Injector Physics C'LimborgDeprey

1
Injector PhysicsC.Limborg-Deprey

• GTL final design
• Wakefield budget
• Final Modifications
• Commissioning Readiness
• Schedule
• Feedback systems
• An example of tuning procedure
• Steering in L0a

2
Injector
?Gun installation Nov. 2006 ? Gun Region
July 2006 ? Accel Region June
2006 ? Heater Region June 2006 ? Wall
Region October 2005 ? Waveguide
October 2005 ? Injection Region Aug-Nov
2006 ? Spect Region Aug-Nov 2006

• Injector Commissioning Start December 2006

3
Gun to Linac Region
4
GTL Design

• Normal incidence
• Mirror size (14mm x 10 mm)
• No second Valve in GTL
• All wakefield computed
• (see next slides)
• Diagnostics units finalized
• accommodate 20 mm screens
• wakefield mitigation
• Gun Solenoid moved as close as possible to
  cathode
• Bucking Coil added (PRD written)
• cancels the 55 Gauss Bz field on cathode
• Compatibility with gun bake cathode removal

5
GTL Design

• Pending issues
• lt1.05 permeability of VV01
• Impact on Bsolenoid falling edge to be measured
• Choice of material for injector mirror
• Optical path for CRG1 light
• Finalization of GTL BPMs to meet 20 ?m resolution
• Alignment laser specifications
• Final GTL design review next week

Courtesy J.Langton
6
Wakefield Budget

• ??projected lt1.2 mm-mrad
• with no error simulations show 1.0 mm-mrad
• Stability of electro- magnetic components to meet
  less than 10 increase
• lt10 increased from total wakefield effects over
  the whole beamline
• GTL area is critical region

Injection mirror with 1mm beam offset
7
Wakefield from Injection Mirror
MAFIA Simulations, Courtesy Cho-Kuen Ng
L
(2)
(3)
(1)
d
8
Wakefield Mitigation in GTL

• Pumping slots
• 0.24 V/pC/m per unit
• 3 units at 0.6 m
• 3 units at 1.2 m
• Negligible emittance growth
• Combined Diagnostics chambers
• Wakefield Mitigated
• small gaps

Pumping slot
Courtesy J.Langton
Courtesy Cho-Kuen Ng
9
Wakefield Mitigation in GTL
Bellows

• Bellows
• Sleeve on each 7
• Small step transition
• instead of 25V/pC/m

Sleeve

• Spectrometer bend chamber
• Wakefield mitigation movable plug
• Eliminates any wakefield
• Small gap

Straight beam

• Gaps
• 1mm gap 3V/pC/m

Beam to Spectrometer
Plug out
Courtesy J.Langton
10
Wakefield in Radiation Stopper

• Radiation Stopper not an issue
• LCLS-TN-05-15
• "Wakefield Calculations for Radiation Stopper
  1  (RST1)
• Wrms lt 0.077V/pC on axis
• ??/? lt 0.1
• due to small ?? 1.5 m

MAFIA computations Courtesy Cho-Kuen Ng
11
Final changes in Accelerator Region
Courtesy P.Stephens
12
Beamline Modifications

• L0a moved downstream by 8 cm
• Ok with emittance compensation
• Solenoid 2 reduced to 20 cm effective length
  magnet (Req. sent out)
• higher Bfield for same focal length
• higher Bfield is not an issue
• Suppressed one out of 2 BPMs in L0a-L0b drift
• 4 inch Phase monitor fits in
• Valve moved from L0a entrance to L0a-L0b drift
• Mu-shield metal wrapped around all possible
  location
• PRD 1.1-009
• Unfortunately not possible in GTL

13
Diagnostics

• Critical decisions
• Specifications for screens and resolution
  finalized (PRD out)
• CR material 1mm thick, quartz, to be replaced
  with aerogel later
• OTR cameras orientation to increase depth of
  field
• Streak camera ordered
• Choice of CCD cameras finalized
• Remaining issues
• Optical path for CRG1 light
• 2nd pick-up on toroid for BCS
• Alignment laser spec. to be finalized
• Finalization (Resolution) of BPM design for large
  aperture pipe

