Chao-Lin Kuo

All Publications

• SLAC microresonator RF (SMuRF) electronics: A tone-tracking readout system for superconducting microwave resonator arrays. The Review of scientific instruments Yu, C., Ahmed, Z., Frisch, J. C., Henderson, S. W., Silva-Feaver, M., Arnold, K., Brown, D., Connors, J., Cukierman, A. J., D'Ewart, J. M., Dober, B. J., Dusatko, J. E., Haller, G., Herbst, R., Hilton, G. C., Hubmayr, J., Irwin, K. D., Kuo, C., Mates, J. A., Ruckman, L., Ullom, J., Vale, L., Van Winkle, D. D., Vasquez, J., Young, E. 2023; 94 (1): 014712

  Abstract

  We describe the newest generation of the SLAC Microresonator RF (SMuRF) electronics, a warm digital control and readout system for microwave-frequency resonator-based cryogenic detector and multiplexer systems, such as microwave superconducting quantum interference device multiplexers (mumux) or microwave kinetic inductance detectors. Ultra-sensitive measurements in particle physics and astronomy increasingly rely on large arrays of cryogenic sensors, which in turn necessitate highly multiplexed readout and accompanying room-temperature electronics. Microwave-frequency resonators are a popular tool for cryogenic multiplexing, with the potential to multiplex thousands of detector channels on one readout line. The SMuRF system provides the capability for reading out up to 3328 channels across a 4-8GHz bandwidth. Notably, the SMuRF system is unique in its implementation of a closed-loop tone-tracking algorithm that minimizes RF power transmitted to the cold amplifier, substantially relaxing system linearity requirements and effective noise from intermodulation products. Here, we present a description of the hardware, firmware, and software systems of the SMuRF electronics, comparing achieved performance with science-driven design requirements. In particular, we focus on the case of large-channel-count, low-bandwidth applications, but the system has been easily reconfigured for high-bandwidth applications. The system described here has been successfully deployed in lab settings and field sites around the world and is baselined for use on upcoming large-scale observatories.

  View details for DOI 10.1063/5.0125084

  View details for PubMedID 36725567

• Current Status of the Ali CMB Polarization Telescope Focal Plane Camera IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY Salatino, M., Austermann, J., Meinke, J., Sinclair, A. K., Walker, S., Bai, X., Beall, J., Connors, J., Dober, B., Duff, S. M., Givhan, R. C., Hilton, G., Hubmayr, J., Karpel, E. D., Kuo, C., Mani, H., Mates, J. B., Mathewson, J., Mauskopf, P., Montana-Lopez, J. A., Stephenson, R., Thompson, K. L., Ullom, J., van Lanen, J., Yoon, K., Weeks, E. L., Wu, Y., Zhang, X. 2021; 31 (5)

  View details for DOI 10.1109/TASC.2021.3065289

  View details for Web of Science ID 000688423500002

• Symmetrically tuned large-volume conic shell-cavities for axion searches Journal of Cosmology and Astroparticle Physics Kuo, C. 2021; February (02)

