217 research outputs found
Characterization of a half-wave plate for cosmic microwave background circular polarization measurement with POLARBEAR
A half-wave plate (HWP) is often used as a modulator to suppress systematic
error in the measurements of cosmic microwave background (CMB) polarization. A
HWP can also be used to measure circular polarization (CP) through its optical
leakage from CP to linear polarization. The CP of the CMB is predicted from
various sources, such as interactions in the Universe and extension of the
standard model. Interaction with supernova remnants of population III stars is
one of the brightest CP sources. Thus, the observation of the CP of CMB is a
new tool for searching for population III stars. In this paper, we demonstrate
the improved measurement of the leakage coefficient using the transmission
measurement of an actual HWP in the laboratory. We measured the transmittance
of linearly polarized light through the HWP used in \textsc{Polarbear} in the
frequency range of \SIrange{120}{160}{GHz}. We evaluate properties of the HWP
by fitting the data with a physical model using the Markov Chain Monte Carlo
method. We then estimate the band-averaged CP leakage coefficient using the
physical model. We find that the leakage coefficient strongly depends on the
spectra of CP sources. We thus calculate the maximum fractional leakage
coefficient from CP to linear polarization as in the
Rayleigh--Jeans spectrum. The nonzero value shows that \textsc{Polarbear} has
sensitivity to CP. Additionally, because we use the bandpass of detectors
installed in the telescope to calculate the band-averaged values, we also
consider systematic effects in the experiment.Comment: 27 pages, 7 figure
Ultra High Energy Cosmology with POLARBEAR
Observations of the temperature anisotropy of the Cosmic Microwave Background
(CMB) lend support to an inflationary origin of the universe, yet no direct
evidence verifying inflation exists. Many current experiments are focussing on
the CMB's polarization anisotropy, specifically its curl component (called
"B-mode" polarization), which remains undetected. The inflationary paradigm
predicts the existence of a primordial gravitational wave background that
imprints a unique B-mode signature on the CMB's polarization at large angular
scales. The CMB B-mode signal also encodes gravitational lensing information at
smaller angular scales, bearing the imprint of cosmological large scale
structures (LSS) which in turn may elucidate the properties of cosmological
neutrinos. The quest for detection of these signals; each of which is orders of
magnitude smaller than the CMB temperature anisotropy signal, has motivated the
development of background-limited detectors with precise control of systematic
effects. The POLARBEAR experiment is designed to perform a deep search for the
signature of gravitational waves from inflation and to characterize lensing of
the CMB by LSS. POLARBEAR is a 3.5 meter ground-based telescope with 3.8
arcminute angular resolution at 150 GHz. At the heart of the POLARBEAR receiver
is an array featuring 1274 antenna-coupled superconducting transition edge
sensor (TES) bolometers cooled to 0.25 Kelvin. POLARBEAR is designed to reach a
tensor-to-scalar ratio of 0.025 after two years of observation -- more than an
order of magnitude improvement over the current best results, which would test
physics at energies near the GUT scale. POLARBEAR had an engineering run in the
Inyo Mountains of Eastern California in 2010 and will begin observations in the
Atacama Desert in Chile in 2011.Comment: 8 pages, 6 figures, DPF 2011 conference proceeding
The QUIET Instrument
The Q/U Imaging ExperimenT (QUIET) is designed to measure polarization in the
Cosmic Microwave Background, targeting the imprint of inflationary
gravitational waves at large angular scales (~ 1 degree). Between 2008 October
and 2010 December, two independent receiver arrays were deployed sequentially
on a 1.4 m side-fed Dragonian telescope. The polarimeters which form the focal
planes use a highly compact design based on High Electron Mobility Transistors
(HEMTs) that provides simultaneous measurements of the Stokes parameters Q, U,
and I in a single module. The 17-element Q-band polarimeter array, with a
central frequency of 43.1 GHz, has the best sensitivity (69 uK sqrt(s)) and the
lowest instrumental systematic errors ever achieved in this band, contributing
to the tensor-to-scalar ratio at r < 0.1. The 84-element W-band polarimeter
array has a sensitivity of 87 uK sqrt(s) at a central frequency of 94.5 GHz. It
has the lowest systematic errors to date, contributing at r < 0.01. The two
arrays together cover multipoles in the range l= 25-975. These are the largest
HEMT-based arrays deployed to date. This article describes the design,
calibration, performance of, and sources of systematic error for the
instrument
The bolometric focal plane array of the Polarbear CMB experiment
The Polarbear Cosmic Microwave Background (CMB) polarization experiment is
currently observing from the Atacama Desert in Northern Chile. It will
characterize the expected B-mode polarization due to gravitational lensing of
the CMB, and search for the possible B-mode signature of inflationary
gravitational waves. Its 250 mK focal plane detector array consists of 1,274
polarization-sensitive antenna-coupled bolometers, each with an associated
lithographed band-defining filter. Each detector's planar antenna structure is
coupled to the telescope's optical system through a contacting dielectric
lenslet, an architecture unique in current CMB experiments. We present the
initial characterization of this focal plane
Development and characterization of the readout system for POLARBEAR-2
POLARBEAR-2 is a next-generation receiver for precision measurements of the
polarization of the cosmic microwave background (Cosmic Microwave Background
(CMB)). Scheduled to deploy in early 2015, it will observe alongside the
existing POLARBEAR-1 receiver, on a new telescope in the Simons Array on Cerro
Toco in the Atacama desert of Chile. For increased sensitivity, it will feature
a larger area focal plane, with a total of 7,588 polarization sensitive
antenna-coupled Transition Edge Sensor (TES) bolometers, with a design
sensitivity of 4.1 uKrt(s). The focal plane will be cooled to 250 milliKelvin,
and the bolometers will be read-out with 40x frequency domain multiplexing,
with 36 optical bolometers on a single SQUID amplifier, along with 2 dark
bolometers and 2 calibration resistors. To increase the multiplexing factor
from 8x for POLARBEAR-1 to 40x for POLARBEAR-2 requires additional bandwidth
for SQUID readout and well-defined frequency channel spacing. Extending to
these higher frequencies requires new components and design for the LC filters
which define channel spacing. The LC filters are cold resonant circuits with an
inductor and capacitor in series with each bolometer, and stray inductance in
the wiring and equivalent series resistance from the capacitors can affect
bolometer operation. We present results from characterizing these new readout
components. Integration of the readout system is being done first on a small
scale, to ensure that the readout system does not affect bolometer sensitivity
or stability, and to validate the overall system before expansion into the full
receiver. We present the status of readout integration, and the initial results
and status of components for the full array.Comment: Presented at SPIE Astronomical Telescopes and Instrumentation 2014:
Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for
Astronomy VII. Published in Proceedings of SPIE Volume 915
Measurement of the cosmic microwave background polarization lensing power spectrum from two years of POLARBEAR data
We present a measurement of the gravitational lensing deflection power spectrum reconstructed with two seasons of cosmic microwave background polarization data from the POLARBEAR experiment. Observations were taken at 150 GHz from 2012 to 2014 and surveyed three patches of sky totaling 30 square degrees. We test the consistency of the lensing spectrum with a cold dark matter cosmology and reject the no-lensing hypothesis at a confidence of 10.9σ, including statistical and systematic uncertainties. We observe a value of AL = 1.33 ± 0.32 (statistical) ±0.02 (systematic) ±0.07 (foreground) using all polarization lensing estimators, which corresponds to a 24% accurate measurement of the lensing amplitude. Compared to the analysis of the first- year data, we have improved the breadth of both the suite of null tests and the error terms included in the estimation of systematic contamination
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