LCLS-II Capabilities & Overview - Stanford University · 2015. 2. 9. · LCLS-II Science...
Transcript of LCLS-II Capabilities & Overview - Stanford University · 2015. 2. 9. · LCLS-II Science...
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LCLS-II Capabilities & Overview LCLS-II Science Opportunities Workshop
Tor Raubenheimer
February 9th, 2015
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Outline
LCLS-II Science Opportunities Workshop, February 9-13, 2015
1. Overall machine goals and layout
2. Primary parameters
• Nominal X-ray wavelength and pulse energy curves
• X-ray power
• Bunch charge versus X-ray length
• Timing and energy stability
3. Simulations of performance
4. Future enhancements
Talk largely consists of slides extracted from recent LCLS-II
reviews and much more information can be found there.
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LCLS-II Concept CW linac based on SCRF technology to complement LCLS CuRF
LCLS-II Science Opportunities Workshop, February 9-13, 2015
SCRF offers advantages in
terms of X-ray power,
stability, and repetition rate
Challenge is cost for high
energy CW accelerator and achieving comparable peak
brighness
LCLS-II will benefit from best of both CuRF and SCRF
• Use CuRF for high peak brightness at short wavelengths
• Use SCRF for very high average brightness with stable beam
and uniform bunch spacing
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LCLS-II 1.3 GHz Cryomodule Similar to EuFEL but modified for CW operation
Total length ~12.2 m Nearly the final LCLS-II cryomodule design
LCLS-II Science Opportunities Workshop, February 9-13, 2015
Cryomodules will be similar to EuXFEL with modifications for
CW operation; cavities will be processed for high Q0 operation
Baseline 16 MV/m with Q0 = 2.7x1010
CM allows 150 Watts max cooling
20 MV/m max gradient @ 2.7x1010
or 16 MV/m @ 1.8x1010
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LCLS-II Concept Use 1st km of SLAC linac for CW SCRF linac
5 LCLS-II Science Opportunities Workshop, February 9-13, 2015
with space for 7 GeV
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Revised LCLS-II (Phase II) Baseline Deliverables
Self seeding between 1.2-4 keV
requires x-ray optics development
Self seeding at high rep rate above
4keV will require ~4.5 GeV electron
beam, not a baseline deliverable
today
Cu Self Seeded
High Rep Rate SASE
Self Seeded (Grating)
Cu SASE
Photon Energy (keV)
0 5 10 15 20 25
SC Linac High Rep Rate
Cu Linac
Legend
4.0 GeV
LCLS-II Science Opportunities Workshop, February 9-13, 2015 6
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LCLS-II Accelerator Layout New Superconducting Linac LCLS Undulator Hall
LCLS-II Science Opportunities Workshop, February 9-13, 2015
• Two sources: high rate SCRF linac and 120 Hz Cu LCLS-I linac
• North and South undulators can operate simultaneously in any mode
Undulator SC Linac (up to 1 MHz) Cu Linac (up to 120Hz)
North
0.20 - 1.3 keV
South
1.0 - 5.0 keV
up to 25 keV
higher peak power pulses
• Concurrent operation of 1-5 keV and 5-25 keV is not possible
HXU
SXU Sec. 21-30 Sec. 11-20
0.2-1.3 keV (0 -1 MHz)
SCRF
4 GeV 1-25 keV (120 Hz) 1-5 keV (0 -1 MHz)
LCLS-I Linac 2.5-15 GeV
proposed FACET-II LCLS-II Linac
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FEL X-ray Performance
LCLS-II FAC Review, February 5-6, 2015
SCRF linac can deliver ~1 MHz beam to either undulator
• Undulators limited to 120 kW electron beam power
• 100 pC at 300 kHz and 4 GeV or 33 pC at 900 kHz and 4 GeV
• Goal is to provide >20 Watts in SASE over wavelength range
of 0.2 to 5 keV to experiments with good mirror figure
- X-ray Transport is designed to handle up to 200 Watts
- Maximum X-ray pulse energy is function of X-ray wavelength,
