Hierarchical instability of a vortex ring array in multipulse laser-matter interactions

Abstract

In XeCl excimer Laser interactions with Co-coated steel surfaces, we have seemingly realized a quasi-linear array of vortex rings. These form from instabilities on an array of vortex filaments which emerge and then lead to a series of loops. Finally the collapse-and-reconnection process yields a cascade of nearby vortex rings. Since the filament array is subjected to randomly distributed local multipolar strains, unstable waves can develop on the vortex rings. These deformed shapes are frozen permanently by ultrafast cooling, following the last laser pulse. Using a modal analysis, an attempt is made to relate the wave structures to a parametric resonance instability which is caused by dipolar and a quadrupolar fields. Multipulse laser-matter interactions are thus capable of nonselective excitation of vortex ring instabilities of various sizes and various modal structures.

Curvature instability of a vortex ring

“…Yet a possibility might not be ruled out that the (0, 1) resonance serves as a seed for it. Lugomer & Fukumoto (2005) found possible evidence for this resonance in vortex rings of micron scale generated by a laser-matter interaction. But to discriminate the instability driven by the dipole field from others is not straightforward.…”

Shock induced variable density flows in the vacuum microchannel: I. medium laser fluence

“…The curvature of vortex filament exposed to torsion due to interaction with turbulent shearing field creates loops called the Hasimoto solitons (Lugomer, 1997) figure 13. When generated in laser-matter interactions with solid target they show tendency to formation of a series of the loops-the loop soliton-chains along the vortex filaments (Fukumoto and Lugomer 2003a, 2003b, Lugomer and Fukumoto 2005, as well as of supercomplex 3D networks (Lugomer and Fukumoto 2018). The loop solitons in the multiple laser interactions become unstable and after collapse-and-reconnection yield a cascade of nearby vortex rings.…”

“…The loop solitons in the multiple laser interactions become unstable and after collapse-and-reconnection yield a cascade of nearby vortex rings. (Lugomer andFukumoto 2005, Lugomer andMaksimovic 1997). The loop solitons may travel without friction along the filament and appear in LMI and in other systems up to the astrophysical scale.…”

Generation of ribbons, helicoids, and complex Scherk surfaces in laser-matter interactions

“…Here A is the perturbation amplitude equivalent to the height of the scratch wall, and k p is the perturbation wavenumber: k p = 2π/L μm −1 . An oscillatory shock perturbs the density interface (shear layer) transversally to the radial flow, or the flow from the central to the peripheral regions (y-direction), causing the formation of waves and their roll-up into vortex filaments of the core thickness σ ∼ 5−7μm [1][2][3][4]. As a result, a high density 1D array of vortex filaments (the separation distance between neighboring filaments Λ ≤ σ) has been generated.…”

“…It is well known that nanosecond laser-matter interactions (LMI) may generate a one-dimensional (1D) array of vortex filaments on a solid surface, with the behavior that is common to string-like formations of various systems [1][2][3]. Among them is the action of torsion that generates the Hasimoto solitons [1], formation and instability of vortex rings [4], the phenomena like helicoidal instability, reconnection, and merging of filaments [2], looping of the filaments in the strain field of a point defect, spiraling and pinning [3] etc. All these phenomena are possible due to the fact that vortex filaments (in a certain stage of the LMI), behave as a viscoelastic entity.…”