K. G. Megerian

Improved Constraints on Cosmology and Foregrounds from BICEP2 and Keck Array Cosmic Microwave Background Data with Inclusion of 95 GHz Band

We present results from an analysis of all data taken by the BICEP2 and Keck Array cosmic microwave background (CMB) polarization experiments up to and including the 2014 observing season. This includes the first Keck Array observations at 95 GHz. The maps reach a depth of 50 nK deg in Stokes Q and U in the 150 GHz band and 127 nK deg in the 95 GHz band. We take auto- and cross-spectra between these maps and publicly available maps from WMAP and Planck at frequencies from 23 to 353 GHz. An excess over lensed ΛCDM is detected at modest significance in the 95×150 BB spectrum, and is consistent with the dust contribution expected from our previous work. No significant evidence for synchrotron emission is found in spectra such as 23×95, or for correlation between the dust and synchrotron sky patterns in spectra such as 23×353. We take the likelihood of all the spectra for a multicomponent model including lensed ΛCDM, dust, synchrotron, and a possible contribution from inflationary gravitational waves (as parametrized by the tensor-to-scalar ratio r) using priors on the frequency spectral behaviors of dust and synchrotron emission from previous analyses of WMAP and Planck data in other regions of the sky. This analysis yields an upper limit r_{0.05}<0.09 at 95% confidence, which is robust to variations explored in analysis and priors. Combining these B-mode results with the (more model-dependent) constraints from Planck analysis of CMB temperature plus baryon acoustic oscillations and other data yields a combined limit r_{0.05}<0.07 at 95% confidence. These are the strongest constraints to date on inflationary gravitational waves.Keck Array and BICEP2 Collaborations: P. A. R. Ade, Z. Ahmed, 3 R. W. Aikin, K. D. Alexander, D. Barkats, S. J. Benton, C. A. Bischoff, J. J. Bock, 7 R. Bowens-Rubin, J. A. Brevik, I. Buder, E. Bullock, V. Buza, 9 J. Connors, B. P. Crill, L. Duband, C. Dvorkin, J. P. Filippini, 11 S. Fliescher, J. Grayson, M. Halpern, S. Harrison, G. C. Hilton, H. Hui, K. D. Irwin, 2, 14 K. S. Karkare, E. Karpel, J. P. Kaufman, B. G. Keating, S. Kefeli, S. A. Kernasovskiy, J. M. Kovac, 9, ∗ C. L. Kuo, 2 E. M. Leitch, M. Lueker, K. G. Megerian, C. B. Netterfield, 17 H. T. Nguyen, R. O’Brient, 7 R. W. Ogburn IV, 2 A. Orlando, 15 C. Pryke, 8, † S. Richter, R. Schwarz, C. D. Sheehy, 16 Z. K. Staniszewski, 7 B. Steinbach, R. V. Sudiwala, G. P. Teply, 15 K. L. Thompson, 2 J. E. Tolan, C. Tucker, A. D. Turner, A. G. Vieregg, 18, 16 A. C. Weber, D. V. Wiebe, J. Willmert, C. L. Wong, 9 W. L. K. Wu, and K. W. Yoon 2 School of Physics and Astronomy, Cardiff University, Cardiff, CF24 3AA, United Kingdom Kavli Institute for Particle Astrophysics and Cosmology, SLAC National Accelerator Laboratory, 2575 Sand Hill Rd, Menlo Park, California 94025, USA Department of Physics, Stanford University, Stanford, California 94305, USA Department of Physics, California Institute of Technology, Pasadena, California 91125, USA Harvard-Smithsonian Center for Astrophysics, 60 Garden Street MS 42, Cambridge, Massachusetts 02138, USA Department of Physics, University of Toronto, Toronto, Ontario, M5S 1A7, Canada Jet Propulsion Laboratory, Pasadena, California 91109, USA Minnesota Institute for Astrophysics, University of Minnesota, Minneapolis, Minnesota 55455, USA Department of Physics, Harvard University, Cambridge, MA 02138, USA Service des Basses Températures, Commissariat à l’Energie Atomique, 38054 Grenoble, France Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, V6T 1Z1, Canada National Institute of Standards and Technology, Boulder, Colorado 80305, USA Department of Physics, University of California at San Diego, La Jolla, California 92093, USA Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637, USA Canadian Institute for Advanced Research, Toronto, Ontario, M5G 1Z8, Canada Department of Physics, Enrico Fermi Institute, University of Chicago, Chicago, IL 60637, USA (Published in PRL 20 January 2016)

BICEP2 / Keck Array V: Measurements of B-mode polarization at degree angular scales and 150 GHz by the Keck Array

The Keck Array is a system of cosmic microwave background polarimeters, each similar to the Bicep2 experiment. In this paper we report results from the 2012 to 2013 observing seasons, during which the Keck Array consisted of five receivers all operating in the same (150 GHz) frequency band and observing field as Bicep2. We again find an excess of B-mode power over the lensed-ΛCDM expectation of >5σ in the range 30 6σ.

