TJ-II:Plasma Wall Interaction

To condition the wall of the TJ-II vacuum vessel, a number of techniques is used.

Glow Discharge Cleaning

Glow discharge cleaning is routinely used at TJ-II. [1] [2]

Limiters

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

Wall conditioning

 
TJ-II retractable Lithium evaporation oven in action

Careful control of wall conditions is essential for successful operation. [3]

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 [4]
  • Boron-coated wall [5] (starting 2002)
  • Lithium-coated wall [6] [7] (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