LCLS-IISC Parameters
Tor Raubenheimer
Operating modes
•Two sources: high rate SCRF linac and 120 Hz NCu LCLS-I linac
•North and south undulators always operate simultaneously in any mode
Undulator SC Linac (up to 100kHz)
North
0.25-1.2 keV
South
1.0-5.0 keV
Cu Linac (up to 120Hz)
up to 18 keV
higher peak power pulses
• Concurrent operation of 1-5 keV and 5-18 keV is not possible
0.2-1.2 keV (100kHz)
4 GeV SC Linac
Cu Linac
LCLS-II Overview
1.0 - 18 keV (120 Hz)
1.0 - 5 keV (100 kHz)
2
Preliminary Operating Parameters
Preliminary LCLS-II Summary Parameters
North Side Source
v0.7
8/30/13
South Side Source
Running mode
SC Linac
SC Linac
Cu Linac
Repetition rate
up to 1 MHz*
up to 1 MHz*
120 Hz
4 GeV
4 GeV
14 GeV
0.25-1.2 keV
1-5 keV
1-20 keV
up to 2 mJ*
up to 2 mJ*
up to10 mJ
3.9x1030 **
12x1030 **
247x1030 **
3.0x1030 **
6.9x1030 **
121x1030 **
Electron Energy
Photon energy
Max Photon pulse energy
(mJ) (full charge, long pulse)
Peak Spectral Brightness
(10 fs pulse) (low charge, 10pC)
Peak Spectral Brightness
(100fs pulse) (full charge, 100pC)
* Limited by beam power on optics
**N_photons/(s*mm^2*mrad^2*0.1% bandwidth)
LCLS-II Overview
3
High Level Schedule
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More Immediate Schedule
1. Mid-October Workshop to review design, cost and
schedule with collaborators
2. Mid-December Director’s Review for CD1 Review
3. Mid-January CD1 Lehman Review
Also may need to have a FAC review prior to CD1 review
 Mid-November ??
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Assumed Beam Parameters
NLS
NGLS
LCLS-IISC
Beam energy [GeV]
2.25
2.4
4
Bunch charge [pC]
200
300
100
Emittance [mm-mrad]
0.3
0.6
0.43
Energy spread [keV]
150
150 keV
300 keV
Peak current [kA]
0.97
0.5
1
Useful bunch fraction [%]
40
50
50
The assumed emittance of 0.43 at 100 pC is roughly 25% larger than
the LCLS-II baseline. It is more conservative than the NLS or the
scaled NGLS values (the latter are consistent with the LCLS-II baseline)
however a gun has not yet been demonstrated that achieves the
desired emittances. Reduced emittances will decrease gain lengths.
Peak current is consistent with higher energy beams and BC’s
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Example of Injector: APEX
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SCRF Linac
Roughly 400 meters long including laser heater at ~100
MeV, BC1 at ~300 MeV and BC2 at 1000-2000 GeV. Long
bypass line starting at Sector 9  BSY. LTU similar to
LCLS-IISA discussed last month.
Based on 1.3 GHz TESLA
9-cell cavity with minor
mods for cw operation
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1.3 GHz 8-cavity cryomodule (CM)
• It is proposed to use an existing cryomodule design for the 4-GeV
LCLS-II SRF linac.
