A new principle for determining the maximum number of neutrons in a given isotope chain is found by a research group that includes a scientist from the ASRC. A first-principles nuclear-structure calculation making a full use of supercomputers points to a crucial role of binding energy that is changing with the neutron number due to nuclear shape transition. Despite very short β-decay lifetimes, nuclei with a very large neutron number are created on the way of nucleosynthesis, and the present finding could greatly contribute to clarifying the origin of elements on earth.
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A research team led by Dr. Yurina Sekine at the Advanced Science Research Center and the Materials Sciences Research Center has developed a crosslinking method using freeze-concentration and used it to synthesize a new type of carboxymethyl cellulose nanofiber (CMCF) hydrogel with high water content, high compressive strength, and high compressive recoverability. The hydrogels were prepared by adding an aqueous solution of citric acid to a frozen CMCF and then thawing the sol. This gelling process is called freeze crosslinking. The physically crosslinked CMCF hydrogels are non-toxic, metal-free, and simple to prepare, and thus they may be useful as sustainable materials in various fields.
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A research team led by Senior Scientists Satoru Okayasu and Jun’ichi Ieda at the Advanced Science Research Center has demonstrated that a "spin thermoelectric (STE) device", which generates electricity from heat, has a very high radiation tolerance. Recently, STE devices relying on electron spins have been developed, and are expected to outperform existing technologies in terms of flexibility in design, low environmental impact, and economic efficiency. However, it has not yet been confirmed whether the device's performance can be maintained in the harsh environment where radioisotopes coexist. To address this, in this study, the service life of the device was estimated by irradiating it with heavy ions, and it was confirmed that the performance of the device would not deteriorate for several hundred years even if spent nuclear fuel was used as a heat source. In the future, it is expected to contribute to the development of new technologies for the safe and effective utilization of waste heat from spent nuclear fuels in the radiation environment.
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A new study by researchers from Riken Center for Emergent Matter Science, Japan Atomic Energy Agency, Institute for Solid State Physics (U. of Tokyo), Ecole Polytechnique Fédérale de Lausanne, and Hitachi Ltd. shows that when surface acoustic waves propagate past a thin magnetic film, there is a large difference in the absorption of the waves by the magnet depending on whether the waves are incident from the right or left side of the film. Although such a rectification effect of magnets has been known, the previous studies suggested that the effect was generally small, and would become weaker for thinner films that are likely to be used in potential applications. The new experimental data indicates a complete disappearance of absorption for an incident wave from one side while maintaining a strong absorption for the other in an ultra-thin magnetic film of 1.6 nm (a billionth of a meter), which imples a 100% efficiency of the rectification effect. The discovery could prove to be a promising way forward in the pursuit of insulator-based communications devices by offering a rectification function for acoustic waves, which acts analogously to a diode for electronic circuits.
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A group of researchers including scientists from the Japan Atomic Energy Agency (JAEA) used the spin-polarized Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory in the United States to show that, in polarized proton-proton collisions, neutral pions emitted in the very forward area of collisions—where direct interactions involving quarks and gluons are not applicable—still have a large degree of left-right asymmetry. This finding suggests that the previous consensus regarding the generation of particles in such collisions needs to be reevaluated.
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H. Chudo (deputy chief researcher, JAEA), R. Takahashi (Assistant Professor, Ochanomizu University (at the time of research, post-doctoral researcher, JAEA)), M. Matsuo(Associate Professor, Chinese Academy of Sciences (at the time of research, deputy chief researcher, JAEA)), S. Maekawa, (Senior Researcher, RIKEN (at the time of research, director of ASRC, JAEA)), E. Saito, (Professor, the University of Tokyo), et al, elucidate the mechanism of the hydrodynamic power generation via a spin current in a channel with a micro meter order, and discovere the efficiency of power gneration significantly enhances with smaller size of the channnel. The flow in a fine channel becomes a laminar flow, and liquid movement like a vortex is widely distributed throughout the channel. This leads to more suitable characteristics for miniaturization and increased power generation efficiency. The basic theory of fluid power generation via spin current was predicted by M. Matsuo in 2017. In this research, we have experimentally demonstrated that the power generation efficiency was improved about 100,000 times in the laminar flow region. The results of this research indicate that the fluid power generation via the spin current will be greatly improved by miniaturization. In addition, no additional equipment is required inside or outside the flow cannel. Therefore, it is expected to be applicable to nanofluidic devices and flow meters for minute flow.
