LCLS Gun Status & Plans - slac.stanford.edu · David H. Dowell [email protected] RF Gun...

David H. [email protected]

RF Gun Operations TalkNovember 15, 2006 1

LCLS Gun LCLS Gun Status & PlansStatus & Plans

David H. DowellOperations Talk

November 15, 2006

Description of Injector and the LCLS gunGun cold test resultsCharacterization of magnetic componentsGun high RF power test description and resultsThe 3-Pass Commissioning PlanSummary



RF Gun & Solenoid

Gun Energy Spectrometer

L0a&L0b S-Band Linacs

Laser-Heater

OTRs & Wire Scanners

Straight Ahead Spectrometer

Transverse RF Cavity

L1 S-Band LinacsBunch Compressor 1

Wire Scanners

Bunch Length DiagnosticsX-Band Linac

Injector and Bunch Compressor 1Injector and Bunch Compressor 1Installation is in Progress at Sectors 20 and 21Installation is in Progress at Sectors 20 and 21

Commissioning will begin in Early 2007Gun-to-Linac Region



Gun and GunGun and Gun--toto--Linac ComponentsLinac Components

SOL1Bucking CoilSOL1BK

Drive laser injection

cross

On-axis alignment

laserD

rive

lase

r

Alig

nmen

t las

er

YAG01/FC01

BXG Spectrometer

YAG02

Quads

YAGG1/FCG1

BPMsIM01Current Toroid



Z-coupling: reduces pulsed heatingincreases vacuum pumping

Racetrack to minimize quadrupole fieldsDeformation tuning to eliminate rf tunersIris reshaped reducing field 10% below cathodeIncrease 0-pi mode separation to 15MHzAll 3D features included in modeling:

laser port and pickup probes 3D fields used in Parmela simulation

3D RF Design of Gun3D RF Design of Gun

0.999:1E0:E115Mode Sep. ∆f (MHz)

2.1β

13960Q02.855987f0 (GHz)

RF Parameters

Slide Compliments of Z. Li & L. Xiao

C. Limborg et al., “RF Design of the LCLS Gun”, LCLS-TN-05-3γβ

r/mm

-0.008

-0.006

-0.004

-0.002

0.000

0.002

0.004

0.006

0.008

-180 -120 -60 0 60 120 180

rf phase

cylindrical cavity

racetrack cavity withd=0.124"racetrack cavity withd=0.14"racetrack cavity withd=0.134"γβ

r/mm

-0.008

-0.006

-0.004

-0.002

0.000

0.002

0.004

0.006

0.008

-180 -120 -60 0 60 120 180

rf phase

cylindrical cavity

racetrack cavity withd=0.124"racetrack cavity withd=0.14"racetrack cavity withd=0.134"

L. Xiao et al., “Dual feed rf gun design for the LCLS,” Proc. 2005 Particle Acc. Conf.



Compliments E. Jongewaard

This is a half cavity model used to investigate the effect of aximuthal temperature variation of the cooling water. In this case the water for all channels varies from 24°C on the right to 26°C on the left. This simulates the bulk temperature rise of the cooling water as it progresses along the cooling channel.

Average temperature at Average temperature at 120Hz, 4kW average power120Hz, 4kW average power

August 2005 LCLS RF Gun Mechanical Design Review



GunGun--Solenoid AssemblySolenoid AssemblyCut-away view of LCLS Gun

Cathode weld assemblyAugust 2005 LCLS RF Gun Mechanical

Design ReviewCompliments E. Jongewaard



Gun Fabrication and Testing ProcessGun Fabrication and Testing ProcessFabricate partsCold test sub assemblies and clamped partsMachine and measure for resonance and field balanceBraze and weld final assemblyLow power RF and cathode testsFurnace bake at 500deg CAssemble and configure for high power RF test (hot test)Vacuum bake of assembly in Klystron test vaultPerform hot testCheck gun probe calibrations Vacuum qualification of gunAlignment of assembly with CMMInstall at S20



RF Gun Fabricated and Cold RF TestedRF Gun Fabricated and Cold RF TestedGun only pictures

CAD cutaway viewof gun interior



RF Field Balance Measured Using Bead Drop TechniqueRF Field Balance Measured Using Bead Drop Technique

