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Entry  Fri Nov 12 14:31:38 2021, Stephen, Radhika, DailyProgress, Cryo vacuum chamber, Radiative Cooling of Si Mass, with better shield emissivity IMG_2738.jpegIMG_2741.jpegIMG_2742.jpegIMG_2745.jpegIMG_2747.jpeg
    Reply  Fri Nov 19 14:01:40 2021, Stephen, Radhika, DailyProgress, Cryo vacuum chamber, Radiative Cooling of Si Mass, with better shield emissivity comp_cooldown_728_cooldown_1116.pdf
    Reply  Fri Dec 10 15:58:57 2021, Stephen, DailyProgress, Cryo vacuum chamber, Radiative Cooling of Si Mass, with worse inner shield inner surface emissivity 
       Reply  Thu Dec 16 15:54:44 2021, Stephen, Radhika, DailyProgress, Cryo vacuum chamber, Radiative Cooling of Si Mass, with worse inner shield inner surface emissivity - CTC100 temperature control success cooldown_12-10_all.pdfcooldown_12-10_vs_11-16.pdf
          Reply  Tue Dec 21 15:33:39 2021, Stephen, DailyProgress, Cryo vacuum chamber, Radiative Cooling of Si Mass, with worse inner shield inner surface emissivity - next run repeating 
             Reply  Wed Dec 31 15:59:59 1969, Stephen, DailyProgress, Cryo vacuum chamber, Radiative Cooling of Si Mass, with worse inner shield inner surface emissivity - retry run was successful cooldown_12-21_vs_12-10.pdfMegastat_Heat_Load_Sketch.png12_21_cooldown_fit.png
Message ID: 2697     Entry time: Fri Nov 19 14:01:40 2021     In reply to: 2695
Author: Stephen, Radhika 
Type: DailyProgress 
Category: Cryo vacuum chamber 
Subject: Radiative Cooling of Si Mass, with better shield emissivity 

[WIP]

11/16 was the first Megastat cooldown after exchanging the copper braid linkage for a copper bar. Attachment 1 compares the cooldown trends for the test mass, inner and outer shields, and cold head. The solid curves are the new cooldown trends (copper bar), and the faded dashed curves are the previous cooldown trends (copper braid).

Immediate observations:

    - The coldhead has a reduced heat load, and interestingly a second time constant governs cooldown from ~2-35 hours.

    - The inner shield time constant is reduced significantly, but the inner shield experiences a slightly greater heat load at steady state.

    - The test mass cooling is improved as expected, given inner shield cooldown.

    - The coupling between the outer shield and inner shield has increased, resulting in greater cooling of the outer shield. This could explain the added heat load to the inner shield. 

Attachment 1: comp_cooldown_728_cooldown_1116.pdf  28 kB  Uploaded Fri Dec 10 15:03:21 2021  | Show | Show all
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