5th Generation XFEL
Fifth Generation Light Sources
X-ray FELs Based on New
Accelerator and Undulators
J. Rosenzweig, UCLA
DESY Advanced X-ray FEL Development
22 May 2014
1
5th Generation XFEL
The X-ray FEL is enormous. Challenge is to fit this…
1 km
Into this…
5m
The university lab scale FEL
UCLA first demonstrated SASE
FEL in this environment; return?
2
5th Generation XFEL
What’s wrong with the status quo?
•
Existing facilities are large, this means:
– High-cost Limited access
– Limited access Risk to science
• Pressure to publish in every experiment
• Beam time precious; hard to verify experiments by other teams
– Result: Pace of science is slowed, quality may be compromised.
FLASH 2005
LCLS II 2017
LCLS 2009
XFEL 2015
SACLA 2012
FERMI 2010
SwissFEL 2017
PAL-XFEL 2015
5th Generation Light Source:
Re-invent XFEL to fit in campus laboratory
3
5th Generation XFEL
Historic need for light sources
To advance science… build a better instrument
We can look outward a
telescope, seeing backwards in
time to the Big Bang…
Or we can utilize a
microscope
With HEP accelerators, microscope sees infinistesimal
distances <10-18 m. Exceed Hooke by factor of trillion…
Galileo Galilei with the Doge of Venice
λ~hc/U
U = particle energy
4
5th Generation XFEL
The path to discovery has led to
very high energy: MeV->TeV
• Enabled by accelerators
• Exponential growth in t in
available energy U
• Livingston plot: “Moore’s
Law” for accelerators
• Now beams are at TeV
• An expensive success
story…
– LHC (Higgs discovery) ~ $10B
1930 1940 1950 1960 1970 1980 1990 2000
Moore’s law for HEP discovery 5
5th Generation XFEL
Accelerators started small now dominate
science, industry, medicine…
An adventure in innovation for
nearly a century, from betatron…
To the largest machines ever built.
The U=1 MeV betatron (1940)
6
5th Generation XFEL
The CERN site for TeV scale physics
The Large Hadron Collier
7
5th Generation XFEL
A giant lives under the mountains
27 km circumference
Costly, complex as a moon shot
8
5th Generation XFEL
Accelerator energy, size limits
• Fatal effect in circular accelerators:
synchrotron radiation power loss
– Future electron colliders foreseen linear
– Large R circular machines
• Scaling in size/cost prohibitive
– Acceleration < 35 MeV/m
4
U
Ps ∝ 2
R
• Big $cience should shrink
The science behemoth: ~TeV linear collider
50 Km/$1010 seem to be the limit…
9
5th Generation XFEL
The light source: from particle
physics “parasite” to essential tool
• Accelerators used as synchrotron light sources for >40 years
• HEP vice (1st generation) turns to an imaging virtue. Dozens of
X-ray facilities worldwide, $B’s invested
• Workhorse of biology, materials, nanoscience
Soleil 3rd generation
light source
Form similar to HEP
accelerator
Note use of
to HEP linac!
High brilliance, but
incoherent X-rays
Example: X-ray protein
10
crystallography
5th Generation XFEL
The 4th generation light source:
the X-ray Free-Electron Laser
• Also large linear accelerator (km, E=15 GeV)
• Now: coherence, brightness, and fs resolution
SLAC 2000:
Dedicated to HEP
The first X-ray FEL
at SLAC: Coherent
X-rays!
SLAC 2010:
Dedicated to FEL
Note use of
to HEP linac
Light sources — before: HEP spin-off,
now: “competitor” in big science (>$1B)
11
5th Generation XFEL
Essential ingredient of FEL:
high brightness electron beam
• High phase space density (cold, focusable, intense)
• Measure: high brightness
2I
Be =
ε
2
x
• Space-charge (plasma) effects strong
in high brightness beams
Phase space
Density map
The secret:
RF photoinjector
(UCLA expertise)
Area=εx
emittance
Area (temperature) small
Peak density large
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5th Generation XFEL
High brightness electrons beget
high brightness photons
• FEL is cold beam instability
• Growth from e- beam brightness
1/3
λu
ρ1D ∝ Be
Lg,1D =
4 π 3 ρ1D
• High λ (short pulse), small εx gives
dense lasing medium
(
)
Erad ∝ exp z/ Lg ; Lg ∝ Be−1/ 3
• Gives +8 orders of magnitude
photon brightness:
femtosecond, coherent X-rays
revolution in “4D” imaging!
