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from the Charge to the Workshops
• In each of the four identified science areas establish a priority list of desired user experiments...
• Identify important x-ray beam parameters to address the envisioned science opportunities, such as photons per pulse, pulse length, 120-Hz-based pulse trains, bandwidth and spectral purity, polarization, coherence…
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this talk
An attempt to enable the discussion of exciting experiments by presenting some basic boundary conditions and ideas that have already been put forward concerning: • LCLS FEL sources
• LCLS instrument capability
• LCLS facility layout
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LCLS growth
• LCLS has a growth plan stretching at least until 2025 – LCLS II Project will provide the infrastructure to enable growth – Anticipate that LUSI II will provide several new instruments – Growth beyond LUSI II will occur as opportunities arise
• The goal for 2025 – 4 FEL sources, all or most seeded – At least 10 experimental stations – Ability to run many stations simultaneously
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Basic LCLS source considerations
• LCLS complex can support 4 FEL undulators – One exists at LCLS I – Two will be added with LCLS II – A fourth could be added at LCLS I
• LCLS I and LCLS II can both reach >10 GeV electron energy – LCLS I can reach 14.5 GeV (>20 GeV with future upgrade) – LCLS II is limited to 13.5 GeV
• Space exists for all undulators to become seeded FEL sources – Undulators generally start as SASE sources and can be upgraded
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FEL self seeding
Intense x-ray source with spiky spectrum
Monochromator filter creates seed with controlled spectrum
FEL amplifier (exponential intensity gain)
Additional amplification (linear gain)
seeded
SASE
Photon energy
Inte
nsity
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Evolution of an FEL undulator
0 61.6 66.0 286.0
Full build out, additional tapered undulators:
S.S. Virtual Source Point
178-183
Tapered 15-64 220.0m
S.S. 1-14 61.6m M
ono
4.4m
0 171.6 286.0
LCLS-II HXR BASE Line:
SASE 1-26 114.4m
Drift 171.6m
SASE Source Point
246-261m
0 215.6 286.0
LCLS-II HXR w/ Self Seeding Mono:
Tapered 12-26 66.0m
167.2
Drift 167.2m
S.S. Virtual Source Point
251-256m
220.0
Mon
o 4.
4m S.S. 1-11
48.4m
0
S.S. 1-11 48.4m
189.2 286.0
Add undulators to reach saturation:
Tapered 12-32 92.4m
140.8
Drift 140.8m
S.S. Virtual Source Point
232-237
Mon
o 4.
4m
193.3
M. Rowen
250 pC 8 keV 2.1 mJ 0.47% bw
40 pC 8 keV 2.6 mJ 0.05% bw
40 pC 8 keV 4.8 mJ 0.05% bw
40 pC 8 keV 8.3 mJ 0.04% bw
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Polarization control can be added
3 Pol. 13.2m
0 286.0
Full build out, tapering and Polarization Control:
180.4
Drift 132.0
S.S. 1-9 39.6m M
ono
8.8m
171.6 132.0
Tapered 10-30 92.4m
S.S. Virtual Source Point 222-227
272.8
0 206.8
Drift 206.8m
SASE Source Point 247-257m
LCLS-II SXR BASE Line:
SASE 1-15 66.0m
272.8
286.0
Drift 13.2m
M. Rowen
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250pC bunch charge 70m SXR undulator 110m HXR undulator
LCLS II HXR 13.5 GeV
LCLS II HXR 8.5 GeV
LCLS II SXR 13.5 GeV
LCLS II SXR 8.5 GeV
LCLS I and LCLS II together provide complete coverage from 250eV to nearly 20keV with >1mJ pulses
LCLS I 3.3-15 GeV
LCLS SASE source characteristics
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LCLS seeded source characteristics
0.1 0.1
1
1
10
10
100
Photon Energy (keV)
Ene
rgy
per p
ulse
(mJ)
SASE
Seeded
100pC, 110m SXR undulator 50pC, 250m HXR undulator Large uncertainties in seeded
optimization and sensitivity
HXR
SXR
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Conclusions about FEL sources
• Seeded sources are generally better – Generally give more pulse power, much higher peak power – Narrow, predictable bandwidth – But, single-bunch seeding is limited to lower-charge short
bunches (a two-bunch seeding scheme might overcome this limitation)
• LCLS facility will cover a wide photon energy range – LCLS II baseline spec is 250 eV to 13 keV – Expect actual useful range to extend to near 20 keV or above – Much of the range can be covered with one fixed electron energy
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Proposed definitions
