-- MarkWard - 22 Feb 2017

Darco

  • Damage to the TPC anode last week was repaired / strengthened with epoxy
  • Used a small cluts of Kapton tape to hold spacers in place around the anode ring for easier assembly
  • Cleaned both meshs with alcohol, long periods of cleaning with the air blower, lots of inspection for issues
  • Reassembled darco
  • Captured focus frame, correct position is with the bottom rail fully pushed in.
  • Performed 3 day pumpdown to remove any impurities introduced that would outgas due to kapton tape and exposure to air.
  • Ramp up on 20th was interesting, starting pressure 3x10^-6 torr, backfilled with CF4 to 52.7 torr (target was 50)
  • Target anode voltage was 500V
  • witnessed large diffuse like sparking from 220V onwards, not enough to light up the chambre but still intense spots.
  • Perofmed ramping with hold periods and achieved around 400V
  • Odd behavour with two glowing spots appearing, the first at 300V, top left which appears to illuminate the source, on voltage change of the anode it went away... odd. on reaching 400 volts another glow about 20-30 counts above background appears around the bottom left. Appears to depend on the cathode voltage.
  • Lack of tracks is frustrating, Jocelyn suggested/asked "Are we sure that is an alpha source"
  • Answer, checked in the undergraduate lab... no... it is not an alpha source frown
  • Borrowed source from the alpha setup in the lab, cleaned it (with permission) and installed in darco
  • Performed voltage ramp, see large sparks around the source... but no tracks, annode reached a voltage of 500 without any sparking.
  • Slow ramp to 600V, noticed spots being generated around the source but nowhere else...
  • Had a small short on the mesh, yet another dissasembly, rotation of the mesh and repump down
  • Note that the mesh had evidence of discolouration near the source...

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Topic revision: r2 - 22 Feb 2017 - MarkWard

 
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