e.g. 0.9 mJ at 200 eV; 1 mJ at 1 keV; 20 uJ at 5 keV
• Soft X-ray self-seeding will provide narrower bandwidth with
pulses a few times transform-limit
CuRF linac will deliver LCLS-like bunches and mJ-scale
SASE X-ray pulses to >25 keV
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Possible Operating Modes Very flexible operation
Configuration Linac Parameters SXR HXR
High rate to SXR and
HXR
SCRF: 4 GeV, 0.929 MHz; 60 pC
CuRF: off
50-200 W at 1 keV
(120-450 uJ at 460 kHz) 20 W at 3 keV
(43 uJ at 460 kHz)
High rate to SXR and
medium pulse energy
at HXR
SCRF: 4 GeV, 0.240 MHz; 100 pC
CuRF: off
80-200 W at 250 eV
(350-900 uJ at 210 kHz) 20 W at 1.5 keV (1 mJ at 20 kHz)
Medium rate and
pulse energy at SXR
and HXR
SCRF: 4 GeV, 0.080 MHz; 100 pC
CuRF: off
20 W at 500 eV
(1 mJ at 20 kHz) 20 W at 4 keV
(0.4 mJ at 50 kHz)
High rate to SXR and
high pulse energy at
HXR
SCRF: 4 GeV, 0.410 MHz; 100 pC
CuRF: 15 GeV, 120 Hz, 130 pC
200 W at 250 eV
(500 uJ at 400 kHz) 0.5 W at 3 keV
(4 mJ at 120 Hz)
High rate to SXR and
short wavelength at
HXR
SCRF: 4 GeV, 0.929 MHz; 30 pC
CuRF: 15 GeV, 120 Hz, 130 pC
50 - 200 W at 1.2 keV
(50-200 uJ at 920 kHz) 0.1 W at 25 keV
(500 uJ at 120 Hz)
LCLS-II Science Opportunities Workshop, February 9-13, 2015
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CuRF Linac Driven X-ray Pulse Energy
LCLS-II Science Opportunities Workshop, February 9-13, 2015 H-D Nuhn 10
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X-ray Pulse Energy from SXR and HXR driven by SCRF Analytic estimates vs. simulation results
LCLS-II Science Opportunities Workshop, February 9-13, 2015 G. Marcus
SC linac + SXR 100 pC, ~50 fs FWHM
300 kHz, 4 GeV SC linac + HXR
100 pC, ~50 fs FWHM
300 kHz, 4 GeV
SXR 3w (approximate)
HXR 3w (approximate)
103 104
10-5
10-4
10-3
Photon Energy (eV)
Ener
gy/p
uls
e (J
)
102
20 pC e-beam
20 fs FWHM
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Example: 100 pC IMPACT, HXR SASE, Eγ = 2 keV
0 20 40 60 80 100 120 14010
-4
10-2
100
102
104
2 keV, energy [J]
z [m]
E [
J]
0 10 20 30 40 50 60 700
10
20
30
40
s [m]
P [
GW
]
0 10 20 30 40 50 60 700
1
2
3
4
I [k
A]Emax ~ 655 μJ
Pavg ~ 10 GW
Δt = 58 fs
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Example: 20 pC IMPACT, HXR SASE, Eγ = 5 keV
LCLS-II Science Opportunities Workshop, February 9-13, 2015
0 50 100 15010
-4
10-3
10-2
10-1
100
101
102
z [m]
E [
J]
No taper
Taper
0 5 10 15 200
0.5
1
1.5
2
s [m]
P [
GW
]
0 5 10 15 200
0.2
0.4
0.6
0.8
I [k
A]
4975 4980 4985 4990 4995 50000
2
4
6
8
10
12x 10
11
E [eV]
P(w
) [a
.u.]
ENT ~ 8 μJ
ET ~ 25 μJ
Δt ~ 18 fs
ΔEγ,FWHM ~ 2.1 eV
ΔEγ,FWHM/E0 ~ 4.2 x 10-4
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Example: 100 pC IMPACT, SXR SS, Eγ = 500 eV,
LCLS-II Science Opportunities Workshop, February 9-13, 2015
0 20 40 60 8010
-4
10-2
100
102
z [m]
E [
J]
E ~ 113 μJ after 9
downstream undulator
sections
0 10 20 30 40 50 600
2
4
6
8
10
s [m]
P [
GW
]
Δtmean ~ 20 fs
490 495 500 5050
1
2
3
4
5
6x 10
12
E [eV]
#/
eV
ΔEγ,FWHM ~ 0.22 eV
ΔEγ,FWHM/E0 ~ 4.4 x 10-4
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5 more undulator segments for
post-saturation taper if desired
Working to
understand
pedestal
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Bunch Charge and Pulse Length Charge and rate determined by 120 kW limit
LCLS-II Science Opportunities Workshop, February 9-13, 2015
LCLS-II baseline will deliver same beam parameters to both
undulators
- Specified to operate with 10 – 300 pC bunch charge @ <120 kW
- 100 pC with 60 fs FWHM; 20 pC with 20 fs FWHM
Baseline is 100 pC per bunch with roughly 60 fs FWHM X-ray
pulse length (1 kA) at 300 kHz (120 kW)
- Working on techniques to shorten X-ray pulse without changing
charge or chirp etc – how rapidly are changes desired?
