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Entry  Fri Jul 16 23:28:24 2021, Koji, Summary, Cryo vacuum chamber, Sus Test Work 07/16/2021 7x
    Reply  Sat Jul 17 00:55:41 2021, Koji, Summary, Cryo vacuum chamber, Temp Log 210716_2255 temp_log_cool_down_20210716_2255.pdf
       Reply  Mon Jul 19 15:57:17 2021, Stephen, Summary, Cryo vacuum chamber, Temp Log 210716_2255 
          Reply  Mon Jul 19 17:21:19 2021, Koji, Summary, Cryo vacuum chamber, Temp Log 210716_2255 temp_log_cool_down_20210716_2255.pdf
             Reply  Tue Jul 20 11:33:52 2021, Koji, Summary, Cryo vacuum chamber, A cooling model (Temp Log 210716_2255) cooling_model.pdfIMG_9390.JPGIMG_9391.JPG
                Reply  Tue Jul 20 17:28:30 2021, Koji, Summary, Cryo vacuum chamber, A cooling model (Temp Log 210716_2255) cooling_model.pdf
                   Reply  Wed Jul 21 21:05:59 2021, Koji, Summary, Cryo vacuum chamber, Test mass cooling (2021/07/16 ~ 2021/07/21) oplev_trend.png20210721201333_IMG_0765.jpeg20210716234113_IMG_0742.jpegScreenshot_from_2021-07-21_20-19-09.png
                      Reply  Thu Jul 22 22:03:45 2021, Koji, Summary, Cryo vacuum chamber, Test mass heating in progress (2021/07/21 ~ 2021/07/23) IMG-9395.jpgtemp_log_warmup_20210721_2052.pdf
                      Reply  Sun Jul 25 21:45:46 2021, Koji, Summary, Cryo vacuum chamber, About the radiation heat transfer model 
Message ID: 2611     Entry time: Tue Jul 20 17:28:30 2021     In reply to: 2610     Reply to this: 2614
Author: Koji 
Type: Summary 
Category: Cryo vacuum chamber 
Subject: A cooling model (Temp Log 210716_2255) 

Updated the model the latest log data with cooling prediction

  • The radiative cooling is expected to be the dominant cooling mode.
  • It will take ~3 more days to reach 123K. We don't need to wait for it.
  • For more informative temp data, we need the temperature of the inner shield and the table.

  • We know the cold head temp from the measurement. For the prediction, the constant cold head temp of 65K was assumed.
  • The table temp was estimated using conductive cooling model + linear empirical dependence of the conductivity on the temp
  • The constant specific heat of the silicon mass (0.71 J/K/g) was assumed. This may need to be updated.
  • The radiative cooling is given from Stefan–Boltzmann law with the emissivity of 0.15 for both the shield and the mass.
     
  • The conductive cooling of the test mass was estimated using: Wire diameter 0.017" (=0.43mm), 4 wires, length of ~10cm (guess), no thermal resistance at the clamps (-> upper limit of the conductive cooling)

Radiative cooling already gives us a good agreement with the measured temp evolution for the test mass. The conductive cooling is not significant and does not change the prediction.


Updated the plot with the new data (2021/7/21 12:30PM)

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