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National Ignition Facility Fires 192-Beam Pulse
An anonymous reader writes "The construction and test firing of the National Ignition Facility have been completed. NIF was designed as the first facility ever to achieve self-sustaining nuclear fusion and, in particular, to reach the point of ignition in which more energy is generated from the reaction than went into creating it. While the recent 192-beam pulse only produced 80 kilojoules worth of energy, all signs point to NIF being able to reach an order of magnitude higher (PDF) than that in the coming year."
Nope. It's pure science. They have no other goals except "study the ignition of nuclear fusion". It's a bit hard to do that inside a nuclear reactor (or bomb) and thus the big freakin' lasers.
How we know is more important than what we know.
That's the problem with magnetically confined fusion. NIF will be inertially confined.
I did my BSc thesis on the laser plasma interaction in NIF and my impression was that while inertial confinement fusion is extremely unlikely to be practical as a power plant, it may be used as an exceptionally intense neutron source for various experiments. Spallation sources can generally achieve high neutron fluxes and neutron energies, but an inertial confinement fusion device would generate orders of magnitude higher neutron intensities still. Moreover the fusion neutrons are virtually mono energetic, and this is impossible to achieve with most present spallation designs without drastically reducing the number of available neutrons. Essentially the only way to do it is to use some criteria like time-of-flight or neutron diffraction to select for only neutrons of a given energy, thus wasting all other neutrons, and this is only practical at low energies. At higher energies you would likely need to exploit the kinematics of some form of knockout reaction, like Li(D,n)Be, and since the large yield requirement would likely cause you to ionize your target, such a scheme would have challenges similar to those faced by inertial confinement devices. It also seems to me that it would be tricky to generate such a powerful deuterium pulse, if it is at all possible.
Inertial confinement fusion does not rely on having a stable plasma for any extended period of time as magnetic confinement does. Instead, think of it as a series of small bombs. Each is fired into the center of the chamber and ignited with the laser system. In a commercial plant this would have occur 5-8 times a second. Meaning you have what is essentially machine gun speed firing of DT pellets into the center of the chamber with equavalent speed lasers. Thus one of the large problems remaining in ICF fusion is the development of the laser components that can fire in this way for extended periods of time. Additionally, first wall materials are needed that can handle the neutron and ion flux that is generated in extended operation. The major US project that was actually addressing the laser and material tech side was HAPL, which got zeroed out on the FY 2009 budget.