david e. moncton- an x-ray laser at the transform limit: technical challenges and scientific payoff

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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




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




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




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




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:




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




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




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




Transient Grating Spectroscopy

or Time-Dependent IXS

Keith Nelson, Chemistry Department, MIT




Accessible phase space

Time-Dependent Methods

Inelastic Scattering




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




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




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




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




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




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




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




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




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




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




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




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




MIT Ultrafast Laser Group is developing:

Overall laser timing and synchronization below 10 fs





RF phase control and stabilization





Powerful short wavelength seed lasers

Phase

Controlled

5fs, 5mJ,

1 kHz




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





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




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




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




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.




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.

david e. moncton- an x-ray laser at the transform limit: technical challenges and scientific payoff

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