First narrow-band search for continuous gravitational waves from known pulsars in advanced detector data

Spinning neutron stars asymmetric with respect to their rotation axis are potential sources of continuous gravitational waves for ground-based interferometric detectors. In the case of known pulsars a fully coherent search, based on matched filtering, which uses the position and rotational parameters obtained from electromagnetic observations, can be carried out. Matched filtering maximizes the signalto- noise (SNR) ratio, but a large sensitivity loss is expected in case of even a very small mismatch between the assumed and the true signal parameters. For this reason, narrow-band analysis methods have been developed, allowing a fully coherent search for gravitational waves from known pulsars over a fraction of a hertz and several spin-down values. In this paper we describe a narrow-band search of 11 pulsars using data from Advanced LIGO’s first observing run. Although we have found several initial outliers, further studies show no significant evidence for the presence of a gravitational wave signal. Finally, we have placed upper limits on the signal strain amplitude lower than the spin-down limit for 5 of the 11 targets over the bands searched; in the case of J1813-1749 the spin-down limit has been beaten for the first time. For an additional 3 targets, the median upper limit across the search bands is below the spin-down limit. This is the most sensitive narrow-band search for continuous gravitational waves carried out so far

Fusion Energy Output Greater than the Kinetic Energy of an Imploding Shell at the National Ignition Facility

A series of cryogenic, layered deuterium-tritium (DT) implosions have produced, for the first time, fusion energy output twice the peak kinetic energy of the imploding shell. These experiments at the National Ignition Facility utilized high density carbon ablators with a three-shock laser pulse (1.5 MJ in 7.5 ns) to irradiate low gas-filled (0.3  mg/cc of helium) bare depleted uranium hohlraums, resulting in a peak hohlraum radiative temperature ∼290  eV. The imploding shell, composed of the nonablated high density carbon and the DT cryogenic layer, is, thus, driven to velocity on the order of 380  km/s resulting in a peak kinetic energy of ∼21  kJ, which once stagnated produced a total DT neutron yield of 1.9×10¹⁶ (shot N170827) corresponding to an output fusion energy of 54 kJ. Time dependent low mode asymmetries that limited further progress of implosions have now been controlled, leading to an increased compression of the hot spot. It resulted in hot spot areal density (ρr∼0.3  g/cm²) and stagnation pressure (∼360  Gbar) never before achieved in a laboratory experiment

Improved Performance of High Areal Density Indirect Drive Implosions at the National Ignition Facility using a Four-Shock Adiabat Shaped Drive

Hydrodynamic instabilities can cause capsule defects and other perturbations to grow and degrade implosion performance in ignition experiments at the National Ignition Facility (NIF). Here, we show the first experimental demonstration that a strong unsupported first shock in indirect drive implosions at the NIF reduces ablation front instability growth leading to a 3 to 10 times higher yield with fuel ρR > 1  g/cm[superscript 2]. This work shows the importance of ablation front instability growth during the National Ignition Campaign and may provide a path to improved performance at the high compression necessary for ignition

First High-Convergence Cryogenic Implosion in a Near-Vacuum Hohlraum

Recent experiments on the National Ignition Facility [M. J. Edwards et al., Phys. Plasmas 20, 070501 (2013)] demonstrate that utilizing a near-vacuum hohlraum (low pressure gas-filled) is a viable option for high convergence cryogenic deuterium-tritium (DT) layered capsule implosions. This is made possible by using a dense ablator (high-density carbon), which shortens the drive duration needed to achieve high convergence: a measured 40% higher hohlraum efficiency than typical gas-filled hohlraums, which requires less laser energy going into the hohlraum, and an observed better symmetry control than anticipated by standard hydrodynamics simulations. The first series of near-vacuum hohlraum experiments culminated in a 6.8 ns, 1.2 MJ laser pulse driving a 2-shock, high adiabat (α ~ 3.5) cryogenic DT layered high density carbon capsule. This resulted in one of the best performances so far on the NIF relative to laser energy, with a measured primary neutron yield of 1.8×10[superscript 15] neutrons, with 20% calculated alpha heating at convergence ~27×

