Thermal conductance modeling and characterization of the SuperCDMS SNOLAB sub-Kelvin cryogenic system

• Published in: IOP conference series. Materials Science and Engineering Vol. 278; no. 1; pp. 12157 - 12164
• Main Authors: Dhuley, R C, Hollister, M I, Ruschman, M K, Martin, L D, Schmitt, R L, Tatkowski, G L, Bauer, D A, Lukens, P T
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.12.2017
• Subjects: Cryogenic equipment; Dark matter; Dilution; Heat transfer; Modelling; Room temperature; Stems; Straps; Thermal analysis; Thermal conductivity
• ISSN: 1757-8981; 1757-899X
• DOI: 10.1088/1757-899X/278/1/012157

The detectors of the Super Cryogenic Dark Matter Search experiment at SNOLAB (SuperCDMS SNOLAB) will operate in a seven-layered cryostat with thermal stages between room temperature and the base temperature of 15 mK. The inner three layers of the cryostat, which are to be nominally maintained at 1 K, 250 mK, and 15 mK, will be cooled by a dilution refrigerator via conduction through long copper stems. Bolted and mechanically pressed contacts, flat and cylindrical, as well as flexible straps are the essential stem components that will facilitate assembly/dismantling of the cryostat. These will also allow for thermal contractions/movements during cooldown of the sub-Kelvin system. To ensure that these components and their contacts meet their design thermal conductance, prototypes were fabricated and cryogenically tested. The present paper gives an overview of the SuperCDMS SNOLAB sub-Kelvin architecture and its conductance requirements. Results from the conductance measurements tests and from sub-Kelvin thermal modeling are discussed.