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SLSP 5246-4 activated well on April 7 th

SLSP 5246-4 activated well on April 7 th. Used LLGUN2 modestly for remaining SAD and Physics start-up OK through April 24 th. Field Emission begins? on April 24 th (QE has fallen significantly already)…. Opportunistically hi-pot HV chamber on 4/27.

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SLSP 5246-4 activated well on April 7 th

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  1. SLSP 5246-4 activated well on April 7th Used LLGUN2 modestly for remaining SAD and Physics start-up OK through April 24th

  2. Field Emission begins? on April 24th(QE has fallen significantly already)…

  3. Opportunistically hi-pot HV chamber on 4/27. • Reach ~120kV each time … finally, viewer flashes (light, not electrons?) • Anode current reduced from ~60pA to ~30pA Wafer preserved in PREP =>

  4. Beam orbit drifting for last few days (over April-May weekend…) • Tunnel investigation on May 1 • Lasers check out OK • Hall B laser spot fixed (result of bad beam tweeking…) • QE now very bad (max ~0.07%) Found anode isolation bad (30k Ohm instead of 50 Ohm) Limp along with spot moves, but QE falls rapidly….

  5. FE emission begins 4/24, orbit drift with hi-potting 4/27, but stabilizing ….

  6. Gun2 wafer activated May 6th very well (1.2%), OK for program, but continues to drop… • Connected picoammeter to anode for investigation(anode connection good) • Anode current >20pA always (except when HV off) • Calibration of HVPS/anode suggests ~120nA FE per 1pA of anode current • Anode current: <50pA beam ON, but up to 150pA when beam OFF

  7. May 11th : Vacuum burps even when HVPS has been off… vary IP voltage? Ground cage?

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