Data compliments J. Wang, ATR Dept., SLAC



Gun Design and Measured SpecificationsGun Design and Measured Specifications

1152.1139602.855987Design

1Field Balance15.17Mode Sep. ∆f (MHz)

2.03β

14062Q02.855999fπ (GHz)

MeasuredRF Parameters



cathode flange

dual rf power feed

focusing solenoidLCLS RF Gun: Cathode SideLCLS RF Gun: Cathode Side



LCLS RF Gun: Beam SideLCLS RF Gun: Beam Side

beam port:Attach 2-km linac here

focusing solenoiddual rf power feeds



Description of gun Description of gun magnet system magnet system

Gun solenoid: SOL1Bucking coil: SOL1BKX,Y dipole correctors:

XC00&YC00 (inside SOL1)Normal & skewed quad correctors:

CQ01&SQ01 (inside SOL1)Field maps and calibrations measured



Bx and By vs z for dipole correctors at 8ampsz=0 at center of solenoid

By effective length = 9.65cmBx effective length = 9.68cm

-0.0005

0

0.0005

0.001

0.0015

0.002

0.0025

0.003

0.0035

-0.3 -0.2 -0.1 0 0.1 0.2 0.3z(m)

Tran

sver

se fi

eld

(T)

By (T)Bx (T)

Gun Solenoid and Dipole CorrectorGun Solenoid and Dipole CorrectorMagnetic MeasurementsMagnetic Measurements

-0.5

0

0.5

1

1.5

2

2.5

3

3.5

-0.4 -0.2 0 0.2 0.4z(m)

Bz

(kG

)

I-sol=172.76amps

I-sol=147.5958 amps

I-sol=197.93amps

Solenoid current (amps) Effective Length (cm)147.5 19.347172.5 19.354197.5 19.355

Average Effective Length 19.352 cmStandard deviation 0.0044 cm

1

10

100

1000

10000

100000

1000000

-0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4z(m)

foca

l len

gth

(m)

0.E+001.E-052.E-053.E-054.E-055.E-056.E-057.E-058.E-05

quad

upol

e fie

ld (k

G-m

)

focal length(m)@5MeV/cquadrupole kGauss-m



Bucking Coil Magnetic MeasurementsBucking Coil Magnetic MeasurementsBz at cathode vs I-buck

y = -0.0017468xR 2 = 0.9999959

-0.04

-0.03

-0.02

-0.01

0

0.01

0.02

0.03

0.04

-30 -20 -10 0 10 20 30I-buck(amps)

Cat

hode

Bz

(T)

Bucking coil current to zero the cathode field vs. SOL1 current

I buck = 7.06E-07 I sol13 - 1.51E-04 I sol1

2

+ 1.47E-02 I sol1 + 3.01E-01

0

1

2

3

4

5

6

7

8

0 50 100 150 200 250 300SOL1 current (amps)

Buc

king

coi

l cur

rent

(am

ps)



RF Gun/Solenoid RF Gun/Solenoid Assembly in Assembly in

Klystron Test Vault Klystron Test Vault



0.0E+00

5.0E+06

1.0E+07

1.5E+07

2.0E+07

2.5E+07

23 24 24 25 25 26 26 27 27time (microseconds)

RF

pow

er (w

atts

)

gun probegun fwdgun refl

Hot Test RF MeasurementsHot Test RF Measurements

GunFWD & Refl RF

Klys.

RF LoadRF windows

Gun3dB Splitter

4 gun probes

Variable Freq.Oscillator

HV PSIon Pump

Ion PumpKlystron

FWD & Refl RF

inside shielded bunkeroutside at Test Stand 8

0 2 4 6 8 10 12 14 160

50

100

150

Cathode field (MV/m)Stored energy (0.1J)

Incident power (MW)

Cat

hode

E (M

V/m

) / S

tore

d en

ergy

*10

12010.7

121.9MV/m



Recent Conditioning ResultsRecent Conditioning ResultsConditioning of Gun-1 (Shemp) at 30Hz

40

50

60

70

80

90

100

110

120

130

9:36 12:00 14:24 16:48 19:12

Time on Nov 9, 2006

Cat

hode

Fie

ld (M

V/m

)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Dar

k C

harg

e (n

C)

Cathode FieldDark Charge

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

80 90 100 110 120 130

Cathode Field (MV/m)

Dar

k C

harg

e (n

C)

