Frontiers in Science with FELs: The Project

Transcription

1 Frontiers in Science with FELs: The Project Fulvio Parmigiani Department of Physics University of Trieste & Laboratory Sincrotrone Trieste, Italy

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3 Si 2p Critical absorption edges ONLY LINEARLY POLARIZED RADIATION 1. 5 GeV 10nm 3nm 1.7nm 1nm 1. 8 GeV Pulse duration (fs) (FWHM) Photons/s/ 0.1% BW (r.r.50 Hz) 4.2 nm x nm x nm x10 14 C 1s N 1s O 1s Mn 2p Fe 2p Pulse duration (fs) (FWHM) Photons/ s/ 0.1% BW (r.r.50 Hz) 3 nm x nm x10 11 All L 23 of 3dTM 1 nm x10 9 D. Attwood-UCB

4 Objectives To perform experiments on magnetic imaging, magnetic manipulation, XMCD-XMLD and high energy/momentum and spin resolution photoelectron spectroscopy on the time scale of s. Artificially structured materials are of growing importance in modern life. The major scientific challenge is to understand the magnetization dynamics in these systems and to identify new directions that can overcome physical limitations: -magnetization of confined systems can be reversed within 100 ps: of special importance is to establish the fundamental limit of magnetization reversal (e.g., coherent acoustic spin waves can reduce the switching time to a few ps); -a spin-flip excitation in the valence shell of a material like Ni requires typically 0.1 ev; this translates into a time scale in the fs range. However very different time scales were reported so far, ranging from 100 fs to ps; -domain wall motion induced by applied currents: how the domain wall is deformed and how it moves with time; -time resolved magnetic microscopy imaging of spin dynamics of non-repetitive events: catching the spin dynamics within a single-shot image.

5 Ultrafast coherent imaging at Fermi Spokesperson: H. Chapman (LLNL-CA), J. Haidu (Stanford University and Uppsala University) Single-shot experiments H.N. Chapman et al.; Nat. Phys. 2, 839 (2006) and Physics Today, Jan 2007, pag. 19

6 March 2007 FLASH soft X-ray laser Hamburg, Germany FIRST FLASH DIFFRACTION IMAGE OF A LIVE PICOPLANKTON FLASH pulse length: 10 fs Wavelength: 13.5 nm RECONSTRUCTED CELL STRUCTURE J. Hajdu, I. Andersson, F. Maia, M. Bogan, H. Chapman, and the imaging collaboration Filipe Maia, Uppsala Resolution length on the detector (nm)

7 Available Instruments to measure Collective Excitations ω (mev) FP (Sandercock) BLS DMDP2000 V = 7000 m/s V = 500 m/s HIRESUV IUVS ESRF-BL21 IN5 IXS INS ESRF-BL Q ( nm -1 ) S(Q,ω) Dynamic Structure Factor S(Q,ω) (arb. units) Q = 0.04 nm -1 SiO 2 0-1,5-1,0-0,5 0,0 0,5 1,0 1,5 Brillouin shift (cm -1 ) F( Q,t) IUVS 14:00 Glycerol T=205 K

8 Transient Grating Spectroscopy at the Nanoscale Liquids - Fluids Transition from the Hydrodynamic to the Kinetic regime in Simple liquids and fluids. Effect of the Local Structure on the Relaxation Dynamics of Molecular liquids and H-bonded liquids. Sound Bifurcation in Gas Mixtures Thermal Relaxation Dynamics in Liquid Metals. Glasses Relaxational Processes in Super-Cooled liquids and their relation to the Glass Transition. Vibrational and Relaxational Low Temperature Properties of Fragile and Strong glasses. Characteristic Length of the Disorder Surface Dynamics Transverse Dynamics in Liquids. Phase Transition in thin Films. Polymers Structural Relaxations. Shear and Density Fluctuations. this regime is not accessible (< 500 nm) using visible light, and will allow sensitive probing of interfaces, extremely thin films, and heat transport and correlations in nanostructured materials. R. I. Tobey et al., APL 2006

9 Cluster and nanoparticle spectroscopy Spokespersons: F. Stienkemeier, B. von Issendorff (Univ. of Freiburg-D) Co-proponents :K.Fauth (MPI- Stuttgart, D), M. Drabbels (EPFL- CH), M. Schmidt(CNRS Orsay, Fr), U.Buck (MPI-Goettingen, D)

