1. X-ray Pump-Probe (WBS 1.2) David Fritz
System Specifications
System Description
WBS
Early Science
Schedule and Costs
Summary
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2. Science Team
Specifications and instrument concept developed with the science team.
The XPP team leaders
Kelly Gaffney, Photon Science, SLAC (leader)
Jorgen Larsson, Lund Institute of Technology, Sweden
David Reis, University of Michigan
Thomas Tschentscher, DESY, Germany
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3. X-ray Pump-Probe Science
Phase Transitions
Order / Disorder
Metal/Insulator
Phonon Dynamics
Charge Transfer Reactions
Photosynthesis
Photovoltaics
Vision
Photoactive Proteins
photo-
excitation
Stampfli and Bennemann Phys. Rev. B 49, 7299 (1994)
The x-ray pump probe instrument will be used to study phenomena that occur on the atomic length and time scales. This includes solid state phenomena such as order/Disorder and metal/Insulator transitions, and the dynamics of phonons; charge transfer reactions that are at the heart of photosynthesis, photovoltaics and vision; and the and photoactve proteins.
photo-
excitation
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4. Time Resolved Scattering
The x-ray pump-probe instrument will take advantage of the ultrashort pulse duration of the LCLS to take snapshots of a photo-induced phenomena.
In general, the experiments performed as this endstation will use an ultrafast laser pulse to initiate a transient response in a system. The system will be probed using various x-ray scattering techniques. The time evolution of the response will be mapped by variably delaying the arrival time of the x-ray pulse with respect to the pump laser pulse.
The success of this end station will depend upon the ability to accommodate a wide variety of laser excitation techniques, samples, sample environments and x-ray scattering methods.
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5. 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

6. 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

7. XPP SCOPE - WBS 1.2 Scope/CD-1 Estimate Includes:
Physics support & engineering integration
X-ray optics – monochromator, focusing optics, slit systems, attenuators
Ultrafast laser system
Detectors - 2D detector from BNL by MOU, Emission Spectrometer
Sample environments - diffractometer system, thermal environments, vacuum environment
Laboratory facilities
Vacuum system
Installation
Diagnostics (WBS 1.5)
Controls and data system (WBS 1.6)
The CD-1 cost estimate of this endstation includes the physics and engineering support necessary to design and construct this instrument. The estimate also includes the hardware associated with …, …, …
Not included in our cost estimates are sample environments such as a liquid jet, magnetic field, or pressure cell. The equipment associated with these environments will be provided by others.
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8. System Specifications
Item
Purpose
Specification
Monochromator
Narrow x-ray spectrum,
multiplex LCLS Beam
600 mm horizontal offset,
9°-50° scattering range,
0.02 arcsec angular res. and repeat.
Focusing optics
Reduces beam size,
maximize on sample flux
µm variable spot size
Laser system
Photoexcitation of
samples
< 50 fs, 20 mJ/Pulse, 800 nm,
wavelength tunable,
temporal pulse shaping capable
X-ray
diffractometer
Sample orientation,
Positioning of detector
Orientation in all degrees of freedom
Detector positioning acc. and
res. < 90 µm
Operation in direct and mono. beam
Detector
Measure of diffraction
patterns
2D,1024 x 1024 pixels, 9090 µm pixel
size, 120 Hz, 10 4 dynamic range,
variable gain
5 major pieces of equipment that will be constructed for the XPP endstation: offset monochromator, focusing optic, laser system, x-ray diffractometer and a detector. The monochromator serves the dual purpose of multiplexing the LCLS beam and narrowing the x-ray spectrum. The focusing optic reduces the beam…
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9. X-ray Pump-Probe Instrument
Laser System
(Fundamental)
X-ray
Diffractometer
& BNL Detector
X-ray Optics
and Diagnostics
Small Angle
Scattering
Wavelength
Conversion
Offset
Monochromator
X-ray Pump-Probe Instrument
The XRPP endstation will be constructed in the 3rd hutch of the NEH.
