World's most powerful laser to trigger fusion reaction this year
A pivotal step in the march towards fusion power, the ''holy grail'' of sustainable clean energy, could be taken this year.
大踏步走向核聚變的一關鍵步驟，那''聖杯'' 滿有可持續的清潔能源，可在今年作出。
Published: 7:30AM GMT 01 Feb 2010
Scientists have spent decades chasing the dream of fusion power, which holds out the promise of producing unlimited amounts of clean energy from hydrogen, the most abundant element in the universe. Photo: AP科學家們已經花費了幾十年追逐核聚變發電的夢想，它保有那承諾由氫生產無限量的潔淨能源，在宇宙中最豐富的元素。 圖片：美聯社
Scientists in the US are preparing for the dramatic moment when the world's most powerful laser unleashes the nuclear force that lights up the sun and achieves ''ignition''.
美國科學家正在準備那戲劇性的時刻，當世界上最強大的激光釋放出核力量，照亮太陽和達到"點火 '''。
At that moment, 192 laser beams housed in a building the size of three football pitches will focus on a target the size of a peppercorn to trigger a self-sustaining fusion reaction.
在那一刻，設在大如三個足球場的建築物中的192株激光束，將集中於一個大小如乾胡椒的目標，去誘發一自我維持的聚變反應。
If all goes according to plan, this could be achieved in October. Although no more than a test of the technology, it could mark the start of a revolution that will change the science and politics of energy for ever.
如果一切按計劃進行，這可能在10月達到。雖然只不過是科技的測試，但它可能標誌著一個革命的開始，將永遠改變能源的科學和政治。
Scientists have spent decades chasing the dream of fusion power, which holds out the promise of producing unlimited amounts of clean energy from hydrogen, the most abundant element in the universe.
Nuclear fusion happens when the nuclei of atoms are driven together so hard that they fuse to form a heavier particle. A self-sustaining chain reaction occurs as more atomic nuclei collide, releasing huge amounts of energy in the process.
Stars are driven by nuclear fusion, as is the immense destructive power of the hydrogen bomb. But no one has yet managed to contain and sustain a fusion reaction under controlled conditions.
The biggest problem facing fusion scientists is how to generate the enormous temperatures and pressures necessary for long enough in a confined space.
Self-sustaining fusion requires conditions more extreme than at the centre of the Sun, with temperatures of around 100 million centigrade.
At the new National Ignition Facility (NIF) at Lawrence Livermore National Laboratory in California, scientists are closer to overcoming this hurdle than anyone has been before.
The 10-storey high NIF is a £2 billion sledgehammer built to crack a nut.
Opened last year, the facility houses an array of optical and electronic devices designed to split a laser 192 ways and boost the combined energy of the beams to 1.8 megajoules.
At its heart the ''nut'' is a tiny beryllium capsule the size of a peppercorn, designed to hold a dash of nuclear fuel in the form of deuterium and tritium.
Both are isotopes, or different atomic versions, of hydrogen.
The aim is to focus the laser beams on the capsule and blast it with a pulse of energy that causes the fuel to implode in an instant, reaching temperatures and pressures greater than those at the centre of the Sun.
Crushed together, the deuterium and tritium nuclei will fuse, releasing a flash of energy. If the experiment is a success, more energy will be generated than was pumped into the capsule in the first place.
A report of the latest progress at the NIF published last week in the journal Science shows that the scientists are on target.
Dr Siegfried Glenzer and colleagues described the first experiments in which all 192 of the lasers were tested on targets empty of fuel, achieving a beam energy of about 40% the NIF's maximum.
A major problem that had to be overcome was getting the capsule to implode evenly.
This was done by encasing it in a gold cylinder called a hohlraum, pierced by holes through which the laser beams were shone.
''We're doing the real thing, and it's going better than expected,'' said Dr Glenzer, quoted in a Science news article.
The facility's ''ignition campaign'', leading to the first attempt to produce a self-sustaining fusion reaction is due to start in earnest in May.
A decision will be made in July on whether or not to push ahead with full-scale fusion experiments paving the way to ignition in October.
British expert Professor Mike Dunne, director of the Central Laser Facility at the Rutherford Appleton Laboratory in Didcot, Oxfordshire, said: ''It's come up better than anyone thought. They're ahead of the curve predicted.''
http://www.telegraph.co.uk/science/science-news/7117774/Worlds-most-powerful-laser-to-trigger-fusion-reaction-this-year.html
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