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Concept
Nova (laser)
Résumé
Nova was a high-power laser built at the Lawrence Livermore National Laboratory (LLNL) in California, United States, in 1984 which conducted advanced inertial confinement fusion (ICF) experiments until its dismantling in 1999. Nova was the first ICF experiment built with the intention of reaching "ignition", a chain reaction of nuclear fusion that releases a large amount of energy. Although Nova failed in this goal, the data it generated clearly defined the problem as being mostly a result of Rayleigh–Taylor instability, leading to the design of the National Ignition Facility, Nova's successor. Nova also generated considerable amounts of data on high-density matter physics, regardless of the lack of ignition, which is useful both in fusion power and nuclear weapons research.
ICF mechanism
Inertial confinement fusion (ICF) devices use drivers to rapidly heat the outer layers of a target in order to compress it. The target is a small spherical pellet containing a few milligrams of fusion fuel, typically a mix of deuterium and tritium. The heat of the driving laser burns the surface of the pellet into a plasma, which explodes off the surface. The remaining portion of the target is driven inwards due to Newton's Third Law, eventually collapsing into a small point of very high density.
The rapid blowoff also creates a shock wave that travels towards the center of the compressed fuel. When it reaches the center of the fuel and meets the shock from the other side of the target, the energy in the shock wave further heats and compresses the tiny volume around it. If the temperature and density of that small spot can be raised high enough, fusion reactions in a small portion of the fuel will occur.
The fusion reactions release high-energy particles, some of which (primarily alpha particles) collide with the remaining high-density fuel around it and slow down. This heats the fuel, and can potentially cause that fuel to undergo fusion as well.
Source officielle
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