The Cosmology Large Angular Scale Surveyor (CLASS) is an experiment to measure the signature of a gravitational-wave background from inflation in the polarization of the cosmic microwave background (CMB). CLASS is a multi-frequency array of four telescopes operating from a high-altitude site in the Atacama Desert in Chile. CLASS will survey 70% of the sky in four frequency bands centered at 38, 93, 148, and 217 GHz, which are chosen to straddle the Galactic-foreground minimum while avoiding strong atmospheric emission lines. This broad frequency coverage ensures that CLASS can distinguish Galactic emission from the CMB. The sky fraction of the CLASS survey will allow the full shape of the primordial B-mode power spectrum to be characterized, including the signal from reionization at low . Its unique combination of large sky coverage, control of systematic errors, and high sensitivity will allow CLASS to measure or place upper limits on the tensor-to-scalar ratio at a level of r = 0.01 and make a cosmic-variance-limited measurement of the optical depth to the surface of last scattering, τ .Recently, the BICEP2 experiment announced the detection of B-mode polarization at of 40-200, 5 but it is unclear whether this signal is cosmological or Galactic in nature. These results have generated strong interest in complementary experiments and have highlighted the importance of multi-frequency observations for foreground subtraction. A measurement of B-modes in the CMB would constitute important evidence for inflation and a measurement of the energy scale at which inflation occured. The tensor-to-scalar ratios, r ≤ 0.1, being probed correspond to E ∼ 10 16 GeV, near grand-unified-theory (GUT) energy scales. The gravitational waves from inflation are our only probe of the physics at such enormous energies and at such early times, just 10 −35 seconds after the Big Bang. They would also provide the first firm evidence for the existence of quantum-gravitational effects. 6 Detecting primordial gravitational waves requires greater frequency coverage to definitively rule out Galactic foreground contamination, as well as a measurement of the B-mode signal over a wider range of angular scales to verify the full shape of the B-mode power spectrum.A number of experiments are searching for B-mode polarization. Notably, the Planck satellite has mapped the entire sky in nine frequency bands from 30 to 857 GHz, allowing measurement of CMB polarization over a broad range of angular scales with the ability to remove Galactic foreground contamination; however, it is yet to be seen whether Planck will have the ability to constrain this signal. In this paper we present the Cosmology Large Angular Scale Surveyor (CLASS), which is leading the effort to map the CMB polarization at large angular scales from the ground. CLASS will observe in four frequency bands centered on 38, 93, 148, and 217 GHz. CLASS is uniquely poised to measure inflationary gravitational waves through its ability to measure CMB polarization at the largest angular scales, a...

26New capabilities for imaging small-scale instabilities and turbulence and for modeling 27 gravity wave (GW), instability, and turbulence dynamics at high Reynolds numbers are 28 employed to identify the major instabilities and quantify turbulence intensities near the summer 29 mesopause. High-resolution imaging of polar mesospheric clouds (PMCs) reveal a range of 30 instability dynamics and turbulence sources that have their roots in multi-scale GW dynamics at 31 larger spatial scales. Direct numerical simulations (DNS) of these dynamics exhibit a range of 32 instability types that closely resemble instabilities and turbulence seen in PMC imaging and by 33 ground-based and in-situ instruments at all times and altitudes. The DNS also exhibit the 34 development of "sheet-and-layer" (S&L) structures in the horizontal wind and thermal stability 35 fields that resemble observed flows near the mesopause and at lower altitudes. 36Both observations and modeling suggest major roles for GW breaking, Kelvin-Helmholtz 37 instabilities (KHI), and intrusions in turbulence generation and energy dissipation. Of these, 38 larger-scale GW breaking and KHI play the major roles in energetic flows leading to strong 39 turbulence. GW propagation and breaking can span several S&L features and induce KHI 40 ranging from GW to turbulence scales. Intrusions make comparable contributions to turbulence 41 generation as instabilities become weaker and more intermittent. Turbulence intensities are 42 highly variable in the vertical and typically span 3 or more decades. DNS results that closely 43 resemble observed flows suggest a range of mechanical energy dissipation rates of ε ~10 -3 -10 44Wkg -1 that is consistent with the range of in-situ measurements at ~80-90 km in summer. 45 46 dynamics 48 49 50 51 throughout the atmosphere for more than five decades (e.g., Panofsky

Analysis of the acoustoelectric behavior of microwave frequency, temperature-compensated AlN-based multilayer coupling configurations J. Appl. Phys. 104, 104509 (2008) We discuss the design, fabrication, and testing of prototype horn-coupled, lumped-element kinetic inductance detectors (LEKIDs) designed for cosmic microwave background studies. The LEKIDs are made from a thin aluminum film deposited on a silicon wafer and patterned using standard photolithographic techniques at STAR Cryoelectronics, a commercial device foundry. We fabricated 20-element arrays, optimized for a spectral band centered on 150 GHz, to test the sensitivity and yield of the devices as well as the multiplexing scheme. We characterized the detectors in two configurations. First, the detectors were tested in a dark environment with the horn apertures covered, and second, the horn apertures were pointed towards a beam-filling cryogenic blackbody load. These tests show that the multiplexing scheme is robust and scalable, the yield across multiple LEKID arrays is 91%, and the measured noise-equivalent temperatures for a 4 K optical load are in the range 26 ± 6 μK √ s. © 2014 AIP Publishing LLC. [http://dx

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 (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 = 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.

Instabilities and turbulence extending to the smallest dynamical scales play important roles in the deposition of energy and momentum by gravity waves throughout the atmosphere. However, these dynamics and their effects have been impossible to quantify to date due to lack of observational guidance. Serendipitous optical images of polar mesospheric clouds at ∼82 km obtained by star cameras aboard a cosmology experiment deployed on a stratospheric balloon provide a new observational tool, revealing instability and turbulence structures extending to spatial scales < 20 m. At 82 km, this resolution provides sensitivity extending to the smallest turbulence scale not strongly influenced by viscosity: the “inner scale” of turbulence, l0∼10(ν3/ϵ)1/4. Such images represent a new window into small‐scale dynamics that occur throughout the atmosphere but are impossible to observe in such detail at any other altitude. We present a sample of images revealing a range of dynamics features and employ numerical simulations that resolve these dynamics to guide our interpretation of several observed events.