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2010-11-19 08:45:37
Publicerad: 17 november 2010, 19.08. Senast ndrad: 17 november 2010, 22.08
2010-11-17 19:08:15
Varf r best r v r v rld endast av materia?
G tan kan vara p v g mot en l sning med hj lp av en forskare fr n Stockholms universitet som har varit med och f r f rsta g ngen f ngat antimateria vid CERN.
Det k nns fantastiskt, s ger docent Svante Jonsell.
Svante Jonsell och hans kollegor vid den internationella forskargruppen ALPHA har f r f rsta g ngen lyckats f nga atomer av antimateria ett f rsta steg f r att ta reda p varf r universum bara best r av materia.
Vad vi har gjort r att vi lyckats f nga alla fasta atomer av det man kallar antimateria och h lla fast dem i en "atomf lla", s ger Svante Jonsell.
Antimateria r enklast beskrivet spegelbilder till vanliga partiklar men med motsatt elektrisk laddning.
Under Big Bang skapades b de materia och antimateria enligt g ngse teorier i fysiken. Men n r de tv tr ffar p varandra f rintas de de f rg r varandra. Fr gan r d rf r hur den materia vi idag ser i universum blev ver.
Det finns ett problem h r. Skapades det mer materia n antimateria? Eller r spegelbilden inte helt perfekt?
Om n gon liten skillnad kan hittas skulle det kunna f rklara vart all antimateria tagit v gen.
Experimentet utf rs vid det europeiska forskningslaboratoriet CERN utanf r Gen ve eftersom antipartiklarna m ste skapas i partikelacceleratorer.
H r tar man fram den enklaste formen av antiatomer, antiv te.
n s l nge har forskarna lyckats producera 38 atomer som nu h lls fast av starka magnetiska krafter i vakuum. Det g r inte att f rvara dem i en vanlig beh llare eftersom de genast f rg rs n r de kommer i kontakt med materia.
Atomerna f r inte heller r ra sig s mycket. D rf r r hela experimentet nerkylt till nio kelvin med hj lp av flytande helium.
Ett 40-tal personer har arbetat med projektet i tta r. De r v ldigt glada ver att ntligen ha lyckats.
F r oss r det h r fantastiskt. Vi har skapat atomer gjorda av partiklar som inte finns p jorden, s ger Jonsell.
Nu satsar forskarna p att ka antalet atomer s att det g r att unders ka ljuset fr n antiv te. Eventuellt kan man d se om det finns n got liten skillnad j mf rt med vanligt v te. D blir det riktigt sp nnande, s ger Svante Jonsell.
Om n gra r hoppas man ha n gra tusen atomer att jobba med.
Finns det n gra faror med experimentet? Vad h nder om ni tappar antimateria?
Nej, det finns inga faror. Tappar man materian s faller den ner och f rg rs mot v ggarna p experimentet. Vi kan aldrig skapa s mycket antimateria att det blir farligt. ven om vi lyckas riktigt bra och skapar en miljard atomer s kan energin som frig rs inte ens v rma en tekopp mer n en hundradels grad.
S om man stoppar in fingret i experimentet h nder ingenting?
Nej. D r det v rre om man hamnar i v gen f r antiprotonacceleratorn, s ger Svante Jonsell.
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Posted: 2010882@445.48
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stranger
Antimatter atom trapped for first time, say scientists
By Jason Palmer Science and technology reporter, BBC News
Alpha detector (Niels Madsen) Flashes of light were detected as the antimatter "annihilated" with matter
Antimatter atoms have been trapped for the first time, scientists say.
Researchers at Cern, home of the Large Hadron Collider, have held 38 antihydrogen atoms in place, each for a fraction of a second.
Antihydrogen has been produced before but it was instantly destroyed when it encountered normal matter.
The team, reporting in Nature, says the ability to study such antimatter atoms will allow previously impossible tests of fundamental tenets of physics.
The current "standard model" of physics holds that each particle - protons, electrons, neutrons and a zoo of more exotic particles - has its mirror image antiparticle.
The antiparticle of the electron, for example, is the positron, and is used in an imaging technique of growing popularity known as positron emission tomography.
However, one of the great mysteries in physics is why our world is made up overwhelmingly of matter, rather than antimatter; the laws of physics make no distinction between the two and equal amounts should have been created at the Universe's birth.
Slowing anti-atoms
Producing antimatter particles like positrons and antiprotons has become commonplace in the laboratory, but assembling the particles into antimatter atoms is far more tricky.
That was first accomplished by two groups in 2002. But handling the "antihydrogen" - bound atoms made up of an antiproton and a positron - is trickier still because it must not come into contact with anything else.
While trapping of charged normal atoms can be done with electric or magnetic fields, trapping antihydrogen atoms in this "hands-off" way requires a very particular type of field.
"Atoms are neutral - they have no net charge - but they have a little magnetic character," explained Jeff Hangst of Aarhus University in Denmark, one of the collaborators on the Alpha antihydrogen trapping project.
Start Quote
I'm delighted that it worked as we said it should... it shows that the dream from many years ago is not completely crazy
End Quote Professor Gerald Gabrielse Harvard University
"You can think of them as small compass needles, so they can be deflected using magnetic fields. We build a strong 'magnetic bottle' around where we produce the antihydrogen and, if they're not moving too quickly, they are trapped," he told BBC News.
Such sculpted magnetic fields that make up the magnetic bottle are not particularly strong, so the trick was to make antihydrogen atoms that didn't have much energy - that is, they were slow-moving.
The team proved that among their 10 million antiprotons and 700 million positrons, 38 stable atoms of antihydrogen were formed, lasting about two tenths of a second each.
Early days
Next, the task is to produce more of the atoms, lasting longer in the trap, in order to study them more closely.
"What we'd like to do is see if there's some difference that we don't understand yet between matter and antimatter," Professor Hangst said.
"That difference may be more fundamental; that may have to do with very high-energy things that happened at the beginning of the universe.
"That's why holding on to them is so important - we need time to study them."
Gerald Gabrielse of Harvard University led one of the groups that in 2002 first produced antihydrogen, and first proposed that the "magnetic bottle" approach was the way to trap the atoms.
"I'm delighted that it worked as we said it should," Professor Gabrielse told BBC News.
"We have a long way to go yet; these are atoms that don't live long enough to do anything with them. So we need a lot more atoms and a lot longer times before it's really useful - but one has to crawl before you sprint.
Professor Gabrielse's group is taking a different tack to prepare more of the antihydrogen atoms, but said that progress in the field is "exciting".
"It shows that the dream from many years ago is not completely crazy."