On-Sky Performance of the SPT-3G Frequency-Domain Multiplexed Readout

• Published in: Journal of Low Temperature Physics
• Main Authors: Bender, A. N., Anderson, A. J., Avva, J. S., Ade, P. R., Ahmed, Z., Barry, P. S., Basu Thakur, R., Benson, B. A., Bryant, L., Byrum, K., Carlstrom, J. E., Carter, F. W., Cecil, T. W., Chang, C. L., Cho, H. -M., Cliche, J. F., Cukierman, A., de Haan, T., Denison, E. V., Ding, J., Dobbs, M. A., Dutcher, D., Everett, W., Ferguson, K. R., Foster, A., Fu, J., Gallicchio, J., Gambrel, A. E., Gardner, R. W., Gilbert, A., Groh, J. C., Guns, S., Guyser, R., Halverson, N. W., Harke-Hosemann, A. H., Harrington, N. L., Henning, J. W., Hilton, G. C., Holzapfel, W. L., Howe, D., Huang, N., Irwin, K. D., Jeong, O. B., Jonas, M., Jones, A., Khaire, T. S., Kofman, A. M., Korman, M., Kubik, D. L., Kuhlmann, S., Kuo, C. -L., Lee, A. T., Leitch, E. M., Lowitz, A. E., Meyer, S. S., Michalik, D., Montgomery, J., Nadolski, A., Natoli, T., Nguyen, H., Noble, G. I., Novosad, V., Padin, S., Pan, Z., Paschos, P., Pearson, J., Posada, C. M., Quan, W., Rahlin, A., Riebel, D., Ruhl, J. E., Sayre, J. T., Shirokoff, E., Smecher, G., Sobrin, J. A., Stark, A. A., Stephen, J., Story, K. T., Suzuki, A., 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.
• Language: unknown
• Published: 2023
• Subjects: 47 OTHER INSTRUMENTATION; South Pole; South pole
• Online Access: http://www.osti.gov/servlets/purl/1632820; https://www.osti.gov/biblio/1632820; https://doi.org/10.1007/s10909-019-02280-w

Frequency-domain multiplexing (fMux) is an established technique for the readout of large arrays of transition-edge sensor (TES) bolometers. Each TES in a multiplexing module has a unique AC voltage bias that is selected by a resonant filter. This scheme provides for the operation and readout of multiple bolometers on a single pair of wires, reducing thermal loading onto sub-Kelvin stages. The current receiver on the South Pole Telescope, SPT-3G, uses a 68x fMux system to operate its large-format camera of ~16,000 TES bolometers. We present here the successful implementation and performance of the SPT-3G readout as measured on-sky. Characterization of the noise reveals a median pair-differenced 1/f knee frequency of 33 mHz, indicating that low-frequency noise in the readout will not limit SPT-3G’s measurements of sky power on large angular scales. Measurements further show that the median readout white noise level in each of the SPT-3G observing bands is below the expectation for photon noise, demonstrating that SPT-3G is operating in the photon-noise-dominated regime.