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Category: particle physics – Page 281

The space between the planets in our solar system is filled with a wispy sea of charged particles that flow out from the Sun’s atmosphere. This particle population is augmented by cosmic rays — speedy protons and atomic nuclei accelerated in extreme environments across the universe — which ebb and flow against the 11-year solar activity cycle. This undulating particle background is punctuated by bursts of high-energy particles from the Sun, which can be unleashed suddenly in violent solar storms.

Spacecraft that venture out from the protection of Earth’s magnetic field must navigate this ocean of particles and weather solar storms. And if we someday wish to send astronauts to other planets, we’ll need to know how high-energy solar particles, which pose a risk to the health of astronauts and electronic systems alike, travel through the solar system.

In a new publication, a team led by Shuai Fu (Macau University of Science and Technology), Zheyi Ding (China University of Geosciences), and Yongjie Zhang (Chinese Academy of Sciences) studied the high-energy solar particles produced in an event in November 2020, when the Sun emitted a solar flare and a massive explosion of solar plasma called a coronal mass ejection.

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For decades, if you asked a fusion scientist to picture a fusion reactor, they’d probably tell you about a tokamak. It’s a chamber about the size of a large room, shaped like a hollow doughnut. Physicists fill its insides with a not-so-tasty jam of superheated plasma. Then they surround it with magnets in the hopes of crushing atoms together to create energy, just as the sun does.

But experts think you can make tokamaks in other shapes. Some believe that making tokamaks smaller and leaner could make them better at handling plasma. If the fusion scientists proposing it are right, then it could be a long-awaited upgrade for nuclear energy. Thanks to recent research and a newly proposed reactor project, the field is seriously thinking about generating electricity with a “spherical tokamak.”

“The indication from experiments up to now is that [spherical tokamaks] may, pound for pound, confine plasmas better and therefore make better fusion reactors,” says Steven Cowley, director of Princeton Plasma Physics Laboratory.

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After decades of inertial confinement fusion research, a yield of more than 1.3 megajoules (MJ) was achieved at Lawrence Livermore National Laboratory’s (LLNL’s) National Ignition Facility (NIF) for the first time on Aug. 8, 2021, putting researchers at the threshold of fusion gain and achieving scientific ignition.

On the one-year anniversary of this historic achievement, the scientific results of this record experiment have been published in three peer-reviewed papers: one in Physical Review Letters and two in Physical Review E. More than 1,000 authors are included in one of the Physical Review Letters paper to recognize and acknowledge the many individuals who have worked over many decades to enable this significant advance.

“The record shot was a major scientific advance in research, which establishes that fusion ignition in the lab is possible at NIF,” said Omar Hurricane, chief scientist for LLNL’s inertial confinement fusion program. “Achieving the conditions needed for ignition has been a long-standing goal for all inertial confinement fusion research and opens access to a new experimental regime where alpha-particle self-heating outstrips all the cooling mechanisms in the fusion plasma.”

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Thomas Jefferson National Laboratory experiments hone in on a never-before-measured region of strong force coupling, a quantity that supports theories accounting for 99% of the ordinary mass in the universe.

Much fanfare was made about the Higgs boson when this elusive particle was discovered in 2012. Although it was touted as giving ordinary matter mass, interactions with the Higgs field only generate about 1% of ordinary mass. The other 99% comes from phenomena associated with the strong nuclear force, the fundamental force that binds smaller particles called quarks into larger particles called protons and neutrons that comprise the nucleus of the atoms of ordinary matter.

The Strong Nuclear Force (often referred to as the strong force) is one of the four basic forces in nature. The others are gravity, the electromagnetic force, and the weak nuclear force. As its name implies, it is the strongest of the four. However, it also has the shortest range, which means that particles must be extremely close before its effects are felt.

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But the dark matter hypothesis isn’t perfect. Computer simulations of the growth of galaxies suggest that dark-matter-dominated galaxies should have incredibly high densities in their centers. Observations of real galaxies do show higher densities in their cores, but not nearly enough as those simulations predicted. Also, simulations of dark matter evolving in the universe predict that every galaxy should have hundreds of smaller satellites, while observations consistently come up short.

Given that the dark matter hypothesis isn’t perfect — and that we have no direct evidence for the existence of any candidate particles — it’s worth exploring other options.

One such option was introduced back in the 1970s alongside the original dark matter idea, when astronomer Vera Rubin first discovered the problem of stars moving too quickly inside galaxies. But instead of adding a new ingredient to the universe, the alternative changes the recipe by altering how gravity works at galactic scales. The original idea is called MOND, for “modified Newtonian dynamics,” but the name also applies to the general family of theories descended from that original concept.

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“Pamela” is an uncrewed surface vehicle (USV) developed as an entrepreneurial idea at the Norwegian University of Science and Technology (NTNU) for sampling a variety of surface water particles, from microplastic to plankton to salmon lice. The USV is a joint effort by an interdisciplinary team—Andrea Faltynkova, a Ph.D. candidate at the Department of Biology, and Artur Zolich, a postdoc at the Department of Engineering Cybernetics.

Faltynkova studies microplastics in the ocean. Microplastics are bits of plastic smaller than 5 mm, which is roughly the size of the end of a pencil. While researchers know that microplastics can have negative effects on marine or freshwater organisms, there’s less known about how they affect human health. But studying microplastics is a challenge because of the nature of the substance itself, she says.

“Microplastics are so heterogeneous. It’s a very large, diverse group of particles. Not only that but they are very unevenly distributed. Microplastic is not like other dissolved pollutants that can be detected even in small quantities of water or soil. If you go and you take a liter from the sea, and there’s no plastic in it, can you conclude that there is no plastic in the sea?” she asked.

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In the two decades since short-baseline neutrino anomalies were first discovered, scientists have come up with several guesses about what might cause discrepancies.

Of all the known elementary particles, neutrinos probably give physicists the most headaches.

These tiny fundamental bits of matter are the second most common particle in the universe yet are anything but ordinary. Since their discovery, they have taunted scientists with bizarre behaviors, some of which physicists have yet to comprehend.

One source of confusion has showed up in the results from short-distance neutrino experiments, in which neutrinos are measured after traveling somewhere between a few meters and a kilometer. When scientists measure neutrinos in these experiments, the results don’t always match their predictions. Sometimes there are too many of certain types of neutrinos, while in others there are too few.

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