• CM is roughly 13 meters for 8 cavities plus a quadrupole package
• The best-fit is the EU-XFEL cryomodule
• Modifications are required for LCLS-II
• (The CEBAF 12 GeV upgrade module must also be considered)
• (The ILC CM is similar but has several important differences and is
not as well suited for CW application)
• 100 cryomodules of this design will be built and tested by the
XFEL by 2016  Global industrial support for this task
• One XFEL ~prototype CM was assembled and tested at Fermilab
• (Fermilab assembled an ILC cryomodule and has parts for another)\
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Linac
v0.9
2013-08-30
Linac parameters
1.3 GHz Mod V
50
kV
1.3 GHz Mod A
10
A
1.32E+06
W
Energy
4
GeV
1.3 GHz Sector-pair RF AC power
Cavity Gradient
16
MV/m
1.3 GHz Cryomodule spacing
13
m
3.9 GHz cryomodules
3
count
deg_K
3.9 GHz Voltage
60
MV
1E+06
Hz
3.9 GHz Cavities
12
count
Average current
0.3
mA
3.9 GHz Cavities/klystron
4
count
Beam power
1.2
MW
L0 length
8
m
Cryogenics power
3.0
MW
L1 RF length
16
m
Total SC RF AC Power
3.4
MW
LC length (3.9 GHz)
4
m
L2 RF length
96
m
L3 RF length
Total Linac length; not incl BC1 BC2
144
405
m
m
Cavity Q_0
Operational temperature
rate
2E+10
1.8
SC Layout
1.3 GHz Cryomodules
34 (+1 spare)
count
1.3 GHz Voltage
4.2
GV
1.3 GHz Cavities
264
count
1.3 GHz Rf power/cavity
7
kW
1.3 GHz Cavities/klystron
32
count
1.3 GHz SSA
24
count
1.3 GHz Cryomodules/klystron
4
count
1.3 GHz Dist. Between klystrons
57
m
3.0E+05
W
1.3 GHz Klystron avg. power
1.3 GHz Klystron (10% margin)
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No warm breaks
except BC: 1
cryo circuit per 3
kW load
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Linac View
SLAC Linac
(11 wide x 10 feet high)
(3.35 x 3.05 m)
x
11
First 800 m of SLAC linac (1964):
Cryoplant placement and construction
12
Assumed FEL Configuration
• High rep rate beam could be directed to either of two undulators
HXR or SXR bunch-by-bunch
• 120 Hz beam could be directed to the HXR at separate times
• The SC linac would be located in Sectors 0-10 and would be
transported to BSY in the 2km long Bypass Line. It would use a
dual stage bunch compressor.
• A dechirper might be used to further cancel energy spread for
greater flexibility in beam parameters
• The high rep rate beam energy would be 4 GeV and the HXR
would fill the LCLS hall with ~144 m while the SXR would be <75
m so that it could be fit into ESA
• Both undulators would need to support self-seeding as well as
other seeding upgrades
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Undulator Requirements
Requirements:
1. SXR self-seeding operation between 0.2 and 1.3 keV
in ESA tunnel (<75 meters) with 2.5 to 4 GeV beam
2. HXR self-seeding operation between 1.3 and 4 keV in
LCLS tunnel (~144 meters) with 4 GeV beam
3. HXR SASE operation up to 5 keV with 4 GeV beam
4. Primary operation of SXR and TXR at constant beam
energy  large K variation
5. HXR operation comparable to present LCLS with 2 to
15 GeV beam
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Undulator Parameters
1. To cover the range of 0.2 to 1.3 keV using SASE in less
than 50 meters (to allow for seeding)  lw ~ 40 mm
•
A conventional hybrid undulator with 40 mm and a
7.2 mm minimum gap would have Kmax ~ 6.0 which easily
covers the desired wavelength range at 4 GeV
2. To achieve 5 keV using SASE with less than 144 m
at 4 GeV  TXR lw <= 26 mm
•
•
A conventional hybrid undulator with 26 mm and a
7.2 mm minimum gap would have Kmax ~ 2.4 which
covers desired wavelength range at 4 GeV
Provides reasonable performance with LCLS beam
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Baseline Tuning Range for 4 GeV
HXR: lu = 26 mm, L = 144 m
Kmin = 0.55
SXR: lu = 41 mm, L = 75 m
SASE
Self-Seeding
Ephoton [keV]
Kmin = 0.91
Kmin = 1.6
Self-Seeding
Kmax = 2.44
Kmax = 6.0
Ebeam [GeV]
Kmin is chosen to saturate within given length for SASE or Self-seeding
Kmax is set to the maximum value for a 7.2 mm gap variable gap undulator
X-ray pulse energy at High Rate
More than enough FEL power although results assume full beam and are ~2x optimistic
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Comparison of HXR with LCLS performance at 120 Hz (1)
26 mm HXR covers 2 keV at ~4 GeV to 30+ keV at 14 GeV –
beam energy might be reduced further if desired
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Comparison of HXR with LCLS performance at 120 Hz (2)
26 mm HXR provides lower pulse energy than 30 mm LCLS but much shorter l
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Options for HXR: SCU, IV, or 30 mm period (1)
To recover the LCLS performance, we need to increase K. Can (1) increase the
period, (2) adopt an in-vacuum design, or (3) consider a planar or helical SCU.
