The Simons Observatory: A large-diameter truss for a refracting telescope cooled to 1 K

Kevin D. Crowley, Peter Dow, Jordan E. Shroyer, John C. Groh, Bradley Dober, Jacob Spisak, Nicholas Galitzki, Tanay Bhandarkar, Mark J. Devlin, Simon Dicker, Patricio A. Gallardo, Kathleen Harrington, Jeffrey Iuliano, Bradley R. Johnson, Delwin Johnson, Anna M. Kofman, Akito Kusaka, Adrian Lee, Michele Limon, Federico NatiJohn Orlowski-Scherer, Lyman Page, Michael Randall, Grant Teply, Tran Tsan, Edward J. Wollack, Zhilei Xu, Ningfeng Zhu

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


We present the design and measured performance of a new carbon fiber strut design that is used in a cryogenically cooled truss for the Simons Observatory small aperture telescope. The truss consists of two aluminum 6061 rings separated by 24 struts. Each strut consists of a central carbon fiber tube fitted with two aluminum end caps. We tested the performance of the strut and truss by (i) cryogenically cycling and destructively pull-Testing strut samples, (ii) non-destructively pull-Testing the final truss, and (iii) measuring the thermal conductivity of the carbon fiber tubes. We found that the strut strength is limited by the mounting fasteners and the strut end caps, not the epoxy adhesive or the carbon fiber tube. This result is consistent with our numerical predictions. Our thermal measurements suggest that the conductive heat load through the struts (from 4 to 1 K) will be less than 1 mW. This strut design may be a promising candidate for use in other cryogenic support structures.

Original languageEnglish (US)
Article number055106
JournalReview of Scientific Instruments
Issue number5
StatePublished - May 1 2022

All Science Journal Classification (ASJC) codes

  • Instrumentation


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