1. LCLS Injector/Diagnostics David H. Dowell, SLAC April 24, 2002
Overview of the LCLS Injector Preliminary Design
Description of Major Components
Summary
LCLS DOE Review, April 24, 2002
David H. Dowell, SLAC

2. LCLS DOE Review, April 24, 2002
David H. Dowell, SLAC

3. Injector Layout at Sector 20
Layout Designed Using PARMELA and Elegant
Injector Consists of Four Regions:
Gun-to-Linac
L0 Linacs
Matching Section
Straight Ahead Tune Up Dump
LCLS DOE Review, April 24, 2002
David H. Dowell, SLAC

4. GTF Gun is Basis for 120 Hz Design
120 Hz Gun Design Includes:
RF Probes on both cells
Additional cooling
RF power feed forward
Remote control of cell tuners
and cathode plate to compensate for
thermo-mechanical detuning
Cathode Load Lock
J. Weaver/J. Schmerge/
M. Hernandez/D. Reis, SLAC
SLAC/BNL/UCLA Collaboration
LCLS DOE Review, April 24, 2002
David H. Dowell, SLAC

5. SLAC/BNL/UCLA Collaboration
Thermal Distortions for GTF Gun at 120 Hz, 3 kW
Radial
Distortion
(mil)
0.9
1.2
1.6
1.9
2.3
2.7
1.8 mil
~3.6 MHz
Axial Distortion
(mil)
1.0
1.7
2.3
3.0
3.6
4.3
1.9 mil
~380 KHz
2.3 mil
~920 KHz
Thermal Distribution
(degrees F)
~170 deg F
~132 deg F
~122 deg F
Optimizing cooling channels, work in progress
Highest temperatures on flexible cathode plate
Preferentially bakes cathode during operation,
cleaning it relative to rest of cavity => Higher QE
SLAC/BNL/UCLA Collaboration
LCLS DOE Review, April 24, 2002
David H. Dowell, SLAC

6. Overpowering Gun Reduces Dissipated Power
Cavity Voltage vs Time 8 P
= MW P
= MW
klystron 30 14
klystron P
= kW
ave
1.23
3.80 P
= kW
ave 7 E
= MV/m
cathode 6 5
V (MV) 4 3 2 1
0.5 1
1.5 2
2.5 3
3.5 4
4.5 5
Time ( m s)
J. Schmerge, SLAC
LCLS DOE Review, April 24, 2002
David H. Dowell, SLAC

7. Fast RF Amplitude and Phase Control for 120 Hz Gun
By rotating (changing the phase of) two vectors in equal
but opposite directions and then combining,
the output amplitude can be changed without changing phase.
R. Akre, SLAC
LCLS DOE Review, April 24, 2002
David H. Dowell, SLAC

8. Preliminary Design for Cathode Load Lock
Load Lock allows efficient cathode replacement
Maintains clean cathode during in-vacuum transfer
Allows use of reactive cathodes
Eliminates need to bake gun after cathode change
Allows gun baking w/o cathode plate
Better pumping during bake
Cleaner gun => Higher RF field (140MV/m)
RF Gun
Kirby/Collet, SLAC
LCLS DOE Review, April 24, 2002
David H. Dowell, SLAC

9. Diagnostic Locations Measures Determines
Gun Spectrometer
Gun to Linac
Energy
Energy Spread
E: Gun field
DE: Gun balance
Electro-Optic
Matching Section
Electron Bunch Shape
Beam Timing
SC & RF bunch shape effects
E-beam:Laser:RF timing
Charge Toroids
Everywhere
Bunch Charge
Transport
Beam Position Monitors
Non-Intercepting Position
Alignment
Correlated jitter
OTR & YAG Profile Monitors
Position
Beam Shape
Emittance: projected,slice
Energy, long phase space
Transverse RF Cavity
Induces Time-Dependent Kick
Longitudinal phase space
Slice emittance
Wire Scanners
‘Non-intercepting’
RF Cavity Phase Detector
Bunch Shape
Faraday Cups
Straight Ahead Dump
Charge
Absolute measurement
LCLS DOE Review, April 24, 2002
David H. Dowell, SLAC

10. RF Gun to L0-1 Accelerator Region
Laser Penetration
Alignment Laser
On-Axis
Laser Table
Load lock not shown M P E B 1 V L
RF Gun E A V E 1
Linac Solenoid
Gun Solenoid V L M A C V Y 1 - C X F 1
Legend C S
CM: Charge Monitor
SC: Steering Corrector
FC: Faraday Cup
BPM: Beam Position Monitor
EO: Electro-Optic
Gun Spectrometer
LCLS DOE Review, April 24, 2002
David H. Dowell, SLAC

11. Matching Section and Straight Ahead Diagnostics
CM3/BPM4/OTR2
EO2: Bunch Shape
L0-2
Legend
Section
Electro-Optic Diagnostic
BPM, Beam Position Monitor
Non-Intercepting
CM, Current Monitor
Projected Emittance Measurement
OTR, Optical Transition Radiation Screen
OTR3,BPM6
Intercepting & "Non-Intercepting"
EO, Electro-Optic
Longitudinal Phase Space
Wire
Quadrupole, typ.
Slice Emittance
Scanners
Wire Scanner ("Non-Intercepting")
OTR (Intercepting)
Scale:
Transverse
RF Cavity
5.00m.
BPM9
OTR6
BPM7/OTR7
Optical Transition
BPM10
EO3
Radiation Screen
Main Linac Center Line
Beam
Stopper
BPM11/OTR9
OTR10/BPM12/CM6
Tune-up Dump/
Faraday Cup
Straight Ahead
OTR11/BPM13
Spectrometer
Longitudinal Phase Space
Slice Emittance
Beam Energy
Beam Charge
LCLS DOE Review, April 24, 2002
David H. Dowell, SLAC

12. LCLS Injector/Diagnostics Summary
Completed Preliminary Injector Design
Injector designed with PARMELA and Elegant
120 Hz Gun
Further work on gun cooling needed
RF heating of cathode may improve QE, lifetime
Fast RF control reduces dissipated power factor of 3
RF probes and dynamic tuners in both cells
Load Lock
Provides fast cathode replacement, no gun baking
Allows use of reactive cathodes
Improves vacuum and HV operation (140MV/m)
Diagnostics Integrated into Injector Design
LCLS DOE Review, April 24, 2002
David H. Dowell, SLAC