GTS meeting 5 02 17

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Attempted to run at 1 mA

  1. Ran for few seconds before a HV arc. QE dropped by a factor of 2.
  2. Ran again for 1.5 hours with ion-precipitators on (?) before a HV arc. QE dropped by another factor of 2.

List of Tasks (Down Monday – Wednesday)

  1. Re-activate photocathode with 3 mm active area
  2. Degas dump with NEGs at 2 Amps AC on for ion pumps to take vacuum load
  3. Laser ND Filters:
    1. Wheel filters are physically out of laser path (cannot be used).
    2. ND filter with In/Out box in GTS control room can still be used. Is has ND1 filter (a factor of 10).
    3. Shukui installed ND3 filter on spare servo motor 2. We should start using this ND filter. It is now on the Tool Screen.
  4. Instrument wire scanner
  5. Installed WiFi access point in GTS cave and enabled JMenu on PC using NX-Connects and Two-Factor Authentication. Then: ssh fell08, jmenu MainMenuGTS.
  6. Why is Dump/FC picoammeter reading is noisy? up to 20 nA.
  7. Hi-pot VIPGT06
  8. SCAM VL LINE SYNC frequency is not 60 Hz? Need 60 Hz Beam Sync Chassis. Will run with "FREE RUN" mode at 60 Hz.
  9. Put ND filter in front of ITVGT06 and mount camera on the floor.

Beam Gap Clearing

  • An alternative to applying electric field (bias) is removing intrinsic electric field (beam)...
Beam 'off' time of ~few microseconds w/ rep rate at least greater than ~100 Hz should do OK
Additional 'do something' half-wave plate within tune mode generator + User mode...
Spinning optical chopper ?


Ion Precipitators

  1. ion collectors and anode current
  2. The downstream ion collector was wired incorrectly
  3. comparing vacuum conditions 1 mA run 11 Jul 2016 with 28 Apr 2017
  4. This is a sketch of the internals of the downstream ion collector VICGT06
  5. Sketch of ion colelcotr internals VICGT06.jpg
  6. These are Cornell's results
  7. Cornell ion clearing results with electrode voltage equation.jpg
  8. Grames paper on anode bias: Media:Grames_PST07_final.pdf
  9. Pozdeyev PAC 2007 ion trapping: Media:Pozdeyev.PDF
  10. Cornell PRAB paper on ion clearing electrodes: Media:Cornell ion colelctors PhysRevAccelBeams.19.034201.pdf
  11. Gabriel's calculation (POISSON model) of the voltage needed in upstream ion collector (VICGT04, wire sticking out of the spool piece): Media:Ion collector VICGT04 wire stikcing out of spool piece.pdf
  12. CEBAF vacuum during 1 mA run
  13. CEBAFvacuum1mA.png
  14. GTS vacuum 1 mA run April 28 2017
  15. Pmceimghkhgmffji.png
  16. GTS 1 mA run also tripped 1.5 hour July 11 2016
  17. Slide09.jpg