We describe a novel method to measure the absolute orientation of the polarization plane of the Cosmic Microwave Background (CMB) photons with arcsecond accuracy, enabling unprecedented measurements ...for cosmology and fundamental physics. Existing and planned CMB polarization instruments looking for primordial B-mode signals need an independent, experimental method for systematics control on the absolute polarization orientation. The lack of such a method limits the accuracy of the detection of inflationary gravitational waves, the constraining power on the neutrino sector through measurements of gravitational lensing of the CMB, the possibility of detecting Cosmic Birefringence (CB), and the ability to measure primordial magnetic fields. Sky signals used for calibration and direct measurements of the detector orientation cannot provide an accuracy better than 1
∘
. Self-calibration methods provide better accuracy, but may be affected by foreground signals and rely heavily on model assumptions, losing constraining power on fundamental processes, like CB, Faraday Rotation and chiral gravity models. The POLarization Orientation CALibrator for Cosmology, POLOCALC, will dramatically improve instrumental accuracy by means of an artificial calibration source flying on high-altitude balloons and aerial drones. Polarization angle calibration requires observation of a well-characterized distant source at high elevation angles. A balloon-borne calibrator will provide a source in the far field of larger telescopes, while an aerial drone can be used for tests and smaller polarimeters. POLOCALC will also allow a unique method to measure the telescopes’ polarized beam. Even a two-hour balloon flight will allow enough time to perform polarization angle calibration and polarized beam function measurements. The source will make use of both narrow and broadband microwave emitters between 40
GHz and 150
GHz coupled to precise polarizing filters. The orientation of the source polarization plane will be registered to absolute celestial coordinates by star cameras and gyroscopes with arcsecond accuracy. This project can become a rung in the calibration ladder for the field: any existing or future CMB polarization experiment observing our novel polarization calibrator will enable measurements of the polarization angle for each detector with respect to absolute sky coordinates.
The Next-Generation Balloon-borne Large-Aperture Submillimeter Telescope (BLAST-TNG) is a submillimeter imaging polarimeter which will map the polarized thermal emission from interstellar dust, ...revealing magnetic field structures in nearby giant molecular clouds, external galaxies and the diffuse interstellar medium in three bands centered at 250, 350 and 500-μm (spatial resolution of 30″, 41″ and 59″). Its camera contains over 2500 dual-polarization sensitive lumped element kinetic inductance detectors, which are read out using field-programmable gate array-based readout electronics. BLAST-TNG was scheduled for a 28-day Antarctic flight during the 2018/2019 summer season, but unfavorable weather conditions pushed the anticipated flight to 2019/2020. We present a summary of key results from the 2018/2019 preflight characterization of the detector and receiver. Included in this summary are detector yields, estimates of in-flight sensitivity, a measurement of the optical passbands and estimates of polarization efficiency.
The Advanced ACTPol (AdvACT) upgrade to the Atacama Cosmology Telescope (ACT) features arrays of aluminum manganese transition-edge sensors (TESes) optimized for ground-based observations of the ...cosmic microwave background (CMB). Array testing shows highly responsive detectors with anticipated in-band noise performance under optical loading. We report on TES parameters measured with impedance data taken on a subset of TESes. We then compare modeled noise spectral densities to measurements. We find excess noise at frequencies around 100 Hz, nearly outside of the signal band of CMB measurements. In addition, we describe full-array noise measurements in the laboratory and in the field for two new AdvACT mid-frequency arrays, sensitive at bands centered on 90 and 150 GHz, and data for the high-frequency array (150/230 GHz) as deployed.
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