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First measurement of antineutrinos from spent nuclear fuel confirms emissions persist after reactor shutdown

Even when the lights go out and nuclear reactors are turned off, the story inside the reactor core still has a great deal to tell. Radioactive, long-lived fission products continue to decay for months or even years, producing a faint flux of a specific type of particle known as antineutrinos. (Anti)neutrinos are the lightest and most elusive known particles in the universe, allowing them to escape unhindered from both the reactor and the surrounding shielding.

Researchers in the Double Chooz collaboration have now measured this residual antineutrino emission for the first time. The study, which was published in Physical Review Letters, was led by Anthony Onillon and Thierry Lasserre from the Max-Planck-Institut für Kernphysik (MPIK) in Heidelberg, Germany.

The results demonstrate that antineutrino detectors can probe nuclear reactors even during shutdown periods, opening new perspectives for reactor monitoring, nuclear safety and safeguards.

Quantum fluid reveals hidden states that can be switched with a magnetic field

Bose-Einstein condensates (BECs) are often described as a “fifth state of matter”: a quantum state in which many particles lose their individual identities and behave as one collective object. For more than 60 years, researchers have sought to create such condensates from excitons—electron-hole pairs—as a solid-state route to macroscopic quantum coherence, which is useful for quantum technologies. This has been difficult to realize in controllable semiconductor devices because optically generated excitons have very short lifetimes of around a billionth of a second, and BECs are normally attained with ultracold gases in a vacuum.

But now, a team led by Lawrence Berkeley National Laboratory (Berkeley Lab) has observed a tunable BEC of excitons at high temperature in an atomically thin semiconductor. The findings, published in Nature, reveal not only that the excitons form a BEC but also that the condensate has an internal structure that can be switched by a magnetic field.

The work enables a new platform for studying quantum fluids in solid materials. (A quantum fluid is an exotic state of matter in which gases of electrons or other particles behave collectively like a fluid.) It also has implications for future quantum simulations, coherent optoelectronics in next-generation telecommunications and computing, and exciton-based devices enabling faster, more efficient computing.

Two materials, one photonic chip: Unlocking a new way to generate light frequencies

Modern photonic chips can pack sophisticated optical functions onto devices smaller than a fingernail. They are increasingly used to generate, manipulate and measure light for applications ranging from communications to sensing. But most of these chips rely on a single material to do the heavy lifting, limiting the range of optical effects they can produce.

Researchers have now demonstrated a different approach: letting two materials share the work. As reported in Advanced Photonics, scientists combined two nonlinear optical effects that normally occur separately. Their device uses a silicon nitride core to generate optical frequency combs while a surrounding silica layer produces Raman scattering.

By harnessing the strengths of both materials at once, the team created a new type of integrated photonic device capable of generating broad ranges of light frequencies on a chip.

Nano-optics: New mechanism for channeling light waves discovered in natural hyperbolic materials

Researchers at the 4th Physics Institute of the University of Stuttgart and the Istituto Italiano di Tecnologia (IIT) in Milan have demonstrated a new mechanism for directing light in a naturally hyperbolic van der Waals material without conventional nanofabricated waveguides. The discovery opens new possibilities for integrated photonics, on-chip optical communication and future quantum technologies. The paper is published in the journal Nature Nanotechnology.

When a stone is dropped into water, circular waves spread outward from the point of impact. Light behaves similarly: When emitted from a localized source, it naturally propagates as spherical or circular wavefronts within a material. While this isotropic propagation is a fundamental property of waves, it is often undesirable in photonic applications where light must be guided efficiently along predefined paths.

Conventional optical technologies overcome this challenge using waveguides. In optical fiber communications, for example, glass fibers confine laser light and transport it over long distances with minimal loss. Similarly, photonic integrated circuits rely on nanoscale waveguides fabricated through complex lithographic processes, including resist coating, lithography and etching. These fabrication steps are technologically demanding and contribute significantly to manufacturing costs.

Scientists Discover What Makes Hydrogen Go Quantum

The symmetry of vanadium’s crystal structure acts as a switch for hydrogen’s quantum behavior.

Inside a vanadium crystal, hydrogen can travel in two very different ways. It may move as a conventional particle that needs enough energy to jump between locations, or behave like a quantum wave that passes through barriers. Researchers have now identified the structural change that determines which route it takes.

The finding could matter as demand grows for materials that can safely store and transport hydrogen as a source of cleaner energy. Vanadium is a promising candidate because it absorbs hydrogen readily and allows the atoms to move through its crystal lattice, although the reason for their changing behavior had remained uncertain.

Scientists Discover Extreme Acceleration Inside a Nuclear Fireball

Simulations reveal some of the strongest accelerations ever produced on Earth, opening new avenues for QCD research.

When atomic nuclei smash together at almost the speed of light, their internal matter briefly transforms into quark–gluon plasma, an extremely hot fluid in which quarks and gluons move freely.

Scientists have closely examined the plasma’s intense rotation and electromagnetic fields, but the acceleration driving its rapid expansion has received far less attention. In hydrodynamics, however, acceleration is as fundamental as vorticity, just as electric and magnetic fields are paired in electromagnetism.

Giant Plasma Waves May Be Stripping Away Mars’ Atmosphere

Kelvin–Helmholtz waves may help the solar wind strip atmospheric particles from Mars.

Mars is continually exposed to a stream of charged particles racing outward from the Sun. Earth’s global magnetic field deflects much of this solar wind, but Mars lacks a comparable shield. The flow can therefore strike the planet’s upper atmosphere directly and gradually carry some of its particles into space.

Researchers led by Boston University have identified one way this atmospheric loss may occur. Their study, published in Science Advances, found that the solar wind can disturb the outer edge of the Martian atmosphere much as wind agitates the surface of water. The interaction produces large rolling structures called Kelvin–Helmholtz waves, which can help pull atmospheric material away from the planet.

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