YAG/faraday cupat 120MV/m



show movieshow movie



Images of the cathode surface Images of the cathode surface during RF conditioningduring RF conditioning

5 mm

5 mm

Nov 9, 2:18 pm Nov 9, 4:51 pm



Cathode Qualification System (CQS)Cathode Qualification System (CQS)

• Measures either GTF- or LCLS-style cathodes

• Ion-cleaning, XPS/AES, QE

•Cathode carrier/storage containers are being fabricated



LCLS Cathode#1 Qualification (in CQS)LCLS Cathode#1 Qualification (in CQS)

H2-brazed, diamond fly cut, vacuum fired at 650C for 24 hours, H-ion cleaned

LCLS Min QE



22 angstromse-e scattering length @8.6eV

0.268eVφschottky @50MV/m

4.31eVWork Function, φ

7eVFermi Energy, EF

180 200 220 240 260 280 3001 .10 8

1 .10 7

1 .10 6

1 .10 5

1 .10 4

1 .10 3

0.01

Theory at 0 MV/mTheory at 50 MV/mExperiment

Wavelength (nm)

Qua

ntum

Eff

icie

ncy

( )⎥⎥⎦

⎤

⎢⎢⎣

⎡

+

+−

+

++

+

⎟⎟⎠

⎞⎜⎜⎝

⎛++

−=

−

ωφ

ωφ

ωω

ωφφω

λλ

ωωhhh

h

h

h F

effF

F

effFF

eff

m

eff

mee

optEE

EEE

EE

RQE 212

1)(2

1

)(1)(

2/3

schottkyeff φφφ −=

eV )/(107947.3 5 mVEschottky−×=φ

Expression for QE and comparison with experimentExpression for QE and comparison with experiment

http://www.slac.stanford.edu/pubs/slacpubs/11750/slac-pub-11788.pdf , submitted to PRST-AB



What weWhat we’’ll have at Sector 20ll have at Sector 20ee−− to L0Ato L0A

ee−−

YAG screensYAG screenssolenoidsolenoid

RF gunRF guncathodecathode

UV laserUV laser

spec. dipolespec. dipole

QQ = 1 = 1 nCnCff = 120 Hz= 120 HzGG = 120 MV/m= 120 MV/mγεγεx,yx,y = 1 = 1 µµmm∆∆ττ = 10 ps= 10 psII = 100 A= 100 AEE = 6 MeV= 6 MeV



Injector Commissioning PhilosophyInjector Commissioning PhilosophyCommissioning plan is organized into three passes through the injector

Tasks 2.3.3: 1st passPre-beam and beam-based hardware & software checkout

Tasks 2.3.4: 2nd passFirst-order optics

Tasks 2.3.5: 3rd passFull 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.



Summary of Gun Status & PlansSummary of Gun Status & PlansGun fabrication and cold testing completed

Gun meets all design goalsAll magnetic components calibrated and characterizedGun integrated with solenoid and waveguide assembly

Installed in test vault at KlystronFirst bake of assembly (gun vacuum in high 10-10 Torr)High-power RF (hot) testing completed (gun vacuum 2.5x10-10)Final vacuum qualification & alignment in progress after Hot-Testing

Gun on schedule for installationCommissioning will be done in three passes

Pass 1: Pre-beam checkout and beam-based checkoutFirst transport beam through entire injector & BC1 to TD-11

Pass 2: First-order opticsCharacterize components and beam throughout injector

Pass 3: Full beam CharacterizationOptimize beam quality



The EndThe End



backup slides



The Injector Commissioning The Injector Commissioning Schedule and the 3Schedule and the 3--Pass PlanPass Plan

2.3 Injector commissioning 97 days Thu 11/30/06 Fri 4/13/072.3.1 First Operation of Gun at S20 5 days Thu 11/30/06 Wed 12/6/06

2.3.1.1 RF Processing 5 days Thu 11/30/06 Wed 12/6/062.3.1.2 Resonance control -Testing Temperature control with RF p 5 days Thu 11/30/06 Wed 12/6/062.3.1.3 "EXIT" criteria 0 days Wed 12/6/06 Wed 12/6/06

