David H. Dowell [email protected]RF Gun Operations Talk November 15, 2006 1 LCLS Gun LCLS Gun Status & Plans Status & Plans David H. Dowell Operations Talk November 15, 2006 Description of Injector and the LCLS gun Gun cold test results Characterization of magnetic components Gun high RF power test description and results The 3-Pass Commissioning Plan Summary
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LCLS Gun Status & Plans - slac.stanford.edu · David H. Dowell [email protected] RF Gun Operations Talk November 15, 2006 1 LCLS Gun Status & Plans David H. Dowell Operations
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Description of Injector and the LCLS gunGun cold test resultsCharacterization of magnetic componentsGun high RF power test description and resultsThe 3-Pass Commissioning PlanSummary
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
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
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
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
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 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
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
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
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
2.3.5.1.3 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