Experimental studies of interaction of intense long laser pulse with a laser-created Ta plasma

Abstract

Characteristics of ions, emitted from the laser produced plasma, were systematically investigated using high power iodine laser system PALS, operating at 3 ω. A Ta target was irradiated perpendicularly with laser pulse energy 150 J. Changing the laser focus position, not only the laser intensity, but also the length (duration) of laser beam interaction with pre-formed plasma is changing. Self-focusing of laser beam in self-created plasma was proved, moreover with longitudinal structure with a period of ∼ 200 µm.

Factors influencing parameters of laser ion sources

“…The distribution of intensity along the filament was observed as moon-like spots of decreasing intensity with a spatial distribution of $200 mm; conditions for their appearance were derived from theoretical modeling. Similar moon-like spots in the expanding plasma plume with the time distance around 100 ps and with the changing intensity (even splitting into two plasma plumes) was recorded by an X-ray streak camera (La ´ska et al, 2006b). Considering the measured velocity of the majority of emitted fast ions $2 Â 10 8 cm/s (La ´ska et al, 2006b), we obtain a similar space scale around $200 mm.…”

“…The intense pulse interaction with pre-plasma produced by the front edge may be a source of various non-linear processes, supporting the extreme characteristics of the produced ions. This is the reason for a well documented appearance of more or less significant self-focusing of intense laser beams (present in almost all of such interaction experiments), even with a possible longitudinal structure (Lei et al, 2006;La ´ska et al, 2006aLa ´ska et al, , 2006b, as well as of generation of a large number of superfast ion subgroups (La ´ska et al, 2005a(La ´ska et al, , 2005b(La ´ska et al, , 2005c. In Figure 1, up to 14 more or less pronounced peaks on the IC signals (14 ion subgroups) have been distinguished, numbered from 2 to 14, which are distributed, in principle, over three generally accepted ion groups: slow S (13,14), thermal T (12,11), and fast F (10,7).…”

Angular distributions of ions emitted from laser plasma produced at various irradiation angles and laser intensities

“…At intensities above 1 Â 10 14 W/cm 2 , the optimum FP makes the interaction of the laser radiation with the expanding plasma plume very effective and the conditions for occurrence of various non-linear processes (including ponderomotive and/or relativistic self-focusing (Hora, 1969(Hora, , 1975Hauser et al, 1992;Kumar et al, 2006;La ´ska et al, 2006;Rowlands, 2006)) can be met. Then heavy ions with the highest charge states and energy can be generated (La ´ska et al, 2003(La ´ska et al, , 2004b(La ´ska et al, , 2005a.…”