TJ-II:Vacuum system

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An octant of the TJ-II vacuum vessel with its many ports. On the right, part of the groove is visible.
Interior view of the TJ-II vacuum vessel during assembly. The helical coil, fitting in the groove, is visible on the left.

Vacuum vessel

The all-metal TJ-II vacuum vessel has a helical geometry and has 96 ports. [1] [2] The vacuum vessel is made of non-magnetic steel (304 LN) with a thickness of 10 mm. 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 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.

Vacuum system

The vacuum vessel is pumped through four symmetrically spaced bottom ports to a base pressure of 10-8 mbar. Four identical and independent vacuum pumping subsystems are used. [3] [4] [5]

See also

A computer model of the TJ-II vacuum vessel. It can be seen how the plasma hugs the groove of the vessel.


  1. M. Baldarelli, A, Cecchini, M, Cucchiaro, et al., Vacuum vessel design for the TJ-II Heliac, Proc. 16th Symposium on Fusion Technology, London, U.K., 3–7 September 1990, 453
  2. J. Botija and M. Blaumoser, Vacuum vessel design for the TJ-II device, 14th IEEE/NPSS Symposium on Fusion Engineering 2 (1991) 992-995
  3. J. Botija et al, Vacuum vessel, wall protection, pumping system and poloidal limiters of the Spanish stellarator TJ-II, 15th IEEE/NPSS Symposium on Fusion Engineering 1 (1993) 529-532
  4. F. Tabarés, The vacuum system of the TJ-II stellarator, Vacuum 45, Issues 10-11 (1994) 1059-1061
  5. R. Carrasco, Hybrid baking system for the vacuum vessel of the Spanish stellarator TJ-II, Proc. 18th Symposium on Fusion Engineering (1999) 231-234