Bulletin of the American Physical Society
APS April Meeting 2020
Volume 65, Number 2
Saturday–Tuesday, April 18–21, 2020; Washington D.C.
Session B10: Cosmic Microwave Background and Cosmic Ray ObservationOn Demand
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Sponsoring Units: DAP Room: Roosevelt 5 |
Saturday, April 18, 2020 10:45AM - 10:57AM |
B10.00001: The Cosmology Large Angular Scale Surveyor (CLASS) Sumit Dahal The Cosmology Large Angular Scale Surveyor (CLASS) aims to make a near cosmic-variance-limited measurement of the optical depth to reionization and characterize the primordial gravitational waves by mapping the cosmic microwave background (CMB) polarization on large angular scales. CLASS is an array of four telescopes: two 90 GHz telescopes optimized for CMB observation near the minimum of polarized Galactic emission, with 40 GHz and dichroic 150/220 GHz receivers designed to probe the polarized synchrotron and dust emissions, respectively. In addition to large sky coverage and broad frequency range, a rapid front-end polarization modulator and background-limited detectors provide CLASS with high sensitivity. In September 2019, CLASS had all its four frequencies on the sky. In this talk, we present the on-sky performance of CLASS telescopes and give an update on early results and project status. [Preview Abstract] |
Saturday, April 18, 2020 10:57AM - 11:09AM On Demand |
B10.00002: CMB polarization low-frequency noise level reduction enabled by the CLASS telescope polarization modulators Joseph Cleary The Cosmology Large Angular Scale Surveyor (CLASS) is a telescope array that measures the polarization of the cosmic microwave background (CMB) on the largest angular scales. Observing at frequency bands centered at 40, 90, 150, and 220 GHz, CLASS aims to constrain the inflationary tensor-to-scalar ratio and optical depth to reionization. These large-scale observations are enabled by a novel, front-end modulator technology called a Variable-delay Polarization Modulator (VPM). A VPM consists of a wire grid in front of a moveable mirror. Varying the grid-mirror separation modulates linear and circular polarization incident on the VPM. This creates a lock-in style measurement and separates sky polarization from polarization internal to the telescope. Here, we demonstrate the ability of the VPM to reduce the observed noise level at large angular scales. [Preview Abstract] |
Saturday, April 18, 2020 11:09AM - 11:21AM Not Participating |
B10.00003: SPIDER: First-Flight Data Analysis Update Jeffrey Filippini SPIDER is a balloon-borne polarimeter aiming to measure the polarization of the Cosmic Microwave Background with unprecedented sensitivity over about 10% of the southern sky. The payload took off on its maiden flight from McMurdo Station, Antarctica on 1 January 2015, mapping the sky at 95 and 150 GHz. A second flight scheduled for the 2020--2021 austral summer will gather additional data at these frequencies and provide novel measurements at 280 GHz. This latter capability will allow for improved characterization of the polarized emission from interstellar dust, and thereby a more robust constraint on the presence of a primordial divergence-free ("B-mode") polarization pattern in the microwave sky. In this talk, we will provide a progress report on the analysis of the data from SPIDER's first flight. In particular, we will present our understanding of the systematic and Galactic foreground contamination levels in the data, with an emphasis on the uncertainty inherent to the foreground removal processes. [Preview Abstract] |
Saturday, April 18, 2020 11:21AM - 11:33AM |
B10.00004: Observations of Interstellar Atomic Species by the Magnetospheric Multiscale Mission (MMS) Roman Gomez, Stephen Fuselier, James Burch, Joey Mukherjee, Carrie Gonzalez A constant neutral wind of interstellar material, mostly hydrogen, constantly enters the heliosphere at a velocity of 26 km/s as a consequence of the Sun's motion relative to the local interstellar medium (LISM). Neutral atoms in the heliosphere are solely under the influence of the gravity and radiation pressure which both increase inversely as $r^{2}$ (where $r$ is the heliocentric distance). With decreasing distance, the gravitational influence of the Sun causes the formation of focusing cones for species more massive than hydrogen, i.e. regions of enhanced density on the downwind side of the Sun. The increased density leads to a higher probability of ionization which makes these newly born ions visible to plasma instruments of in the vicinity of the cone. For hydrogen atoms, gravity and radiation pressure essentially balance out. In addition, the higher ionization rates of hydrogen relative to other ion species leads to the formation of an interstellar neutral (ISN) hydrogen cavity upwind and downwind of the Sun. It is thought that during solar minima that observation of interstellar hydrogen ions will also be possible. In this work is presented interstellar hydrogen observations as well as sequential annual surveys of the helium focusing cone by the plasma instrument of the MMS mission. [Preview Abstract] |
Saturday, April 18, 2020 11:33AM - 11:45AM On Demand |
B10.00005: Determining Angle Dependent Effective Rigidity Cutoffs for ISS-CALET Ultra-Heavy Cosmic-Ray Analysis Wolfgang Zober The CALorimetric Electron Telescope (CALET) has been collecting data on the International Space Station (ISS) since shortly after its launch in August 2015. Its main calorimeter (CAL), is designed to measure the fluxes of the highest energy cosmic-ray electrons, but has also made excellent measurements of cosmic-ray (CR) nuclei and gamma rays. Ultra-heavy (UH) CR events are screened by the geomagnetic field, which the preliminary analysis has used for a vertical cutoff rigidity to determine a minimum energy threshold for valid events. Current work is now being done to improve this energy threshold to boost statistics and resolution in UHCR measurements by calculating an angle dependent effective cutoff rigidity. This has been explored in two ways: an angle dependent Stoermer approximation and a ray-tracing program that calculates the effective cutoff by determining allowed trajectory energies with a Cash-Karp Runge-Kutta that was inspired by the work of D.F. Smart and M.A. Shea. These methods have found use in UHCR analysis and could be used in a positron-electron spectra calculation. Here we present the current state of the analysis and show the improvements in the data thus far from properly accounting for the trajectory of the detected nuclei. [Preview Abstract] |
Saturday, April 18, 2020 11:45AM - 11:57AM Not Participating |
B10.00006: Performance and Preliminary Results of the ISS-CREAM Instrument Jason Link, Tyler Anderson, Yu Chen, Stephane Coutu, Tyler LaBree, John Mitchell, Isaac Mognet, Scott Nutter, Kenichi Sakai, Jacob Smith, Monong Yu The Cosmic Ray Energetics And Mass for the International Space Station (ISS-CREAM) experiment was built by an international collaboration from the US, Republic of Korea, France, and Mexico to measure the elemental spectra of cosmic rays from Z$=$1 to Z$=$26 over the energy range of 10$^{\mathrm{12}}$-10$^{\mathrm{15}}$ eV. ISS-CREAM was installed on the International Space Station on August 22, 2017. Mission operation was terminated on February 12, 2019. Since then, the present group of authors have continued to analyze the data collected over ISS-CREAM's approximately 1.5 years of operation. In this talk, we discuss the performance of the instrument during operation as well as the current status of this data analysis, including preliminary cosmic ray elemental spectra. [Preview Abstract] |
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