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Injector Physics C.Limborg-Deprey

Injector Physics C.Limborg-Deprey. GTL final design Wakefield budget Final Modifications Commissioning Readiness Schedule Feedback systems An example of tuning procedure Steering in L0a. Injector.  Gun installation Nov. 2006  Gun Region July 2006

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Injector Physics C.Limborg-Deprey

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  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 • <1.05 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 <1.2 mm-mrad • with no error simulations show 1.0 mm-mrad • Stability of electro- magnetic components to meet less than 10% increase • <10 % 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-KuenNg 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 < 0.077V/pC on axis • / < 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

  15. December 06  Schedule

  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 (f<1Hz) : <200 m (or slice emittance degraded) • Fast (1Hz<f<120 Hz): <10 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) < 2%rms • Sensor/Actuator • first toroid IM01/ polarizer

  19. Feedback Systems • Timing Stability • Tolerance • Fast stability (120Hz), laser phase w.r.t master clock < 0.5 ps rms • feedback system • sensor : phase monitor signal • actuator: locking electronics from Thales system • Slow stability (<1Hz), laser phase w.r.t gun phase < +/-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

  21. 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

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