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The JAEA, in collaboration with the University of Tokyo and RIKEN, has clarified the peculiar behavior of conduction electrons in exchange for accepting a strongly correlated state in the complex phase transition phenomenon of Cerium-Antimony (CeSb) called "devil's staircase". This research group investigated the mechanism that induces the "devil's staircase" by measuring spin arrangements and conduction electrons using ultra-high resolution laser photoelectron spectroscopy. As a result, it is shown that conduction electrons, which are supposed to move freely, form a pseudo-gap state to obtain energy gain and eventually causes the "devil's staircase". The strong correlation between electrons and spins clarified in this study can potentially be applied to spintronics magnetic material design, because conduction electrons are controlled by the spin arrangement to function as the operating principle of devices like magnetic memories.
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We have investigated the atomic structure of superconducting Ca-intercalated bilayer graphene on a SiC (0001) substrate using total-reflection high-energy positron diffraction. By comparing the experimental rocking-curves with ones calculated for various structural models using a full-dynamical theory, we have found that Ca atoms are intercalated in the graphene-buffer interlayer, rather than between the two graphene layers. From transport measurements, the superconducting transition was observed to be at T_c^onset = 4 K for this structure. This study is the first to clearly identify the relation between the atomic arrangement and superconductivity in Ca-intercalated bilayer graphene.
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Electric current has been used to send electricity to far distant places. On the other hand, spin current, a flow of electron spin, can in principle also send angular momentum to distant places. In a magnet, there is a universal spin carrier called a spin wave, a wave-type excitation of magnetization. Since spin waves exhibit a long propagation length, it should be able to send angular momentum that can generate torque and force at a distant place: a new function of magnets. Here we observe mechanical angular momentum transmission and force generation due to spin waves injected into Y3Fe5O12 by the spin-Seebeck effect. The spin-wave current, transmitted through a Y3Fe5O12 micro cantilever, was found to create a mechanical force on the cantilever as a non-local reaction of the spin-Seebeck effect. Spin-wave current can be generated remotely even in open circuits, and it can be used to drive micro mechanical devices.
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We propose a topological characterization of Hamiltonians describing classical waves. Applying it to the magnetostatic surface spin waves that are important in spintronics applications, we settle the speculation over their topological origin. For a class of classical systems that includes spin waves driven by dipole-dipole interactions, we show that the topology is characterized by vortex lines in the Brillouin zone in such a way that the symplectic structure of Hamiltonian mechanics plays an essential role. We define winding numbers around these vortex lines and identify them to be the bulk topological invariants for a class of semimetals. Exploiting the bulk-edge correspondence appropriately reformulated for these classical waves, we predict that surface modes appear but not in a gap of the bulk frequency spectrum. This feature, consistent with the magnetostatic surface spin waves, indicates a broader realm of topological phases of matter beyond spectrally gapped ones.
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An international research team led by JAEA, Gifu University, J-PARC center, and KEK has detected a new hypernucleus of Bellilium having additional two Lambda particles, so-called "double Lambda hypernucleus (DLH)". One of the goals of modern physics is to understand the mechanism of matter formation through the hierarchical structure from quarks to nuclei. The studies of hypernuclei are essential issues because they extend our knowledge of the ordinary nucleus to the more general nucleus having strange-quark. Particularly, systematic studies of various DLHs are important and challenging issues. We performed an experiment named E07 at J-PARC. It was designed to detect 100 times higher statistics of DLH compared to past experiments with the high-intensity beam of J-PARC. In this experiment, we detected the 2nd identified DLH event named "MINO" and measured its mass. We reconstructed the Lambda-Lambda interaction from the mass. The strength of the interaction was different from that of the 1st identified DLH, so-called "NAGARA". This result is the 1st example that Lambda-Lambda interaction has changed due to the nuclear structure. We will continue the search for new DLHs. DLHs are recorded in photographic emulsion sheets and searched under optical microscopes with automated image recognition. We expect to detect several more new DLHs within a few years. Furthermore, we intend to accelerate the DLH hunting with a new technique, so-called the "Overall scanning method". This result may lead to the understanding of the internal state of neutron stars. Many scientists predict Lambda particles should appear spontaneously in neutron stars by nuclear processes in the high-pressure environment. This result shall be used to validate the scenarios.
