TIMEX project homepage 
(@University of Camerino - ITALY)

The expected capabilities of the Fermi@Elettra source to deliver 0.01-1 ps pulses in the 10-1000 eV range open the way to investigations of the fundamental properties of condensed matter under non equilibrium thermodynamic conditions with an unprecedented temporal resolution, which allows us to access fast dynamical process at the nanometre scale. The aim TIMEX is the construction of an instrument for investigating materials under extreme and excited or metastable conditions. The main idea is to use the FEL beam within a pump-probe scheme for time-resolved studies of the optical and soft x-ray properties of matter providing direct information on surfaces and bulk under extreme conditions. Such experiments in the 0.1-10 ps range are relevant to a variety of physical and chemical phenomena including high-pressure and high-temperature phase transition, non-equilibrium and metastable states of matter, applied material studies, understanding of chemical reaction and catalysis paths, planetary interiors, inertial fusion, and various forms of plasma production in which energy is rapidly deposited into a solid. The main TIMEX scientific objectives will be ultrafast studies (conductance, reflectivity, transmission, scattering) of i) warm dense matter (WDM); ii) transitions occurring in stable, metastable and excited states under extreme conditions. Materials and techniques will be selected in view of the specific expected characteristics of the source. The primary difficulties in studying these physical phenomena and states of matter are that the timescales for changes are rapid (within few ps) whereas the matter, being dense, cannot be probed by the usual short-pulse visible laser techniques. Interest in understanding the properties of warm dense matter is related to the actual conditions occurring in most planets and star interiors. Approaching these states in a laboratory experiment is a crucial challenge to pursue. The little progresses made so far in laboratory experiments (see for example [1] and ref. therein) are mirrored in the astrophysical literature where the WDM regime is found, for example, in the structural formation of large planets and brown dwarfs [2]. Present experimental data are scattered and largely based on single-shot shock-wave techniques while ultrafast isochoric heating obtained using the FEL beam is able to sample wide regions in still unexplored extreme conditions. Our calculations show that efficient isochoric heating up to temperatures of 10 eV can be obtained for bulk-like samples using the FERMI radiation. A second important physical problem that will be tackled using TIMEX concerns the study of phase transitions involving metastable states occurring in regions that are presently inaccessible. An important example is the occurrence of polymorphism and the hypothesis about the existence of a coexistence line and a critical point separating low-density and high-density fluids in a class of substances which include water, C, Ge, Si and their oxides (see for example [3]). In spite of the fundamental importance of these phenomena, the transition region often is located in a no man's land where crystallization of the undercooled liquid or of the glassy phase prevents observation of the fluid structure transformation. Due to the ultrafast bulk heating nature of the pump, a simple experiment using the FERMI beam will give access to what is presently a no man's land in simple liquid and glasses like water, C, Ge, Si shedding light on the nature of the fluid and on the dynamics of recrystallization.


Updated information on the TIMEX end-station can be found at the website of the TIMEX collaboration.



[1] R. W. Lee, et al., J. Opt. Soc. Am. B 20 , 770 (2003). 

[2] H. M. Van Horn, Science 252 , 384 (1991); H. M. Smoluchowski, Nature 215, 691 (1967); W. B. Hubbard,Science 214, 145 (1981). A. M. Linderberg and et al., Science 308, 392 (2005). 

[3] Poole et al., Nature 360, 324 (1992); Mishima et al. Nature 396, 329 (1998). 


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Ultima modifica il Mercoledì, 30 Marzo 2011 10:30