  View details for DOI 10.1088/1475-7516/2021/02/018

• LiteBIRD satellite: JAXA's new strategic L-class mission for all-sky surveys of cosmic microwave background polarization Hazumi, M., Ade, P. A., Adler, A., Allys, E., Arnold, K., Auguste, D., Aumont, J., Aurlien, R., Austermann, J., Baccigalupi, C., Banday, A. J., Banjeri, R., Barreiro, R. B., Basak, S., Beall, J., Beck, D., Beckman, S., Bermejo, J., de Bernardis, P., Bersanelli, M., Bonis, J., Borrill, J., Boulanger, F., Bounissou, S., Brilenkov, M., Brown, M., Bucher, M., Calabrese, E., Campeti, P., Carones, A., Casas, F. J., Challinor, A., Chan, V., Cheung, K., Chinone, Y., Cliche, J. F., Colombo, L., Columbro, F., Cubas, J., Cukierman, A., Curtis, D., D'Alessandro, G., Dachlythra, N., De Petris, M., Dickinson, C., Diego-Palazuelos, P., Dobbs, M., Dotani, T., Duband, L., Duff, S., Duval, J. M., Ebisawa, K., Elleflot, T., Eriksen, H. K., Errard, J., Essinger-Hileman, T., Finelli, F., Flauger, R., Franceschet, C., Fuskeland, U., Galloway, M., Ganga, K., Gao, J. R., Genova-Santos, R., Gerbino, M., Gervasi, M., Ghigna, T., Gjerlw, E., Gradziel, M. L., Grain, J., Grupp, F., Gruppuso, A., Gudmundsson, J. E., de Haan, T., Halverson, N. W., Hargrave, P., Hasebe, T., Hasegawa, M., Hattori, M., Henrot-Versille, S., Herman, D., Herranz, D., Hill, C. A., Hilton, G., Hirota, Y., Hivon, E., Hlozek, R. A., Hoshino, Y., de la Hoz, E., Hubmayr, J., Ichiki, K., Iida, T., Imada, H., Ishimura, K., Ishino, H., Jaehnig, G., Kaga, T., Kashima, S., Katayama, N., Kato, A., Kawasaki, T., Keskitalo, R., Kisner, T., Kobayashi, Y., Kogiso, N., Kogut, A., Kohri, K., Komatsu, E., Komatsu, K., Konishi, K., Krachmalnicoff, N., Kreykenbohm, I., Kuo, C. L., Kushino, A., Lamagna, L., Lanen, J., Lattanzi, M., Lee, A. T., Leloup, C., Levrier, F., Linder, E., Louis, T., Luzzi, G., Maciaszek, T., Maffei, B., Maino, D., Maki, M., Mandelli, S., Martinez-Gonzalez, E., Masi, S., Matsumura, T., Mennella, A., Migliaccio, M., Minami, Y., Mitsuda, K., Montgomery, J., Montier, L., Morgante, G., Mot, B., Murata, Y., Murphy, J. A., Nagai, M., Nagano, Y., Nagasaki, T., Nagata, R., Nakamura, S., Namikawa, T., Natoli, P., Nerval, S., Nishibori, T., Nishino, H., Noviello, F., O'Sullivan, C., Ogawa, H., Ogawa, H., Oguri, S., Ohsaki, H., Ohta, I. S., Okada, N., Okada, N., Pagano, L., Paiella, A., Paoletti, D., Patanchon, G., Peloton, J., Piacentini, F., Pisano, G., Polenta, G., Poletti, D., Prouve, T., Puglisi, G., Rambaud, D., Raum, C., Realini, S., Reinecke, M., Remazeilles, M., Ritacco, A., Roudil, G., Rubino-Martin, J. A., Russell, M., Sakurai, H., Sakurai, Y., Sandri, M., Sasaki, M., Savini, G., Scott, D., Seibert, J., Sekimoto, Y., Sherwin, B., Shinozaki, K., Shiraishi, M., Shirron, P., Signorelli, G., Smecher, G., Stever, S., Stompor, R., Sugai, H., Sugiyama, S., Suzuki, A., Suzuki, J., Svalheim, T. L., Switzer, E., Takaku, R., Takakura, H., Takakura, S., Takase, Y., Takeda, Y., Tartari, A., Taylor, E., Terao, Y., Thommesen, H., Thompson, K. L., Ben Thorne, Toda, T., Tomasi, M., Tominaga, M., Trappe, N., Tristram, M., Tsuji, M., Tsujimoto, M., Tucker, C., Ullom, J., Vermeulen, G., Vielva, P., Villa, F., Vissers, M., Vittorio, N., Wehus, I., Weller, J., Westbrook, B., Wilms, J., Winter, B., Wollack, E. J., Yamasaki, N. Y., Yoshida, T., Yumoto, J., Zannoni, M., Zonca, A., Lystrup, M., Perrin, M. D., Batalha, N., Siegler, N., Tong, E. C. SPIE-INT SOC OPTICAL ENGINEERING. 2021

  View details for DOI 10.1117/12.2563050

  View details for Web of Science ID 000646193100036

• Large-volume centimeter-wave cavities for axion searches Journal of Cosmology and Astroparticle Physics Kuo, C. 2020

