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.

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 experiments @ BaD-ElPh beamline experimental determination of the inelastic electron mean free path at KE<10eV electronic structure in a strongly correlated system

Photon source: Figure 8 undulator WUTA 08, LNF Flux@ 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. 2001 Particle Accelerator Conference

Beamline Layout: a 4 meter NIM WUTA 08, LNF Beamline Layout: a 4 meter NIM Beam in Energy range: 4.6 - 26 eV with two gratings (AlMgF2 - SiC) Photon flux: 3x1012 photons/s @ 8 eV (exit slit 150 µm) 6x1011 photons/s @ 19 eV (exit slit 300 µm) Resolving Power: up to about 50.000

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!

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 45000 (10 µm) 12 eV, resolving power 75000 (10 µm) 8 eV, resolving power 50000 (10 µm)

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

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) 10.7888 10.7886 10.7884 10.7882 10.7880 10.7878 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

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.

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

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

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/11604.5)))) c = 676.29 ± 4.09 a = 20520 ± 2.13e+03 b = -2143.1 ± 235 Ef = 9.0996 ± 0.000104 eV T = 32.534 ± 1.02 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 = 1.8349 ± 0.859 A = 89.702 ± 3.38 x0 = 9.0995 ± 0.000178 width = 0.0058939 ± 0.000265

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)

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, 201101(R) 2008

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, 201101(R) 2008

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.

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

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!

Why a Figure 8 undulator? WUTA 08, LNF Originally designed for soft X-rays @ Spring 8 (E=8GeV) UV-rays @ Elettra (E = 2-2.4 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

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

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