It generally takes a decent-sized particle accelerator to produce antimatter, but a team of physicists working at the University of Michigan says they've developed a table-top system that can create short bursts of positrons – anti-electrons.
Their metre-long device creates electron-positron pairs by firing a petawatt laser at helium gas. For this they used the HERCULES laser at the university*.
This results in a stream of electrons moving at relatavistic speeds, which are directed to a thin gold foil. The collisions between the high-speed electrons and the individual metal atoms resulted in a stream of electrons and positrons, which are easily separated using magnets.
Each 30 femtosecond firing of the laser produces “quadrillions” of positrons, the researchers say, which is comparable to the densities observed at CERN.
Never fear, however: as the image below shows, a mere lump of Teflon is sufficient to absorb the positrons, so the setup doesn't actually risk the earth-shattering kaboom of a matter-antimatter annihilation.
One reason researchers are interested in making antimatter experiments accessible outside the rarefied world of big particle colliders is because electrons and positrons make up the jet streams emitted by black holes and pulsars. Clearly, producing them in labs is simpler and more accessible to measurement than relying solely on what's observed by astronomers.
In the abstract of their paper, the international team that worked out of the University of Michigan states that “The detected positron beam propagates with a high-density electron beam and γ rays of similar spectral shape and peak energy, thus closely resembling the structure of an astrophysical leptonic jet. It is envisaged that this experimental evidence, besides the intrinsic relevance to laser-driven particle acceleration, may open the pathway for the small-scale study of astrophysical leptonic jets in the laboratory”.
The experimental setup: it fits on a tabletop
- if you don't count the room-sized laser! Source: University of Michigan
As the pre-press version of the paper at Arxiv notes, the setup might also be useful for observing matter / antimatter asymmetries, as well as optically-driven electron-positron collider setups. ®
*Bootnote: HERCULES is somewhat larger than “tabletop” size. It's a rather large beast – so perhaps the description is stretching things just a little. ®