  View details for DOI 10.1088/1475-7516/2020/06/010

• Constraints on Primordial Gravitational Waves Using Planck, WMAP, and New BICEP2/Keck Observations through the 2015 Season PHYSICAL REVIEW LETTERS Ade, P. R., Ahmed, Z., Aikin, R. W., Alexander, K. D., Barkats, D., Benton, S. J., Bischoff, C. A., Bock, J. J., Bowens-Rubin, R., Brevik, J. A., Buder, I., Bullock, E., Buza, V., Connors, J., Cornelison, J., Crill, B. P., Crumrine, M., Dierickx, M., Duband, L., Dvorkin, C., Filippini, J. P., Fliescher, S., Grayson, J., Hall, G., Halpern, M., Harrison, S., Hildebrandt, S. R., Hilton, G. C., Hui, H., Irwin, K. D., Kang, J., Karkare, K. S., Karpel, E., Kaufman, J. P., Keating, B. G., Kefeli, S., Kernasovskiy, S. A., Kovac, J. M., Kuo, C. L., Larsen, N. A., Lau, K., Leitch, E. M., Lueker, M., Megerian, K. G., Moncelsi, L., Namikawa, T., Netterfield, C. B., Nguyen, H. T., O'Brient, R., Ogburn, R. W., Palladino, S., Pryke, C., Racine, B., Richter, S., Schillaci, A., Schwarz, R., Sheehy, C. D., Soliman, A., St Germaine, T., Staniszewski, Z. K., Steinbach, B., Sudiwala, R. V., Teply, G. P., Thompson, K. L., Tolan, J. E., Tucker, C., Turner, A. D., Umilta, C., Vieregg, A. G., Wandui, A., Weber, A. C., Wiebe, D. V., Willmert, J., Wong, C. L., Wu, W. K., Yang, H., Yoon, K. W., Zhang, C., Keck Array Collaboration, BICEP2 Collaboration 2018; 121 (22)

  View details for DOI 10.1103/PhysRevLett.121.221301

  View details for Web of Science ID 000451580700006

• Highly-multiplexed microwave SQUID readout using the SLAC Microresonator Radio Frequency (SMuRF) Electronics for Future CMB and Sub-millimeter Surveys Henderson, S. W., Ahmed, Z., Austermann, J., Becker, D., Bennett, D. A., Brown, D., Chaudhuri, S., Cho, H., D'Ewart, J. M., Dober, B., Duff, S. M., Dusatko, J. E., Fatigoni, S., Frisch, J. C., Gard, J. D., Halpern, M., Hilton, G. C., Hubmayr, J., Irwin, K. D., Karpel, E. D., Kernasovskiy, S. S., Kuenstner, S. E., Kuo, C., Li, D., Mates, J. B., Reintsema, C. D., Smith, S. R., Ullom, J., Vale, L. R., Van Winkle, D. D., Vissers, M., Yu, C., Zmuidzinas, J., Gao SPIE-INT SOC OPTICAL ENGINEERING. 2018

  View details for DOI 10.1117/12.2314435

  View details for Web of Science ID 000451719300023

• BICEP2 / Keck Array IX: New bounds on anisotropies of CMB polarization rotation and implications for axionlike particles and primordial magnetic fields PHYSICAL REVIEW D Ade, P. R., Ahmed, Z., Aikin, R. W., Alexander, K. D., Barkats, D., Benton, S. J., Bischoff, C. A., Bock, J. J., Bowens-Rubin, R., Brevik, J. A., Buder, I., Bullock, E., Buza, V., Connors, J., Crill, B. P., Duband, L., Dvorkin, C., Filippini, J. P., Fliescher, S., Germaine, T., Ghosh, T., Grayson, J., Harrison, S., Hildebrandt, S. R., Hilton, G. C., Hui, H., Irwin, K. D., Kang, J., Karkare, K. S., Karpel, E., Kaufman, J. P., Keating, B. G., Kefeli, S., Kernasovskiy, S. A., Kovac, J. M., Kuo, C. L., Larson, N., Leitch, E. M., Megerian, K. G., Moncelsi, L., Namikawa, T., Netterfield, C. B., Nguyen, H. T., O'Brient, R., Ogburn, R. W., Pryke, C., Richter, S., Schillaci, A., Schwarz, R., Sheehy, C. D., Staniszewski, Z. K., Steinbach, B., Sudiwala, R. V., Teply, G. P., Thompson, K. L., Tolan, J. E., Tucker, C., Turner, A. D., Vieregg, A. G., Weber, A. C., Wiebe, D. V., Willmert, J., Wong, C. L., Wu, W. K., Yoon, K. W. 2017; 96 (10)

