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Undulator Section e- Diagnostics Glenn Decker, ANL / APS April 24, 2002

Undulator Section e- Diagnostics Glenn Decker, ANL / APS April 24, 2002. Overview Beam Position Monitoring Wire Scanners / Cherenkov Detectors Optical Transition Radiation Imaging. Undulator Section Particle Beam Diagnostics. Conceptual Design for Combined Button / Cavity BPM.

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Undulator Section e- Diagnostics Glenn Decker, ANL / APS April 24, 2002

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  1. Undulator Section e- DiagnosticsGlenn Decker, ANL / APSApril 24, 2002 • Overview • Beam Position Monitoring • Wire Scanners / Cherenkov Detectors • Optical Transition Radiation Imaging Glenn Decker, ANL / APS

  2. Undulator Section Particle Beam Diagnostics Glenn Decker, ANL / APS

  3. Conceptual Design for Combined Button / Cavity BPM Glenn Decker, ANL / APS

  4. Principle of operation of BPM waveguide-cavity coupling Port to coax • Dipole frequency: 11.424 GHz • Dipole mode: TM11 • Coupling to waveguide: magnetic • Beam x-offset couples to “y” position • Sensitivity: 1.6mV/nC/m (1.6109V/C/mm) Magnetic Field Lines Beam Direction Zenghai Li, S. Smith, R. Johnson, SLAC Glenn Decker, ANL / APS

  5. Waveguide-Coupled Cavity-Based BPM Model • Dipole frequency: 11.424 GHz • Dipole mode: TM11 • Coupling to waveguide: radial magnetic • Beam x-offset couples to “y” port • Sensitivity: 1.6mV/nC/m • Explicitly does not couple to TM01 6 mm Zenghai Li, S. Smith, R. Johnson, SLAC Glenn Decker, ANL / APS

  6. Coupling scheme eliminates TM01 from output waveguide Dipole Frequency 11.4 GHz (Arb. Units) Fundamental Frequency 8.8 GHz Glenn Decker, ANL / APS

  7. Longitudinal Cavity Impedance 5e3 WL(V/pC) Dipole Mode 0 0 3 6 9 12 15 18 21 24 Frequency (GHz) Glenn Decker, ANL / APS

  8. LEUTL Capacitive Button Pickup Electrodes Electrical Specifications: Frequency: DC to 20 GHz Impedance: 50 ohm nominal, terminated by a capacitive button Capacitance: 4.8 pF nominal VSWR: 1.03:1 max. to 3 GHz, 1.15:1 to 20 GHz Insertion loss: 0.1 db max. to 3 GHz, 0.5 db max. to 20 GHz Matching: +/- 0.5 ohm in impedance, and +/- 0.1 pF in capacitance. Connector: SMA female ,hermetically sealed with glass insulator. Dielectric Strength: >1500 V at 50/60 Hz Leakage Resistance: > 1013 ohm, from center conductor to outer housing Mechanical Specifications: Diameter: 4 mm Materials: As per Kaman P/N 853881-001 Hermeticity: <10-11 cc He/sec Radiation: >200 megarads gamma 4 mm Dia. Drawing courtesy J. Hinkson ALS Glenn Decker, ANL / APS

  9. Button Pickup Electrode Mechanical Drawing Glenn Decker, ANL / APS

  10. Inexpensive Logarithmic Amplifiers for Button BPM Single Channel Four-Channel Unit with Test Ports Courtesy R. Lill, R. Keane, APS Glenn Decker, ANL / APS

  11. BPM Summary • Cavity BPM’s capable of sub-micron-scale resolution, reproducibility • Prototype unit undergoing characterization at SLAC/NLC • Capacitive button pickup electrodes are a mature technology, capable of providing 1 micron resolution / stability for hours / days • “Belt and suspenders” approach assures highest quality beam alignment capability Glenn Decker, ANL / APS

  12. Cherenkov Detector (Upgrade from PEP-II Design) Courtesy W. Berg, APS Glenn Decker, ANL / APS

  13. Cherenkov Detector Electronics (APS Design) Courtesy A. Pietryla, APS Glenn Decker, ANL / APS

  14. Optical Transition Radiation A. Lumpkin, APS Glenn Decker, ANL / APS

  15. OTR Radiation Pattern Glenn Decker, ANL / APS

  16. Glenn Decker, ANL / APS

  17. Optical Transition Radiation (cont’d) • 11 Intra-undulator OTR Electron-Beam Profile Diagnostics are proposed • Thin foils (1-5 microns thick) can be used to minimize e-beam scattering and bremsstrahlung radiation • Conversion efficiency reasonable for ~ 1 nC of charge and CCD cameras • OTR Techniques have been validated in a number of recent experiments: • Beam sizes of 30 um (sigma) for a 600-MeV beam measured at APS with an Al mirror. (Lumpkin et al.,FEL’98) • Beam sizes of 50 microns sigma for a 4-GeV beam at TJNAF with 0.8-micron thin foil (Denard etal, BIW ’94) • Beam size measurements performed at 30 GeV at SLAC (Catravas etal, PAC ’99) • Beam size of 15 microns rms measured at 30 GeV on a single shot at SLAC (Hogan, E-162) Glenn Decker, ANL / APS

  18. Conclusions • Undulator particle beam diagnostics will build upon knowledge base at APS, SLAC and elsewhere. • Majority of diagnostics require minimal development • Important items are • BPM fabrication / fiducialization and mechanical support. Beam-based alignment relaxes requirements considerably • OTR foil survivability (rep rate limitation?) • Decision on bpm electronics topologies – • downconversion / phase detection with cavities vs dumb power monitor • Log-amp, delta/sum, AM/PM etc. for button pickups Glenn Decker, ANL / APS

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