High-resolution K-shell spectra of a plasma created by superintense laser irradiation of micron-sized Ar clusters have been measured with an intensity above 10 19 W0cm 2 and a pulse duration of 30 fs. The total photon flux of 2 ϫ 10 8 photons0pulse was achieved for He a1 resonant line of Ar~l ϭ 3.9491 Å, 3.14 keV!. In parallel with X-ray measurements, energy distributions of emitted ions have been measured. The multiply charged ions with kinetic energies up to 800 keV were observed. It is found that hot electrons produced by high contrast laser pulses allow the isochoric heating of clusters and shift the ion balance toward the higher charge states, which enhances both the X-ray line yield of the He-like argon ion and the ion kinetic energy.

The time evolution of the matter parameters and current distribution in the discharge channel formed during a nanosecond explosion of a 25 µm diameter 12 mm long aluminum wire was studied in a series of experiments with the following parameters: the discharge voltage was U 0 = 20 kV, the current ampli tude was I max ~ 8 kA, and the current rise rate was dI/dt ~ 40 A/ns. Optical shadow and schlieren images of the discharge channel were obtained using the second harmonic of a YAG : Nd +3 laser, and UV images of the discharge channel self radiation were recorded using a four frame camera with a microchannel plate. The process of aluminum wire explosion was simulated numerically (including simulations performed from the "cold start"). The numerical results were compared with the experimental data.

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