Transcript XPP Experiment

X-ray Pump-Probe Instrument
D. M. Fritz
Pump-probe Experiments
System Description
X-ray optics
Laser System
Detector
Sample environments
Laser/X-ray Timing
Technical Choice
LCLS FAC Meeting April 16, 2007
XPP Instrument
D. M. Fritz
[email protected]
Science Team
Specifications and instrument concept developed
with the science team.
The XRPP team
Kelly Gaffney (leader), SSRL/SLAC
Jorgen Larsson, Lund Institute of Technology, Sweden
David Reis, University of Michigan
Thomas Tschentscher, DESY, Germany
LCLS FAC Meeting April 16, 2007
XPP Instrument
D. M. Fritz
[email protected]
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 April 16, 2007
XPP Instrument
D. M. Fritz
[email protected]
Time Resolved Scattering
LCLS FAC Meeting April 16, 2007
XPP Instrument
D. M. Fritz
[email protected]
Laser System
(Fundamental)
Small Angle
Scattering
Wavelength
Conversion
X-ray
Diffractometer
Offset
Monochromator
X-ray Pump-Probe Instrument
LCLS FAC Meeting April 16, 2007
XPP Instrument
D. M. Fritz
[email protected]
X-ray Optics
Parameter
Value
Energy Range
6 – 24 keV
Horizontal Offset
600 mm
Scattering Angle
90 - 500
 Accuracy
0.02 arcsec
χ Accuracy
4 arcsec
Scattering Angles (2 theta)
Double Crystal Offset Monochromator
Narrows x-ray spectrum for resonant scattering experiments
Multiplexes LCLS beam (mono. beam, diagnostic beam)
LCLS FAC Meeting April 16, 2007
XPP Instrument
1.5 Å
0.5 Å
Silicon
111
27.6°
9.1°
Silicon
220
45.8°
14.9°
Diamond
111
42.5°
13.9°
Diamond
220
-
22.8°
D. M. Fritz
[email protected]
X-ray Optics
Double Crystal Offset Monochromator
for 2 µm Si (111) @ 1.5 Å
85% transmission ,2.5% - Mono beam, 1.3% - Diagnostics beam
LCLS FAC Meeting April 16, 2007
XPP Instrument
D. M. Fritz
[email protected]
X-ray Optics
Flexure Stages
Piezoelectric Stages
Double Crystal Offset Monochromator (cont.)
 motion
0.02 arcsecond resolution and repeatability (100 nrad)
LCLS FAC Meeting April 16, 2007
XPP Instrument
D. M. Fritz
[email protected]
X-ray Optics
Mono
Lens
190 m
4m
Beryllium lens focusing optic
Variable spot size from 2-10 µm and 40-60 µm @ 8.3 keV
Variable spot size from 2-10 µm @ 24.9 keV
> 40% throughput
Positioning resolution and repeatability to 1 µm
LCLS FAC Meeting April 16, 2007
XPP Instrument
D. M. Fritz
[email protected]
Laser System Overview
LCLS FAC Meeting April 16, 2007
XPP Instrument
D. M. Fritz
[email protected]
Ultrafast Laser System
Ti:Sapphire Oscillator & Power Amplifiers
Compressor, OPA, Harmonic Generation, Delay Stage
LCLS FAC Meeting April 16, 2007
XPP Instrument
D. M. Fritz
[email protected]
Ultrafast Laser System
Cavity Length
Stabilization Mirror
Ti:Sapphire Oscillator
119 MHz rep. rate, <30 fs ~ 2.5 nJ/pulse
Frequency stabilized to LCLS RF < 300 fs rms phase jitter
Demonstrated at SPPS
LCLS FAC Meeting April 16, 2007
XPP Instrument
D. M. Fritz
[email protected]
Ultrafast Laser System
Power Amplifiers
Regenerative amplifier
~ 2.5 mJ (< 1% rms stability), 120 Hz, <35 fs
Multipass amplifier
~ 20 mJ (<1.5% rms stability), 120 Hz, <35 fs
Second Compressor
External Pockels Cell
Arbitrary laser pulse train structure
LCLS FAC Meeting April 16, 2007
XPP Instrument
D. M. Fritz
[email protected]
Ultrafast Laser System
Temporal Pulse Shaper
Create complex excitation pulse envelopes
Multi-pulses
Compression optimization
LCLS FAC Meeting April 16, 2007
XPP Instrument
D. M. Fritz
[email protected]
XPP Detector - BNL
Pixel array detector
1000 x 1000 pixels
80 micron pixel size
