X-ray Pump-Probe Instrument
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X-ray Pump-Probe Instrument David Fritz Instrument Overview Instrument Layout System Description X-ray Optics &Diagnostics Sample Environments Detectors Laser System FEL/Pump Laser Timing System Technical Issues Summary LCLS FAC Meeting Oct. 30, 2007 1 David Fritz dmfritz@slac.stanford.edu X-ray Pump-Probe Science photoexcitation Stampfli and Bennemann Phys. Rev. B 49, 7299 (1994) Phase Transitions Order / Disorder Metal/Insulator Phonon Dynamics Charge Transfer Reactions Photosynthesis Photovoltaics Vision Photoactive Proteins photoexcitation LCLS FAC Meeting Oct. 30, 2007 2 David Fritz dmfritz@slac.stanford.edu Ultrafast Hard X-ray Sources to Date 3rd Generation Synchrotrons (APS) ~ 1 x 10 9 photons/second coincident with a 1 kHz Laser 100 ps pulse duration Slicing Source ~ 1 x 10 6 photons/second coincident with a 1 kHz Laser 100 fs pulse duration Laser Plasma Source ~ 1 x 10 5 photons/second collected at 10 Hz 300 fs pulse duration Sub-Picosecond Pulse Source ~ 1 x 10 7 photons/second coincident with a 10 Hz Laser 100 fs pulse duration LCLS FAC Meeting Oct. 30, 2007 3 David Fritz dmfritz@slac.stanford.edu Ultrafast X-ray Science to Date Non-thermal Melting of Semiconductors Large Amplitude Coherent Phonons Single Shot at SPPS 20 minute acquisition at SPPS Limited to slow processes ( > 100 ps) or X-ray diffraction from single crystals LCLS FAC Meeting Oct. 30, 2007 4 David Fritz dmfritz@slac.stanford.edu XPP Instrument Scope Instrument will operate in the 6-25 keV photon energy range X-ray Wavelength and Bandwidth Fundamental Monochromatic Fundamental 3rd Harmonic Monochromatic 3rd Harmonic Sample Environment Room Press. & Room Temp Temperature Controlled Cryostat Liquid Vacuum Scattering Technique Wide Angle Scattering Small Angle Scattering Emission Excitation Laser Parameters Med. Energy (2 mJ fund.) Fundamental (800 nm) 2nd Harmonic (400 nm) 3rd Harmonic (266 nm) OPA High Energy (20 mJ fund.) Fundamental (800 nm) 2nd Harmonic (400 nm) 3rd Harmonic (266 nm) Versatility is key to the instrument success LCLS FAC Meeting Oct. 30, 2007 5 David Fritz dmfritz@slac.stanford.edu Instrument Specifications FEE Photon Shutter Purpose Specification Large Offset Monochromator Multiplex FEL radiation, Narrow FEL spectrum 600 mm offset, ≤ 10-4 spectral bandwidth Harmonic Rejection Mirrors Filter 3rd Harmonic Radiation 105 : 1 contrast ratio < 0.5 nm surface roughness Slits/Apertures Beam definition, Beam halo cleaning 0.1 um stability, 1 um repeatability Attenuators Control incident x-ray flux Variable, up to 107 reduction at 1.5 Å Diagnostics Intensity Monitor, Position Monitor 0.1% relative intensity measurement, < 5% incident x-ray attenuation Be Focusing Lenses Increase incident x-ray flux 2-10 mm, 40-60 mm spot size at 1.5 Å, 2-10 mm spot size at 0.5 Å Laser System Photoexcitation of samples Ultrafast pulse duration (<50 fs), Up to 20 mJ pulse energy at 800 nm, 120 Hz X-ray Diffractometer Sample orientation Kappa diffractometer, Platform diffractometer Wide Angle Detector Stage Move the detector in reciprocal space Spherical detector motion at a 10-150 cm radius Small Angle Stage Small Angle Detector Stage Collect SAXS patterns 2.5, 5, and 10 m Sample-to-detector distance, 0.5 m horizontal detector motion Diagnostics 2D Detector Provide 2D pixelated detection capability 1024 x1024 pixels, 120 Hz frame/s, dynamic range >103, single-photon sensitivity, pixel size 90x90 mm2 Diagnostics