By Jonathan Fildes
Science and technology reporter, BBC News
The lasers concentrate huge amounts of energy into a tiny point
When the first lasers were developed in the 1960s they were described as "a solution looking for a problem."
Today, the beams of light are ubiquitous, crammed into everything from CD players and phone networks to supermarket checkouts and research laboratories. They have found many problems to solve.
But if an international team led by UK scientists gets its way, lasers could soon face their biggest challenge yet: solving the world's energy crisis in an environmentally friendly way.
Researchers from the Rutherford Appleton Laboratory (RAL) in Oxfordshire, working with partners from 14 countries, have tabled a proposal to use lasers to recreate the physical reactions at the heart of the Sun.
In just one cubic kilometre of seawater there is the equivalent energy of the world's oil reserves
Harnessing nuclear fusion, as the process is known, would offer almost unlimited energy without the release of greenhouse gases such as carbon dioxide.
A proposal to fund the set-up costs of a project called Hiper (High Power Laser Energy Research) is currently being considered by the EU.
If the team gets the 50m Euros (£35m) it is asking for to kick-start the project, it would put the researchers on a path that could eventually see an 800m-euro (£500m) working demonstration reactor opened towards the end of the next decade, and commercial reactors soon after that.
"This is not an immediate solution to the world's energy demand," admits Professor Mike Dunne, director of the project at RAL. "But if we're very aggressive you could have a power reactor on the ground by 2030."
Nuclear fusion has long been a dream of scientists. The idea is to fuse together two heavier forms of hydrogen, known as deuterium and tritium, to form helium.
These isotopes of hydrogen are readily available.
"In just one cubic kilometre of seawater there is the equivalent energy of the world's oil reserves," says Professor Dunne. "So it's almost limitless fuel."
1. Powerful lasers irradiate a fuel capsule causing the outer layer to rapidly expand.
2. The fuel capsule's core increases in density, converging at the tip of a gold cone.
3. An intense ignition laser is fired into the gold cone producing energetic electrons.
4. Electrons bombard the fuel raising its temperature to 100 million Celsius, initiating fusion.
When the isotopes are combined at high temperatures, a small amount of mass is lost and a colossal amount of energy is released. By-products are no more radioactive than hospital waste.
In the core of the Sun, huge gravitational pressure allows this to happen at temperatures of around 10 million Celsius. At the much lower pressures on Earth, temperatures to produce fusion need to be much higher - above 100 million Celsius.
Hiper would achieve these extreme temperatures using ultra powerful lasers - some will concentrate the equivalent of ten thousand times the power of the national grid into a spot less than a millimetre across.
The whole scheme has been drawn up to capitalise on a US project at the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory in California.
Scheduled for completion in 2010, the massive NIF laser is expected to prove to the world that laser fusion will work and should be taken seriously.
"That will move it from the scientific field to the public and political field," says Professor Dunne.
"Everything from then on is just mere detail - it's technology and engineering."
The NIF laser and Hiper take very different approaches to laser fusion. Professor Dunne compares it to the differences between a diesel and petrol engine.
"Nif is the diesel approach," he says. "You shine lasers at a pellet of material and compress it to such a point that its temperature and density reach a point that allows fusion reactions."
It sounds like a lot of money, but in the greater scheme of things, half a billion dollars to solve the world's energy problems is nothing
In contrast, Hiper will use two sets of lasers: one to compress the fuel pellet and another, like a spark plug, to ignite it. Using this set up means that the fuel does not need to be compressed as much as it does with NIF, overcoming a major hurdle.
"It's like trying to squeeze jelly," explains Professor Bob Bingham, also of the RAL. "You want to squeeze in a way that it doesn't come back out through your fingers. That really is the key."
Nif engineers get round this problem by using ultra precise lasers and near-perfect shaped fuel pellets, both of which are delicate, time consuming and unlikely to be ever viable routes to a commercial reactor.
Using the secondary laser, a technique first demonstrated by Japanese scientists, means the machinery of Hiper can be a bit more rough and ready.
But the Hiper team will not have it all its own way.
There is still a lot of work to be done on the lasers, particularly getting them to fire rapidly enough to sustain fusion in a reactor.
At the moment, large powerful lasers need several minutes to draw in enough power to fire. A laser fusion reactor would need to fire several times a second and be an order of magnitude more efficient than today's beams.
ITER - NUCLEAR FUSION PROJECT
Project estimated to cost 10bn euros and will run for 35 years
It aims to produce the first sustained fusion reactions
Final stage before full prototype of commercial reactor is built
"The lasers required have never been realised," says Dr Duarte Borba, who works at JET, a fusion reactor down the road from where the Hiper team are based.
Jet takes another approach to nuclear fusion, using superconducting magnets to contain and fuse the hydrogen nuclei.
This is the same technique used by the poster child of nuclear fusion: the 10bn-euro International Thermonuclear Experimental Reactor (Iter) currently being built in Cadarache, southern France.
"The main technology for magnetic fusion has already been designed and tested," says Dr Borba. "What is need is to integrate everything into one project and show that it works. That's where Iter comes in."
The scheme will run for 35 years and if all goes well with the experimental reactor, officials hope to set up a demonstration power plant at Cadarache by 2040, perhaps giving the Hiper team enough time to steal a march on its magnetic rivals.
A decision on whether to fund the initial stages of Hiper will be announced by the EU in July 2007. And once the ball is rolling, the scientists and engineers hope it will be a proposition politicians cannot ignore.
"It sounds like a lot of money," says Professor Dunne. "But in the greater scheme of things, half a billion dollars to solve the world's energy problems is nothing."
Others already seem to agree.
The UK funding bodies, including the Science and Technology Facilities Council that own and operate most of the UK's large science instruments, are making positive noises about stumping up the necessary cash to build and host Hiper in the UK.
"We will be considering whether to put it into our roadmap towards the end of the year and I think the likelihood is that we will," said Keith Mason, Chief Executive of the STFC. "We are very interested in Hiper."