The Japanese space gravitational wave antenna; DECIGO

DECi-hertz Interferometer Gravitational wave Observatory (DECIGO) is the future Japanese space gravitational wave antenna. DECIGO is expected to open a new window of observation for gravitational wave astronomy especially between 0.1 Hz and 10 Hz, revealing various mysteries of the universe such as dark energy, formation mechanism of supermassive black holes, and inflation of the universe. The pre-conceptual design of DECIGO consists of three drag-free spacecraft, whose relative displacements are measured by a differential Fabry– Perot Michelson interferometer. We plan to launch two missions, DECIGO pathfinder and pre- DECIGO first and finally DECIGO in 2024

DECIGO pathfinder

DECIGO pathfinder (DPF) is a milestone satellite mission for DECIGO (DECi-hertz Interferometer Gravitational wave Observatory) which is a future space gravitational wave antenna. DECIGO is expected to provide us fruitful insights into the universe, in particular about dark energy, a formation mechanism of supermassive black holes, and the inflation of the universe. Since DECIGO will be an extremely large mission which will formed by three drag-free spacecraft with 1000m separation, it is significant to gain the technical feasibility of DECIGO before its planned launch in 2024. Thus, we are planning to launch two milestone missions: DPF and pre-DECIGO. The conceptual design and current status of the first milestone mission, DPF, are reviewed in this article

The status of DECIGO

DECIGO (DECi-hertz Interferometer Gravitational wave Observatory) is the planned Japanese space gravitational wave antenna, aiming to detect gravitational waves from astrophysically and cosmologically significant sources mainly between 0.1 Hz and 10 Hz and thus to open a new window for gravitational wave astronomy and for the universe. DECIGO will consists of three drag-free spacecraft arranged in an equilateral triangle with 1000 km arm lengths whose relative displacements are measured by a differential Fabry-Perot interferometer, and four units of triangular Fabry-Perot interferometers are arranged on heliocentric orbit around the sun. DECIGO is vary ambitious mission, we plan to launch DECIGO in era of 2030s after precursor satellite mission, B-DECIGO. B-DECIGO is essentially smaller version of DECIGO: B-DECIGO consists of three spacecraft arranged in an triangle with 100 km arm lengths orbiting 2000 km above the surface of the earth. It is hoped that the launch date will be late 2020s for the present

Amorphous Gallium Oxide as an Improved Host for Inorganic Light-Emitting Thin Film Semiconductor Fabricated at Room Temperature on Glass

We report new amorphous oxide semiconductor (AOS)-based thin film phosphor, Eu-doped a-Ga2Ox (a-GO:Eu), to solve the issues of previously reported a-In-Ga-Zn-O: Eu (a-IGZO:Eu). The internal quantum efficiencies (IQE) of a-GO:Eu (2.3% for unannealed, 8.3% for annealed films) are improved from those of a-IGZO:Eu (0.9% and 1.6%, respectively) because of the much wider bandgap (4.26 eV), subsequent low residual electron density, and higher available annealing temperature. We found that the annealing temperature to improve IQE is limited by crystallization temperature. Another issue of a-IGZO:Eu is that the initial state of Eu3+ 4f is deeper than the valence band maximum (VBM), which is not suitable for light-emitting diode. We expected that Eu3+ 4f would locate above the VBM in a-GO:Eu because the VBM of a-Ga2Ox is similar to 0.8 eV deeper than that of a-IGZO. However, resonant photoemission spectroscopy revealed that the Eu 4f states are bound more to the O 2p valence band than to the vacuum level, and the Eu3+ 4f states in a-GO:Eu are still buried in the valence band. (C) 2017 The Electrochemical Society. All rights reserved

Special Beam Position Monitor With 8-Button Electrodes

To maintain the optimum collision condition of the two beams, two special BPMs with 8-button electrodes, called OCTOPOS, were installed inside the super-conducting quadrupole magnets (QCSs) at the interaction region (IR) of KEKB. We have commissioned the OCTOPOS BPMs for simultaneous measurements of both the electron and positron beam positions from their composite signal. A collision orbital feedback using OCTOPOS has been put into practical application since last November. The position of each beam is separable by analyzing the nonlinearity of the pickup sensitivity from the signal amplitudes of the eight button electrodes. This report describes the characterization of the OCTOPOS and its performance

SnAs with the NaCl-type Structure: Type‑I Superconductivity and Single Valence State of Sn

We examined the superconductivity of SnAs and the valence state of Sn in its lattice with an expectation that SnAs and related compounds with the NaCl-type structure might exhibit superconductivity at a high critical temperature (<i>T</i>_c), as (Ba_1–<i>x</i>K_<i>x</i>)­BiO₃ (BKBO) does, owing to the similar crystallographic and chemical environments of Sn in SnAs and Bi in BKBO. Although SnAs had low <i>T</i>_c, 3.58 K, we clarified two important characteristics: First, SnAs exhibits weakly coupled type-I superconductivity. Second, Sn has a single valence state, like Sn³⁺(5s¹), originating from there being only one crystallographically independent site in its NaCl-type structure. This unconventional single chemical state of Sn in SnAs would explain the superconductivity of SnAs with a three-dimensional NaCl-type structure, rather than a two-dimensional layered structure

Low-temperature-processable amorphous-oxide- semiconductor-based phosphors for durable light-emitting diodes

In this study, we fabricated light-emitting diodes (LEDs) on glass substrates at a maximum process temperature of 200 degrees C using amorphous oxide semiconductor (AOS) materials as emission layers. Amorphous gallium oxide films doped with rare-earth elements (Eu, Pr, and Tb) were employed as AOS emission layers, and the LEDs emitted clear red, green, and pink luminescence upon direct-current application even in the ambient environment. Resonance photoelectron spectroscopy revealed the difference in the electronic structure of the films for each rare-earth dopant, suggesting different emission mechanisms, viz., electron hole recombination and impact excitation. Although it is widely believed that amorphous materials are unsuitable for use as emission layers of LEDs because of their high concentrations of mid-gap states and defects, the developed rare-earth-doped AOS materials show good performance as emission layers. This study provides opportunities for the advancement of flexible display technologies operating in harsh environments. Published under an exclusive license by AIP Publishing