Plasma blanket

In the plasma 8Q% of the energy produced by the D-T reactions is in the form of energetic NEUTRONS which escape across the magnetic field and are then trapped in a surrounding blanket which contains LITHIUM. 

Schematic of a fusion reactor, assuming a generally toroidal shape of the plasma and magnetic fusion. The principles emphasized are central hot core (red) at 100 million degrees, blanket and heat exchanger, shield, energy conversion, and the handling of D, T, and the "ash" He.

Chemical Vapor Deposition- Deposition of silicon oxide films is accomplished by CVD equipment. Either plasma CVD or ozone oxidation is used. Blanket tungsten films are also deposited by CVD equipment to create contact and via plugs. Polysilicon and silicon nitride films are deposited in hot-wall furnaces. TiN diffusion barrier films are deposited by either sputtering or CVD, the latter giving superior step coverage. 

The shielding blanket is composed of water-cooled steel modules, which are directly supported by the vacuum vessel and are effective in moderating the 14MeV neutrons, with a water-cooled copper mat bonded to the surface of the modules on the plasma side, and protected from interaction with the plasma by beryllium. Manufacturing considerations can be found elsewhere [48]. The first wall incorporates two start-up limiters located in two equatorial ports. With the aim to reduce cost and nuclear waste, the design includes a modular and separable first wall. This allows damaged or eroded blanket modules to be repaired inside the hot cell either by replacement of panels or by plasma spraying or other methods. 

One of the important materials problems in this design is the corrosion of metal alloys when Li-Pb is used as the breeder-moderator. The dual wall structure used in the Cauldron Blanket Module should apply equally well here, so that V can be used for the plasma first wall to provide structural strength with minimum activation. The choice of a material for the wall membrane in contact with liquid Li-Pb becomes difficult. Ti alloys cannot be used because of reaction with Pb. Pure iron and iron-rich alloys appear marginal because of a solubility of Fe in Pb of 10-5 atom fraction at 900 K (12). Use of Ni or Cr as alloying constituents in iron do not improve the situation, since Ni and Cr have solubilities in Pb of 0.03 and v 10" atom fraction at 900 K (13). The refractory metals Nb, Ta, Mo,... 

Liquid Metal Wall IGF reactors are distinct from other fusion reactors in that the lithium breeding blanket is in direct contact with the plasma exhaust. Thus, the solubility of hydrogen isotopes in the liquid metal will determine whether tritium must be recovered from either the liquid loop or the vacuum system, rather than both systems. 

One problem associated with the PCM scheme is that during application of a photoresist such as AZI350J onto a PMMA film, a thin layer of PMMA is redissolved and mixed with the photoresist so that a thin interfacial layer is formed that remains after development of the photoresist layer and inhibits proper exposure and development of the PMMA layer. Because the PMMA developer, such as chlorobenzene or toluene, used in the capped process is chosen to be a nonsolvent for the photoresist, such a solvent cannot remove the interfacial layer. Therefore, some process, like plasma treatment, is required to remove the interfacial layer prior to the blanket exposure of the bottom PMMA layer (83, 85). 

The metal-RIE process is used in the fabrication of Al interconnects on chips. In this process, a blanket thin film of Al (or Al alloys, like Al—Cu, Al—Si) is deposited and then etched in a reactive plasma (RIE) through a photoresist stencil. After RIE, a... 

The neutron carries much of the energy released by this reaction. The neutrons have no electric charge so they are not contained by the magnetic field. They must be captured in a blanket material. When the blanket material absorbs them, their energy is transformed into heat. The heat from the neutrons and the radiant energy emitted from the hot plasma and directly adsorbed by the walls of the reactor are the heat output of the fusion reactor. This heat can be used to produce steam for the generation of electric power by conventional steam turbines. 

After leaving the plasma, the neutrons interact with the reactor inner wall or the cooling materials behind it. The inner wall and the coolant are termed the blanket. When the neutrons react with the blanket, their energy is deposited as heat. The resulting heat is used in conventional steam generation to provide process heat for the generation of electricity. 

The essential detail in the dual damascene technique is outlined in Fig. 16.19. It begins with the deposition of a blanket Si02 ILD oxide by means of the plasma-enhanced chemical vapor deposition (PECVD) technique to the desired thickness for the via. Next, a dense thin film of SiN is deposited on the ILD oxide by means of the high-density chemical vapor deposition (HDPCVD) technique. 

T. Hino, Y. Hirohata, Y. Yamauchi, M. Hashiba, A. Kohyama, Y. Katoh, Y. Lee, T. Jinushi, M. Akiba, K. Nakamura, H. Yoshida, S. Sengoku, K. Tsuzuki, Y. Kusama, K. Yamaguchi, and T. Muroga, Plasma Material Interaction Studies on Low Activation Materials Used for Plasma Facing or Blanket Component, J. Nucl. Mater., 329-333, 673-77 (2004). 

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