10 Magnetization Dynamics FERMI-FEL2

11 FEL2+ and variable polarization :X-ray Dichroism

12 Probing the Properties of Magnetic Materials Magneto Optical Kerr Effect in the Visible Ni Beaurepaire et al., PRL 76, 4250 (1996) Non-Equilibrium Magnetization Dynamics: transfer of energy and angular momentum Optical Excitation Electrons Lattice Pressure Magnetic field or Spin injection Spin Magnetism: From Fundamentals to Nanoscale Dynamics, J. Stohr & H.C. Siegmann Stamm et al., Nature Mat. 6, 740(2007)

13 New experiments - Magnetization Dynamics Coherent photon scattering: speckle spectroscopy Coherency of FEL: scattering of coherent photons produces a two-dimensional intensity distribution called speckle pattern. With FEL a speckle pattern can be taken within a single FEL pulse opening the way to single snapshot dynamic experiments. MLXD and CMXD provide the contrast mechanism for the scattering of domains in magnetic systems. X-ray spectro-holography (BESSY-II) Interference pattern (hologram) 2D FFT S. Eisebitt et al., Nature 432, 885 (2004)

14 Photo-induced and Magnetic Field-induced Phase Transitions Photo-induced and magnetic field-induced insulator-to-metal transition Photo-induced isothermal magneto-structural phase transition and magneto-resistance For H > 5 Tesla, T< 30 K

15 BESSY II fs slicing source 3 rd harmonic 10 3 (ph s %BW)

16 Main FEL photon parameters to be considered The primary interest for the users of FERMI is to extend the photon energy upwards toward 1 kev as much as possible with variable polarization. While the initial physics requirement remains 40 nm 10 nm, the user program foreseen strongly suggests FEL design choices that will enable operation at < 10 nm (120 ev) at the earliest possible date. The second priority for the updated the experimental plan is to require a time structure for the pulses in the range from fs. Even shorter duration pulses are of interest if attainable (with >10 9 photons/pulse/mev). Jitter in the pulse arrival time should be fs or less with a goal <10% of the pulse duration. The third priority requirement is that the peak resolving power in experiments should be in the range from Therefore, the natural bandwidth (rms) of the FEL output (for long pulses) should be in the range of 5 15 mev. The FEL output radiation should be easily (and rapidly) tunable over the range of 5 10 % of the central output wavelength. An acceptable compromise for the user program will be to produce short radiation pulses (< = 100 fs), that will serve the large majority of the planned experiments, and to monochromatize the output radiation if and when narrow bandwidth is required experimentally. Of course, monochromatization is performed at the cost of losing photon intensity.

17 FEL 2+ : main photon beam parameters

18 Worse-Case Estimate of Circularly-Polarized Harmonic Emission Off-axis emission from purely helical undulator (destructive interference effects) Adapting Geloni et al. s analysis to a high gain amplifier reaching saturation P h = 2 P fund f b ( ( h = 2 ) ) 2 π 2 1 k w Z R ( h = 1) : O ( ) ~ Rough analytic estimates suggest for h=3, another factor ~ (4 kwzr) -1 appears # photons s -1 (r.r. = 50 Hz) Fundamental Wavelength / Energy 3 nm 413 ev # photons/pulse fundamental 4.2E+11 Harmonic Wavelength / Energy 1.5 nm (h=2) 826 ev 1 nm (h=3) 1240 ev # photons / pulse harmonic 1.7E E+7 5 nm 248 ev 3.2E nm (h=2) 496 ev 1.66 nm (h=3) 744 ev 1.2E E E+5

19 Actual beamlines and photon diagnostics Shutters FEL 1 FEL 2 Slits Gas cell I0 monitors 2.5 Plane mirrors Safety Hutch 5 EIS switching LDM Monochromator Spectrometer D. COCCO Dealy lines KB system FEL 2 beamline LDM Diproi EIS There will be the possibility to measure the following characteristics. Intensity: on line; shot by shot; 1% repeatability, 2-3% precision (calibration dependent) Angular position: on line; shot by shot; ~ 2 mrad sensibility. Divergence: NOT on line; NOT shot by shot; based on YAG crystal measurements Photon energy distribution: on line; shot by shot. Single spectrometer, ev sub mv resolution. Arrival time: on line; shot by shot; Visible streak camera (Timing and Synchronization Area) ps resolution. Wavefront: Hartmann sensor (Imagine Optic), Precision l/50 at 20-5 nm range or CCD. Pulse length measurement: NOT on line; NOT shot by shot. ALS-Highlights-2008 Streak Camera FERMI-Hamamatsu collaboration FERMI responsible: M. ZANGRANDO