High Field RF photoninjector,
emits single component, cold
relativistic plasmas…
13
5th Generation XFEL
UCLA perspective: 1st 4 generations of FEL
UCLA 16-mm
FEL:
1stTaking
SASE
SASE Process
Just
Off gain
LANL/UCLA 1st high gain SASE
IR Detector Signal [mV]
70
60
50
Spontaneous @ 16µm, within žc
16µm within žc
Ginger - normalized to 0.2nC data
Fit
40
30
20
10
0
0.2
0.3
0.4
0.5
0.6
Charge [nC]
M. Hogan et al., Phys. Rev. Lett., 80, 289–292 (1998).
M. Hogan et al., PRL, 81, 4867–4870 (1998).
Saturation at UCLA-led
VISA ~800 nm
LCLS, 1.5 Å,
April 2009
courtesy G.
Andonian
14
A. Murokh, et al., Phys. Rev. E 67, 066501 (2003)
5th Generation XFEL
What’s next: the 5th
generation ultra-compact FEL
• High brightness beam (HBB)
– low charge (pC), ultrashort pulses
– Ultralow emittance
J.B. Rosenzweig, et al., Nucl. Instruments Methods A, 593, 39 (2008)
• High field, short  undulator
– With HBB, large ⟩ , short Lg
• Lowers e- energy needed to
reach short wavelength
Hybrid cryo-undulator: Pr-based,
SmCo sheath;  =9 mm up to 2.2 T
– Ex: 2 GeV hard X-ray FEL
– Much smaller accelerator, undulator
• Utilize high gradient accelerators
to shrink the FEL dramatically
F.H. O’Shea et al, PRSTAB 13, 070702 (2010)
FEL w/1 pC driver at 2.1 GeV
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5th Generation XFEL
Generation 4.1: state-of-art injector
and ultra-short period undulator
Goal: Enable compact soft-X-ray FEL
(Keck proposal) at UCLA using shortperiod MEMS undulator. First step in
miniaturization.
No “advanced accelerator” yet
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5th Generation XFEL
MEMS electromagnetic undulator
~30 µm
– ADD SOLENOID
Current
Cartoon
~50 µm
– Label the picture
• ADD NOW AND THEN
CHART
r
B
Soft magnet
core
Saturation limits fields…
200 µm
Windings
Very short period enabled:
20-800 microns
Batch-fabricated electromagnets
17
5th Generation XFEL
(1)
MEMS process(quad!)
(2)
(3)
(4)
(5)
18
5th Generation XFEL
MEMS electromagnetic quadrupoles
Currently Available
Future
Technology
Permanent Magnet Quadrupole
μmachined Electromagnets
∇B
560 T/m
>3,000 T/m
Inner diameter
5 mm
200 μm
Tuning
Axial translation of magnets
Electromagnet
Top View
Mag. flux density, x-component
Top metal
Bore
Vias
200 µm
19
5th Generation XFEL
First MEMS quads proven
J. Harrison, et al., submitted to Applied Physics Letters
20
5th Generation XFEL
Micromachined undulator
• Advantages and
challenges with new
technology
2
λu (1+ K 2 ) Scaling
λr =
favorable
2γ 2
qB0 λu
K=
2 2π m0 c
Scaling a
challenge
λu
How do we use this “weak” undulator (K<0.1)?
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5th Generation XFEL
UCLA Keck FEL proposal:
High brightness beamline
New
To New
Undulator
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5th Generation XFEL
Beam parameters for injection
into Keck FEL microundulator
Beam energy
Beam charge
63 MeV
20 pC
Beam emittance
Energy spread
Pulse length (FWHM)
Peak current
0.2 mm-mrad
0.1 %
70 fs
~300 Amp
Excellent beam performance, compression w/o chicane
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5th Generation XFEL
Hybrid SW/TW Hybrid Photoinjector
No Reflection
Standing
Wave Cells
25 MW RF in
IC
Velocity Bunching
Post-acceleration
RF Gun
Traveling Wave Cells
3 m linac (Option)
Laser
(1/4 + 1/6 )
• Compact high brightness beam source integrated with RF gun
(low emittance) + velocity buncher (high peak current)
• Post acceleration for high current, moderate energy beam
• Diminish RF reflection from the cavity. Scale also to X-band
Energy
Bunch length
120
3.5e-4
100
Gamma factor
sigmaz(m)
3.0e-4
2.5e-4
2.0e-4
1.5e-4
1.0e-4
60
40
20
0.5e-4
0
0.0
GPT
80
0.5
1.0
1.5
2.0
2.5
3.0
z (m)
3.5
4.0
4.5
5.0
5.5
0.0
GPT
0.5
1.0
1.5
2.0
2.5
3.0
z (m)
3.5
4.0
4.5
5.0
5.5
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5th Generation XFEL
RF commissioning completed
RF IN
RF Out
RF Pulse
Solenoid+Gun
Test Bench at Pegasus Lab, UCLA.
