[ti:US Scientists Announce Major Advance in Fusion Development] [by:www.51voa.com] [00:00.00]更多听力请访问51VOA.COM [00:00.04]American scientists have announced [00:02.88]a "major scientific breakthrough" [00:06.04]in the long-sought search for a way [00:09.20]to use nuclear fusion to produce energy. [00:13.60]The announcement came Tuesday [00:16.76]during a briefing by U.S. Energy Secretary Jennifer Granholm [00:22.36]and other officials in Washington, D.C. [00:26.92]Granholm said that, for the first time, [00:30.92]a fusion reaction experiment [00:33.84]had produced more energy [00:36.40]than was required to ignite it. [00:40.28]Scientists describe such a result as "net energy gain." [00:46.44]This state has until now been an unreachable goal [00:51.20]for the scientists because fusion happens [00:55.08]at extremely high temperatures and pressures. [00:59.00]This makes the process very difficult to control. [01:04.28]The new result came last week during an experiment carried out [01:09.84]by government scientists at the National Ignition Facility [01:14.92]at the Lawrence Livermore National Laboratory in California. [01:20.60]The lab is part of the U.S. Department of Energy. [01:25.80]Fusion happens when the nuclei of two atoms [01:30.00]are subjected to extreme heat. [01:32.88]This leads to the formation of a new, [01:36.28]larger atom and the release of energy. [01:39.68]Fusion is the process that fuels stars, including the sun. [01:45.92]Scientists have long understood how nuclear fusion works. [01:51.36]Many have tried to repeat the process on Earth. [01:55.92]The current efforts centered on fusing a pair [01:59.68]of hydrogen isotopes — deuterium and tritium. [02:04.68]The Department of Energy says that the combination [02:08.88]releases "much more energy than most fusion reactions." [02:13.88]It also requires less heat to do so. [02:18.68]Some experts have suggested that fusion energy [02:22.84]could one day be used to provide limitless, pollution-free power. [02:28.64]Granholm and other officials said Tuesday [02:32.40]that the latest result is a major step forward [02:36.24]in helping to create a future source [02:39.36]for clean power generation. [02:42.84]However, they said commercialization of the technology [02:47.36]will likely take many years to be fully developed. [02:51.32]Granholm said the department's ignition success [02:55.56]permits scientists for the first time [02:58.84]to copy "certain conditions [03:01.64]that are found only in the stars and the sun." [03:05.48]She added that the result is a major step [03:09.20]toward "the possibility of zero-carbon abundant [03:13.40]fusion energy powering our society." [03:17.20]The experiments involved aiming nearly 200 lasers [03:22.36]at a small capsule that contained fuel. [03:25.96]When the lasers ignited the fuel, [03:29.28]two lighter atoms were joined together [03:32.32]to create a denser one. [03:34.56]This process produced more energy [03:38.28]than was required to ignite it, the scientists said. [03:43.24]The experiment briefly reached "fusion ignition" [03:47.32]by generating 3.15 megajoules of energy output. [03:53.64]This was after the laser targeting the capsule [03:57.48]used 2.05 megajoules of energy, [04:01.64]the Energy Department said. [04:04.16]A megajoule is a measurement for energy output. [04:08.60]Nuclear scientists not involved in the latest result [04:13.28]praised the success as a major breakthrough. [04:17.12]But they noted there is much more science to be done [04:21.00]before fusion can develop into a profitable industry. [04:25.56]Riccardo Betti is a professor at New York's University of Rochester [04:31.68]and an expert in laser fusion. [04:34.84]He compared the latest result to when humans first learned [04:40.04]that refining oil into gasoline and igniting it [04:44.52]could produce an explosion. [04:47.88]"You still don't have the engine, [04:50.48]and you still don't have the tires," Betti said. [04:54.40]"You can't say that you have a car." [04:57.60]Tony Roulstone is a nuclear energy expert [05:02.08]at the University of Cambridge in Britain. [05:05.12]He told Reuters news agency that while interesting, [05:10.08]the latest experiment still leaves scientists a long way [05:15.24]from turning the process into useful, limitless energy. [05:20.84]Roulstone said that in order to become commercially successful, [05:26.20]a power plant would have to produce enough energy [05:30.28]to also power the laser equipment [05:33.20]and generate a continuous ignition process. [05:38.20]I'm Bryan Lynn. 更多听力请访问51VOA.COM