TJ-II:Plasma Wall Interaction: Difference between revisions

To condition the wall of the [[TJ-II]] [[TJ-II:Vacuum system|vacuum vessel]], a number of techniques is used,

<ref>R. Carrasco, '' Hybrid baking system for the vacuum vessel of the Spanish stellarator TJ-II'', [[doi:10.1109/FUSION.1999.849826|Proc. 18^th Symposium on Fusion Engineering (1999) 231-234]]</ref>  

<ref>D. Tafalla and F.L. Tabarés, ''Wall conditioning and density control in the TJ-II stellarator'', [[doi:10.1016/S0022-3115(00)00672-3|Journal of Nuclear Materials '''290-293''' (2001) 1195-1198]]</ref>

<ref>D. Tafalla and F.L. Tabarés, ''Wall conditioning of TJ-II stellarator by glow discharge'', [[doi:10.1016/S0042-207X(01)00301-3|Vacuum '''64''', Issues 3-4 (2002) 411-415]]</ref>

 

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

<ref>J. Botija et al, ''Vacuum vessel, wall protection, pumping system and poloidal limiters of the Spanish stellarator TJ-II'', [[doi:10.1109/FUSION.1993.518387|15^th IEEE/NPSS Symposium on Fusion Engineering, Vol. 1 (1993) 529-532]]</ref>

 

 

[[File:TJ-II_Lithium_oven.jpg|300px|thumb|right|TJ-II retractable Lithium evaporation oven in action]]

 

Careful control of wall conditions is essential for successful operation.

<ref>F.L. Tabarés et al, ''Density control and plasma edge characterisation of ECRH heated plasmas in the TJ-II stellarator'', [[doi:10.1016/S0022-3115(00)00490-6|Journal of Nuclear Materials '''290-293''' (2001) 748-752]]</ref>

 

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 <ref>F.L. Tabarés et al, ''Plasma–wall interaction in the Spanish stellarator TJ-II Diagnostics and first results'', [[doi:10.1016/S0022-3115(98)00861-7|Journal of Nuclear Materials '''266-269''' (1999) 1273-1278]]</ref> <ref>F.L. Tabarés et al, ''Edge characteristics and global confinement of electron cyclotron resonance heated plasmas in the TJ-II Stellarator'', [[doi:10.1088/0741-3335/43/8/302|Plasma Phys. Control. Fusion '''43''' (2001) 1023-1037  ]]</ref>

* Boron-coated wall <ref>D. Tafalla and F.L. Tabarés, ''First boronization of the TJ-II stellarator'', [[doi:10.1016/S0042-207X(02)00211-7|Vacuum '''67''', Issues 3-4 (2002) 393-397]]</ref> (starting 2002)

* Lithium-coated wall <ref>F.L. Tabarés at al, ''Plasma performance and confinement in the TJ-II stellarator with lithium-coated walls'', [[doi:10.1088/0741-3335/50/12/124051|Plasma Phys. Control. Fusion '''50''' (2008) 124051]]</ref> <ref>J. Sánchez et al, ''Impact of lithium-coated walls on plasma performance in the TJ-II stellarator'', [[doi:10.1016/j.jnucmat.2009.01.224|Journal of Nuclear Materials '''390-391''' (2009) 852-857]]</ref> <ref>J. Sánchez et al, ''Confinement transitions in TJ-II under Li-coated wall conditions'', [[doi:10.1088/0029-5515/49/10/104018|Nucl. Fusion '''49''' (2009) 104018]]</ref><ref>F.L. Tabarés, M. Ochando, D. Tafalla, F. Medina, K. McCarthy, J.M. Fontdecaba, M. Liniers, J. Guasp, E. Ascasíbar, T. Estrada, I. Pastor, TJ-II Team, ''Energy and Particle Balance Studies Under Full Boron and Lithium-Coated Walls in TJ-II'', [[doi:10.1002/ctpp.200900046|Contrib. Plasma Phys. '''50''', 6-7 (2010) 610–615]]</ref>(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.