116 research outputs found
The Double Entry Journal
The Double Entry Journal is a note-taking technique for English Composition courses that encourages students to become active readers
High-Precision Scanning Water Vapor Radiometers for Cosmic Microwave Background Site Characterization and Comparison
The compelling science case for the observation of B-mode polarization in the
cosmic microwave background (CMB) is driving the CMB community to expand the
observed sky fraction, either by extending survey sizes or by deploying
receivers to potential new northern sites. For ground-based CMB instruments,
poorly-mixed atmospheric water vapor constitutes the primary source of
short-term sky noise. This results in short-timescale brightness fluctuations,
which must be rejected by some form of modulation. To maximize the sensitivity
of ground-based CMB observations, it is useful to understand the effects of
atmospheric water vapor over timescales and angular scales relevant for CMB
polarization measurements. To this end, we have undertaken a campaign to
perform a coordinated characterization of current and potential future
observing sites using scanning 183 GHz water vapor radiometers (WVRs). So far,
we have deployed two identical WVR units; one at the South Pole, Antarctica,
and the other at Summit Station, Greenland. The former site has a long heritage
of ground-based CMB observations and is the current location of the Bicep/Keck
Array telescopes as well as the South Pole Telescope. The latter site, though
less well characterized, is under consideration as a northern-hemisphere
location for future CMB receivers. Data collection from this campaign began in
January 2016 at South Pole and July 2016 at Summit Station. Data analysis is
ongoing to reduce the data to a single spatial and temporal statistic that can
be used for one-to-one site comparison.Comment: Published in Proc. SPIE. Presented at SPIE Astronomical Telescopes
and Instrumentation Conference 10708: Millimeter, Submillimeter, and
Far-Infrared Detectors and Instrumentation for Astronomy XI, June 2018. 10
pages, 11 figure
BICEP3: a 95 GHz refracting telescope for degree-scale CMB polarization
BICEP3 is a 550 mm-aperture refracting telescope for polarimetry of radiation
in the cosmic microwave background at 95 GHz. It adopts the methodology of
BICEP1, BICEP2 and the Keck Array experiments - it possesses sufficient
resolution to search for signatures of the inflation-induced cosmic
gravitational-wave background while utilizing a compact design for ease of
construction and to facilitate the characterization and mitigation of
systematics. However, BICEP3 represents a significant breakthrough in
per-receiver sensitivity, with a focal plane area 5 larger than a
BICEP2/Keck Array receiver and faster optics ( vs. ).
Large-aperture infrared-reflective metal-mesh filters and infrared-absorptive
cold alumina filters and lenses were developed and implemented for its optics.
The camera consists of 1280 dual-polarization pixels; each is a pair of
orthogonal antenna arrays coupled to transition-edge sensor bolometers and read
out by multiplexed SQUIDs. Upon deployment at the South Pole during the 2014-15
season, BICEP3 will have survey speed comparable to Keck Array 150 GHz (2013),
and will significantly enhance spectral separation of primordial B-mode power
from that of possible galactic dust contamination in the BICEP2 observation
patch.Comment: 12 pages, 5 figures. Presented at SPIE Astronomical Telescopes and
Instrumentation 2014: Millimeter, Submillimeter, and Far-Infrared Detectors
and Instrumentation for Astronomy VII. To be published in Proceedings of SPIE
Volume 915
BICEP2 / Keck Array VIII: Measurement of gravitational lensing from large-scale B-mode polarization
We present measurements of polarization lensing using the 150 GHz maps which
include all data taken by the BICEP2 & Keck Array CMB polarization experiments
up to and including the 2014 observing season (BK14). Despite their modest
angular resolution (), the excellent sensitivity (K-arcmin) of these maps makes it possible to directly reconstruct the
lensing potential using only information at larger angular scales (). From the auto-spectrum of the reconstructed potential we measure an
amplitude of the spectrum to be (Planck
CDM prediction corresponds to ), and reject
the no-lensing hypothesis at 5.8, which is the highest significance
achieved to date using an EB lensing estimator. Taking the cross-spectrum of
the reconstructed potential with the Planck 2015 lensing map yields
. These direct measurements of
are consistent with the CDM cosmology, and with
that derived from the previously reported BK14 B-mode auto-spectrum (). We perform a series of null tests and consistency
checks to show that these results are robust against systematics and are
insensitive to analysis choices. These results unambiguously demonstrate that
the B-modes previously reported by BICEP / Keck at intermediate angular scales
() are dominated by gravitational lensing. The
good agreement between the lensing amplitudes obtained from the lensing
reconstruction and B-mode spectrum starts to place constraints on any
alternative cosmological sources of B-modes at these angular scales.Comment: 12 pages, 8 figure
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