A Fermi Gamma-Ray Burst Monitor Search for Electromagnetic Signals Coincident with Gravitational-wave Candidates in Advanced LIGO's First Observing Run

We present a search for prompt gamma-ray counterparts to compact binary coalescence gravitational wave (GW) candidates from Advanced LIGO's first observing run (O1). As demonstrated by the multimessenger observations of GW170817/GRB 170817A, electromagnetic and GW observations provide complementary information about the astrophysical source, and in the case of weaker candidates, may strengthen the case for an astrophysical origin. Here we investigate low-significance GW candidates from the O1 compact binary coalescence searches using the Fermi Gamma-Ray Burst Monitor (GBM), leveraging its all sky and broad energy coverage. Candidates are ranked and compared to background to measure the significance. Those with false alarm rates (FARs) of less than 10−5 Hz (about one per day, yielding a total of 81 candidates) are used as the search sample for gamma-ray follow-up. No GW candidates were found to be coincident with gamma-ray transients independently identified by blind searches of the GBM data. In addition, GW candidate event times were followed up by a separate targeted search of GBM data. Among the resulting GBM events, the two with the lowest FARs were the gamma-ray transient GW150914-GBM presented in Connaughton et al. and a solar flare in chance coincidence with a GW candidate

СТРУКТУРА, ФАЗОВЫЙ СОСТАВ И МЕХАНИЧЕСКИЕ СВОЙСТВА КРИСТАЛЛОВ ZrO2, ЧАСТИЧНО СТАБИЛИЗИРОВАННЫХ Y2O3

The structure of PSZ crystals has been studied as a function of the content of the stabilizing impurity (Y2O3) by X–ray diffraction, transmission electron microscopy (TEM) and atomic−force microscope (AFM). The hardness and fracture toughness have been measured by microindentation. The study has shown that PSZ crystals obtained by directional solidification of the melt consist of two tetragonal phases (t and t’) with varying degrees of tetragonality. Increasing the stabilizing impurity concentration leads to an increase in the volume fraction of the “untransformable” t’ phase. Experiments have shown that an increase in the concentration of the stabilizing impurity leads to a growth in the amount of positively charged oxygen vacancies (the F++–centers) which increase the lattice parameter and stabilize the structure. The character of the twinned structure changes depending on the concentration of the stabilizing impurity. In PSZ crystals with Y2O3 concentration from 2.8 to 3.2 mol. % twins first, second and third orders as well as large twins consist of smaller twin domains are observed. At high concentrations of stabilizing impurities (3.7—4.0 mol. %) the twin structure becomes smaller and more uniform. This suggests that twinning occurs simultaneously and is localized within small volumes. The character of the twinned structure changes depending on the concentration of the stabilizing impurity. This work shows that the quantity of hardening (fracture toughness) is proportional to the content of the transformable t phase.Методами рентгеновской дифрактометрии, атомно-силовой и просвечивающей электронной микроскопии исследована структура кристаллов частично стабилизированного ZrO2 (ЧСЦ) в зависимости от содержания стабилизирующей примеси (Y2O3). Проведены измерения твердости и трещиностойкости методом микроиндентирования. Установлено, что кристаллы ЧСЦ, полученные направленной кристаллизацией расплава, характеризуются наличием двух тетрагональных фаз (t и t’), различающихся степенью тетрагональности. Причем увеличение концентрации Y2O3 в кристаллах приводит к увеличению содержания нетрансформируемой t'-фазы. Экспериментально показано, что рост концентрации стабилизирующей примеси приводит к увеличению количества кислородных положительно заряженных вакансий, (F++-центров), которые увеличивают параметр решетки и стабилизируют структуру. Обнаружено, что повышение концентрации Y2O3 влияет на вид и дисперсность двойниковых доменов. В кристаллах ЧСЦ с концентрацией Y2O3 от 2,8 до 3,2 % (мол.) выявлены двойники первого, второго, третьего порядков, в свою очередь, каждый из двойников содержит внутри двойники следующего порядка. При больших концентрациях стабилизирующей примеси (3,7—4,0 % (мол.)) двойниковая структура становится более мелкой и однородной, двойникование идет одновременно и локализуется в малых объемах. Показано, что величина упрочнения (трещиностойкость) пропорциональна содержанию трансформируемой t-фазы

