A Wexford physicist has won a US award for his work on fusion, the energy that powers the stars, writes Dick Ahlstrom
Watch the swirling waters of a stream flow by and you will quickly notice the little eddies and whirlpools that form and make the water shimmer. Imagine how complicated it might be to measure these features, which quickly disappear back under the surface.
An Irish researcher working at the University of California in Los Angeles has added an extra difficulty to the task. The flow he measures is a superheated ion plasma.
"It is very challenging. The conditions we are trying to create are actually hotter than the sun," says Edward Doyle of UCLA's Institute of Plasma and Fusion Research.
Late last year he shared an award for excellence in plasma-physics research given by the American Physical Society. The prestigious prize is given "to recognise a particular recent outstanding achievement in plasma physics", according to the society.
Doyle is originally from Wexford; after a primary and secondary education in Waterford, he took a degree in electrical engineering at University College Cork. He then spent five years in Culham, Oxfordshire, home of the EU's main fusion research centre.
He moved to UCLA in 1985 and has remained there since, mostly working at DIII-D, the university's fusion-research facility, based in San Diego, in southern California. DIII-D is the largest fusion-research centre in the US, he says.
"Fusion is the power source of the sun and the stars. Fusion is about trying to provide an alternative fuel supply for the world."
Bringing to earth the power that drives the sun is no easy matter. It involves heating hydrogen atoms to a temperature at which they can be forced to fuse together to form a helium atom.
Tremendous energy is released in this process, and the reaction must be contained if it is to become a useable source of power.
The scientists contain the energy by using powerful magnetic fields that corral the gas, which is heated to such a degree that it becomes a plasma. The temperatures inside can reach 100 million degrees, says Doyle.
"These are phenomenal temperatures, yet they are being achieved only one metre from the wall of the device," he says.
The plasma and its retaining magnetic fields exist in a device known as a tokamak. It creates a doughnut-shaped space in which the plasma is produced and then studied.
The main problem is energy transport - "the rate at which the heat you put in comes back out". The loss of energy reduces the temperature of the plasma.
The researchers at San Diego wanted to know how to reduce this loss; they found that at least some of the problem was caused by turbulence within the plasma. "These magnetised plasmas behave in many ways like fluids," says Doyle. "The turbulence increases the loss rate."
The group began studying the turbulence and ways to reduce it, in particular, by inducing a flow in the plasma. "Putting up a system of flow in these plasmas can have interesting effects. My role in this was providing the turbulence-measurement part of the story."
The team developed several ways to induce a flow, including using electrical fields and striking the plasma with a beam of neutral atoms, which deliver momentum to the plasma.
Measurement is equally difficult. One method involves measuring the way turbulence in the plasma scatters a 280 gigahertz microwave beam. Another is reflectometry, using radio waves or microwaves that bounce back from the turbulence. By varying the frequency, the team can reach into different plasma depths.
The award highlighted their success in reducing turbulence by controlling the flow of the plasma and so reducing energy transport. Doyle's devices were able to show how the eddies were reduced, proving their work.
While fusion energy is still a considerable distance away, Doyle believes the day when a working reactor becomes a reality has been brought that bit closer.