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Unmeasured MC-stage loading with LPE filter and focal-plane assembly installed

Ascertain the net thermal loading on the Bluefors SD-400 dilution refrigerator mixing chamber (100 mK) stage of SAT-MF1 during cooldown when the 6.2 cm^-1 metal-mesh low-pass-edge filter at the mixing chamber stage and the fully populated focal-plane assembly (seven universal focal-plane modules) are installed, by isolating and quantifying the optical, conductive, and electrical contributions.

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Background

The authors established baseline DR load curves and measured loading contributions from individual subsystems. However, later DR issues limited their ability to extract reliable loading when the mixing chamber stage low-pass-edge filter and the full focal-plane assembly were present.

This leaves an unresolved measurement needed to complete the thermal budget with the final optical and detector configuration at the coldest stage.

References

Due to several issues with the DR system later in the testing program, we were unable to extract reliable loading for cooldowns that had the MC stage LPE filter and FPA installed.

— The Simons Observatory: Design, integration, and testing of the small aperture telescopes (2405.05550 - Galitzki et al., 9 May 2024) in Section “Validation of the DR and DR stages” (Table: Still and MC Stage Thermal Performance)