Experimental and theoretical investigations of mechanisms responsible for plasma jets formation at PALS

Abstract

Recent experimental results demonstrated that well formed plasma jets can be produced at laser interaction with targets made of materials with high atomic number (A ≥ 29 where A = 29 corresponds to Cu). On the contrary, it is impossible to launch a plasma jet on low-A material targets like plastic. This paper is aimed at explanation of this difference by considering mechanisms responsible for plasma jet formation, i.e., the radiative cooling of ablative plasma and the influence of target irradiation annular profile speculated hitherto, newly complemented by different expansion regimes of the Cu and plastic plasmas (provided by numerical simulations). The experiment was carried out with the PALS iodine laser. Two different planar massive targets, plastic and Cu, as well as the plastic target covered by thin Cu layers of various thicknesses were irradiated by the third harmonic laser beam of energy of 30 J, pulse duration of 250 ps (full width at half maximum), and the focal spot radius of 400 µm. To find the most suitable range of these layers (from 28 to 190 nm) a simple analytical model of laser-driven evaporation was developed. Three-frame laser interferometer and an X-ray streak camera were used as two main diagnostic tools. Numerical modeling was performed with the use of two-dimensional hydrodynamic code ATLANT-HE. Results provided from experiments and theoretical analyses have proved that the process of plasma jet formation is rather complex. Relative importance of the three mechanisms mentioned above depends on the target irradiation geometry as well as the target material used.

Interaction of two plasma jets produced successively from Cu target

“…It confirms our earlier suggestion (Kasperczuk et al, 2009a) that there is one additional mechanism taking part in the plasma jet forming toward the two such mechanisms considered so far, namely the annular irradiation and the plasma radiative cooling. However, it turned out that the radiative cooling is not as effective as it follows from the theoretical predictions.…”

“…Their typical examples are presented in Figure 3. Its annular form, which is conserved for the whole time of plasma emission, corresponds to the target irradiation geometry being necessary for the plasma jet formation (Kasperczuk et al, 2009a). The plasma X-ray emission intensity distributions are normalized to unity, 0.05 being the step of the adjacent equidensity lines.…”

Laser-produced aluminum plasma expansion inside a plastic plasma envelope

“…17 Our experiments at the Prague asterix laser system (PALS) laser facility 18 have proved that an annular target irradiation plays a decisive role in the plasma jet forming. 19,20 The gas (iodine) laser PALS tends to generate a small central depression in the otherwise uniform intensity distribution in the transverse beam cross-section. This phenomenon is becoming more pronounced with the increasing laser energy.…”

Ion jet generation in the ultraintense laser interactions with rear-side concave target

“…The advent of ultrashort ultraintense laser pulses led to the development of new exciting fields in laser plasma interaction (Karsch et al, 1999;Malka et al, 2004;Roth et al, 2005;Mangles et al, 2006;Kawata et al, 2005;Yu et al, 2005;Glowacz et al, 2006;Koyama et al, 2006;Lifshitz et al, 2006;Sakai et al, 2006;Yu et al, 2007;Hora, 2007;Dromey et al, 2009;Fazio et al, 2009;Hoffmann 2008aHoffmann , 2008bKasperczuk et al, 2009aKasperczuk et al, , 2009bLaska et al, 2007;Limpouch et al, 2008;Malekynia et al, 2009;Sharma & Sharma 2009;Izgorodin et al, 2009;Li et al, 2009;Sadighi-Bonabi et al, 2009;Hong et al, 2009;Kline et al, 2009). The generation of energetic ion beams from laser plasma interaction is an exciting area of research with important applications ranging from medical proton therapy (Bulanov & Khoroshkov, 2002), high-energydensity physics (Patel et al, 2003), to fast ignition in inertial confinement fusion .…”