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Longlived antimatter hybrid points to gamma ray laser
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Paul Wesley-Griggs/untitled
How to build a laser with antimatter
HALF matter, half antimatter, be used to make a gamma ray positronium atoms teeter on the laser. It would produce a highly brink of annihilation. Now there’s energetic beam of extremely a way to make these unstable short wavelength that could probe atoms survive much longer, a key tiny structures including the step towards making a powerful atomic nucleus – the wavelength gamma-ray laser. of visible light is much too long All the elements in the periodic to be of any use for this. table consist of atoms with a The trouble is that this means nucleus of positively charged assembling a dense cloud of protons, orbited by the same positronium in a quantum number of negatively charged state known as a Bose-Einstein electrons. Positronium, symbol “The positronium atoms Ps, is different. It consists of an behave in lockstep – when electron and a positron orbiting one annihilates, the rest each other (see diagram, right). follow, producing a laser” A positron is the electron’s antimatter counterpart. Though condensate (BEC). How to do positively charged like the this without the positronium proton, it has just 0.0005 times annihilating in the process its mass. Positronium “atoms” was unclear. survive less than a millionth of Now a team led by Christoph a second before the electron and Keitel of the Max Planck Institute positron annihilate in a burst of AD_ NSUNI SEP_ 1 1 . p d f Pa ge 1 2 4 / 8 / 1 1 , 3 : 2 0 PM 101_Statoil_advertPart4_131211.pdf 1 13/12/2011 10:42 for Nuclear Physics in Heidelberg, gamma rays. –Take a laser to make a laser– In principle, positronium could Germany, suggests that ordinary
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24/08/11 2:06 PM
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Introducing positronium Ordinary atoms contain the same number of protons and electrons Hydrogen atom ELECTRON
—
+
PROTON
But we can make a short-lived “atom” with matter and antimatter, which annihilates to produce gamma rays Positronium atom POSITRON (antimatter equivalent of electron)
+ ELECTRON —
lasers could be used to slow the annihilation. The trick is to tune the lasers to exactly the energy needed to boost the positronium into a higher energy state, in which the electron and positron orbit farther from one another. That makes them much less likely to
annihilate (arxiv.org/abs/1112.1621). The positronium will eventually lose energy by emitting photons and return to the annihilationprone state. But the team calculates that about half the excited positronium atoms can survive for 28 millionths of a second on average, 200 times as long as unexcited ones. This may be long enough to assemble the BEC cloud. In a BEC, positronium atoms behave in lockstep, so when one annihilates itself, the rest follow suit, producing a burst of laser radiation made of gamma rays. It may sound like a lot of work, but one thing makes the task easier. Ordinary atoms can only form a BEC when cooled gradually to within a fraction of a degree of absolute zero. By contrast, due to quantum effects, positronium will form a BEC at close to room temperature. David Shiga n
Where mirror, dark and anti-matter meet Half a century after it was first made, and vanish without these emissions. positronium could find uses. As well The idea could be tested by as powering a gamma ray laser (see trapping positronium in a chamber main story), it might put the strange and keeping track of how much theory of mirror matter to the test. energy it gives off as gamma rays. If The idea that every particle has an the amount is smaller than expected identical – but so far undetectable – based on the number of positronium mirror partner was dreamed up to atoms that entered the chamber, explain baffling asymmetries in then some of it may be turning into the emission of electrons from mirror matter. New calculations radioactive atoms. Mirror matter has by Sergei Demidov of the Institute also been touted as a candidate for for Nuclear Research in Moscow, the mysterious dark matter that Russia, and colleagues indicate this makes up 80 per cent of the universe. should happen often enough to be The theory says that particles detectable (arxiv.org/abs/1111.1072). of ordinary matter might very Paolo Crivelli of the Swiss Federal occasionally transform into their Institute of Technology in Zurich is mirror-reversed versions, effectively leading the development of one disappearing from view. Positronium such experiment (arxiv.org/ normally ends its life by hurling out a abs/1005.4802). The existing AEgIS flurry of gamma rays. If the mirror antimatter experiment at CERN near world N exists, S 1 8 positronium 7 4 _ A t might h e i s t _ Geneva, Q P . pSwitzerland, df P acould g e also 1 be 2 8 / 1 1 sometimes turn into mirror matter modified for this purpose.
