Current status of the BaD-ElPh project at ELETTRA

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Current status of the BaD-ElPh project at ELETTRA
P. Vilmercati L. Petaccia S. Gorovikov M.
Barnaba C. Masciovecchio D. Cocco A. Bianco A.
Goldoni
1st Workshop on Ultraviolet Techniques and
Applications, October 8th-10th 2008 LNF,
Frascati.
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Outline
BaD-ElPh beamline (Band Dispersion and
Electron-Phonon coupling studies)

• photon source
• beamline
• experimental end station

Examples of experiments _at_ BaD-ElPh beamline

• experimental determination of the inelastic
  electron mean free path at KElt10eV
• electronic structure in a strongly correlated
  system

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Photon source Figure 8 undulator
Flux_at_ 10eV 200mA 1015 photons/s/0.1bandwidth
Two sets of harmonics, integer (i1,2,) and
half-integer (i1/2,3/2,), having horizontal
and vertical linear polarization, respectively.
B.Diviacco et al. "New Insertion Devices for
ELETTRA", proc. 2001 Particle Accelerator
Conference
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Beamline Layout a 4 meter NIM
Beam in
Energy range 4.6 - 26 eV with two gratings
(AlMgF2 - SiC) Photon flux 3x1012 photons/s _at_
8 eV (exit slit 150 µm) 6x1011 photons/s _at_ 19
eV (exit slit 300 µm) Resolving Power up to
about 50.000
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Gratings efficiency
AlMgF2 1.500 l/mm
Efficiency
SiC 3000l/mm
Pt soon available!
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Gratings resolving power
AlMgF2

• SiC

20 eV, resolving power 45000 (10 µm) 12 eV,
resolving power 75000 (10 µm) 8 eV, resolving
power 50000 (10 µm)
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Ar autoionization spectrum in the range 2P3/2
-2P1/2 recordered in first order light
Resolving power 28000 exit slit 50µm
12s
11s
13s
?E535µeV
9d
Ar 2P1/2
Ar 2P3/2
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Ne 14s Rydberg line recorded in second order
light
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Photon Flux at the end of the beamline
Measurements performed with a calibrated
photodiode set at the end of the beamline, just
before the experimental end-station.
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BaD-ElPh experimental end-station

• 4 axis manipulator with cryostat (15K with liquid
  He)
• Fast entry lock
• Preparation chamber
• Sputter gun
• Cleaver
• Heating stage
• several free flanges to mount evaporators
• Experimental chaber
• Phoibos 150
• X-ray (Al, Mg) and UV (He discharge) sources
• LEED

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Performances of the Phoibos 150 provided by SPECS
Energy resolution 3.94 meV obtained in Gas
Phase with Pass Energy 1.4eV in LAD mode.
Angular Resolution 0.2deg
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Experimental Performances of Phoybos 150
entrance slit 400µm exit slit 300µm
Ag Polycristal
f(x) c(abx)(1/(1exp((x-Ef)/(T/11604.5)))) c
676.29 4.09 a 20520 2.13e03 b
-2143.1 235 Ef 9.0996 0.000104 eV T
32.534 1.02 K
PE1eV
FWHM 9.8 meV
First derivative fit y y0 Aexp ( (x-x0) /
width)2 y0 1.8349 0.859 A 89.702
3.38 x0 9.0995 0.000178 width
0.0058939 0.000265
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Electon inelastic mean free path of low kinetic
energy electrons
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Inelastic mean free path the case of CoO.
The overlayer method
Photo-electrons
UV SR
insulator
metal
Offi, et al. PRB 77, 201101(R) 2008
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Evaluation of the Mean Free Path
Inelastic mean free path is reduced of a factor 6
with respect to theoretical predictions!
Offi, et al. PRB 77, 201101(R) 2008
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Phase transitions in Mott-Hubbard insulators.
(V1-xCrx)2O3 x0.011
Theoretical calculation predicts structures close
to Fermi level that have been observed only with
Hard X-Ray Photoemission.
hv 21 eV (He I)
M. Marsi et al. submitted.
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Bulk sensitivity!
Comparison with theoretical calculations
M. Marsi et al. submitted.
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Conclusions
WUTA 08, LNF
Conclusions

• The BaD ElPh beamline is now operating and users
  are welcome to apply for beamtime.

Thank you for your attention!
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Why a Figure 8 undulator?
Originally designed for soft X-rays _at_ Spring 8
(E8GeV)
UV-rays _at_ Elettra (E 2-2.4 GeV). Energy range
4.6eV (E2GeV), 6.7eV (E2.4GeV) 70eV (not used)
The power density is mainly distributed off-axis
can be screened with a suitable pinhole
aperture Reduced by a large factor the heat
load on optics
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Experimental setup for resolution measurements
Gas Cell setup
Ar, Ne
Pico Amp.
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Flux_at_ 10eV 200mA 1015 photons/s/0.1bandwidth