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Fu, J.

Publications and source records attributed to Fu, J..

47 records · Page 3

All sources NASA NTRS DOE OSTI

DOE OSTI2021

Measurements of the E-mode polarization and temperature-E-mode correlation of the CMB from SPT-3G 2018 data

We present measurements of the E -mode ( E E ) polarization power spectrum and temperature- E -mode ( T E ) 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 deg 2 region at 95, 150, and 220 GHz taken over a four-month period in 2018. We report binned values of the E E and T E 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 E E and 300 ≤ ℓ ≤ 1700 for T E , 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 Λ CDM cosmological model with parameter constraints consistent with those from Planck and SPTpol data. From SPT-3G data alone, we find H 0 = 68.8 ± 1.5 km s - 1 Mpc - 1 and σ 8 = 0.789 ± 0.016 , with a gravitational lensing amplitude consistent with the Λ CDM prediction ( A L = 0.98 ± 0.12 ). We combine the SPT-3G and the Planck data sets and obtain joint constraints on the Λ CDM model. The volume of the 68% confidence region in six-dimensional Λ CDM 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.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2021

Measurement of the very rare K+ → $ {\pi}^{+}\nu \overline{\nu} $ decay

The NA62 experiment reports the branching ratio measurement BR K + → π + ν ν ¯ = 10.6 - 3.4 + 4.0 stat ± 0.9 syst × 10 - 11 at 68% CL, based on the observation of 20 signal candidates with an expected background of 7.0 events from the total data sample collected at the CERN SPS during 2016–2018. This provides evidence for the very rare K + → π + ν ν ¯ decay, observed with a significance of 3.4 σ . The experiment achieves a single event sensitivity of (0 . 839 ± 0 . 054) × 10 - 11 , corresponding to 10.0 events assuming the Standard Model branching ratio of (8 . 4 ± 1 . 0) × 10 - 11 . This measurement is also used to set limits on BR( K + → π + X ), where X is a scalar or pseudo-scalar particle. Details are given of the analysis of the 2018 data sample, which corresponds to about 80% of the total data sample.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2021

Search for K + decays to a muon and invisible particles

The NA62 experiment at CERN reports searches for K + → μ + N and K + → μ + ν X decays, where N and X are massive invisible particles, using the 2016–2018 data set. The N particle is assumed to be a heavy neutral lepton, and the results are expressed as upper limits of O ( 10 - 8 ) of the neutrino mixing parameter | U μ 4 | 2 for N masses in the range 200–384 MeV/ c 2 and lifetime exceeding 50 ns. The X particle is considered a scalar or vector hidden sector mediator decaying to an invisible final state, and upper limits of the decay branching fraction for X masses in the range 10–370 MeV/ c 2 are reported for the first time, ranging from O ( 10 - 5 ) to O ( 10 - 7 ) . An improved upper limit of 1.0 × 10 - 6 is established at 90% CL on the K + → μ + ν ν ν ¯ branching fraction.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2021

Search for a feebly interacting particle X in the decay K + → π + X

A search for the K + → π + X decay, where X is a long-lived feebly interacting particle, is performed through an interpretation of the K + → π + $\overline{vv}$ analysis of data collected in 2017 by the NA62 experiment at CERN. Two ranges of X masses, 0–110 MeV/c 2 and 154–260 MeV/c 2 , and lifetimes above 100 ps are considered. The limits set on the branching ratio, BR(K + → π + X), are competitive with previously reported searches in the first mass range, and improve on current limits in the second mass range by more than an order of magnitude.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2021

Search for π 0 decays to invisible particles

The NA62 experiment at the CERN SPS reports a study of a sample of 4 × 10 9 tagged π0 mesons from K + → π + π 0 (γ), searching for the decay of the π 0 to invisible particles. No signal is observed in excess of the expected background fluctuations. An upper limit of 4.4 × 10 –9 is set on the branching ratio at 90% confidence level, improving on previous results by a factor of 60. This result can also be interpreted as a model- independent upper limit on the branching ratio for the decay K + → π + X, where X is a particle escaping detection with mass in the range 0.110–0.155 GeV/c 2 and rest lifetime greater than 100 ps. Model-dependent upper limits are obtained assuming X to be an axion-like particle with dominant fermion couplings or a dark scalar mixing with the Standard Model Higgs boson.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2020