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Paul Wesley-Griggs/untitled
How to build a laser with antimatter
HALF matter, half antimatter, be used to make a gamma ray positronium atoms teeter on the laser. It would produce a highly brink of annihilation. Now there’s energetic beam of extremely a way to make these unstable short wavelength that could probe atoms survive much longer, a key tiny structures including the step towards making a powerful atomic nucleus – the wavelength gamma-ray laser. of visible light is much too long All the elements in the periodic to be of any use for this. table consist of atoms with a The trouble is that this means nucleus of positively charged assembling a dense cloud of protons, orbited by the same positronium in a quantum number of negatively charged state known as a Bose-Einstein electrons. Positronium, symbol “The positronium atoms Ps, is different. It consists of an behave in lockstep – when electron and a positron orbiting one annihilates, the rest each other (see diagram, right). follow, producing a laser” A positron is the electron’s antimatter counterpart. Though condensate (BEC). How to do positively charged like the this without the positronium proton, it has just 0.0005 times annihilating in the process its mass. Positronium “atoms” was unclear. survive less than a millionth of Now a team led by Christoph a second before the electron and Keitel of the Max Planck Institute positron annihilate in a burst of AD_ NSUNI SEP_ 1 1 . p d f Pa ge 1 2 4 / 8 / 1 1 , 3 : 2 0 PM 101_Statoil_advertPart4_131211.pdf 1 13/12/2011 10:42 for Nuclear Physics in Heidelberg, gamma rays. –Take a laser to make a laser– In principle, positronium could Germany, suggests that ordinary
386mm w x 117mm deep DPS page horizontal
| 24/31 2729 USY The New Scientist advert 24Aug.indd 1 6 | NewScientist December 2011
24/08/11 2:06 PM
For daily news stories, visit newscientist.com/news
Introducing positronium Ordinary atoms contain the same number of protons and electrons Hydrogen atom ELECTRON
—
+
PROTON
But we can make a short-lived “atom” with matter and antimatter, which annihilates to produce gamma rays Positronium atom POSITRON (antimatter equivalent of electron)
+ ELECTRON —
lasers could be used to slow the annihilation. The trick is to tune the lasers to exactly the energy needed to boost the positronium into a higher energy state, in which the electron and positron orbit farther from one another. That makes them much less likely to
annihilate (arxiv.org/abs/1112.1621). The positronium will eventually lose energy by emitting photons and return to the annihilationprone state. But the team calculates that about half the excited positronium atoms can survive for 28 millionths of a second on average, 200 times as long as unexcited ones. This may be long enough to assemble the BEC cloud. In a BEC, positronium atoms behave in lockstep, so when one annihilates itself, the rest follow suit, producing a burst of laser radiation made of gamma rays. It may sound like a lot of work, but one thing makes the task easier. Ordinary atoms can only form a BEC when cooled gradually to within a fraction of a degree of absolute zero. By contrast, due to quantum effects, positronium will form a BEC at close to room temperature. David Shiga n
Where mirror, dark and anti-matter meet Half a century after it was first made, and vanish without these emissions. positronium could find uses. As well The idea could be tested by as powering a gamma ray laser (see trapping positronium in a chamber main story), it might put the strange and keeping track of how much theory of mirror matter to the test. energy it gives off as gamma rays. If The idea that every particle has an the amount is smaller than expected identical – but so far undetectable – based on the number of positronium mirror partner was dreamed up to atoms that entered the chamber, explain baffling asymmetries in then some of it may be turning into the emission of electrons from mirror matter. New calculations radioactive atoms. Mirror matter has by Sergei Demidov of the Institute also been touted as a candidate for for Nuclear Research in Moscow, the mysterious dark matter that Russia, and colleagues indicate this makes up 80 per cent of the universe. should happen often enough to be The theory says that particles detectable (arxiv.org/abs/1111.1072). of ordinary matter might very Paolo Crivelli of the Swiss Federal occasionally transform into their Institute of Technology in Zurich is mirror-reversed versions, effectively leading the development of one disappearing from view. Positronium such experiment (arxiv.org/ normally ends its life by hurling out a abs/1005.4802). The existing AEgIS flurry of gamma rays. If the mirror antimatter experiment at CERN near world N exists, S 1 8 positronium 7 4 _ A t might h e i s t _ Geneva, Q P . pSwitzerland, df P acould g e also 1 be 2 8 / 1 1 sometimes turn into mirror matter modified for this purpose.
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New ScieNtiSt coNNect
Join now
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Start your search now at: http://dating.newscientist.com
24/31 December 2011 | NewScientist | 7