Physicists have uncovered a surprisingly straightforward
strategy for turning light into matter.
The design, published in
Nature Photonics, adapts technology used in fusion research and can be
implemented at existing facilities in the UK. Several locations could now enter a race to convert photons into positrons
and electrons for the very first time. This would prove an 80-year-old theory by Breit and Wheeler, who themselves
thought physical proof was impossible. Now, according to researchers from Imperial College London, that proof is
within reach.
Prof. Steven Rose and his PhD student, Oliver Pike, told the BBC it could
happen within a year. With a good experimental team, it should be quite doable," said Mr. Pike.
If the experiment comes to fruition, it will be the final piece in a puzzle
that began in 1905, when Einstein accounted for the photoelectric effect with
his model of light as a particle.
Several other basic interactions between matter and light have been described
and subsequently proved by experiment, including Dirac's 1930 proposal that an
electron and its antimatter counterpart, a positron, could be annihilated upon
collision to produce two photons.
Breit and Wheeler's theoretical prediction of the reverse - that two photons
could crash together and produce matter (a positron and an electron) - has been
difficult to observe.
"The reason this is very hard to see in the lab is that you need to throw an
awful lot of photons together - because the probability of any two of them
interconverting is very low," Prof Rose explained.
His team proposes gathering that vast number of very high-energy photons by
firing an intense beam of gamma-rays into a further cloud of photons, created
within a tiny, gold-lined cylinder.
That cylinder is called a "hohlraum," German for "hollow space", because it
contains a vacuum, and it is usually used in nuclear fusion research. The cloud
of photons inside it is made from extraordinarily intense X-rays and is about as
hot as the Sun.
