1. LCLS Linac Overview E. Bong Lehman Review August 10, 2004

2. Technical Scope and Status
LCLS Linac Overview
Technical Scope and Status
Linac Functional Areas
Long Lead Procurement Items
Schedule and Organization
Linac Challenges

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
Two Beam e- e+ Running

6. L1 & BC1 Subsystem L1 Requirements PRD# 1.3-002
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 4 S-Band Structures
Electrons
L1 Requirements PRD#
BC1 Requirements PRD#
Installation ’06 shutdown

7. X-Band System Design
X-Band located in L1 just up-stream of BC1 bunch compressor
Linearizes energy gradient prior to bunch compression to minimize CSR instability
1 x XL-4 klystron feeding 1 X-Band accelerating structure obtained from NLC
Long Lead Procurement Item
Installation Summer ’06 and ’06 shutdown
Requirements – PRD#
Parameter
LCLS
(Nom)
NLCTA
Units
Structure Length 60 cm
Structure Voltage 19 30 MV
Phase
-160 -
deg
Klystron Power 21 50 MW
Repetition Rate
120 Hz
Pulse width
0.1
1.6 ms

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 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#

10. 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#

11. 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#

12. 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#

13. LCLS Linac LTU Subsystem Schematic
3-D solid automated layout generated from MAD also done

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

15. LCLS Linac E-Dump Subsystem
New Beamline located between exit of Undulator and Near Experimental Hall in new underground housing.
Separates electron beam from X-Ray FEL beam directs beam to dump.
Includes energy and energy spread measurement capability to 10-4
Requirements PRD#

16. Safety Dump Concept
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
Specification ESD#

17. LCLS Linac Challenges
RF Stability (RF/Timing Design, R. Akre; Linac Long-lead Procurement P. McIntosh)
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 (E-Beam Diagnostics , P. Krejcik)
Bunch length measurement in R&D at SPPS
Epics/SLAC Controls System Compatibility (Controls System breakouts)
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 (Physics Requirements for Linac, P. Emma)
Articulation required for R56 tuning for full range of beam charge
Simplification of LEUTL design to reduce design challenge
BPM Module Design (Controls System Breakouts)
Measurement of full range of beam charge required
Two beam e+ e- beam operations place additional challenge on module design

18. 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

19. Budgeted Cost of Work Scheduled (BCWS)
FY04 to FY05 increase in funding - X-Band System LLP
FY05 to FY06 increase in funding – Construction

20. 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

21. Linac System Progress Summary
SC Wiggler removed from Linac baseline
Conducted Linac Technical Design Review
Linac status to Facility Advisory Committee
Linac baseline presented to EIR
Linac area schematics complete
L1, BC1 and X-Band modeling underway
Conducted L1 & BC1 preliminary design review
E-Dump & Safety Dump design ready for Radiations Safety Committee review
Jitter model developed and feedback simulations conducted, presented at XFEL conference J. Wu

22. Work Plan Next 6 Months
Matrix in Klystron Dept. engineering and design support for X-Band 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

23. LCLS Linac System Conclusions
L1 and BC1 design progress on schedule
Linac system baseline established
X-Band system & BC Magnets ready for FY05 LLP funding
RF stability achievable with feedback
Bunch length measurement R&D in progress

24. End

25. BC 1 X-Band Compressor