Теплопроводность монокристаллов твердых растворов на основе диоксида циркония, стабилизированных оксидами скандия, иттрия, гадолиния и иттербия

The phase composition and heat conductivity of (ZrO2)0.9(R2O3)0.1 solid solution single crystals have been studied, where R = (Gd, Yb, Sc, Y), (ZrO2)0.9(Sc2O3)0.09(Gd2O3)0.01 and (ZrO2)0.9(Sc2O3)0.09(Yb2O3)0.01. Single crystals have been grown by directional melt crystallization in a cold skull. The phase composition of the crystals has been studied using X-ray diffraction and Raman spectroscopy. The heat conductivity of the crystals has been studied using the absolute steady-state technique of longitudinal heat flow in the 50—300 K range. We show that at a total stabilizing oxide concentration of 10 mol.% the phase composition of the crystals depends on the ionic radius of the stabilizing cation. The (ZrO2)0.9(Sc2O3)0.1 crystals have the lowest heat conductivity in the 50—300 K range while the (ZrO2)0.9(Gd2O3)0.1 solid solutions have the lowest heat conductivity at 300 K.Analysis of the experimental data suggests that the heat conductivity of the crystals depends mainly on the phase composition and ionic radius of the stabilizing cation. Phonon scattering caused by the difference in the weight of the co-doping oxide cation has a smaller effect on the heat conductivity.В работе приведены результаты исследования фазового состава и теплопроводности кристаллов твердых растворов (ZrO2)0,9(R2O3)0,1 где R = (Gd, Yb, Sc, Y), (ZrO2)0,9(Sc2O3)0,09(Gd2O3)0,01 и (ZrO2)0,9(Sc2O3)0,09(Yb2O3)0,01. Кристаллы выращивали методом направленной кристаллизации расплава в холодном контейнере. Исследования фазового состава кристаллов проводили методом рентгеновской дифрактометрии и комбинационного рассеяния света. Теплопроводность кристаллов изучали абсолютным стационарным методом продольного теплового потока в интервале температур 50—300 К.Показано, что при суммарной концентрации стабилизирующих оксидов 10 % (мол.) фазовый состав кристаллов зависит от величины ионного радиуса стабилизирующего катиона. Минимальные значения теплопроводности в диапазоне температур 50—150 K имеют кристаллы (ZrO2)0,9(Sc2O3)0,1, а при температуре 300 К — твердые растворы (ZrO2)0,9(Gd2O3)0,1.Анализ полученных данных позволяет сделать вывод о том, что основное влияние на теплопроводность оказывает фазовый состав и величина ионного радиуса стабилизирующего катиона. При этом фононное рассеяние, связанное с различиями массы катионов солегирующего оксида, оказывает на теплопроводность меньшее значение

Анизотропия механических свойств и механизмы упрочнения в кристаллах твердых растворов ZrO2—Y2O3

