Browsing by Subject "Cosmic microwave background"

Now showing 1 - 3 of 3
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    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.
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    The E and B EXperiment: implementation and analysis of the 2009 engineering flight.
    (2011-06) Milligan, Michael Bryce
    The E and B EXperiment (EBEX) is a balloon-borne telescope designed to map the polarization of the cosmic microwave background (CMB) and emission from galactic dust at millimeter wavelengths from 150 to 410 GHz. The primary science objectives of EBEX are to: detect or constrain the primordial B-mode polarization of the CMB predicted by in ationary cosmology; measure the CMB B-mode signal induced by gravitational lensing; and characterize the polarized thermal emission from interstellar dust. EBEX will observe a 420 square degree patch of the sky at high galactic latitude with a telescope and camera that provide an 80 beam at three observing bands (150, 250, and 410 GHz) and a 6:2#14; diffraction limited field of view to two large-format bolometer array focal planes. Polarimetry is achieved via a continuously rotating half-wave plate (HWP), and the optical system is designed from the ground up for control of sidelobe response and polarization systematic errors. EBEX is intended to execute y or more Antarctic long duration balloon campaigns. In June 2009 EBEX completed a North American engineering flight launched from NASA's Columbia Scientific Ballooning Facility (CSBF) in Ft. Sumner, NM and operated in the stratosphere above 30 km altitude for #24; 10 hours. During flight EBEX must be largely autonomous as it conducts pointed, scheduled observations; tunes and operates 1432 TES bolometers via 28 embedded Digital frequency-domain multiplexing (DfMux) computers; logs over 3 GiB/hour of science and housekeeping data to onboard redundant disk storage arrays; manages and dispatches jobs over a fault-tolerant onboard Ethernet network; and feeds a complex real-time data processing infrastructure on the ground via satellite and line-of-sight (LOS) downlinks. In this thesis we review the EBEX instrument, present the optical design and the computational architecture for in-flight control and data handling, and the quick-look software stack. Finally we describe the 2009 North American test flight and present analysis of data collected at the end of that flight that characterizes scan-synchronous signals and the expected response to emission from thermal dust in our galaxy.
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    Phenomenology of particle production during inflation
    (2013-09) Namba, Ryo
    This thesis is devoted to the study on particle production during the era of primordial inflation and its phenomenological impacts. The simplest models of inflation typically assume only one dynamical degree of freedom, inflaton, that is responsible for all the inflationary dynamics and predictions. Yet, it is a natural expectation that the inflaton should be coupled to some other fields, in need of successful reheating of the universe after inflation. We first consider the models in which the inflaton is coupled to a U(1) gauge field. For a pseudo-scalar inflaton, its natural coupling induces tachyonic growth of the gauge quanta, which then inverse-decay to the inflaton perturbations. This imprints non-Gaussianity in the cosmic microwave background (CMB) anisotropies. This non-Gaussianity has a nearly equilateral shape, and the fact that we have not observed it with Planck provides a bound on the axion decay constant, which is in the range naturally obtained in UV completed theories. The produced gauge quanta also source gravitational waves (GWs). Future GW interferometer experiments can improve over the CMB non-Gaussianity limits. We then study a different model characterized by a scalar inflaton coupled to gauge fields via a dilation-like interaction. This coupling can result in a nearly scale-invariant spectrum for the gauge field. Also in this case, the produced gauge quanta source inflaton perturbations, but the resulting non-Gaussianity now has a shape peaked for squeezed triangles, and which exhibits a peculiar angular dependence, that, if detected, would be a smoking gun of the higher-spin fields involved. In the above two models, the GW signals are always subdominant at the CMB scales, due to the non-Gaussianity bounds from the scalar perturbations (namely, from the perturbations generated by the inflaton quanta produced by the gauge fields). We study the radically different situation in which some field other than the inflaton produces the gauge quanta, and these quanta have no direct coupling (apart from the unavoidable gravitational interaction) to the inflaton. We study whether this production can result in a detectable GW signal at CMB scales, without conflicting with the bounds from non-Gaussianity of the scalar perturbations. We study two possibilities: (i) gauge quanta production due to a sudden variation of their mass, and (ii) gauge quanta production from a rolling pseudo scalar. In case (i), we find that GW signals are unlikely to be detectable, due to the suppressed quadrupole moment of non-relativistic quanta. In case (ii), we instead find that GWs from particle production can actually exceed the usual inflationary vacuum fluctuations. The observable B-mode polarization can be obtained for any choice of inflaton potential, and the amplitude of the signal is not necessarily correlated with the scale of inflation.