TJ-II:Plasma Wall Interaction

To condition the wall of the TJ-II vacuum vessel, a number of techniques is used, such as a baking system. [1]

Glow Discharge Cleaning

Glow discharge cleaning is routinely used at TJ-II. [2] [3]

Limiters

TJ-II is fitted with two mobile limiters. Nevertheless, the main interaction between the plasma and the wall occurs at the central "groove". [4]

Wall conditioning

 
TJ-II retractable Lithium evaporation oven in action

Careful control of wall conditions is essential for successful operation. [5]

The walls can be coated by various materials, using a set of 4 evaporation ovens: two fixed and two mounted on retractable manipulators. In the course of time, TJ-II has been operated with the following types of wall:

  • Metal wall [6]
  • Boron-coated wall [7] (starting 2002)
  • Lithium-coated wall [8] [9] (starting 2007)

TJ-II was the first stellarator to be operated with Lithium-coated walls. The lithium coating has led to much improved density control.

References