Showing papers by "K. L. Thompson published in 2012"

Second Season QUIET Observations: Measurements of the CMB Polarization Power Spectrum at 95 GHz

Abstract: The Q/U Imaging ExperimenT (QUIET) has observed the cosmic microwave background (CMB) at 43 and 95GHz The 43-GHz results have been published in QUIET Collaboration et al (2011), and here we report the measurement of CMB polarization power spectra using the 95-GHz data This data set comprises 5337 hours of observations recorded by an array of 84 polarized coherent receivers with a total array sensitivity of 87 uK sqrt(s) Four low-foreground fields were observed, covering a total of ~1000 square degrees with an effective angular resolution of 128', allowing for constraints on primordial gravitational waves and high-signal-to-noise measurements of the E-modes across three acoustic peaks The data reduction was performed using two independent analysis pipelines, one based on a pseudo-Cl (PCL) cross-correlation approach, and the other on a maximum-likelihood (ML) approach All data selection criteria and filters were modified until a predefined set of null tests had been satisfied before inspecting any non-null power spectrum The results derived by the two pipelines are in good agreement We characterize the EE, EB and BB power spectra between l=25 and 975 and find that the EE spectrum is consistent with LCDM, while the BB power spectrum is consistent with zero Based on these measurements, we constrain the tensor-to-scalar ratio to r=11+09-08 (r<28 at 95% CL) as derived by the ML pipeline, and r=12+09-08 (r<27 at 95% CL) as derived by the PCL pipeline In one of the fields, we find a correlation with the dust component of the Planck Sky Model, though the corresponding excess power is small compared to statistical errors Finally, we derive limits on all known systematic errors, and demonstrate that these correspond to a tensor-to-scalar ratio smaller than r=001, the lowest level yet reported in the literature

SECOND SEASON QUIET OBSERVATIONS: MEASUREMENTS OF THE COSMIC MICROWAVE BACKGROUND POLARIZATION POWER SPECTRUM AT 95 GHz

Abstract: The Q/U Imaging ExperimenT (QUIET) has observed the cosmic microwave background (CMB) at 43 and 95 GHz. The 43 GHz results have been published in a previous paper, and here we report the measurement of CMB polarization power spectra using the 95 GHz data. This data set comprises 5337 hr of observations recorded by an array of 84 polarized coherent receivers with a total array sensitivity of 87 μK√s. Four low-foreground fields were observed, covering a total of ~1000 deg^2 with an effective angular resolution of 12'.8, allowing for constraints on primordial gravitational waves and high signal-to-noise measurements of the E-modes across three acoustic peaks. The data reduction was performed using two independent analysis pipelines, one based on a pseudo-C_l (PCL) cross-correlation approach, and the other on a maximum-likelihood (ML) approach. All data selection criteria and filters were modified until a predefined set of null tests had been satisfied before inspecting any non-null power spectrum. The results derived by the two pipelines are in good agreement. We characterize the EE, EB, and BB power spectra between l = 25 and 975 and find that the EE spectrum is consistent with ΛCDM, while the BB power spectrum is consistent with zero. Based on these measurements, we constrain the tensor-to-scalar ratio to r = 1.1^(+0.9)_(–0.8) (r < 2.8 at 95% C.L.) as derived by the ML pipeline, and r = 1.2^(+0.9)_(–0.8) (r < 2.7 at 95% C.L.) as derived by the PCL pipeline. In one of the fields, we find a correlation with the dust component of the Planck Sky Model, though the corresponding excess power is small compared to statistical errors. Finally, we derive limits on all known systematic errors, and demonstrate that these correspond to a tensor-to-scalar ratio smaller than r = 0.01, the lowest level yet reported in the literature.

The QUIET Instrument

Abstract: The Q/U Imaging ExperimenT (QUIET) is designed to measure polarization in the Cosmic Microwave Background, targeting the imprint of inflationary gravitational waves at large angular scales (~ 1 degree). Between 2008 October and 2010 December, two independent receiver arrays were deployed sequentially on a 1.4 m side-fed Dragonian telescope. The polarimeters which form the focal planes use a highly compact design based on High Electron Mobility Transistors (HEMTs) that provides simultaneous measurements of the Stokes parameters Q, U, and I in a single module. The 17-element Q-band polarimeter array, with a central frequency of 43.1 GHz, has the best sensitivity (69 uK sqrt(s)) and the lowest instrumental systematic errors ever achieved in this band, contributing to the tensor-to-scalar ratio at r < 0.1. The 84-element W-band polarimeter array has a sensitivity of 87 uK sqrt(s) at a central frequency of 94.5 GHz. It has the lowest systematic errors to date, contributing at r < 0.01. The two arrays together cover multipoles in the range l= 25-975. These are the largest HEMT-based arrays deployed to date. This article describes the design, calibration, performance of, and sources of systematic error for the instrument.

The Keck Array: A Multi Camera CMB Polarimeter at the South Pole

Abstract: The Keck array is a new multi-camera Cosmic Microwave Background (CMB) polarimeter. Each camera contains 256 polarization pairs of antenna-coupled transition edge sensor (TES) bolometers. We recently deployed three of five cameras at the geographic South Pole, and plan to deploy the final two cameras in early 2012. This new telescope is an ideal instrument to search for the primordial B-mode polarization signal imprinted in the CMB by inflationary gravitational waves. We will discuss the design of the detectors and receivers, the status of current observations, and report on progress toward upgrading the instrument with the full compliment of polarized receivers.