2.3.2 RF systems (L0 and TCAV) set-up and testing 10 days Thu 11/30/06 Wed 12/13/062.3.2.1 RF Processing 10 days Thu 11/30/06 Wed 12/13/062.3.2.2 Controls with RF power 10 days Thu 11/30/06 Wed 12/13/062.3.2.3 procedure and "EXIT" criteria 0 days Wed 12/13/06 Wed 12/13/06

2.3.3 First Beam through beamline 21 days Wed 12/6/06 Wed 1/3/072.3.3.1 Set Laser and RF Timing 1 day Thu 12/14/06 Thu 12/14/062.3.3.2 Transport beam through GTL 2 days Wed 12/6/06 Thu 12/7/062.3.3.3 Transport beam to BXS dump 16 days Fri 12/8/06 Fri 12/29/062.3.3.4 Transport beam through DL1 3 days Mon 1/1/07 Wed 1/3/07

2.3.4 Diagnostics Commissioning // Beam Optimization in GTL 50.75 days Mon 1/1/07 Mon 3/12/072.3.4.1 Characterize beam properties in GTL 33.25 days Mon 1/1/07 Thu 2/15/072.3.4.2 Diagnostics and Feedbacks commissioning 50.75 days Mon 1/1/07 Mon 3/12/07

2.3.5 Preparation of two standard configurations 24.25 days Mon 3/12/07 Fri 4/13/072.3.5.1 Optimization of Highest "stable charge" configuration 13.25 days Mon 3/12/07 Thu 3/29/072.3.5.6 Optimization of Smallest emittance (with useful charge 11 days Fri 3/30/07 Fri 4/13/07

12/6

12/13

Pass 2

Pass 3

Pass 1

~March 1 2007Approximation of real schedule!



The Gun & GunThe Gun & Gun--toto--Linac Region Linac Region with the Drive Laser Launch Opticswith the Drive Laser Launch Optics

Laser tube from laser room



0.018 0.016 0.014 0.012 0.01 0.008 0.006 0.004 0.002 0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018

0.01

0

0.01

0.02

(0, 0.01, 0, 0)(0, -0.01, 0, 0)(0.001, 0.01, 0, 0)(0, 0, 0, 0.01)(0, 0, 0, -0.01)

B0 = 1.10KG

x (m)

y (m

)

0.01−

0.01

0.01− 0.01 Pattern at lower solenoid fieldexhibits intersecting arcs due tothe large energy spread



0.015 0.01 0.005 0 0.005 0.01 0.015

0.01

0

0.01

0.02

(0, 0.01, 0, 0)(0, -0.01, 0, 0)(0.001, 0.01, 0, 0)(0, 0, 0, 0.01)(0, 0, 0, -0.01)

x (m)

y (m

)

0.01−

0.01

0.01− 0.01

0.025 0.02 0.015 0.01 0.005 0 0.005 0.01 0.015 0.02 0.0250.02

0.015

0.01

0.005

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035B0 = 1.57 KG

0.01−

0.01

0.01− 0.01

High energy

Low energy

E

high energy electrons are just touching at the critical solenoid field



0.02 0.015 0.01 0.005 0 0.005 0.01 0.015 0.02 0.025 0.03 0.0350.02

0.015

0.01

0.005

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035B0 = 1.65 KG

x (m)

y (m

)

0.01−

0.01

0.01− 0.01

High energy electrons separate above the critical solenoid fieldwith the low energy electrons stream out to large radii



Schematic of Drive Laser Launch OpticsSchematic of Drive Laser Launch Optics

M2

To the Gun window and in-vacuum mirror

BS1 BS2

Virtual image of

in-vacuum mirror

Joule meter

Polarizer

Virtual in-vacuum mirror

cameralens

shutter (BCS), rate control

M1

mirrors used to steer laser on cathode

Virtual cathode camera

Wave plate

BS: beam splitter

Laser beam from drive laser



RF Processing and Water & RF ControlsRF Processing and Water & RF Controls2.3 Injector commissioning

2.3.1 First Operation of Gun at S20 2.3.1.1 RF Processing2.3.1.2 Resonance control -Testing Temperature control with RF power2.3.1.3 "EXIT" criteria

2.3.2 RF systems (L0 and TCAV) set-up and testing2.3.2.1 RF Processing2.3.2.2 Controls with RF power2.3.2.3 procedure and "EXIT" criteria

Characterize and test gun water system controlsWater system only, no RFControl loop bandwidthTemp 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 tripInteraction between LLRF & water controls

