Avva, J.; Ade, P.; Ahmed, Z. ; Anderson, A. J.; Austermann, J.; Basu Thakur, R.; Barron, D.; Bender, A.; Benson, B.; Carlstrom, J.; Carter, F.; Cecil, T.; Chang, C.; Ding, J.; Gannon, R.; Harke-Hosemann, A.; Khaire, T.; Kuhlmann, S.; Novosad, V.; Pearson, J.; Posada, C.; Saunders, L.; Wang, G.; Yefremenko, V.
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- mu m- thick niobium- titanium ( NbTi) broadsidecoupled 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 L = 21 +/- 1 nH, and C = 1.47 +/-. 02 nF. Additionally, the striplines’ thermal conductivity is described by kA = 6.0 +/- 0.3 T 0.92 +/- 0.04 mu W 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.