- Pulse energy simply proportional to pulse length
Low charge options include 10 and 20 pC at up to 929 kHz
- Better performance (pulse energy/bunch charge)
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Nonlinear Harmonic Generation and Harmonic Lasing
LCLS-II Science Opportunities Workshop, February 9-13, 2015
• Nonlinear harmonic generation produces third harmonic
radiation at ~1% of the fundamental when K>1.5
• Harmonic lasing can produce significant radiation with a
narrow spectrum when the fundamental is suppressed
- Investigating options for harmonic lasing
- Should be reasonable to upgrade HXR undulator if needed
Fundamental 2 keV 3 keV
Bunch charge 100 pC 20 pC
3rd harmonic 6 keV 9 keV
Efficiency 1% 0.75%
Energy/pulse 1 uJ 0.14 uJ
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Stability Goals
LCLS-II Science Opportunities Workshop, February 9-13, 2015
• LCLS-II SCRF FEL will be more stable than LCLS
• Baseline specs for electron beam:
- DE/E < 0.01% rms
- DI/I < 4% rms
- Dt < 20 fs rms
- DX/sX, DY/sY < 15% rms
• LLRF has been specified to provide stability in ‘worst’ case
of correlated errors
• X-ray pulse has added intensity jitter from SASE and optics
• MHz beam rate should allow further stabilization with
addition of fast feedback systems
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Longer-Term Goals Can Provide Exceptional Stability
LCLS-II Science Opportunities Workshop, February 9-13, 2015
ENERGY
PEAK
CURRENT
ARRIVAL
TIME
Now simulate the best case:
0.01% and 0.01 deg rms jitter
and all uncorrelated Energy stable to 0.003% rms
Peak current stable to 1.8%
Timing stable to 5 fs
* The gun timing error is compressed by 3.85 from gun to 100 MeV, due
to velocity compression.
Best Case Jitter Simulations in LiTrack
See PRD: LCLSII-2.4-PR-0041
P. Emma 18
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Parameter Range for: Timing
Parameter Name
(Unit)
Ready for First
Light
Possible within
the first year or
two of operation
It could happen –
don’t laugh
Short term laser
vs X-ray jitter
<100 fs RMS* <50 fs RMS
10 fs RMS
probably the limit
X-ray vs laser 1-
day drift
1 ps 100 fs 10 fs with pulsed
fiber locking
X-ray / optical
cross correlator**
Probably not
ready
10-50 fs 10 fs
LCLS_I to
LCLS_II jitter
200 fs RMS 100 fs RMS 100 fs RMS
*Assuming full performance LLRF system for the accelerator
** if applicable for beam operating conditions
J. Frisch, July 31, LCLS-II Parameters Review
LCLS-II Science Opportunities Workshop, February 9-13, 2015 19
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LCLS-II Planned Undulator Layout Replace Existing LCLS Undulator with HXR and add SXR
32 HXU Segments
Existing Diamond Crystal
Self-Seeding System
New SXR Self-Seeding
System for High Power Loads
21 SXU Segments
Space for future upgrades? Space for polarization
upgrade?
Considering vertical polarization of X-rays from HXR line
LCLS-II Science Opportunities Workshop, February 9-13, 2015
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Enhanced Modes of operation (G. Marcus, July 31, LCLS-II Parameters Review)
• High rep-rate HXR SS
• External seeding
• HGHG
• EEHG
• ?SASE
• iSASE
• pSASE
• Harmonic Lasing
• Two-Color
• Split undulator and gain modulation
• Two-bunches
• FWM via selective amplification
• Short pulses
• low charge, beam spoiling, laser modulation, self-seeding / chirp
• Timing control
• Defined by laser
• Easy to adjust pulse duration
• Improved stability in photon energy and #
• Possibly near transform limited pulses
• Increase cooperation length
• Narrow spectrum
• Extend tuning range of FEL beamline
• X-ray pump & probe
• Four-wave mixing
LCLS-II Science Opportunities Workshop, February 9-13, 2015
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Option for complete HXR self-seeding monochromator Possible layout options not fully explored
• Two-stage diamond wake-field monochromator seeding sections and a grating
monochromator seeding section
• Seeding below 3 keV • Both diamond systems are retracted
• Seeding above 3 keV • Grating system is retracted
• Between 3 – 5 keV • Both diamond monochromators in use using (111) crystals
• Above 5 keV with CuRF linac • Only 2nd diamond mono. in use with (400) crystal
LCLS-II Science Opportunities Workshop, February 9-13, 2015 22
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Summary
LCLS-II Science Opportunities Workshop, February 9-13, 2015
• Broad capability
- High rate beam from 0.20 – 5 keV with >20 W X-ray power
- High intensity pulses with LCLS charactistics to >25 keV
• SCRF linac will provide >10x better stability than CuRF
- How best to take advantage of benefits?
- What else is needed?
