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Entry  Mon Jan 31 15:40:21 2022, Stephen, DailyProgress, , 31 Jan Fastest Radiative Cooling run started 
    Reply  Fri Feb 4 14:00:19 2022, Radhika, DailyProgress, , 31 Jan Fastest Radiative Cooling run started Cooldown_0114_analyzed.pdfCooldown_0131_analyzed.pdfCooldown_0131_copperbar_halfR.pdfCooldown_0131_flexstrap_halfR.pdf
       Reply  Wed Feb 9 15:21:27 2022, rana, Howto, TempCtrl, plots 
    Reply  Mon Feb 7 16:06:36 2022, Stephen, DailyProgress, , 31 Jan Fastest Radiative Cooling run, ended 07 Jan 
Message ID: 2715     Entry time: Mon Jan 31 15:40:21 2022     Reply to this: 2716   2718
Author: Stephen 
Type: DailyProgress 
Subject: 31 Jan Fastest Radiative Cooling run started 

As discussed during the 21 Jan 2022 meeting, the next cryostat run will seek the fastest radiative cooling (again, see QIL/2706) through the following configuration choices:

  • move heater to test mass
  • add thermal grease to inner shield - coldplate interface (clamped joint)

Actions completed 27, 28, and 31 Jan 2022

  • Vent.
  • Remove Test Mass in frame.
    • For simplicity, we snipped the RTD lead (we didn't want to have to redo the cryovarnish joint).
      • Of course, the joint failed during the repairs so we had to redo the workpiece RTD cryovarnish joint anyway!
  • Use cryovarnish to affix heater.
    • Removed aquadag in area of joint using IPA-soaked Alpha wipe and scrubbing motion.
    • First, varnished cigarette paper anchor pad, then added heater.
    • We allowed the cryovarnish to cure overnight between the 27th and 28th, then allowed the joint to hang in its vertical orientation over the weekend to confirm its integrity.
  • Use conventional pin-socket arrangement to add junction to heater leads and workpiece RTD leads.
    • Confirm all RTD leads are functional, and repair crimp joints and Kapton tape insulation where needed.
  • Clean up aquadag flakes on coldplate.
  • Remove inner shield, add Apiezon M thermal grease, and bolt down again.
  • Touch up position of mylar shield on cold linkage, aluminum foil aperture covers.
    • All apertures are covered except:
      • Inner Shield: cold linkage (not an issue - partially occluded by copper bar, mylar tube extends into cold head view and mylar mitten)
      • Outer Shield: electrical port, cold linkage (aperture has been extended to have additional area underneath the original circular aperture)
  • Insert Test Mass in frame. Dog clamp down frame.
  • Pump down, cool down.
    • Pump down started at ~15:15.
    • Cool down started at 15:44.

Model updates required to reflect new configuration:

  • estimate conductive leak from 24 AWG heater leads to test mass
  • model conductance of cryovarnish joint between heater and test mass - does cigarette paper make a difference?
  • model greased joint of inner shield - cold plate interface
    • confirm clamp load is adequate for effective greased joint, at room temp and cold temp!
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