A conceptual schematic of the XRPP endstation is displayed in this image. The x-ray equipment included an offset monochromator, Beryllium lens focusing optic, and x-ray diffractometer. The front end of the laser system will reside on the second floor laboratory directly above the XRPP hutch. The remainder of the system, in particular the equipment that provides wavelength tunability, will reside in the XRPP hutch. Housing the front end of the laser system on the second floor serves 3 purposes:
Allows maintenance of the laser system to be performed without interference with x-ray operations
Limits the transported radiation to a single wavelength range, which eases laser safety requirements as well as and requires only a single optical transport design.
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10. XPP System Description
1.2.1 Physics support and engineering integration
1.2.2 X-ray optics
1.2.3 Laser system
1.2.4 Detector
1.2.5 Sample environments
1.2.6 Laboratory facilities
1.2.7 Vacuum system
1.2.8 Installation
The x-ray pump-probe instrument is broken into 7 subsystems: Physics support & engineering integration, X-ray optics, … Each of these subsystems have engineering and design cost embedded in them so the progress and cost of each component can be monitored separately. The engineering and design costs contained in is the costs to integrate all of the subcomponents into the global endstation design.
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11. X-ray Pump-Probe System Description (2)
Parameter
Value
Energy Range
6 – 24 keV
Horizontal Offset
600 mm
Scattering Angle
Accuracy
0.02 arcsec
χ Accuracy
4 arcsec
The main x-ray optic included in the x-ray pump-probe instrument is a double crystal monochromator. This device will serve a dual purpose: The first purpose is to provide additional spectral filtering of the LCLS beam. This capability is important for resonant scattering experiments. The second purpose is to multiplex the LCLS beam to allow concurrent beam delivery to multiple endstations. This is achieved by using thin Bragg reflectors, which essentially act as beam splitters. The monochromator is specified to accommodate x-ray energies ranging from 8 to 24 keV. A 600 mm offset between the monochromatic beam and direct beam is specified to allow sufficient space to install a x-ray spectrometer in the monochromatic beam without interference with the direct beam vacuum transport.
Additional x-ray optics include a beryllium lens focusing optic, precision slits, and attenuators.
1.2.2 X-ray optics
Monochromator
Thin crystals
Be lens
Slits
Attenuators
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12. X-ray Pump-Probe System Description (3)
1.2.3 Femtosecond laser system (similar to LCLS gun laser)
Ti:Sapphire based system
Up to 20 mJ/pulse (<1.5 % rms stability) , < 50 fs, 800 nm, 120 Hz
Synchronized to LCLS RF ( <300 fs rms integrated jitter)
Wavelength tunable
Harmonic generation (400 nm, 266 nm)
Parametric amplification (240 nm – 11,000 nm)
Temporal pulse shaper
Diagnostics
Energy, wavelength, temporal profile, contrast, spatial profile
1.2.4 Detectors
2D Detector (BNL)
1024 x 1024 pixels
90 micron pixel size
10 4 dynamic range
120 Hz readout rate
X-ray Emission Spectrometer
100 eV dynamic range
1 eV resolution
High collection efficiency
Different experiments will have distinct requirements of the laser excitation radiation. Therefore, the flexibility of the laser system is extremely important. The ability to tune the wavelength of the laser radiation, either through harmonic generation in non-linear crystals or parametric amplification, and to shape the temporal profile of the laser pulse in a sophisticated manner is required.
To effectively operate the laser system, and to determine the experimental conditions of the sample such as excitation density and the peak field, a diagnostics suite that can effectively characterize the photoexcitation pulse energy, wavelength, temporal profile, contrast ratios, and spatial profile is included in the XPP laser system.
Laser System is commercial and not beyond state of the art!! Very similar to the LCLS gun laser.
A pixel array detector is being developed at Brookhaven National Laboratory for the X-ray pump-probe instrument. It will be an array of 1000 x 1000 pixel with a pixel size of 80 square microns. To support the breadth of experiments that will be performed at the XPP station, the detector must have the ability to detect a single x-ray photon with high efficiency for diffuse scattering applications as well as measure a slight change in an intense Bragg reflection. To accommodate this requirement, the detector will have high quantum efficiency (approaching unity at 8 keV), 10^3 dynamic range per pixel, and a variable gain spanning 4 orders of magnitude. As will be described in the WBS 1.7 Diagnostics sections, the LCLS will be a highly fluctuating source even when maturely commissioned. The successful execution of the experiments at the x-ray pump-probe instrument will hinder on the ability to mitigate these source fluctuations through diagnostics. It is therefore necessary that both the pixel array detector and the diagnostics operate on a pulse-by-pulse acquisition since integration over the source fluctuations cannot be performed. Thus, the readout rate of the detector must accommodate 120 Hz operation to take full advantage of the LCLS.
