Fusion boundary removal

There are various methods of assessing the state of fusion of PVC. Intact particle boundaries, coated with stabilisers, etc. are very weak. Consequently, immersing the PVC in a liquid such as methylene dichloride causes the particles to separate, giving rise to a white powdery surface (Fig. 6.20). The wall of the pipe has been chamfered to expose the different layers. Fusion is only complete at the inner and outer surfaces, that experienced the highest levels of shear in passing through the extrusion die. A pipe with this level of fusion would have inferior mechanical properties. The fusion of PVC particles is referred to as gelation. As PVC is mixed in an internal mixer, viscous dissipation causes a steady rise in temperature. Samples are removed at various... 

Almost all modern fusion devices rely on the divertor concept and all planned devices comprise a divertor. The divertor was initially a separate chamber to which the boundary plasma was diverted by additional divertor coils. In the divertor, the plasma is guided onto target plates. The dominant and most important process at the target plate is neutralization. The impinging plasma ions are neutralized and reemitted into the gas phase. Therefore, the neutral gas pressure in the divertor is substantially higher than in the main chamber. The pump ducts to the vacuum pumps are located underneath the divertor to pump the neutral gas. Naturally, the pumped gas is dominantly composed of fuel species, but in addition, the helium ash and other volatile impurities will be removed in this way. The pumped fuel will be recycled in the gas handling facility and pumped impurities will be permanently removed. The other important function of the divertor is to handle the arriving power flux. This will be discussed further below. 

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