Wide Solid Angle Research Articles

Dynamical properties of mildly relativistic ejecta produced by the mass-loading of gamma-ray burst jets in dense ambient media

Abstract We present the results of a series of 3D special relativistic hydrodynamic simulations of a gamma-ray burst (GRB) jet in a massive circumstellar medium (CSM) surrounding the progenitor star. Our simulations reproduce the jet morphology transitioning from a well-collimated state to a thermal pressure-driven state for a range of CSM masses and outer radii. The jet–CSM interaction redistributes the jet energy to materials expanding into a wide solid angle and results in a quasi-spherical ejecta with four-velocities from $\Gamma \beta \simeq 0.1$ to 10. The mass and kinetic energy of the ejecta with velocities faster than $0.1c$ are typically of the order of $0.1\, M_{\odot }$ and $10^{51}\:\mbox{erg}$ with only a weak dependence on the CSM mass and radius for the explored CSM parameter ranges. We find that the numerically obtained density structure of the mildly relativistic ejecta is remarkably universal. The radial density profile is well approximated as a power-law function of the radial velocity with an index of $-5$, $\rho \propto v^{-5}$, in agreement with our previous simulations and other studies, as well as those suggested from recent studies on early-phase spectra of supernovae associated with GRBs. Such fast ejecta rapidly becomes transparent following its expansion. Gradually releasing the trapped thermal photons, the ejecta gives rise to bright UV–optical emission within ${\sim} 1\:$d. We discuss the potential link of the relativistic ejecta resulting from jet–CSM interaction to GRB-associated supernovae as well as fast and blue optical transients.

Study of structural parameters and systemic proper motion of Sextans dwarf spheroidal galaxy with Subaru Hyper Suprime-Cam data

ABSTRACT We use the Subaru Hyper Suprime-Cam (HSC) data to study structural parameters and systemic proper motion of the Sextans dwarf spheroidal galaxy at the heliocentric distance of 86 kpc, which is one of the most important targets for studies of dark matter nature and galaxy formation physics. Thanks to the superb image quality and wide area coverage, the HSC data enable a secure selection of member star candidates based on the colour–magnitude cut, yielding about 10 000 member candidates at magnitudes down to i ∼ 24. We use a likelihood analysis of the two-dimensional distribution of stars to estimate the structural parameters of Sextans taking into account the contamination of foreground halo stars in the Milky Way, and find that the member star distribution is well fitted by an elliptical King profile with ellipticity ϵ ≃ 0.25 and the core and tidal radii of Rc = (368.4 ± 8.5) pc and Rt = (2.54 ± 0.046) kpc, respectively. Then using the two HSC data sets of 2.66 yr time baseline on average, we find the systemic proper motions of Sextans to be (μα, μδ) = (−0.448 ± 0.075, 0.058 ± 0.078) mas yr−1, which are consistent with some of the previous works using the Gaia data of relatively bright member stars in Sextans. Thus, our results give a demonstration that ground-based, large-aperture telescope data that cover a wide solid angle of the sky and have a long time baseline, such as the upcoming data from Legacy Survey of Space and Time (LSST), can be used to study systemic proper motions of dwarf galaxies.

Designing TOGAXSI: Telescope for inverse-kinematics cluster-knockout reactions

We have launched a new research project named “ONOKORO” to elucidate the formation mechanism of clusters in atomic nuclei. The project comprehensively investigates clustering phenomena in the medium-to-heavy mass region with inverse-kinematics cluster-knockout reactions at the intermediate energy facilities. The new detector array named “TOGAXSI” is under construction for this purpose. It measures scattering angles and the energies of deuterons, tritons, 3He, and α particles emitted at forward angles from the cluster-knockout reactions. It also measures the recoil protons emitted from the scattering events at large angles. High-angular and high-energy resolutions with wide solid angles are required to achieve a good cluster separation energy resolution and a reasonably high yield. The designed telescope consists of silicon trackers and GAGG:Ce calorimeters. This paper shows the required conditions and design concepts of TOGAXSI.

