TJ-II:Construction: Difference between revisions

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=== Vacuum vessel ===
=== Vacuum vessel ===
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:Vacuum system|TJ-II vacuum vessel]] 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 vacuum 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 vacuum vessel thanks to a helical groove built into the vessel.
The 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 is pumped through four symmetrically spaced bottom ports to a base pressure of 10<sup>-8</sup> mbar. Four identical and independent vacuum pumping subsystems are used.
<ref>[http://dx.doi.org/10.1109/FUSION.1993.518387 J. Botija et al, '' Vacuum vessel, wall protection, pumping system and poloidal limiters of the Spanish stellarator TJ-II'',  15<sup>th</sup> IEEE/NPSS Symposium on Fusion Engineering '''1''' (1993) 529-532]</ref>
<ref>[http://dx.doi.org/10.1016/0042-207X(94)90022-1 F. Tabarés, ''The vacuum system of the TJ-II stellarator'', Vacuum '''45''', Issues 10-11 (1994) 1059-1061]</ref>


=== Coil system ===
=== Coil system ===