Design and Validation of a Generalized Cooldown Simulation Tool for Cryogenic Millimeter-Wave Telescopes

Modern, large-format cryogenic cameras for mm-wave and sub-mm cosmology, including CMB experiments, require multi-stage cryogenic systems for sensitive detector operation. As these cameras increase in size, cooldown time can become prohibitively long. To address this and allow for valuable comparative studies early in the design process, we developed a thermal simulation tool to predict cooldown timelines and heat flows. Our model is flexible to various geometries and does not rely on final-stage design. Unlike previous cryogenic thermal network models, it incorporates thermal loading through the mm-transparent window and its associated infrared filters. We validate our tool against published cooldown thermometer data from a pulse-tube cooled ground-based CMB telescope, replicating the overall cooldown duration to ~25% accuracy and reproducing most qualitative features of the cooldown profile. We plan to release the code publicly for general use.