High‐Throughput Data‐Driven Prediction of Stable High‐Performance Na‐Ion Sulfide Solid Electrolytes

AbstractDesigning solid electrolytes (SEs) for solid‐state batteries is a challenging issue. Herein, by using data‐driven techniques and a multi‐stage density functional theory molecular dynamics (DFT‐MD) sampling workflow that is developed, 523 443 978 cell structure samples of in‐silico Na‐based sulfides with isolated tetrahedral framework units are generated and a largely unexplored chemical space of the filtered 170 samples is examined to find novel SE candidates. Given the DFT‐accurate MD ion trajectory configurations for the largest cell structure dataset so far, the three (meta)stable solid‐solution series with high Na‐ion conductivity σNa,300K = 10−3–10−2 S cm−1: Na5−2xAl1 −xVxS4, Na5−2xAl1−xTaxS4, and Na5−2xIn1−xSbxS4 (0.375 ≤ x ≤ 0.625) are suggested. Moreover, robust descriptors for Na‐ion self‐diffusion coefficient DNa,300K accumulated from the sampling workflow by exhaustive multiple regression modeling is revealed, indicating that crystal structures with wide NaS3 solid angles and high‐valence dopants with small ionic radii result in high Na‐ion diffusivity.

Wideband dual‐polarized wide solid angle scanning cylindrically conformal millimeter‐wave phased array

A dual-polarized substrate-integrated hollow antenna (SIHA) and its cylindrically conformal phased array are proposed. The bandwidth of the proposed SIHA is 35%. The cylindrically conformal phased array with 24 SIHA subarrays can scan its beam in the whole horizontal plane and scan its beam within ± 60° in the vertical plane. The proposed array with wide band, wide-angle scanning, and dual-polarization characteristics is appropriate for millimeter-wave base station applications.

J-PARCにおける高性能<sup>3</sup>He中性子スピンフィルタの開発とその先導研究

3He spin filter is a useful neutron polarization device as a neutron polarizer and an analyzer in neutron scattering experiments because of its capabilities to polarize neutrons in broad energy range and cover wide solid angle. We are developing a 3He spin filter, based on the Spin Exchange Optical Pumping (SEOP) for polarized neutron scattering experiments at Materials and Life Science Experimental Facility (MLF) of J-PARC. A 3He gas-filling station was constructed at J-PARC, and several 3He cells with long spin relaxation times have been fabricated. A compact pumping systems with laser powers of 110 W was developed, and a 3He polarization of 85 % was achieved under real experimental conditions. Several user experiments utilizing the 3He spin filter are now being conducted at several beamlines at MLF. The development and utilization of 3He spin filters at MLF of J-PARC are reported.

Empirical Assessment of Aperiodic and Periodic Radio Bursts from Young Precessing Magnetars

We analyze the slow periodicities identified in burst sequences from FRB 121102 and FRB 180916 with periods of about 16 and 160 days, respectively, while also addressing the absence of any fast periodicity that might be associated with the spin of an underlying compact object. Both phenomena can be accounted for by a young, highly magnetized, precessing neutron star that emits beamed radiation with significant imposed phase jitter. Sporadic narrow-beam emission into an overall wide solid angle can account for the necessary phase jitter, but the slow periodicities with 25%–55% duty cycles constrain beam traversals to be significantly smaller. Instead, phase jitter may result from variable emission altitudes that yield large retardation and aberration delays. A detailed arrival time analysis for triaxial precession includes wobble of the radio beam and the likely larger, cyclical torque resulting from the changes in the spin–magnetic moment angle. These effects will confound identification of the fast periodicity in sparse data sets longer than about a quarter of a precession cycle unless fitted for and removed as with orbital fitting. Stochastic spin noise, likely to be much larger than in radio pulsars, may hinder detection of any fast periodicity in data spans longer than a few days. These decoherence effects will dissipate as sources of fast radio bursts age, so they may evolve into objects with properties similar to Galactic magnetars.

Issues with Modeling a Tunnel Communication Channel through a Plasma Sheath.

We consider two of the most relevant problems that arise when modeling the properties of a tunnel radio communication channel through a plasma layer. First, we studied the case of the oblique incidence of electromagnetic waves on a layer of ionized gas for two wave polarizations. The resonator parameters that provide signal reception at a wide solid angle were found. We also took into account the unavoidable presence of a protective layer between the plasma and the resonator, as well as the conducting elements of the antenna system in the dielectric itself. This provides the first complete simulation for a tunnel communication channel. Noise immunity and communication range studies were conducted for a prospective spacecraft radio line.