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Researchers in U. Tokyo, UEC, and JAEA succeeded in the controlling the high speed motion of a magnetic domain wall (DW) by voltage application. The technology to drive the DW at a higher speed is indispensable for improving the performance of the magnetic memory. To this end, applying voltages to the magnet is a promissing method with high energy efficiency but previous reports were limited to the extremely slow speed operation of 1 mm/sec or less. In this research, it was demonstrated that the DW speed in the region exceeding 100 m/sec is shifted by the voltage. The success in a practical speed region for a memory device is the first time and it opens a way to realize a "race track memory" expected as the ultimate storage memory with high speed, large capacity, high durability.
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We find the strong correlation between ferromagnetic fluctuations and pressure-induced superconductivity in uranium ferromagnetic superconductor UGe2. It has considered that the ferromagnetism and the superconductivity compete with each other. However, the coexistence of both phases has been discovered in several uranium compound. We show that the ferromagnetic fluctuations enhanced under high pressure may take an important role for the superconductivity. We hope that this study contributes to further developments for a complete understanding of the superconductivity.
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Researchers in JAEA and RIKEN have developed a versatile angular momentum measuring apparatus to observe the temperature dependent spin of electrons (angular momentum) by rotating the sample at high speed. Moreover, they investigated the magnitude of angular momentum using this apparatus, and observed that the angular momentum disappears with a specific magnetic material. The magnetic reversal process and the angular momentum are closely related, and the magnetic reversal speed is accelerated when the angular momentum is small. By measuring the angular momentum of various materials with this apparatus, it is expected to search for materials for the next generation high speed magnetic devices.
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JAEA has discovered a new magneto-optical material, (Fe,FeCo)-(Al-, Y-fluoride) nano-granular films exhibiting giant Faraday effect, 40 times larger than that of Bi-YIG, which has been used for optical communications since 1972. These newly discovered material will contribute greatly to the miniaturization and integration of optical devices.
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JAEA has succeeded to clarify the mechanism of superconductivity in uranium compound URu₂Si₂ using JAEA facility; why the superconductivity of this compound can survive under the extremely high magnetic field. So far, experimental resolusion has not been enough due to the difficulty of treating the nuclear fuel material. This result can lead development of more useful superconducting magnet.
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A theory of spin current noise has been constructed in a normal-metal/ ferromagnet bilayer systems. The theory is applied to estimate heat in the spin pumping by micro-waves. It may also be used to obtain high efficiency spin current generation technology.
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Scientists at Japan Atomic Energy Agency, RIKEN, and Brookhaven National Laboratory shocked by results of spinning protons striking different sized atomic nuclei at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory.
Neutrons produced when a spinning proton collides with another proton come out with a slight rightward-skew preference.
But when the spinning proton collides with a much larger gold nucleus, the neutrons' directional preference becomes larger and switches to the left.
The scientists will execute a new series of experiments colliding polarized protons with other kinds of nuclei to study the electromagnetic interaction effect.
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ISSP, University of Tokyo and JAEA have found an ordering of electron orbitals at the surface of a heavy fermion superconductor CeCoIn5. By using the highly stabilized scanning tunneling microscopy, they succeeded to directly observe the orbital ordering in real space for the first time.

Keio University, Tohoku University, and JAEA succeded in generating "spin current", the flow of magnets by injecting Rayleigh wave into copper. This result is expected to make a significant contribution as a high performance, power saving, and inexpensive rare metal free technology of magnetic devices, which are widely installed in portable information terminals such as smart phones.
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JAEA will obtain einsteinium isotope ²⁵⁴Es (element 99) from Oak Ridge National Laboratory (ORNL). Using the experiemntal setups developed by JAEA in the tandem facility and the SPring-8, experiments such as fission mechanism and hydration structure are planned.

