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Long-lived electrons

ECLOUD07 Conference & Electron Cloud Instrumentation in the Main Injector Bob Zwaska Accelerator Physics Department Meeting May 16, 2007. Long-lived electrons. Low energy electrons trapped in quadrupole. ECLOUD 2007 Workshop. April 9-12, 2007 -- Daugu, ROK 38 participants

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Long-lived electrons

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  1. ECLOUD07 Conference&Electron Cloud Instrumentation in the Main Injector Bob ZwaskaAccelerator Physics Department MeetingMay 16, 2007

  2. Long-lived electrons Low energy electrons trapped in quadrupole

  3. ECLOUD 2007 Workshop • April 9-12, 2007 -- Daugu, ROK • 38 participants • Most from Asia (KEK, KNU, China) • Several from US. (LBL, LANL, ORNL, CESR, FNAL…) • 2 from Europe – none from CERN • Presentations online at: • http://chep.knu.ac.kr/ecloud07/index.html • Talks linked in the program PDF

  4. Grooves for ILC DR Cloud density near (r=1mm) beam (m-3) before bunch passage, values are taken at a cloud equilibrium density. Solenoids decrease the cloud density in DRIFT regions, where they are only effective. Compare options LowQ and LowQ+train gaps. All cases wiggler aperture 46mm.

  5. SEY test station in PEP-II LER 0o position 45o position

  6. Compare vacuum chamber e- currents 18 March 2007 Grooves don’t work groove1 groove2 flat2 flat1 Measured e- current in TiN/Al fin/flat chambers << StSt chamber. PEP-II LER current still raising (2.7A  4A).

  7. Very Successful Conditioning (lab)

  8. Even More successful (KEK)

  9. Summary • Progress in electron cloud study, but questions remains • SE model is at the core of problems • Long lived electrons? • Excellent conditioning in lab • Not as good in accelerators • Type of conditioning matters • Still observing electron cloud worldwide • No consistent solution has been discovered

  10. Present MI Installation • Electron detector in MI straight section • Only see clear signal with highest intensities • Requires filtering • Slow signal

  11. Upgrade Plans for Shutdown • Better measurements • New cables for cleaner signal • Add data recorder (computer w/ digitizer) • New ion gauge and extra flanges for more detectors • Experimental possibilities • Add weak solenoid for suppression • Add proof-of-principle clearing electrode • Being designed presently (Alex Chen) • Probably kapton-shrouded stainless

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