• Variable gap udulators allow flexible operation
- Broad bandwidth coverage; Strong tapering; Rapid wavelength scans
• Broad spectrum of upgrade options
- LCLS is pioneering many techniques that may be implemented in LCLS-II
• Please suggest your X-ray goals
- Opportunity to modify development plans but need strong science case
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BACKUP
LCLS-II Science Opportunities Workshop, February 9-13, 2015
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Must Use Gas Based Techniques for SXR
• Design concept similar to LCLS-I gas attenuator, but
- Using Ar gas, 5 m long volume, up to 10 torr
- Differential pumping w/ 1st variable (impedance) apertures to reduce
conductance (beam size ~ 10 mm at 200 eV at location)
LCLS-II Science Opportunities Workshop, February 9-13, 2015
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Impact of Intensity Fluctuations on Gas Attenuator Beam drills hole through gas
Intensity fluctuation induced inaccuracy in attenuation ~ 10%
T (
K)
Att
n A
ch
ieve
d
Intensity fluctuation induced baseline temperature variation ~ 200 °K
Operating pressure ~ 2.5 torr, effective attenuation 5x10-4 ~ absorbed 200 W into gas detector
Y. Feng LCLS-II Science Opportunities Workshop, February 9-13, 2015
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LCLS-II (SCRF) Baseline Parameters
Parameter symbol nominal range units
Electron Energy Ef 4.0 2.0 - 4.14 GeV
Bunch Charge Qb 100 10 - 300 pC
Bunch Repetition Rate in Linac fb 0.62 0 - 0.93 MHz
Average e- current in linac Iavg 0.062 0.0 - 0.3 mA
Avg. e- beam power at linac end Pav 0.25 0 - 1.2 MW
Norm. rms slice emittance at undulator e-s 0.45 0.2 - 0.7 m
Final peak current (at undulator) Ipk 1000 500 - 1500 A
Final slice E-spread (rms, w/heater) sEs 500 125 - 1500 keV
Final bunch length (rms) tb 8.5 3 - 50 m
Avg. CW RF gradient (powered cavities) Eacc 16 - MV/m
Photon pulse length (FWHM) txray 70 10 - 350 fs
Photon energy range of SXR (SCRF) Ephot - 0.2 - 1.3 keV
Photon energy range of HXR (SCRF) Ephot - 1 - 5 keV
Photon energy range of HXR (Cu-RF) Ephot - 1 - 25 keV
See LCLSII-1.1-PR-0133
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External seeding modes
UV
seeds
radiator mod1
mod2
UV
seed
fresh
bunch
delay
mod1 rad1 mod2 rad2
EEHG
HGHG
9 fs rms
0.22 eV rms
16 fs rms 0.12 eV rms
~ 2 x transform limit
• Allows long coherent pulses
• Highly sensitive to laser quality, less so to electron bunch
• Highly sensitive to electron
bunch parameters
• Consistently poor spectrum
• QHG (with reviewers) relax
conditions on harmonic jumps
LCLS-II Science Opportunities Workshop, February 9-13, 2015
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External seeding performance and requirements
LCLS-II Science Opportunities Workshop, February 9-13, 2015
• EEHG
• Performance
- Long, coherent pulses
- Near Fourier transform limit (~ 2x FTL @ 1nm)
• Requirements
- Stable (amplitude and phase) laser @ 260 nm
- 2 chicanes and 2 modulators
• HGHG
• Performance
- Best for short pulses
- Hard to control spectrum
- Below 2 nm is pushing limits
• Requirements
- 3 chicanes (one for fresh bunch), 2 modulators, intermediate radiator
- 260 nm laser
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Harmonic lasing using 100 pC, 1 kA e-beam slice
properties
0 50 100 15010
2
104
106
108
1010
z [m]
P [
W]
Ideal beam comparison
5 keV @ fund.
5 keV @ 3rd
harm.
Additional phase shifters needed
0 50 100 15010
2
103
104
105
106
107
108
z [m]
P [
W]
7 keV
6-7 keV photons become possible
with attenuators
• Tune first undulators such that 3rd
harmonic at desired wavelength
• Tune second undulators such that 5th
harmonic is at desired wavelength and
equal to 3rd upstream
0 20 40 60 80 100 12010
0
102
104
106
108
1010
z [m]
P [
W]
E,f
~ 4.1 keV
1.38 keV
4.1 keV
0.83 keV
2.5 keV
4.1 keV
Pavg ~ 200 MW
HXR
SXR
LCLS-II Science Opportunities Workshop, February 9-13, 2015
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Two-color generation: Some recent LCLS results
• Split undulator scheme
• Gain modulation
l1,2 = lw1+K1,2
2
2g 2
LCLS-II Science Opportunities Workshop, February 9-13, 2015
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Two-color generation: Two-bunch xFEL demonstrated
at LCLS
Photocathode Laser Pulse
Adjustable delay stage
Double Pulse
Electron Gun
Linac
Few ps delay
Bunch Compressor 1
Bunch Compressor 2
Few fs delay
~1% energy separation
UNDULATOR
time time
Energ
y
Energ
y
2-color
X-Rays
Splitter
l1,2 = lw1+K 2
2g 2
1,2
LCLS-II Science Opportunities Workshop, February 9-13, 2015
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FEL for FWM
LCLS-II Science Opportunities Workshop, February 9-13, 2015
• Control of
• Timing
• Color
• Angle of incidence
• Large bandwidth, coherent short (~1-2
fs) pulses
• Can be further compressed (~0.5
fs)
• Many additional components and
significant R&D required
• Easily fits in SXR tunnel
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Ferrite Loaded Transmission Line Kicker Hardware testing has begun
• Loaded sections of ferrite and discrete capacitors
simulate a transmission line.