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13. X-ray Pump-Probe System Description (4)
1.2.5 Sample environments
X-ray diffractometer
Operate in both direct and monochromatic beam
Detector motion about a spherical surface centered at sample
Cryostat
X-ray and optical window (collinear and non-collinear geometry)
Decoupled sample motion from vacuum shroud
Cryostream
Liquid jet
Vacuum chamber
Two sample environments will be constructed for the x-ray pump-probe instruments: a x-ray diffractometer and a cryostat.
In general, constraints are placed on the scattering geometry to fix both the x-ray and laser penetration depths into the sample bulk. Doing so, however, requires orienting the physical surface and the reciprocal lattice of the sample with respect to the x-ray beam, making the scattering geometry analogous to one used in a surface scattering experiment. The diffractometer also serves the purpose of moving the detector about a spherical surface.
A cryostat is also specified to control the temperature of samples.
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14. X-ray Pump-Probe System Description (5)
1.2.6 Laboratory facilities
1.2.7 Vacuum system
1.2.8 Installation
The LCLS project will deliver electrical and gas utilities to the x-ray hutches. However, the deliver of ultilities within the hutch is outside of the LCLS scope. The costs for intrahutch distribution of utilites is included in 1.2.6
A evacuated beam transport is required to avoid attenuation of the x-ray beam due to gas scattering and also to avoid contamination of x-ray optics.
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15. 1.2 WBS
Here is the diagram of the Work Breakdown structure for the XRPP endstation. As I described earlier, the level 3 subsystems are … At level 4 are various x-ray optics including the offset monochromator, focusing optic, …
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16. CD 4a XPP Instrumentation
LCLS AMO Laser
Detector
X-ray
Diffractometer
X-ray Optics
and Diagnostics
Utilize AMO laser
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17. CD 4a XPP Science Early experimental techniques
Time-resolved diffraction
Time-resolved diffuse scattering
~ 100 fs temporal resolution
Non-thermal melting and large amplitude coherent phonons
Natural extension to research performed at SPPS
Characterize source and instrument capabilities
Interaction of FEL with solid state matter as soon as LCLS reaches saturation

18. XPP Schedule in Primavera 3.1
Here is the projected schedule for the pump-probe endstation. The major milestones are the completion of the monochromator, laser system, installation of the pixel array detector, and diffractometer. At the beginning of the 3rd quarter of fiscal year 2009, beam is delivered to the endstation and laser transport optics will be installed so that experiments can begin with user provided equipment and shared use of the AMO laser system. At the end of 1st quarter 2011, muliplexing of the LCLS beam will begin with the completion of the offset monochromator system and also with the diffractometer system and monochromatic beam will begin.
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19. XPP Milestones CD-1 Aug 01, 07 Conceptual Design Complete Sep 21, 07
CD-2a Dec 03, 07
CD-3a Jul 21, 08
Phase I Final Design Complete Oct 15, 08
Receive Diffractometer Feb 19, 09
Receive Focusing Lenses Feb 27, 09
Receive Laser Optics and Diagnostics Mar 18, 09
Phase I Installation Complete Oct 01, 09
Install BNL XPP Detector Nov 03, 09
CD-4a Feb 08, 10

20. XPP Cost Estimate
Here is the high level cost estimate of the Pump-probe instrument. (Read the numbers) Cost details will be presented in the breakout session.
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21. Summary Instrument concept is advanced
100% of Letters of Intent are represented in instrument concept
Standing monthly meeting with XPP team
Instrument concept is based on proven developments made at SPPS and SR sources
Initial specifications well developed
Ready to proceed with baseline cost and schedule development
In summary, there has been valuable experience gained by the scientific team at the Sub-picosecond pulse source and other synchrotron radiation sources. As a result, the initial specifications are well developed and communicated at a standing monthly meeting with the XRPP team members. 100% of the letters of intent for this endstation are represented at this meeting. The initial instrument conceptual design meeting these specifications is advanced and we are ready to proceed with baseline cost and schedule development.
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