By Becky Phillips
Video - "Antimatter - harnessing the power of positrons"
"This morning, NASA successfully launched the world’s first gamma ray shuttle to the galactic center of the Milky Way. Once there, geo-astronauts say they can mine and harvest enough raw antimatter to power Earth’s energy needs for the next decade. Unfortunately, they won’t be back for centuries..."
Although we won’t see that story on tonight’s six o’ clock news, Kelvin Lynn
is serious when he says it is possible to harness the power of antimatter – and that it may be conceivable to collect that antimatter from a mother-lode hiding out near the center of our galaxy.
Marc Weber and Kelvin Lynn (l-r)
Lynn - professor in the departments of Physics and Mechanical & Materials Engineering and director of the Center for Materials Research - and Marc Weber
, staff scientist in the Department of Physics, have developed an unprecedented concept that could offer the world its first practical method for containing and transporting a type of antimatter particle called the positron.
If successful, their theory could lead to large-scale production of antimatter fuel capable of powering deep space travel – as well as a host of other, more earthbound, applications.
"It’s the most efficient energy source that we know of. It’s 100 percent efficient - with no radioactive residue," said Lynn.
As two of the foremost positron researchers in the world, Lynn and Weber have the capacity to produce more positrons at WSU than any other facility in the nation. With a deuteron accelerator in the W.M. Keck Antimatter Laboratory, they can create positron beams that generate up to 120 billion positrons per second – or up to 10 trillion usable positrons per day.
They said it could never be done
Because of their expertise in the field, the pair was challenged by the U.S. Air Force several years ago to come up with a way to trap these positrons – specifically by storing them in plasma. (Plasma is a unique type of matter composed of ionized gas.)
Despite their best efforts, however, they were unable to overcome the repulsive forces present when a billion or so positrons are forced together into a plasma "trap." Since particles of like charge repel each other, the energy required to hold the positrons together quickly exceeds the energy that would be gained through their "annihilation" – the explosion that occurs when an antimatter positron meets its matter opposite - the electron – and releases gamma rays.
Until now, no one had discovered a way to circumvent the repulsion problem – and the general consensus was that it was impossible. When even Lynn could not figure out a way to make it work, he literally went outside the box and turned to tubes.
It had occurred to him, one restless night, that rather than trying to contain positrons in an enclosed space, they could instead be lined up side-by-side in an infinitely long and narrow vacuum tube. From there, he realized, the tube could be cut up into tiny straws - each containing just one positron.
With several million dollars in federal funding approved for this project, Lynn and Weber have already designed a prototype trap – about the size of a Coke can – that can hold an array of 10,000 tubes each with a diameter of 100 micrometers and 0.1 meter length. Their goal is to store up to one trillion positrons for 10 days.
The key is in the coating
The key factor behind the success of the trap is a mirror-like, metallic coating on the walls of each tube. The repulsive forces of each positron are bounced back by the mirror and can no longer affect any of the other positrons. In effect, many more tubes can be added to the trap with no further energy expenditure.
Also helping hold the positrons in place are magnetic fields, which must be perfectly aligned within each tube. At the end of the trap is a small metal "gate" that could be charged with a 9-volt battery.
"When we want to use the positrons, we could lower the voltage, open the gate and let some of the positrons come out and annihilate to give us energy," said Lynn.
"The Coke can (trap) can store up to one trillion positrons, which would create a tremendous amount of energy," he said. "When matter comes together with antimatter, all that’s left is pure energy."
Indeed, just 0.3 milligrams of antimatter – the size of two grains of sand – packs the same energy potential as about 1, 700 tons of liquid hydrogen-oxygen fuel used to power the space shuttle. With only two milligrams of antimatter and a 10 pound trap, Lynn speculates that astronauts would be able to fly into deep space.
"While the experimental pursuit and prototype test of this idea is technologically challenging, it complies with all known fundamental (laws of) science," Lynn said. "Our concept is based on well established and experimentally proven physics – but we are extending it into previously unexplored territory."
To the galaxy and beyond
And if that concept is confirmed, "it is just a matter of extrapolation," said Lynn.
The trap design could be scaled to a size large enough to power space ships, for example – which would use the gamma rays to propel them along.
"They would slowly push you faster and faster … until you eventually reached the speed of light," he said. "Then, you could actually go mine antimatter near the galactic center and put it in the traps – and from there, you could travel anywhere you’d want to. You wouldn’t have to make it anymore."
Just recently, Lynn explained, astronomers have detected massive amounts of annihilation and gamma rays coming from the center of our Milky Way galaxy – signaling a large cache of antimatter in that location. He said that ever since the inception of the big bang theory, physicists have wondered about an apparent lack of antimatter in our universe. It now seems that at least some of it is being hoarded near the galactic center.
On a more terrestrial level, Weber said that "most people can probably relate to antimatter in terms of positron emission tomography. The PET scan is a medical device that uses positron-emitting isotopes to diagnose biomedical conditions such as Alzheimer’s disease and very early stages of cancer."
|Worldwide, one of the biggest threats to human health is a lack of available clean water. Lynn is using positrons to help improve nanofiltration technology that may make water treatment systems much more effective.
In addition, positrons also are used for studying biological, chemical and environmental systems – as well as for measuring atomic interactions, global warming and dark matter. In the world of materials research, positrons help identify defects in semi-conductors, insulators and metals.
"Right now, they have to bring the semi-conductors to us because we have the positron beams," said Lynn. "But if we had these little traps, we could take them other places. We could have portable positrons."
Like lasers and transistors - both of which had their skeptics when first invented - Lynn said harnessing positrons could open up a "universe" of unexplored ideas and uses.
"It could happen in your lifetime," he said.
The concept of an "antimatter" world first arose in 1928 when the fields of quantum mechanics and relativity theory were just emerging. In 1933, American physicist, Carl Anderson confirmed that reality when he identified the first-known antiparticle, the positron, from cosmic rays – and was awarded the Nobel Prize.
(photo: curved line on left gave first proof of an
antiparticle. Courtesy Kelvin Lynn.)
Simply speaking, antimatter is the exact opposite of matter. For every electron, proton or neutron in an atom, there exists a particle of opposite charge. Right now, there actually could be an anti-you sitting in front of an anti-computer in an anti-universe somewhere. But if you happened to meet yourself and shake hands – Boom! When matter and anti-matter meet, they annihilate each other – leaving nothing but energy behind.
"We can create antimatter very easily in the matter world," said professor Kelvin Lynn. "It just doesn’t live very long because it eventually finds (its opposite) an electron … and annihilates. However, if you put it in a vacuum, it will live forever."
Lynn and staff scientist Marc Weber are world-renowned for their ability to create positrons. Using a 3 million volt deuteron accelerator in the Keck Antimatter Laboratory, they shoot beams of particles at carbon atoms with such force that they are pounded into unstable nitrogen atoms that further decay, releasing positrons in the process. A similar reaction takes place in the PET scan with positron emission tomography.
In order to harness the energy of positrons, Weber listed three problems that must be overcome.
"We need to be able to generate many positrons; we need a vacuum container to store them in; and then we must convert their annihilation power into something that drives an engine or turns on the lights. Right now we are focusing on the storage problem."
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