Example of a helical SCU below
however have not included poorer SCU fill factor  results are optimistic
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Options for HXR: SCU, IV, or 30 mm period (2)
Example of a 30 mm period hybrid undulator below. Nearly recovers LCLS
performance (reduction due to slightly larger gap with VG undulator) however the
maximum photon energy at high rate, i.e., 4 GeV is now 4.3 keV not 5 keV as
with 26 mm period
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SCU options
An SCU has a number of benefits:
1. Would attain comparable performance as LCLS even
while achieving 5 keV at 4 GeV at high rate by operating
with high K
2. Would allow shorter SXR period to reduce SXR beam
energy and gain length to ensure space in ESA while still
covering full wavelength range at constant energy.
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GENESIS SIMULATION ELECTRON PARAMETERS
Centroid energy 4 GeV; 100 pC compressed to 1 kA;
normalized emittance: 0.45 mrad; slice energy spread:
sE = 300 keV except for LCLS case with 15 GeV
6 cases – details in following pages
Good
Case 1: HXR Kmin = 0.91; lw = 26 mm; Lw = 144 m (study SS 4keV)
Case 2: SXR Kmin = 1.6; lw = 41 mm; Lw = 75 m (study 1.6 keV)
Bad
Case 3: SXR Kmax = 6.0; lw = 41 mm; Lw = 75 m (study 200 eV)
Good
Barely
Case 4: SXR K = 1.9; lw = 41 mm; Lw = 75 m (study 1.3 keV)
Case 5: SXR K = 2.0; lw = 30 mm; Lw = 75 m (short gain len.)
Good
OK
Case 6: HXR in LCLS TW parameters but K too high for hybrid
undulator
J. Wu (SLAC), jhwu@slac.stanford.edu, 08/05/2013
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Potential Areas of Collaboration with Partner Labs
SLAC
LBNL
Injector
X
Undulator
X
FNAL
JLAB
X
X
SC Linac
X
X
SC cryo line
X
X
Cryo plant
X
X
X
X
X
RF systems
X
Beam Physics
X
Instruments/
Detectors
X
PM/Integration
X
Installation
X
Commissioning
X
LCLS-II Overview
Cornell
Wisconsin
X
X
X
SC linac prototype
LLRF
ANL
X
X
X
X
X
X
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Points of Contact
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CDR Writing
• Must keep the document concise – it is a conceptual design
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
Executive Summary (Galayda)
Scientific Objectives (TBD)
Machine Performance and Parameters (Raubenheimer)
Project Overview (Galayda)
Electron Injector (Schmerge)
Superconducting Linac Technologies (Ross,Corlett)
Electron Bunch Compression and Transport (Raubenheimer, Emma)
FEL Systems (Nuhn)
Electron Beam Diagnostics (Frisch, Smith)
Start-to-End Tracking Simulations (Emma)
Photon Transport and Diagnostics (Rowen)
Experimental End-Stations (Schlotter)
Timing and Synchronization (Frisch)
Controls and Machine Protection (Shoaee, Welch)
Conventional Facilities (Law)
Environment, Safety and Health (Healy)
Radiological Issues (Rokni)
Future Upgrade Options (Galayda)
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