• 𝑓𝑖𝑙𝑙 𝑡𝑖𝑚𝑒 =𝐿𝑡𝑜𝑡𝑎𝑙×𝐼
𝑉 where we will have 3
separate kickers for 1/3 fill time ~100ns.
Recent measurements (7 out of 23)
Individual magnets
Integrated kick
T. Beukers
Test Pulser Schematic of 1m kicker
LCLS-II Science Opportunities Workshop, February 9-13, 2015
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Two-color performance and requirements
LCLS-II Science Opportunities Workshop, February 9-13, 2015
• Split undulator/gain modulation
• Performance - Peak power 5-10 x lower for both colors
- Different source points
- Only up to ~ 2.5 keV on HXR due to long saturation lengths
• Requirements - Chicane (SXR)
• Two bunch
• Performance - Both colors achieve saturation
- Smaller photon tunability due to chromatic effects in transport, on order of 1-2%
• Requirements - Beam splitter for photocathode laser
• FEL for FWM
• Performance - Short pulses
- Large bandwidth
- Flexibility in timing, photon energy, angle of incidence
• Requirements - Two modulators, four small chicanes, single-cycle mid IR laser, beam splitter, delay stages
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Parameter Sensitivities
SXR is robust at 1.25 keV; HXR is limited at 5 keV
LCLS-II Science Opportunities Workshop, February 9-13, 2015 H-D Nuhn
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Using LCLS to Benchmark IMPACT S-2-E Simulations uBI effects will be important
LCLS microbunching studies: 4GeV, 180pC, 1kA
Measured final t-p phase space vs laser heater preliminary analysis of bunching factor
D. Ratner, Y. Ding, et al. LCLS-II Science Opportunities Workshop, February 9-13, 2015
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LCLS-II Layout (P. Emma, LCLS-II FAC Review)
L2-Linac L3-Linac
HXU
SXU
Sec. 21-30
LH BC1 BC2
BC3
D2
D10
-wall
0.65 m 0.93 m
2.50 m
L1
kicker LTUH
LTUS
“glowing” sections indicate these are not in the vertical plane of either linac
LCLS-I
Linac
See PRD: LCLSII-2.5-PR-0134
(plan view - not to scale) N
ew
SC
RF
Lin
ac (
4 G
eV
)
Byp
ass
Lin
e
1s
t D
og
Leg
LT
U
Tra
nsp
ort
un
du
lato
rs
Beam
Sp
read
er
LCLS-II Science Opportunities Workshop, February
9-13, 2015
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Solid-State Amplifiers Simplify LLRF and offer better performance
LCLS-II Science Opportunities Workshop, February 9-13, 2015
• Installing
3.8 kW SSA
• Need 2.6 kW
with no f offset
or overhead
• Need 3.8 kW
with 10 Hz
-phonic offsets,
6% overhead for losses and 10 % tuning overhead
- Same power allows operation at ~ 50% duty with 60 uA at 23
MV/m with 3 Hz max detuning, QL = 6e7 and the same overheads
Linac
Sec.
V0
(MV)
j
(deg)
Acc.
Grad.*
(MV/m)
No.
Cryo
Mod’s
No.
Avail.
Cav’s
Spare
Cav’s
Cav’s
per
Amp.
