A graded-density shell facilitates inertial confinement fusion reactions
A graded-density shell facilitates inertial confinement fusion reactions lead image
Inertial confinement fusion, where a fusion core is subjected to extreme pressure and temperature to drive a sustained fusion reaction, is an exciting and promising field of research. The biggest challenge is to reach the ignition threshold, where the energy entering the core exceeds the energy leaving it due to fusion reactions, allowing for sustained fusion.
MacLaren et al. designed an approach to make reaching the ignition threshold easier, by introducing a high-density layer at the inner surface of the capsule. This capsule lowers the requirements for ignition and increases the duration of the reaction, which should substantially lower the energy requirements for ignition.
“When the rate of heating exceeds the characteristic rate of disassembly of the capsule, that’s when you’ve met the ignition condition,” said author Stephan A. MacLaren.
The researchers proposed a dense capsule, called a pushered single shell, made of a mix of two materials, such as molybdenum and beryllium. The design takes advantage of recent manufacturing advances to create a shell that has a mixed core while grading smoothly outward to pure beryllium at the outer edge.
The result is a reaction where the low-density beryllium in the outer shell ablates off and adds energy, while the high-density molybdenum core increases the confinement time. The smooth gradient of the pusher shell keeps the implosion stable, and the overall effect is to lower the temperature and pressure requirement to reach ignition.
“The next step is to execute a series of experiments that would lead up to an implosion that reaches this ignition threshold,” said MacLaren.
Source: “A pushered capsule implosion as an alternate approach to the ignition regime for inertial confinement fusion,” by S. A. MacLaren, D. D.-M Ho, O. A. Hurricane, E. L. Dewald, D. A. Martinez, R. E. Tipton, J. E. Pino, C. V. Young, H. W. Xu, C. W. Kong, and K. Sequoia, Physics of Plasmas (2021). The article can be accessed at https://doi.org/10.1063/5.0064971 .