Pass 1 Pre-Beam Commissioning



2.3.3 First Beam through beamline2.3.3.1 Set Laser and RF Timing

2.3.3.1.1 Calibrate diode and rf cables2.3.3.1.2 Measure time delay between diode and rf signals2.3.3.1.3 Add delay as necessary to trigger laser at desired time during rf signal2.3.3.1.4 Coarse Timing

2.3.3.2 Transport beam through GTL2.3.3.2.1 Find beam on Yag01 and Yag02 then center onto alignment laser centers2.3.3.2.2 Remove Yag01, monitor image on Yag02 and charge in IM01 during measurements2.3.3.2.3 Measure beam centroid position with BPM2 and BPM3 vs solenoid field2.3.3.2.4 Move laser until beam centroid independent of solenoid field variation2.3.3.2.5 View beam on Yag02, change laser beam size and verify e-beam doesn't move2.3.3.2.6 Laser crude centering in gun completed; mark laser center on virtual cathode Use fast diode at gun to time laser in rf envelope

Set launch phase within rf periodSOL1 at nominal field, scan laser phase until beam observed on YAG01Meas. 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 SOL1Vary SOL1 current & move laser on cathode until there is no motion on YAG01Observe beam on YAG02, vary SOL1 current & move laser until there is no motionRecord settings on virtual cathode, virtual mirror, etc.

Setting RF & Centering Laser in SOL1. Then continue transport thru L0a, L0b ending at BXS to set the injector beam energy

Pass 1 Commissioning



Overview of Second Pass Gun/GTL Commissioning

2.3.4 Diagnostics Commissioning // Beam Optimization in GTL2.3.4.1 Characterize beam properties in GTL

2.3.4.1.1 Absolute charge calibration of IM012.3.4.1.2 Setup gun spectrometer and measure beam energy & energy spread2.3.4.1.3 Schottky scan

2.3.4.1.3.1 Measure charge at FC01 vs RF gun phase2.3.4.1.3.2 Compare Schottky data with model

2.3.4.1.4 QE characterization2.3.4.1.4.1 Measure photo-charge ( f rom 10-500 pC) on FC01 vs laser energy

2.3.4.1.4.3 Measure QE spatial profile2.3.4.1.5 Transverse quality of emitted photo-electrons

2.3.4.1.5.1 Uniformity of emission2.3.4.1.5.2 Thermal emittance 2.3.4.1.5.3 Momentum distribution

2.3.4.1.6 Fine adjustment of laser position on cathode2.3.4.1.7 Measure Longitudinal Beam Properties at gun exit

2.3.4.1.7.1 QG01 offset determination + polarity checkout 2.3.4.1.7.2 Measure gun exit energy (low charge, short bunch)2.3.4.1.7.3 Measure energy spread vs injection phase (low charge)2.3.4.1.7.4 Measure bunch length at CRG1 and CR01 (low charge) vs injection phase2.3.4.1.7.5 Longitudinal Phase space at gun exit (high charge, long bunch)

2.3.4.1.8 Coarse Correction laser pulse f or Shottky ef f ect




2.3.4 Diagnostics Commissioning // Beam Optimization in GTL2.3.4.1 Characterize beam properties in GTL

2.3.4.1.1 Absolute charge calibration of IM012.3.4.1.1.1 Setup nominal beam at 200pC2.3.4.1.1.2 Check beam trajectory to AL on YAG01 and YAG022.3.4.1.1.3 Measure charge with FC01 and IM01 vs laser intensity, collect dark current2.3.4.1.1.4 Analyze data for IM01 calibration and enter into data base

2.3.4.1.2 Setup gun spectrometer and measure beam energy & energy spread2.3.4.1.2.1 set bunch charge to 15pC and launch beam at 30degrees2.3.4.1.2.2 set trajectory to Alignment Laser (AL) reference on YAG01/YAG022.3.4.1.2.3 Insert YAG01 & adjust S1 to form waist at YAG012.3.4.1.2.4 Remove YAG01 & remove wakefield plug2.3.4.1.2.5 Turn on gun spectrometer, BXG2.3.4.1.2.6 Sweep BXG current until beam is centered on YAGG1, 2.3.4.1.2.7 Measure beam centroid vs BXG current. Does result agree with BXG field measurements?2.3.4.1.2.8 Measure charge with IM01 and FCG1: Do they agree?2.3.4.1.2.9 Calibration of BPMG1

