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Cooling 100 million degree plasma with a hydrogen-neon mixture ice pellet

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Plasmoid behavior of pure hydrogen and hydrogen mixed with 5 % neon. In this experiment, a new Thomson Scattering (TS) diagnostic system operating at (an unprecedented rate of) 20 kHz was used to (i) measure the density of the plasmoid at the moment it passed through the observation region, and (ii) identify its position, which verified the theoretical predictions. Credit: National Institute for Fusion Science

At ITER—the world’s largest experimental fusion reactor, currently under construction in France through international cooperation—the abrupt termination of magnetic confinement of a high temperature plasma through a so-called “disruption” poses a major open issue. As a countermeasure, disruption mitigation techniques, which allow to forcibly cool the plasma when signs of plasma instabilities are detected, are a subject of intensive research worldwide.

Now, a team of Japanese researchers from National Institutes for Quantum Science and Technology (QST) and National Institute for Fusion Science (NIFS) of National Institute of National Sciences (NINS) found that by adding approximately 5% neon to a ice pellet, it is possible to cool the plasma more deeply below its surface and hence more effectively than when pure hydrogen ice pellets are injected.

Using and experimental measurements with advanced diagnostics at Large Helical Device owned by NIFS, the researchers clarified the dynamics of the dense plasmoid that forms around the ice pellet and identified the physical mechanisms responsible for the successful enhancement of the performance of the forced cooling system, which is indispensable for carrying out the experiments at ITER. These results will contribute to the establishment of plasma control technologies for future fusion reactors. The team’s report was made available online in Physical Review Letters.

The construction of the world’s largest experimental fusion reactor, ITER, is underway in France through international cooperation. At ITER, experiments will be conducted to generate 500 MW fusion energy by maintaining the “burning state” of the hydrogen isotope plasma at more than 100 million degrees. One of the major obstacles to the success of those experiments is a phenomenon called “disruption” during which the magnetic field configuration used to confine the plasma collapses due to magnetohydrodynamic instabilities.

Disruption causes the high-temperature plasma to flow into the inner surface of the containing vessel, resulting in structural damage that, in turn, may cause delays in the experimental schedule and higher cost. Although the machine and the operating conditions of ITER have been carefully designed to avoid disruption, uncertainties remain and for a number of experiments so that a dedicated machine protection strategy is required as a safeguard.

A promising solution to this problem is a technique called “disruption mitigation,” which forcibly cools the plasma at the stage where first signs of instabilities that may cause a disruption are detected, thereby preventing damage to plasma-facing material components. As a baseline strategy, researchers are developing a method using ice pellets of hydrogen frozen at temperatures below 10 Kelvin and injecting it into a high-temperature plasma.

The injected ice melts from the surface and evaporates and ionizes owing to heating by the ambient high-temperature plasma, forming a layer of low-temperature, high-density plasma (hereafter referred to as a “plasmoid”) around the ice. Such a low-temperature, high-density plasmoid mixes with the main plasma, whose temperature is reduced in the process. However, in recent experiments, it has become clear that when pure hydrogen ice is used, the plasmoid is ejected before it can mix with the target plasma, making it ineffective for cooling the high-temperature plasma deeper below the surface.

This ejection was attributed to the high pressure of the plasmoid. Qualitatively, a plasma confined in a donut-shaped magnetic field tends to expand outward in proportion to the pressure. Plasmoids, which are formed by the melting and the ionization of hydrogen ice, are cold but very dense. Because temperature equilibration is much faster than density equilibration, the plasmoid pressure rises above that of the hot target plasma. The consequence is that the plasmoid becomes polarized and experiences drift motion across the magnetic field, so that it propagates outward before being able to fully mix with the hot target plasma.

A solution to this problem was proposed from : model calculations predicted that by mixing a small amount of neon into hydrogen, the pressure of the plasmoid could be reduced. Neon freezes at a temperature of approximately 20 Kelvin and produces strong line radiation in the plasmoid. Therefore, if the neon is mixed with hydrogen ice before injection, part of the heating energy can be emitted as photon energy.

To demonstrate such a beneficial effect of using a hydrogen-neon mixture, a series of experiments was conducted in the Large Helical Device (LHD) located in Toki, Japan. For many years, the LHD has operated a device called the “solid hydrogen pellet injector” with high reliability, which injects ice pellets with a diameter of approximately 3 mm at the speed of 1100 m/s. Due to the system’s high reliability, it is possible to inject hydrogen ice into the plasma with a temporal precision of 1 ms, which allows measurement of the plasma temperature and density just after the injected ice melts.

