Human World

Antimatter created and trapped for the first time

Antimatter has been created and contained for the first time by scientists at the European nuclear research organization CERN, according to a November 2010 report. We spoke with lead researcher Jeffrey Hangst of the University of Aarhus in Denmark.

Jeffrey Hangst: What we’ve done here for the first time is to hold onto some anti-hydrogen atoms. Anti-hydrogen is the antimatter equivalent of the most basic element, hydrogen. And we’ve been producing anti-hydrogen at CERN since about 2002. What we’ve done here is to not just produce it, but to produce it in a trap, as we call it. It’s kind of a magnetic bottle that can hold on to the anti-hydrogen so that it doesn’t fly off and meet a cataclysmic fate by annihilating with normal matter.

Professor Hangst described antimatter as a mirror image of the regular matter that makes up the universe as we know it.

Jeffrey Hangst: Now, matter and anti-matter aren’t compatible. If they meet, you get annihilation.

Hangst said that in this experiment, antimatter atoms were trapped the atoms for 1/10th of a second, and then intentionally released to see them annihilate. But these antimatter experiments, said Hangst, pose no danger.

Jeffrey Hangst: But there’s no real danger in what we do. We’re not unleashing some unknown energy source or something like that. That’s purely science fiction. What we’re really trying to do is ask fundamental questions. And the question in our experiment is, do matter and anti-matter obey the same laws of physics. It’s really very simple.

Hangst explained more about the results of his experiment that trapped 38 atoms of antihydrogen for 1/10 of a second.

Jeffrey Hangst: There’s nothing magical about those two numbers. This is a proof of principle experiment. So we published this as soon as we can demonstrate that this actually works. We can already trap many more and for much longer time. So the 172 milliseconds was chosen by us, it was kind of the fastest time that we could do the experiment and then release the anti-hydrogen to see that it was there. The way that you do this experiment is to trap the atoms and then intentionally release them so that you can see them annihilate. That’s how you know that they were there. We’re already doing much longer storage times and we’re improving the rate regularly.

One of the big mysteries about antimatter, said Hangst, is why there’s so little of it apparent to humans. The equations of physics predict there should be as much antimatter as regular matter in the universe.

Jeffrey Hangst: People have spent a long time looking for some evidence of anti-matter in distant galaxies. When matter and anti-matter annihilate, the signature that they leave is well-defined. So you can go looking for that. And so far, no one has found any evidence of anti-matter anywhere else in their telescopes or in any experiment they’ve done. So as far as we know, the universe is made entirely of matter. There’s no evidence that there are significant quantities of anti-matter anywhere. That’s why this is such a big mystery. We don’t know why that is.

Professor Hangst described how antimatter was made and trapped.

Jeffrey Hangst: The reason we’re at CERN is that we need a machine that can produce anti-protons. Those are the nuclei of the anti-hydrogen atom. It’s just the opposite of a proton. A proton has a positive charge, and an anti-proton has a negative charge. And these things are quite common in Physics laboratories, in Fermilab, for example, in Chicago, and at CERN. So we’ve been working with anti-protons for many, many years. But you need an accelerator to produce them. CERN has a very special machine that produces anti-protons for us, and then slows them down. It’s kind of an accelerator in reverse. It’s called the anti-proton decelerator. It can produce some number of anti-protons for us, which we then trap. We make an electromagnetic bottle that can hold on to the anti-protons. The other ingredient is positrons. Those are anti-electrons. And positrons are much more common. You can go to a hospital and have what’s called a PET scan, Positron Emission Tomography, where they actually inject a positron emitter into your body and watch what happens. You can buy positrons, if you have the ‘mad scientists license.’ We get them from a radioactive source. It’s called Sodium-22 source. Then we have a device that sits and accumulates positrons from this radioactive source. What our experiment does then is to mix anti-protons and positrons at very low temperatures, just a few degrees above absolute zero, to make anti-hydrogen atoms.

Professor Hangst explain how his team uses a ‘magnetic bottle.’

Jeffrey Hangst: The way you can think about this is that, although the anti-hydrogen atom is neutral, it has a slight magnetic character. You can think of it as a microscopic compass needle, so it can be deflected by very strong magnetic fields. So what we do is surround the formation of the region with a kind of a magnetic bottle. And when the anti-hydrogen atom is born, if it’s not moving too quickly, it gets trapped in this magnetic bottle. And this is the first experiment to demonstrate that this is possible. Just to give you an idea of how difficult that is, in temperature units, these anti-atoms have to have less than 0.5 degrees above absolute zero, otherwise they just fly out of this magnetic bottle. And that’s what’s made this so difficult and why it’s such a breakthrough.

There are no practical uses for anti-matter, said Hangst.

Jeffrey Hangst: This is pure science fiction to think of anti-matter as a fuel, or as a weapon. It would take us longer than the age of the universe just to produce one gram of anti-hydrogen. You use much, much more energy to produce it then you could ever get out of it. And that’s of course a losing proposition for an energy source. So this is really pure research at the most basic level. We’re really asking fundamental questions, and we’re not worried in any way about future applications of what we might do. Thirty-eight atoms aren’t a danger to anybody.

Hangst told EarthSky what he feels is the most important thing to share with people today about antimatter.

Jeffrey Hangst: This is a fascinating substance that for some reason, nature chose not to give us. And that should inspire people’s curiosity and get them to look harder, ask questions about why this is and why is the universe the way it is. That’s the kind of thing that inspires us to go looking.

December 13, 2010
Human World

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