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MIT X-ray Laser Project
An X-ray Laser at the Transform Limit:
Technical Challenges and Scientific Payoff
David E. Moncton
Massachusetts Institute of Technology
NSLS
February 20, 2004
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MIT X-ray Laser Project
MIT X-ray Laser R&D Proposal
Contact: David E. Moncton, Director Telephone: 617-253-8333
E-mail: [email protected]
website: http://mitbates.mit.edu/xfel/indexpass.htm
Bates Senior Staff Contributors
Manouchehr Farkhondeh William M. Fawley James FujimotoJan van der Laan Erich Ippen
Christoph Tschalaer Ian McNulty
Denis B. McWhan
Fuhua Wang
Jianwei Miao
Michael Pellin
Abbi Zolfaghari
Mark Schattenburg
Gopal K. Shenoy
Townsend Zwart
Co-Principal Investigators Science Collaborators
William S. Graves Simon Mochrie Keith A. Nelson
Franz X. Kaertner Gregory Petsko Dagmar Ringe
Richard Milner Henry I. Smith Andrei Tokmakoff
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MIT X-ray Laser Project
A Unique Opportunity± An X-ray Laser User Facility
30 or more independent beamlines
Fully coherent milli-Joule pulses at kHz rates
Wavelength range from 200 nm to 0.1 nm
The Scientific Impact
Femtosecond pulse duration Chemistry
Condensed Matter Physics
Atomic Physics
Fundamental Physics
BiologyFull transverse coherence
Milli-volt bandwidths
Full quantum degeneracy
High electric field
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MIT X-ray Laser Project
Photon pulses would be ³transform-limited´ satisfying the
Uncertainty Principle in all six phase-space dimensions
Transverse Phase Space
(x (y ~ 100 microns
(k x (k y ~ 10-5 nm-1
Longitudinal Phase Space
(t ~ fs 1ps ([beV 2meV
Note that all 1011 to 1014 photons in each pulse wouldoccupy the same quantum state
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MIT X-ray Laser Project
q=k i-k f [=[i-[f
Photon-in ± photon out Probes charge-neutral excitations:
Phonons, diffusive modes, orbitons,
superconducting gaps«
Excitons, plasmons, particle-holecreation, interband transitions«
Inelastic X-ray Scattering (IXS)
ARPES measures A(q,[), surface sensitive. INS does not couple to charge, and requires large sample.
EELS cannot measure to large q, or in fields.
W([), Raman are restricted to q=0.
Complements existing techniques:
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MIT X-ray Laser Project
Existing 3rd Generation IXS Beamlines
ESRF
APS
3 Beamlines with meV resolution, 2 more soon
1 Beamline with 100 meV resolution
2 Beamlines with eV resolution
ESRF APS Sp
ring-8
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MIT X-ray Laser Project
IXS with 3rd Generation Synchrotron Sources
Data taken on APS ID3
2.2 meV resolution
109 incident flux
Data shown took 6 hrs
TiOCl
E. Isaacs, Y. Lee, D. Moncton
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MIT X-ray Laser Project
Large IXS Signal Gain with Bandwidth Seeded X-ray Laser
3 x 1011 photons/pulse at 1 kHz = 3 x 1014 ph/sec
Bandwidth seeding: 100 fs = 20 meV (P = 0.1nm)
1013 ph/sec at 1 meV resolution
Bandwidth seeding: 1 ps = 2 meV
1014 ph/sec at 1 meV
Compare with 109 ph/sec at 3rd Gen Sources
An intensity gain of 4-5 orders of magnitude willrevolutionize the study of the dynamics of
condensed matter
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MIT X-ray Laser Project
Transient Grating Spectroscopy
or Time-Dependent IXS
Keith Nelson, Chemistry Department, MIT
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MIT X-ray Laser Project
Accessible phase space
Time-Dependent Methods
Inelastic Scattering
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MIT X-ray Laser Project
The Potential of a Transform-Limited X-ray Laser for
Inelastic X-ray Scattering
1010 ph/sec in 1 meV bandwidth
S/N still too low for many experiments
Phenomena with (E < 1 meV not resolved by IXS
Generally phenomena with 1 ns > (t > 1 ps are inaccessible
Bandwidth Seeded X-ray Laser
Up to 1014
ph/sec in meV bandwidthTransform-limited pulses reach Heisenberg limit (t ([~ T
Time-dependent (or pump-probe) IXS for full t/E coverage
Third Generation IXS
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MIT X-ray Laser Project
Photon pulses would be ³transform-limited´ satisfying the
Uncertainty Principle in all six phase-space dimensions
Transverse Phase Space
(x (y ~ 100 microns
(k x (k y ~ 10-5 nm-1
Longitudinal Phase Space
(t ~ fs 1ps ([beV 2meV
Note that all 1011 to 1014 photons in each pulse wouldoccupy the same quantum state
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MIT X-ray Laser Project
To realize such a source, the most sophisticated laser
and accelerator technology must be integrated together.
