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Message ID: 2555     Entry time: Wed Apr 14 09:49:38 2021
Author: Stephen 
Type: DailyProgress 
Category: Cryo vacuum chamber 

2021.04.14 StephenA

QIL Cryo vacuum chamber cooldown was not as successful under the new configuration (radiation shielded by cylindrical outer + inner shields, cold finger thermally strapped to baseplate).

--> Karthik's Si cantilever workpiece was stable at 240 K.

--> Cold Finger was stable at 200 K - there is significant thermal loss between the cold finger and the workpiece.

--> Inner shield was stable at 250 K - seems to be somewhat decoupled from the baseplate; not very satisfied with the current state of the shielding.

Will need to re-examine some of the connections, which were not optimal (especially the improvised dog clamped strap-baseplate interface). Fabricating an adapter piece for the thermal strap which will be bolted 4x on a 2" x 2" grid. Might also look into a new thermal strap which could interface with baseplate directly.

Also will need to consider options to decouple outer shield from inner, and double check that shield orientation has no other solution (hoping there's an answer to the question, why would outer shield be coupled to baseplate?)


Data - cooldown 20210408 (CSV = raw, XLSX = Stephen's plots) in Box Folder [Voyager\MarinerBox\CryoEngineering\CSVlogs]

Description - 6 day cooldown. Layout described in QIL/2552. The radiation shields were installed and thermal strap was connected to baseplate. The cryocooler was turned on/off at the start/end of the data collection, and the in-vac heater was not powered on at all.

Images -

  1. IMG_8570 = starting conditions;
  2. IMG_8585 = final conditions after 144 hours;

Plots -

  1. cooldown_20210408_first_si_workpiece_with_shields_and_straps

Attachment 1: IMG_8570.JPG  2.725 MB  Uploaded Fri Apr 16 12:16:43 2021  | Hide | Hide all
Attachment 2: IMG_8585.JPG  2.363 MB  Uploaded Fri Apr 16 12:17:12 2021  | Hide | Hide all
Attachment 3: cooldown_20210408_first_si_workpiece_with_shields_and_straps.png  28 kB  Uploaded Fri Apr 16 12:19:01 2021  | Hide | Hide all
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