40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
  ATF eLog  Not logged in ELOG logo
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: 2702     Entry time: Thu Dec 16 15:54:44 2021     In reply to: 2701     Reply to this: 2704
Author: Stephen, Radhika 
Type: DailyProgress 
Category: Cryo vacuum chamber 
Subject: Radiative Cooling of Si Mass, with worse inner shield inner surface emissivity - CTC100 temperature control success 

This post will host plots and trends from this radiative cooling run. At a glance, the tuned CTC100 PI control was able to control the workpiece steady state temperature in this radiative cooling test within .005 K.

Run description: At 4 pm Wednesday, the workpiece temperature was at steady state from the QIL/2701 cooldown, a little less than 120 K. From 4pm Wednesday thru 5pm Thursday (25 hours) the CTC100 controller was actuating on the workpiece RTD temperature (cryovarnished to the suspended Si mass) using the resistive heater (dog clamped to baseplate with indium foil gasket). The conductive heating of the cold plate, and therefore the inner shield, led to radiative heating capacity (via ΔT)  that actuated on the temperature of the suspended test mass. As found in QIL/2643, the suspended Si mass is well isolated from conduction to the cold plate.

Before the run, the CTC100 PID controller was allowed to autotune using a long lag (600 s) and a moderate acutation step (10 W). After autotuning, the D term was still 0, which seemed fine.

Data: Attachment 1 plots cooldown curves for all RTDs during this run. Attachment 2 compares this run's test mass and inner shield temperature curves to those from the previous run (Aquadag on inner surface of inner shield). The expected result of this change (coating inner surface of inner shield with Al foil) is a weakened radiative coupling between the inner shield and test mass, leading to less effective cooling of the test mass. 

Initial observations from data:

1) The cold head temperature curve again suggests 2 time constants, and cooldown is identical.

2) The inner shield's cooldown is roughly unchanged.

3) The outer shield's temperature drops significantly more, indicating a stronger coupling to the inner shield. We will check for a conductive short the next time we open up.

4) The test mass's cooldown matches expectations (weaker radiative coupling).

[WIP - The data will be fitted and discussed]. More detailed analysis from fit to come, including from heater runs.

 

Attachment 1: cooldown_12-10_all.pdf  16 kB  Uploaded Fri Dec 17 12:30:22 2021  | Show | Show all
Attachment 2: cooldown_12-10_vs_11-16.pdf  17 kB  Uploaded Fri Dec 17 12:30:32 2021  | Show | Show all
ELOG V3.1.3-