p 4F7/2 → 4s2 4G 9/2 at 519.65 nm transitions have been used to estimate the electron temperature through the Boltzmann plot method. The number density has been estimated from the Stark broadened profiles of the spectral line 348.30 nm. The spatial behavior of the electron temperature and number density has been examined at different ambient air pressures and with laser irradiance. The temperature and number density are found to be in the range from 9842 K to 9371 K and 1.58 × 1017 to 3.26 × 1016 cm−3 for the 1064 nm laser, from 9668 to 9297 K and 2.27 × 1017 to 5.79 × 1016 cm−3 for the 532 nm laser.

This article presents the results of a study on transportation of a pulse ion beam of gigawatt power. This beam is formed by a self-magnetically insulated diode with an explosive-emission cathode. The experiments have been performed using the TEMP-4M pulsed ion accelerator configured in double-pulse formation mode with the first negative pulse (300–500 ns, 100–150 kV), followed by the second positive pulse (150 ns, 250–300 kV). To increase the effectiveness of ion beam focusing, a metal shield is installed on a grounded electrode. Investigations are performed using a strip focusing diode, a cone diode, and a spiral diode with metal shields of different constructions. We observed that the beam diameter at the focus decreases from 60 mm (without shield) to 40–42 mm (with a shield), which leads to an increase in the energy density by a factor of 1.5–2 being 4–5 J/cm2 at the focus. We analyzed different mechanisms for ion trajectories deviation from an ideal one: Coulomb repulsion due to incomplete space charge neutralization, influence of electromagnetic fields, etc. It is found that for a strip focusing diode the concentration of low-energy electrons accompanying the ion beam exceeds the concentration of ions by 1.3–1.5 times. The use of a metal shield improves the transportation properties of the ion beam by keeping neutralizing electrons within the beam volume which ensures its space charge neutralization during the transport.

The effect of smoothing by spectral dispersion (SSD) on stimulated rotational Raman scattering (SRRS) in air has been investigated both numerically and theoretically. The suppression effect of SSD on SRRS process is verified and it is demonstrated and proposed that the suppression effect is attributed to two aspects: the decreasing of the laser fluence modulation degree and the reducing of Stokes gain coefficient caused by the temporal and spatial variation of the phase of the incident laser pulse. The simulation results show that the SRRS threshold distance can be lengthened by choosing appropriate SSD parameters.

We report on an experimental study on the interaction of a high-contrast 40 fs duration 2 TW laser pulse with an argon-cluster target. A high-charge, homogeneous, large divergence electron beam with moderate kinetic energy (~2 MeV) is observed in the forward direction. The results show that an electron beam with a charge as high as 12 nC can be obtained using a table-top laser system. It was demonstrated that the accelerated electron beam is suitable for a variety of applications such as micro-radiography of thin samples in a wide field of view. It can also be applied for in vitro dosimetry studies.

The free expansion of a heated mass of uniform gas (e.g. a laser produced plasma) can be modelled by self-similar motion with a linear velocity gradient. Using a series of numerical solutions we have shown that a reasonable representation is obtained by the use of a matching parameter relating the scale lengths in the prototype and its model, and that the representation improves as the ratio of the heating and disassembly times increases. In this paper we re-examine these two inferred results, and re-derive them on an analytic basis. The extension of the theory to multi-structured bodies shows that such systems of symmetric form allow self-similar motion, as does the particular case of an asymmetric one-dimensional foil. The case of isothermal foils is examined in detail to illustrate the derivation of the matching conditions.

A new method of generation of nanosecond soft X-ray pulses with a photon energy around 1 keV is presented. X-rays are generated in a high-temperature plasma, which is created as a result of the interaction of Nd:glass laser radiation with a gas puff target. The target was obtained by puffing a small amount of gas through the nozzle into the vacuum chamber by means of a pressure electromagnetic valve. The pulses of laser radiation, with pulse duration of 1 ns and energy up to 15 J, generated in the system of a high-power Nd:glass laser were used for the target heating. Spatial, spectral, and temporal measurements of X-ray emission have shown that the high-intensity soft X rays are generated as a result of the interaction of nanosecond pulses of Nd:glass laser radiation with the gas puff target. A high efficiency of X-ray generation is suggested to be related to the effect of condensation of the gas outflowing from the valve nozzle and, in effect, to the interaction of laser radiation with matter in a form of aerosol.

It has been shown that in the scattered radiation, generated by an ultrashort laser pulse impinging on a metal nano-layer, non-oscillatory wakefields appears with a definite sign. The magnitude of these wakefields is proportional to the incoming field strength, and the definite sign of them is governed by the cosine of the carrier-envelope phase difference of the incoming pulse. When we let such a Wakefield excite the electrons of a secondary target (say an electron beam, a metal surface or a gas jet), we can obtain 100 percent modulation in the electron signal in a given direction. This scheme can serve as a basis for the construction of a robust linear carrier-envelope phase difference meter. At relativistic laser intensities, the target is considered as a plasma layer in vacuum produced from a thin foil by a prepulse, which is followed by the main high-intensity laser pulse. The nonlinearities stemming from the relativistic kinematics lead to the appearance of higher-order harmonics in the scattered spectra. In general, the harmonic peaks are downshifted due to the presence of an intensity-dependent factor. This phenomenon is analogous to the famous intensity-dependent frequency shift in the nonlinear Thomson scattering on a single electron. In our analysis, an attention has also been paid to the role of the carrier-envelope phase difference of the incoming few-cycle laser pulse. It is also shown that the spectrum has a long tail where the heights of the peaks vary practically within one order of magnitude forming a quasi-continuum. Fourier synthesizing the components from this plateau region attosecond pulses has obtained.

Since DT laser fusion with 10-MJ laser pulses for 1000-MJ output now offers the physics solution for an economical fusion energy reactor, the conditions are evaluated assuming that controlled ICF reactions will become possible in the future using clean nuclear fusion fuel such as deuterium-helium(3) or hydrogen-boron(11). Using the transparent physics mechanisms of volume ignition of the fuel capsules, we show that the volume ignition for strong reduction of the optimum initial temperature can be reached for both types of fuels if a compression about 100 times higher than those in present-day laser compression experiments is attained in the future. Helium(3) laser-pulse energies are then in the same range as for DT, but ten times higher energies will be required for hydrogenboron(11).