The Effect of Pre-plasma and Self-focusing on Characteristics of Laser Produced Ions

Generation of various ion groups was studied using lasers of different pulse length and intensities. Up to thirteen ion subgroups have been distinguished when using the PALS iodine laser system in experiments that involve a laser interaction with a preformed plasma. In addition to generally accepted thermal, fast, and slow ion groups, the existence of the second fast (superfast) group was clearly proven. The threshold laser intensity I_L necessary fo appearance of nonlinear effects was confirmed to be × 10¹⁴W/cm² at our experimental conditions. Above this value, there exists an interval of laser focus positions in front of the target in which ions with significantly higher charge states and energies are produced, compared to experiments without pre-plasma interactions, due to nonlinear processes in preformed plasma.