Monochromator Photon Shutter Diagnostics NEH Hutch 3 Attenuators Primary Slits Focusing Lenses Diagnostics Mirror System Secondary Slits Diagnostics Laser Port Diffractometer Wide Angle Stage Photon Shutter LCLS FAC Meeting Oct. 30, 2007 Item 6 David Fritz dmfritz@slac.stanford.edu XPP Instrument Location CXI XCS XPP Endstation AMO (LCLS) LCLS FAC Meeting Oct. 30, 2007 7 David Fritz dmfritz@slac.stanford.edu Laser System (Fundamental) Small Angle Scattering X-ray Diffractometer & BNL Detector Wavelength Conversion X-ray Optics and Diagnostics Offset Monochromator X-ray Pump-Probe Instrument LCLS FAC Meeting Oct. 30, 2007 8 David Fritz dmfritz@slac.stanford.edu X-ray Optics – Offset Monochromator Scattering Angles (2 theta) Parameter Value Energy Range 6 – 24 keV 1.5 Å 0.5 Å Silicon 111 27.6° - Horizontal Offset 600 mm Silicon 220 45.8° 14.9° Scattering Angle 140 - 500 Diamond 111 42.5° 13.9° Accuracy 0.02 arcsec Diamond 220 - 22.8° χ Accuracy 4 arcsec Double crystal offset monochromator Narrows x-ray spectrum for resonant scattering experiments Multiplexes LCLS beam (mono. beam, diagnostic beam) LCLS FAC Meeting Oct. 30, 2007 9 David Fritz dmfritz@slac.stanford.edu X-ray Optics - Attenuators Attenuators Variable, up to 10 7 reduction at 8.3 keV Coherence preserving High damage threshold LCLS FAC Meeting Oct. 30, 2007 10 David Fritz dmfritz@slac.stanford.edu X-ray Optics – Slit Systems D. Le Bolloc’h et al., J. Synchrotron Rad., 9, 258-265 (2002). Slit systems Variable horizontal and vertical gap from 5 μm – 5 mm Can withstand full LCLS flux – unfocused Minimize background scatter from blades LCLS FAC Meeting Oct. 30, 2007 11 David Fritz dmfritz@slac.stanford.edu X-ray Optics - Be Focusing Lenses B. Lengeler et al., J. Synchrotron Rad., 6, 1153-1167 (1999). Beryllium CRL > 40% throughput Positioning resolution and repeatability to 1 µm Z translation to vary spot size LCLS FAC Meeting Oct. 30, 2007 12 David Fritz dmfritz@slac.stanford.edu X-ray Optics – Harmonic Rejection Mirrors 10-2 10-3 10-4 10-5 10-6 Harmonic Rejection Mirror System > 80% throughput 10 5 : 1 contrast ratio (10 7 : 1 overall) LCLS FAC Meeting Oct. 30, 2007 13 David Fritz dmfritz@slac.stanford.edu Kappa Diffractometer δ η α = 50º φ x κ μ Kinematic Mount ν XY Table Kappa X-ray Diffractometer Operate in both direct and monochromatic beam Large reciprocal space access Gas stream temperature control LCLS FAC Meeting Oct. 30, 2007 14 David Fritz dmfritz@slac.stanford.edu Platform Diffractometer δ x trans z trans y trans χ ω μ Kinematic Mount ν XY Table Platform X-ray Diffractometer Operate in both direct and monochromatic beam Accommodates large sample environments (Cryostats, vacuum chambers, etc…) LCLS FAC Meeting Oct. 30, 2007 15 David Fritz dmfritz@slac.stanford.edu Emission Spectroscopy XAMPS vertical cut δ spectrum top view PSD analyzers sample μ analyzers beam ν XY Table X-ray Emission Spectrometer ~ 50 eV dynamic range ~ 0.1 eV resolution Large collection solid angle LCLS FAC Meeting Oct. 30, 2007 16 David Fritz dmfritz@slac.stanford.edu Small Angle Scattering SAXS Capability 2.5, 5, and 10 m sample-to-detector distance 10 µrad angular resolution with XAMPS detector (10 m) Operate in both direct and monochromatic beam LCLS FAC Meeting Oct. 30, 2007 17 David Fritz dmfritz@slac.stanford.edu 2D Detectors 2D detector (BNL) 1024 x 1024 pixels 90 micron pixel size High Detector Quantum Efficiency (DQE) 10 4 dynamic range at 8 keV 120 Hz Readout Rate LCLS FAC Meeting Oct. 30, 2007 18 David Fritz