Fusion energy progress by Livermore scientists
Published 4:00 am, Wednesday, April 11, 2012
Livermore scientists report that after years of experiments, they have moved closer to reproducing the blazing energy of the sun's interior in the laboratory.
A team of physicists and engineers at the $3.5 billion National Ignition Facility said they fired an array of 192 laser beams, focused "in perfect unison," and created a single pulse of energy that for 23 billionths of a second generated a thousand times more power than the entire United States consumes in a single second.
The experiment March 15 delivered to the center of the facility's target chamber 1.87 megajoules of ultraviolet light, amounting to 100 times more energy than any other laser system in the world, the scientists said in a report.
A megajoule is a million joules of energy, the equivalent of a million watts of electric power. In this one experiment, the virtually instantaneous shot generated 411 trillion watts of power, the scientists said.
The ultimate goal of the multibillion-dollar laboratory experiments is to safely mimic in miniature the immensely powerful thermonuclear explosions of hydrogen bombs so that experts can validate their bomb-making computer codes and verify the safety and reliability of America's arsenal of nuclear weapons.
To achieve that kind of explosion, the facility's 192 laser beams would have to be focused so precisely and be delivered at such immensely high energy that the combined single beam would crush a tiny capsule of frozen hydrogen gas no bigger than a peppercorn and ignite a thermonuclear reaction inside the capsule.
In nature those reactions are known only in the interior of the sun and the stars, and the physics involved is so difficult that it demands far more megajoules of energy than has so far been reached. At the start of the experiments two years ago, the scientists' goal was an energy beam of only a single megajoule, but in shot after shot energy has increased slowly.
The huge lab known as the NIF, 10 stories high and bigger than a football field, was completed three years ago. Its massive building, heavily guarded and highly classified, stands on isolated ground inside the Lawrence Livermore National Laboratory.
Scientists associated with the ignition effort predicted at first they would achieve ignition in 2010, and again last year. Ed Moses, leader of the NIF program, and his colleagues next set the goal of ignition for this October, and now the aim is to achieve it by the end of the year.
Moses is not making any firm predictions now.
"We are encouraged with our progress and look forward to the knowledge we will gain this year," he said. "Hopefully this will include demonstrating fusion burn," another term for ignition.
Doubts about experiments
Many scientists have long voiced doubts that the experiments could ever yield enough energy to achieve ignition, and it's still an open question whether thermonuclear reactions can ever be achieved in the laboratory. Last month a committee of experts preparing a report on the future of fusion research for the National Academy of Sciences expressed continued doubts.
"The scientific and technological progress in inertial confinement fusion has been substantial during the past decade. However, many of the technologies needed for an integrated inertial fusion energy system are still at an early stage of technological maturity," the committee said in a statement. "For all approaches to inertial fusion energy there remain critical scientific and engineering challenges."
Stephen Bodner, retired director of the laser-fusion program at the Naval Research Laboratory in Washington and a longtime public critic of the ignition project, said he was highly skeptical of the significance of the latest development. Bodner has advocated a completely different approach to creating the unimaginably high temperatures and pressures required for achieving fusion.
"Was it just a gimmick shot, achieved without any real progress ... and done only to demonstrate some sort of program progress?" he asked in an e-mail. "It appears that they are just floundering about as they try to solve the many basic problems with their ignition target design."
The facility's campaign has been running at a budget of more than $450 million a year. This year its budget is $474 million, and the president's budget request would cut that total to about $460 million.