Spinons behave as a Tomonaga–Luttinger liquid at low energy, and the spin system is often called a quantum spin chain. Here we show that a quantum spin chain generates and carries spin current, which is attributed to spinon spin current.
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Developing optically transparent magnets at room temperature is an important challenge. They would bring many innovations to various industries, not only for electronic and magnetic devices but also for optical applications. Here we introduce FeCo-(Al-fluoride) nanogranular films exhibiting ferromagnetic properties with high optical transparency in the visible light region.
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We have determined the structure of germanene, germanium version of graphene, on an aluminum substrate using total-reflection high-energy positron diffraction (TRHEPD) method. The present study revealed that germanene has an asymmetric structure.
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A new method to obtain fission fragment mass distributions using multi-nucleon transfer reactions was established, which generates data for more than fourteen nuclei at once including neutron-rich nuclei not investigated so far. A fluctuation-dissipation model successfuly explains the measured data.
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In order to gently regenerate village forests without destroying forest ecosystem, a new technology for migration control of radioactive cesium has been developed. By scattering bentonite that adsorbs cesium on slope grounds covered by leaf soil, the uptake of cesium to plants is suppressed. The bentonite adsorbing cesium is transferred by rainwater flow and then captured by interpolyelectrolyte complex (self-assembly of polyelectrolytes having opposite charge by electrostatic interaction).
Patent-pending

On the basis of large-scale nuclear-structure calculations using the K supercomputer, the most reliable value of the nuclear matrix element for neutrinoless ββ decay in Ca-48 is provided by a collaboration group among the University of Tokyo, Japan Atomic Energy Agency, and other institutes. This data will strongly narrow the range of neutrino masses when the neutrinoless ββ decay in Ca-48 is observed.
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Collaborative research team of JAEA and KEK experimentally verified using total-reflection high-energy positron diffraction (TRHEPD) that the spacing between graphene and metal substrate depends on the substrate material.
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Collaborative research team of KEK, Hokkaido University, and JAEA experimentally determined the surface structure of TiO2 photocatalyst using total-reflection high-energy positron diffraction (TRHEPD)
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Our latest research achievement "Electrical generation from quantum mechanical spinning motion in a liquid metal", press released on November 03, 2015, was featured in News&Views of Nature Physics and Nature Materials.
Nature Materials
Nature Physics

An international collaboration led by Tohoku University, High Energy Accelerator Research Organization (KEK), and Japan Atomic Energy Agency (JAEA) found fundamental symmetry called "charge symmetry" is broken by adding a "strange" particle, Lambda, to a nucleus in an experiment at J-PARC Hadron Experimental Facility.
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In spin glass metals, where localized moments are polarized in random directions, the relative dynamics between the localized moment and the conduction electron spin is successfully probed by the spin Hall effect. Such spin dynamics is very difficult to be detected even by the superconducting quantum interference device (SQUID), the most sensitive magnetometer at the present stage. Such technique can be applied to develop the highly sensitive magnetic sensors.
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The team found a new method of power generation by using electron spinning motion in a liquid metal via the quantum mechanical coupling between electron and fluid vorticity. The result can be used as an electric generator and a spin generator in, e.g., micro-electromechanical system free from magnetic fields.
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We have succeeded the development of synthesis process of novel composite nanotubes, which are consisted of different crystal states or new microstructures, using ion irradiation technique.
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・First demonstration of the spin-Hall effect in a superconductor. ・More than 2000 times enhancement of the effect has been achieved compared to the normal conductor case. ・This finding opens the door to next-generation spintronics devices such as a "spin-meter" that magnifies and detects tiny spin signals.
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Reentrant superconducitivity has been discovered in uranium based compound URhG under strong magnetic fields. We have revealed the noevel mechansim of this exotic phenomenon by means of Nuclear Magnetic Resonance (NMR) technique.