dmfritz@slac.stanford.edu Laser System LCLS FAC Meeting Oct. 30, 2007 19 David Fritz dmfritz@slac.stanford.edu Laser System Ti:Sapphire Oscillator & Power Amplifiers Compressor, OPA, Harmonic Generation, Delay Stage LCLS FAC Meeting Oct. 30, 2007 20 David Fritz dmfritz@slac.stanford.edu Laser System Laser Diagnostics Temporal and spectral characterization Grenouille – Real time pulse duration, spectrum 3rd Order Correlator – Contrast ratio Energy characterization Per pulse Joule meter, 120 Hz, 1% accuracy Spatial characterization Profile monitor at a “virtual” sample, 5 μm resolution LCLS FAC Meeting Oct. 30, 2007 21 David Fritz dmfritz@slac.stanford.edu X-ray Diagnostics Transmissive Intensity Monitor > 95 % Transmission Relative accuracy < 0.1% Flourescent Screeens Diodes LCLS FAC Meeting Oct. 30, 2007 22 David Fritz dmfritz@slac.stanford.edu Laser/FEL Timing Master Clock Electron Gun Accelerating Elements RF Distribution Network Experimental Pump Laser Sources of Short Term Jitter E-beam phase to RF phase jitter Electron beam energy jitter + dispersive electron optics End station laser phase to RF Phase ~ 1 ps limit LCLS FAC Meeting Oct. 30, 2007 23 David Fritz dmfritz@slac.stanford.edu Traditional Pump-probe C. W. Siders Delay will be achieved by optical delay and/or RF phase shift Resolution limited by LCLS/laser jitter ~ 1 ps limit LCLS FAC Meeting Oct. 30, 2007 24 David Fritz dmfritz@slac.stanford.edu diffracted intensity Single Shot Pump-Probe A. M. Lindenberg et al., Science, 308, 392 (2005). Limited to X-ray diffraction Need ‘large’ effects Imaging resolution affects temporal resolution LCLS FAC Meeting Oct. 30, 2007 25 David Fritz dmfritz@slac.stanford.edu Laser/FEL Timing Stabilized Fiber Optic RF Distribution (10 fs) LBNL Pump-probe Gun Laser Electro-optic Sampling Laser Sector 20 LTU NEH Laser Electro-optic Sampling Enhanced Temporal Resolution (~ 100 fs) Limited by our ability to phase lock the lasers to the RF backbone Limited by Intra-bunch SASE jitter LCLS FAC Meeting Oct. 30, 2007 26 David Fritz dmfritz@slac.stanford.edu Non-sequential Sampling 100 consecutive shots Single shot, Lorentzian fit Diagnostic required to measure LCLS/laser timing EOS demonstrated at SPPS LCLS FAC Meeting Oct. 30, 2007 27 David Fritz dmfritz@slac.stanford.edu Laser/FEL Timing Diagnostic Beam 1.3% Mono. Beam 2.5% 8keV 600mm Transmitted Beam 85% Diagnostic Beam for Direct Timing Measurement Permits destructive x-ray timing measurement in hutch Same excitation laser can be used LCLS FAC Meeting Oct. 30, 2007 28 David Fritz dmfritz@slac.stanford.edu Technical Issues 1. X-ray/Laser Timing Below 100 fs 2. Flexible Diffractometer Design - Kappa + Platform 3. Thin Monochromator Crystals - Diamond vs. Thin Silicon - (Absorption, Damage vs. Quality) 4. Monochromator Precision Motion - 200 nRad motion & stability 5. Rejecting Fundamental in 3rd Harmonic Operation LCLS FAC Meeting Oct. 30, 2007 29 David Fritz dmfritz@slac.stanford.edu Summary Instrument design emphasizes flexibility X-ray scattering techniques WAXS SAXS Emission spectroscopy X-ray optics can tailor FEL parameters for users Many sample environments are accommodated Vacuum Low temperature (cryostat, cryostream) Samples in solution Versatile laser system LCLS FAC Meeting Oct. 30, 2007 30 David Fritz dmfritz@slac.stanford.edu Non-sequential Sampling D. M. Fritz et al., Science, 315, 633 (2007). A. L. Cavalieri et al., Phys. Rev. Lett., 94, 114801 (2005). LCLS FAC Meeting Oct. 30, 2007 31 David Fritz dmfritz@slac.stanford.edu
