Thursday, September 06, 2007

Laser Fusion Project gets Go-Ahead.

A British-led team of researchers intend to use mighty lasers to promote nuclear fusion, which some think will provide us with effectively limitless energy in the face of the looming world energy crisis. The project, known as HiPER, will be instigated in the UK, which aims to use such intense lasers to create the temperatures millions of degrees required for hydrogen (tritium and deuterium) nuclei to fuse, releasing more energy it is intended in the process than is required to power the lasers. This is currently a problem with fusion, but scientists believe that by using a laser of petawatt power (10,000 times the output of the UK national grid) in very short duration pulses, and if the laser can fire repeatedly on a fraction of a second timescale, it should be possible to create a sustainable source of energy that could be drawn-off to produce electricity.

The practicalities have been evaluated by a panel of European experts, who have approved the project. This is, in effect, a green-light for the seven year project which will cost around £500 million ($1 billion). Hiper is a development of work done in the US, and it is thought that it could provide the means for generating electricity within 20 years. When deuterium and tritium nuclei fuse a helium nucleus is formed and large amounts of energy are released. Deuterium can be extracted from seawater and tritium is produced within the reactor itself. To produce the high temperatures (above 40 million degrees) required to overcome the electrostatic repulsion between the positively charged nuclei so that they can fuse requires a lot of energy, and the balance of output to input must favour the former.

Magnetic confinement is required to hold the high temperature plasma together, since all materials known on Earth would simply be vapourised in contact with it. The strategy is that a pulsed laser with a power of one petawatt (one million billion watts) is fired at a fuel pellet just 2 millimetres in diameter. An enormous pressure is generated that squashes the pellet down to a width of just a few microns (thousands of a millimetre).

Speaking from the Rutherford Appleton Laboratory, Professor Mike Dunne said, "To put that into perspective, the laser is 10,000 times the power of the entire UK national grid. And then you're going to focus that down onto a spot that's 10 to 100 times smaller than the width of a human hair. The pressure is equivalent to 10 Nimitz class aircraft carriers sitting on your thumb. Some pretty crazy things are going to happen, and that's what we're about."

I'm sure he's right, but is the technology really going to arrive in time to circumvent an energy crisis that will arrive within 10 - 20 years? I don't think we should place all our bets on it just yet, and the dearth of energy to power the world's transportation network is not obviously cured by HiPER, or the analogous ETIR fusion programme either, which is thought will not produce power commercially for another 60 years.

Related Reading.
"Green light for fusion project," By Mark Henderson, Timesonline, September 3, 2007:

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