The latest putative technological ray of salvation from the imminent energy crisis that confronts the world is Laser-Fusion. At an expected cost of half a billion Euros, a mighty laser is to be constructed which can create enormous temperatures at which nuclei will fuse. Lasers are currently used to heat plasmas, normally containing tritium and deuterium nuclei, above the ignition temperature of 40 million degrees required to overcome the electrostatic forces whereby the positive charges on these nuclei repel them from one another, getting them close enough that they can fuse-together, releasing energy in the process. The ignition temperatures that must be achieved for other hydrogen nuclei to fuse are far greater than this, hence the focus on the deuterium-tritium couple. However, in all cases I am aware of, it takes more energy to run the laser than is extracted from the plasma itself. This is partly a result of limitations in laser technology, but if an extremely powerful laser can be built, and which furthermore can fire sequentially at a sufficiently rapid rate, scientists believe that a sustainable working fusion reactor might be a possibility. The world's most powerful lasers need several minutes to recover for a second burst, but the HiPER laser will need to fire several times a second.
It is not thought that a commercial reactor will happen any time yet, and I am reminded of the ITER project at Cadarache in France: an experimental thermal fusion reactor project costing ten billion Euros, which it is thought might produce a working reactor in about 60 years, allowing for the various development stages planned. The laser-fusion HiPER project has been earmarked as "priority" by the European Union, and is intended to overtake the US-funded imperative known as the National Ignition Facility (Nif) in Livermore, California. When Nif is built in 2010, physicists are confident that the laser will be sufficiently powerful to start a fusion reaction, and experiments undertaken using underground nuclear explosives in the Nevada desert have provided evidence in regard to just how much energy the laser will need to provide to do this.
Mike Dunne, who is director of the Central Laser Facility in Oxfordshire and where the world's currently most powerful laser, Vulcan, is housed said: "The world is going to take notice when this happens. Politicians are going to look around and say, 'So what are you going to do about it? What is the next step?' This is how to take it from a scientific demonstration to a commercial reality. The trick now is, can we get it to work without throwing a nuclear bomb at the thing?"
Fair enough, but the engineering challenges are huge. Indeed in neither ITER or HiPER have the materials been devised that can withstand either massively energetic neutrons or a mighty laser beam, and without them any commercial development seems unlikely. It is often said that nuclear fusion is an attempt to replicate the processes going on in stars, e.g. the Sun, and yet Earth-bound plasmas are of very low density compared to the huge gravitational pressures in stars which dramatically increase the probability of fusion occurring, e.g. the solar proton-proton cycle which probably could not be reproduced sustainably on Earth.
The world will begin to run short of fossil fuels: first oil, then gas and finally coal, beginning within just a decade for oil. Unless more nuclear fuel is found, nuclear power has only a limited lifetime too, without the development and implementation of breeder technology based on uranium or thorium. The energy clock is ticking away, and I wonder, even if these behemoths can be made to work, not just at all but commercially, how quickly might this be done in reality. 60 years for ITER will almost certainly be too late to come to our aid in the impending energy crisis, and if HiPER has a similar projection in timescale then both may be regarded in the future as white elephants, similar to those architectural follies that pebble-dash the British landscape, which finally served no practical purpose.
"Laser fusion - the safe, clean way to produce nuclear energy," by James Randerson, The Guardian. http://www.guardian.co.uk/nuclear/article/0,,2091037,00.html