Recently, the world’s highest time resolution for Thomson Scattering (TS) of 20 kHz was achieved in the LHD system using new laser technology. Using this system, the research team has captured the evolution of plasmoids. They found that, as predicted by theoretical calculations, plasmoid ejection was suppressed when hydrogen ice was doped with approximately 5 % neon, in stark contrast to the case where pure hydrogen ice was injected. In addition, the experiments confirmed that the neon plays a useful role in the effective cooling of the plasma.

The results of this study show for the first time that the injection of hydrogen ice pellets doped with a small amount of neon into a high-temperature plasma is useful to effectively cool the deep core region of the by suppressing plasmoid ejection. This effect of neon doping is not only interesting as a new experimental phenomenon, but also supports the development of the baseline strategy of disruption mitigation in ITER. The design review of the ITER disruption mitigation system is scheduled for 2023, and the present results will help improve the performance of the system.

More information:
A. Matsuyama et al, Enhanced Material Assimilation in a Toroidal Plasma Using Mixed H2+Ne Pellet Injection and Implications to ITER, Physical Review Letters (2022). DOI: 10.1103/PhysRevLett.129.255001

Citation:
Cooling 100 million degree plasma with a hydrogen-neon mixture ice pellet (2023, January 6)
retrieved 7 January 2023
from https://phys.org/news/2023-01-cooling-million-degree-plasma-hydrogen-neon.html

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Here’s how Helene and other storms dumped a whopping 40 trillion gallons of rain on the South

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More than 40 trillion gallons of rain drenched the Southeast United States in the last week from Hurricane Helene and a run-of-the-mill rainstorm that sloshed in ahead of it — an unheard of amount of water that has stunned experts.

That’s enough to fill the Dallas Cowboys’ stadium 51,000 times, or Lake Tahoe just once. If it was concentrated just on the state of North Carolina that much water would be 3.5 feet deep (more than 1 meter). It’s enough to fill more than 60 million Olympic-size swimming pools.

“That’s an astronomical amount of precipitation,” said Ed Clark, head of the National Oceanic and Atmospheric Administration’s National Water Center in Tuscaloosa, Alabama. “I have not seen something in my 25 years of working at the weather service that is this geographically large of an extent and the sheer volume of water that fell from the sky.”

The flood damage from the rain is apocalyptic, meteorologists said. More than 100 people are dead, according to officials.

Private meteorologist Ryan Maue, a former NOAA chief scientist, calculated the amount of rain, using precipitation measurements made in 2.5-mile-by-2.5 mile grids as measured by satellites and ground observations. He came up with 40 trillion gallons through Sunday for the eastern United States, with 20 trillion gallons of that hitting just Georgia, Tennessee, the Carolinas and Florida from Hurricane Helene.

Clark did the calculations independently and said the 40 trillion gallon figure (151 trillion liters) is about right and, if anything, conservative. Maue said maybe 1 to 2 trillion more gallons of rain had fallen, much if it in Virginia, since his calculations.

Clark, who spends much of his work on issues of shrinking western water supplies, said to put the amount of rain in perspective, it’s more than twice the combined amount of water stored by two key Colorado River basin reservoirs: Lake Powell and Lake Mead.

Several meteorologists said this was a combination of two, maybe three storm systems. Before Helene struck, rain had fallen heavily for days because a low pressure system had “cut off” from the jet stream — which moves weather systems along west to east — and stalled over the Southeast. That funneled plenty of warm water from the Gulf of Mexico. And a storm that fell just short of named status parked along North Carolina’s Atlantic coast, dumping as much as 20 inches of rain, said North Carolina state climatologist Kathie Dello.

Then add Helene, one of the largest storms in the last couple decades and one that held plenty of rain because it was young and moved fast before it hit the Appalachians, said University of Albany hurricane expert Kristen Corbosiero.

“It was not just a perfect storm, but it was a combination of multiple storms that that led to the enormous amount of rain,” Maue said. “That collected at high elevation, we’re talking 3,000 to 6000 feet. And when you drop trillions of gallons on a mountain, that has to go down.”

The fact that these storms hit the mountains made everything worse, and not just because of runoff. The interaction between the mountains and the storm systems wrings more moisture out of the air, Clark, Maue and Corbosiero said.