L0 100 varies 16.3 1 8 1 1
L1 211 -12.7 13.6 2 16 1 1
HL -64.7 -150 12.5 2 16 1 1
L2 1446 -21.0 15.5 12 96 6 1
L3 2206 0 15.7 18 144 9 1
Lf 202 ±34 15.7 2 16 1 1
HXU
SXU Sec. 21-30 Sec. 11-20
0.2-1.3 keV (0.1-1 MHz)
SCRF
4 GeV 1-25 keV (120 Hz) 1-5 keV (0.1-1 MHz)
LCLS-I Linac 2.5-15 GeV
proposed FACET-II LCLS-II Linac
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High Level Photon Parameters Table 2 from Bill Schlotter’s LCLS-II Introduction document
LCLS-II Science Opportunities Workshop, February 9-13, 2015
Undulator Uni
ts SXR HXR
Linac SC SC Cu
Photon Energy ke
V 0.25-1.25 1-5 >5 1-25
Max Repetition
Rate kH
z 1000 1000 .12
Max Pulse Energy mJ 1.9-1.6 2.3-1.9 2.3-0.1 0.2 4.2-1.4 10-3.3
Max Power in
FEE W 200 200 1.2-0.4
Max Power to
End Station W 20 20 0.4
FWHM Pulse
Duration fs 70 fs
@100 pC 10 fs
@10 pC 70 fs
@100 pC 10 fs
@ 10 pC 25 fs
@100 pC
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Tracking a 100, 300, and 20 pC Bunch Charge (with CSR, long. wakes, and separate injector runs – ASTRA & Elegant)
LCLS-II Science Opportunities Workshop, February 9-13, 2015
Q = 100 pC ex=0.350.42 m (20%)
heater = 5.5 keV rms
jL1 = -12.7 deg
V3.9 = 64.7 MV
j3.9 = -150 deg
R56-BC2 = -37.0 mm
Q = 300 pC ex=0.610.77 m (26%)
heater = 11 keV rms
jL1 = -14.0 deg
V3.9 = 58.0 MV
j3.9 = -150 deg
R56-BC2 = -36.7 mm
Q = 20 pC ex=0.090.13 m (44%)
heater = 2.0 keV rms
jL1 = -21.0 deg
V3.9 = 55 MV
j3.9 = -165 deg
R56-BC2 = -62 mm
0.6 kA L. Wang
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HXR Components
LCLS-II Science Opportunities Workshop, February 9-13, 2015
SXR Device Symbol HXR
Count Notes
Adjustable Aperture type 1 1 New Design
Adjustable Aperture type 2 (mirror Slits) 1 Similar to LUSI
Attenuators (Gas and Solid) 1 Modifications to the existing Gas attenuator
New solid attenuator Design based on LUSI
Flat Mirror 2
No upgrades to the existing HOMS mirrors
New HOMS mirrors to cover SC energy range
Gas Energy Monitor 2 Repurposed with upgrades
High Resolution Imager 3 New design based on LUSI
In line Spectrometer 1 Repurpose existing
Mono 1 Repurpose existing
Rapid Turnaround Diagnostics Station 1 Repurpose existing
Stopper 1 New design SB
SB
PH
OT
ON
BE
AM
ST
OP
PE
R
M2H
(N
)
MIR
RO
R
IMA
GE
R
HO
MS
1 (
E)
MIR
RO
R
IMA
GE
R
AD
J
AP
ER
GA
S
MO
NIT
OR
GA
S
MO
NIT
OR
AD
J
AP
ER
RA
PID
DIA
GN
OS
TIC
CH
AM
BE
R
SP
EC
TR
OM
ET
ER
UN
DU
LA
TO
R
CE
NT
ER S
HA
DO
W
WA
LL
(E
)
K-M
ON
O
SO
LID
AT
TE
N
IMA
GE
R
GA
S A
TT
EN
M1
H (
N)
MIR
RO
R
HO
MS
2 (
E)
MIR
RO
R
XR
T &
FE
H
DU
MP
WA
LL
NE
H W
AL
L
TH
ER
MA
L B
AR
RIE
R
WA
LL
DU
MP
AR
EA
FE
E
AR
EA
NE
H
AR
EA
FE
E W
AL
L
HU
TC
H 1
AR
EA
Beam Direction
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SXR Components
LCLS-II Science Opportunities Workshop, February 9-13, 2015
SXR Device Symbol SXR count Notes
Adjustable Aperture type 1 1 New Design
Adjustable Aperture type 2 (mirror Slits) 1 Similar to LUSI
Attenuator (Gas) 1 New Gas attenuator, design similar to LCLS-I
Flat Mirror 2 New System: very low figure error, water cooled
Gas Energy Monitors 2 One repurposed system with upgrades, one new
system with similar design to LCLS-I system
High Resolution Imager 4 New System, design borrows elements from LUSI
K-B mirrors 1 New System: Bender design leveraged on CXI
system
Rapid Turnaround Diagnostics Station 1 New System, use LCLS-I design
Stopper 1 New Design SB
SBA
DJ
AP
ER
TU
RE
1G
AS
AT
TE
NU
AT
OR
RA
PID
DIA
GN
OS
TIC
IMA
GE
R
AD
J
AP
ER
TU
RE
2
IMA
GE
R
M1S
1 M
IRR
OR
SH
IELD
ING
WA
LL
M2S
1 M
IRR
OR
DU
MP
AR
EA
FE
E A
RE
A
BE
AM
ST
OP
PE
R
GA
S E
NE
RG
Y M
ON
ITO
R
IMA
GE
R AR
RIV
AL
TIM
E
WA
VE
FR
ON
T
GA
S M
ON
ITO
R
CE
NT
ER
UN
DU
LAT
OR
DU
MP
WA
LL
IMA
GE
R
FE
E W
ALL
KB
M1
HO
RIZ
ON
TA
L
KB
MIR
RO
R
EN
D S
TA
TIO
N 1
KB
M1-
VE
RT
ICA
L
KB
MIR
RO
R
TH
ER
MA
L W
ALL
NE
H
HU
TC
H-1
LCLS
Operations
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Verify RF Stability Tolerances by Tracking (P. Emma, LCLS-II FAC Review)
* The gun timing error is compressed by 3.85 from gun to 100 MeV, due to velocity compression.
