It’s interesting what three physicists can come up with over a cup of coffee. When a theoretical physicist from the Max Planck Institute for Nuclear Physics was passing through Imperial College London, a casual coffee in a tiny office at Imperial's Blackett Physics Laboratory led to a monumental scientific breakthrough. In just a day, the three physicists discovered how to create matter from light.
Eighty years ago in 1934, scientists Breit and Wheeler proposed that if two particles of light (photons) are smashed together, an electron and positron will be created. This was the simplest methods ever predicted to turn light into matter. It has never been proved, never seen in a laboratory and the scientists never thought it would ever be able to be demonstrated.
The new research, “A photon–photon collider in a vacuum hohlraum,” announced on May 18, 2014 will be published in Nature Photonics. It will explain how Breit and Wheeler’s theory can be proven in practice with a ‘photon-photon’ collider that will recreate a process found in the first 100 seconds of the universe.
If this demonstration is successful, it will supply the last piece of a seven piece light-matter jigsaw puzzle. The six other pieces are: Compton scattering (Arthur H. Compton, 1923), the photoelectric effect (Albert Einstein, 1905), electron-positron annihilation (Dirac observed by Klemperer in 1934), single photon annihilation (Blackett and Occhialini, 1933), the Bethe-Heitler mechanism of pair production (observed by Anderson in 1932) and Bremsstrahlung “braking radiation” discovered by Roentgen in 1895.
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 (German for '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 centre 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.
Professor Steve Rose from the Department of Physics at Imperial College London said:
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. As we are theorists we are now talking to others who can use our ideas to undertake this landmark experiment.
John F. Gunion from U.C. Davis in a paper, “The Need for a Photon-Photon Collider in addition to LHC & ILC for Unraveling the Scalar Sector of the Randall-Sundrum Model” way back in 2004 suggested a photon-photon collider would provide a crucial complement to the LHC and a future ILC collider. Also in a November 5, 2008 article, “Should a photon-photon collider precede the ILC?” former director of Japan's KEK laboratory and former International Committee on Future Accelerators chairperson, Hirotaka Sugawara proposed to build a photon-photon collider prior to building the six billion dollar ILC.
He said, “A photon-photon collider could generate Higgs bosons, directly, requiring only 160 GeV of energy (if the LHC found the Higgs is in the low-energy range) and would be a less expensive alternative saving millions of dollars in operating costs.”
Sugawara predicted that the cost of a photon-photon collider would be well under half that of the ILC. The 2008 economic crisis led the United States and United Kingdom to cut funds to the ILC collider project. Now with this new discovery for a new photon-to-photon collider, maybe Sugawara was on to something.