Modeling of annular-laser-beam-driven plasma jets from massive planar targets

Abstract

Production of sharply collimated high velocity outflows – plasma jets from massive planar targets by a single laser beam at PALS facility is clarified via numerical simulations. Since only a few experimental data on the intensity distribution in the interaction beam near the focus are available for the PALS facility, the laser beam profile was calculated by a numerical model of the laser system and the interaction optics. The obtained intensity profiles are used as the input for plasma dynamic simulations by our cylindrical two-dimensional fluid code PALE. Jet formation due to laser intensity profile with a minimum on the axis is demonstrated. The outflow collimation improves significantly for heavier elements, even when radiative cooling is omitted. Using an optimized interaction beam profile, a homogeneous jet with a length exceeding its diameter by several times may be reliably generated for applications in laboratory astrophysics and impact ignition studies.

Microjet formation and hard x-ray production from a liquid metal target irradiated by intense femtosecond laser pulses

“…The low density jets could be related to a directed ejection of vapors created at the target surface by a fast laser energy deposition. 8 However, such jets become transparent to optical probes in a nanosecond time scale, which is not the case of present observations. Another possibility is the formation of cumulative jets that corresponds to an ejection of a liquid material at a high speed.…”

Increase of the density, temperature and velocity of plasma jets driven by a ring of high energy laser beams

“…While the traditional approaches to address these questions are mainly direct observation and theoretical modelling, laboratory produced jets with proper scaling relations [4,5] may provide an alternative platform to study jets on astrophysical scales. In particular, jets formed by laser produced plasma have been successfully created by either irradiating a planar target with one "concaved" (intensity lower at the center) laser beam [6,7,8,9,10,11,12] or shining multiple beams onto a cone-shaped target [13,14]. In both designs ablated plasma plumes are produced at different locations on the target and collide on the central vertical axis.…”

Radiative characterization of supersonic jets and shocks in a laser-plasma experiment

“…The laser pulse had a Gaussian temporal profile with a full width at half maximum (FWHM) of 250 ps, and truncated wings, giving a full duration of 400 ps. Similar to the experiment [33], the laser had an annular intensity distribution on target, with a radius of r L = 300 µm (FWHM), as shown in the insert in figure 9a. The duration of the simulation extended from the initial laser-target interaction, to the subsequent shock formation and evolution over 20 ns.…”

“…It was focused using an aspheric lens (f = 600 mm) at normal incidence onto a flat massive copper target, with the focal plane located slightly behind the front surface of the target. The resulting defocused irradiated area on the target had a radius of r L 300 µm, with an annular intensity distribution [25,33]. The laser energy was in the range of E L 70 − 110 J, giving an average intensity on target of I L 10 14 Wcm −2 .…”