Laser-based THz Streaking - PowerPoint Presentation

1. Laser-based THz Streaking5th Annual X-ray FEL Collaboration Meeting, SLACAdrian CavalieriFeb 5th, 2013

2. X-ray Pulse Characterization by THz Streaking Overlap streaking and X-ray pulses on single-cycle THz ramp in gas jet X-ray induced photoemission is streakied by THz field Spectral peak is shifted and broadened. Shift gives arrival time information. Degree of broadening gives temporal extent. Arrival & temporal profile of arbitrary pulse can be recovered.

3. All single-shots displayed Interaction in Helium (isolated line) 0.3nC bunches; ~260eV; ~10µJ/pulseStreaking Spectrogram at FLASHMaximum KE shiftMinimum broadeningHigh time resolutiontemporal profile, jitter~ 60 eV~ 660 fs

4. Single-Shot FEL Pulse ProfileMeasurement accuracy ~5fs FWHMTemporal resolution ~45 fs FWHMcalculated statistical error at each data pointGenerate error envelopeDeconvolve energy resolution from signal, upper and lower envelope boundMap to time for limits on recovered temporal profilestatisticalerror(boxcar int.)(I. Grguras et al., Nature Photonics, 2012)

5. Quantify Timing Jitter at FLASHtime-zero shotsaveraged spectrogramσ = 90 fs (rms)transformation calculated fromstreak-map/EOScollapse full timing information to COMfixed set delayarrival-time distribution

6. Master Optical Laser OscillatorOptical Synchronization at FLASHMaster RF OscillatorFiber Optical Distribution NetworkLaser-to-laser Synch.(OXC)Experiment LaserGun Laser&Accelerator componentsBunch Arrival Monitorfeedback~ 1 fs (OXC-measured)~60 fs ~20 fs w/BAM~40 fs RF scheme<4 fs (all-optical)(S. Schulz, H. Schlarb, S. Schefer, M. K. Czwalinna, S. Pfeiffer, C. Schmidt, U. Wegner)

7. Effective Timing Jitter with all Optical Synchronization~ 30 fs rms“Thickness” of streaking spectrogram gives total effective jitterW/out OXC ~50 fs rms jitterOut-of-loop confirmation of optical lock <4fsCumulative jitter over ~ 2 min acq.w/ “partial” BAM feedback(preliminary analysis)

8. Higher Photon Energy X-ray Pulse Characterization at LCLS ~ 1010eV, ~ mJ/pulse (attenuated to < 10%) ~25,000 single-shot spectra averaged to create spectrogram Vector potential of THz revealed in trace Peak THz field strength ~400kV/cm~ 120eV~ 660 fs

9. THz ~3mJ Pump, Shaped X-ray Pulse Profile ResolvedPeak Separation : 60 ± 8 fsPeak Separation : 105 ± 9 fsPeak Separation : 90 ± 8 fsPeak Separation : 125 ± 10 fsPeak Separation : 150 ± 15 fs(Y. Ding)

10. THz Streaking Measurement ResolutionTemporal resolution is fundamentally limited by:THz streaking powerPhotoelectron energy resolutionOptimal temporal resolution given by the product of the twoSecondary considerations:Initial FEL bandwidth essentially we observe differences between streaked and initial FEL bandwidthnarrower initial BW leads to higher sensitivity under identical meas. conditionsEvolution of the THz focus through the interaction regionleads to “false” broadening of the streaked spectraoverestimate of the X-ray pulse duration

11. Colinear pump geometry (with ~1.5mJ @ 1.5µm) Simplified Experiment Setup Steeper THz streaking field <-> Expect higher time resolution streaking ramp is ~200fs pk-pk (with LiNbO3 was 650 fs pk-pk) Complication from timing jitter (could bucket jump <- > streak with uncharacterized fieldIncreased Streaking Power (DAST)

12. DAST Streaking at LCLSsingle-shot spectrogrambinned spectrogramTHz “bucket” clearly identified using timing tool1-to-5-femtosecond time of arrival accuracyCan make unique mapping of temporal profileMaximum KE shift corresponds to ~ 1MV/cm field strengthsStreaking power ~ 1.7 fs/eV (LiNbO3, 20mJ, ~6 fs/eV)

13. Measurement of Effective “Corrected” Timing Jitter~ 10 fs rmsResidual jitter after spectral encodingUncorrected jitter was 200 fs rms

14. EL(t) eAL(t)td = -T0/4 pifield-freedistributiontd = +T0/4 final energyintensity of electronemissionelectron counts per binelectron kinetic energy [eV]field-freedistributiontd = +T0/4 td = -T0/4 chirpedchirpedbandwidth-limitedbandwidth-limitedW0 = ħωx - Wbinding shape, chirp & duration of the sub-fs xuv pulse

15. Characterize Spectral Phaserotate DAST by 180 degreesProvides access to spectral phase of X-ray pulse If we can retrieve spectral phase, may not need to be in the strong-streaking regimeEases requirements on required streaking strength, initial FEL bandwidthDAST provides access to both streaking field phases w/ single detector

16. 25.3 fsdouble-slot, -23,700µm, BC2=2kAMIR-Streaking (AMO/LCLS Feb-2013, G. Doumy)~200 fs rms timing jitterWithout phase stabilizationAveraged spectral feature (pulse profile)

17. Phase-shifted Measurement for Self-CalibrationMeasurement 1:broadened spectramaps time to energyMeasurement 2:shifted spectraprovides calibration phase-shifted field

18. Tandem Streaking also Delivers Relative Timingnear time-zero arrivalearly arrivalsingle-shot streaking strength gives the relative timing information

19. CollaborationDESYHolger SchlarbSebastian SchulzStefan DüstererUlrike WegnerChristopher BehrensXFELMichael MeyerTommaso MazzaMarkus IlchenThomas TschentscherNikolay KabachnikSLACMatthias HoffmannJerry HastingsChristoph BostedtSebastian SchorbJohn BozekYuanto DingRyan CoffeeWolfram HelmlMPSD/CFEL/UHHIvanka GrgurasSebastian HuberHubertus BrombergerHaiyun LiuUHH/DESY/CFELFlorian GrünerAndreas MaierArgonne National LabGilles DoumyDublin City UniversityJohn CostelloThomas KellyOhio State UniversityLouis DiMauroUPV-EHUAndrey Kazansky

20. Thank you for your attention.