  View details for DOI 10.1103/PhysRevD.96.102003

  View details for Web of Science ID 000414740300001

• BICEP2/KECK ARRAY VIII: MEASUREMENT OF GRAVITATIONAL LENSING FROM LARGE-SCALE B-MODE POLARIZATION ASTROPHYSICAL JOURNAL Ade, P. A., Ahmed, Z., Aikin, R. W., Alexander, K. D., Barkats, D., Benton, S. J., BISCHOFF, C. A., Bock, J. J., Bowens-Rubin, R., Brevik, J. A., Buder, I., Bullock, E., Buza, V., Connors, J., Crill, B. P., Duband, L., Dyorkin, C., Filippini, J. P., Fliescher, S., GRAYSON, J., Halpern, M., Harrison, S., Hildebrandt, S. R., Hilton, G. C., Hui, H., Irwin, K. D., Kang, J., Karkare, K. S., Karpel, E., Kaufman, J. P., Keating, B. G., Kefeli, S., Kernasoyskiy, S. A., Kovac, J. M., Kuo, C. L., Leitch, E. M., Lueker, M., Megerian, K. G., Namikawa, T., Netterfield, C. B., Nguyen, H. T., O'Brient, R., Ogburn, R. W., Orlando, A., Pryke, C., Richter, S., Schwarz, R., Sheehy, C. D., Staniszewski, Z. K., Steinbach, B., Sudiwala, R. V., Teply, G. P., Thompson, K. L., Tolan, J. E., Tucker, C., Turner, A. D., Vieregg, A. G., Weber, A. C., Wiebe, D. V., WILLMERT, J., Wong, C. L., Wu, W. L., Yoon, K. W. 2016; 833 (2)

  View details for DOI 10.3847/1538-4357/833/2/228

  View details for Web of Science ID 000391169600103

• BICEP2/KECK ARRAY. VII. MATRIX BASED E/B SEPARATION APPLIED TO BICEP2 AND THE KECK ARRAY ASTROPHYSICAL JOURNAL Ade, P. A., Ahmed, Z., Aikin, R. W., Alexander, K. D., Barkats, D., Benton, S. J., BISCHOFF, C. A., Bock, J. J., Bowens-Rubin, R., Brevik, J. A., Buder, I., Bullock, E., Buza, V., Connors, J., Crill, B. P., Duband, L., Dvorkin, C., Filippini, J. P., Fliescher, S., GRAYSON, J., Halpern, M., Harrison, S., Hildebrandt, S. R., Hilton, G. C., Hui, H., Irwin, K. D., Kang, J., Karkare, K. S., Karpel, E., Kaufman, J. P., Keating, B. G., Kefeli, S., Kernasovskiy, S. A., Kovac, J. M., Kuo, C. L., Leitch, E. M., Lueker, M., Megerian, K. G., Namikawa, T., Netterfield, C. B., Nguyen, H. T., O'Brient, R., Ogburn, R. W., Orlando, A., Pryke, C., Richter, S., Schwarz, R., Sheehy, C. D., Staniszewski, Z. K., Steinbach, B., Sudiwala, R. V., Teply, G. P., Thompson, K. L., Tolan, J. E., Tucker, C., Turner, A. D., Vieregg, A. G., Weber, A. C., Wiebe, D. V., WILLMERT, J., Wong, C. L., Wu, W. L., Yoon, K. W. 2016; 825 (1)