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We report that the experimentally obtained the first ionization potencial of the heaviest actinide, lawrencium (Lr, atomic number 103), is 4.96 eV. The value was measured with Lr-256 (half-life 27 seconds) using an efficient surface ion-source and a radioisotope detection system coupled to a mass separator at the JAEA tandem accelerator. The measured ionization potencial is in excellent agreement with the value predicted here by state-of-the-art relativistic calculations.
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We have constructed a folding (A4-size) nuclear chart, “JAEA Chart of the Nuclides 2014,” including the latest experimental (3,150 points) and theoretical (1,578 points) decay data for nuclear science experts and the general public.

A conversion of light energy into spin currents in magnetic insulators is demonstrated for the first time with the aid of "surface plasmon", a collective excitation of electrons in metal nanoparticles under light illumination.
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We have theoretically shown that electron-electron correlation is necessary to reproduce the experimental results of the spin Hall effect in Ir-doped Cu.
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Concerning the phonon Hall effect, it has not been clarified the mechanism why a heat current is changed by a magnetic field. We theoretically show that this effect is due to resonant skew scattering of phonons from a tiny amout of magentic impurities.
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Thermomagnetic effect was investigated on an ultra-clean single crystal of a uranium superconductor URu₂Si₂. Colossal thermomagnetic response a million times larger than the theoretical prediction has successfully been detected. This observation proofs the superconducting fluctuation in this material.
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We have revealed the chemical states of radioactive cesium in the sewage sludge ashes produced after the Fukushima Daiichi nuclear power plant accident and have succeeded in recovering more than 90 % of radioactive cesium in the ashes by pre-pulverizing the ashes to particles less than 1 µm and heating them in acid solutions.
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Mottled electronic state is found in an Yb-based compound around a magnetic field induced quantum critical phase transition at low temperatures.
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For the first time, a chemical bond was established between a superheavy element – seaborgium (element 106) in the present study – and a carbon atom by an international collaboration with research groups from Univ. Mainz, GSI and RIKEN. Seaborgium were converted into seaborgium hexacarbonyl complexes. Its gaseous properties and adsorption to a silicon dioxide surface were studied, and compared with similar compounds of neighbors of seaborgium in the same group of the periodic table.
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We have developed an novel spectroscopic technique, using high brilliant X-rays provided by SPring-8, to study synergy effect of radiation and water on the processes of DNA damage induced by radiation.
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The newly developmed material is a thin-film dielectric material consists of metal and insulator phases, in which nano-magnetic particles have been dispersed in a inslator matrix. This so-called nanogranular material shows giant dielectric and magnetoelectric responses at room temperature.
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We have found new phenomenon of magnetism in uranium ferromagnetic superconductors UGe2 and URhGe where the ferromagnetism and superconductivity co-exist.
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Deformation of the crystal lattice was detected in the hidden-order phase of URu₂Si₂ by using an ultra high-resolution crystallography with synchrotron radiation at SPring-8.
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An unknown magnetic structure in uranium compound URu₂Si₂ induced by high field over 35 tesla, has been determined by means of nuclear magnetic resonance technique. The experiment was performed using the world's strongest magnetic field in National High Magnetic Field Laboratory (NHMFL) in Tallahasee, USA.
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By using the most intense pulsed muon beam at J-PARC MUSE(MUon Science Establishment), we successfully demonstrate a depth-profile analysis of light elements (B, C, N, and O) from several mm-thick layered materials and non-destructive bulk analyses of meteorites containing organic materials.
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We have developed a unique conceptual measurement system of nucler spin of materials in rotoational speed of 10000 times per 1second based on nuclear magnetic resonance method.
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2014, Commendation for Science and Technology by the Minister of Education, Culture, Sports, Science and Technology
Kawasuso, Group Leader, and his colaborators received the above award.

We improved the total reflection positron diffraction method by enhancing the brightness of positron beam at KEK slow positon facility.
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We found that radiation damage to DNA could affect non-irradiated normal chromosomes to induce genetic instability. This project has been perfomed by collaboration with Prof. Seiji Kodama in Osaka prefectrue univ. (Pregident: Taketoshi Okuno)
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This prize is one of the prestigious prize in Science for Japanese scientist. Yomiuri Tchno Forum selects luminary scientists 3 or so per a year.
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