By Becky Phillips, Washington State University
"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 three or four 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.
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.