190 research outputs found
A Comparison of Fundamental Noise in Kinetic Inductance Detectors and Transition Edge Sensors for Millimeter-wave Applications
Kinetic inductance detectors (KIDs) show promise as a competitive technology
for astronomical observations over a wide range of wavelengths. We are
interested in comparing the fundamental limitations to the sensitivity of KIDs
with that of transition edge sensors (TESs) at millimeter wavelengths,
specifically over the wavelengths required for studies of the Cosmic Microwave
Background (CMB). We calculate the total fundamental noise arising from optical
and thermal excitations in TESs and KIDs for a variety of bath temperatures and
optical loading scenarios for applications at millimeter wavelengths. Special
consideration is given to the case of ground-based observations of 100 GHz
radiation with a 100 mK bath temperature, conditions consistent with the
planned second module of the QUBIC telescope, a CMB instrument. Under these
conditions, a titanium nitride KID with optimized critical temperature pays a
few percent noise penalty compared to a typical optimized TES.Comment: 6 pages, 2 figures, Proceedings of 15th International Workshop on Low
Temperature Detectors (LTD-15, Pasadena, California, June 2013), To be
published in the Journal of Low Temperature Physics (JLTP
Hello! Peaches!
https://digitalcommons.library.umaine.edu/mmb-vp/1445/thumbnail.jp
Properties of Superconducting Mo, Mo2n and Trilayer Mo2n-Mo-Mo2n Thin Films
We present measurements of the properties of thin film superconducting Mo, Mo2N and Mo2N/Mo/Mo2N trilayers of interest for microwave kinetic inductance detector (MKID) applications. Using microwave resonator devices, we investigate the transition temperature, energy gaps, kinetic inductance, and internal quality factors of these materials. We present an Usadel-based interpretation of the trilayer transition temperature as a function of trilayer thicknesses, and a 2-gap interpretation to understand the change in kinetic inductance and internal resonance quality factor (Q) as a function of temperature
Design and Bolometer Characterization of the SPT-3G First-year Focal Plane
During the austral summer of 2016-17, the third-generation camera, SPT-3G,
was installed on the South Pole Telescope, increasing the detector count in the
focal plane by an order of magnitude relative to the previous generation.
Designed to map the polarization of the cosmic microwave background, SPT-3G
contains ten 6-in-hexagonal modules of detectors, each with 269 trichroic and
dual-polarization pixels, read out using 68x frequency-domain multiplexing.
Here we discuss design, assembly, and layout of the modules, as well as early
performance characterization of the first-year array, including yield and
detector properties.Comment: Conference proceeding for Low Temperature Detectors 2017. Accepted
for publication: 27 August 201
Measurements of the Temperature and E-Mode Polarization of the CMB from 500 Square Degrees of SPTpol Data
We present measurements of the -mode polarization angular auto-power
spectrum () and temperature--mode cross-power spectrum () of the
cosmic microwave background (CMB) using 150 GHz data from three seasons of
SPTpol observations. We report the power spectra over the spherical harmonic
multipole range , and detect nine acoustic peaks in the
spectrum with high signal-to-noise ratio. These measurements are the most
sensitive to date of the and power spectra at and , respectively. The observations cover 500 deg, a fivefold increase
in area compared to previous SPTpol analyses, which increases our sensitivity
to the photon diffusion damping tail of the CMB power spectra enabling tighter
constraints on \LCDM model extensions. After masking all sources with
unpolarized flux mJy we place a 95% confidence upper limit on residual
polarized point-source power of at , suggesting that the damping tail
dominates foregrounds to at least with modest source masking. We
find that the SPTpol dataset is in mild tension with the model
(), and different data splits prefer parameter values that differ
at the level. When fitting SPTpol data at we
find cosmological parameter constraints consistent with those for
temperature. Including SPTpol data at results in a preference for
a higher value of the expansion rate (H_0 = 71.3 \pm
2.1\,\mbox{km}\,s^{-1}\mbox{Mpc}^{-1} ) and a lower value for present-day
density fluctuations ().Comment: Updated to match version accepted to ApJ. 34 pages, 17 figures, 6
table
MRI texture analysis of subchondral bone at the tibial plateau
OBJECTIVES: To determine the feasibility of MRI texture analysis as a method of quantifying subchondral bone architecture in knee osteoarthritis (OA).  METHODS: Asymptomatic subjects aged 20-30 (group 1, n = 10), symptomatic patients aged 40-50 (group 2, n = 10) and patients scheduled for knee replacement aged 55-85 (group 3, n = 10) underwent high spatial resolution T1-weighted coronal 3T knee MRI. Regions of interest were created in the medial (MT) and lateral (LT) tibial subchondral bone from which 20 texture parameters were calculated. T2 mapping of the tibial cartilage was performed in groups 1 and 2. Mean parameter values were compared between groups using ANOVA. Linear discriminant analysis (LDA) was used to evaluate the ability of texture analysis to classify subjects correctly.  RESULTS: Significant differences in 18/20 and 12/20 subchondral bone texture parameters were demonstrated between groups at the MT and LT respectively. There was no significant difference in mean MT or LT cartilage T2 values between group 1 and group 2. LDA demonstrated subject classification accuracy of 97 % (95 % CI 91-100 %).  CONCLUSION: MRI texture analysis of tibial subchondral bone may allow detection of alteration in subchondral bone architecture in OA. This has potential applications in understanding OA pathogenesis and assessing response to treatment.  KEY POINTS: • Improved techniques to monitor OA disease progression and treatment response are desirable • Subchondral bone (SB) may play significant role in the development of OA • MRI texture analysis is a method of quantifying changes in SB architecture • Pilot study showed that this technique is feasible and reliable • Significant differences in SB texture were demonstrated between individuals with/without OA
Measurements of B-mode Polarization of the Cosmic Microwave Background from 500 Square Degrees of SPTpol Data
We report a B-mode power spectrum measurement from the cosmic microwave
background (CMB) polarization anisotropy observations made using the SPTpol
instrument on the South Pole Telescope. This work uses 500 deg of SPTpol
data, a five-fold increase over the last SPTpol B-mode release. As a result,
the bandpower uncertainties have been reduced by more than a factor of two, and
the measurement extends to lower multipoles: . Data from both
95 and 150 GHz are used, allowing for three cross-spectra: 95 GHz x 95 GHz, 95
GHz x 150 GHz, and 150 GHz x 150 GHz. B-mode power is detected at very high
significance; we find , corresponding to a
detection of power. An upper limit is set on the tensor-to-scalar
ratio, at 95% confidence (the expected constraint on
given the measurement uncertainties is 0.22). We find the measured B-mode power
is consistent with the Planck best-fit CDM model predictions. Scaling
the predicted lensing B-mode power in this model by a factor Alens, the data
prefer Alens = . These data are currently the most precise
measurements of B-mode power at .Comment: 16 pages, 4 figures, Submitted to PR
- …