20 Estimated LP photon the sample Green: 3 rd /5 th harmonics White: Fundamental (1 st harmonic) RED: Start 2 End simulation April 2009 Calculated by D. Cocco LDM beamline photon flux DIPROI beamline photon flux 20

21 TR-Magnetic Experiments BL Shutters FEL 1 FEL 2 Slits Gas cell I0 monitors 2.5 Plane mirrors 1.5 Safety Hutch 5 EIS switching LDM Monochromator Spectrometer Dealy lines KB system FEL 2 beamline LDM Diproi EIS EIS pipes 1 m FEL 2 line

22 Magnetic dynamics beamline flux ONLY LP Photons D. COCCO CP Photons LINAC: 1.5 GeV (rr 50 Hz) fundamental hν = 248 ev (5 nm) Worse-Case LINAC: 1.8 GeV (rr 50 Hz) fundamental hν=413 ev (3 nm) 3 harmonic hν = 744 ev (1.66 nm) 2 harmonic hν=826 ev (1.5 nm) flux@source 2.5x10 5 photons s -1 flux@source 8.5x10 7 photons s -1 flux@sample 3.25x10 4 photons s -1 flux@sample 1.5x10 7 photons s -1 W. FAWLEY 22

23 Pump-probe experiments on BACH SincroLock 50 fs R.R. 250 KHz λ=800 nm OPA: nm DFG: µm 5 W MIRA seed in scatola Mira 900 Stretcher/compressor OPA DFG Verdi V18 18 W RegA W SincroLock MIRA HP Pulse picker 1-10 MHz 800 nm, 120 fs on Bi MHz T*< Tc T*>Tc

24 New experiments - TR-XMCD Superconductivity and Ferromagnetism Experiment proposed by M. Zacchigna H vs T phase diagram for (H 2 O) Cobaltites. Open and closed circles represent T c and magnetic ordering Temperature PROBE PUMP Nature, 2007

25 TR-XAS a nd TR XMCD on manganites: testing the polarons? Dichroism 1.10x10-3 La0.85Na0.15MnO3 H = 3T Dichroic signal m totale (emu) Comparison with SQUID Temperature (K) m spin = 6 (µ µ ) + dω 4 (µ L3 + µ ) dω L3+L2 n hole µ + + µ ) m n orb hole 4 = 3 L3+ L2 L3+ L2 ( µ µ ) + ( µ + µ ) + ( L3+L2 Energy (ev)

26 Test of the SR-TR ToF on the Au(111) surface states TR- and AR-Photoemission Time and Spin resolved experiments Fermi surface mapping 1 2c Spin-orbit coupling = S ( V ) H SO r r r 2 p r V ) = V ( r, z) + V ( r, z)sin 3ϕ + V ( r, )cos6ϕ ( z r r r V = α z + β u ϕ r p = r p u r H SO p r r r r = ( α S uϕ + β cos3ϕ S u c 2 2 z ) u rϕ ϕ z r u r r Osterwalder et al. PRB 69, R, 2004)

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28 Synchronization and detection system for Synchrotron: TR XMCD SS Spin radial component ± 7T, 2K cryostat H SO H SO 1 r r r = S ( V p) 2 2c p r r r r = ( α S u + β cos3ϕ S u ) 2c 2 ϕ z u rϕ ϕ z r u r r SR LS LS = 83.3 MHz SR = 500MHz 40ps Ready for experiments Hamamatsu MCP detector 2ns Assembling starts May Commissioning before end 2009

29 Conclusions By extending the LINAC energy up to GeV it is possible to generate a significant photon flux ( > 10 8 photon s -1 on the sample) up to ~ 1 kev photon energy for LP light pulses with a time structure < 100 fs FWHM. The intensity for elliptically polarized light between 0.5 kev and 1 kev is quite reduced compared to the LP case but, even for the worse conditions, simulations suggest that is possible to obtaining on the sample a photon flux larger than that required for TR-magnetic dynamics studies ( see results from BESSY II EP ~ 100 fs slicing source). In house TR-magnetic dynamics TR-XMCD on BACH (commissioning II semester 2009). TR-dichroic experiments with HHG at the Fe and Ni M 2,3 threshold started. TR-Spin dynamics open for experiments. Soft-X ray streak-camera with < 0.5 ps time resolution, commissioning May 2009.

30 Thanks: Daniele Cocco Marco Zangrando Barbara Ressel Goran Zgrablic Alberto Simoncig Michele Pasqualetto Andrew Aquila David Attwood Marco Malvestuto Luigi Stebel Federica Bondino Cephise Cacho Elaine Seddon TIFF (Uncompressed) decompressor TIFF (Uncompressed) decompressor