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

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

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