125 research outputs found
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
Internal delensing of cosmic microwave background polarization B-Modes with the POLARBEAR experiment
International audienceUsing only cosmic microwave background polarization data from the polarbear experiment, we measure B-mode polarization delensing on subdegree scales at more than 5σ significance. We achieve a 14% B-mode power variance reduction, the highest to date for internal delensing, and improve this result to 22% by applying for the first time an iterative maximum a posteriori delensing method. Our analysis demonstrates the capability of internal delensing as a means of improving constraints on inflationary models, paving the way for the optimal analysis of next-generation primordial B-mode experiments
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
Development of the Low Frequency Telescope Focal Plane Detector Modules for LiteBIRD
LiteBIRD is a JAXA-led strategic large-class satellite mission designed to
measure the polarization of the cosmic microwave background and Galactic
foregrounds from 34 to 448 GHz across the entire sky from L2 in the late 2020s.
The scientific payload includes three telescopes which are called the low-,
mid-, and high-frequency telescopes each with their own receiver that covers a
portion of the mission's frequency range. The low frequency telescope will map
synchrotron radiation from the Galactic foreground and the cosmic microwave
background. We discuss the design, fabrication, and characterization of the
low-frequency focal plane modules for low-frequency telescope, which has a
total bandwidth ranging from 34 to 161 GHz. There will be a total of 4
different pixel types with 8 overlapping bands to cover the full frequency
range. These modules are housed in a single low-frequency focal plane unit
which provides thermal isolation, mechanical support, and radiative baffling
for the detectors. The module design implements multi-chroic lenslet-coupled
sinuous antenna arrays coupled to transition edge sensor bolometers read out
with frequency-domain mulitplexing. While this technology has strong heritage
in ground-based cosmic microwave background experiments, the broad frequency
coverage, low optical loading conditions, and the high cosmic ray background of
the space environment require further development of this technology to be
suitable for LiteBIRD. In these proceedings, we discuss the optical and
bolometeric characterization of a triplexing prototype pixel with bands
centered on 78, 100, and 140 GHz.Comment: SPIE Astronomical Telescope + Instrumentation (AS22
Measurements of tropospheric ice clouds with a ground-based CMB polarization experiment, POLARBEAR
The polarization of the atmosphere has been a long-standing concern for ground-based experiments targeting cosmic microwave background (CMB) polarization. Ice crystals in upper tropospheric clouds scatter thermal radiation from the ground and produce a horizontally polarized signal. We report a detailed analysis of the cloud signal using a ground-based CMB experiment, Polarbear, located at the Atacama desert in Chile and observing at 150 GHz. We observe horizontally polarized temporal increases of low-frequency fluctuations ("polarized bursts," hereafter) of 720.1 K when clouds appear in a webcam monitoring the telescope and the sky. The hypothesis of no correlation between polarized bursts and clouds is rejected with >24\u3c3 statistical significance using three years of data. We consider many other possibilities including instrumental and environmental effects, and find no reasons other than clouds that can explain the data better. We also discuss the impact of the cloud polarization on future ground-based CMB polarization experiments
Conceptual Design of the Modular Detector and Readout System for the CMB-S4 survey experiment
We present the conceptual design of the modular detector and readout system
for the Cosmic Microwave Background Stage 4 (CMB-S4) ground-based survey
experiment. CMB-S4 will map the cosmic microwave background (CMB) and the
millimeter-wave sky to unprecedented sensitivity, using 500,000 superconducting
detectors observing from Chile and Antarctica to map over 60 percent of the
sky. The fundamental building block of the detector and readout system is a
detector module package operated at 100 mK, which is connected to a readout and
amplification chain that carries signals out to room temperature. It uses
arrays of feedhorn-coupled orthomode transducers (OMT) that collect optical
power from the sky onto dc-voltage-biased transition-edge sensor (TES)
bolometers. The resulting current signal in the TESs is then amplified by a
two-stage cryogenic Superconducting Quantum Interference Device (SQUID) system
with a time-division multiplexer to reduce wire count, and matching
room-temperature electronics to condition and transmit signals to the data
acquisition system. Sensitivity and systematics requirements are being
developed for the detector and readout system over a wide range of observing
bands (20 to 300 GHz) and optical powers to accomplish CMB-S4's science goals.
