1. LCLS Linac Update E. Bong Facility Advisory Committee Meeting October 12, 2004

2. LCLS Linac Update
Brief Overview
L1 & BC1 Progress
LTU & E-Dump Status
Continuing Resolution Impact

3. Nominal LCLS Linac Parameters for 1.5-Å FEL
Single bunch, 1-nC charge, 1.2-mm slice emittance, 120-Hz repetition rate…
135 MeV
z  0.83 mm
  0.10 %
250 MeV
z  0.19 mm
  1.6 %
14.1 GeV
z  mm
  0.01 %
Linac-X
L =0.6 m
rf= -160
4.54 GeV
z  mm
  0.71 %
E-Dump
LCLS INJ
Linac-1
L 9 m
rf  -25°
Linac-2
L 330 m
rf  -41°
Linac-3
L 550 m
rf  -10°
21-1b
21-1d X
21-3b
24-6d
25-1a
30-8c
undulator
L =130 m
SLAC linac
BC-1
L 6 m
R56 -39 mm
BC-2
L 22 m
R56 -25 mm
DL-1
L 12 m
R56 0
LTU
L =275 m
R56  0
SLAC linac tunnel
research yard
(RF phase: frf = 0 is at accelerating crest)

4. Baseline System Design
1.5-Å SASE FEL Linac:
Requirements
Acceleration to 14.3 GeV (4.5 GeV min.)
Bunch compression to 3.4 kA (gex,y  1.2 mm)
Emittance preservation (<20% ‘slice’, <100% ‘projected’)
Final energy spread (<0.02% ‘slice’, <0.1% ‘projected’)
Minimal sensitivity to system ‘jitter’
Diagnostics integrated into design
Flexible operations (1.5 to 15 Å, low-charge, chirp, etc.)
Compatibility with other SLAC programs
use 2 compressors, 3 linacs
Linac Physics Requirement Document PRD#

5. LCLS/SLAC Program Compatibility
Program Changeover Time
15 minutes from LCLS to damped SLAC beam
24 hours from LCLS to undamped ESA beam
Moving Chicanes
Articulates collinear with linac axis for straight-ahead
X-Band Structure Aperture
7mm, smaller than linac scrapers (16.5mm)
Smaller than undamped beam
Moves off-axis, temporary pipe installed
BPM Module Design
Charge Range. LCLS 0.2nC to 1nC. Full ESA beam

6. L1 & BC1 Subsystem System background 3-D complete
Linac 1 (L1)
Bunch Compressor 1 (BC1)
Treaty Point LCLS Injector/LCLS Linac
Two short accelerator structures, refurbished Quads+BPMs,X&YCOR
X-Band Structure (NLC)
Quad + BPM, YCOR,XCOR, QE, Toroid
Bunch Compressor & Diagnostics
Emittance Diagnostics.
LCLS Injector
LCLS Linac
Remove 5 S-Band Structures
Electrons
System background 3-D complete
X-Band structure and waveguide network design in progress
BC1 chicane articulation design in progress
Dimensional checks between mechanical layout and physics deck performed
Work remaining: short accelerators, emittance diagnostics section

7. X-Band System Design 60cm structure from Fermi
Integrated into beamline layout
Translation to be designed
XL4 Klystron
NLC waveguide components designed for 8-Pack

8. BC1 System Design Status
Articulated bunch compressor layout
Dynamic solid modeling
Bend Magnets LLP
Install FY ’06 shutdown
BC1 inter-bend diagnostics package
BPM, collimator, OTR

9. LCLS Linac L2, BC2, L3
Except for BC2 in Linac Sector 24, Linac Sectors largely unmodified
System schematics complete
3-D models of area backgrounds near complete
File management structure for 3-D models complete

10. LCLS Linac LTU Subsystem Schematic
Energy and emittance diagnostics, energy collimation, bunch length diagnostics and undulator launch feedback
3-D solid automated layout generated from MAD done

11. Multiple Undulator Expansion Capability
LTU
Multiple beamlines NOT in LCLS baseline scope
Baseline design not to exclude possibility of expansion

