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

[1] D. Tafalla and F.L. Tabarés, Journal of Nuclear Materials 290-293 (2001) 1195-1198

[2] D. Tafalla and F.L. Tabarés, Vacuum 64, Issues 3-4 (2002) 411-415

[3] F.L. Tabarés et al, Journal of Nuclear Materials 290-293 (2001) 748-752

[4] F.L. Tabarés et al, Plasma Phys. Control. Fusion 43 (2001) 1023-1037

[5] D. Tafalla and F.L. Tabarés, Vacuum 67, Issues 3-4 (2002) 393-397

[6] F.L. Tabarés at al, Plasma Phys. Control. Fusion 50 (2008) 124051

[7] J. Sánchez et al, Journal of Nuclear Materials 390-391 (2009) 852-857

[1]

[2]

[3]

[4]

[5]

[6]

[7]