  View details for DOI 10.3847/0004-637X/825/1/66

  View details for Web of Science ID 000381930000066

• Joint Analysis of BICEP2/Keck Array and Planck Data PHYSICAL REVIEW LETTERS Ade, P. A., Aghanim, N., Ahmed, Z., Aikin, R. W., Alexander, K. D., Arnaud, M., Aumont, J., Baccigalupi, C., Banday, A. J., Barkats, D., Barreiro, R. B., Bartlett, J. G., Bartolo, N., Battaner, E., Benabed, K., Benoit, A., Benoit-Levy, A., Benton, S. J., Bernard, J., Bersanelli, M., Bielewicz, P., BISCHOFF, C. A., Bock, J. J., Bonaldi, A., Bonavera, L., Bond, J. R., Borrill, J., Bouchet, F. R., Boulanger, F., Brevik, J. A., Bucher, M., Buder, I., Bullock, E., Burigana, C., Butler, R. C., Buza, V., Calabrese, E., Cardoso, J., Catalano, A., Challinor, A., Chary, R., Chiang, H. C., Christensen, P. R., Colombo, L. P., Combet, C., Connors, J., Couchot, F., Coulais, A., Crill, B. P., Curto, A., Cuttaia, F., Danese, L., Davies, R. D., Davis, R. J., de Bernardis, P., De Rosa, A., De Zotti, G., Delabrouille, J., Delouis, J., Desert, F., Dickinson, C., Diego, J. M., Dole, H., Donzelli, S., Dore, O., Douspis, M., Dowell, C. D., Duband, L., Ducout, A., Dunkley, J., Dupac, X., Dvorkin, C., Efstathiou, G., Elsner, F., Ensslin, T. A., Eriksen, H. K., Falgarone, E., Filippini, J. P., Finelli, F., Fliescher, S., Forni, O., Frailis, M., Fraisse, A. A., Franceschi, E., Frejsel, A., Galeotta, S., Galli, S., Ganga, K., Ghosh, T., Giard, M., Gjerlow, E., Golwala, S. R., Gonzalez-Nuevo, J., Gorski, K. M., Gratton, S., Gregorio, A., Gruppuso, A., Gudmundsson, J. E., Halpern, M., Hansen, F. K., Hanson, D., Harrison, D. L., Hasselfield, M., Helou, G., Henrot-Versille, S., Herranz, D., Hildebrandt, S. R., Hilton, G. C., Hivon, E., Hobson, M., Holmes, W. A., Hovest, W., Hristov, V. V., Huffenberger, K. M., Hui, H., Hurier, G., Irwin, K. D., Jaffe, A. H., JAFFE, T. R., Jewell, J., Jones, W. C., Juvela, M., Karakci, A., Karkare, K. S., Kaufman, J. P., Keating, B. G., Kefeli, S., Keihanen, E., Kernasovskiy, S. A., Keskitalo, R., Kisner, T. S., Kneissl, R., Knoche, J., Knox, L., Kovac, J. M., Krachmalnicoff, N., Kunz, M., Kuo, C. L., Kurki-Suonio, H., Lagache, G., Lahteenmaki, A., Lamarre, J., Lasenby, A., Lattanzi, M., Lawrence, C. R., Leitch, E. M., Leonardi, R., Levrier, F., Lewis, A., Liguori, M., Lilje, P. B., Linden-Vornle, M., Lopez-Caniego, M., LUBIN, P. M., Lueker, M., Macias-Perez, J. F., Maffei, B., Maino, D., Mandolesi, N., MANGILLI, A., Maris, M., Martin, P. G., Martinez-Gonzalez, E., Masi, S., Mason, P., Matarrese, S., Megerian, K. G., Meinhold, P. R., Melchiorri, A., Mendes, L., Mennella, A., Migliaccio, M., Mitra, S., Miville-Deschenes, M., Moneti, A., Montier, L., Morgante, G., Mortlock, D., Moss, A., Munshi, D., Murphy, J. A., Naselsky, P., Nati, F., Natoli, P., Netterfield, C. B., Nguyen, H. T., Norgaard-Nielsen, H. U., Noviello, F., Novikov, D., Novikov, I., O'Brient, R., Ogburn, R. W., Orlando, A., Pagano, L., Pajot, F., Paladini, R., Paoletti, D., Partridge, B., Pasian, F., Patanchon, G., Pearson, T. J., Perdereau, O., Perotto, L., Pettorino, V., Piacentini, F., Piat, M., Pietrobon, D., Plaszczynski, S., Pointecouteau, E., Polenta, G., Ponthieu, N., Pratt, G. W., Prunet, S., Pryke, C., Puget, J., Rachen, J. P., Reach, W. T., Rebolo, R., Reinecke, M., Remazeilles, M., Renault, C., Renzi, A., Richter, S., Ristorcelli, I., Rocha, G., Rossetti, M., ROUDIER, G., Rowan-Robinson, M., Rubino-Martin, J. A., Rusholme, B., Sandri, M., Santos, D., SAVELAINEN, M., Savini, G., Schwarz, R., Scott, D., Seiffert, M. D., Sheehy, C. D., SPENCER, L. D., Staniszewski, Z. K., Stolyarov, V., Sudiwala, R., Sunyaev, R., Sutton, D., Suur-Uski, A., Sygnet, J., Tauber, J. A., Teply, G. P., Terenzi, L., Thompson, K. L., Toffolatti, L., Tolan, J. E., Tomasi, M., Tristram, M., Tucci, M., Turner, A. D., Valenziano, L., Valiviita, J., Van Tent, B., Vibert, L., Vielva, P., Vieregg, A. G., Villa, F., Wade, L. A., Wandelt, B. D., Watson, R., Weber, A. C., Wehus, I. K., White, M., White, S. D., WILLMERT, J., Wong, C. L., Yoon, K. W., Yvon, D., Zacchei, A., Zonca, A. 2015; 114 (10)

