Scientists Discover How to Turn Light Into Matter

Light rays (Image courtesy Imperial College London)


LONDON, UK, May 19, 2014 (ENS) – Physicists at the Imperial College London have thought up a way to convert light directly into matter in a new type of high-energy physics experiment, using technology already available in the UK.

“As we are theorists, we are now talking to others who can use our ideas to undertake this landmark experiment,” said Professor Steve Rose at the Department of Physics, Imperial College London.

Professor Steve Rose (Photo courtesy Imperial College London)

The proposed experiment would recreate a process that was important in the first 100 seconds of the universe.

The process also is seen in gamma ray bursts, which are the biggest explosions in the universe and one of physics’ greatest unsolved mysteries.

One day over coffee in a tiny office in Imperial’s Blackett Physics Laboratory, three theoretical physicists worked out a way to physically prove a theory first devised in 1934 by American physicists Gregory Breit and John Wheeler.

Breit and Wheeler suggested that it should be possible to turn light into matter by smashing together two particles of light, called photons, to create an electron and a positron, the simplest method of turning light into matter ever theorized.

The calculation was found to be theoretically sound but Breit and Wheeler, who would later help to create the atomic bomb, said that they never expected anybody to physically demonstrate their prediction. It has never been observed in the laboratory and past experiments to test it have required the addition of massive high-energy particles.

Professor Rose said, “Despite all physicists accepting the theory to be true, when Breit and Wheeler first proposed the theory, they said that they never expected it be shown in the laboratory. Today, nearly 80 years later, we prove them wrong.”

“What was so surprising to us was the discovery of how we can create matter directly from light using the technology that we have today in the UK,” said Rose, who serves as vice dean of the Faculty of Natural Sciences at the Imperial College London.

The new research, published in the current issue of the journal “Nature Photonics,” shows for the first time how Breit and Wheeler’s theory could be proven in practice in a “photon-photon collider.”

Electrons passing through a solid gold target are used to create a high-energy photon beam. This is fired into a vacuum hohlraum, where it interacts with high-temperature thermal radiation. (Image by study authors)

The collider experiment that the scientists have proposed involves two key steps.

First, the scientists would use an extremely powerful high-intensity laser to speed up electrons to just below the speed of light.

They would then fire these electrons into a slab of gold to create a beam of photons a billion times more energetic than visible light.

The next stage of the experiment involves a tiny gold can called a hohlraum, which in German means “empty room.”

Scientists would fire a high-energy laser at the inner surface of this gold can, to create a thermal radiation field, generating light similar to the light emitted by stars.

They would then direct the photon beam from the first stage of the experiment through the center of the can, causing the photons from the two sources to collide and form electrons and positrons.

It would then be possible to detect the formation of the electrons and positrons when they exited the can.

Lead researcher Oliver Pike, who is currently completing his PhD in plasma physics, said, “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.”

Light rays (Image courtesy Imperial College London)

“Within a few hours of looking for applications of hohlraums outside their traditional role in fusion energy research, we were astonished to find they provided the perfect conditions for creating a photon collider,” Pike said. “The race to carry out and complete the experiment is on!”

The breakthrough was achieved in collaboration with fellow theoretical physicist Felix Mackenroth from the Max Planck Institute for Nuclear Physics, who happened to be visiting Imperial.

Pike and Edward Hill of the Blackett Physics Laboratory initially proposed the collider concept and, together with Mackenroth, developed the experimental scheme. Pike and Mackenroth performed the analysis and wrote the manuscript. Pike carried out the Monte Carlo simulations. Professor Rose guided the project.

Their study entitled, “A photon-photon collider in a vacuum hohlraum,” was published online May 18.

The research was funded by the Engineering and Physical Sciences Research Council, the John Adams Institute for Accelerator Science, and the Atomic Weapons Establishment, and was carried out in collaboration with Max-Planck-Institut für Kernphysik.

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