Wouldn't it be great to have abundant, clean power that doesn't contribute to climate change? That is the promise of fusion power. Practical fusion power remains elusive, but advances in creating self-sustaining fusion reactions and harnessing its power continue to occur.
In the early morning hours of Aug.13, Lawrence Livermore's National Ignition Facility (NIF) focused all 192 of its ultra-powerful laser beams on a tiny deuterium-tritium filled capsule. In the nanoseconds that followed, the capsule imploded and released a neutron yield of nearly 3x1015, or approximately 8,000 joules of neutron energy -- approximately three times NIF's previous neutron yield record for cryogenic implosions.
The primary mission of NIF is to provide experimental insight and data for the National Nuclear Security Administration's science-based stockpile stewardship program. The experiment attained conditions not observed since the days of underground nuclear weapons testing and represents an important milestone in the continuing demonstration that the stockpile can be kept safe, secure and reliable without a return to testing.
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This newest accomplishment provides an important benchmark for the program's computer simulation tools, and represents a step along the "path forward" for ignition delivered by the NNSA to Congress in December 2012.
Early calculations show that fusion reactions in the hot plasma started to self-heat the burning core and enhanced the yield by nearly 50 percent, pushing close to the margins of alpha burn, where the fusion reactions dominate the process.
"The yield was significantly greater than the energy deposited in the hot spot by the implosion," said Ed Moses, principle associate director for NIF and Photon Science. "This represents an important advance in establishing a self-sustaining burning target, the next critical step on the path to fusion ignition on NIF."
The experiment was designed to resist breakup of the high velocity imploding ablator (shell of the target capsule) that has degraded the performance of previous experiments by lowering compression of the target. To create this resistance, the laser power is turned up during the picket that occurs at the beginning of the laser pulse. This raises the radiation temperature in the foot or trough period of the pulse (hence the name "high-foot" pulse), increasing the stability of the ablator but sacrificing the ability to compress later in the implosion.
By. Roger Greenway