Horn Coupled Multichroic Polarimeters for the Atacama Cosmology Telescope Polarization Experiment

Multichroic polarization sensitive detectors enable increased sensitivity and spectral coverage for observations of the Cosmic Microwave Background (CMB). An array optimized for dual frequency detectors can provide 1.7 times gain in sensitivity compared to a single frequency array. We present the design and measurements of horn coupled multichroic polarimeters encompassing the 90 and 150 GHz frequency bands and discuss our plans to field an array of these detectors as part of the ACTPol project

New SETI Sky Surveys for Radio Pulses

Berkeley conducts 7 SETI programs at IR, visible and radio wavelengths. Here we review two of the newest efforts, Astropulse and Fly's Eye. A variety of possible sources of microsecond to millisecond radio pulses have been suggested in the last several decades, among them such exotic events as evaporating primordial black holes, hyper-flares from neutron stars, emissions from cosmic strings or perhaps extraterrestrial civilizations, but to-date few searches have been conducted capable of detecting them. We are carrying out two searches in hopes of finding and characterizing these mu-s to ms time scale dispersed radio pulses. These two observing programs are orthogonal in search space; the Allen Telescope Array's (ATA) "Fly's Eye" experiment observes a 100 square degree field by pointing each 6m ATA antenna in a different direction; by contrast, the Astropulse sky survey at Arecibo is extremely sensitive but has 1/3,000 of the instantaneous sky coverage. Astropulse's multibeam data is transferred via the internet to the computers of millions of volunteers. These computers perform a coherent de-dispersion analysis faster than the fastest available supercomputers and allow us to resolve pulses as short as 400 ns. Overall, the Astropulse survey will be 30 times more sensitive than the best previous searches. Analysis of results from Astropulse is at a very early stage. The Fly's Eye was successfully installed at the ATA in December of 2007, and to-date approximately 450 hours of observation has been performed. We have detected three pulsars and six giant pulses from the Crab pulsar in our diagnostic pointing data. We have not yet detected any other convincing bursts of astronomical origin in our survey data. (Abridged)Comment: 9 pages, 6 figures, Accepted to Acta Astronautica "Special Issue: Life Signatures

Current and Nascent SETI Instruments

Here we describe our ongoing efforts to develop high-performance and sensitive instrumentation for use in the search for extra-terrestrial intelligence (SETI). These efforts include our recently deployed Search for Extraterrestrial Emissions from Nearby Developed Intelligent Populations Spectrometer (SERENDIP V.v) and two instruments currently under development; the Heterogeneous Radio SETI Spectrometer (HRSS) for SETI observations in the radio spectrum and the Optical SETI Fast Photometer (OSFP) for SETI observations in the optical band. We will discuss the basic SERENDIP V.v instrument design and initial analysis methodology, along with instrument architectures and observation strategies for OSFP and HRSS. In addition, we will demonstrate how these instruments may be built using low-cost, modular components and programmed and operated by students using common languages, e.g. ANSI C.Comment: 12 pages, 5 figures, Original version appears as Chapter 2 in "The Proceedings of SETI Sessions at the 2010 Astrobiology Science Conference: Communication with Extraterrestrial Intelligence (CETI)," Douglas A. Vakoch, Edito

BFORE: The B-mode Foreground Experiment

The B-mode Foreground Experiment (BFORE) is a proposed NASA balloon project designed to make optimal use of the sub-orbital platform by concentrating on three dust foreground bands (270, 350, and 600 GHz) that complement ground-based cosmic microwave background (CMB) programs. BFORE will survey ~1/4 of the sky with 1.7 - 3.7 arcminute resolution, enabling precise characterization of the Galactic dust that now limits constraints on inflation from CMB B-mode polarization measurements. In addition, BFORE's combination of frequency coverage, large survey area, and angular resolution enables science far beyond the critical goal of measuring foregrounds. BFORE will constrain the velocities of thousands of galaxy clusters, provide a new window on the cosmic infrared background, and probe magnetic fields in the interstellar medium. We review the BFORE science case, timeline, and instrument design, which is based on a compact off-axis telescope coupled to >10,000 superconducting detectors.Comment: 7 pages, 4 figures, conference proceedings published in Journal of Low Temperature Physic

Altered Tendon Characteristics and Mechanical Properties Associated with Insertional Achilles Tendinopathy

Study Design: Case-control laboratory study. Objectives: To compare tendon characteristics (shape, composition) and mechanical properties (strain, stiffness) on the involved side of participants with insertional Achilles tendinopathy (IAT) to the uninvolved side and to controls, and to examine if severity of tendon pathology is associated with severity of symptoms during function. Background: Despite the severity and chronicity of IAT, the quality of theoretical evidence available to guide the development of exercise interventions is low. While tendon pathology of midportion Achilles tendinopathy has been described, there are few studies specific to IAT. Methods: Twenty individuals with unilateral IAT and 20 age- and sex-matched controls volunteered to participate. Ultrasound imaging was used to quantify changes in tendon shape (diameter) and composition (echogenicity). A combination of ultrasound and dynamometry was used to measure tendon mechanical properties (strain and stiffness) during passive ankle rotation toward dorsiflexion. Generalized estimating equations were used to examine the association between IAT, alterations in tendon properties, and participant demographics. Pearson correlation was used to examine the association between severity of tendon pathology and severity of symptoms (Victorian Institute of Sport Assessment-Achilles). Results: The side with IAT had a larger tendon diameter (P Conclusion: Ultrasound imaging combined with dynamometry can discriminate alterations in tendon shape, composition, and mechanics in participants with IAT. Future clinical trials for IAT may consider strategies to alter tendon characteristics and restore tendon mechanic