Improvement of nano-polycrystalline diamond anvil cells with Zr-based bulk metallic glass cylinder for higher pressures: application to Laue-TOF diffractometer

ABSTRACT Single-crystal neutron diffraction provides direct information about crystal structures such as hydrogen positions and magnetic structures. However, in-situ experiments conducted under high pressure entail technical difficulties such as attenuation correction, masking of parasitic diffraction, and limitations of sample volumes and accessible directions. For this study, we improved diamond anvil cells with a tubular frame made of Zr-based bulk metallic glass and nano-polycrystalline diamond anvils for single-crystal neutron diffraction. The thicker tubular frame was confirmed through experimentation as stably generating 4.5 GPa. Its feasibility for neutron diffraction was assessed at the Laue-TOF diffractometer at the BL18 (SENJU) beamline in the MLF J-PARC using time-resolved two-dimensional detectors covering wide solid angles. In addition to ambient-pressure measurements of NH4Cl, diffraction patterns of a high-pressure phase of ice were also collected in-situ. The obtained intensities are of refinable quality sufficient for structure analysis.

Parameters of the Ion Flow of the Pulsed Vacuum Flashover Discharge

The plasma flow parameters of nanosecond vacuum flashover were examined in detail. It was found that high-velocity ion flow could be obtained using significantly more compact and cheap equipment than that used earlier. These new results will be useful to the design of new type compact plasma thrusters. It was proven that the plasma charge composition is formed at the low-voltage phase of vacuum discharge. After the analysis of experimental data, there was not found any clear dependence of the ion spectra and the degree of ionization on the flashover amplitude. The ion flow propagates in wide solid angle (up to 60°) and the ion-energy spectra contain several local maxima. The maxima positions coincide for different charge states of ions. The coincidence can be explained by the formation of plasma waves in the ion flow. The strong dependence of maximum and average ion energies on an ion charge was found. When the short interelectrode gap was used in the vacuum arc, discharge occurred at high-current discharge mode (>200 A), leading to a metal electrode consumption. A plasma acceleration model based on the occurrence of ion-acoustic shock waves was proposed.

Indoor ultrasonic positioning system transceiver modules

Positioning systems allow you to determine the position of an object. Global positioning systems use signals from satellites for this purpose, and local (indoor) positioning systems use a wide range of physical phenomena that can transmit signals. In particular, one of these phenomena is ultrasonic. The author of this article propose a solution in the form of devices for emitting and receiving an ultrasonic pulse with high sensitivity and a wide solid angle of reception/emission of ultrasonic, which can be successfully applied in an indoor positioning system.

Versatile Conical Conformal Array Antenna Based on Implementation of Independent and Endfire Radiation for UAV Applications

This paper proposed an integrated conical conformal array antenna (CCAA) for versatile application to the unmanned aerial vehicles. The CCAA consists of five flexible linear gradient subarrays with a uniform circumferential arrangement around the conical surface. It is also embedded with a pyramid reflective back-cavity (PRBC) within the conical carrier. The implementation for the three different elements of the linear gradient subarray toward impedance match and high isolation was investigated, and their identity resonant frequency (9.8 GHz) principle was developed and demonstrated. Furthermore, the PRBC was presented to improve the radiation null of the elements. A numerical 5-bit phase shifter manipulating phase difference of 72° was then combined with an 8-way power divider to obtain a fixed beam with a half power bandwidth (HPBW) of less than 24°, which indicated the backward endfire direction ( $\theta = 180 ^{\circ }$ ) in terms of three circumferential arrays (R#X). Finally, the measurements with the aid of the designed phase shifter and power divider (model SHPDW4-040140S) were conducted. The experimental results show one omnidirectional coverage (360°) in the $H$ -plane through the switching working mode of the elements with a wide scanning solid angle ( $\geqslant 72^{\circ }$ ) when these elements of the subarray hold an identity resonant frequency and exhibit a uniform performance in the point-to-point communication. The measurements of a narrow HPBW of less than 27.5° and the gain over 10.7 dBi in the endfire direction of the three circumferential arrays show great potential in backward blind space detection simultaneously.