Fabrication of Nb/Al-N/sub x//NbTiN junctions for SIS mixer applications

We discuss fabrication and characteristics of superconductor-insulator-superconductor (SIS) junctions which typically exhibit a 3.5 mV sum-gap voltage. Junctions have a sub-gap to normal state resistance ratio of R/sub SG//R/sub N/=27 for resistance-area products down to R/sub N/A=8 /spl Omega/ /spl mu/m/sup 2/ and high quality junctions have been produced with RNA products as low as 4 /spl Omega/ /spl mu/m/sup 2/. The device structure incorporates a Nb base electrode, a tunnel barrier formed by plasma nitridation of a thin Al proximity layer, and a NbTiN counter-electrode. Results for all Nb junctions with high current density aluminum-nitride barriers are also shown. Nitridation of the aluminum layer is investigated by control of the dc floating potential on a separate rf driven electrode in the vacuum process chamber. Devices are integrated to a mixer antenna structure incorporating NbTiN as a ground plane. The wire circuit layer can be either normal metal or NbTiN. Annealing results show improved I-V characteristics with increased RNA products. Recent receiver measurements employing these junctions exhibit low noise performance up to 900 GHz.

BICEP2/Keck Array. IV. Optical Characterization and Performance of the BICEP2 and Keck Array Experiments

bicep2 and the Keck Array are polarization-sensitive microwave telescopes that observe the cosmic microwave background (CMB) from the South Pole at degree angular scales in search of a signature of inflation imprinted as B-mode polarization in the CMB. bicep2 was deployed in late 2009, observed for three years until the end of 2012 at 150 GHz with 512 antenna-coupled transition edge sensor bolometers, and has reported a detection of B-mode polarization on degree angular scales. The Keck Array was first deployed in late 2010 and will observe through 2016 with five receivers at several frequencies (95, 150, and 220 GHz). bicep2 and the Keck Array share a common optical design and employ the field-proven bicep1 strategy of using small-aperture, cold, on-axis refractive optics, providing excellent control of systematics while maintaining a large field of view. This design allows for full characterization of far-field optical performance using microwave sources on the ground. Here we describe the optical design of both instruments and report a full characterization of the optical performance and beams of bicep2 and the Keck Array at 150 GHz.

Antenna-coupled TES bolometers used in BICEP2, Keck Array, and SPIDER

We have developed antenna-coupled transition-edge sensor bolometers for a wide range of cosmic microwave background (CMB) polarimetry experiments, including Bicep2, Keck Array, and the balloon borne Spider. These detectors have reached maturity and this paper reports on their design principles, overall performance, and key challenges associated with design and production. Our detector arrays repeatedly produce spectral bands with 20%–30% bandwidth at 95, 150, or 230 GHz. The integrated antenna arrays synthesize symmetric co-aligned beams with controlled side-lobe levels. Cross-polarized response on boresight is typically

Pre-flight integration and characterization of the SPIDER balloon-borne telescope

\sim 0.5\%

In situ characterization of vertically oriented carbon nanofibers for three-dimensional nano-electro-mechanical device applications

, consistent with cross-talk in our multiplexed readout system. End-to-end optical efficiencies in our cameras are routinely 35% or higher, with per detector sensitivities of NET ~ 300

Antenna-coupled TES bolometers for the Keck array, Spider, and Polar-1

\mu {{\rm{K}}}_{\mathrm{CMB}}\sqrt{{\rm{s}}}

Performance of the NbTiN hot electron bolometer mixer with AlN buffer layer at terahertz frequency range

. Thanks to the scalability of this design, we have deployed 2560 detectors as 1280 matched pairs in Keck Array with a combined instantaneous sensitivity of

Single, aligned carbon nanotubes in 3D nanoscale architectures enabled by top-down and bottom-up manufacturable processes

\sim 9\;\mu {{\rm{K}}}_{\mathrm{CMB}}\sqrt{{\rm{s}}}