The EIS-TIMER instrument is purposely designed to exploit the time structure, coherence properties and harmonic content/multi-color operation of the FERMI FEL source in order to carry out extreme ultraviolet/soft x-ray transient grating (XTG) experiments. In such kind of experiments two non-collinear FEL pulses (pump-A and pump-B) are overlapped, in time and space, at the sample to generate an interference pattern with a spatial periodicity in the 2-200 nm range. The dynamical response to such a nanoscale modulation, imposed by the XTG excitation, is monitored via transient diffraction of a third, time-delayed, FEL pulse pulse (probe). The XTG signal encodes information on several kinds of dynamics, ranging from transport processes (e.g. spin and heat diffusion) to collective lattice excitations (e.g. phonons) and fast electron dynamics; all this with the wavevector selectivity imposed by the XTG pattern. 

The implementation of this experimental scheme, nowadays used only with optical lasers, to the EUV/soft x-ray range allows probing lattice dynamics in the mesoscopic regime (10's of nm wavelength range) that cannot be accessed by available instruments. This capability is expected to be of the highest relevance for studying, e.g., the physics of disordered solids and nanoscale heat transport, which is crucial aspects for forefront nanoelectronics. The XTG approach can be also used to study other kind of nanoscale dynamics, as for isntance magnetic excitations or structural relaxation in liquids. 

In a broader context, XTG experiments is a specific application of EUV/soft x-ray four-wave-mixing (XFWM). The exploitation of this broader class of light-matter interactions has been so far conceived only theoretical, pointing out a great potential in a manifold of applications. Indeed, XFWM-based spectroscopies based on the exploitation of the elemental/chemical selectivity (provided by EUV/soft x-ray absorption edges) could be a unique experimental tool to gain information on coherences between vibrational, valence and core excitations, which are critical for understanding, e.g., charge and energy transfer dynamics in light harvesting or emitting devices.

 

Additional Lightsources

Seed Laser for Users (SLU)

Laser type
Ti:Sapphire
Central Wavelength/Energy
795 [nm]
Wavelength fluctuations
1 * 10-3 [%]
Spectral Bandwidth FWHM
18 [nm]
Tunability
1 [%]
Beam shape
Gaussian
Other beam shape
M2<1.5
Pulse duration FWHM
65 [fs]
Polarisation
Linear Horizontal, Linear Vertical, Circular
Other polarisation
All linear and circular polarizations available
Pulse repetition rate
50 [Hz]
Maximum pulse energy
1.5 * 10-3 [J]
Pulse energy fluctuations
5 * 10-3 [sigma]
Peak power
20 * 109 [W]
Peak fluence on target
10 [J/cm2]
Special modes
2nd and 3rd harmonics (~390 and ~260 nm) available
Endstations or Setup

EIS-TIMER

Spectrometer
None
Base Pressure
7 * 10-7 [mbar]
Detectors Available
Balanced photodiode
PI-MTE
Endstation Operative
Yes

Sample

Sample Type
Crystal, Amorphous
Required Sample Size
X = 1000 [um], Y = 1000 [um], Z = 0.1 [um]
Required Sample Volume
1 * 10-4 [uL]

Manipulator or Sample stage

Degrees Of Freedom
7
Cradles
1
Detectors

Balanced photodiode

Type
Balanced photodiode
Description
Balanced photoreceiver, 8 mm Silicon Detector, 400-1070 nm, 1 MHz ; commercial device (Newport Corp., Model: 2307)
Passive or Active (Electronics)
Active

Detection

Detected Particle
Photon

PI-MTE

Type
in vacuum, windowless CCD (for optical/EUv/x-rays)
Description
Commercial device (by Princeton Instruments) ; possible to add Al(200 nm thick), Zr(150 nm thick) or Pd(150 nm thick) filters
Pixel Size
X = 13.5 [um], Y = 13.5 [um]
Array Size
X = 2048 [pixel], Y = 2048 [pixel]
Passive or Active (Electronics)
Active

Detection

Detected Particle
Photon

PIXIS

Type
CCD camera (optical photons)
Description
Commericial device (by Princeton Instruments)
Pixel Size
X = 20 [um], Y = 20 [um]
Array Size
X = 1340 [pixel], Y = 100 [pixel]
Passive or Active (Electronics)
Active

Detection

Detected Particle
Photon
contacts
Filippo Bencivenga (BL scientist)
Riccardo Mincigrucci (post-doc)
Laura Foglia (post-doc)
Techniques
Absorption
  • Time-resolved studies
Emission or Reflection
  • Time-resolved studies
Scattering
  • Coherent scattering
  • Inelastic scattering
  • Time-resolved scattering
control/Data analysis
Control Software Type
  • TANGO
Data Output Type
  • Tensors of rank 0 - 3
Data Output Format
  • HDF
Softwares For Data Analysis
  • Matlab, Python and Igor (users use/develop their own codes)
Equipment That Can Be Brought By The User
Overall the instrumental layout is not particularly flexible, since the special design for XTG/XFWM applications resulted in some strict constraints. The installation of a user-supplied sample preparation chamber, cryostat or injector (in place of the standard sample holder/manipulator) and EUV/soft x-ray spectrometer (at some fixed angles) has been grossily evaluated and is likely possible. More complex setups for manipulating/detecting optical pulses can be accomodated. The standard (in-vacuum) EUV TG breadboard can be substituded by a user-supplied setup.
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