Overview

With the advent of 4th generation free electron laser (FEL) light sources, which provide ultra-short pulses and high photon numbers per pulse in the VUV to X-ray wavelength range, a wide variety of topics from condensed matter physics to plasma physics becomes now accessible for the first time.

The aim of the TIMEX project is the design and construction of an end-station to investigate metastable and/or excited states of matter under extreme conditions at the Italian FERMI@Elettra free electron laser facility.

The instrument, recently funded through a collaboration between the:

  • ELETTRA synchrotron radiation facility in Trieste
  • X-ray Absorption Spectroscopy (XAS) group at the University of Camerino

  • will exploit the unique intensity, energy domain and time structure of the FEL radiation delivered by the FERMI@Elettra source.

    The energy and intensity of the Fermi@Elettra FEL beam is suitable for an efficient ultrafast heating of most bulk-like dense samples. We intend to exploit this unique source for two classes of experiments:

    1. creation and investigation of warm dense matter (WDM)
    2. phase transitions occurring in metastable states under extreme conditions

    The TIMEX end-station has been developed through a collaboration between the University of Camerino ( XAS group ) and Sincrotrone Trieste and is in course of installation at the Elastic and Inelastic Scattering (EIS) beamline, under construction at the FERMI@Elettra FEL facility.

    Scientific topics

    A first topic concerns the creation and characterization of warm dense matter, a region of the density-pressure phase diagram between solids and plasmas where both the standard theories of condensed matter physics and/or plasma statistical physics are invalid. Such a regime is found in planetary interiors, cool dense stars, and in every plasma device where one starts from a solid, e.g., laser-solid-matter-produced plasma, as well as all inertial fusion schemes. The FEL VUV/soft x-rays pulses in the 10-100 eV range are able to raise solid matter at temperatures up to 10 eV in very short times compared to hydrodynamic expansion, in a way yet unachievable with other sources such as high-power infrared and visible light lasers. Experiments aimed at investigating physical properties of WDM such as optical/UV reflectivity, transmitted energy, etc will be performed using also ultrafast optical probes or the FEL harmonics.

    A second important research objective of the project exploits the timescales involved in the FEL beam (0.1-1ps range) to access regions of metastable liquid regime presently unaccessible. The FEL beam will be used to isochorically heat amorphous systems (deposited from the vapor phase) into the metastable liquid state at a temperature where the nucleation rate is much higher than in any possible cooling experiment (no man's land). It will be therefore possible to follow the time evolution of this state, for example by optical-near UV reflectivity measurements. We expect to be able to detect the sample crystallization onset and measure nucleation rate and other properties of the metastable liquid before nucleation in a region presently unaccessible.

    Status

    The first TIMEX "first-shot" activities (runs in March and in July 2011) will be mainly devoted to the commissioning and tuning of the end-station. The TIMEX end-station has been tested during the first days of operation of the FEL1 source (March 2011). We have measured a photon fluence compatible with the expected performances of the source at this stage of commissioning. Pilot single-shot pump and probe experiments with a laser source are also being carried out.

    Set-up

    TIMEX layout

    Sketch of the TIMEX end-station under commissioning at the FERMI@Elettra FEL facility. The side view shows all the optical elements up to the sample chamber, most of them presently under construction. In the top view on the left side of the figure we show the main components of the end-station along with their distances from the sources. In the top view, right side, we show the details of the focusing and aligning devices and the detectors used for reflection and transmission measurements using both the FEL and a probe pulse of an optical laser.

    Publication list

    Highlights

    Elettra
    FERMI
    UNICAM
    TIMEX_chamber "Tightening the screws... " Assembling and vacuum test of the TIMEX chamber (Bencivenga, Filipponi, Carino, D'Amico)
    Fermi exp. hall Fermi experimental hall - first days (17 nov 2010)
    Timex end-station
    First temporary installation of the TIMEX chamber at the exit of the FEL1 source. The FEL beam (yellow dashed line, guide for the eye) is aligned up to the main TIMEX chamber (17 March 2011).