Scientists at Imperial College London have worked out a way to turn light into matter. This is achieved by colliding two photons—the particles of light—to create an electron and a positron. While theoretically this has been considered possible since 1934, when physicists Gregory Breit and John A. Wheeler identified the process, no was sure how to actually achieve it in a lab setting until now.
Last year, a coffee-fueled brainstorming session on a related topic made lead researcher Oliver Pike and two others realize that the technology was now available to put the 80-year-old Breit-Wheeler process into action. Using a very powerful, high-intensity laser electrons can be sped up to just below the speed of light. The electrons are then fired onto a gold slab, producing a beam of photons that is one billion times more energetic than visible light. Then another laser beam is focused on a tiny device made of gold, known as a hohlraum. (Hohlraums are typically used in fusion experiments – and they provided the ‘aha’ moment for the team.)
Firing the laser at the interior of the hohlraum creates a thermal radiation field, which generates light similar to that emitted by stars. In fact, gamma ray explosions are a naturally occurring incident of the process, which also occurred in the first 100 seconds of the universe.
The photon beam produced in the initial step of the experiment would then be aimed onto the hohlraum as well. This will cause the photons from each light source to collide, breaking up into electrons and positrons – and thus, matter.
Explains Pike: “Although the theory is conceptually simple, it has been very difficult to verify experimentally. We were able to develop the idea for the collider very quickly, but the experimental design we propose can be carried out with relative ease and with existing technology. Within a few hours of looking for applications of hohlraums outside their traditional role in research, we were astonished to find they provided the perfect conditions for creating a photon collider. The race to carry out and complete the experiment is on!”
The team has just published their photon-photon collider design in Nature Photonics.