Abstract
Monitoring motion originating from ultra low-temperature cooling systems like cryocoolers is important for vibration sensitive cryogenic experiments like KAGRA. Since no high sensitivity ...commercial cryogenic accelerometers are available, we developed a compact self-calibrating accelerometer with a Michelson interferometer readout for cryogenic use. Change in calibration factor and drop in interferometer output originating from temperature drop were the main concerns which were tackled. Sensitivity of
3.38
×
10
−
11
m/
H
z
at 1 Hz was achieved at 300 K. The accelerometer was tested inside the KAGRA cryostat; showed stable operation down to 12 K in 0.1–100 Hz band with only 1% visibility drop. Our accelerometer can be employed in low vibration cryogenic environment for a multitude of applications.
Abstract
KAGRA uses cryogenics to cool its sapphire test masses down to 20 K to reduce the thermal noise. However, cryocooler vibration and structural resonances of the cryostat couple to the test ...mass and can contaminate the detector sensitivity. We performed vibration analysis of the cooling system at cryogenic temperature to study its impact on detector sensitivity. Our measurements show shield vibration below 1 Hz is not impacted by cryocooler operation or structural resonances and is dominated by ground motion. The noise floor of the shield in the range 1–100 Hz was observed to be 2–3 orders of magnitude larger than seismic motion even without cryocooler operation. The operation of cryocoolers does not change the noise floor, but 2 Hz peaks and their harmonics were observed over the entire spectrum (1–100 Hz). These results were used to calculate the coupling of cooling system vibration to the test mass. We conclude that vibration from the cooling system does not limit KAGRA design sensitivity.
We present an overview of the design and status of the
Polarbear
-2 and the Simons Array experiments.
Polarbear
-2 is a cosmic microwave background polarimetry experiment which aims to characterize ...the arc-minute angular scale B-mode signal from weak gravitational lensing and search for the degree angular scale B-mode signal from inflationary gravitational waves. The receiver has a 365 mm diameter focal plane cooled to 270 mK. The focal plane is filled with 7588 dichroic lenslet–antenna-coupled polarization sensitive transition edge sensor (TES) bolometric pixels that are sensitive to 95 and 150 GHz bands simultaneously. The TES bolometers are read-out by SQUIDs with 40 channel frequency domain multiplexing. Refractive optical elements are made with high-purity alumina to achieve high optical throughput. The receiver is designed to achieve noise equivalent temperature of 5.8
μ
K
CMB
s
in each frequency band.
Polarbear
-2 will deploy in 2016 in the Atacama desert in Chile. The Simons Array is a project to further increase sensitivity by deploying three
Polarbear
-2 type receivers. The Simons Array will cover 95, 150, and 220 GHz frequency bands for foreground control. The Simons Array will be able to constrain tensor-to-scalar ratio and sum of neutrino masses to
σ
(
r
)
=
6
×
10
-
3
at
r
=
0.1
and
∑
m
ν
(
σ
=
1
)
to 40 meV.
Gravitational lensing due to the large-scale distribution of matter in the cosmos distorts the primordial cosmic microwave background (CMB) and thereby induces new, small-scale B-mode polarization. ...This signal carries detailed information about the distribution of all the gravitating matter between the observer and CMB last scattering surface. We report the first direct evidence for polarization lensing based on purely CMB information, from using the four-point correlations of even- and odd-parity E- and B-mode polarization mapped over ∼30 square degrees of the sky measured by the POLARBEAR experiment. These data were analyzed using a blind analysis framework and checked for spurious systematic contamination using null tests and simulations. Evidence for the signal of polarization lensing and lensing B modes is found at 4.2σ (stat+sys) significance. The amplitude of matter fluctuations is measured with a precision of 27%, and is found to be consistent with the Lambda cold dark matter cosmological model. This measurement demonstrates a new technique, capable of mapping all gravitating matter in the Universe, sensitive to the sum of neutrino masses, and essential for cleaning the lensing B-mode signal in searches for primordial gravitational waves.
We reconstruct the gravitational lensing convergence signal from cosmic microwave background (CMB) polarization data taken by the Polarbear experiment and cross-correlate it with cosmic infrared ...background maps from the Herschel satellite. From the cross spectra, we obtain evidence for gravitational lensing of the CMB polarization at a statistical significance of 4.0σ and indication of the presence of a lensing B-mode signal at a significance of 2.3σ. We demonstrate that our results are not biased by instrumental and astrophysical systematic errors by performing null tests, checks with simulated and real data, and analytical calculations. This measurement of polarization lensing, made via the robust cross-correlation channel, not only reinforces POLARBEAR auto-correlation measurements, but also represents one of the early steps towards establishing CMB polarization lensing as a powerful new probe of cosmology and astrophysics.
KAGRA is a large scale cryogenic gravitational wave telescope currently under construction in Japan. The detector is located 200 m underground in the Kamioka mine and will employ cryogenic ...technologies to achieve high sensitivity. The mirrors of the interferometer will be in the form of multiple pendulums and the final stages will employ cryogenic sapphire suspension system operating at 20 Kelvin. In this paper we report the ongoing activities of the cryogenic payload group involved in the design and fabrication of the cryogenic payload system for the KAGRA detector
Deployment of Polarbear-2A Kaneko, Daisuke; Adachi, S.; Ade, P. A. R. ...
Journal of low temperature physics,
05/2020, Letnik:
199, Številka:
3-4
Journal Article
Recenzirano
Odprti dostop
Polarbear
-2A is the first of three receivers in the Simons array, a cosmic microwave background experiment located on the Atacama Plateau in Chile.
Polarbear
-2A was deployed and achieved the first ...light in January 2019 by mapping the microwave emission from planet observations. Commissioning work is underway to prepare the receiver for science observations.
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