ИСТИНА

The anisotropy and the spatial configuration of the ion source generated under femtosecond laser interaction with clusters are investigated by pinhole imaging method. Laser pulses with the duration of 36 fs, energy of 160 mJ and laser intensity of 4x1017 W/cm2 interacted with CO2 cluster target. The dependence of source structure represented in the pinhole image on the position of focus of the laser pulse in respect to the jet axis was investigated. We observed decrease of ion generation efficiency at large angles in the best focus of the laser. Anisotropy of the ion source is explained by the relativistic self focusing effect in the area of maximal laser intensity that is confirmed by the maximal yield of X-rays from this area. This results in efficient acceleration of the ion beam that becomes highly collimated in the direction of the laser beam propagation.