Between Dec 19, 2024 and Jan 2, 2025, datasets can be submitted to DRUM but will not be processed until after the break. Staff will not be available to answer email during this period, and will not be able to provide DOIs until after Jan 2. If you are in need of a DOI during this period, consider Dryad or OpenICPSR. Submission responses to the UDC may also be delayed during this time.

Browsing by Subject "Polarimetry"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Calibration of the E and B EXperiment (EBEX), a balloon-borne cosmic microwave background polarimeter.
    (2009-10) Polsgrove, Daniel Edward
    We discuss pre-flight calibration of the E and B EXperiment (EBEX), a balloon-borne telescope designed to measure the B-mode polarization anisotropy of the cosmic microwave background (CMB). EBEX will observe the sky with 8' resolution in each of three bands centered on 150, 250 and 410 GHz. Employing over 1,400 detectors and performing polarimetry through a continuously rotating half-wave plate with fixed wire-grid polarizer, we expect to detect the B-mode signal or set a new upper limit one order of magnitude below the current value. In this thesis we describe a set of ground-based experiments devised for calibrating instrumental response to incident millimeter-wave flux with varying spectral and polarization properties. We chronicle the design, construction and execution of these experiments, along with preliminary results from tests executed prior to our North American (NA) test flight which originated at the Columbia Scientific Ballooning Facility, Ft Sumner, NM in June 2009. A brief review of this inaugural flight is provided, as is a synopsis of our current plan for a comprehensive calibration strategy to be implemented in conjunction with a future long duration balloon (LDB) flight over Antarctica.
  • Thumbnail Image
    Item
    Design, implementation, and calibration of physics Half-Wave Plate polarimetry for the E and B Experiment
    (2014-10) Klein, Jeffrey Michael
    The E and B Experiment (EBEX) is a balloon-borne telescope designed to measure the polarization of the Cosmic Microwave Background (CMB) and dust foregrounds at 10' scales and three frequency bands of 150 GHz, 250 GHz, and 410 GHz in order to detect or constrain B-mode polarization. Results may provide evidence to support the theory of cosmological inflation, or constrain specific models.EBEX's polarization measurement capability is implemented via continuously-rotating Half-Wave Plate (HWP) polarimetry. We discuss the design and implementation of the polarimetry hardware for the E and B Experiment (EBEX). In order to achieve low-temperature rotation of our 15 cm, 635 g achromatic HWP stack, we implement a unique application of a Superconducting Magnetic Bearing (SMB), building off an earlier prototype. We discuss design constraints, detail our implementation, and present results of tests of power dissipation, rotation speed stability, dynamic stability, and operational lifetime. We find power dissipation of 15 mW in our LDB configuration, and achieve successful operation of the system in both a 2009 test flight and a 2012 Long Duration (LDB) flight.We design and carry out calibration tests to verify our ability to measure polarized signals. We develop a data analysis pipeline to extract polarization measurements from the chopped polarized signals we use in calibration; we verify and optimize the performance of this pipeline with a simulation. We find that a thorough understanding of the time constants of EBEX's bolometric sensors is essential to measure polarization. We develop methods to measure and remove the effects of these time constants. Tests of polarization rotation across our bands verify predictions of rotation due to our achromatic HWP 5-stack. Polarized beam scans allow us to set an absolute calibration for EBEX with a standard deviation of 1.5 degrees.
  • Thumbnail Image
    Item
    Magnetic Fields of Spiral Galaxies Observed with Far-Infrared Polarimetry: M 51 and NGC 891
    (2023-05) Kim, Jin-Ah
    We explore the magnetic field geometry in two nearby spiral galaxies, M 51 and NGC 891. We look into the magnetic field geometry derived from interstellar polarization, using polarimetric images made with Stratospheric Observatory For Infrared Astronomy/High-resolution Airborne Wideband Camera-Plus at 154 μm in the far-infrared (far-IR). This study aims to characterize the magnetic fields of typical spiral galaxies in three dimensions based on the magnetic field geometry seen in the face-on galaxy, M 51, and the edge-on galaxy, NGC 891.Far-IR polarimetry in M 51 shows that the magnetic field geometry in the galactic plane is aligned with a spiral pattern delineated by gas distributions. The inferred magnetic fields in the northeastern part of the galaxy tend to diverge from the spiral pattern and point more toward the interacting companion M 51b. We derive the mean degree of polarization in M 51 based on a Bayesian theorem and the Rice probability distribution. The similar fractional polarization in the arm and inter-arm regions implies no significant difference in turbulent magnetic fields between those environments. The magnetic field geometry inferred in M 51b is not aligned with the stellar bar of the galaxy but may correspond to the orientation of a curved structure of the inner region of the bar. Magnetic fields inferred in NGC 891, an edge-on galaxy, generally lie close to the galactic plane. There is one location with vertical magnetic fields in the galactic disk, probably caused by a blowout associated with star formation. We investigate the far-IR polarimetry in NGC 891 by comparing it with simple model galaxies in which a planar, ordered magnetic field and an isotropic random field contribute to the net field geometry. The observed low fractional polarization at either side of the central region of NGC 891 is best explained as being due to the line of sight (LOS) being tangent to spiral arms, with the field aligned along the LOS. While the reduced polarization observed at the center is not well explained in the model using a normal spiral, using a barred model galaxy instead can match the observations. Overall low fractional polarization compared to other galaxies seen in the galactic plane implies significant turbulence and many turbulent decorrelation cells along the LOS through the plane. Unexpected low polarization off the galactic plane is likely due to a mixture of planar and vertical fields in the dusty regions of the halo.