Ablation by short optical and x-ray laser pulses

Abstract

The paper is devoted to experimental and theoretical studies of ablation of condensed matter by optical (OL), extreme ultraviolet (EUV) and X-ray lasers (XRL). Results obtained at two different XRL are compared. The first XRL is collision Ag-plasma laser with pulse duration τ L = 7 ps and energy of quanta hν=89.3 eV, while the second one is EUV free electron laser (EUV-FEL) and has parameters τ L = 0.3 ps and energy of quanta 20.2 eV. It is shown that ablation thresholds for these XRL at LiF dielectric are approximately the same. A theory is presented which explains slow growth of ablated mass with fluence in case of XRL as a result of transition from spallative ablation near threshold to evaporative ablation at high fluencies. It is found that the metal irradiated by short pulse of OL remains in elastic state even in high shear stresses. Material strength of aluminum at very high deformation ratesV /V ∼ 10 9 s −1 is defined.Keywords: Short pulse laser ablation, EUV and X-ray laser ablation of LiF, material strength defined in laser experiment

Ultrashort laser-matter interaction at moderate intensities: two-temperature relaxation, foaming of stretched melt, and freezing of evolving nanostructures

“…While the middle piece is short and steep, see pictures in papers. 9,18,21,28 That is, the early profiles replicate the temperature profile shifted along the propagation axis x. They are far from profiles with shocks.…”

“…Therefore the sloping pieces become steeper, while the steep middle piece becomes more sloping. 9,18,21,28 Focusing and steeping of the forward piece leads to breaking (overturning) of the wave and to formation of shock in the point of inflection. Later an amplitude of the jump increases, and shock wave with triangular shape appears.…”

“…small significance, and the thermomechanical response may be described in the one-temperature T e = T i = T approximation. To analyze our case with combined 2T and thermomechanical effects, we developed full 2T theory including 2T-equation-of-state (2T-EOS), 3 thermal transport properties of metals in 2T state, [3][4][5][6][7] and calculations of electron-ion coupling parameter 6, 8-10 for simple metals, 8 for dielectrics, 9,10 and for noble and transition metals 6 where a situation is complicated by d-band influence; see also works. [11][12][13][14][15] This allows us qualitatively describe transition from light absorption to 2T state, and from 2T stage to hydrodynamics.…”

Using submicron-resolution LiF crystal and film x-ray detectors for the near and far fields in-situ characterization of soft x-ray laser beams

“…Here we present a review of the results [3,[5][6][7][8][9][10][11][12][13][14][15][16], obtained by using recently proposed new approach for applying a color center (CC) formation in LiF crystals and films to perform a high quality, single -shot in situ imaging of the near field and the far field measurements of soft X-ray laser (SXRL) beams parameters. Such detectors have submicron spatial resolution [8,9,12,14] and also more stable to direct intense laser radiation compared with the X-ray CCD.…”