An illustration of anti-hydrogen containment
Physicists at the ALPHA facility at CERN report that they have managed to contain antimatter for several minutes, a huge improvement over their previous attempt at antimatter containment last year, which lasted only two tenths of a second.
Antimatter is comprised of particles that have the same mass as “normal” particles, like protons or electrons, but have opposite charge: for example, anti-protons have negative charge, while anti-electrons (aka positrons) have positive charge. The antimatter in the ALPHA experiment is in the form of neutral anti-hydrogen — an anti-proton and a positron — created in a high energy state. Anti-hydrogen is the antimatter counterpart to hydrogen, the simplest and by far the most abundant element in the universe.
Physicists at particle accelerates have been able to produce positrons and anti-protons for a long time. Getting them to stick together to form a neutral anti-hydrogen atom and keep it contained has been the real trick. The ALPHA physicists used electric fields to clear out stray charged particles, and used superconducting magnets to hold the remaining anti-hydrogen particles in place. The purpose for containing antimatter for a long periods of time is to allow study of its properties and see how it differs from normal matter. Why is this important? Out of laziness, I’ll just quote myself from a previous article:
… big bang theory requires that equal amounts of matter and antimatter existed in the very early history of the universe. The matter and antimatter would collide and annihilate, producing a burst of energy. The great mystery is why our galaxy and everything we observe appears to be made of matter. Actually, the great mystery is why there is any matter at all, for if there was an equal amount of antimatter, all of it should have been annihilated. Some theories propose a tiny asymmetry, with slightly more matter than antimatter, but these theories raise problems of their own.
What physicists hope to understand is why matter came to dominate the universe instead of antimatter (or no matter at all). Some sort of asymmetry has to exist, and studying anti-hydrogen may reveal what that is.
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SixDay Science 
Wait, I thought antimatter was as powerful as a nuclear bomb! They are playing with forces they don’t understand! At least, that’s what pop culture has taught me, and therefore, it’s fact.
More seriously though, what happens when the antimatter is no longer contained?
What happens is that the antimatter goes zipping off and immediately annihilates with the first bit of matter it encounters. Depending on what type of antimatter particles they are, the annihilation produces different stuff. Electron-positron annihilation produces gamma rays, while proton-anti-proton annihilation produces gamma rays and other particles, such as pions (carriers of the strong nuclear force).
The energy of the gamma rays and particles can, in principle, be harnessed to do mechanical work. For instance, check out this groovy NASA article about antimatter propulsion. The main limitations are the difficulties containing antimatter and the cost to produce antimatter — the article, which is dated 1999, claims that antimatter costs $62.5 trillion a gram. [Insert government-spending joke here]. That’s probably come down a bit, but still. Expensive.
Thanks!
From the article: “Our goal is to remove antimatter from the far-out realm of science fiction into the commercially exploitable realm for transportation and medical applications.”
It’s been twelve years, but this now looks like a promising step forward toward that goal!