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arXiv · 2608.20236

SPT-3G+: A Cosmic Microwave Background Experiment for the South Pole Telescope

T. Natoli·Z. Ahmed·H. Athreya·J. E. Austermann·K. Bae·A. Bapat·D. R. Barron·P. S. Barry·A. N. Bender·B. A. Benson·L. E. Bleem·J. E. Carlstrom·T. W. Cecil·C. L. Chang·S. Cisneros·A. Coerver·J. Cornelison·T. M. Crawford·R. Datta·K. R. Dibert·W. Dominguez·S. M. Duff·K. Fichman·J. P. Filippini·L. Gades·P. A. Gallardo·S. Galli·N. W. Halverson·Q. Hao·S. Henderson·R. Herbst·W. L. Holzapfel·A. Hryciuk·J. Hubmayr·D. Jones·V. Kabra·K. S. Karkare·C. King·M. A. Koc·A. M. Kofman·R. A. Lew·M. J. Link·T. J. Lucas·A. Mangu·E. S. Martsen·J. J. McMahon·J. Montgomery·J. M. Nagy·H. Nguyen·V. Novosad·S. Padin·T. Pinsonneault-Marotte·S. Raghunathan·A. S. Rahlin·C. L. Reichardt·L. Ruckman·J. E. Ruhl·M. S. Sarwar·S. Simon·R. Singh·J. A. Sobrin·A. A. Stark·Q. Taylor·C. Tucker·J. Ullom·J. Van Lanen·J. D. Vieira·A. G. Vieregg·M. R. Vissers·G. Wang·W. L. K. Wu·V. Yefremenko·E. Yilmaz·C. Yu·J. Zivick
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Abstract

SPT-3G+ is the next survey receiver planned to be installed in early 2029 on the 10-meter South Pole Telescope (SPT). This new receiver will feature 6,020 polarization-sensitive dichroic pixels with transition-edge sensors observing in frequency bands centered at 90 GHz and 150 GHz. The 24,080 detectors in the SPT-3G+ receiver will be cooled to 100 mK by a dilution refrigerator and read out using microwave SQUID multiplexing. The optical design of the receiver enables a 4 degree diameter field of view, which is broken up into 14 individual optics tubes each containing cryogenic alumina, silicon, and nylon lenses. These technology choices will allow the SPT-3G+ receiver to improve on the mapping speed of the currently operating SPT-3G receiver by nearly an order of magnitude. Once deployed, the SPT-3G+ receiver will observe for 6-years an area overlapping with the BICEP survey to achieve a combined (90 GHz and 150 GHz) CMB map depth of 0.5 uK-arcmin. Data from these observations will be used to create unprecedentedly deep CMB lensing maps, discover new galaxy clusters, and detect astrophysical transients. The lensing map produced by SPT-3G+ will be used to remove or "delens" foreground B modes, where large-scale structure gravitationally lenses the CMB and converts E modes into B-mode polarization, with the goal of revealing inflationary B modes. Together with data from the BICEP Array as part of the South Pole Observatory, SPT-3G+ data will be used to constrain the tensor-to-scalar ratio $r$ with a goal of achieving a measurement of $\sigma(r) = 0.001$

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T. Natoli, Z. Ahmed, H. Athreya, J. E. Austermann, K. Bae, A. Bapat, D. R. Barron, P. S. Barry, A. N. Bender, B. A. Benson, L. E. Bleem, J. E. Carlstrom, T. W. Cecil, C. L. Chang, S. Cisneros, A. Coerver, J. Cornelison, T. M. Crawford, R. Datta, K. R. Dibert, W. Dominguez, S. M. Duff, K. Fichman, J. P. Filippini, L. Gades, P. A. Gallardo, S. Galli, N. W. Halverson, Q. Hao, S. Henderson, R. Herbst, W. L. Holzapfel, A. Hryciuk, J. Hubmayr, D. Jones, V. Kabra, K. S. Karkare, C. King, M. A. Koc, A. M. Kofman, R. A. Lew, M. J. Link, T. J. Lucas, A. Mangu, E. S. Martsen, J. J. McMahon, J. Montgomery, J. M. Nagy, H. Nguyen, V. Novosad, S. Padin, T. Pinsonneault-Marotte, S. Raghunathan, A. S. Rahlin, C. L. Reichardt, L. Ruckman, J. E. Ruhl, M. S. Sarwar, S. Simon, R. Singh, J. A. Sobrin, A. A. Stark, Q. Taylor, C. Tucker, J. Ullom, J. Van Lanen, J. D. Vieira, A. G. Vieregg, M. R. Vissers, G. Wang, W. L. K. Wu, V. Yefremenko, E. Yilmaz, C. Yu, J. Zivick. 2026-08-20. SPT-3G+: A Cosmic Microwave Background Experiment for the South Pole Telescope. https://arxiv.org/abs/2608.20236

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