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It will be
used to learn more about the sun and nuclear fusion, according to scientists.
Capturing
lightning in a bottle is a difficult challenge, but physicists have now
discovered a way to store ultra-cold plasma in a magnetic bottle trap, a
discovery that could help physicists understand solar winds and achieve nuclear
fusion.
Plasma is
made up of positive ions and negative free electrons and is one of the four
states of matter. However, unlike solids, liquids, and gases, it only appears
in the most extreme places, such as a flash of ionized air known as a lightning
bolt, the dancing pattern of the aurora borealis, or the sun's surface, making it
highly difficult to observe.
The fact
that plasmas in the Northern Lights or on the surface of the sun deal with a
complex magnetic field in ways that scientists don't fully comprehend only adds
to the difficulty.
The
(strong) magnetic field has the effect of altering anything relative to what
you'd expect without a magnetic field in the sun's atmosphere, but in very
subtle and complicated ways that can really trip you up if you don't have a very
clear understanding of it, study co-author Peter Bradshaw said in a statement.
Colder
particles travel more slowly, allowing for more accurate conduct measurements.
The scientists used a method called laser-cooling to cool their strontium
plasma down to around 1 degree above absolute zero (around minus 272 degrees
Celsius) in order to find out how plasmas deal with magnetic fields.
You'd
assume that shooting a laser at something will heat it up, but if the photons
(light particles) in the laser beam move in the opposite direction of the
moving plasma particles, they can actually slow them down and cool them down.
After
cooling the plasma, the researchers used forces from nearby magnets to
temporarily trap it, allowing them to observe it until it dissipated. They then
set out to unravel the relationship between the plasma's ions and electrons and
the magnetic field, which varies greatly around the plasma. It took them a year
to completely interpret their data due to the complexity of the interaction.
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We test
plasma properties by scattering light off the ions in the plasma, but the
magnetic field makes this extremely difficult, according to Rice Dean of
Natural Sciences Tom Killian. Since the magnetic field alters how the ions
disperse the laser light in unexpected ways, this is the case.
Furthermore,
the magnetic field varies in space around the plasma, according to Killian. To
paint a picture of the plasma density and speed through the bottle over time,
we had to figure out all of those results.
The image
they released showed fast-moving, low-mass electrons pinned to magnetic field
lines and spiraling around them, with positive ions trapped within the trap due
to their attraction to the negatively charged electrons. The writers of the
paper theorize that the magnetic field prevented the electrons and ions from
joining to form neutral atoms, keeping the soup in a plasma state.
The
trapping method opens up a slew of new possibilities for plasma science.
Physicists may study the behavior of plasma-composed stellar objects like white
dwarfs or begin to mimic the conditions for fusion within the sun if they can
trap ultra-cold plasma in a container.
The
researchers will then create a laser grid to plug any holes in the magnetic
field of the bottle that might allow ions to escape the experiment. They also
want to learn more about the processes that take place within the trapped
plasma, including how ions and electrons recombine and how energy and mass pass
through the system.
According
to Killian, our new abilities can provide a great opportunity to research
certain phenomena. Similar effects are likely significant for understanding
some other difficult-to-experiment structures, such as white dwarf stars.
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