1. 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.

2. Outline BaD-ElPh beamline Examples of experiments @ BaD-ElPh beamline
WUTA 08, LNF
BaD-ElPh beamline
(Band Dispersion and Electron-Phonon coupling studies)
photon source
beamline
experimental end station
Examples of BaD-ElPh beamline
experimental determination of the inelastic electron mean free path at KE<10eV
electronic structure in a strongly correlated system

3. Photon source: Figure 8 undulator
WUTA 08, LNF
10eV 200mA: 1015 photons/s/0.1bandwidth
Two sets of harmonics, integer (i=1,2,…)
and half-integer (i=1/2,3/2,…), having
horizontal and vertical linear polarization, respectively.
B.Diviacco et al. : "New Insertion Devices for ELETTRA", proc Particle Accelerator Conference

4. Beamline Layout: a 4 meter NIM
WUTA 08, LNF
Beamline Layout: a 4 meter NIM
Beam in
Energy range: eV with two gratings (AlMgF2 - SiC)
Photon flux: 3x eV (exit slit 150 µm)
6x eV (exit slit 300 µm)
Resolving Power: up to about

5. Gratings efficiency Energy (eV) AlMgF2 1.500 l/mm Efficiency SiC
WUTA 08, LNF
Gratings efficiency
15.5
10.0
7.0
5.0
23.0
41.0
Energy (eV)
AlMgF2
1.500 l/mm
Efficiency
SiC
3000l/mm
Pt: soon available!

6. Gratings resolving power
WUTA 08, LNF
Gratings resolving power
24.8
12.4
8.27
6.2
4.96
Energy (eV)
+ AlMgF2
SiC
20 eV, resolving power (10 µm)
12 eV, resolving power (10 µm)
8 eV, resolving power (10 µm)

7. Resolving power = 28000; exit slit =50μm
WUTA 08, LNF
Ar autoionization spectrum in the range 2P3/2 -2P1/2 recordered in first order light
Resolving power = 28000; exit slit =50μm
1.0x10
-12
0.8
0.6
0.4
0.2
Total Yield (A)
15.88
15.84
15.80
15.76
15.72
Photon Energy (eV)
12s’
11s’
13s’
ΔE=535μeV
9d’
Ar 2P1/2
Ar 2P3/2

8. Ne 14s’ Rydberg line recorded in second order light
WUTA 08, LNF
Ne 14s’ Rydberg line recorded in second order light
200x10
-15
150
100 50
Total Ion Yield (A)
Photon Energy (eV)
Curr0908_044
fit_Curr0908_044 gauss
exit slit = 20 m
entrance slit = 400
FWHM = 156 eV
E/DE = 68000
Ne 14s' Rydberg line
recorded in second order

9. Photon Flux at the end of the beamline
WUTA 08, LNF
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.

10. BaD-ElPh experimental end-station
WUTA 08, LNF
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

11. Performances of the Phoibos 150 provided by SPECS
WUTA 08, LNF
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

12. Experimental Performances of Phoybos 150
WUTA 08, LNF
Experimental Performances of Phoybos 150
entrance slit = 400μm
exit slit = 300μm
1800
1600
1400
1200
1000
800
600
Intensity (Arb. Units)
9.130
9.120
9.110
9.100
9.090
9.080
9.070
Kineitc Energy (eV)
Ag Polycristal
f(x) = c+(a+b*x)*(1/(1+exp((x-Ef)/(T/ ))))
c = ± 4.09
a = ± 2.13e+03
b = ± 235
Ef = ± eV
T = ± K
PE=1eV
100 80 60 40 20
-20
intensity (arb. units)
1st derivative of
9.13
9.12
9.11
9.10
9.09
9.08
9.07
Kinetic Energy (eV)
FWHM = 9.8 meV
First derivative fit
y = y0 + A*exp ( (x-x0) / width)2
y0 = ± 0.859
A = ± 3.38
x0 = ±
width = ±

13. Electon inelastic mean free path of low kinetic energy electrons
WUTA 08, LNF
Electon inelastic mean free path of low kinetic energy electrons
Electron Kinetic Energy (eV)
Inelastic Mean Free Path ( Å)

14. Inelastic mean free path: the case of CoO.
WUTA 08, LNF
Inelastic mean free path: the case of CoO.
The “overlayer” method
Photo-electrons
UV SR
Silver
Cobalt oxide
insulator
metal
Offi, et al. PRB 77, (R) 2008

15. Evaluation of the Mean Free Path
WUTA 08, LNF
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, (R) 2008

16. Phase transitions in Mott-Hubbard insulators.
WUTA 08, LNF
Phase transitions in Mott-Hubbard insulators.
(V1-xCrx)2O3 x=0.011
Theoretical calculation predicts structures close to Fermi level that have been observed only with Hard X-Ray Photoemission.
hv = 21 eV (He I)
-2.0
-1.5
-1.0
-0.5
0.0
binding energy (eV)
métal 200K
isolant 300K Ag
M. Marsi et al. submitted.

17. Bulk sensitivity! Comparison with theoretical calculations
WUTA 08, LNF
Bulk sensitivity!
Comparison with theoretical calculations
M. Marsi et al. submitted.

18. Thank you for your attention!
Conclusions
Conclusions
WUTA 08, LNF
The BaD ElPh beamline is now operating and users are welcome to apply for beamtime.
Future perspectives
the third Pt grating will be installed in the first semester of 2009 in order enlarge the photon energy range up to 40eV.
a new 5 degree of freedom manipulator is under construction.
This project was financed by MIUR
(Italian Ministry for University and Research)
and Sincrotrone Trieste.
Acknowledgements
Thank you for your attention!

19. Why a Figure 8 undulator?
WUTA 08, LNF
Originally designed for soft Spring 8 (E=8GeV)
Elettra (E = GeV).
Energy range: 4.6eV (E=2GeV), 6.7eV (E=2.4GeV) ~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

20. Experimental setup for resolution measurements
WUTA 08, LNF
Experimental setup for resolution measurements
Gas Cell setup
Ar, Ne
Pico Amp.

21. Flux@ 10eV 200mA: 1015 photons/s/0.1bandwidth