High Detector Quantum Efficiency (DQE)
10 4 dynamic range at 8 keV
120 Hz Readout Rate
LCLS FAC Meeting April 16, 2007
XPP Instrument
D. M. Fritz
[email protected]
XPP Diffractometer System
Rotary Stages vs. Robot Arm
LCLS FAC Meeting April 16, 2007
XPP Instrument
D. M. Fritz
[email protected]
XPP Diffractometer System
X-ray Diffractometer
Operate in both direct and monochromatic beam
Sample orientation & translation
Detector motion about a spherical surface centered at sample
(variable radius from 0.1 m to 1.5 m)
Accommodate various sample environments
LCLS FAC Meeting April 16, 2007
XPP Instrument
D. M. Fritz
[email protected]
Small Angle Scattering Capability
10 µrad angular resolution with XAMPS detector
Detector translation
Operate in both direct and monochromatic beam
LCLS FAC Meeting April 16, 2007
XPP Instrument
D. M. Fritz
[email protected]
Sample Environments
Collinear Geometry
Non-collinear Geometry
Cryostat System
Vacuum shroud
Optical and x-ray windows (collinear & non-collinear geometry)
Decoupled sample motion
LCLS FAC Meeting April 16, 2007
XPP Instrument
D. M. Fritz
[email protected]
Expected Fluctuations of the LCLS
Intensity fluctuations exceeding 30%
Expected spatial jitter ~25% of beam diameter
Wavelength fluctuations expected to be ~ 0.2% of center
wavelength (≈ LCLS intrinsic bandwidth)
Pulse duration expected to vary ~15%
X-ray Pulse/LCLS RF timing will fluctuate by ~ 1 ps
- Diagnostics are required to measure these parameters since they
cannot be controlled
- This information must be available to accelerator operations and
experiments
LCLS FAC Meeting April 16, 2007
XPP Instrument
D. M. Fritz
[email protected]
Temporal Jitter
Master
Clock
Electron Gun
Accelerating
Elements
Coax RF
Distribution
Network
Experimental
Pump Laser
Sources of Short Term Jitter
• Coax RF distribution Network
• e-beam phase to RF phase
• End Station Laser phase to RF phase
Limited to ~ 1 ps !
LCLS FAC Meeting April 16, 2007
XPP Instrument
D. M. Fritz
[email protected]
Electro-optic Sampling
Stabilized Fiber Optic RF Distribution (10 fs)
LBNL
Pump-probe
Gun Laser
Electro-optic
Sampling
Laser
Sector 20
LTU
NEH
Laser
Temporal resolution is now limited by:
1) Our ability to phase lock the lasers to the RF
2) Intra-bunch SASE jitter
LCLS FAC Meeting April 16, 2007
XPP Instrument
D. M. Fritz
[email protected]
SPPS Laser/X-ray Timing
100 consecutive shots
LCLS FAC Meeting April 16, 2007
XPP Instrument
Single shot, Lorentzian fit
D. M. Fritz
[email protected]
Data Sorting at SPPS
• 10 Hz
• Point Detector
LCLS FAC Meeting April 16, 2007
XPP Instrument
D. M. Fritz
[email protected]
XPP Data Sorting at LCLS
X-ray Detector
LCLS Beam Parameters
Intensity
Time of Arrival
Wavelength
180 MB/s
~ 1 MB/s
Real Time
Processing Unit
t1
t2
LCLS FAC Meeting April 16, 2007
XPP Instrument
t3
t4 …………………………………………………….………………tN
• 120 Hz
• 1 Megapixel Area Detector
• 2-dimensional binning or data filtering?
D. M. Fritz
[email protected]
Key Technological Choices
1. Diamond vs. Silicon Monochromator Crystal
- Absorption, Damage vs. Quality
2. Flexure vs. Piezo Monochromator Rotation Stage
- Stability vs. Range
3. Robot Arm vs. Rotary Stage Detector Mover
- Reciprocal Space Access vs. Control, Safety
4. Hexapod vs. Stages Sample Manipulator
- Range of Motion vs. Stability, Control
5. Ti:Sapphire Oscillator vs. Fiber Oscillator
- Bandwidth vs. Synchronization
LCLS FAC Meeting April 16, 2007
XPP Instrument
D. M. Fritz
[email protected]