Although synchrotron radiation is thought to be well understood in a theoretical sense, the practicalities of controlling a synchrotron source sometimes seem difficult. Often the output spectrum contains sharp peaks, especially at the high-frequency end of the spectrum. These spikes are unwanted because they rob power from desired frequency intervals, and unexpected because idealized theory predicts a quite smooth spectrum. In the face of such difficulties, it has been natural to suspect some sort of engineering shortfall. But the present paper argues that the spectral structure may point instead to an imperfection of theory.

The computational tools used in the investigation of light-ion diode physics at Sandia National Laboratories are described. Applied-B ion diodes are used to generate intense beams of ions and focus these beams onto targets as part of Sandia's inertial confinement fusion program. Computer codes are used to simulate the energy storage and pulse forming sections of the accelerator and the power flow and coupling into the diode where the ion beam is generated. Other codes are used to calculate the applied magnetic field diffusion in the diode region, the electromagnetic fluctuations in the anode-cathode gap, the subsequent beam divergence, the beam propagation, and response of various beam diagnostics. These codes are described and some typical results are shown.

A model for the Stark broadening of ions in a high-density plasma created by laser has been developed by taking account of the full effect of a two-component plasma. One of the objectives of the work was to include the effect of ion dynamics in an efficient way. This has been achieved by using a stochastic process for mixing the different components that constitute a line profile. With the systematic use of fast algorithms, a code has been developed with the ability of treating complex atomic structures.

We have proposed an extension of the Model Microfield Method to the case of ionic radiators. Special attention is given to the accurate treatment of plasma mixtures in terms of static and dynamic statistical properties of the plasma microfield. Line shapes of one electron Carbon and Argon illustrate the influence of ion dynamic effects.

The results of an experimental investigation of iodine laser interaction with Al targets obtained on the laser system PERUN (λ = 1.315 μm, E < 50 J, τ ∼ 350 ps) by means of corpuscular diagnostics, are presented. Ion velocity distributions, angular distributions, and electron temperature were determined. The plasma electron temperature Te ∼ 550 ± 100 eV was weakly dependent on laser intensity in the range Iλ2 ∼ 1014-1015 Wcm-2 μm2. Maximal velocity (energy) for the Al ions was estimated as V ∼ 9 × 107 cm/s (∼ 110 keV) and the maximal measured charge state was z = 13. It was shown that the diameter of the area emitting high energy ions is a few times larger than the focus diameter (80 μm), which indicates a strong influence of lateral heat transport on plasma parameters. The hot electron temperature Te.h was estimated to be in the range 6–10 keV. On the basis of Langmuir probe measurements, the electron temperature of expanded Al plasma at a distance of about 100 cm was estimated to be Te ∼ 3 eV

Second harmonic emission from underdense laser-preformed plasmas has been investigated in forward direction with respect to the interaction beam axis. Two series of measurements have been performed using two focusing conditions and changing the intensity of the interaction beam. Effects of beam smoothing by random phase plates on second harmonic emission were also tested. Novel information on density and intensity gradients driven by filamentation instability was obtained.

The interaction of a plasma produced by irradiation of perforated foils with laser pulses was studied. The laser beam of the first harmonics of the iodine laser (λ = 1.315 μm) system PERUN was focused by anf/2 optics (f = 20 cm) on a hole in the foil target of high-Z material. The laser energy and the temporal shape of the pulses were monitored both before and behind the hole. Foils of two different materials (Pb, Cu) were used, and a series of hole diameters 2rH ranging from 100 μm to 500 μm were tested. The diameter of the laser focal spot 2r0 was about 150 μm. For hole diameters smaller than 300 μm, a shortening of the laser pulse was observed, demonstrating the effect of plasma shutter. The pulse shortening, which depends on the hole diameter, corresponds to the reduction in the pulse energy passing through the hole. An analysis of the experimental data is based on hydrodynamic computations, and the physics of the process is illustrated by a simple analytical model.

Experimental spectra of hot dense plasmas of aluminium produced by the interaction of a subpicosecond laser with solid targets at 1016 and 5 × 1017 W/cm2 are analyzed and discussed. A detailed analysis of the K-shell spectra is given through time-dependent calculations of atomic physics postprocessed to Fokker-Planck calculations of the laser-matter interaction. The non-Maxwellian character of the electron distribution function is shown. An evaluation of the electronic density and of the ion temperature 7i will be presented through Stark line broadening calculations. An X-ray spectrum from a Tantalum target also will be presented along with a preliminary interpretation.

We report on a compact, all-glass laser using a fiberless CPA technique as a potential system for the generation of extreme high-contrast picosecond pulses in the terawatt power range. New exciting experiments in the field of laser-matter interaction at extremely high intensities require both a high output energy and a very high peak to background intensity ratio (contrast). At present the system delivers 1.5 ps-pulses of 1.5-J energy with an intensity contrast of 4.109.

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.

Radial inhomogeneity diagnostics in hot and dense laser plasmas are presented. By means of an analysis of the spatially resolved X-ray transverse emission of the plasma and of a theoretical modeling, we can access directly to the radial emission coefficient and to the transverse gradients. The intense aluminum Lyβ line has been chosen for this study, and different structured targets have been used to control the radiative transfer in the transverse direction. These targets (large or narrow emissive strips) give complementary results for the emission in the core (i.e., near the laser-target axis) or in the border of the plasma.

A microcylinder target is proposed for a recombination X-ray laser generation and is investigated by a numerical simulation. The size of the target is of the order of 1 cm in the axial direction and 100 μm in the inner radius. The target has an axial slit of 20 μm wide through which a line-focused laser illuminates the inner wall. The hot plasma produced inside is confined, and a part of this is blown out through the slit. This plasma cools due to the free expansion, so that a gain of a recombination X-ray laser appears outside the microcylinder. When a large enough amount of hot plasma is produced inside, it plays the role of a reserver. Numerical results show that the quasi-cw (continuous wave) gain of Hα line is obtained outside the aluminum microcylinder when the plasma, which has not recombined yet, is supplied continuously.