Design and assembly of SPT-3G cold readout hardware

• Published in: Journal of Low Temperature Physics
• Main Authors: Avva, J. S., Ade, Peter A. R., Ahmed, Z., Anderson, A. J., Austermann, J. E., Thakur, R. Basu, Barron, D., Bender, A. N., Benson, B. A., Carlstrom, J. E., Carter, F. W., Cecil, T., Chang, C. L., Cliche, J. F., Cukierman, A., Denison, E. V., de Haan, T., Ding, J., Dobbs, M. A., Dutcher, D., Elleflot, T., Everett, W., Foster, A., Gannon, R. N., Gilbert, A., Groh, J. C., Halverson, N. W., Harke-Hosemann, A. H., Harrington, N. L., Hasegawa, M., Hattori, K., Henning, J. W., Hilton, G. C., Holzapfel, W. L., Hori, Y., Huang, N., Irwin, K. D., Jeong, O. B., Jonas, M., Khaire, T., Kofman, A. M., Korman, M., Kubik, D., Kuhlmann, S., Kuo, C. L., Lee, A. T., Lowitz, A. E., Meyer, S. S., Montgomery, J., Nadolski, A.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer 2018
• Subjects: Austral; South Pole; South pole
• Online Access: https://orca.cardiff.ac.uk/id/eprint/113459/; https://doi.org/10.1007/s10909-018-1965-5; https://orca.cardiff.ac.uk/id/eprint/113459/1/JessicaAvvaJLTP2.pdf

The third-generation upgrade to the receiver on the South Pole Telescope, SPT-3G, was installed at the South Pole during the 2016–2017 austral summer to measure the polarization of the cosmic microwave background. Increasing the number of detectors by a factor of 10 to ∼16,000 ∼16,000 required the multiplexing factor to increase to 68 and the bandwidth of the frequency-division readout electronics to span 1.6–5.2 MHz. This increase necessitates low-thermal conductance, low-inductance cryogenic wiring. Our cold readout system consists of planar thin-film aluminum inductive–capacitive resonators, wired in series with the detectors, summed together, and connected to 4K SQUIDs by 10−μm 10−μm -thick niobium–titanium (NbTi) broadside-coupled striplines. Here, we present an overview of the cold readout electronics for SPT-3G, including assembly details and characterization of electrical and thermal properties of the system. We report, for the NbTi striplines, values of R≤10 −4 Ω R≤10−4Ω , L=21±1 nH L=21±1 nH , and C=1.47±.02 nF C=1.47±.02 nF . Additionally, the striplines’ thermal conductivity is described by kA=6.0±0.3 T 0.92±0.04 μW mm K −1 kA=6.0±0.3 T0.92±0.04 μW mm K−1 . Finally, we provide projections for cross talk induced by parasitic impedances from the stripline and find that the median value of percentage cross talk from leakage current is 0.22 and 0.09% 0.09% from wiring impedance.