2.3.4.1.2.10 Measure beam sizes on YAG1 and YAGG1, Do results agree with model?2.3.4.1.2.11 Adjust BXG and SC1 to center beam on YAGG12.3.4.1.2.12 Measure centroid and rms size : convert into energy and energy spread2.3.4.1.2.13 Switch on QG02 and QG03 to values given by model2.3.4.1.2.14 Measure centroid and rms size : convert into energy and energy spread

Second Pass Commissioning Details of Gun/GTL Optimization, 1st of 3 parts

Calibration of charge and energy diagnosticsAlignment procedure for energy measurementsMeasurements of gun beam energy




2.3.4.1.3 Schottky scan2.3.4.1.3.1 Measure charge at FC01 vs RF gun phase2.3.4.1.3.1.1 With laser off measure dark current on FCO1 to test FC01.2.3.4.1.3.1.2 Turn laser on and vary rfphase to maximize measured photo-current emitted from the gun2.3.4.1.3.1.3 Scan over 720 degrees to verify the Schottky scan is periodic with 360 degree period2.3.4.1.3.1.4 Verify the current is emitted only over approximately 120 degrees2.3.4.1.3.1.5 Test for satellite laser pulses and laser timing jitter2.3.4.1.3.1.6 measure laser-RF temporal jitter 2.3.4.1.3.2 Compare Schottky data with model

2.3.4.1.4 QE characterization2.3.4.1.4.1 Measure photo-charge ( from 10-500 pC) on FC01 vs laser energy

2.3.4.1.4.3 Measure QE spatial profile2.3.4.1.4.3.1 Focus laser to approximately 100-200 microns spot size2.3.4.1.4.3.2 Limit laser fluence to values less than or equal to values used in step 6 to prevent damage to cathode2.3.4.1.4.3.3 Scan laser across 2.5 X 2.5 mm array and measure photo-charge on FC01

Second Pass Commissioning Details of Gun/GTL Optimization, 2nd of 5 parts

Schottky scan to determine QE and presence of satellite laser pulsesCharge vs. laser energy to measure QE and linearity (no space charge limit of emission)QE uniformity measurement by rastering laser beam




2.3.4.1.5 Transverse quality of emitted photo-electrons2.3.4.1.5.1 Uniformity of emission2.3.4.1.5.1.1 Point-to-point imaging of cathode on YAG01 , find Vrf, Phase, Solenoid2.3.4.1.5.1.2 Compare electron beam and laser beam profiles2.3.4.1.5.1.3 Repeat at YAG022.3.4.1.5.2 Thermal emittance 2.3.4.1.5.2.1 Divergence to point imaging 2.3.4.1.5.2.2 Compare set point with theoretical model prediction2.3.4.1.5.2.3 Repeat with another set of parameters (Vrf) giving a different magnification 2.3.4.1.5.3 Momentum distribution 2.3.4.1.5.3.1 find solenoid , Vrf , Phase such that waist at YAG02 independent of laser radius2.3.4.1.5.3.2 record profile to be used as momentum distribution in model

Second Pass Commissioning Details of Gun/GTL Optimization, 3rd of 5 parts

Determination of emission uniformity by imaging cathode onto YAG01 and YAG02Thermal emittance by solenoid scan at different gun fieldsDivergence of beam at cathode by parallel-to-point imaging at YAG02Confirm parallel-to-point optics by varying laser radiusRepeat at different gun fields




2.3.4.1.7 Measure Longitudinal Beam Properties at gun exit 2.3.4.1.7.1 QG01 offset determination + polarity checkout 2.3.4.1.7.1.1 find beam on Yag01 and Yag02/ center onto alignment laser centers2.3.4.1.7.1.2 Remove Yag01, monitor image on Yag02 and charge in IM01 during measurements2.3.4.1.7.1.3 Using BPM1 and BPM2 measure beam centroid vs QG01 current2.3.4.1.7.1.4 Analyze data & determine offset of QG012.3.4.1.7.1.5 QG01 is now cheked-out

