1. LCLS Gun Commissioning Status & Plans David H
LCLS Gun Commissioning Status & Plans David H. Dowell LCLS Injector Commissioning Workshop October 9, 2006
Status of gun fabrication and testing
Gun test results
Characterization of magnetic components
Systems to be commissioned
The 3-Pass Commissioning Plan
Summary

2. Gun Fabrication and Testing Process
Fabricate parts
Cold test sub assemblies and clamped parts
Machine and measure for resonance and field balance
Braze and weld final assembly
Low power RF and cathode tests
Furnace bake at 500deg C
Assemble and configure for high power RF test (hot test)
Vacuum bake of assembly in Klystron test vault
Perform hot test
Vacuum qualification of gun
Alignment of assembly with CMM
Install at S20

3. Gun only pictures CAD cut away view of gun interior
RF Gun Fabrication and Cold RF Testing Finished & Preparing for High-Power Tests
Gun only pictures
CAD cut
away view
of gun interior

4. RF Field Balance Measured Using Bead Drop Technique
Data compliments J. Wang, ATR Dept., SLAC

5. Gun Design and Measured Specifications
RF Parameters
Design
Measured
fp (GHz) Q0
13960
14062 β
2.1
2.03
Mode Sep. f (MHz) 15
15.17
Field Balance 1

6. LCLS RF Gun: Beam Side
dual rf power feeds
focusing solenoid
beam port:
Attach 2-km
linac here

7. cathode flange
dual rf power feed
focusing solenoid
LCLS RF Gun: Cathode Side

8. Description of gun magnet system
Gun solenoid: SOL1
Bucking coil: SOL1BK
X,Y dipole correctors:
XC00&YC00 (inside SOL1)
Normal & skewed quad correctors: CQ01&SQ01 (inside SOL1)
Field maps and calibrations measured

9. Gun Solenoid and Dipole Corrector Magnetic Measurements

10. Bucking Coil Magnetic Measurements

11. What we’re commissioning
e- to L0A
Q = 1 nC
f = 120 Hz
G = 120 MV/m
gex,y = 1 mm
Dt = 10 ps
I = 100 A
E = 6 MeV
spec. dipole
UV laser e-
solenoid
YAG screens
RF gun
cathode

12. The Gun & Gun-to-Linac Region with the Drive Laser Launch Optics
Laser tube from laser room

13. CAD Model of the Drive Laser Launch Optics
(top view) BS
Wave plate
Lead block
Shutter
Table is fully enclosed VC
Power Meter
Cathode
CAD model of the
laser launch optics
(top view)

14. Schematic of Drive Laser Launch Optics
Laser beam from drive laser
Virtual in-vacuum mirror camera
Virtual cathode camera
lens M2 M1
Polarizer
Virtual image of
in-vacuum mirror
mirrors used to
steer laser on cathode
Wave plate
BS2
BS: beam splitter
BS1
Joule meter
shutter (BCS), rate control
To the Gun window and in-vacuum mirror

15. Gun and Gun-to-Linac Components
SOL1
Bucking Coil
SOL1BK
Drive laser injection cross
On-axis alignment laser
Drive laser
Alignment laser
YAG01/FC01
BXG
Spectrometer
YAG02
Quads
YAGG1/FCG1
BPMs
IM01
Current Toroid

16. Injector Commissioning Philosophy
Commissioning plan is organized into three passes through the injector
Tasks 2.3.3: 1st pass
Pre-beam and beam-based hardware & software checkout
Tasks 2.3.4: 2nd pass
First-order optics
Tasks 2.3.5: 3rd pass
Full beam characterization and optimization
In each pass the beam is transported from the gun through DL1 and BC1 stopping at the beam dump, TD-11.

17. The Injector Commissioning Schedule and the 3-Pass Plan
Jan 1
2007
March 1
Approximation of real schedule!

18. Pass 1 Pre-Beam Commissioning RF Processing and Water & RF Controls
Characterize and test gun water system controls
Water system only, no RF
Control loop bandwidth
Temp stability
RF processing with resonance control (water & LLRF)
Test of LLRF phase/amplitude controls (4-gun probes) (0.1deg s-band, 0.1%)
Measure recovery time after trip
Interaction between LLRF & water controls

19. Setting RF & Centering Laser in SOL1.
Pass 1 Commissioning
Setting RF & Centering Laser in SOL1.
Then continue transport thru L0a, L0b ending at BXS to set the injector beam energy
Use fast diode at gun to time laser in rf envelope
Set launch phase within rf period
SOL1 at nominal field, scan laser phase until beam observed on YAG01
Meas. base width of charge vs. laser phase (is it correct?, i.e. ~110deg)
Locate zero crossing & set laser phase to 30deg
Center laser beam on SOL1
Vary SOL1 current & move laser on cathode until there is no motion on YAG01
Observe beam on YAG02, vary SOL1 current & move laser until there is no motion
Record settings on virtual cathode, virtual mirror, etc.

20. Overview of Second Pass Gun/GTL Commissioning
Pass 2 Commissioning
Overview of Second Pass Gun/GTL Commissioning

21. Calibration of charge and energy diagnostics
Pass 2 Commissioning
Second Pass Commissioning Details of Gun/GTL Optimization, 1st of 3 parts
Calibration of charge and energy diagnostics
Alignment procedure for energy measurements
Measurements of gun beam energy

22. Schottky scan to determine QE and presence of satellite laser pulses
Pass 2 Commissioning
Second Pass Commissioning Details of Gun/GTL Optimization, 2nd of 5 parts
Schottky scan to determine QE and presence of satellite laser pulses
Charge vs. laser energy to measure QE and linearity (no space charge limit of emission)
QE uniformity measurement by rastering laser beam

23. Thermal emittance by solenoid scan at different gun fields
Pass 2 Commissioning
Second Pass Commissioning Details of Gun/GTL Optimization, 3rd of 5 parts
Determination of emission uniformity by imaging cathode onto YAG01 and YAG02
Thermal emittance by solenoid scan at different gun fields
Divergence of beam at cathode by parallel-to-point imaging at YAG02
Confirm parallel-to-point optics by varying laser radius
Repeat at different gun fields

24. Beam alignment and calibration checks of BXG and quads
Pass 2 Commissioning
Second Pass Commissioning Details of Gun/GTL Optimization, 4th of 5 parts
Beam alignment and calibration checks of BXG and quads
Gun beam energy and energy spread vs. laser phase
Low charge, short bunch
Low charge, 10ps bunch
High charge, 10ps bunch

25. Beam-based feedback systems tested and enabled
Pass 2 Commissioning
Second Pass Commissioning Details of Gun/GTL Optimization, 5th of 5 parts
Beam-based feedback systems tested and enabled
First emittance and bunch length measurements

26. Third Pass Commissioning Details of Gun/GTL Optimization
Integrated operation with entire injector
Projected and slice emittance optimization (Gun solenoid & laser shape)
Longitudinal phase space measurements

27. Summary of Gun Commissioning Status & Plans
Gun fabrication and cold testing completed
Gun meets all design goals
All magnetic components calibrated and characterized
Gun integrated with solenoid and waveguide assembly
Installed in test vault at Klystron
First bake of assembly (gun vacuum in high Torr)
High-power RF (hot) testing has begun
Final vacuum qualification & alignment performed after Hot-Testing
Gun on schedule for Dec’06 installation
Commissioning will be done in three passes
Pass 1: Pre-beam checkout and beam-based checkout
First transport beam through entire injector & BC1 to TD-11
Pass 2: First-order optics
Characterize components and beam throughout injector
Pass 3: Full beam Characterization
Optimize beam quality