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The all-metal [[TJ-II:Sectors|vacuum vessel]] of TJ-II has a helical geometry and has 96 [[TJ-II:Ports|ports]]. | The all-metal [[TJ-II:Sectors|vacuum vessel]] of TJ-II has a helical geometry and has 96 [[TJ-II:Ports|ports]]. | ||
The vacuum vessel is made of non-magnetic steel (304 LN) with a thickness of 10 mm. | The vacuum vessel is made of non-magnetic steel (304 LN) with a thickness of 10 mm. | ||
The octants with flanges have been manufactured separately and were assembled in-situ by welding. This assembly was done directly around the central conductor CC/HX, already placed in position. The CC/HX coil is outside of the vaccuum vessel thanks to a helical groove built into the vessel. This groove has a wall thickness of 7 mm for clearance reasons. | The octants with flanges have been manufactured separately and were assembled in-situ by welding. This assembly was done directly around the central conductor CC/HX, already placed in position. The CC/HX coil is outside of the vaccuum vessel thanks to a helical groove built into the vessel. This groove has a wall thickness of 7 mm for clearance reasons. | ||
Its groove is protected along the entire toroidal circumference against damage due to the bean-shaped plasma by 3 mm stainless steel sheets for low and medium power operation and graphite tiles for high power operation. Furthermore, the vacuum vessel is protected on the areas where the neutral beams deposit a residual shine-through heat flux. The vacuum vessel will be pumped through four symmetrically spaced bottom ports to a base pressure of 10<sup>-8</sup> mbar. Four identical and independent vacuum pumping subsystems will be used. | |||
<ref>[http://dx.doi.org/10.1109/FUSION.1993.518387 J. Botija et al, '' Vacuum vessel, wall protection, pumping system and poloidallimiters of the Spanish stellarator TJ-II'', 15<sup>th</sup> IEEE/NPSS Symposium on Fusion Engineering '''1''' (1993) 529-532]</ref> | |||
=== Coil system === | === Coil system === |