Scientists from the Lawrence Livermore National Laboratory (LLNL) have announced a breakthrough in nuclear fusion technology. In the latest round of experiments, the LLNL scientists have succeeded in achieving fuel gains greater than "unity."
The ultimate goal in nuclear fusion is to achieve ignition, which simply means that the amount of energy released via fusion is greater than or equal to the amount of energy expended to confine fusion reaction. Before achieving ignition, however, scientists first need to achieve a fuel gain that is greater than "unity." To achieve this, the nuclear fusion reaction must generate enough energy to exceed the amount of energy that is deposited into the fuel used in the reaction.
The LLNL scientists working at the National Ignition Facility (NIF) have recently succeeded in conducting a nuclear fusion experiment where the fuel gains were greater than 1. This achievement is considered to be the first of its kind. The NIF scientists published their findings in the online journal Nature.
"Ignition is needed to make fusion energy a viable alternative energy source, but has yet to be achieved," said the scientists who authored the paper. "A key step on the way to ignition is to have the energy generated through fusion reactions in an inertially confined fusion plasma exceed the amount of energy deposited into the deuterium-tritium fusion fuel and hotspot during the implosion process, resulting in a fuel gain greater than unity."
While physicists working on the problem of nuclear fusion have yet to achieve ignition, the recent results published by the LLNL team is a significant milestone in the road to creating a practical fusion reactor.
"What's really exciting is that we are seeing a steadily increasing contribution to the yield coming from the boot-strapping process we call alpha-particle self-heating as we push the implosion a little harder each time," said LLNL scientist Omar Hurricane, the lead author in the study.
To jumpstart the fusion reaction, the LLNL scientists used 192 lasers aimed at a small capsule holding the deuterium and tritium needed to fuel the reaction. Deuterium and tritium are two stable isotopes of hydrogen. Once heated by the multiple laser beams hitting the fuel capsule, the nuclei of the deuterium and tritium atoms fuse. A neutron and an "alpha particle" are produced in the process and energy is released.
"There is more work to do and physics problems that need to be addressed before we get to the end," said Hurricane, "but our team is working to address all the challenges, and that's what a scientific team thrives on."