We present a detailed report on sterile neutrino oscillation and 235Uν¯e energy spectrum measurement results from the PROSPECT experiment at the highly enriched High Flux Isotope Reactor (HFIR) at ...Oak Ridge National Laboratory. In 96 calendar days of data taken at an average baseline distance of 7.9 m from the center of the 85 MW HFIR core, the PROSPECT detector has observed more than 50,000 interactions of νe produced in beta decays of 235U fission products. New limits on the oscillation of ν¯e to light sterile neutrinos have been set by comparing the detected energy spectra of ten reactor-detector baselines between 6.7 and 9.2 meters. Measured differences in energy spectra between baselines show no statistically significant indication of ν¯e to sterile neutrino oscillation and disfavor the reactor antineutrino anomaly best-fit point at the 2.5σ confidence level. The reported 235U ν¯e energy spectrum measurement shows excellent agreement with energy spectrum models generated via conversion of the measured 235U beta spectrum, with a χ2/d.o.f. of 31/31. PROSPECT is able to disfavor at 2.4σ confidence level the hypothesis that 235U ν¯e are solely responsible for spectrum discrepancies between model and data obtained at commercial reactor cores. A data-model deviation in PROSPECT similar to that observed by commercial core experiments is preferred with respect to no observed deviation, at a 2.2σ confidence level.
Origami and kirigami have emerged as potential tools for the design of mechanical metamaterials whose properties such as curvature, Poisson ratio, and existence of metastable states can be tuned ...using purely geometric criteria. A major obstacle to exploiting this property is the scarcity of tools to identify and program the flexibility of fold patterns. We exploit a recent connection between spring networks and quantum topological states to design origami with localized folding motions at boundaries and study them both experimentally and theoretically. These folding motions exist due to an underlying topological invariant rather than a local imbalance between constraints and degrees of freedom. We give a simple example of a quasi-1D folding pattern that realizes such topological states. We also demonstrate how to generalize these topological design principles to two dimensions. A striking consequence is that a domain wall between two topologically distinct, mechanically rigid structures is deformable even when constraints locally match the degrees of freedom.
This Letter reports the first scientific results from the observation of antineutrinos emitted by fission products of ^{235}U at the High Flux Isotope Reactor. PROSPECT, the Precision Reactor ...Oscillation and Spectrum Experiment, consists of a segmented 4 ton ^{6}Li-doped liquid scintillator detector covering a baseline range of 7-9 m from the reactor and operating under less than 1 m water equivalent overburden. Data collected during 33 live days of reactor operation at a nominal power of 85 MW yield a detection of 25 461±283 (stat) inverse beta decays. Observation of reactor antineutrinos can be achieved in PROSPECT at 5σ statistical significance within 2 h of on-surface reactor-on data taking. A reactor model independent analysis of the inverse beta decay prompt energy spectrum as a function of baseline constrains significant portions of the previously allowed sterile neutrino oscillation parameter space at 95% confidence level and disfavors the best fit of the reactor antineutrino anomaly at 2.2σ confidence level.
This Letter reports the first measurement of the 235U $\bar{ν}$e energy spectrum by PROSPECT, the Precision Reactor Oscillation and Spectrum experiment, operating 7.9 m from the 85 MWth highly ...enriched uranium (HEU) High Flux Isotope Reactor. With a surface-based, segmented detector, PROSPECT has observed 31678±304(stat) $\bar{ν}$e-induced inverse beta decays, the largest sample from HEU fission to date, 99% of which are attributed to 235U. Despite broad agreement, comparison of the Huber 235U model to the measured spectrum produces a χ2/ndf=51.4/31, driven primarily by deviations in two localized energy regions. The measured 235U spectrum shape is consistent with a deviation relative to prediction equal in size to that observed at low-enriched uranium power reactors in the $\bar{ν}$e energy region of 5–7 MeV.
