The results of formation of elongated krypton/helium plasma channels are presented. Two laser pulses were used: one to produce plasma channels and the second one for conversion to soft X rays. The soft X-ray radiation was in turn used for backlighting the channels and their visualization. The study of their formation and uniformity was performed using a combination of soft X-ray shadowgraphy and pinhole camera imaging. The plasma channels, with various lengths and various densities, were visualized and the results of their characterization are presented. Using moderate laser pulse energy quite uniform channels, up to 9 mm in length, were demonstrated.

Characterization measurements and modes of operation of a novel, dual-gas multi-jet target, developed for experiments on high-order harmonic generation, are presented. The target has been formed by pulsed injection of argon through a nozzle in a form of linearly oriented small orifices. The argon jets were separated with the helium jets formed by injection of helium through alternate orifices in the nozzle. The targets have been characterized by extreme ultraviolet backlighting at 13.5 nm wavelength. Density profiles for this type of targets have been obtained, to our knowledge, for the first time.

Pulsed laser induced plasma in water produces multiple bubbles with the passage of laser pulse. Shadowgraphy and beam deflection set-up is used to study the temporal and spatial evolution of these bubbles as a function of distance from the laser focus. The formation of multiple bubbles, bubble coalescence, and their effect onto cavity dynamics is reported. Bubble radius and the corresponding velocities from shadowgraphy is used to calculate the maximum gas pressure inside the bubble using Neppiras model. The maximum pressure inside the cavity is found to be 0.4 MPa at the laser focus.