A new XRF spectrometer using a crystal monochromator and parallel plates beam guides

Conventional x-ray fluorescence analysis (XRF) is a powerful instrumental technique for elemental quantification of samples with a wide range of matrices coming from industry, medicine, biology, environmental and archaeometry. The scattering of the x-ray tube excitation beam from the matrix is mainly responsible of the strong background in XRF spectra which restricts the detection limit (DL) to a few ppm (w/w). One possible strategy to reduce the DL is the monochromatization of the excitation beam with a crystal monochromator. In this case, the optimization of the system components is strongly required to obtain the highest excitation count rate over the sample, since it is considerable reduced by the short energy band pass of the monochromator.In the present work an optical device composed by a Si(100) crystal monochromator and two parallel plates beam guides (PPBG) was characterized and including in a conventional XRF spectrometer to improve the DLs. The PPBGs are composed by several thin glass plate reflectors placed together and separated by spacers. Inside the gap, x-rays are transmitted by total reflection contributing to the photon flux at the output of the optical device. The first PPBG reduces the divergence of the beam striking the crystal, and the second one collects the monochromatic beam that emerges from the crystal. In this way, the design of the optical device is quite compact keeping a high photon flux at the output thanks to the wide acceptance solid angle of the PPBGs. The new XRF spectrometer was applied to the analysis of biological tissues. The first results obtained in this field are shown in the present work where the performance of the spectrometer can be evaluated.

Wide Solid Angle Beam-Switching Conical Conformal Array Antenna With High Gain for 5G Applications

This letter presents a design for three-dimensional polymeride printing, printed circuit board fabrication, and a full experimental verification of a conical conformal array antenna (CCAA) with wide solid angle switching beam by a radio frequency semiconductor switch (RFSS) configuration. The CCAA consists of eight linear array antennas (LAAs) with uniform circumferential arrangement around a conical surface. Only one LAA out of the eight arrays is individually excited, operating each time by the RFSS connected to the ports of 1–8 power dividers in order to achieve the requirement of beam switching. The CCAA with beam-switching feeding network operates at 4.8 GHz according to the fifth-generation (5G) band requirements. Both a wide solid scanning angle of 0°–218° in the H-plane and a half-power bandwidth less than 16° in the E-plane are achieved. When the realized gain of each LLA is over 10 dBi, the measured peak gain of the final antenna can reach about over 11 dBi and the average radiation efficiency can reach 59.5%. This CCAA with wide solid angle beam switching and high-gain property has the potential to reduce the signal-to-noise ratio and integrate with 5G communication systems.

The DN-6 Neutron Diffractometer for High-Pressure Research at Half a Megabar Scale

A neutron diffractometer DN-6 at the IBR-2 high-flux reactor is used for the studies of crystal and magnetic structure of powder materials under high pressure in a wide temperature range. The high neutron flux on the sample due to a parabolic focusing section of a neutron guide and wide solid angle of the detector system enables neutron diffraction experiments with extraordinarily small volumes (about 0.01 mm3) of studied samples. The diffractometer is equipped with high-pressure cells with sapphire and diamond anvils, which allow pressures of up to 50 GPa to be reached. The technical design, main parameters and current capabilities of the diffractometer are described. A brief overview of recently obtained results is given.

NuSTAR Hard X-Ray Data and Gemini 3D Spectra Reveal Powerful AGN and Outflow Histories in Two Low-redshift Lyα Blobs

Abstract We have shown that Lyα blobs (LABs) may still exist even at z ∼ 0.3 , about seven billion years later than most other LABs known (Shirmer et al.). Their luminous Lyα and [O iii] emitters at z ∼ 0.3 offer new insights into the ionization mechanism. This paper focuses on the two X-ray brightest LABs at z ∼ 0.3 , SDSS J0113+0106 (J0113) and SDSS J1155−0147 (J1155), comparable in size and luminosity to “B1,” one of the best-studied LABs at z ≳ 2 . Our NuSTAR hard X-ray (3–30 keV) observations reveal powerful active galactic nuclei (AGN) with L 2 – 10 keV = ( 0.5 – 3 ) × 10 44 erg s−1. J0113 also faded by a factor of ∼5 between 2014 and 2016, emphasizing that variable AGN may cause apparent ionization deficits in LABs. Joint spectral analyses including Chandra data constrain column densities of N H = 5.1 − 3.3 + 3.1 × 10 23 cm−2 (J0113) and N H = 6.0 − 1.1 + 1.4 × 10 22 cm−2 (J1155). J0113 is likely buried in a torus with a narrow ionization cone, but ionizing radiation is also leaking in other directions, as revealed by our Gemini/GMOS 3D spectroscopy. The latter shows a bipolar outflow over 10 kpc, with a peculiar velocity profile that is best explained by AGN flickering. X-ray analysis of J1155 reveals a weakly absorbed AGN that may ionize over a wide solid angle, consistent with our 3D spectra. Extinction-corrected [O iii] log-luminosities are high, ∼43.6. The velocity dispersions are low, ∼100–150 km s−1, even at the AGN positions. We argue that this is a combination of high extinction hiding the turbulent gas and previous outflows that have cleared the escape paths for their successors.