The laser generates the coherent signal
MIT Ultrafast Laser Group
Franz Kaertner,E
rich Ippen, et al
An accelerated electron beam amplifies andfrequency shifts the laser radiation
MIT Bates Laboratory
William S. Graves et al
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MIT X-ray Laser Project
Self-Amplified Spontaneous Emission (SASE)
e-
Argonne APS first demonstrates
SASE at optical wavelengths
Gain of 107
LCLS project at SLAC aims to
demonstrate SASE at 0.15 nm
~100 fs
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MIT X-ray Laser Project
X(fs) ([[
The SASE radiation is powerful, but noisy!
One solution: Impose a strong coherent modulation with
an external laser source
A SASE FEL amplifies random electron density modulations
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MIT X-ray Laser Project
To Produce Transform-Limited Pulses below 10 nm
Must get powerful short-wavelength seeds using High
Harmonic Generation methods
Then use ³cascaded´ High Gain Harmonic Generation
methods in FEL
Inputseed [0
1st stage 2nd stage «Nth stage
Stage 1 output at
5[0 seeds 2nd stage
Stage 2 output at
25[0 seeds 3rd stage
«Nth stage
output at 5N[0
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MIT X-ray Laser Project
Two different seeding regimes
Seeding for short (1 fs) pulses²bandwidth of a few eV
Seeding for narrow (meV) bandwidth²pulse lengths 0.1 ± 1.0 ps
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MIT X-ray Laser Project
High pulse rates provide for many independent beamlines
CW operation provides much greater beam stability
Most important is minimizing electron arrival time jitter
Superconducting linac
technology is essential
Developed
at DESY
Seeded FEL requires 10 fs timing stabilityat short wavelengths
CW Superconducting cavities will havemuch less phase jitter
4.0
4.5
5.0
5.5
6.0
0 100 200 300 400
Time (s)
P h a s e : K l y s t r o
n - M O A ( d e g )
= 0.14° (150 fs)
Measured inside 10 s window
Copper linacs like Bates or LCLS have jitter of 100·s of femtoseconds
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MIT X-ray Laser Project
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MIT X-ray Laser Project
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MIT X-ray Laser Project
0.3 nm 0.1 nm
UV Hall X-ray Hall
Nanometer Hall
SC Linac
4 GeV2 GeV1 GeV
1 nm
0.3 nm
200 nm
30 nm
10 nm
10 nm
3 nm
1 nm
Main oscillator
Pump
laserPump
laser
Seed
laser
Seed
laser
Seed
laser
Pump
laser
Fiber link synchronization
Injector
laser
Undulators
Undulators
Undulators
Upgrade: 0.1 nm
at 8 GeV
SC Linac
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MIT X-ray Laser Project
LCLS performance fromSL AC website parameter
table.
MIT beamlines are 1 kHz.LCLS is 120 Hz.
MIT covers wide spectrumsimultaneously withmultiple undulators.
LCLS limited by undulator lattice to spectrum shown,
must tune energy for different wavelengths.
Note steep falloff at shortwavelength for MIT due togun performance and 4GeV energy.
Change in performance at5 nm is due to beam
energy change from 1GeV at longer wavelengths to 4 GeV.
This is conservativespectral flux density for MIT. A 2 ps long pulsewould have 10 times theflux in 1/10 the bandwidth.
Narrow bandwidth performance for MIT and LCLS
P h o t o n s p e r s e c o
n d
Wavelength (m)
12.4 eV 124 eV 1.24 keV 12.4 keV
MIT UV(X = 200 fs([ = 10 meV
MIT X-ray
(X = 200 fs([ = 10 meV
LCLS(X = 200 fs([ = 4 eV
MIT3rd harmonic
LCLS(X = 200 fs([ = 10 meV
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MIT X-ray Laser Project
Wavelength (m)
P h o t o n s p e r s e c
o n d
12.4 eV 124 eV 1.24 keV 12.4 keV
MIT UV
LCLS
1 fs
10 fs
3 fs
30 fs
1 fsCPA
MITX-ray
0.5 fs
Photons per second
assuming FEL
output fromthe short pulselengthsshown. LCLS uses electronbeam slicing, MIT uses shortseed pulse.
MIT beamlines are 1 kHz.LCLS is 120 Hz.
Dots are minimum FWHMpulselengths using FEL gainbandwidth.
CPA pulselength accountsfor bandwidth and slippage.
CPA can be used at longer wavelengths also. Slippagelimits the min pulse length tobe near the values shown ateach wavelength. The pulse
intensity would be increasedby 1-2 orders of magnitude.
Bandwidth ranges from 5e-4at 0.3 nm to 1e-2 at 200 nm.
