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NIF(National Ignition Facility at the Lawrence Livermore National Laboratory in California) uses the ICF (inertial confinement fusion) approach in order to harvest fusion energy.

At NIF, indirect drive laser ICF uses a "hohlraum" which is irradiated with a laser beam to bathe a peppercorn - sized fusion capsule inside with smooth high intensity X-rays. The capsule contains hydrogen fuel (actually its isotopes, deuterium and tritium), and when compressed, it creates a hot, dense ball 1/60000 th its original volume. Inside this tiny sphere, a cascade of fusion reactions would release many times more energy than the laser delivered. The newly formed helium would not be able to escape easily, and the heat generated from these extra collisions would encourage more hydrogen to fuse. Fusion would briefly become self-sustained leading to a huge jump in the energy produced (at least in principle).

The problem is maintaining the symmetry of the implosion. Once the capsule begins to collapse, instead of remaining spherical, as the simulations predicted, the capsule warps into an amorphous blob. Little bumps emerge on its surface, and these imperfections grow exponentially. The highest energy output achieved (according to a report in December 2012) was at most a third of the amount needed to trigger the helium collisions that would ignite the fuel.

A possible solution. Instead of using plastic coated fuel capsules, why not use capsules made of deuterium saturated palladium? The crystal structure of the hydrogen palladium system would represent a multitude of deuterium microcapsules embedded in the crustal structure of palladium. At implosion, the Coulomb repulsion would be easily overcome, due to the imploding crystal structure of the palladium. Not to be discouraged here that deuterium saturated palladium was considered by Pons and Fleischmann in their cold fusion experiments, proved to be misleading (in their case, fusion was not a factor). It has nothing to do with that , but the deuterium saturated palladium capsules could be feasible for ICF.

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  • $\begingroup$ Bremsstrahlung. Once you ionize the palladium and it's all a ball of plasma, it will lose all the energy trough radiation. The crystal structure won't matter, because there won't be a crystal. The whole point of the hohlraum is to keep the radiation in, which can only be done with very clean plasmas. $\endgroup$ – CuriousOne Jan 4 '15 at 18:54
  • $\begingroup$ Plus you will be wasting energy compressing the palladium and heating it, rather than the stuff you want to. $\endgroup$ – Jon Custer Jan 4 '15 at 22:15
  • $\begingroup$ Out of curiosity, why palladium? In any case, as both CuriousOne and Jon pointed out, the palladium would evaporate and ionize under such conditions, destroying its intended purpose of keeping the pressure spherically symmetric (I assume that was what you intended in your question). $\endgroup$ – honeste_vivere Jan 5 '15 at 20:00
  • $\begingroup$ You are talking about the evaporation and ionization of the outer layers of the material, with the formation of a plasma crown. This expands and generates an inward moving compression front which heats the inner layers of the material. The period of time during which thermonuclear reactions occur is limited by the inertia of the fuel. During the acceleration phase of the implosion, the contact between the high density of the shell material and the low density of the expanding fluid can bring Rayleigh - Taylor instabilities, and the fuel can pass through the shell material and tear it. $\endgroup$ – Cristian Dumitrescu Jan 11 '15 at 19:13
  • $\begingroup$ That is why homogeneous illumination is necessary. The target wall consists of multiple layers of materials with a range of atomic numbers, in order to ensure high efficiency combustion and optimization of energy coupling conversion. The density gradient in the system plays a major role in the dynamics. The inward moving compression front which heats the inner layers will interact with the crystal structure of the palladium capsule. I don't know if deuterium - tritium saturated palladium capsules represent the right answer. $\endgroup$ – Cristian Dumitrescu Jan 11 '15 at 19:17

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