January 7, 2013
New Cooling Process Could Help Scientists Learn More About Antimatter
redOrbit Staff & Wire Reports - Your Universe Online
By aiming a laser at antihydrogen atoms, researchers have found that they can force them to lose energy and plummet to temperatures 25-times colder than previously achieved -- a discovery which could greatly assist the study of the more elusive properties of antimatter.
The method, which was developed by a team of experts from the US and Canada, is described in the most recent edition of the Journal of Physics B: Atomic, Molecular and Optical Physics, "could reduce the average energy of trapped antihydrogen by a factor of more than 10," co-author and Auburn University professor Francis Robicheaux said in a statement on Sunday.
Doing so would allow researchers to make the antiparticle far more stable and "perform more precise measurements of all of its parameters," Robicheaux added. "The ultimate goal of antihydrogen experiments is to compare its properties to those of hydrogen. Colder antihydrogen will be an important step for achieving this."
Normally, antihydrogen atoms are formed in an ultra-high vacuum trap by injecting positron plasma with antiprotons, causing the antiproton to capture a positron, the researchers explained. As a result, the positron gives off an electronically excited antihydrogen atom -- an atom which has so much energy that it can distort any measurements attempted by scientists.
Since only a few atoms of the substance can be trapped at a time, the primary method used by researchers looking to study it is to cool those atoms to very low temperatures using lasers -- a process known as Doppler cooling. While Doppler cooling is used regularly to cool and study atoms, "because of the restricted parameters that are needed to trap antimatter, the researchers need to be absolutely sure that it is possible," they added.
To check the viability of cooling antihydrogen in this way, Robicheaux's team conducted a series of computer simulations. Those simulations revealed that the atoms of this particular form of antimatter could be cooled to approximately 20 millikelvin, while possessing energies of up to 500 millikelvin.
As a result, they believe that this will increase the amount of time that antihydrogen can remain trapped while decreasing loss rate. Furthermore, using Doppler cooling on antihydrogen atoms could allow researchers to measure the gravitational properties of antimatter.
"No one has ever seen antimatter actually fall in the field of gravity. Laser cooling would be a very significant step towards such an observation," noted study co-author Dr Makoto Fujiwara of TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics.