Numerical study of nanosecond laser interactions with micro-sized single droplets and sprays of xenon

Abstract

We present a thorough numerical study on interactions of a nanosecond laser with micro-sized xenon droplets. We developed a code which allows simulation of laser interactions with a single droplet as well as a spray. We give a detailed description of the code, and we present results on the dynamics of a microplasma produced by irradiation of a single xenon droplet with a laser focused at peak vacuum intensity in the 5×1010−5×1012 W∕cm2 range. We find that the heating of the plasma depends dramatically on the laser parameters (duration, pulse shape, and intensity) on one hand, and on the droplet diameter on the other. We also present results obtained with a spray which show that the dynamics of the microplasmas is very sensitive to the position of the droplets in the interaction volume. The predictions of our model agree well with recent experimental observations performed on laser-produced plasma sources for extreme ultraviolet lithography. In particular, the postprocessing of our data with a sophisticated atomic physics code has allowed us to reproduce quite well the spectrum emitted in the extreme ultraviolet range by a xenon plasma generated by laser irradiation of a spray of droplets.

Characterization and optimization of the laser-produced plasma EUV source at 13.5 nm based on a double-stream Xe/He gas puff target

“…12c (in this case the shape is more ellipsoidal). As the mass and electron density is constant in the sphere (not in time but in space), we show that the speed inside the sphere remains homothetic and consequently all the formulas for the kinetic energy, radiative losses [53] of energy, and impulsion balance [56] remain very simple.…”

“…29 (the ratio of the radiative losses over the laser energy) shows very high rates all over the domain of high conversion efficiency at 13.5 nm (more than 75%). For this reason, it is not possible to make a pure hydro simulation without radiation losses as noticed in [56]. It shows also that it is possible to build a very efficient broadband radiation converter (mostly in the 10-14 nm region).…”

Quantum molecular dynamics study of warm dense iron

“…All simulations are performed with 128 atoms for fluid iron where a cubic supercell of length L (volume V = L 3 ) is periodically repeated. The simulated densities range from 12.5 to 25.0 g/cm 3 . The temperature range from 0.5 to 15 eV has been selected to highlight the conditions as reached in nuclear explosion and high power laser experiments.…”

“…The fitted coefficients for A i,j and B i,j are summarized in Tables I and II. Here, the internal energy E and the pressure of the initial state at 7.85 g/cm 3 and T = 300 K have been taken as zero.…”

“…Due to technological, geological, and sociological importance, iron is one of the most studied materials. The demands for models of materials in the warm dense regime is of great interest in the context of astrophysics [1] and other fields of applications, such as the inertial confinement fusion, the realization of x-ray sources, and the interpretation of XUV spectroscopy experiments [2][3][4]. Accurate knowledge of the thermophysical properties of iron at the warm dense matter (WDM) regime, such as the equation of state (EOS), transport properties, and opacity [5], is essential in constructing a realistic model of Earth and in the description of the transition between the liquid outer core and the solid inner core [6,7] where pressure between 1.3 and 3.7 Mbar is reached.…”