GTS meeting 1 17 17

• After the gun had been conditioned to 340kV in vacuum, we turned on the magnetized beam coil to 200 Amps and ramped the voltage, slowly up to 340kV.
  • Notice how the signal from the the gun ion pump current responds to the the magnet coil current, as expected
  • BUT the ion pump current ALSO responds to the voltage with the magnet ON: UNEXPECTED! Why the voltage affects the gun ion pump current with the magnet on?
  • GTSLOG showing the ion pump current responding to magnet coil and to gun voltage
  • We will isolate the gun ion pump from the magnetic field, and also monitor the bake ion pump. If it is real vacuum activity, both pumps will show the same behavior with gun voltage and magnet coil on.
  • After increasing the gun voltage to 340kV and with the magnet at 200 Amps, the gun tripped off, resulting in field emission.
  • The gun got re-condtioned with Krypton, and now shows 20 CPS of field emission at 325 kV.
  • We need to re-condition the gun at the chosen operating voltage (300kV, 325kV) for each magnet current setting: 100A, 200A, 300A, and 400A.

• On another note, the gun was soaked at 365 kV w/Kr for about 10 hours!
  • this shows the robustness of the high voltage package: Cable/insulator plug, Yan;s shed design for 10 MV/m at 350kV, bulk semi-conducting ceramic, and Barrel polished electrodes!

• Mamun and Yan successfully heated the new photocathode puck using the sapphire roller external spring holder.
  • They also grew a Sb layer using the mask,
  • But after applying alkalies, they have not seen photocurrent.

• Beam Line Vacuum
  • Bubba is almost done with the spool piece / bellow / ion precipitator between the two diagnostic crosses.
  • Survey and Alignment crew are working today on aligning the slits and fiducializing them to the cross.
  • We are still waiting on JT to complete the other two spool pieces.
  • We are aiming to have the beam line assembled and surveyed by the end of next week, to start vacuum and bake.
  • Media:Beamline 12-9-16 ISO VIEW.jpg
  • Media:Beamline 12-9-16 SIDE VIEW.jpg

• Beam line I&C
  • Keith Cole asked for a meeting to define what we need and when
  • We need to complete the viewer limited SCAM mode (point of contact?)
  • We also need a 3 position actuator for each of the two diagnostic crosses. We have now a 2 position actuator. Who provides what? Who does what? Carlos will schedule this meeting for this week.
  • For high current / lifetime we will need to control the insertable Faraday cup, and add Kevin's diagnostic cross. When?