Short-pulse performance for MIT and LCLS
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MIT X-ray Laser Project
Chirped Pulse Compression
didf
P!d)
t
100 fs
2eV
20 meV
PiPf PiPf
For compression: 100 fs to 1 fs
Energy chirp/bandwidth > compression
Reflectivity/layer< pulse chirp
But extinction depth~ few pulse lengths
Crystal chirp > pulse chirp
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MIT X-ray Laser Project
MIT Ultrafast Laser Group is developing:
Overall laser timing and synchronization below 10 fs
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MIT X-ray Laser Project
MIT Ultrafast Laser Group is developing:
RF phase control and stabilization
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MIT X-ray Laser Project
MIT Ultrafast Laser Group is developing:
Powerful short wavelength seed lasers
Phase
Controlled
5fs, 5mJ,
1 kHz
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MIT X-ray Laser Project
High-Harmonic Generation with Noble gas jets (He, Ne, Ar, Kr )
XUV @ 3 ± 30
nm
L= 10-8
- 10-5
Recombination
Propagation
-Wb
[XUV
E n e r g y
X
x
Xb
0
Laser electric field
Ionization
Phase
Controlled
5fs, 5mJ,
1 kHz
MIT Ultrafast Laser Group is developing:
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MIT X-ray Laser Project
A focused, concept-driven R&D program is a pre-requisite
to an X-ray Laser User Facility incorporating many
beamlines and seeding for full coherence Execute the critical laser related R&D to achieve necessary seedpower, wavelength, pulse duration, and timing synchronization
Work in collaboration with ANL, BNL, DESY to demonstrate seeding
and cascaded HGHG.E
stablish a facility at 100 nm for experimental use Work in collaboration with DESY, Jlab, Cornell and others to optimizeSC RF technology for CW applications w/ 10-5 amplitude control
Explore a new concept pioneered at Bates for greatly simplifying RFsystems and significantly reducing costs
Develop high rep-rate, high-brightness photoinjector and drive laser incollaboration with LBNL
Collaborate with ANL and NHFML to optimize the LCLS undulator design for variable gap performance
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MIT X-ray Laser Project
1. Cascaded HGHG experiment. Future x-ray FEL facilities that generate fullycoherent radiation will require multiple cascaded HGHG stages starting from along wavelength seed laser.
2. Chirped pulse amplification using HGHG. Seed FEL with frequency-chirpedlaser, amplify, and compress optical pulse to produce high power, short timeduration output.
3. Start-to-end simulation using measured parameters. Include beam-basedmeasurements of injector RF fields, thermal emittance, photocathode laser timeprofile, undulator fields, and seed properties. Test codes including parmela, MAD,elegant, and ginger.
4. Seeding with HHG. The Quantum Optics group at MIT is developing highharmonic generation from conventional lasers for use as a short wavelength (10-100 nm) seed. This has advantages over seeding with low harmonics includingrequiring fewer HGHG stages, and generating pulse lengths approaching 1 fs.
Critical DUVFEL Experiments
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MIT X-ray Laser Project
Develop a risk-based prototyping program for all critical components
Plan for a broad and inclusive User Program appropriate for aNational Facility
Educate the scientific community to develop beamline concepts andexecute the necessary R&D to support 10 initial beamlines
Leverage this R&D program with MIT educational programs to
involve graduate students, undergraduates, K-12 students andteachers
And finally«.
Develop the overall conceptual design, cost and schedule
data necessary for a decision to construct
We propose a 3-year $15M collaborative effortcentered at MIT
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MIT X-ray Laser Project
Conclusions: Technical
A multi-beamline X-ray Laser User Facility can be conceived based on
existing technology combined with a focused 3-year R&D program.
A modular approach with 2 or more stages with increasing linac energywould be a systematic approach, establishing capabilities and provingtechnology at various cost/performance points versus wavelength.
Lower emittance electron guns would have enormous impact, enabling x-ray wavelengths to be reached at conventional (6-8 GeV) energies.
Seeding technology would greatly improve performance with highlysynchronized transform-limited pulses, and seeding reduces undulator gain lengths and associated costs.
CW SC RF is probably essential for synchronization stability, and sincecryogenic costs rise rapidly with linac energy and gradient, the lower electron energies achieved with lower emittance guns will be veryimportant. Possible pulse structures are strongly influenced by this choice.
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MIT X-ray Laser Project
Conclusions: Scientific
Transform-limited beams from seeded sources will enable science wellbeyond SASE, for example . . .
Seeding for narrow bandwidth will enable pulses as long as 1 ps to havea bandwidth of 2 meV. SASE sources monochromated to meV levels havelarge fluctuations and low photon flux.
Seeding with for short pulses using CPA combined with ³compressionoptics´ may allow femtosecond pulses containing 1011 photons or more.This is significantly higher than SASE and of crucial importance for molecular imaging, and chemical dynamics studies.
Finally, I believe that virtually all experiments carried out at 3rd generation
sources are easily accomplished on such a source at lower facility cost.This will not be an exotic facility for only niche experiments, but representsa source of extraordinary power and flexibility with which all x-rayexperiments possible can be done.