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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: 2695     Entry time: Fri Nov 12 14:31:38 2021     Reply to this: 2697   2701
Author: Stephen, Radhika 
Type: DailyProgress 
Category: Cryo vacuum chamber 
Subject: Radiative Cooling of Si Mass, with better shield emissivity 

In this phase, we are working toward improving our setup with a rigid copper bar, and obtaining a new data point for our radiative cooling thermal models for a suspended silicon mass. Since the past cooling runs of a silicon test mass did not yet incorporate aquadag-painted shields, we wanted to obtain a new data point in the model (in other words, we painted the shields in QIL/2645, but the next test was a PD measurement, so this is the first silicon test mass measurment after shields were painted). The improvement to the thermal linkage, now using a rigid copper bar with higher conductivity (ref. QIL/2666), is a second variable being changed simultaneously in the spirit of improving the cooldown time.

Refer to the prior post (QIL/2694) for the bulk of the blow-by-blow of configuring the chamber to use the rigid copper bar linkage. This post will describe the mounting of the Si mass, and the pump down and cool down.

  • The silicon mass with Aquadag barrel was dropped into the existing frame, with the previous wire arrangement and with no particular requirement on position or orientation (just best effort centering and leveling). Adjustments were done chamberside as access was easier.
  • The frame was lifted into the chamber, with the hanging mass supported by auxiliary fingers, and placed in an available area. Since conductive cooling was not a dominant mode of heat transfer in this setup (ref. QIL/2647), clamping to the baseplate was simply a single dog clamp on each foot of the frame.
  • The cigarette paper was cryovarnished to the surface in the bare central position. Once the cryovarnish was set, the RTD was cryovarnished to the cigarette paper pad. No  strain relief or thermal anchoring considerations were implemented. RTD continuity was verified.
  • Lids were bolted down and shields were finalized (avoiding shorting to copper bar, making sure foil drapes covering apertures were well positioned, etc.
  • Vacuum pumps on at ~3 pm, cryocooler on at 3:30 pm. At 4 pm, things are still looking good!

Closeout photos will be posted to the QIL Cryo Vacuum Chamber photo album.

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