Hybrid successfully commissioned up to 13 MW 3.5 µs (1 Hz)
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5th Generation XFEL
Preliminary measurements (2013)
-
Measured beam dynamics PRF=11.5 MW
Strong velocity bunching observed
Validate model, hybrid characteristics
Next measurements underway
24”
Mirror
Box
IG
51” 57.25” 62.5” 71.25” 79.5”
36.5”40.5”
45.5”
Deflector Dipole
FC
Slit
Gun
GV
screen
IP 100
R6”
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5th Generation XFEL
MEMS+HBB enable new type of FEL
• Microundulator has unprecedented short period, but
not higher field. Thus…
• Microundulator K is weak, <0.1 for λu< 1 mm
• Gain length relatively long due to coupling
• Increase beam-field coupling not via wiggle, but by
focusing electrons: enhanced gain medium
• Solution: MEMS microquadrupoles ( to 3 kT/m)
• Unprecedented small beam size (<10 µm), dense HBB
Gradient beats previous best (UCLA PMQs) by factor of 5
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5th Generation XFEL
Space charge effects in FEL
• With sub-mm period undulator, soft X-ray
machine is in ~100 MeV range (not few GeV)
• Dense beam gives space charge response:
measured by “plasma skin depth” kp-1 ~ γ-3/2
• Approaches relevant scale lengths
– Transverse kp-1 ~ , must focus stronger
– Longitudinal kp-1 ~ L1D, longer gain length
Apply more
focusing to
overcome trans.
repulsion
Longitudinal repulsive self forces oppose microbunching
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5th Generation XFEL
Space charge gives more FEL efficiency
• Gain length increased (recent UCLA analysis)
Lg,R / Lg,1D ≅ 2.6kpLg,1D
G. Marcus E. Hemsing, J. Rosenzweig, Phys.
Rev. ST Accel. Beams 14, 080702 (2011)
• Efficiency also increased!
– A. Gover and P. Sprangle, IEEE
J. Quantum Electron. 17, 1196 (1981)
ηR / η1D ≅ 3.46kpLg,1D
More E-field demanded for bunching
Large efficiency increase possible
Lg

Termed “Raman regime” kp Lg,1D > 1
Typical of µwave FEL with  u ~ few cm!
Microundulator gives soft-X-ray Raman FEL
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5th Generation XFEL
Example:
Water window Raman regime FEL
• Parameter list for highly focused microundulator based SASE FEL
Without extra focusing, 8 m saturation for nm FEL (J. Harrison, et al., PRSTAB 15, 070703 (2012)
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5th Generation XFEL
Simulation validation
• Saturation length increased as expected
• 30 MW peak power, effective efficiency
⟩ =5x10-4; 2.3x value from gain length
Very compact, soft X-ray biology FEL enabled
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5th Generation XFEL
UCLA KecK EUV FEL
• With the Keck proposal and compact
accelerator, we can reach λ=26 nm
– FEL like Fermi or FLASH in small UCLA lab
Compact FEL
~20 MW peak power
2.5E11 photons (50 eV)
But what about the accelerator? Hard X-rays?
32
5th Generation XFEL
Shrinking the accelerator for FEL (or collider):
some popular views…
Well, it does destroy
the sample…
The IKEA proposition:
“Mïniåtur Linjår Cjöllider or
Frei Elëktrœn Lāzr”
5th Generation XFEL
Shrinking the accelerator
• Higher E (>GV/m): shorter λ (E~λ−1); THz down to IR
–
–
–
–
–
Need much smaller ε
Small Q (beam loading/eff. Q∼λ2E~λ). Synergy with brightness, FEL
Losses -> dielectric at short λ -> photonics
Breakdown considerations -> dielectric -> plasma
Sources? Laser (to mid IR). THz? From wakefields…
Photonic structure (woodpile) wakes; as constructed at UCLA (left)
5th Generation XFEL
What is optimum scaling of λΕΜ?