Abstract. The anisotropy of the mechanical properties of single crystal ZrO2 — 2.8 mol.% Y2O3 solid solutions has been studied. The crystals have been grown by skull melting technique. The microhardness and fracture toughness have been tested for different crystallographic planes by indentation with different indenter diagonal orientations. The study shows that the microhardness of the material depends on the crystallographic orientation but slightly whereas the fracture toughness varies for different planes. The maximum fracture toughness has been observed in the crystal specimen cut laterally to the <100> orientation. We have studied the anisotropy of the microhardness in the material for different indenter diagonal orientations. The maximum fracture toughness has been obtained for the {100} plane and the <100> indenter diagonal orientation. The phase composition inside and outside the indents on the {100}, {110} and {111} surfaces for 20, 3 and 1 N loads has been studied in local areas using Raman spectroscopy. The degree of the tetragonal−monoclinic transition has been evaluated for different crystallographic planes and different indenter diagonal orientations. The tetragonal−monoclinic transition proves to be anisotropic, and this affects the transformation hardening mechanism. The maximum amount of the monoclinic phase is present in the vicinity of the indent in the {100} plane for the <100> indenter diagonal orientation. The highest fraction toughness has also been observed in the {100} plane for the <100> indenter diagonal orientation. Probably, the abovementioned indenter diagonal orientation provides for the maximum stress concentration along the coherent conjugation planes between the tetragonal and the monoclinic phases during the tetragonal−monoclinic transition, i.e. (100)t||(100)m and [001]t||[010]m.Исследована анизотропия механических характеристик кристаллов твердых растворов ZrO2 — 2,8 % (мол.) Y2O3. Кристаллы выращены методом направленной кристаллизации расплава с использованием прямого высокочастотного нагрева. Методом индентирования проведены измерения микротвердости и трещиностойкости на разных кристаллографических гранях и при разной ориентации диагоналей индентора. Установлено, что микротвердость слабо зависит от кристаллографической ориентации, в то время как значения трещиностойкости для разных плоскостей отличаются. Максимальные значения трещиностойкости отмечены на образце, вырезанном из кристалла перпендикулярно к направлению <100>. Исследована анизотропия микротвердости в зависимости от ориентации диагоналей индентора. Максимальное значение трещиностойкости получено на плоскости {100} при ориентации диагоналей индентора в направлении <100>. Методом локальной спектроскопии комбинационного рассеяния света исследован фазовый состав внутри и вокруг отпечатков индентора на плоскостях {100}, {110} и {111} при нагрузках 20, 3 и 1 Н. Выполнена оценка степени интенсивности тетрагонально− моноклинного перехода на разных кристаллографических плоскостях и при разной ориентации диагоналей индентора. Показано, что наблюдается анизотропия тетрагонально−моноклинного перехода, влияющего на трансформационный механизм упрочнения. Максимальное количество моноклинной фазы обнаружено в области отпечатка индентора на плоскости {100}, при ориентации диагоналей индентора в направлении <100>. Также максимальное значение трещиностойкости реализуется на плоскости {100} при такой же ориентации диагоналей индентора. Возможно, что при данной ориентации диагоналей индентора максимальные действующие напряжения получаются вдоль когерентных плоскостей сопряжения тетрагональной и моноклинной фазы: при тетрагонально−моноклинном переходе — (100)t || (100)m и [001]t || [010]m

First measurement of the Hubble Constant from a Dark Standard Siren using the Dark Energy Survey Galaxies and the LIGO/Virgo Binary–Black-hole Merger GW170814

International audienceWe present a multi-messenger measurement of the Hubble constant H 0 using the binary–black-hole merger GW170814 as a standard siren, combined with a photometric redshift catalog from the Dark Energy Survey (DES). The luminosity distance is obtained from the gravitational wave signal detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO)/Virgo Collaboration (LVC) on 2017 August 14, and the redshift information is provided by the DES Year 3 data. Black hole mergers such as GW170814 are expected to lack bright electromagnetic emission to uniquely identify their host galaxies and build an object-by-object Hubble diagram. However, they are suitable for a statistical measurement, provided that a galaxy catalog of adequate depth and redshift completion is available. Here we present the first Hubble parameter measurement using a black hole merger. Our analysis results in , which is consistent with both SN Ia and cosmic microwave background measurements of the Hubble constant. The quoted 68% credible region comprises 60% of the uniform prior range [20, 140] km s−1 Mpc−1, and it depends on the assumed prior range. If we take a broader prior of [10, 220] km s−1 Mpc−1, we find (57% of the prior range). Although a weak constraint on the Hubble constant from a single event is expected using the dark siren method, a multifold increase in the LVC event rate is anticipated in the coming years and combinations of many sirens will lead to improved constraints on H 0