Firing new shots (Nuclear Fusion)

The Economist: Firing New Shots (Nuclear Fusion)

Using lasers to trigger fusion could prove cheaper than other techniques.

WHEN lasers were invented in the 1960s they were little more than an exotic curiosity—a solution looking for something to solve. Now that lasers are found in everything from telephone cables to DVD players to the humble laser pointer, they have become almost prosaic. Time, then, to rekindle a little glamour, by using lasers to bring about nuclear fusion, the great prize of energy research. Next month researchers will try to persuade the European Commission to pay for the biggest laser-fusion project yet.

Nuclear fusion is a compelling idea. The sun and stars are daily proof of the great energy released when light atomic nuclei join together. Lots of power could be produced using very little fuel. No greenhouse gases would be released. The fuel is abundant, the process safe and the waste, though radioactive, is far less noxious than the stuff left over from fission. Unfortunately, in spite of more than 50 years' work and billions of dollars of backing, no one has yet managed to get an Earth-bound fusion reaction to produce useful energy.

The idea of using lasers to trigger fusion has a long history. It is partly behind the National Ignition Facility at the Lawrence Livermore National Laboratory in California, due to be completed next year, and a slightly larger effort, called the Laser Mégajoule, in France that is a couple of years further off. Most of the work done by Livermore's 192 powerful lasers, focused on a spot just a millimetre or so across, will be nuclear-weapons research. But some of the time they will blast a pellet of nuclear fuel. The fuel will be made from two heavy forms of hydrogen, called deuterium and tritium. Zap it from all sides simultaneously with the lasers and, scientists hope, the pellet will implode and the hydrogen nuclei will fuse. They would form helium and a subatomic particle, called a neutron. The neutron would carry energy that could be converted into heat. In principle, this heat could be used, as in conventional power plants, to boil water and create steam that drives a turbine.

…….

Lasers offer some obvious advantages over magnetic confinement. Because laser beams can run for long distances, the fuel does not have to be right next to the lasers that generate them. This means they can be easily shielded from the damaging neutrons. Fuel pellets can also be placed in the target site using conventional mechanical systems and these should easily be able to cope with the five mini-explosions a second needed to generate power.

There is one problem with nuclear fusion that lasers cannot solve, however: the price. HiPER may be budgeted to cost just one tenth as much as its magnetic cousin. But $1 billion is a lot of money all the same. Whether the benefits are worth such costs remains written in the stars.