2.3.4.1.7.2 Measure gun exit energy (low charge, short bunch)2.3.4.1.7.2.1 Measure energy using spectrometer as a function of RF phase and amplitude2.3.4.1.7.2.2 Compare spectrometer energy measurement with solenoid steering coil energy measurement if desired2.3.4.1.7.2.3 Can also compare with solenoid rotation energy measurement if desired2.3.4.1.7.2.4 Calibrate SC01 (QG01), SCG1(QG02),SCG2 (QG03)2.3.4.1.7.2.5 Determine offset in QG01,QG02, QG032.3.4.1.7.2.6 Verify calibration of QG01,QG02, QG03 w.r.t model (from magnetic measurements)

2.3.4.1.7.3 Measure energy spread vs injection phase (low charge)2.3.4.1.7.3.1 Set up beamline for energy spread measurement on spectrometer screen2.3.4.1.7.3.2 Verify laser pulse length less than 2 ps FWHM2.3.4.1.7.3.3 Measure beam size on spectrometer screen as a function of RF phase and amplitude

2.3.4.1.7.4 Measure bunch length at CRG1 and CR01 (low charge) vs injection phase2.3.4.1.7.5 Longitudinal Phase space at gun exit (high charge, long bunch)2.3.4.1.8 Coarse Correction laser pulse for Shottky effect

Second Pass Commissioning Details of Gun/GTL Optimization, 4th of 5 parts

Beam alignment and calibration checks of BXG and quadsGun beam energy and energy spread vs. laser phase

Low charge, short bunchLow charge, 10ps bunchHigh charge, 10ps bunch




2.3.4.2 Diagnostics and Feedbacks commissioning2.3.4.2.1 Feedback loops2.3.4.2.1.1 Commissioning Phase monitor2.3.4.2.1.2 Laser Energy 2.3.4.2.1.3 Gun /Voltage / Phase 2.3.4.2.1.4 Transverse orbit feedback in GTL2.3.4.2.1.5 Transverse orbit feedback for Matching Section 2.3.4.2.1.6 details to come2.3.4.2.2 First projected emittance measurement2.3.4.2.2.1 Measurement with WS2.3.4.2.2.2 measurement with OTRs2.3.4.2.3 First Bunch length measurement with TCAV2.3.4.2.3.1 checkout TCAV2.3.4.2.3.2 low charge with different RF phase2.3.4.2.3.3 Laser profile Shottky effect correction2.3.4.2.4 First Slice emittance (H) measurement 2.3.4.2.5 First Longitudinal Phase Space measurement2.3.4.2.6 First slice emittance (V) measurement

Second Pass Commissioning Details of Gun/GTL Optimization, 5th of 5 parts

Beam-based feedback systems tested and enabledFirst emittance and bunch length measurements




Integrated operation with entire injectorProjected and slice emittance optimization (Gun solenoid & laser shape)Longitudinal phase space measurements

2.3.5 Preparation of two standard configurations2.3.5.1 Optimization of Highest "stable charge" configuration2.3.5.1.1 Tune GTL2.3.5.1.2 Emittance vs Solenoid2.3.5.1.3 Emittance vs Injection phase

2.3.5.1.4 Emittance vs L0a voltage2.3.5.1.4.1 Scan Solenoid, Injection phase for each voltage2.3.5.1.5 Test Automated Optimization procedure of 3 parameter scan (S1,Phase, L0a amplitude) 2.3.5.1.8 Perform a S2 scan

2.3.5.1.2 Optimize laser pulse 2.3.5.1.2.3 check laser pointing 2.3.5.1.2.2 adjust correction for Shottky effect (using TCAV)

2.3.5.1.3 Beamline Optimization2.3.5.1.3.1 3D parameter scan for different laser pulse radii 2.3.5.1.3.2 repeat at different pulse length2.3.5.1.9 Longitudinal Phase space measurement

2.3.5.6 Optimization of Smallest emittance (with useful charge) configuration2.3.5.6.12 Fine Tuning GTL2.3.5.6.2 Optimize laser pulse for that charge (radius, length, correction Shottky)2.3.5.6.3 Emittance vs 3D parameter scan ( L0a amplitude, solenoid , Phase )2.3.5.6.5 Longitudinal Phase space measurement2.3.5.6.6 Refine optimization

Third Pass Commissioning Details of Gun/GTL Optimization


LCLS Gun Status & Plans - slac.stanford.edu · David H. Dowell [email protected] RF Gun...

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