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Araujo D.,Columbia University | Bischoff C.,University of Chicago | Bischoff C.,Harvard - Smithsonian Center for Astrophysics | Brizius A.,University of Chicago | And 63 more authors.
Astrophysical Journal | Year: 2012

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. Four low-foreground fields were observed, covering a total of 1000 deg2 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-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. © 2012. The American Astronomical Society. All rights reserved..


Bischoff C.,University of Chicago | Bischoff C.,Harvard - Smithsonian Center for Astrophysics | Brizius A.,University of Chicago | Brizius A.,Max Planck Institute for Radio Astronomy | And 58 more authors.
Astrophysical Journal | Year: 2011

The Q/U Imaging ExperimenT (QUIET) employs coherent receivers at 43GHz and 94GHz, operating on the Chajnantor plateau in the Atacama Desert in Chile, to measure the anisotropy in the polarization of the cosmic microwave background (CMB). QUIET primarily targets the B modes from primordial gravitational waves. The combination of these frequencies gives sensitivity to foreground contributions from diffuse Galactic synchrotron radiation. Between 2008 October and 2010 December, over 10,000hr of data were collected, first with the 19 element 43 GHz array (3458hr) and then with the 90 element 94 GHz array. Each array observes the same four fields, selected for low foregrounds, together covering ≈1000 deg2. This paper reports initial results from the 43 GHz receiver, which has an array sensitivity to CMB fluctuations of 69μK√s. The data were extensively studied with a large suite of null tests before the power spectra, determined with two independent pipelines, were examined. Analysis choices, including data selection, were modified until the null tests passed. Cross-correlating maps with different telescope pointings is used to eliminate a bias. This paper reports the EE, BB, and EB power spectra in the multipole range ℓ = 25-475. With the exception of the lowest multipole bin for one of the fields, where a polarized foreground, consistent with Galactic synchrotron radiation, is detected with 3σ significance, the E-mode spectrum is consistent with the ΛCDM model, confirming the only previous detection of the first acoustic peak. The B-mode spectrum is consistent with zero, leading to a measurement of the tensor-to-scalar ratio of r = 0.35+1.06 -0.87. The combination of a new time-stream "double-demodulation" technique, side-fed Dragonian optics, natural sky rotation, and frequent boresight rotation leads to the lowest level of systematic contamination in the B-mode power so far reported, below the level of r = 0.1. © 2011. The American Astronomical Society. All rights reserved.


Bischoff C.,University of Chicago | Bischoff C.,Harvard - Smithsonian Center for Astrophysics | Brizius A.,University of Chicago | Brizius A.,Max Planck Institute for Radio Astronomy | And 68 more authors.
Astrophysical Journal | Year: 2013

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°). Between 2008 October and 2010 December, two independent receiver arrays were deployed sequentially on a 1.4 m side-fed Dragonian telescope. The polarimeters that form the focal planes use a 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 μKs1/2) 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 μKs1/2 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, and sources of systematic error of the instrument. © 2013. The American Astronomical Society. All rights reserved.


Tran H.D.,Sandia National Laboratories | Emtman C.,Micro Encoder Inc. | Salsbury J.G.,Mitutoyo America Corporation | Wright W.,Mitutoyo America Corporation | Zwilling A.,Micro Encoder Inc.
Proceedings - ASPE 2011 Annual Meeting | Year: 2011

A mesoscale dimensional artifact based on silicon bulk micromachining fabrication has been developed and manufactured with the intention of evaluating the artifact both on a high precision coordinate measuring machine (CMM) and video-probe based measuring systems. This hybrid artifact has features that can be located by both a touch probe and a video probe system. A key feature is that the physical edge can be located using a touch probe CMM, and this same physical edge can also be located using a video probe. While video-probe based systems are commonly used to inspect mesoscale mechanical components, a video-probe system's certified accuracy is generally much worse than its repeatability. To solve this problem, an artifact has been developed which can be calibrated using a commercially available high-accuracy tactile system and then be used to calibrate typical production vision-based measurement systems. This allows for error mapping to a higher degree of accuracy than is possible with a typical chrome-on-glass reference artifact. Details of the designed features and manufacturing process of the hybrid dimensional artifact are given, and a comparison of the designed features to the measured features of the manufactured artifact is presented and discussed. Measurement results are presented using a meter-scale CMM with submicron measurement uncertainty; an optical CMM with submicron measurement uncertainty; a micro-CMM with submicron measurement uncertainty using three different probes; and a form contour instrument.


Andrews L.C.,Micro Encoder Inc. | Bernstein H.J.,Dowling College
Journal of Applied Crystallography | Year: 2014

Niggli reduction can be viewed as a series of operations in a six-dimensional space derived from the metric tensor. An implicit embedding of the space of Niggli-reduced cells in a higher-dimensional space to facilitate calculation of distances between cells is described. This distance metric is used to create a program, BGAOL, for Bravais lattice determination. Results from BGAOL are compared with results from other metric based Bravais lattice determination algorithms. This embedding depends on understanding the boundary polytopes of the Niggli-reduced cone N in the six-dimensional space G 6. This article describes an investigation of the boundary polytopes of the Niggli-reduced cone N in the six-dimensional space G 6 by algebraic analysis and organized random probing of regions near one-, two-, three-, four-, five-, six-, seven- and eightfold boundary polytope intersections. The discussion of valid boundary polytopes is limited to those avoiding the mathematically interesting but crystallographically impossible cases of zero-length cell edges. Combinations of boundary polytopes without a valid intersection in the closure of the Niggli cone or with an intersection that would force a cell edge to zero or without neighboring probe points are eliminated. In all, 216 boundary polytopes are found. There are 15 five-dimensional boundary polytopes of the full G 6 Niggli cone N. © 2014 International Union of Crystallography.


McGill K.J.,Dowling College | Asadi M.,Dowling College | Karakasheva M.T.,Dowling College | Andrews L.C.,Micro Encoder Inc. | Bernstein H.J.,Dowling College
Journal of Applied Crystallography | Year: 2014

A database of lattices using the G 6 representation of the Niggli-reduced cell as the search key provides a more robust and complete search than older techniques. Searching is implemented by finding the distance from the probe cell to other cells using a topological embedding of the Niggli reduction in G 6, so that all cells representing similar lattices will be found. The embedding provides the first fully linear measure of distances between unit cells. Comparison of results with those from older cell-based search algorithms suggests significant value in the new approach. © 2014 International Union of Crystallography.


PubMed | Micro Encoder Inc. and Dowling College
Type: Published Erratum | Journal: Journal of applied crystallography | Year: 2014

Ambiguities in the article by Andrews & Bernstein [

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