While the design incorporates the successes of previous generations of CMB
instruments, CMB-S4 requires an order of magnitude more detectors than any
prior experiment. This requires fabrication of complex superconducting circuits
on over 10 square meters of silicon, as well as significant amounts of
precision wiring, assembly and cryogenic testing.Comment: 25 pages, 15 figures, presented at and published in the proceedings
of SPIE Astronomical Telescopes and Instrumentation 202
Modeling Atmospheric Emission for CMB Ground-based Observations
Atmosphere is one of the most important noise sources for ground-based cosmic microwave background (CMB) experiments. By increasing optical loading on the detectors, it amplifies their effective noise, while its fluctuations introduce spatial and temporal correlations between detected signals. We present a physically motivated 3D-model of the atmosphere total intensity emission in the millimeter and sub-millimeter wavelengths. We derive a new analytical estimate for the correlation between detectors time-ordered data as a function of the instrument and survey design, as well as several atmospheric parameters such as wind, relative humidity, temperature and turbulence characteristics. Using an original numerical computation, we examine the effect of each physical parameter on the correlations in the time series of a given experiment. We then use a parametric-likelihood approach to validate the modeling and estimate atmosphere parameters from the POLARBEAR-I project first season data set. We derive a new 1.0% upper limit on the linear polarization fraction of atmospheric emission. We also compare our results to previous studies and weather station measurements. The proposed model can be used for realistic simulations of future ground-based CMB observations
Cross-correlation of CMB polarization lensing with High-z submillimeter Herschel-ATLAS galaxies
We report a 4.8σ measurement of the cross-correlation signal between the cosmic microwave background (CMB) lensing convergence reconstructed from measurements of the CMB polarization made by the Polarbear experiment and the infrared-selected galaxies of the Herschel-ATLAS survey. This is the first measurement of its kind
The POLARBEAR-2 and Simons Array Focal Plane Fabrication Status
We present on the status of POLARBEAR-2 A (PB2-A) focal plane fabrication.
The PB2-A is the first of three telescopes in the Simon Array (SA), which is an
array of three cosmic microwave background (CMB) polarization sensitive
telescopes located at the POLARBEAR (PB) site in Northern Chile. As the
successor to the PB experiment, each telescope and receiver combination is
named as PB2-A, PB2-B, and PB2-C. PB2-A and -B will have nearly identical
receivers operating at 90 and 150 GHz while PB2-C will house a receiver
operating at 220 and 270 GHz. Each receiver contains a focal plane consisting
of seven close-hex packed lenslet coupled sinuous antenna transition edge
sensor bolometer arrays. Each array contains 271 di-chroic optical pixels each
of which have four TES bolometers for a total of 7588 detectors per receiver.
We have produced a set of two types of candidate arrays for PB2-A. The first we
call Version 11 (V11) and uses a silicon oxide (SiOx) for the transmission
lines and cross-over process for orthogonal polarizations. The second we call
Version 13 (V13) and uses silicon nitride (SiNx) for the transmission lines and
cross-under process for orthogonal polarizations. We have produced enough of
each type of array to fully populate the focal plane of the PB2-A receiver. The
average wirebond yield for V11 and V13 arrays is 93.2% and 95.6% respectively.
The V11 arrays had a superconducting transition temperature (Tc) of 452 +/- 15
mK, a normal resistance (Rn) of 1.25 +/- 0.20 Ohms, and saturations powers of
5.2 +/- 1.0 pW and 13 +/- 1.2 pW for the 90 and 150 GHz bands respectively. The
V13 arrays had a superconducting transition temperature (Tc) of 456 +/-6 mK, a
normal resistance (Rn) of 1.1 +/- 0.2 Ohms, and saturations powers of 10.8 +/-
1.8 pW and 22.9 +/- 2.6 pW for the 90 and 150 GHz bands respectively
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