• Lasers produce copious power (~J, >TW)
– Scale in λΕΜ by ~5 orders of magnitude
– GV/m fields possible, “only” two orders of magnitude greater
• Avalanche breakdown limited… quantum energy is large
0.03
Laser wavelength accelerator
longitudinal dynamics: few % δp/p stability range...
0.02
δ p/p0
0.01
0.00
α EM ≡
-0.01
-0.02
-0.03
0.0
0.2
0.4
0.6
0.8
1.0
qE0
∝ λEM
kzm0 c2
α EM << 1
δ pmax
p0
kzζ /2π
• To jump to GV/m, longer λEM may be better:
– Beam dynamics(!), breakdown scaling
– Need new power sources for THz spectral range
• OPA lasers (mid-IR),
• Wakefields: start here…
=
4α EM γ 0
β02
5th Generation XFEL
New paradigm for high
field acceleration:
wakefields
Wakefields in dielectric tube
Driving & accelerrating beams
• Coherent radiation from bunched, v~c, e- beam
– Any slow-wave environment (metal, dielectric, plasma)
– Resonant or short pulse operation
– THz within reach
• High average power beams can be produced
– Tens of MW, can beat lasers
– Motivates CLIC-like schemes
5th Generation XFEL
Breakdown threshold: many GV/m
longer
bunch
ultrashort
bunch
Post mortem images (1st vaporize Al
coating, next damage Si02)
Breakdown determined
by benchmarked
simulations (OOPIC)
Breakdown limit:
5.5 GV/m decel. field
(10 GV/m accel.?)
Multi-mode excitation – 100 fs, pulses separated by ps
— gives better breakdown dynamics
Multi-GV/m in the sights for laser accelerator and DWA
M. Thompson, et al., PRL 100, 214801 (2008)
5th Generation XFEL
THz Coherent Cerenkov
Radiation (CCR) from DWA
• FFTB gone … moved expt to UCLA
• Chicane-compressed (σz<200 µm),
Q=0.3 nC beam @ Neptune
– PMQ focuses to σr~100 µm
(a=250 µm)
• Autocorrelation of CCR pulse
• Single mode operation
– Two tubes (diff. b), 2 THz frequencies
– Extremely narrow line width in THz
• Long wave trains from low vg
A. Cook, et al., Phys. Rev. Lett.
103, 095003 (2009)
Spin-off: Higher power, lower bandwidth than THz FEL
5th Generation XFEL
Back online at SLAC: FACET —
20 GeV wakefied facility
• 3 nC, <20x20 um
beams
• 15 cm long structures
• 2.3 GV/m sustained
acceleration, now!
– No observed damage
5th Generation XFEL
Pulse shaping: reaching high
transformer ratios
• Make wakefield acceleration more
powerful
• Reach high (FEL) energy with single
DWA module?
• Enhanced transformer ratio with
ramped beam
Eacc,witness
R≡
Edec,driver
• FEL scenario: 0.5-1 GeV ramped
driver; 5-10 GeV X-ray FEL injector in
<10 m
– Matches length of
advanced undulator
Symmetric beam R<2
Ramped beam R>>2
5th Generation XFEL
Example: DWA-driven 5th
generation light source
• Beam parameters: Q=3 nC,
ramp L=2.5 mm,U=1 GeV
Possible at SLAC FACET
• Structure: a,b=100,150 µm, ε=3.8;
fundamental @ f=0.74 THz
• Performance: Ez>GV/m, R=9-10
• Ramp achieved at UCLA, BNL
• Enables hard X-ray source w/high
average power, small footprint?
• Ongoing work at FACET, BNL
– Advanced slab structures
– Photonics!
