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]

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Wall conditioning

TJ-II retractable Lithium evaporation oven in action

Careful control of wall conditions is essential for successful operation. ^[2]

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 ^[3]
Boron-coated wall ^[4] (starting 2002)
Lithium-coated wall ^[5] ^[6] (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] R. Carrasco, Hybrid baking system for the vacuum vessel of the Spanish stellarator TJ-II, Proc. 18^th Symposium on Fusion Engineering (1999) 231-234

[2] F.L. Tabarés et al, Density control and plasma edge characterisation of ECRH heated plasmas in the TJ-II stellarator, Journal of Nuclear Materials 290-293 (2001) 748-752

[3] F.L. Tabarés et al, Edge characteristics and global confinement of electron cyclotron resonance heated plasmas in the TJ-II Stellarator, Plasma Phys. Control. Fusion 43 (2001) 1023-1037

[4] D. Tafalla and F.L. Tabarés, First boronization of the TJ-II stellarator, Vacuum 67, Issues 3-4 (2002) 393-397

[5] F.L. Tabarés at al, Plasma performance and confinement in the TJ-II stellarator with lithium-coated walls, Plasma Phys. Control. Fusion 50 (2008) 124051

[6] J. Sánchez et al, Impact of lithium-coated walls on plasma performance in the TJ-II stellarator, Journal of Nuclear Materials 390-391 (2009) 852-857

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