113 research outputs found
Emission Characteristics of an Axially Staged Sector Combustor for a Small Core High OPR Subsonic Aircraft Engine
This paper presents the nitrogen oxides, carbon monoxide, and particulate matter emissions of a single sector axially staged combustor sector designed and fabricated by United Technologies Research Center (UTRC) in partnership with NASA under a compact low-emissions combustor contract supported by the NASA Advanced Air Transport Technology (AATT) N+3 project. The test was conducted at NASA Glenn Research Center's CE-5 combustion test facility. The facility provided inlet air temperatures up to 922 K and pressures up to 19.0 bar. The combustor design concept, called Axially Controlled Stoichiometry (ACS), was developed by Pratt & Whitney (P&W) under NASA's Environmentally Responsible Aviation (ERA) program for an N+2 combustor for use in twin-aisle subsonic aircraft engines. Under the N+3 project the ACS combustor was scaled-down for application to small-core N+3 engines for use in single-aisle aircraft. The results show that the NOx and CO emissions characteristics are similar in both the N+2 and N+3 applications. The non-volatile particulate matter (nvPM) emissions trends are similar to CO emissions with an exception at high fuel-air ratio, as inlet air temperature and pressure conditions change from taxi to approach. Three NOx correlation equations are generated to describe theNOx emissions of this combustor. The percentage landing and takeoff (LTO) NOx reduction of the N+3 ACS combustor is between 82% and 89% relative to the ICAO CAEP/6 standard, which meets the NASA N+3 goal of exceeding 80% LTO NOx reduction
Report of the Topical Group on Cosmic Frontier 5 Dark Energy and Cosmic Acceleration: Cosmic Dawn and Before for Snowmass 2021
This report summarizes the envisioned research activities as gathered from
the Snowmass 2021 CF5 working group concerning Dark Energy and Cosmic
Acceleration: Cosmic Dawn and Before. The scientific goals are to study
inflation and to search for new physics through precision measurements of relic
radiation from the early universe. The envisioned research activities for this
decade (2025-35) are constructing and operating major facilities and developing
critical enabling capabilities. The major facilities for this decade are the
CMB-S4 project, a new Stage-V spectroscopic survey facility, and existing
gravitational wave observatories. Enabling capabilities include aligning and
investing in theory, computation and model building, and investing in new
technologies needed for early universe studies in the following decade (2035+).Comment: contribution to Snowmass 202
Characterization of MKIDs for CMB observation at 220 GHz with the South Pole Telescope
We present an updated design of the 220 GHz microwave kinetic inductance
detector (MKID) pixel for SPT-3G+, the next-generation camera for the South
Pole Telescope. We show results of the dark testing of a 63-pixel array with
mean inductor quality factor , aluminum inductor
transition temperature K, and kinetic inductance fraction
. We optically characterize both the microstrip-coupled and
CPW-coupled resonators, and find both have a spectral response close to
prediction with an optical efficiency of . However, we find
slightly lower optical response on the lower edge of the band than predicted,
with neighboring dark detectors showing more response in this region, though at
level consistent with less than 5\% frequency shift relative to the optical
detectors. The detectors show polarized response consistent with expectations,
with a cross-polar response of for both detector orientations.Comment: 6 pages, 5 figures, ASC 2022 proceeding
Electromagnetic properties of aluminum-based bilayers for kinetic inductance detectors
The complex conductivity of a superconducting thin film is related to the quasiparticle density, which depends on the physical temperature and can also be modified by external pair breaking with photons and phonons. This relationship forms the underlying operating principle of Kinetic Inductance Detectors (KIDs), where the detection threshold is governed by the superconducting energy gap. We investigate the electromagnetic properties of thin-film aluminum that is proximitized with either a normal metal layer of copper or a superconducting layer with a lower TC , such as iridium, in order to extend the operating range of KIDs. Using the Usadel equations along with the Nam expressions for complex conductivity, we calculate the density of states and the complex conductivity of the resulting bilayers to understand the dependence of the pair breaking threshold, surface impedance, and intrinsic quality factor of superconducting bilayers on the relative film thicknesses. The calculations and analyses provide theoretical insights in designing aluminum-based bilayer kinetic inductance detectors for detection of microwave photons and athermal phonons at the frequencies well below the pair breaking threshold of a pure aluminum film
CMB-S4 Science Book, First Edition
This book lays out the scientific goals to be addressed by the
next-generation ground-based cosmic microwave background experiment, CMB-S4,
envisioned to consist of dedicated telescopes at the South Pole, the high
Chilean Atacama plateau and possibly a northern hemisphere site, all equipped
with new superconducting cameras. CMB-S4 will dramatically advance cosmological
studies by crossing critical thresholds in the search for the B-mode
polarization signature of primordial gravitational waves, in the determination
of the number and masses of the neutrinos, in the search for evidence of new
light relics, in constraining the nature of dark energy, and in testing general
relativity on large scales
First Results from a Broadband Search for Dark Photon Dark Matter in the to eV range with a coaxial dish antenna
We present first results from a dark photon dark matter search in the mass
range from 44 to 52 () using a
room-temperature dish antenna setup called GigaBREAD. Dark photon dark matter
converts to ordinary photons on a cylindrical metallic emission surface with
area and is focused by a novel parabolic reflector onto a horn
antenna. Signals are read out with a low-noise receiver system. A first data
taking run with 24 days of data does not show evidence for dark photon dark
matter in this mass range, excluding dark photon - photon mixing parameters
in this range at 90% confidence level. This surpasses
existing constraints by about two orders of magnitude and is the most stringent
bound on dark photons in this range below 49 eV.Comment: 7 pages, 4 figure
A Stress Induced Source of Phonon Bursts and Quasiparticle Poisoning
The performance of superconducting qubits is degraded by a poorly
characterized set of energy sources breaking the Cooper pairs responsible for
superconductivity, creating a condition often called "quasiparticle poisoning."
Recently, a superconductor with one of the lowest average quasiparticle
densities ever measured exhibited quasiparticles primarily produced in bursts
which decreased in rate with time after cooldown. Similarly, several cryogenic
calorimeters used to search for dark matter have also observed an unknown
source of low-energy phonon bursts that decrease in rate with time after
cooldown. Here, we show that a silicon crystal glued to its holder exhibits a
rate of low-energy phonon events that is more than two orders of magnitude
larger than in a functionally identical crystal suspended from its holder in a
low-stress state. The excess phonon event rate in the glued crystal decreases
with time since cooldown, consistent with a source of phonon bursts which
contributes to quasiparticle poisoning in quantum circuits and the low-energy
events observed in cryogenic calorimeters. We argue that relaxation of
thermally induced stress between the glue and crystal is the source of these
events, and conclude that stress relaxation contributes to quasiparticle
poisoning in superconducting qubits and the athermal phonon background in a
broad class of rare-event searches.Comment: 13 pages, 6 figures. W. A. Page and R. K. Romani contributed equally
to this work. Correspondence should be addressed to R. K. Roman
Snowmass2021 Cosmic Frontier: Cosmic Microwave Background Measurements White Paper
This is a solicited whitepaper for the Snowmass 2021 community planning exercise. The paper focuses on measurements and science with the Cosmic Microwave Background (CMB). The CMB is foundational to our understanding of modern physics and continues to be a powerful tool driving our understanding of cosmology and particle physics. In this paper, we outline the broad and unique impact of CMB science for the High Energy Cosmic Frontier in the upcoming decade. We also describe the progression of ground-based CMB experiments, which shows that the community is prepared to develop the key capabilities and facilities needed to achieve these transformative CMB measurements
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