Superconducting nanowire single photon detectors are capable of single-photon detection across a large spectral range with near unity detection efficiency, picosecond timing jitter, and sub-10 μm ...position resolution, at rates as high as 109 counts/s. In an effort to bring this technology into nuclear physics experiments, we fabricate niobium nitride (NbN) nanowire detectors using ion beam assisted sputtering and test their performance in strong magnetic fields. We demonstrate that these devices are capable of detection of 400 nm wavelength photons with saturated internal quantum efficiency at temperatures of 3 K and in magnetic fields of up to 5 T at high count rates and with nearly zero dark counts.
We present a measurement of the cosmic microwave background lensing potential using 500 deg2 of 150 GHz data from the SPTpol receiver on the South Pole Telescope. The lensing potential is ...reconstructed with signal-to-noise per mode greater than unity at lensing multipoles L 250, using a quadratic estimator on a combination of cosmic microwave background temperature and polarization maps. We report measurements of the lensing potential power spectrum in the multipole range of 100 < L < 2000 from sets of temperature-only (T), polarization-only (POL), and minimum-variance (MV) estimators. We measure the lensing amplitude by taking the ratio of the measured spectrum to the expected spectrum from the best-fit Λ cold dark matter model to the Planck 2015 TT + low P + lensing data set. For the minimum-variance estimator, we find A MV = 0.944 0.058 ( Stat . ) 0.025 ( Sys . ) ; restricting to only polarization data, we find A POL = 0.906 0.090 ( Stat . ) 0.040 ( Sys . ) . Considering statistical uncertainties alone, this is the most precise polarization-only lensing amplitude constraint to date (10.1 ) and is more precise than our temperature-only constraint. We perform null tests and consistency checks and find no evidence for significant contamination.
Abstract
We perform the first simultaneous Bayesian parameter inference and optimal reconstruction of the gravitational lensing of the cosmic microwave background (CMB), using 100 deg
2
of ...polarization observations from the SPTpol receiver on the South Pole Telescope. These data reach noise levels as low as 5.8
μ
K arcmin in polarization, which are low enough that the typically used quadratic estimator (QE) technique for analyzing CMB lensing is significantly suboptimal. Conversely, the Bayesian procedure extracts all lensing information from the data and is optimal at any noise level. We infer the amplitude of the gravitational lensing potential to be
A
ϕ
=
0.949
±
0.122
using the Bayesian pipeline, consistent with our QE pipeline result, but with 17% smaller error bars. The Bayesian analysis also provides a simple way to account for systematic uncertainties, performing a similar job as frequentist “bias hardening” or linear bias correction, and reducing the systematic uncertainty on
A
ϕ
due to polarization calibration from almost half of the statistical error to effectively zero. Finally, we jointly constrain
A
ϕ
along with
A
L
, the amplitude of lensing-like effects on the CMB power spectra, demonstrating that the Bayesian method can be used to easily infer parameters both from an optimal lensing reconstruction and from the delensed CMB, while exactly accounting for the correlation between the two. These results demonstrate the feasibility of the Bayesian approach on real data, and pave the way for future analysis of deep CMB polarization measurements with SPT-3G, Simons Observatory, and CMB-S4, where improvements relative to the QE can reach 1.5 times tighter constraints on
A
ϕ
and seven times lower effective lensing reconstruction noise.
A microwave kinetic inductance detector (MKID) is a superconducting pair breaking detector that offers a number of unique advantages for realizing large-format arrays of ultra-sensitive detectors, ...such as inherent multiplexibility and relative ease of fabrication. With the detection threshold being set by the Cooper pair binding energy, and correspondingly, the superconducting critical temperature (
T
c
), typically well-understood MKID materials such as aluminum (Al) present a lower limit on the operating frequency. Aluminum manganese (Al-Mn) is a promising candidate material for MKIDs because it can be fabricated with nearly identical processing as pure Al, but allows for control of the
T
c
with varying levels of Mn doping or post-deposition heat treatment. We present initial results from an early characterization of AlMn using a series of lumped-element superconducting microwave resonators, including measurements of
T
c
, internal quality factor, and noise performance over a range of Mn doping.
We present cosmological constraints based on the cosmic microwave background (CMB) lensing potential power spectrum measurement from the recent 500 deg2 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.
In this work, we present measurements of the E-mode (EE) polarization power spectrum and temperature-E-mode (TE) cross-power spectrum of the cosmic microwave background using data collected by ...SPT-3G, the latest instrument installed on the South Pole Telescope. This analysis uses observations of a 1500 deg2 region at 95, 150, and 220 GHz taken over a four-month period in 2018. We report binned values of the EE and TE power spectra over the angular multipole range 300≤ℓ<3000, using the multifrequency data to construct six semi-independent estimates of each power spectrum and their minimum-variance combination. These measurements improve upon the previous results of SPTpol across the multipole ranges 300 ≤ ℓ ≤ 1400 for EE and 300 ≤ ℓ ≤ 1700 for TE, resulting in constraints on cosmological parameters comparable to those from other current leading ground-based experiments. We find that the SPT-3G data set is well fit by a ΛCDM cosmological model with parameter constraints consistent with those from Planck and SPTpol data. From SPT-3G data alone, we find H0=68.8±1.5 km s-1 Mpc-1 and σ8=0.789±0.016, with a gravitational lensing amplitude consistent with the ΛCDM prediction (AL=0.98±0.12). We combine the SPT-3G and the Planck data sets and obtain joint constraints on the ΛCDM model. The volume of the 68% confidence region in six-dimensional ΛCDM parameter space is reduced by a factor of 1.5 compared to Planck-only constraints, with no significant shifts in central values. We note that the results presented here are obtained from data collected during just half of a typical observing season with only part of the focal plane operable, and that the active detector count has since nearly doubled for observations made with SPT-3G after 2018.
