Scientists create billions of particles of anti-matterNovember 18th, 2008 - 5:45 pm ICT by IANS
Washington, Nov 18 (IANS) When you shoot laser through a gold bit the size of a pinhead, suddenly more than 100 billion particles of anti-matter materialise.The anti-matter, also known as positrons, shoots out of the target in a cone-shaped plasma “jet.”
This new ability to create a large number of positrons in a small lab opens the door to several fresh avenues of anti-matter research, including an understanding of the physics underlying phenomena such as black holes and gamma ray bursts.
Anti-matter research also could reveal why more matter than anti-matter survived the Big Bang at the start of the universe.
“We’ve detected far more anti-matter than anyone else has ever measured in a laser experiment,” said Hui Chen, Lawrence Livermore National Lab researcher who led the experiment. “We’ve demonstrated the creation of a significant number of positrons using a short-pulse laser.”
Chen and her colleagues used a short, ultra-intense laser to irradiate a millimeter-thick gold target. “Previously, we concentrated on making positrons using paper-thin targets,” said Scott Wilks, who designed and modelled the experiment using computer codes.
“But recent simulations showed that millimeter-thick gold would produce far more positrons. We were very excited to see so many of them,” he said.
In the experiment, laser ionises and accelerates electrons, which are driven right through the gold target. On their way, the electrons interact with the gold nuclei, which serve as a catalyst to create positrons.
The electrons give off packets of pure energy, which decays into matter and anti-matter, following the predictions by Einstein’s famous equation that relates matter and energy, said a Livermore release.
By concentrating the energy in space and time, the laser produces positrons more rapidly and in greater density than ever before in the laboratory.
Particles of anti-matter are almost immediately annihilated by contact with normal matter, and converted to pure energy (gamma rays).
There is considerable speculation as to why the observable universe is apparently almost entirely matter, whether other places are almost entirely anti-matter, and what might be possible if anti-matter could be harnessed.
Normal matter and anti-matter are thought to have been in balance in the very early universe, but due to an “asymmetry” the anti-matter decayed or was annihilated, and today very little anti-matter is seen.
Chen presented her work at the American Physical Society’s Division of Plasma Physics meeting in Dallas.