– New materials
Ramped beam using sextupole-corrected
dogleg compression
Longitudinal phase space
R. J. England, J. B. Rosenzweig, and G. Travish,
after 1.3 m DWA (OOPIC)
PRL 100, 214802 (2008)
Longitudinal wakefields
with ramped beam
5th Generation XFEL
Past Breakdown: Plasma Accelerators
Intense laser or relativistic e- beam excites plasma wake
PlasmaSchematic
wakefieldofaccelerator
(e-beam
driven)
laser wakefield
Accelerator
(LWFA):
charge waves give large E-field
>1 TVm accelerating fields in
UCLA FACET IIPWFA experiment
Extremely high fields possible: E(V/cm) ∝ n (cm-3 )
e
Ex: atmospheric gas density
E ∝1 TV/m, for ne =10 20 cm -3
LHC-class energies in the length of an automobile?
5th Generation XFEL
Plasma Accelerators History:
Livingston Plot Bis
Equivalent fixed
target energy 2
Ub ≈
LHC
UCM
2mt c2
E167
Plasma accelerators
(actual, not “equivalent”)
5th Generation XFEL
PWFA doubles highest energy linac
• Acceleration gradients
of ~50 GV/m
(3000 x SLAC linac)
• Doubled 45 GeV beam
energy in 1 m plasma
• Required enormous
infrastructure at SLAC
• Still not yet a “beam”
I Blumenthal et al., Nature 445
741 15-Feb-2007
NB: “witness beam” acceleration
observed in latest round of experiments
(data unreleased)
5th Generation XFEL
5th generation injector based on PWFA
• To ε<10-8 m for low energy XFEL; new approaches needed
• Very high field at beam birth, use PWFA in controlled fashion
• “Trojan Horse” injection
– Load e- only in narrow r,z,t window with laser, selective ionization
– E210 at FACET underway (same team as E201)
B. Hidding, et. al., PRL 108, 035001 (2012)
Trojan Horse Injection
E210 current layout
Parametric emittance study for
Trojan horse injection (Xi et al.)
5th Generation XFEL
Pulse shaped PWFA driver for low
energy X-ray FEL
• Inject with Trojan scheme
– Ultra-high brightness beam
• FEL scenario: ramped driver
– 5-10 GeV X-ray FEL injector, <10 m
– SLAC-UCLA-Strathclyde-DESY
collaboration
– FACET context; FEL goal
– Example: 500 MeV driver, 9 mm
period undulator gives nm X-rays
Ramped beam driver
20 GV/m, R=10 PWFA
5th Generation XFEL
Laser wakefields (LWFA) already create high
quality electron beam
• Breakthrough 10 years ago
• Trapped plasma e-’s in LWFA
– Gives εn~1E-6 m-rad at Nb~109
• Narrow δE/E produced
– accelerating in plasma channels
• Looks like a beam!
– Applications to FEL
– Betatron radiation
– Less $ than e-beam wakes…
40 TW, 37 fs
Record now >2 GeV
W.P. Leemans et. al, Nature Physics 2 (2006) 696
Early LWFA beams
5th Generation XFEL
LWFA 5th generation XFEL light source
(Couprie talk for update)
MPQ-centered (Uni. Hamburg) collab.
Pushed R&D
for short λ
cryoundulato
r
Record now >>2 GeV
(HZB-UCLA)
W.P. Leemans et. al, Nature Physics 2 (2006) 696
5th Generation XFEL
GALAXIE: An Illustrative Example of
Integrated Table-top X-ray SASE FEL
GALAXIE: GV-per-meter AcceLerator And Xray-source Integrated Experiment
Ultra-high brightness
electron source
1 m 800 MeV Dielectric
Laser Accelerator
~2 m EM undulator
(λ=100 um)
Long wavelength
(5 um) laser source
All EM system with GV/m fields
Supported by DARPA AXiS Program
5th Generation XFEL
Dielectric laser accelerator (DLA)
• Dedicated DARPA program last 2 years (AXiS)
• SLAC experiments make a splash in Nature
• Uses 800 nm laser, simple structure
– Non-optimized
• Demonstrated >300 MV/m fields (∆U~100keV)
• GALAXIE @ UCLA…
5th Generation XFEL
The DLA Design Philosophy
• Why dielectrics for laser?
– Dissipation and breakdown in metals
• Why photonic structures?
– Natural in dielectric (confinement)
– Advantages of burgeoning field Laser pulses
• design possibilities
• fabrication
• Why slab-type geometries?
180 degrees
out of phase
e-beam
Biharmonic ~2D structure
– Highly asymmetric (P available!)
