Delay-Line Imaging and XPCS

Transcription

1 . Delay-Line Imaging and XPCS Gerhard Grübel W.Roseker, F. Lehmkühler, L. MüIler, S. Schleitzer, M. Berntsen, H. Schulte-Schrepping, M. Walther DESY Deutsches Elektronen Synchrotron, Notkestr. 85, Hamburg, Germany

2 How to measure sub-ns dynamics with an FEL? Pulse spacing: 8.3 ms (LCLS), 16.6 ms (SACLA), 200 ns during 0.6 ms (E-XFEL) permits also x-pump x-probe Compatible 2D detector Gerhard Grübel XBSD Workshop, January 28, 2014 Page 2

3 Split-and delay unit(s) Gerhard Grübel XBSD Workshop, January 28, 2014 Page 3

4 Application(s) for soft X-ray split-and delay unit(s) Diagnostics coherence time pulse length Fluctuations in magnetic systems ultrafast switching in transmission metal systems (Co,..) Sequential fs Imaging Non-equilibrium phenomena (x-ray) pump -- probe Gerhard Grübel XBSD Workshop, January 28, 2014 Page 4

5 . Coherence properties of the FLASH FEL A. Singer, F. Sorgenfrei, A. P. Mancuso, N. Gerasimova, O. M. Yefanov, J. Gulden, T. Gorniak, T. Senkbeil, A.Sakdinawat, Y.Liu, D. Attwood, S. Dziarzhytski, D. D. Mai, R. Treusch, E. Weckert, T. Salditt, A. Rosenhahn,W. Wurth, and I. A. Vartanyants OPTICS EXPRESS, 20/ (2012) Gerhard Grübel XBSD Workshop, January 28, 2014 Page 5

6 Spatio-temporal coherence. properties of FEL pulses Two beam interference: fringe spacing = / sin coherence length l c = sqrt(2ln2/ ) ( 2 / ) coherence time c = sqrt(2ln2/ ) ( 2 / )/c FLASH: = 24 nm = mrad c = 7.5 fs R. Mitzner, B. Siemer, M. Neeb, T. Noll, F. Siewert S. Roling, M. Rutkowski, A.A. Sorokin, M. Richter, P. Juranic, K. Tiedtke, J. Feldhaus, W. Eberhardt, and H. Zacharias OPTICS EXPRESS 16 (2008) LCLS: = nm = 1 rad (137 m spacing) expect: c = 24 fs Gerhard Grübel XBSD Workshop, January 28, 2014 Page 6

7 Pulse-length measurements Double ionization of He : E= at 51.8 FLASH Find pulse-length of 29(5) fs Gerhard Grübel XBSD Workshop, January 28, 2014 Page 7

8 Ultrafast Demagnetization. Time delay Magnetization Gd (100+/-80 ps) via time resolved photoemission A. Vaterlaus et al., PRL 67, 3315 (1991) Time-resolved MOKE (Ni 120 fs) E. Beaurepaire et al., PRL 76 (1996) 4250 Gerhard Grübel XBSD Workshop, January 28, 2014 Page 8

9 IR pump X-ray Probe B. Pfau et al., Nature Communications, Vol. 3, 11; DOI:doi: /ncomms2108 (2012) L.Müller et al., Rev. Sci. Instrum. 84, (2013) Fluctuations about the average de- and re-magnetization behaviour? Gerhard Grübel XBSD Workshop, January 28, 2014 Page 9

10 X-ray Photon Correlation Spectroscopy (XPCS) Beam splitting is accomplished using 20 um thin Si crystals quantify dynamics in terms of the intensity correlation function g 2 (Q,t): g 2 (Q,t) = <I(Q,0) I(Q,t)> / <I(Q)> 2 Eight Si(422) perfect crystals arranged in 90 o geometry g 2 (Q,t) = 1 + ß(Q) f(q,t) 2 with f(q,t) = F(Q,t) / F(Q,0) F(Q,0): static structure factor Δt max=3.5 ns Gerhard Grübel XBSD Workshop, January 28, 2014 Page 10

11 Split-and-delay XPCS Beam splitting is accomplished using 20 um thin Si crystals Eight Si(422) perfect crystals arranged in 90 o geometry Δt max=3.5 ns Gerhard Grübel XBSD Workshop, January 28, 2014 Page 11

12 Sequential fs Imaging Per shot get: Image(t) + Image (t+ t) Vary t Gerhard Grübel XBSD Workshop, January 28, 2014 Page 12

13 X-pump. - X-probe experiments X-Ray Pump X-ray Probe X-ray Pump X-ray Probe experiment on PMMA particles in decalin Probe/Pump = 1/30 Pump + Probe Δt = 2.2 ns Probe Gerhard Grübel XBSD Workshop, January 28, 2014 Page 13 28

14 Parameters Wish List Day 0 Experimental techniques Source properties Energy range M to L edges (transition metals) Pulse duration as short as possible bandwidth Device properties Maximum Temporal delay 20 ps Pulse intensity ratio variable 2 Colors Yes Symmetric delay around t=0 Yes (get experimental t 0 ) Spatial separation behind sample yesno Nice to have Add your suggestions Gerhard Grübel XBSD Workshop, January 28, 2014 Page 14

15 . The end Gerhard Grübel XBSD Workshop, January 28, 2014 Page 15