In May of 2011, NASA selected the
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dentification, and
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ecurity–
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plorer (OSIRIS-REx) asteroid sample return mission as the third mission ...in the New Frontiers program. The other two New Frontiers missions are
New Horizons
, which explored Pluto during a flyby in July 2015 and is on its way for a flyby of Kuiper Belt object 2014 MU69 on January 1, 2019, and
Juno
, an orbiting mission that is studying the origin, evolution, and internal structure of Jupiter. The spacecraft departed for near-Earth asteroid (101955) Bennu aboard an United Launch Alliance Atlas V 411 evolved expendable launch vehicle at 7:05 p.m. EDT on September 8, 2016, on a seven-year journey to return samples from Bennu. The spacecraft is on an outbound-cruise trajectory that will result in a rendezvous with Bennu in November 2018. The science instruments on the spacecraft will survey Bennu to measure its physical, geological, and chemical properties, and the team will use these data to select a site on the surface to collect at least 60 g of asteroid regolith. The team will also analyze the remote-sensing data to perform a detailed study of the sample site for context, assess Bennu’s resource potential, refine estimates of its impact probability with Earth, and provide ground-truth data for the extensive astronomical data set collected on this asteroid. The spacecraft will leave Bennu in 2021 and return the sample to the Utah Test and Training Range (UTTR) on September 24, 2023.
The PROSPECT physics program Ashenfelter, J; Balantekin, A B; Band, H R ...
Journal of physics. G, Nuclear and particle physics,
10/2016, Letnik:
43, Številka:
11
Journal Article
Recenzirano
Odprti dostop
The precision reactor oscillation and spectrum experiment, PROSPECT, is designed to make a precise measurement of the antineutrino spectrum from a highly-enriched uranium reactor and probe eV-scale ...sterile neutrinos by searching for neutrino oscillations over a distance of several meters. PROSPECT is conceived as a 2-phase experiment utilizing segmented 6Li-doped liquid scintillator detectors for both efficient detection of reactor antineutrinos through the inverse beta decay reaction and excellent background discrimination. PROSPECT Phase I consists of a movable 3 ton antineutrino detector at distances of 7-12 m from the reactor core. It will probe the best-fit point of the e disappearance experiments at 4 in 1 year and the favored region of the sterile neutrino parameter space at > 3 in 3 years. With a second antineutrino detector at 15-19 m from the reactor, Phase II of PROSPECT can probe the entire allowed parameter space below 10 eV2 at 5 in 3 additional years. The measurement of the reactor antineutrino spectrum and the search for short-baseline oscillations with PROSPECT will test the origin of the spectral deviations observed in recent θ 13 experiments, search for sterile neutrinos, and conclusively address the hypothesis of sterile neutrinos as an explanation of the reactor anomaly.
The syntheses and the electrochemical spectroscopic properties of a suite of asymmetrical bistridentate cyclometalated Ru(II) complexes bearing terminal triphenylamine (TPA) substituents are ...reported. These complexes, which contain structural design elements common to both inorganic and organic dyes that exhibit superior power conversion efficiencies in the dye-sensitized solar cell (DSSC), are broadly formulated as RuII(L-2,5′-thiophene-TPA-R1)(L-R2)+ L = tridentate chelating ligand (e.g., 2,2′:6′,2′′-terpyridine (tpy); deprotonated forms of 1,3-di(pyridin-2-yl)benzene (Hdpb) or 6-phenyl-2,2′-bipyridine (Hpbpy)); R1 = −H, −Me, −OMe; R2 = −H, −CO2Me, −CO2H. The following structural attributes were systematically modified for the series: (i) electron-donating character of the terminal substituents (e.g., R1 = −H, −Me, −OMe) placed para to the amine of the “L-2,5′-thiophene-TPA-R1” ligand framework; (ii) electron-withdrawing character of the tridentate chelate distal to the TPA-substituted ligand (e.g., R2 = −H, −CO2Me, −CO2H); and (iii) position of the organometallic bond about the Ru(II) center. UV–vis spectra reveal intense and broad absorption bands arising from a collection of metal-to-ligand charge-transfer (MLCT) and TPA-based intraligand charge-transfer (ILCT) transitions that, in certain cases, extend beyond 800 nm. Electrochemical data indicate that the oxidative behavior of the TPA and metal chelate units can be independently modulated except in cases where the anionic phenyl ring is in direct conjugation with the TPA unit. In most cases, the anionic character of the cyclometalating ligands renders a metal-based oxidation event prior to the oxidation of the TPA unit. This situation can, however, be reversed with an appropriately positioned Ru–C bond and electron-rich R1 group. This finding is important in that this arrangement confines the highest occupied molecular orbital (HOMO) to the TPA unit rather than the metal, which is optimal for sensitizing TiO2; indeed, a remarkably high power conversion efficiency (η) in the DSSC (i.e., 8.02%) is measured for the TPA-substituted pbpy– chelate where R1 = −OMe. These results provide a comprehensive strategy for improving the performance of bistridentate Ru sensitizers devoid of NCS– groups for the DSSC.
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