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Entry  Fri Sep 24 13:12:00 2021, Radhika, General, Heat Load, Mariner cooldown model status + next steps 
    Reply  Mon Sep 27 17:01:53 2021, rana, General, Heat Load, Mariner cooldown model status + next steps 
       Reply  Wed Sep 29 16:15:19 2021, Radhika, General, Heat Load, Mariner cooldown model status + next steps Heat_Load_Sketch_geometry.pdfHeat_Load_Sketch_diagram.pdfheating_cooling_P_vs_T.pdfCooldownTM_radiative.pdf
          Reply  Tue Oct 5 17:46:14 2021, Radhika, General, Heat Load, Mariner cooldown model status + next steps Heat_Load_Sketch_all.pdfVaryingISA.pdfCooldownTM.pdf
             Reply  Fri Oct 15 13:45:55 2021, Radhika, General, Heat Load, Mariner cooldown model status + next steps VaryingTMl.pdf
                Reply  Fri Oct 15 14:31:15 2021, Radhika, General, Heat Load, Mariner cooldown model status + next steps VaryingISA.pdfVaryingTMl.pdf
Message ID: 37     Entry time: Tue Oct 5 17:46:14 2021     In reply to: 32     Reply to this: 42
Author: Radhika 
Type: General 
Category: Heat Load 
Subject: Mariner cooldown model status + next steps 

Building on [32], I added a copper cold finger to conductively cool the inner shield, instead of holding the inner shield fixed at 77K. The cold finger draws cooling power from a cyro cooler or "cold bath" held at 60K, for simplicity. I added an outer shield and set its temperature to 100K. The outer shield supplies some radiative heating to the inner shield, but blocks out 295K heating, which is what we want. The expanded diagram can be seen in Attachment 1. 

I wanted to find the optimal choice of inner shield area (AIS) to maximize the radiative cooling to the test mass. I chose 5 values for AIS (from ATM to AOS) and plotted the test mass cooldown for each in Attachment 2. The radiative coupling between the inner shield and test mass is maximized when the ratio of the areas, ATM/AIS, is minimized. Therefore, the larger AIS, the colder the test mass can be cooled. Even though choosing AIS close to AOS increases the coupling between the 2 shields, the resulting heating from the outer shield is negligible compared to the enhancement in cooling.

I chose AIS = 0.22 m2 to model the inner shield and test mass cooldown in Attachment 3. The test mass reaches 123 K at ~ 125 hours, or a little over 5 days. I have pushed the updated script which can be found under mariner40/CryoEngineering/MarinerCooldownEstimation.ipynb.

Attachment 1: Heat_Load_Sketch_all.pdf  27 kB  | Hide | Hide all
Heat_Load_Sketch_all.pdf
Attachment 2: VaryingISA.pdf  20 kB  | Hide | Hide all
VaryingISA.pdf
Attachment 3: CooldownTM.pdf  15 kB  | Hide | Hide all
CooldownTM.pdf
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