14
Commissioning Schedule

• Discussed every 5th week with LCLS
  physicists/operators group
• To be incorporated into large .mpp document for
  links
• Discussed weekly inside Injector group
• (Bong, Dowell, Limborg, Loos, Schmerge )
• Based on 2 shifts per day
• Resource loading to be refined
• 2 physicists per shift 1 control person 1
  operator
• guests
• Meeting will evolve in high level application
  discussion
• Schedule Outline
• Starts with RF Gun cold and hot test (summer 06)
• First beam at 135MeV dump (Nov.22-06 ?? Dec.06)
• 8 months of characterization and optimization
• Deliver most stable beam for acceptable charge
  for BC1 commissioning at end of June07

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Schedule
December 06 ?
16
Commissioning Readiness

• Pending issues
• Hot test schedule
• Finalize start date, detailed schedule
• Feedback Systems
• Calibrations procedure
• Magnetic calibration procedure drafted
• Screen calibration procedure
• High Level Applications

17
High Level Applications

• Cathode characterization (QE, uniformity, Thermal
  emittance)
• Steering in L0a
• Longitudinal phase space measurements at BXG
• Bunch length measurement with transverse RF
  deflector(s)
• Emittance meas. (multi-wire, multi-OTR,
  quad-scan, slice)
• Power-steering through beamlines, with corrector
  weights
• Difference orbit fitting, including internal kick
• Longitudinal phase space measurement at BXS
• Tomography (Longitudinal and Transverse)

18
Feedback Systems

• Pointing Stability (see Laser)
• Tolerance
• Slow (flt1Hz) lt200 ??m (or slice emittance
  degraded)
• Fast (1Hzltflt120 Hz) lt10 ??m (1 of 10
  ?x,undulator budget)
• Slow feedback Sensor/ actuator
• Virtual cathode / mirrors
• Status preliminary tests at bldg 407
• Fast stability
• Design constraint (Gun injection mirror
  vacuum chamber rigidly linked to optical launch
  table ,i.e. less than 10??m fast motion )
• Charge Stability (see Laser)
• Tolerance
• Fast (shot-to shot) lt 2rms
• Sensor/Actuator
• first toroid IM01/ polarizer

19
Feedback Systems

• Timing Stability
• Tolerance
• Fast stability (120Hz),
• laser phase w.r.t master clock lt 0.5 ps rms
• feedback system
• sensor phase monitor signal
• actuator locking electronics from Thales system
• Slow stability (lt1Hz),
• laser phase w.r.t gun phase lt /-3 ps
• to maintain emittance within 5 of optimal

20
Steering in L0a

• Solenoid mispositioning
• 250 ??m, 250 ?rad
• Earth Magnetic field 2mrad/m vert.
• No space for mu-metal shielding in GTL
• By 0.35 G
• Bx 0.12 G
• Offset as large as 3mm without steering

Solenoid
SC0
SC1
SC2
BPM2
BPM3
BPM5
Gun
L0a
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Simulations of steering

• Procedure
• L0a solenoid off
• Orthogonal knobs at SC0
• SC0 and SC1 adjusted to steer in L0a
• Scaling of SC0 orthogonal knobs with solenoid to
  be implemented in software when

Solenoid
SC0
SC1
SC2
BPM2
BPM3
BPM5
Gun
L0a
22
Conclusions

• GTL Design finalized
• L0a-L0b space issue solved
• Laser Heater region to be detailed
• Commissioning schedule under completion
• Feedback systems under completion
• High Level Applications to be written

23
Response to the April FAC Recommendations

• Wakefield in Gun
• Large Energy spread in gun identified to be
  related to 0-mode
• ACD group will perform more simulations
• 3D-ellipsoidal laser pulses
• Presented at major conferences, in particular at
  FEL05 with good interest shown from many laser
  experts

24
BACK-UP
25
Hot test schedule

• Objectives
• Task1 RF Conditioning
• Task2 Verification of thermal design (?f vs
  Power, ?f vs T)
• Task3 Close LLRF feedback loop
• LLRF feedback loop can only be closed if
  availability of
• Chiller, Instrumentation of detection of phase
  from reflected power signal, Drive Amplifier
• Four scenarios discussed

() Special PPS run klystron e beam to
spectrometer during linac downtime