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Microscopic liquid beams : a unique tool to investigate extreme states of matter ranging from plasma to condensed matter physics - Robert E. Grisenti - Mardi 3 juin 2014 à 11 h

Robert E. Grisenti - Institut für Kernphysik JWG-­‐Universität Frankfurt(M) & GSIHelmholtzzentrum für Schwerionenforschung, Darmstadt

Mardi 3 juin 2014 à 11 h - INSP - 4 place Jussieu - 75252 PARIS Cedex 05 - Barre 22-32, 2e étage, salle 201

Abstract

A liquid jet is formed by injecting a liquid through a tiny aperture in a high-­‐vacuum chamber under laminar flow conditions. Owing to their unique features liquid jets have now found a very wide range of applications, ranging from more practically oriented areas such as microfluidics and ink-­‐jet print-­‐ ing to areas of basic research such as the generation of soft x-­‐ray, photoelectron spectroscopy, and x-­‐ ray structure analysis. Here I will describe two novel applications in two rather different research fields. On one side, advances in state-­‐of-­‐the-­‐art laser technology have led to the development of Petawatt laser systems that can generate ultra short pulses on the sub-­‐picosecond time scale. When focused to a spot size a few micrometers wide, these laser pulses can exceed peak intensities of 1021 W cm-­‐2, thus producing energy densities on a micrometer length-­‐scale larger than those produced by any other method. The interaction with such ultra intense laser pulses produces matter under ex-­‐ treme conditions that allow the investigation of a huge variety of exciting phenomena, ranging from the demonstration of tabletop-­‐scale ion accelerators to the generation of hot dense matter in the la-­‐ boratory. I will show that liquid jets turn out to be extremely attractive target systems with respect to the above applications, offering several unique advantages with respect to traditional targets such as thin foils. On the other hand, the use of microscopic liquid jets provides a completely new ap-­‐ proach to study phase transition phenomena in deeply supercooled liquids. When a liquid is cooled below its normal melting point it enters a metastable region, in the sense that the crystal has a lower free energy than the liquid. Supercooled liquid represent a fascinating system to study and offer unique possibilities to investigate non-­‐equilibrium phase transformation phenomena. Understanding structural transformations in supercooled liquids is a central goal of modern condensed matter phys-­‐ ics and a fundamental problem of non-­‐equilibrium statistical physics. I will show here that the use of liquid jets in combination with state-­‐of-­‐the-­‐art light sources offers a completely novel approach to study such complex non-­‐equilibrium phenomena at an unprecedented level of analysis, allowing one to deepen our understanding of the most challenging aspects of phase transformations in super-­‐ cooled liquids that are of paramount importance in a variety of research fields such as materials sci-­‐ ence or atmospheric physics.