Thermal conductance measurements of bolted copper joints for SuperCDMS

• Joint thermal conductance across bolted copper to copper connections has been tested from 60 mK to 26 K.
• Surfaces passivated with citric acid were tested as an alternative to gold plating.
• Results of joint thermal conductance testing are well fitted with a power law regression.
• These results correlate well with data obtained from a literature survey.

Joint thermal conductance testing has been undertaken for bolted copper to copper connections from 60 mK to 26 K. This testing was performed to validate an initial design basis for the SuperCDMS experiment, where a dilution refrigerator will be coupled to a cryostat via multiple bolted connections. Copper used during testing was either gold plated or passivated with citric acid to prevent surface oxidation. Results obtained are well fit by a power law regression of joint thermal conductance to temperature and match well with data collected during a literature review.