The contribution of different sorts of secondary particles to the preheating of thermonuclear targets driven by heavy-ion beams is analyzed. Two types of illumination geometry are considered: side-on and face-on locations of the fuel with respect to the ion beam. It is shown that a substantial preheating can be expected from (1) nuclear fission fragments for the face-on fuel position and (2) δ-electrons and low-Z nuclear fragments for the side-on fuel location. All the X-ray and gamma photons of various origin are shown to produce a negligible fuel heating.

An experimental study of laser-driven shock wave propagation in a transparent material such as Plexiglas using a high-speed optical shadowgraphy technique is presented in this paper. A Nd:glass laser was used to produce laser intensity in the range 1012-1014 W/cm2 on the target. Optical shadowgrams of the propagating shock front were recorded with a second-harmonic (0.53-μm) optical probe beam. Shock pressures were measured at various laser intensities, and the scaling was found to agree with the theoretically predicted value. Shock pressure values have also been obtained from a one-dimensional Lagrangian hydrodynamic simulation, and they match well with experimental results. Shadowgrams of shock fronts produced by nonuniform spatial laser beam irradiation profiles have shown complete smoothing when targets with a thin coating of a material of high atomic number such as gold were used. Shock pressures in such coated targets are also found to be considerably higher compared with those in uncoated targets.

Sodium laser blow-off plasma of low temperature (in the 1-eV range) is generated by laser intensities of 108–5.109 W cm−2. Imprisonment of resonant laser light has been observed. These experiments show that basic processes of interaction of radiation with level populations can be studied in the visible range, where the atomic levels have longer lifetimes than the ionic ones in hot plasmas, corresponding to X-ray generation. The imprisonment and resonant effects with various experimental parameters were investigated together with the nonresonant scattering on fragments.

Laser-produced plasma cloud evolution in a magnetic field is investigated up to 3 kg using photographs and spectroheliograms. Generation of a plasma jet, oriented across the magnetic field, was detected, whose emission increases with the field strength and is more distinct for multicharged ions. The effects of the field on the interaction of closely located laser-produced plasma clouds were studied as well. The results of numerical analysis comply with experimental data on plasma behavior in the magnetic field.

Spectroscopic study of plasma produced through bombardment of the 1 × 3 mm2 area on the surface of a solid Mg target with Kr+ ions is carried out. Spectral lines of Mg I and Mg II ions were observed in the visible range (200–600 nm). The plasma parameters Ne = 1.4.1017 cm−3 and Te = 0.8 eV are calculated from electron impact broadening of the 4f–3d line of Mg II and from the ratio of intensities for the 4f–3d and 4s–3p lines of Mg II. The ionic composition of the plasma is determined. The detected X-ray emission is shown to be the characteristic emission of the target.

The first harmonics beam generated by an iodine laser system was focused by an f/2 optics on an Al foil target. The X-ray output from the laser plasma both in the line and broad-band spectra was registered over an interval around the “ideal” focus. It was found that the maximum X-ray power is not obtained in the focus itself but for a somewhat larger focal spot outside the focus. To explain this phenomena, temperature and density measurements were in addition made. The plasma temperature evaluated from both the line (He-like Al XII resonant line and j, k, l satellites) and broad-band spectra (two foil method) was also measured and found to be largely constant in the vicinity of the focus. The line and broad-band temperatures differ, the broad-band temperature being about 25% higher. The electron density was equally determined using an intercombination line.

X-ray emission from planar targets irradiated by 1.054-μm laser pulses was observed with temporal, spatial, and spectral resolution. The main purpose of these measurements was the investigation of energy transfer in multilayer targets and X-ray conversion efficiency. A mass ablation rate was determined from temporal analysis of multicharged ion line emission and a key role of corona X-ray emission in accelerated material preheating was established.

The X-ray emission from laser-produced plasmas at an X-ray wavelength of approximately 10.4 nm was measured for Al and Gd target materials. The laser power density on the target surface was varied between 1.5 × 1010 and 3 × 1012 W/cm2 to obtain different electron temperatures. The output from the plasma was measured using an X-ray reflecting Pd-C multilayer coating as a wavelength-selective element and a diamond photoconductive detector. The emission at 10.4 nm is strongest at the low end of the power density range investigated. A strong increase is found for Al targets due to a contribution of line radiation, which is not present in the Gd plasmas. The measured conversion efficiency for Al plasmas was (4.5 ± 1)% in a 3% bandwidth at an X-ray wavelength of 10.4 nm.

In this article, we present the formation of an elongated plasma column by combining a laser plasma with an external magnetic field. The laser plasma is produced by irradiating solid targets with a focused Nd-glass laser. The targets were placed on the axis of the two, single-turn magnetic coils, which provided a magnetic field up to 500 kg in the target region. The expanding laser plasma is confined by the magnetic field and an elongated and uniform plasma column is formed on the axis of the coils. The plasma column emits strong, soft X-ray radiation. The pinhole photographs show that the plasma column is at least 5 mm long. To study the interaction of the expanding laser plasma with a magnetic field, the laser probing diagnostic was used.

The effect of laser intensity distribution along the line focus on the uniformity of the line-shaped plasmas produced is investigated with time-integrated and time-resolved soft X-ray and optical diagnostics. Evident plasma condition nonuniformities along the line focus resulting from nonuniform laser intensity distributions have been observed with a conventional simple line-focusing technique. With a new line-focusing technique producing a uniform laser illumination, a uniform, line-shaped plasma can be obtained. It is also found that nonuniformities under uniform laser illumination occur mostly during laser heating. The line-shaped uniform laser plasma can be used as a large, uniform X-ray source besides its importance in X-ray laser demonstration and amplification. As an application of such line-shaped plasmas as X-ray sources, the no-overcoat 5F X-ray film is calibrated for the first time by a new method in the soft X-ray range from 10–80 A.

It is shown that large gainlengths of amplified spontaneous emission (ASE) together with collisional effects in plasmas are liable to generate modifications in population inversions and then in observed gain values. In the case of the Ne-like Se24+ ion, one can expect a significant reduction of the J = 0–1 transition gain value at the wavelength of 18.24 nm.

A study of the effects of photoionization of a laser-produced plasma has been carried out by modeling the fluorescence of resonance lines due to cascades. The photoionization source is the X-ray M-band emission of a laser-produced high-Z plasma and it perturbs a ground state He-like aluminum plasma. Simulations have been performed to study the conditions necessary to maximize the fluorescence and guide future experiments. A collisional-radiative model is used to determine the optimal temperature and density of the pumped plasma, while hydrodynamic models are used to produce realistic plasma gradients and explore the optimum time delay of the photopumping.

Experimental investigations of laser-produced plasma expansion in a strong (−20 T) magnetic field have been carried out. The image and spectra of the plasma flame in the soft X-ray spectral region have been obtained. It has been shown that the strong magnetic field limits the transverse plasma expansion and strongly effects the ion-level populations.

The possibility of the occurrence of a population inversion between n = 3, 2 levels in H-like Al, as well as between levels of the n = 4, 3 manifold in He-like Al, has been inferred from time integrated K-line intensity ratios. Opacity-corrected inversion factors (1 − Ni/Nj) of about 0.6 for both He- and H-like Al have been obtained in counterstreaming Al-Au plasmas from which gain values of about 0.5 cm−1 have been estimated.