POLARBEAR-2b (PB-2b) is the second of three cryogenic receivers of the Simons Array cosmic microwave background polarization experiment. PB-2b contains over 7500 transition-edge sensor (TES) ...bolometers cooled to 250 mK and read out using digital frequency-division multiplexing (DfMux). Stray impedance in the DfMux circuit obscures TES characterization and affects TES dynamic behavior. In order to accurately characterize TESs, it is necessary to account for stray impedance in the bias circuit. We define a stray impedance model, and we describe the technique used to measure model parameters in situ and to remove their effects on TES characterization. We use the same model to predict TES dynamic behavior and show good agreement between data and the model.
We are developing multi-chroic antenna-coupled Transition Edge Sensor (TES) bolometer detectors for Cosmic Microwave Background (CMB) polarimetry. Multi-chroic detectors increase focal plane area ...efficiency, and thus the mapping speed per focal plane area, and provide greater discrimination against polarized galactic foregrounds with no increase in weight or cryogenic cost. In each pixel, a silicon lens-coupled dual-polarized sinuous antenna collects photons over a two-octave frequency band. The antenna couples the broadband millimeter wave signal into microstrip transmission lines, and on-chip filter banks split the broadband signal into multiple frequency bands. Separate TES bolometers detect the power in each frequency band and linear polarization state. We will describe the design and performance of these devices and present optical data taken. Our measurements of dual-polarization pixels in multiple frequency bands show beams with percent-level ellipticity, and percent-level cross-polarization leakage. We will also describe the development of large arrays of these multi-chroic pixels. Finally, we will describe kilo-pixel arrays of these detectors planned for the future CMB experiments that will achieve unprecedented mapping speed.
Polarbear-2
(PB-2) is a next-generation receiver that is part of the Simons Array cosmic microwave background (CMB) polarization experiment which is located in the Atacama desert in Northern Chile. ...The primary scientific goals of the Simons Array are a deep search for the CMB B-mode signature of gravitational waves from inflation and the characterization of large-scale structure using its effect on CMB polarization. The PB-2 receiver will deploy with 1897 dual-polarization sinuous antenna-coupled pixels, each with a directly contacting extended hemispherical silicon lens. Every pixel has dual polarization sensitivity in two spectral bands centered at 95 and 150 GHz, for a total of 7588 transition edge sensor bolometers operating at 270 mK. To achieve the PB-2 detector requirements, we developed a broadband anti-reflection (AR) coating for the extended hemispherical lenses that uses two molds to apply two layers of epoxy, Stycast 1090 and Stycast 2850FT. Our measurements of the absorption loss from the AR coating on a flat surface at cryogenic temperatures show less than 1 % absorption, and the coating has survived multiple thermal cycles. We can control the diameter of the coating within 25
μ
m and translation errors are within 25
μ
m in all directions, which results in less than 1 % decrease in transmittance. We also find the performance of the AR-coated lens matches very well with simulations.
The POLARBEAR-2 Experiment Suzuki, A.; Ade, P.; Akiba, Y. ...
Journal of low temperature physics,
09/2014, Letnik:
176, Številka:
5-6
Journal Article
Recenzirano
Odprti dostop
We present an overview of the design and development of the POLARBEAR-2 experiment. The POLARBEAR-2 experiment is a cosmic microwave background polarimetry experiment, which aims to characterize the ...small angular scale B-mode signal due to gravitational lensing and search for the large angular scale B-mode signal from inflationary gravitational waves. The experiment will have a 365 mm diameter multi-chroic focal plane filled with 7,588 polarization sensitive antenna-coupled Transition Edge Sensor bolometers and will observe at 95 and 150 GHz. The focal plane is cooled to 250 mK. The bolometers will be read-out by SQUIDs with
32
×
frequency domain multiplexing. The experiment will utilize high purity alumina lenses and thermal filters to achieve the required high optical throughput. A continuously rotating, cooled half-wave plate will be used to give stringent control over systematic errors. The experiment is designed to achieve a noise equivalent temperature of 5.7
μ
K
s
, and this allows us to constrain the signal from the inflationary primordial gravitational corresponding to a tensor-to-scalar ratio of
r
=
0.01
(
2
σ
). POLARBEAR-2 will also be able to put a constraint on the sum of neutrino masses to 90 meV (
1
σ
) with POLARBEAR-2 data alone and 65 meV (
1
σ
) when combined with the Planck satellite. We plan to start observations in 2014 in the Atacama Desert in Chile.
Using 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.
Abstract
We report an improved measurement of the degree-scale cosmic microwave background
B
-mode angular-power spectrum over 670 deg
2
sky area at 150 GHz with P
olarbear
. In the original analysis ...of the data, errors in the angle measurement of the continuously rotating half-wave plate, a polarization modulator, caused significant data loss. By introducing an angle-correction algorithm, the data volume is increased by a factor of 1.8. We report a new analysis using the larger data set. We find the measured
B
-mode spectrum is consistent with the ΛCDM model with Galactic dust foregrounds. We estimate the contamination of the foreground by cross-correlating our data and Planck 143, 217, and 353 GHz measurements, where its spectrum is modeled as a power law in angular scale and a modified blackbody in frequency. We place an upper limit on the tensor-to-scalar ratio
r
< 0.33 at 95% confidence level after marginalizing over the foreground parameters.
ABSTRACT 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.
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