Injector Commissioning Plans C.Limborg-Deprey

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Injector Commissioning PlansC.Limborg-Deprey

• Parameters
• nominal tuning 1nC
• 0.2nC
• Diagnostics
• Start-Up and Alignment
• Calibrations Critical Measurements
• Gun Spectrometer
• 135MeV Emittance, Spectrometers
• Key Softwares
• Data Analysis Softwares
• On-Line Modeling Tools

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Preinjector
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Injector-Linac Installation

• Laser System June 2006
• Gun Region April 2006
• Accel Region March 2006
• Heater Region January 2006
• Wall Region October 2005
• Injection Region August 2006
• Spect Region August 2006

Commissioning starts Jan07 ? August07
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Alcove feet underground
Sector 20 Alcove
Laser Bay
Drive Laser
Drive Laser System
Transport Tubes
Transport Tube
Laser Heater
RF Gun
UV Launch and Condition.
Photocathode Gun Launch System
Laser Heater
Electron Diagnostic
Courtesy J.Mitchell
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Parameters
Name Q (nC) Laser Pulse r (mm) ??th (mm.rad) ?100 / ?80 (mm.rad)
1nC 1 10ps 1.2 0.72 1.0
0.2nC 0.2 6ps 0.42 0.25 0.37

• ? Critical parameters assessed at GTF
• ?thermal 0.6 mm.mrad per mm laser spot size
  measured for S-Band copper cathode
• (discrepancy to theoretical thermal value is
  under investigation)
• E peak 120MV/m
• QE 3.10-5
• Alternate tuning 0.2 nC
• Performances demonstrated at GTF (?slice
  1mm.mrad without laser shaping)
• With laser pulse shaped, much better performances
  expected
• Tuning easier for whole LCLS (reduced wakefields
  )

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6 MeV ?? 1.6 ??m ??,un. 3keV
63 MeV ?? 1.08 ??m ??,un. 3keV
135 MeV ?? 1.07 ??m ??,un. 3keV
135 MeV ?? 1.07 ??m ??,un. 40keV
Linac tunnel
Laser Heater
DL1
Gun
S1
S2
L0-1 19.8MV/m
L0-2 24 MV/m
Spectrometer
3 screen emittance measurement
RF Deflecting cavity TCAV1
Spectrometer
UV Laser 200 ??J, ?? 255 nm, 5-20 ps, r 0-1.5
mm
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Diagnostics
YAGs
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Start-Up

• Laser Commissioning
• Deliver laser to linac vault
• Steer beam through transport tubes and set up
  alignment fiducials
• Set up laser BPM and measure laser beam spatial
  jitter
• Test laser energy diagnostic and vary laser
  energy from 1-100 mJ at cathode
• Test laser timing diagnostic (ns diode or
  comparable detector)
• Set up and test the laser virtual cathode
• Measure laser pulse length with streak camera
• Measure at cathode position without cathode.
• Test ability to adjust pulse length from 2-10 ps
• Vary laser beam diameter at cathode from 100
  microns to 2 mm.
• Gun Commissioning
• RF processing
• Measure following parameters as a function of rf
  field (power) at 10 Hz stop when the field on
  axis as measured with the field probes is 130
  MV/m.
• Gun Probe amplitude signals
• Gun forward power signals
• Gun Probe phase signals
• Dark current
• Vacuum levels

Steering Stability Shape Temporal Transverse
RF Processing
Laser Timing
Courtesy J.Schmerge
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BBA

• BBA of solenoid
• align centers of
• laser beam Gun solenoid linac
• Steerers in solenoid SC1 (0.8m)SC2(1.5m)
• Do we need remote control ?
• still under discussion in our group
• hope to get information from M.Krasilnikov
  presentation
• BBA
• BPMs offsets (Quad Shunt)

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Including Magnets
Treaty Point
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Linac tunnel
Laser Heater
Straight Ahead Spectrometer
3 screen emittance measurement
RF Deflecting cavity TCAV1
Emission ??thermal Uniformity QE
Gun Spectrometer
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Thermal emittance Uniformity Emission Spot
YAG1
YAG2
CR1
Energy Energy Spread Temporal uniformity
Time-Space correlation Slice thermal emittance
YAGG1
?rf Vrf Bsolenoid
CRG1
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Emission

• QE
• Cathode imaging
• Point-to-Point Imaging
• Transverse uniformity of emission disk
• Ellipticity Slope of Edges
• Thermal emittance measurement
• Infinite-to-Point imaging
• Divergence at cathode
• Model thermal emittance
• Future optimal pulse shaping (3D-ellipsoid)
• Measure time-radius correlation
• Dephasing of RF Gun
• Good thermal emittance model is fundamental for
  experiment/simulations