Direct detection of nuclear scatterings of sub-GeV Dark Matter (DM) particles favors low-Z nuclei. Hydrogen nucleus, which has a single proton, provides the best kinematic match to a light dark ...matter particle. The characteristic nuclear recoil energy is boosted by a factor of a few tens from those for larger nuclei used in traditional Weakly Interacting Massive Particle (WIMP) searches. Furthermore, hydrogen is optimal not only for spin-independent nuclear scatterings of sub-GeV DM, but also for spin-dependent nuclear scatterings, where large parameter space remains unconstrained. In this paper, we first introduce hydrogen-rich crystals, which include water ice, acetylene, anthracene, trans-stilbene, and naphthalene. These crystals emit two classes of signals under kinetic excitations. One class of the signals is infrared photons, which are from optically active fundamental vibrational modes of molecules and are at corresponding characteristic wavelengths. The other is acoustic phonons, and optical phonons that decay into acoustic phonons. We then discuss the technical status and future researches of low-Tc Transition-Edge Sensor (TES) detectors, which measure single infrared photons and a small flux of acoustic phonons with desirable sensitivities. With theoretical modeling to select the hydrogen-rich crystals for the optimized science reach, development of ultra-sensitive low-Tc TES detectors for readout, and experimentally characterizing transport properties of photons and phonons in the selected hydrogen-rich crystals, a direct detection experiment can be built for measuring the large unexplored parameter space of light DM particles.
The SPTpol Extended Cluster Survey Bleem, L. E.; Bocquet, S.; Stalder, B. ...
The Astrophysical journal. Supplement series,
03/2020, Letnik:
247, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We describe the observations and resultant galaxy cluster catalog from the 2770 deg2 SPTpol Extended Cluster Survey (SPT-ECS). Clusters are identified via the Sunyaev-Zel'dovich (SZ) effect and ...confirmed with a combination of archival and targeted follow-up data, making particular use of data from the Dark Energy Survey (DES). With incomplete follow-up we have confirmed as clusters 244 of 266 candidates at a detection significance ≥ 5 and an additional 204 systems at 4 < < 5. The confirmed sample has a median mass of and a median redshift of z = 0.49, and we have identified 44 strong gravitational lenses in the sample thus far. Radio data are used to characterize contamination to the SZ signal; the median contamination for confirmed clusters is predicted to be ∼1% of the SZ signal at the > 4 threshold, and <4% of clusters have a predicted contamination >10% of their measured SZ flux. We associate SZ-selected clusters, from both SPT-ECS and the SPT-SZ survey, with clusters from the DES redMaPPer sample, and we find an offset distribution between the SZ center and central galaxy in general agreement with previous work, though with a larger fraction of clusters with significant offsets. Adopting a fixed Planck-like cosmology, we measure the optical richness-SZ mass ( ) relation and find it to be 28% shallower than that from a weak-lensing analysis of the DES data-a difference significant at the 4 level-with the relations intersecting at λ = 60. The SPT-ECS cluster sample will be particularly useful for studying the evolution of massive clusters and, in combination with DES lensing observations and the SPT-SZ cluster sample, will be an important component of future cosmological analyses.
This work presents a suite of measurement techniques for characterizing the dielectric loss tangent across a wide frequency range from <inline-formula><tex-math ...notation="LaTeX">\sim</tex-math></inline-formula>1 GHz to 150 GHz using the same test chip. In the first method, we fit data from a microwave resonator at different temperatures to a model that captures the two-level system (TLS) response to extract and characterize both the real and imaginary components of the dielectric loss. The inverse of the internal quality factor is a second measure of the overall loss of the resonator, where TLS loss through the dielectric material is typically the dominant source. The third technique is a differential optical measurement at 150 GHz. The same antenna feeds two microstrip lines with different lengths that terminate in two microwave kinetic inductance detectors (MKIDs). The difference in the detector response is used to estimate the loss per unit length of the microstrip line. Our results suggest a larger loss for SiN<inline-formula><tex-math notation="LaTeX">_{x}</tex-math></inline-formula> at 150 GHz of <inline-formula><tex-math notation="LaTeX">{\mathbf{\tan \delta \sim 4\times 10^{-3}}}</tex-math></inline-formula> compared to <inline-formula><tex-math notation="LaTeX">{\mathbf{2.0\times 10^{-3}}}</tex-math></inline-formula> and <inline-formula><tex-math notation="LaTeX">{\gtrsim \mathbf{1\times 10}^{\mathbf{-3}}}</tex-math></inline-formula> measured at <inline-formula><tex-math notation="LaTeX">\sim</tex-math></inline-formula>1 GHz using the other two methods. These measurement techniques can be applied to other dielectrics by adjusting the microstrip lengths to provide enough optical efficiency contrast and other mm/sub-mm frequency ranges by tuning the antenna and feedhorn accordingly.
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