Computational imaging, relighting and depth sensing using flexible thin-film sensors.

We wrap a thin-film luminescent concentrator (LC) - a flexible and transparent plastic foil doped with fluorescent dye particles - around an object to obtain images of the object under varying synthetic lighting conditions and without lenses. These images can then be used for computational relighting and depth reconstruction. An LC is an efficient two-dimensional light guide that allows photons to be collected over a wide solid angle, and through multiple overlapping integration areas simultaneously. We show that conventional photodetectors achieve a higher signal-to-noise ratio when equipped with an LC than in direct measurements. Efficient light guidance in combination with computational imaging approaches, such as presented in this article, can lead to novel optical sensors that collect light in a structured way and within a wide solid angle rather than unstructured through narrow apertures. This enables flexible, scalable, transparent, and lens-less thin-film image and depth sensors.

Launching jets from accretion belts

We propose that sub-Keplerian accretion belts around stars might launch jets. The sub-Keplerian inflow does not form a rotationally supported accretion disk, but it rather reaches the accreting object from a wide solid angle. The basic ingredients of the flow are a turbulent region where the accretion belt interacts with the accreting object via a shear layer, and two avoidance regions on the poles where the accretion rate is very low. A dynamo that is developed in the shear layer amplifies magnetic fields to high values. It is likely that the amplified magnetic fields form polar outflows from the avoidance regions. Our speculative belt-launched jets model has implications on a rich variety of astrophysical objects, from the removal of common envelopes to the explosion of core collapse supernovae by jittering jets.

Collection and spectral control of high-order harmonics generated with a 50 W high-repetition rate Ytterbium femtosecond laser system

We generate high-order harmonics with a 50 W, Yb femtosecond fiber laser system operating at 100 kHz in a tight focusing configuration. We achieve a high photon flux even with pulses longer than 500 fs. We collect the diverging extreme ultraviolet (XUV) harmonic beam in a 35 mrad wide solid angle by using a spectrometer designed to handle the high thermal load under vacuum and refocus the XUV beam onto a detector where the beam is characterised or can alternatively be used for experiments. This setup is designed for a 50 eV XUV bandwidth and offers the possibility to perform XUV-IR pump probe experiments with both temporal and spectral resolution. The high-order harmonics were generated and optimized at 100 kHz by using several gas target geometries (a gas jet and a semi-infinite gas cell) and several gases (argon, krypton, xenon) that provide XUV beams with different characteristics. After the spectrometer and for high-order harmonic generation (HHG) in xenon, we detect more than 4 × 1010 photons per second over four harmonics, that is a useful XUV power on target of 0.1 μW. This corresponds to the emission of more than 1 μW per harmonic at the source and we achieved a similar flux with both the semi-infinite cell and the jet. In addition, we observe a strong spectral selectivity when generating harmonics in a semi-infinite gas cell as few harmonics clearly dominate the neighbouring harmonics. We attribute this spectral selectivity to phase matching effects.

Transition radiation at radio frequencies from ultrahigh-energy neutrino-induced showers

Coherent radiation at radio frequencies from high-energy showers fully contained in a dense radio-transparent medium - like ice, salt or regolith - has been extensively investigated as a promising technique to search for ultra-high energy (UHE) neutrinos. Additional emission in the form of transition radiation may occur when a neutrino-induced shower produced close to the Earth surface emerges from the ground into atmospheric air. We present the first detailed evaluation of transition radiation from high-energy showers crossing the boundary between two different media. We found that transition radiation is sizable over a wide solid angle and coherent up to $\sim$ 1 GHz. These properties encourage further work to evaluate the potential of a large-aperture UHE neutrino experiment based on detection of transition radiation.