Design and Assembly of SPT-3G Cold Readout Hardware

• Published in: Journal of low temperature physics 2018-05, Vol.193 (3-4)
• Main Authors: Avva, J. S., Ade, P. 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., Natoli, T., Nguyen, H., Nishino, H., Noble, G. I., Novosad, V., Padin, S., Pan, Z., Pearson, J., Posada, C. M., Rahlin, A., Rotermund, K., Ruhl, J. E., Saunders, L. J., Sayre, J. T., Shirley, I., Shirokoff, E., Smecher, G., Sobrin, J. A., Stark, A. A., Story, K. T., Suzuki, A., Tang, Q. Y., Thompson, K. L., Tucker, C., Vale, L. R., Vanderlinde, K., Vieira, J. D., Wang, G., Whitehorn, N., Yefremenko, V., Yoon, K. W., Young, M. R.
• Format: Article
• Language: English
• Subjects: ASTRONOMY AND ASTROPHYSICS; Cosmic microwave background; Frequency-division multiplexing; SPT-3G
• ISSN: 0022-2291

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 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 -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≤10-4Ω , L=21±1 nH , and C=1.47±.02 nF . Additionally, the striplines’ thermal conductivity is described by 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% from wiring impedance.