The process of ignition has been considered the "holy grail" of inertial confinement fusion science; for the first time ever researchers have reached" fuel gains" greater than 1.
Ignition is "the process of releasing fusion energy equal to or greater than the amount of energy used to confine the fuel," a Lawrence Livermore National Laboratory news release reported. In order to complete this process there must be fuel gains greater than unity, which occurs when the "energy generated through fusion reactions exceeds the amount of energy deposited into the fusion fuel."
"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," lead author Omar Hurricane said in the news release.
"Boot strapping" occurs when alpha particles ("helium nuclei produced in the deuterium-tritium fusion process") don't escape but rather deposit their energy in the deuterium-tritium (DT) fuel.
These alpha particles create more of themselves by heating the fuel; this process leads to ignition. The researchers demonstrated the boot-strapping process in a number of experiments in which the fusion yield was "systematically increased by more than a factor of 10 over previous approaches," the news release reported.
The process is designed to prevent a breakup of plastic in the shell that confines the DT fuel as it compresses. It is believed this breakup has caused fuel yield degradation in the past.
The team modified the laser pulse that compresses the fuel and found the breakup was suppressed. "The higher yields that were obtained affirmed the hypothesis, and demonstrated the onset of boot-strapping," the news release reported.
"There is more work to do and physics problems that need to be addressed before we get to the end," Hurricane said, "but our team is working to address all the challenges, and that's what a scientific team thrives on."