An investigation of the very rare ${K}^{+}\to {\pi}^{+}\nu \overline{\nu}$ decay

The NA62 experiment reports an investigation of the ${K}^{+}\to {\pi}^{+}\nu \overline{\nu}$ mode from a sample of ${K}^{+}$ decays collected in 2017 at the CERN SPS. The experiment has achieved a single event sensitivity of (0.389 ± 0.024) × 10 -10 , corresponding to 2.2 events assuming the Standard Model branching ratio of (8.4 ± 1.0) × 10 -11 . Two signal candidates are observed with an expected background of 1.5 events. Combined with the result of a similar analysis conducted by NA62 on a smaller data set recorded in 2016, the collaboration now reports an upper limit of 1.78 × 10 -10 for the ${K}^{+}\to {\pi}^{+}\nu \overline{\nu}$ branching ratio at 90% CL. This, together with the corresponding 68% CL measurement of (${0.48}_{-0.48}^{+0.72}$) × 10 -10 , are currently the most precise results worldwide, and are able to constrain some New Physics models that predict large enhancements still allowed by previous measurements.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2020

Broadband, millimeter-wave antireflection coatings for large-format, cryogenic aluminum oxide optics

Here, we present two prescriptions for broadband (~77 -252 GHz), millimeter-wave antireflection coatings for cryogenic, sintered polycrystalline aluminum oxide optics: one for large-format (700 mm diameter) planar and plano–convex elements, the other for densely packed arrays of quasi-optical elements—in our case, 5 mm diameter half-spheres (called “lenslets”). The coatings comprise three layers of commercially available, polytetrafluoroethylene-based, dielectric sheet material. The lenslet coating is molded to fit the 150 mm diameter arrays directly, while the large-diameter lenses are coated using a tiled approach. We review the fabrication processes for both prescriptions, then discuss laboratory measurements of their transmittance and reflectance. In addition, we present the inferred refractive indices and loss tangents for the coating materials and the aluminum oxide substrate. We find that at 150 GHz and 300 K the large-format coating sample achieves (97±2)% transmittance, and the lenslet coating sample achieves (94±3)% transmittance.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Particle Response of Antenna-Coupled TES Arrays: Results from SPIDER and the Laboratory

Future mm-wave and sub-mm space missions will employ large arrays of multiplexed transition-edge-sensor (TES) bolometers. Such instruments must contend with the high flux of cosmic rays beyond our atmosphere that induce ‘glitches’ in bolometer data, which posed a challenge to data analysis from the Planck bolometers. Future instruments will face the additional challenges of shared substrate wafers and multiplexed readout wiring. Here, we explore the susceptibility of modern TES arrays to the cosmic ray environment of space using two data sets: the 2015 long-duration balloon flight of the SPIDER cosmic microwave background polarimeter, and a laboratory exposure of SPIDER flight hardware to radioactive sources. We find manageable glitch rates and short glitch durations, leading to minimal effect on SPIDER analysis. We constrain energy propagation within the substrate through a study of multi-detector coincidences and give a preliminary look at pulse shapes in laboratory data.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2019

On-Sky Performance of the SPT-3G Frequency-Domain Multiplexed Readout

Frequency-domain multiplexing (fMux) is an established technique for the readout of large arrays of transition-edge sensor (TES) bolometers. Each TES in a multiplexing module has a unique AC voltage bias that is selected by a resonant filter. This scheme provides for the operation and readout of multiple bolometers on a single pair of wires, reducing thermal loading onto sub-Kelvin stages. The current receiver on the South Pole Telescope, SPT-3G, uses a 68x fMux system to operate its large-format camera of ~16,000 TES bolometers. We present here the successful implementation and performance of the SPT-3G readout as measured on-sky. Characterization of the noise reveals a median pair-differenced 1/f knee frequency of 33 mHz, indicating that low-frequency noise in the readout will not limit SPT-3G’s measurements of sky power on large angular scales. Measurements further show that the median readout white noise level in each of the SPT-3G observing bands is below the expectation for photon noise, demonstrating that SPT-3G is operating in the photon-noise-dominated regime.

47 OTHER INSTRUMENTATION↗

NASA NTRS2006

Calculation of Atomic Data for NASA Missions

The interpretation of cosmic spectra relies on a vast sea of atomic data which are not readily obtainable from analytic expressions or simple calculations. Rather, their evaluation typically requires state-of-the-art atomic physics calculations, with the inclusion of weaker effects (spin-orbit and configuration interactions, relaxation, Auger broadening, etc.), to achieve the level of accuracy needed for use by astrophysicists. Our NASA-supported research program is focused on calculating data for three important atomic processes, 1) dielectronic recombination (DR), 2) inner-shell photoabsorption, and 3) fluorescence and Auger decay of inner-shell vacancy states. Some additional details and examples of our recent findings are given.

Gorczyca, T. W.↗

NASA NTRS2002

Basis for the thermal-vacuum hot dwell test duration

This work suggests that the hot dwell duration for each test should be determined in two steps: a minimum hot duration of 80 hours be required and then followed by specific tailoring be conducted to arrive at the proper test duration.

early test failure distribution Weibull analysis r↗