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Matsumoto, Y.

Publications and source records attributed to Matsumoto, Y..

11 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Limits on the Low-energy Electron Antineutrino Flux from the Brightest Gamma-Ray Burst of All Time

The electron antineutrino flux limits are presented for the brightest gamma-ray burst (GRB) of all time, GRB221009A, over a range of 1.8–200 MeV using the Kamioka Liquid Scintillator Antineutrino Detector. Using multiple time windows ranging from minutes to days surrounding the event to search for electron antineutrinos coincident with the GRB, we set an upper limit on the flux under the assumption of several power-law neutrino source spectra, with power-law indices ranging from 1.5 to 3 in steps of 0.5. No excess was observed in any time windows ranging from seconds to days around the event trigger time T 0 . For a power-law index of 2 and a time window of T 0 ± 500 s, a flux upper limit of 2.34 × 10 9 cm −2 was calculated. The limits are compared to the results presented by IceCube.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

Homogeneous reduced moment in a gapful scalar chiral kagome antiferromagnet

We present a quantitative experimental investigation of the scalar chiral magnetic order with in Nd 3 Sb 3 Mg 2 O 14 . Static magnetization reveals a net ferromagnetic ground state, and inelastic neutron scattering from the hyperfine coupled nuclear spin reveals a local ordered moment of 1.76(6) μB, just 61(2)% of the saturated moment size. The experiments exclude static disorder as the source of the reduced moment. A 38(1)μeV gap in the magnetic excitation spectrum inferred from heat capacity rules out thermal fluctuations and suggests a multipolar explanation for the moment reduction. Furthermore, we compare Nd 3 Sb 3 Mg 2 O 14 to Nd pyrochlores and show that Nd 2 Zr 2 O 7 is in a spin fragmented state using nuclear Schottky heat capacity.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

TIME EVOLUTION OF KELVIN–HELMHOLTZ VORTICES ASSOCIATED WITH COLLISIONLESS SHOCKS IN LASER-PRODUCED PLASMAS

We report experimental results on Kelvin–Helmholtz (KH) instability and resultant vortices in laser-produced plasmas. By irradiating a double plane target with a laser beam, asymmetric counterstreaming plasmas are created. The interaction of the plasmas with different velocities and densities results in the formation of asymmetric shocks, where the shear flow exists along the contact surface and the KH instability is excited. We observe the spatial and temporal evolution of plasmas and shocks with time-resolved diagnostics over several shots. Our results clearly show the evolution of transverse fluctuations, wavelike structures, and circular features, which are interpreted as the KH instability and resultant vortices. The relevant numerical simulations demonstrate the time evolution of KH vortices and show qualitative agreement with experimental results. Shocks, and thus the contact surfaces, are ubiquitous in the universe; our experimental results show general consequences where two plasmas interact.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Simple synthesis of PbSe nanocrystals and their self-assembly into 2D ‘flakes’ and 1D ‘ribbons’ structures

Highlights: • PbSe is obtained in a simple way by the co-precipitation method at low-temperature. • The structural, morphological and optical properties of PbSe were studied. • Adding NH{sub 4}OH to the precursor solutions influences on the morphology. • 2D- and 1D-PbSe structures assemble by oriented attachment. • PbSe can be a potential candidate for thermoelectric applications. - Abstract: This work presents a simple and low-temperature method to prepare a variety of Lead selenide (PbSe) nanostructures, using aqueous solutions of Pb(NO{sub 3}){sub 2} and NaHSe. Nanostructures with different morphology were obtained by varying the Pb:Se molar ratio, as well as the mixing sequence of NH{sub 4}OH with either Pb(NO{sub 3}){sub 2} or NaHSe. Nanoparticles with different shapes (spherical and octahedral), and self-assembled structures (flakes and ribbons) were observed by Transmission Electron Microscopy. X-ray results confirmed that the PbSe rock-salt crystalline structure was obtained for all of the prepared samples. The crystal size is in the order of 7.3 to 8.9 nm for single nanocrystals. The absorption spectra of the samples show exciton absorption bands at 1395 nm and 1660 nm. This material could be used to develop more advanced structures for thermoelectric generators.

36 MATERIALS SCIENCE↗
NASA NTRS1988

Studies on pressure response of gas bubbles contributions of condensed droplets in bubbles generated by a uniform nucleation

The response of a tiny gas bubble under reduced pressure is investigated in its relation to cavitation. Equations of motion are formulated for gas mixtures inside the bubble and numerical calculations performed for several examples. The conclusions are as follows: (1) at the onset of bubble growth, the gas mixture inside it adiabatically expands and the temperature decreases. Condensed droplets appear inside the gas mixture due to a uniform nucleation and the temperature recovers, thus the motion of the bubble is apparently isothermal; (2) the evaporation and condensation coefficient largely affects bubble motions (maximum radius, period and rate of attenuation of the bubble oscillation) including the uniform contraction; (3) the oscillation period of the bubble is longer as the equilibrium bubble radius is larger when the surrounding pressure decreases stepwise. In this circumstance the temperature inside the bubble is kept constant due to condensation evaporation phenomena and is nearly isothermal; and (4) when the surrounding pressure decreases in a stepwise fashion, the critical pressure bubble radius relation becomes closer to that for the isothermal process if the bubble radius is larger than 8 microns.

Matsumoto, Y.↗
NASA NTRS1984

Motorized Cyrogenic Valve

Remotely-controlled cryogenic valve operates over temperature range from room temperature to 2 K. Valve used in helium dilution refrigerators, cryostats and adiabatic-demagnetization refrigerators.

Salerno, L.↗
NASA NTRS1980

Video-compression scheme

Video compression circuit divides picture into elements transmitted at reduced data rate. By sampling elements along diagonals in N-by-N picture blocks, system gives picture quality comparable to that of standard television and superior to most pseudorandom sampling schemes.

Lum, H., Jr.↗
NASA NTRS1980

Microprocessor-controlled receiver

Microprocessor and radio receiver are combined in low-cost, high performance, data communications receiver. Hybrid receiver automatically acquires and tracks UHF channels despite low signal-to-noise ratios, fading signal strengths, and high Doppler offset. It also performs digital bit synchronization, which has traditionally required separate unit.

Grant, T. L.↗
NASA NTRS1977

Sampling video compression system

A system for transmitting video signal of compressed bandwidth is described. The transmitting station is provided with circuitry for dividing a picture to be transmitted into a plurality of blocks containing a checkerboard pattern of picture elements. Video signals along corresponding diagonal rows of picture elements in the respective blocks are regularly sampled. A transmitter responsive to the output of the sampling circuitry is included for transmitting the sampled video signals of one frame at a reduced bandwidth over a communication channel. The receiving station is provided with a frame memory for temporarily storing transmitted video signals of one frame at the original high bandwidth frequency.

Matsumoto, Y.↗
NASA NTRS1977

Remote moisture-content balance

Automatic balance monitors wetness of wood samples to determine forest fire hazards. Fuel model consists of four wooden dowels that will absorb precipitation moisture and humidity at rate related to moisture absorption by forest wood. Model wetness is determined from weight changes as monitored by electronic balance.

Blomseth, R. A.↗