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Current status of the BaD-ElPh project at ELETTRA

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. 1 st Workshop on Ultraviolet Techniques and Applications, October 8 th -10 th 2008 LNF, Frascati. WUTA 08, LNF. Outline.

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Current status of the BaD-ElPh project at ELETTRA

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  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. WUTA 08, LNF Outline 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

  3. WUTA 08, LNF Photon source: Figure 8 undulator 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

  4. 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

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

  6. WUTA 08, LNF Energy (eV) 8.27 6.2 4.96 12.4 24.8 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)

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

  8. WUTA 08, LNF -15 Ne 14s' Rydberg line 200x10 recorded in second order exit slit = 20 m m entrance slit = 400 m m m FWHM = 156 eV Curr0908_044 fit_Curr0908_044 gauss E/DE = 68000 150 Total Ion Yield (A) 100 50 0 10.7878 10.7880 10.7882 10.7884 10.7886 10.7888 Photon Energy (eV) Ne 14s’ Rydberg line recorded in second order light

  9. 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. 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. 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. WUTA 08, LNF 1800 1600 1400 Intensity (Arb. Units) 1200 1000 800 600 9.070 9.080 9.090 9.100 9.110 9.120 9.130 100 Kineitc Energy (eV) 80 60 1st derivative of intensity (arb. units) 40 20 0 -20 9.07 9.08 9.09 9.10 9.11 9.12 9.13 Kinetic Energy (eV) Experimental Performances of Phoybos 150 entrance slit = 400μm exit slit = 300μm 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 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

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

  14. WUTA 08, LNF Cobalt oxide Silver 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

  15. 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

  16. WUTA 08, LNF métal 200K isolant 300K Ag -2.0 -1.5 -1.0 -0.5 0.0 binding energy (eV) 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) M. Marsi et al. submitted.

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

  18. Conclusions WUTA 08, LNF 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. Acknowledgements This project was financed by MIUR (Italian Ministry for University and Research) and Sincrotrone Trieste. Conclusions • The BaD ElPh beamline is now operating and users are welcome to apply for beamtime. Thank you for your attention!

  19. WUTA 08, LNF Why a Figure 8 undulator? 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

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

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

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