– Longitudinal wakes, Q limits
– Transverse wakes
• Dynamics concerns
• External coupling schemes
Schematic of GALAXIE
monolithic photonic DLA
5th Generation XFEL
Example: GALAXIE accelerator structure
Hole ID=800 nm
2 um
e-beam
propagation
Close up of beam
channel in GALAXIE
traveling wave DLA
• Single material (Si, Al2O3) photonic structure, easier fabrication
• Rich space-harmonic spectrum for 2nd order focusing (resonant TW
defocusing)
B. Naranjo, A. Valloni, S. Putterman, J.B. Rosenzweig, PRL 109, 164803 (2012)
• Fully 3D photonic structure (mode control)
• Optimized E-field w/“teeth”; small E in dielectric
5th Generation XFEL
New beam dynamics in DLA: 2nd
order focusing and adiabatic
compression
GALAXIE example: Adiabatic: (1) focusing (2) capture
(3) compression (x1000!)
5th Generation XFEL
DLA fabrication is challenging
• Very high aspect ratio features
(e.g. 0.8 x 200 um holes) for
photonics, wide beams
• Utilize macroporous silicon etching
Mask for etching
Cross-section of photonic array
5th Generation XFEL
Collective effects: wakes in
photonic DLAs
•
•
•
•
Scaled experiments in THz at BNL ATF
Bragg (1D photonic slab structure)
Woodpile (3D photonic structure)
Both results to PRL…
Bragg structure
Woodpile schematic
Simulated wakes (side view)
Narrow-band mode confinement
Measured emitted spectrum: modes in pass-bands
5th Generation XFEL
The front-end: generating very
HBB electron beams
• Photoinjector at extreme field (>175 MV/m), short RF
pulse
• Very low charge (1 pC for GALAXIE)
• New phase space manipulations
– magnetized beam emittance splitting
GALAXIE super-S-band gun
(UCLA-RadiaBeam)
From Valloni et al.
Beam after emittance splitting
Normalized Emittance
εn-,εn+=2.9×10-9, 2.6×10-7 m-rad
5th Generation XFEL
µm beam manipulation/diagnostics
Manipulating sub-um beams: ultra-short focal length
optics with microquads/dipoles
Reconstructed phase
Reconstructed profile
Incoherent (detuned) OTR
Coherent transition radiation imaging reconstruction expt.,
A. Marinelli et al., PRL 110, 094802 (2013)
• Measure sub-um beam sizes? Coherent
imaging (borrowed from XFEL!)
5th Generation XFEL
Next generation undulator:
Electromagnetic waves
Tantawi X-band SW undulator
Undulator Mechanical Structure
Electric Field Distribution
• To use <1 GeV in XFEL, need λu=100 um
• K~0.1 or above: T-level B0 inadequate
• On to EM undulators:
– THz SW structures,
– IR TW guides
– Free-space Thompson
Chang et al. PRL 110, 064802 (2013)
5th Generation XFEL
2 DLA-based 5th generation sources
Optimized
350 MeV
GALAXIE
Unprecedented short beam from DLA, permits
use in SASE FEL, super-radiant cases
Super-Radiant Case
σz=2.3 nm(!), Ip=870 A, σδp=0.12%
SASE hard X-ray FEL case
Quantum effects!
ρ~hν/U
UCLA-µbunching induced super-radiance
exp’t with S. Tantawi’s X-band undulator
Accelerate to 350 MeV for LCLS-like 1.5 Å
SASE FEL with ~1-m saturation (λu=100 um)
Utilize X-band undulator (proven) at 450
MeV (1.1 kA). Obtain fully coherent pulse
train of 13.5 nm light (EUV lithography λ).
Produce 3.5x108 soft-X-ray photons/pulse.
5th Generation XFEL
Conclusions
• Ultra-compact XFELs are intriguing new instruments forr
revolutionarizing wide swaths of science
– Nanoscience, biology, fs chemistry, lithography, etc.
• Opportunities to bring cutting-edge tools to wide use
• Convergence of advanced concepts
– Frontiers of bright electron beams
– First generation of microscale magnets
– Enables new FEL regime; first 5th generation light source
• Going forward
– DARPA AXiS “sequestered”. NSF and Keck are gaining traction.
– Options in optical structures, IFEL, wakefields, laser-plasma…
• Long-term impact: Fundamentally change light sourcebased science – XFEL in the basement lab!
60