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Schottky Scan
J.Schmerge, GTF
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Laser masking of cathode image at DUVFEL
Above Laser cathode image with mask removed
showing smooth profile. Below Resulting
electron beam showing hot spot of emission.
Above Laser cathode image of air force mask in
laser room. Below Resulting electron beam at
pop 2.
Courtesy W.Graves
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Thermal emittance

• At YAG2
• With low accelerating gradient

Good resolution
Assumes ??th 0.6 mm.mrad
Good resolution (better than at YAG1)
YAG2 Image of divergence of source
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Imaging source divergence what type of
momentum distribution?
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Difficulties of Calibrations

• ?? beam at YAG1 varies with Vrf , ?rf , Gun
  field balance, charge, Solenoid calibration
• calibrate Vrf , ?rf (see slide 21-22)
• rotation of L-shape mask
• then can possibly detect field unbalanced

Fit of DUVFEL measurements
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Gun Spectrometer

• Energy
• Absolute energy
• alignment using laser
• spectrometer field calibration
• Lifts-up ?rf ?? Vrf
• Correlated Energy Spread for all charges
• Uncorrelated energy spread for low charges
• Introducing a time-energy correlation (varying
  injection phase)
• Slice thermal emittance
• Relay imaging system from YAG1 to spectrometer
  screens
• Point-to-point imaging in both planes
• Uniformity of line density
• 3D-ellispoid Emission pulse

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Calibrations, Orthogonality of knobs
Rotation of L-shape mask Vrf Steering
coil (2), offset at YAG1/YAG2 Spectrometer
calibration
Shottky scan (for short bunch 2ps) ?rf
Shottky scan at different gun fields Energy
spread at low/high current in spectrometer
Solenoid Beam size compared at YAG1 / YAG2
Waist vs charge
Gun Balance Offset in solenoid scan
curve Direct field measurement from probes
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Orthogonality ?rf ?? Vrf

• Energy vs Phase (for different Vrf)
• Current vs charge

Operating point 2?? from minimum ??E
Zero Current
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Orthogonality ?rf ?? Vrf

• With finite bunch length

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Low Charge operation
Direct measurement of ?E vs ?rf
Gun spectrometer with all quadrupoles off
Referenced to nominal ?? 32??
Referenced to nominal ?? 32??
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High Charge operation
1nC Nominal tuning no quadrupole on -
Longitudinal at YAG1
YAGG1
YAGG1
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High Charge operation

• Correlated Energy spread vs ?rf
• Calibration ?rf repeated

At YAG1
At YAGG1
PARMELA Simulations for 1 nC Good Linearity
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High Charge operation
1nC, temporal pulse
at YAG1 location
?8 modulation
Nominal phase Quadrupoles off
YAG1
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High Charge operation
Temporal pulse , using quadrupoles to project
on manageable size screen
??RF ?? Quadrupoles on Resolves modulation
at YAG1 location
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More Profile measurement
Standard Beer Can
3D-Ellipsoid
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Straight Ahead Spectrometer
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Longitudinal Phase Space at waist

• Transverse deflecting cavity ?? y / time
  correlation
• (??0.5mrad over 10ps )
• Spectrometer ? x / energy correlation
• Direct longitudinal Phase Space representation

rms
From PARMELA simulations (assuming 1??m
emittance), resolution of less than 10 keV
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Straight Ahead Spectrometer

• Tuned to possibly be used in pulsed mode
• Laminated magnet ceramic chamber

Dx 1m ?x 0.1
Same tuning
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Slice-Emittance Measurement Simulation
sy ? bunch length
RF-deflector at 1 MV
slice OTR 10 times
quad scanned
Courtesy P.Emma
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Slice-Emittance Measurement Simulation
(slice-y-emittance also simulated in BC1-center)
Injector at 135 MeV with S-band RF-deflector
at 1 MV
(same SLAC slice-e code used at BNL/SDL)
slice-5
Courtesy P.Emma
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Conclusions

• Diagnostics were designed to provide
• Tools for performing correctly emittance
  compensation
• 6D characterization of beam at end of injector
• Diagnostics for degraded beam started
• Temporal Modulation laser
• Large emittance gt Energy spread measurement ok
• On-line simulations tools to be chosen
• Fast-tracker (Homdyn, Trace3D, PARMELA ??)
• MP tracker (PARMELA, ASTRA, IMPACT, GPT ??)

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Including Magnets
Treaty Point
Straight Ahead Spectrometer
3 screen emittance measurement
RF Deflecting cavity TCAV1
Gun Spectrometer
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Diagnostics
Current Monitors
Straight Ahead Spectrometer
Wire scanners
Cerenkov Radiator
OTRs
YAGs
Gun Spectrometer
EO monitor
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Z. Huang