North Carolina weather officials said their top measurement total was 31.33 inches in the tiny town of Busick. Mount Mitchell also got more than 2 feet of rainfall.

Before 2017’s Hurricane Harvey, “I said to our colleagues, you know, I never thought in my career that we would measure rainfall in feet,” Clark said. “And after Harvey, Florence, the more isolated events in eastern Kentucky, portions of South Dakota. We’re seeing events year in and year out where we are measuring rainfall in feet.”

Storms are getting wetter as the climate change s, said Corbosiero and Dello. A basic law of physics says the air holds nearly 4% more moisture for every degree Fahrenheit warmer (7% for every degree Celsius) and the world has warmed more than 2 degrees (1.2 degrees Celsius) since pre-industrial times.

Corbosiero said meteorologists are vigorously debating how much of Helene is due to worsening climate change and how much is random.

For Dello, the “fingerprints of climate change” were clear.

“We’ve seen tropical storm impacts in western North Carolina. But these storms are wetter and these storms are warmer. And there would have been a time when a tropical storm would have been heading toward North Carolina and would have caused some rain and some damage, but not apocalyptic destruction. ”

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Follow AP’s climate coverage at https://apnews.com/hub/climate

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Follow Seth Borenstein on Twitter at @borenbears

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‘Big Sam’: Paleontologists unearth giant skull of Pachyrhinosaurus in Alberta

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It’s a dinosaur that roamed Alberta’s badlands more than 70 million years ago, sporting a big, bumpy, bony head the size of a baby elephant.

On Wednesday, paleontologists near Grande Prairie pulled its 272-kilogram skull from the ground.

They call it “Big Sam.”

The adult Pachyrhinosaurus is the second plant-eating dinosaur to be unearthed from a dense bonebed belonging to a herd that died together on the edge of a valley that now sits 450 kilometres northwest of Edmonton.

It didn’t die alone.

“We have hundreds of juvenile bones in the bonebed, so we know that there are many babies and some adults among all of the big adults,” Emily Bamforth, a paleontologist with the nearby Philip J. Currie Dinosaur Museum, said in an interview on the way to the dig site.

She described the horned Pachyrhinosaurus as “the smaller, older cousin of the triceratops.”

“This species of dinosaur is endemic to the Grand Prairie area, so it’s found here and nowhere else in the world. They are … kind of about the size of an Indian elephant and a rhino,” she added.

The head alone, she said, is about the size of a baby elephant.

The discovery was a long time coming.

The bonebed was first discovered by a high school teacher out for a walk about 50 years ago. It took the teacher a decade to get anyone from southern Alberta to come to take a look.

“At the time, sort of in the ’70s and ’80s, paleontology in northern Alberta was virtually unknown,” said Bamforth.

When paleontogists eventually got to the site, Bamforth said, they learned “it’s actually one of the densest dinosaur bonebeds in North America.”

“It contains about 100 to 300 bones per square metre,” she said.

Paleontologists have been at the site sporadically ever since, combing through bones belonging to turtles, dinosaurs and lizards. Sixteen years ago, they discovered a large skull of an approximately 30-year-old Pachyrhinosaurus, which is now at the museum.

About a year ago, they found the second adult: Big Sam.

Bamforth said both dinosaurs are believed to have been the elders in the herd.

“Their distinguishing feature is that, instead of having a horn on their nose like a triceratops, they had this big, bony bump called a boss. And they have big, bony bumps over their eyes as well,” she said.

“It makes them look a little strange. It’s the one dinosaur that if you find it, it’s the only possible thing it can be.”

The genders of the two adults are unknown.

Bamforth said the extraction was difficult because Big Sam was intertwined in a cluster of about 300 other bones.

The skull was found upside down, “as if the animal was lying on its back,” but was well preserved, she said.

She said the excavation process involved putting plaster on the skull and wooden planks around if for stability. From there, it was lifted out — very carefully — with a crane, and was to be shipped on a trolley to the museum for study.

“I have extracted skulls in the past. This is probably the biggest one I’ve ever done though,” said Bamforth.

“It’s pretty exciting.”

This report by The Canadian Press was first published Sept. 25, 2024.

The Canadian Press. All rights reserved.

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The ancient jar smashed by a 4-year-old is back on display at an Israeli museum after repair

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TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.

Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.

Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.

The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.

The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.

It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.

Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.

Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.

Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.

Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.

Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.

The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”

The Canadian Press. All rights reserved.

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