Reaching for the Stars - Antimatter Explored

While that's been done easily enough in small quantities, fueling a rocket will take much more.

"We're building a Penning trap," Smith said, "one that will be lightweight and robust." When completed, it will weigh about 100 kg (220 lbs), much of it liquid nitrogen and helium to keep about a trillion antiprotons - far less than a nanogram - quiescent in a zone about 1 mm (1/25th inch) across.

"How do you know that you have particles in the trap?" Smith asked. "They're odourless and colourless." However, they do have distinctive radio frequency signatures which Smith and his colleagues have been able to measure. They've also demonstrated that their trap design would hold a significant quantity for up to 5 days.

"Our aim is to get up to a microgram of antiprotons," Smith said. "There are some interesting propulsion technologies that work at that level. We think we can do it."

A trillion antiprotons is the maximum that can be stored under those conditions. More could be held if they were turned into anti-hydrogen, antiprotons plus positrons.

A lot of bang for the buck

Right now, antimatter is the most expensive substance on Earth, about $62.5 trillion a gram ($1.75 quadrillion an ounce). The production is, at best, 50 percent efficient because half of what's created are regular protons, and the equipment now used was not designed to fuel rockets. Harold Gerrish of NASA and others estimate that improvements in equipment to slow and trap the antiprotons could bring the price down to about $5,000 per microgram. A new injector at Fermilab outside Chicago will allow that facility to increase its production tenfold, from 1.5 to 15 nanograms a year.

Lab. for Energetic Particle Science A schematic of the heart of a Penning trap where a cloud of antiprotons (the fuzzy bluish spot) is kept cold and quiet by liquid nitrogen and helium and a stable magnetic field.

"Right now, a lot of antiprotons are produced, but most are wasted," Gerrish said.

CERN has now produced anti-hydrogen as part of the Athena fundamental physics program to determine if antimatter indeed is indistinguishable from matter. Using the same Ioffe-Pritchard trap developed at CERN, Dr. Steven Howe of Synergistic Technologies in Los Alamos, N.M, expects that large quantities of anti-hydrogen atoms could be stored safely for long periods. At low temperatures, the wavelength of the atom is several times that of the material making up the container walls, so the atoms are reflected with little effort.