GTS meeting 5 31 16

• We ran beam for RadCon Surveys
  • 300keV DC beam 1.6 uA on the Dump
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  • And yes...with the multi-alkali photocathode the current has increased to 1.7 uA after one hr of running beam.
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  • The laser variable attenuator is not working, so we started to steer beam through the viewers, but seems the beam is too intense.
  • Yan steered the beam to the dump, which reportes 1.6 micro-Amps! This made the vacuum increase from 1E-11 Amps, to about 1E-6 Amps when the beam was at each viewer.
  • Shukui has a plan to have full control of the laser output power and variable attenuator. It involves setting up a PC in the GTS, and a new ThorLabs variable attenuator wheel.
  • William Lu and Keith Cole are working on getting the beam dump Kethley signal to EPICS
  • First we ran at 275kV, then at 300kV, stable!
  • Oh! The electricians wired up a GTS enclosure light switch! it works!

• What do we do next!?
  • RadCon requested more 300kV beam time Wednesday afternoon around 2:30 pm. We will need about the same amount of laser power to deliver ~1.6 uA of beam!
  • Yan points out that emittance measurements will be very difficult, if not impossible, because the solenoid is not counter wound.
  • Due to the cathode electrode misalignment, the Haimson coils are not strong enough to center (H) the beam on the solenoid.
  • Align beam on solenoids, perhaps need to physical adjust the first solenoid mount.
  • Need to write a beam measurements and cathode lifetime studies plan.
  • Want a camera on top viewport to look at laser spot on the cathode

• Before going to higher beam current, Need to short out the conditioning resistor.
  • At 1 micro-Amps beam current, the voltage drop on the cathode is already 0.3 kV, at 100 micro-Amps it will be 30 kV!!! because the resistor is 300 Mega-Ohms.
  • We should let Shukui take the time to give us full control of the laser power and attenuator.

• What else?....