12. Main Dump and Safety Dump
Main dump electromagnets allow energy and energy spread measurements
Safety dump permanent magnets deflect e-beam on BYD failure
Ray traces show no beam transported through wall in any failure condition
Working with SLAC Radiation Safety for approval of design

13. LCLS Linac Work Plan by Area Design, Long Lead Procurement, Construction, Installation, FEL Commissioning
LLP X-Band
LLP BC1 BC2 Bends
L1, BC1, L2, BC2 and L3 must be installed during SLAC Linac downtimes.
SLAC Linac Downtimes

14. LCLS Linac Organizational Chart
Resources obtained through both direct hire and matrixed from SLAC departments
Resources within groups distributed based on project demands
Communication between systems managed through Interface Control Documents

15. LCLS Linac Challenges RF Stability Bunch Length Measurement & Feedback
Existing system phase and amplitude stable to requirements over several seconds
Stability achievable over longer time scales using bunch length and energy feedback
Bunch Length Measurement & Feedback
Bunch length measurement in R&D at SPPS
Feedback modeling and simulation by J. Wu
Epics/SLAC Controls System Compatibility
Require Epics system to access SLC control system in order to operate existing equipment required for LCLS
SLC control system needs to access EPICS system to operate LCLS upgraded equipment required in high power beam operations
Articulated Bunch Compressors
Articulation required for R56 tuning for full range of beam charge
Move for Accelerator centerline for un-damped beam operation
BPM Module Design
Measurement of full range of beam charge required
Two beam e+ e- beam operations place additional challenge on module design

16. Work Plan Next 6 Months
Matrix in Klystron Dept. engineering and design support for X-Band modulator and LLRF design
Begin procurement of X-Band system
Begin procurement of BC1 & BC2 dipoles
Complete L1 & BC1 design & details
Complete BC1 diagnostics design & details
Begin L2 & L3 system design
Obtain Radiation Physics approval of safety dump design
Continue jitter and feedback modeling
Develop commissioning plans
Develop detailed installation plan
Integrate Injector and Linac engineering groups

17. Linac System Progress Summary
Linac baseline presented to EIR
Linac area schematics complete
Linac Li D backgrounds in process
L1, BC1 and X-Band modeling underway
Conducted L1 & BC1 preliminary design review
E-Dump & Safety Dump design under radiation safety review
Jitter model developed and feedback simulations conducted, presented at XFEL conference J. Wu

18. Continuing Resolution Impact
Procurement of long lead items delayed
Ramp-up of engineering effort delayed
In most cases delays decrease schedule float
X-Band Klystron will not be ready for FY’06 downtime

19. End

20. BC 1 X-Band Compressor

21. LCLS Linac L2 Subsystem
Linac Sector 21-3b to 24-6d. Largely unmodified SLAC Linac.
Energy chirps the bunch to allow compression in BC2
RF stability critical
Four wire scanners added for emittance measurement
Requirements PRD#

22. LCLS Linac BC2 Subsystem
Linac Sector 24-7a to 24-8d, Remove eight S-Band structures
compress a single 1-nC, 195-mm long (rms) electron bunch, at a repetition rate of 120 Hz, at 4.54 GeV to an rms length of 22 mm
BC2 Bends, Long Lead Procurement Item
Requirements – PRD#

23. LCLS Linac L3 Subsystem Linac Sector 25 to 30 largely unmodified.
Two accelerator structures added, two structures moved, two wire scanners moved, transverse cavity moved, new OTR screen.
Requirements PRD#

24. LCLS Linac LTU Subsystem
New Beamline extending from FFTB muon plug wall in SLAC BSY, across research yard in new housing to FEL undulator
Transports a 1-nC, 20-mm long (rms) electron bunch, at a repetition rate of 120 Hz, at 14 GeV to the LCLS FEL undulator
Includes energy and emittance diagnostics, energy collimation, bunch length diagnostics and undulator launch feedback
Requirements PRD#

25. LCLS Longitudinal Feedback Simulation
feedback off
feedback on (Integral gain:0.5)
Juhao Wu (SLAC)