  Abstract

  We report the results of a joint analysis of data from BICEP2/Keck Array and Planck. BICEP2 and Keck Array have observed the same approximately 400  deg^{2} patch of sky centered on RA 0 h, Dec. -57.5°. The combined maps reach a depth of 57 nK deg in Stokes Q and U in a band centered at 150 GHz. Planck has observed the full sky in polarization at seven frequencies from 30 to 353 GHz, but much less deeply in any given region (1.2  μK deg in Q and U at 143 GHz). We detect 150×353 cross-correlation in B modes at high significance. We fit the single- and cross-frequency power spectra at frequencies ≥150  GHz to a lensed-ΛCDM model that includes dust and a possible contribution from inflationary gravitational waves (as parametrized by the tensor-to-scalar ratio r), using a prior on the frequency spectral behavior of polarized dust emission from previous Planck analysis of other regions of the sky. We find strong evidence for dust and no statistically significant evidence for tensor modes. We probe various model variations and extensions, including adding a synchrotron component in combination with lower frequency data, and find that these make little difference to the r constraint. Finally, we present an alternative analysis which is similar to a map-based cleaning of the dust contribution, and show that this gives similar constraints. The final result is expressed as a likelihood curve for r, and yields an upper limit r_{0.05}<0.12 at 95% confidence. Marginalizing over dust and r, lensing B modes are detected at 7.0σ significance.

  View details for DOI 10.1103/PhysRevLett.114.101301

  View details for Web of Science ID 000350624500002

  View details for PubMedID 25815919

• Detection of B-Mode Polarization at Degree Angular Scales by BICEP2. Physical review letters Ade, P. A., Aikin, R. W., Barkats, D., Benton, S. J., BISCHOFF, C. A., Bock, J. J., Brevik, J. A., Buder, I., Bullock, E., Dowell, C. D., Duband, L., Filippini, J. P., Fliescher, S., Golwala, S. R., Halpern, M., Hasselfield, M., Hildebrandt, S. R., Hilton, G. C., Hristov, V. V., Irwin, K. D., Karkare, K. S., Kaufman, J. P., Keating, B. G., Kernasovskiy, S. A., Kovac, J. M., Kuo, C. L., Leitch, E. M., Lueker, M., Mason, P., Netterfield, C. B., Nguyen, H. T., O'Brient, R., Ogburn, R. W., Orlando, A., Pryke, C., Reintsema, C. D., Richter, S., Schwarz, R., Sheehy, C. D., Staniszewski, Z. K., Sudiwala, R. V., Teply, G. P., Tolan, J. E., Turner, A. D., Vieregg, A. G., Wong, C. L., Yoon, K. W. 2014; 112 (24): 241101-?

  Abstract

  We report results from the BICEP2 experiment, a cosmic microwave background (CMB) polarimeter specifically designed to search for the signal of inflationary gravitational waves in the B-mode power spectrum around ℓ∼80. The telescope comprised a 26 cm aperture all-cold refracting optical system equipped with a focal plane of 512 antenna coupled transition edge sensor 150 GHz bolometers each with temperature sensitivity of ≈300  μK(CMB)√s. BICEP2 observed from the South Pole for three seasons from 2010 to 2012. A low-foreground region of sky with an effective area of 380 square deg was observed to a depth of 87 nK deg in Stokes Q and U. In this paper we describe the observations, data reduction, maps, simulations, and results. We find an excess of B-mode power over the base lensed-ΛCDM expectation in the range 30 < ℓ < 150, inconsistent with the null hypothesis at a significance of >5σ. Through jackknife tests and simulations based on detailed calibration measurements we show that systematic contamination is much smaller than the observed excess. Cross correlating against WMAP 23 GHz maps we find that Galactic synchrotron makes a negligible contribution to the observed signal. We also examine a number of available models of polarized dust emission and find that at their default parameter values they predict power ∼(5-10)× smaller than the observed excess signal (with no significant cross-correlation with our maps). However, these models are not sufficiently constrained by external public data to exclude the possibility of dust emission bright enough to explain the entire excess signal. Cross correlating BICEP2 against 100 GHz maps from the BICEP1 experiment, the excess signal is confirmed with 3σ significance and its spectral index is found to be consistent with that of the CMB, disfavoring dust at 1.7σ. The observed B-mode power spectrum is well fit by a lensed-ΛCDM+tensor theoretical model with tensor-to-scalar ratio r = 0.20_(-0.05)(+0.07), with r = 0 disfavored at 7.0σ. Accounting for the contribution of foreground, dust will shift this value downward by an amount which will be better constrained with upcoming data sets.

  View details for PubMedID 24996078