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Injector Diagnostics Status

Injector Diagnostics Status. LCLS DOE Review October 25, 2006 Henrik Loos Diagnostics overview Beam profile monitors Wire Scanners Transverse Cavity Toroids, BPMs, BLM see J. Frisch. Charge Toroids (Gun, Inj, BC, Und) Faraday cups (Gun & Inj) Trajectory & energy

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Injector Diagnostics Status

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  1. Injector Diagnostics Status LCLS DOE Review October 25, 2006 Henrik Loos Diagnostics overview Beam profile monitors Wire Scanners Transverse Cavity Toroids, BPMs, BLM see J. Frisch

  2. Charge Toroids (Gun, Inj, BC, Und) Faraday cups (Gun & Inj) Trajectory & energy Stripline BPMs (Gun, Inj, Linac) Cavity BPMs (Und) Profile monitors (Inj), compare position with alignment laser Transverse emittance & energy spread Wire scanners YAG screen (Gun, Inj) OTR screens (Inj, Linac) Bunch length Cherenkov radiators + streak camera (Gun) Transverse cavity + OTR (Inj, Linac) Coherent radiation power (BC) Slice measurements Horizontal emittance T-cavity + quad + OTR Vertical Emittance OTR in dispersive beam line + quad Energy spread T-cavity + OTR in dispersive beam line LCLS Diagnostics Tasks

  3. LCLS Injector Diagnostics YAG, FC YAG Toroid T-Cavity Phase Monitor Wire Scanner Toroid OTR Toroid OTR YAG

  4. Diagnostics Through BC1 RF Gun & Solenoid L0a&L0b S-Band Linacs T-Cav Sec 29 Transverse RF Cavity Bunch-Compressor-1 (BPM, OTR, collimator) OTR & Wire Scanners Gun Spectrometer L1 S-Band Linac Wire Scanners + OTR 135 MeV 250 MeV TD-11 stopper X-Band RF Straight Ahead Spectrometer Bunch Length Diagnostics 40 m

  5. Requirements for YAG & OTR Monitors Large 50mm crystal required for gun spectrometer. Zoom lens needed. Requires foil with and angle of 5 deg to the beam and a likewise tilted camera to keep the entire screen in focus. Very high resolution required. Special optics design needs to be developed.

  6. YAG screens High yield at low energy 108 Photons at 5pC 100µm to meet resolution Saturation at high charge densities Combined with Faraday cup in GTL -> camera shielding Thin mirror (1mm) at higher energies OTR screens Small yield Aluminum foil 1µm Mitigates radiation issue Foil damage is concern Limited z-space Foil at 45 degree Depth of field ~1mm Match reflection direction with TCAV or dispersion direction Beam Profile Monitor Specifications

  7. Used for all standard YAG/OTR screens Telecentric lens 55mm focal length >100 line pairs/mm Magnification up to 1:1 Stack of 2 insertable neutral density filters Beam splitter and reticule for in situ calibration Megapixel CCD with 12bit and 4.6µm pixel size Radiation shielding in gun region CCD Lens Filters Vacuum OTR Beam splitter Reticule YAG e-beam Illumination Optics Layout

  8. OTR/YAG Optics Design Actuator Optics Box CCD Screen Lens Filters Beam Splitter Reticle Courtesy V. Srinivasan

  9. OTR Profile Monitors

  10. OTR Imager for Spectrometer • Need wide field of view in focus for measurements in spectrometer beam line • Tilt OTR screen and CCD by 5 degrees in 1:1 imaging • 12um resolution tested • Device ready to install B.X. Wang et al. PAC05

  11. Simulation of OTR Beam Size Measurement • Simulation of CCD image • Include 0.5% TR yield, photon shot noise, and typical CCD parameters for quantum efficiency, read out noise, pixel size, digitizer gain • Calculation of beam size • Generate beam profile with 10σ bounding box • Compare rms width of profile with original Gaussian beam size • Simulation agrees well with OTR measurement at GTF • Error of 5% in beam size for beam of 0.1nC, 260µm at 10µm resolution Q = 0.1nC E = 135 MeV

  12. YAG Efficiency YAGG1 beam image at 5 pC • Nφ = 14µm-1 l sin2(θ/2) • l = 0.1mm,θ = 70mrad,Nφ = 1.7/e- • 1nC: Nφ = 1*1010 • 200pC: Nφ = 2*109 • 5pC: Nφ = 5*107

  13. CCD Camera and Lens Test Uniq Vision CCD Dark Image Test TECM55 lens with ruler (scale 1/64”) Periodic BG structure removed with background subtraction Resolution: B/W transition < 20um

  14. y CCD Image x Rows YAG Crystal Profile Monitor Controls • Rate limit electron beam • Single bunch & burst mode • Prevent foil damage and limit camera irradiation • Camera control • Cameralink and EPICS IOC • Buffered acquisition@10Hz • Screen update @1Hz • Image processing • Flip image to match image coordinates with beam • Background subtraction • Automated image cropping • Beam size calculation • Different algorithms • Gaussian fit • Baseline cut, etc. Mock-up

  15. Software Development

  16. Profile Monitor Commissioning Tasks • Verify correct image polarity and calibration. • Compare with alignment laser, BPMs and wire scanners. • Find proper attenuation filter for YAG profile monitors. • Determine beam center with alignment laser.

  17. Wire Scanner Status • Requirements • Step size 5um • Accuracy 2um, reproducibility 10um • Tungsten wire 20um to 60um, matched to beam size • Hardware status • Wire scanners for injector tested to meet specs and calibrated • Photomultipliers with charge integrating ADCs tested • Software status • Low level EPICS • Calibration tool • Scan user interface to select 1 or more wires • Buffered acquisition linked to timing system • High level Matlab • Software for normalization with toroid and jitter correction with BPM to be completed in November • Profile analysis and emittance calculation same as for profile monitors

  18. Requirements

  19. Design - Mechanical Distance Measurement (LVDT or similar) Motor Beam Limit Switches

  20. Current Status

  21. User Interface - Operations

  22. TCAV in injector @ 135 MeV Low field of 1.4 MV sufficient Invasive measurements on OTR2, 4, S1, YAGS2 TCAV in Sector 25 at 5.9 GeV Max field of 25 MV Parasitic measurement with horizontal kicker and off-axis OTR Vertical Deflecting Cavity Horizontal Kicker Electron Beam Off-axis Screen Transverse Cavity Bunch Length Measurement

  23. Injector TCAV • TCAV tested successfully at full gradient in klystron lab • 3MW, 120Hz, 3us pulse • 2MW, 120Hz, 3us pulse was requirement

  24. Transverse Cavity Calibration • Temporal resolution limited by beta function, RF power, screen size • Calibration with TCAV phase scan • Calibration accuracy limited by phase jitter • TCAV injector: >>20 slices possible • TCAV linac: <5 slices due to limited RF, non-dedicated optics, screen resolution Mock-up Mock-up

  25. Software Development

  26. Commissioning Readiness • Redundancy in diagnostics, independent methods to determine the most important beam parameters • Before commissioning check-out of each device by physicist to verify proper functioning and correct assignment in control system

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