• Beam Transport – transmits X-rays from source to end station – May service more than one end station – Optics elements may be distributed along the beam transport
• Optics – redirect and condition the X-rays on the way from source to end station – May service more than one end station
• End Station – includes sample environment and detectors – May be permanent or removable (roll-in/roll-out)
The term “beamline” can be confusing when used in a context with sources, transport, and optical components serving multiple experimental stations. It may help to focus the discussion on the following:
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LCLS instruments are becoming more complex
• LCLS has 6 hutches now, with 1 source – AMO, SXR have multiple, removable end stations
• CXI is developing a system of 2 in-line end stations – Could eventually allow simultaneous experiments
• LCLS is developing beam-splitting technology – In near future, expect to deliver beam to several end stations
simultaneously
Currently the source feeds only 1 end station at a time
but
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More complexity coming
• LCLS II adds 2 new FEL sources • LCLS II adds room for at least 4 new end stations
– Could squeeze in additional end stations
• LCLS I has room for an additional undulator – More capability for simultaneous operations
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• LCLS available beam time will dramatically increase
• Source flexibility may decrease – Multiple experiments on one source must agree on parameters
A fundamental change in LCLS operation
Consequences of LCLS expansion/multiplexing:
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How to best manage the expansion?
• Start with the science – A clear vision of science opportunities – An understanding of the instrumentation that the science requires
• Develop concepts of instruments for doing the science, including source parameters, optics and diagnostics, end stations
• Optimize the design and layout of the instruments
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Information to be captured from discussions during and after this workshop
Science Wavelength range
Band-width
Photons per pulse
Pulse duration
Polarization Focus size
Sample environ-ment
Detector needs
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Possible biology instrumentation
• High peak power hard X-ray imaging/diffraction instrument – With lasers for pumping, various sample environments, fluorescence
spectrometers – With 2 end stations in series for simultaneous operation
• High peak power intermediate-energy X-ray imaging instrument – 2-6 keV photon energy – With lasers, sample environments, spectrometers
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Possible materials/chemistry instrumentation
• General purpose hard X-ray scattering instrument – With various sample environments, detector resolutions, geometries,
monochromator, detectors, focusing, split & delay, optical pump lasers, etc…
– For WAXS, SAXS, XAS, XES, coherent scattering, etc…
• Soft X-ray instrument with polarization control – With several end stations optimized for diffraction, RIXS, surface
science, etc… – With pump laser capability over wide spectral range including THz
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• Seeded source with narrow bandwidth, high power • Branches optimized so user can choose either high energy
resolution or high peak power • Multiple end stations accommodating various sample
sources and spectrometers – Gas jets, cluster sources ovens, laser ablation sources, ion sources – Ion and electron spectrometers including magnetic bottle, high
energy resolution, and angle resolving spectrometers – X-ray spectrometer
• Lasers for time-resolved experiments • Diagnostics for spent X-ray beam
Possible AMO instrumentation
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Summary
• LCLS has an ambitious expansion plan and the LCLS II project is a critical enabling step
• LCLS should start now to work out the details of the
expansion plan in anticipation of funding opportunities – This workshop will help to define the first step, a package of
instruments to be installed at LCLS II
• The details start with the science, which then defines the
source and instrument requirements