CCAT-prime: a novel telescope for submillimeter astronomy

The CCAT-prime telescope is a 6-meter aperture, crossed-Dragone telescope, designed for millimeter and sub-millimeter wavelength observations. It will be located at an altitude of 5600 meters, just below the summit of Cerro Chajnantor in the high Atacama region of Chile. The telescope's unobscured optics deliver a field of view of almost 8 degrees over a large, flat focal plane, enabling it to accommodate current and future instrumentation fielding >100k diffraction-limited beams for wavelengths less than a millimeter. The mount is a novel design with the aluminum-tiled mirrors nested inside the telescope structure. The elevation housing has an integrated shutter that can enclose the mirrors, protecting them from inclement weather. The telescope is designed to co-host multiple instruments over its nominal 15 year lifetime. It will be operated remotely, requiring minimum maintenance and on-site activities due to the harsh working conditions on the mountain. The design utilizes nickel-iron alloy (Invar) and carbon-fiber-reinforced polymer (CFRP) materials in the mirror support structure, achieving a relatively temperature-insensitive mount. We discuss requirements, specifications, critical design elements, and the expected performance of the CCAT-prime telescope. The telescope is being built by CCAT Observatory, Inc., a corporation formed by an international partnership of universities. More information about CCAT and the CCAT-prime telescope can be found at www.ccatobservatory.org.Comment: Event: SPIE Astronomical Telescope + Instrumentation, 2018, Austin, Texas, USA; Proceedings Volume 10700, Ground-based and Airborne Telescopes VII; 107005X (2018

The Cosmology Large Angular Scale Surveyor

The Cosmology Large Angular Scale Surveyor (CLASS) is a four telescope array designed to characterize relic primordial gravitational waves from inflation and the optical depth to reionization through a measurement of the polarized cosmic microwave background (CMB) on the largest angular scales. The frequencies of the four CLASS telescopes, one at 38 GHz, two at 93 GHz, and one dichroic system at 145/217 GHz, are chosen to avoid spectral regions of high atmospheric emission and span the minimum of the polarized Galactic foregrounds: synchrotron emission at lower frequencies and dust emission at higher frequencies. Low-noise transition edge sensor detectors and a rapid front-end polarization modulator provide a unique combination of high sensitivity, stability, and control of systematics. The CLASS site, at 5200 m in the Chilean Atacama desert, allows for daily mapping of up to 70\% of the sky and enables the characterization of CMB polarization at the largest angular scales. Using this combination of a broad frequency range, large sky coverage, control over systematics, and high sensitivity, CLASS will observe the reionization and recombination peaks of the CMB E- and B-mode power spectra. CLASS will make a cosmic variance limited measurement of the optical depth to reionization and will measure or place upper limits on the tensor-to-scalar ratio, $r$, down to a level of 0.01 (95\% C.L.)

Optical modeling and polarization calibration for CMB measurements with ACTPol and Advanced ACTPol

The Atacama Cosmology Telescope Polarimeter (ACTPol) is a polarization sensitive upgrade to the Atacama Cosmology Telescope. Located at an elevation of 5190 m, ACTPol measures the Cosmic Microwave Background (CMB) temperature and polarization with arcminute-scale angular resolution. Calibration of the detector angles is a critical step in producing maps of the CMB polarization. Polarization angle offsets in the detector calibration can cause leakage in polarization from E to B modes and induce a spurious signal in the EB and TB cross correlations, which eliminates our ability to measure potential cosmological sources of EB and TB signals, such as cosmic birefringence. We present our optical modeling and measurements associated with calibrating the detector angles in ACTPol.Comment: 12 pages, 8 figures, conference proceedings submitted to Proceedings of SPIE; added reference in section 2 and merged repeated referenc

Detection of the Power Spectrum of Cosmic Microwave Background Lensing by the Atacama Cosmology Telescope

We report the first detection of the gravitational lensing of the cosmic microwave background through a measurement of the four-point correlation function in the temperature maps made by the Atacama Cosmology Telescope. We verify our detection by calculating the levels of potential contaminants and performing a number of null tests. The resulting convergence power spectrum at 2-degree angular scales measures the amplitude of matter density fluctuations on comoving length scales of around 100 Mpc at redshifts around 0.5 to 3. The measured amplitude of the signal agrees with Lambda Cold Dark Matter cosmology predictions. Since the amplitude of the convergence power spectrum scales as the square of the amplitude of the density fluctuations, the 4-sigma detection of the lensing signal measures the amplitude of density fluctuations to 12%.Comment: 4 pages, 4 figures, replaced title and author list with version accepted by Physical Review Letters. Likelihood code can be downloaded from http://bccp.lbl.gov/~sudeep/ACTLensLike.htm