PEAK
CURRENT
(<4%)
ARRIVAL
TIME
(<20 fs)
ENERGY
(<0.01%)
Jitter Simulations in LiTrack
(DE/E0)rms =
0.008%
Dtrms =
20 fs
(DIpk/Ipk)rms =
3.8%
Now verify by tracking 1000 times with random jitter
Jitter may be correlated or uncorrelated (cav. to cav.)
Include bunch charge, gun laser, & chicane supplies
uncorrelated rms
jitter tols per cavity
if jitter is correlated
(cavity to cavity)
OK
OK
OK
LCLS-II Science Opportunities Workshop, February 9-13, 2015
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200 W Requirement on Photon Beamlines Will have impact but looks achievable
LCLS-II Science Opportunities Workshop, February 9-13, 2015
• Photon beamlines have been speced to operate at 20 W
with good figure performance and 200 W
• The FEL’s can deliver >200W over much of photon range
• The 200 W requirement is to provide headroom in
operations and to allow for harmonics, …
• 200 W requirement impacts stoppers, attenuators, and
photon diagnostics
• Most issues have been resolved with small impact
• Some new challenges have been uncovered
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100 pC, 1 kA: SXR SS simulation results @ Eγ = 1.24
keV – typical run
LCLS-II Science Opportunities Workshop, February 9-13, 2015
0 20 40 60 8010
-4
10-2
100
102
104
z [m]
E [
J]
Energy gain curve
E ~ 1.5 μJ
0 10 20 30 40 50 60 700
0.05
0.1
0.15
0.2Power (blue), Current (green)
s [m]
P [
GW
]
0 10 20 30 40 50 60 700
0.5
1
1.5
2
I [k
A]
1230 1235 1240 1245 12500
2
4
6
8x 10
9
E [eV]
#
/eV
[N
]
Spectrum (blue), Filter (red)
1230 1235 1240 1245 12500
0.005
0.01
0.015
0.02
E ~ 200 μJ
0 10 20 30 40 50 60 700
0.5
1
1.5
2x 10
5 Power (blue), Current (green)
s [m]
P [
W]
0 10 20 30 40 50 60 700
0.5
1
1.5
2
I [k
A]
1238 1239 1240 1241 12420
2
4
6
8
10x 10
7 Spectrum
E [eV]
#
/eV
[N
]
0 10 20 30 40 50 60 700
5
10
15
20Power (blue), Current (green)
s [m]
P [
GW
]
0 10 20 30 40 50 60 700
0.5
1
1.5
2
I [k
A]
1238 1239 1240 1241 12420
1
2
3
4
5
6x 10
12 Spectrum
E [eV]
#
/eV
[N
]
ΔEFWHM ~ 64 meV
ΔEFWHM/E0 ~ 5.1 x 10-5
TBP ~ 4.3 eV-fs = 2.4 FTL
Saturation after 16 out of
21 undulators
G. Marcus
FWHM ~ 65 fs
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20 pC, 500 A: HXR SASE simulation results @ Eγ = 5.0
keV
LCLS-II Science Opportunities Workshop, February 9-13, 2015
0 20 40 60 80 100
10-4
10-2
100
102
z [m]
E [
J]
Energy gain curve
0 5 10 15 20 250
1
2
3
4
5
6
7Power (blue), Current (green)
s [m]
P [
GW
]
0 5 10 15 20 250
0.2
0.4
0.6
0.8
1
1.2
1.4
I [k
A]
5000 5005 5010 5015 5020 5025 50300
0.5
1
1.5
2
2.5
3
3.5x 10
11 Spectrum
E [eV]
P(w
) [a
.u.]
ΔEFWHM ~ 3.5 eV
ΔEFWHM/E0 ~ 7.0 x 10-4
E ~ 27.4 μJ
Saturation after 24 out of 32 undulators
G. Marcus
FWHM ~ 20 fs
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100 pC IMPACT e-beam slice properties, HXR
LCLS-II Science Opportunities Workshop, February 9-13, 2015
s [m]
E [
GeV
]
0 10 20 30 40 50
3.98
3.99
4
4.01
4.02
0 10 20 30 40 50-40
-20
0
20
40
60
s [m]
- 0
0 10 20 30 40 500
1
2
3
4
5
I [k
A]
0 10 20 30 40 500
0.5
1
s [m]
e n [m
m-m
rad
]
0 10 20 30 40 500
1
2
3
4
5
I [A
]
0 10 20 30 40 500
1
2
s [m]
sE [
MeV
]
0 10 20 30 40 500
1
2
3
4
5
I [A
]
head I ~ 720 A
ϵn,x ~ 0.35 mm-mrad
ϵn,y ~ 0.42 mm-mrad σE ~ 450 keV
SXR shows larger fluctuations here,
but otherwise is comparable
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SXR self-seeded geometry (LCLS)
LCLS-II Science Opportunities Workshop, February 9-13, 2015
1239 1239.5 1240 1240.5-0.2
0
0.2
E [eV]
Am
p
1239 1239.5 1240 1240.5-0.1
0
0.1
Ph
ase
• λu = 39 mm
• Lu = 3.4 (87 per.)
