The third-generation South Pole Telescope camera is designed to measure the cosmic microwave background across three frequency bands (centered at 95, 150 and 220 GHz) with ~ 16,000 transition-edge ...sensor (TES) bolometers. Each multichroic array element on a detector wafer has a broadband sinuous antenna that couples power to six TESs, one for each of the three observing bands and both polarizations, via lumped element filters. Ten detector wafers populate the detector array, which is coupled to the sky via a large-aperture optical system. Here we present the frequency band characterization with Fourier transform spectroscopy, measurements of optical time constants, beam properties, and optical and polarization efficiencies of the detector array. The detectors have frequency bands consistent with our simulations and have high average optical efficiency which is 86, 77 and 66% for the 95, 150 and 220 GHz detectors. The time constants of the detectors are mostly between 0.5 and 5 ms. The beam is round with the correct size, and the polarization efficiency is more than 90% for most of the bolometers.
The South Pole Telescope third-generation (SPT-3G) receiver was installed during the austral summer of 2016–2017. It is designed to measure the cosmic microwave background across three frequency ...bands centered at 95, 150, and 220 GHz. The SPT-3G receiver has ten focal plane modules, each with 269 pixels. Each pixel features a broadband sinuous antenna coupled to a niobium microstrip transmission line. In-line filters define the desired band-passes before the signal is coupled to six bolometers with Ti/Au/Ti/Au transition edge sensors (three bands×two polarizations). In total, the SPT-3G receiver is composed of 16,000 detectors, which are read out using a 68× frequency-domain multiplexing scheme. In this paper, we present the process employed in fabricating the detector arrays.
Here, we present a measurement of gravitational lensing over 1500deg2 of the Southern sky using SPT-3G temperature data at 95 GHz and 150 GHz taken in 2018. The lensing amplitude relative to a ...fiducial Planck 2018 Lambda cold dark matter ( Λ CDM ) cosmology is found to be 1.020±0.060 , excluding instrumental and astrophysical systematic uncertainties. We conduct extensive systematic and null tests to check the robustness of the lensing measurements, and report a minimum-variance combined lensing power spectrum over angular multipoles of 50<L<2000 , which we use to constrain cosmological models. When analyzed alone and jointly with primary cosmic microwave background (CMB) spectra within the Λ CDM model, our lensing amplitude measurements are consistent with measurements from SPT-SZ, SPTpol, ACT, and Planck. Incorporating loose priors on the baryon density and other parameters including uncertainties on a foreground bias template, we obtain a 1σ constraint on σ8 Ω m 0.25=0.595±0.026 using the SPT-3G 2018 lensing data alone, where σ8 is a common measure of the amplitude of structure today and Ω m is the matter density parameter. Combining SPT-3G 2018 lensing measurements with baryon acoustic oscillation (BAO) data, we derive parameter constraints of σ8=0.810±0.033 , S8≡σ8 ( Ω m /0.3 ) 0.5= 0.836±0.039 , and Hubble constant H0=68.8-1.6+1.3km s -1Mpc-1 . Our preferred S8 value is higher by 1.6 to 1.8σ compared to cosmic shear measurements from DES-Y3, HSC-Y3, and KiDS-1000 at lower redshift and smaller scales. We combine our lensing data with CMB anisotropy measurements from both SPT-3G and Planck to constrain extensions of Λ CDM . Using CMB anisotropy and lensing measurements from SPT-3G only, we provide independent constraints on the spatial curvature of Ω K=0.014-0.026+0.023 (95% C.L.) and the dark energy density of Ω Λ =0.722-0.026+0.031 (68% C.L.). When combining SPT-3G lensing data with SPT-3G CMB anisotropy and BAO data, we find an upper limit on the sum of the neutrino masses of Σmν<0.30eV (95% C.L.). Due to the diferent combination of angular scales and sky area, this lensing analysis provides an independent check on lensing measurements by ACT and Planck.
Kinetic inductance detectors (KIDs) are a promising technology for astronomical observations over a wide range of wavelengths in the mm and sub-mm regime. Simple fabrication, in as little as one ...lithographic layer, and passive frequency-domain multiplexing, with readout of up to 1000 pixels on a single line with a single cold amplifier, make KIDs an attractive solution for high-pixel-count detector arrays. We are developing an array that optimizes KIDs for optical frequencies near 100GHz to expand their usefulness in mm-wave applications, with a particular focus on CMBB-mode measurement efforts in association with the QUBIC telescope. We have designed, fabricated, and tested a 20-pixel prototype array using a simple quasi lumped microstrip design and pulsed DC reactive magnetron-sputtered TiNTiTiN trilayer resonators, optimized for detecting 100GHz (3mm) signals. Here we present a discussion of design considerations for the array, as well as preliminary detector characterization measurements and results from a study of TiN trilayer properties.
We study the polarization properties of extragalactic sources at 95 and 150 GHz in the SPTpol 500 deg2 survey. We estimate the polarized power by stacking maps at known source positions, and correct ...for noise bias by subtracting the mean polarized power at random positions in the maps. We show that the method is unbiased using a set of simulated maps with similar noise properties to the real SPTpol maps. We find a flux-weighted mean-squared polarization fraction $\langle$p2$\rangle$ = 8.9 ± 1.1 × 10-4 at 95 GHz and 6.9 ± 1.1 × 10-4 at 150 GHz for the full sample. This is consistent with the values obtained for a subsample of active galactic nuclei. For dusty sources, we find 95 percent upper limits of $\langle$p2$\rangle$95 < 16.9 × 10-3 and $\langle$p2$\rangle$150 < 2.6 × 10-3. We find no evidence that the polarization fraction depends on the source flux or observing frequency. The 1σ upper limit on measured mean-squared polarization fraction at 150 GHz implies that extragalactic foregrounds will be subdominant to the CMB E and B mode polarization power spectra out to at least ℓ ≲ 5700 (ℓ ≲ 4700) and ℓ ≲ 5300 (ℓ ≲ 3600), respectively, at 95 (150) GHz.
Abstract
We present cosmological constraints based on the cosmic microwave background (CMB) lensing potential power spectrum measurement from the recent 500 deg
2
SPTpol
survey, the most precise CMB ...lensing measurement from the ground to date. We fit a flat ΛCDM model to the reconstructed lensing power spectrum alone and in addition with other data sets: baryon acoustic oscillations (BAO), as well as primary CMB spectra from
Planck
and
SPTpol
. The cosmological constraints based on
SPTpol
and
Planck
lensing band powers are in good agreement when analyzed alone and in combination with
Planck
full-sky primary CMB data. With weak priors on the baryon density and other parameters, the
SPTpol
CMB lensing data alone provide a 4% constraint on
. Jointly fitting with BAO data, we find
,
, and
, up to
away from the central values preferred by
Planck
lensing + BAO. However, we recover good agreement between
SPTpol
and
Planck
when restricting the analysis to similar scales. We also consider single-parameter extensions to the flat ΛCDM model. The
SPTpol
lensing spectrum constrains the spatial curvature to be
and the sum of the neutrino masses to be
eV at 95% C.L. (with
Planck
primary CMB and BAO data), in good agreement with the
Planck
lensing results. With the differences in the signal-to-noise ratio of the lensing modes and the angular scales covered in the lensing spectra, this analysis represents an important independent check on the full-sky
Planck
lensing measurement.
PDF
