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Category: particle physics – Page 142

Launching rockets into space with atomic bombs is a crazy idea that was thankfully discarded many decades ago. But as Richard Corfield discovers, the potential of using the energy from nuclear-powered engines to drive space travel is back on NASA’s agenda.

In 1914 H G Wells published The World Set Free, a novel based on the notion that radium might one day power spaceships. Wells, who was familiar with the work of physicists such as Ernest Rutherford, knew that radium could produce heat and envisaged it being used to turn a turbine. The book might have been a work of fiction, but The World Set Free correctly foresaw the potential of what one might call “atomic spaceships”

The idea of using nuclear energy for space travel took hold in the 1950s when the public – having witnessed the horrors of Hiroshima and Nagasaki – gradually became convinced of the utility of nuclear power for peaceful purposes. Thanks to programmes such as America’s Atoms for Peace, people began to see that nuclear power could be used for energy and transport. But perhaps the most radical application lay in spaceflight.

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Tokamak fusion plasmas benefit from high pressures but are then susceptible to modes of instability. These magnetohydrodynamic (MHD) modes are macroscopic distortions of the plasma, but certain collective motions of individual particles can provide stabilizing effects opposing them. The presence of a resistive wall slows the mode growth, converting a kink to a resistive wall mode (RWM). A kinetic MHD model includes Maxwell’s equations, ideal MHD constraints, and kinetic effects included through the pressure tensor, calculated with the perturbed drift-kinetic distribution function of the particles. The kinetic stabilizing effects on the RWM arise through resonances between the plasma rotation and particle drift motions: precession, bounce, and transit. A match between particle motions and the mode allows efficient transfer of energy that would otherwise drive the growth of the mode, thus damping the growth. The first approach to calculating RWM stability is to write a set of equations for the complex mode frequency in terms of known quantities and then to solve the system. The “energy principle” approach, which has the advantage of clarity in distinguishing the various stabilizing and destabilizing effects, is to change the force balance equation into an equation in terms of changes of kinetic and potential energies, and then to write a dispersion relation for the mode frequency in terms of those quantities. These methods have been used in various benchmarked codes to calculate kinetic effects on RWM stability. The theory has illuminated the important roles of plasma rotation, energetic particles, and collisions in RWM stability.

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The neutron lifetime anomaly has been used to motivate the introduction of new physics with hidden-sector particles coupled to baryon number, and on which neutron stars provide powerful constraints. Although the neutron lifetime anomaly may eventually prove to be of mundane origin, we use it as motivation for a broader review of the ways that baryon number violation, be it real or apparent, and dark sectors can intertwine and how neutron star observables, both present and future, can constrain them.

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NASA’s Parker Solar Probe is crashing through a hailstorm of dust as it hurtles towards the sun at awe-inspiring speed.

The probe’s team members found that high-speed impacts with dust particles are not only more common than expected, they’re making tiny plumes of superhot plasma on the surface of the craft, according to an announcement for a new study.

The probe’s main mission goals are to measure the electric and magnetic fields near the sun and learn more about the solar wind—the stream of particles coming off of the sun, says David Malaspina, a space plasma physicist at the University of Colorado Boulder Astrophysical and Planetary Sciences Department and Laboratory for Atmospheric and Space Physics. Malaspina led the study, which the team will present at a conference this week.

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A team from TU Dortmund University recently succeeded in producing a highly durable time crystal that lived millions of times longer than could be shown in previous experiments. By doing so, they have corroborated an extremely interesting phenomenon that Nobel Prize laureate Frank Wilczek postulated around ten years ago and which had already found its way into science fiction movies.

The results have been published in Nature Physics.

Crystals or, to be more precise, in space, are periodic arrangements of atoms over large length scales. This arrangement gives crystals their fascinating appearance, with smooth facets like in gemstones.

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In research that could jumpstart work toward the quantum internet, researchers at MIT and the University of Cambridge have built and tested an exquisitely small device that could allow the quick, efficient flow of quantum information over large distances.

Key to the device is a “microchiplet” made of diamond in which some of the diamond’s carbon atoms are replaced with atoms of tin. The team’s experiments indicate that the device, consisting of waveguides for the light to carry the , solves a paradox that has stymied the arrival of large, scalable quantum networks.

Quantum information in the form of quantum bits, or qubits, is easily disrupted by environmental noise, like magnetic fields, that destroys the information. So on one hand, it’s desirable to have qubits that don’t interact strongly with the environment. On the other hand, however, those qubits need to strongly interact with the light, or photons, key to carrying the information over distances.

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