• Lbr = 1.0 (25 per.)
• 7 undulator sections
• U8 removed
• R = 5,000 (FWHM)
• Aiming for R = 10,000
• Gaussian filter
• 2% efficiency
• Will implement optical
propagation that includes
relevant spatio-temporal
couplings
• Full 3D seed
• λu = 39 mm
• Lu = 3.4 (87 per.)
• Lbr = 1.0 (25 per.)
• 14 undulator sections
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SS experience with LCLS, measurement and simulation
LCLS-II Science Opportunities Workshop, February 9-13, 2015
• S2E simulations
• ASTRA/ELEGANT/GENESIS
• Phenomenological and wave
optics simulation of mono.
• Shows excellent overall
agreement both in energy and in
spectrum D. Ratner, S. Serkez
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20 pC IMPACT e-beam slice properties, HXR
LCLS-II Science Opportunities Workshop, February 9-13, 2015
s [m]
E [
GeV
]
0 10 20 30 40 50 60
3.995
4
4.005
4.01
4.015
0 10 20 30 40 50 60-10
-5
0
5
10
s [m]
- 0
0 10 20 30 40 50 600
0.1
0.2
0.3
0.4
0.5
0.6
0.7
I [k
A]
0 10 20 30 40 50 600
0.1
0.2
s [m]
e n [m
m-m
rad
]
0 10 20 30 40 50 600
0.1
0.2
0.3
0.4
0.5
0.6
0.7
I [A
]
0 10 20 30 40 50 600
1
2
s [m]
sE [
MeV
]
0 10 20 30 40 50 600
0.1
0.2
0.3
0.4
0.5
0.6
0.7
I [A
]
head I ~ 350 A
ϵn,x ~ 0.15 mm-mrad
σE ~ 450 keV
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Time-dependent S2E parameter scan (very time
consuming), HXR Eγ = 2 keV
LCLS-II Science Opportunities Workshop, February 9-13, 2015
d
1.8 2 2.2 2.4 2.6
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
Emax ~ 655 μJ
ξ = 0.03
d = 2.1
ETI ~ 470 μJ
ξ = 0.06
d = 2.15
30% difference in final energy
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Pulse length control – emittance spoiling
LCLS-II Science Opportunities Workshop, February 9-13, 2015
• Calculations indicate an emittance spoiler foil can withstand the full beam at
high rep rate
• However, the increased load on the collimators might force operation at a
low(er) rep rate
Dispersed bunch
Y
X
• Energy chirped e-beam has
x-t correlation in region of
high dispersion
• Insert foil with triangular
width to continuously tune
the pulse duration
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Emittance spoiling foil measurements at LCLS
LCLS-II Science Opportunities Workshop, February 9-13, 2015
~100 fs ~6 fs
Y. Ding
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Measured foil scan movie at LCLS
LCLS-II Science Opportunities Workshop, February 9-13, 2015
Y. Ding
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Pulse length control – differential heating
LCLS-II Science Opportunities Workshop, February 9-13, 2015
• It is fairly easy to put a notch in the laser heater profile
• Here we assume a 1 ps notch but you can get to a few 100 fs with no heroic
efforts…
unspoiled beam
@ heater spoiled beam
@ heater
A. Marinelli
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After compression and acceleration (S2E with
ELEGANT, 100 pC)
LCLS-II Science Opportunities Workshop, February 9-13, 2015
few fs lasing
core
garbage
~6 fs
FWHM
A. Marinelli
LCLS MD shifts will be dedicated to this study in the near future
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Self-seeding with a chirped e-beam for short pulses
LCLS-II Science Opportunities Workshop, February 9-13, 2015
• A chirped e-beam generates a SASE signal
• Monochromator selects a narrow bandwidth and helps to control the seed pulse
duration
• The seed is amplified only over a fraction of the bunch and dominates SASE
• Superradiance can possibly be used to further compress the pulse
SASE undulator Amplifier undulator
K0 K1
λ1 λ1
SXRSS
Y. Ding
chirp SASE BW Mono BW
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SASE undulator Amplifier undulator
K0 K1
λ1 λ1
SXRSS
LCLS example
LCLS-II Science Opportunities Workshop, February 9-13, 2015
Power profile Power spectrum
0.14eV 13 fs ~7 fs 0.3eV