TJ-II

2011-09-12T14:19:31Z

ALF: /* Simulation codes */

[[File:TJII_model.jpg|500px|thumb|right|TJ-II Model]]

TJ-II is a flexible Heliac installed at Spain's [[Laboratorio Nacional de Fusión|National Fusion Laboratory]].
It is one of Spain's [http://www.micinn.es/portal/site/MICINN/menuitem.6f2062042f6a5bc43b3f6810d14041a0/?vgnextoid=cb09846085f90210VgnVCM1000001034e20aRCRD Large Scientific Installations].
It is currently operational.

== History ==

[[File:Foto_grupo_Fusion_1996.jpg|300px|thumb|left|TJ-II and the TJ-II Team in 1996]]

The flexible Heliac TJ-II was designed on the basis of calculations performed by the team of physicists and engineers of [[CIEMAT]], in collaboration with the Oak Ridge National Laboratory ([http://en.wikipedia.org/wiki/ORNL ORNL], USA) and the Institut für PlasmaPhysik at Garching ([http://en.wikipedia.org/wiki/Max-Planck-Institut_f%C3%BCr_Plasmaphysik IPP], Germany).
<ref>[http://www.ornl.gov/info/reports/1987/3445602635147.pdf T.C. Hender et al, ''Studies of a flexible heliac configuration'', Report ORNL/TM-10374 (1987) OSTI ID: 6007697]</ref>
The TJ-II project received preferential support from [[Euratom]] for phase I (Physics) in 1986 and for phase II (Engineering) in 1990. The [[TJ-II:Construction|construction of this flexible Heliac]] was carried out in parts according to its constitutive elements, which were commissioned to various European companies, although 60% of the investments reverted back to Spanish companies.

The first plasma was produced in 1999.

== Precedents ==

TJ-II is the third magnetic confinement device in a series. In 1983, the device [[TJ-I]] was taken into operation.
The denomination of this device is due to the abbreviation of "Tokamak de la Junta de Energía Nuclear", this being the former denomination of [[CIEMAT]]. The abbreviation was maintained for successive devices for administrative reasons.

In 1994, the torsatron [[TJ-IU]] was taken into operation. This was the first magnetic confinement device entirely built in Spain. Currently, [[TJ-IU]] is located at the [http://www.ipf.uni-stuttgart.de/index_e.html University of Stuttgart] in Germany under the name of TJ-K.

== Description ==

[[File:TJ-II_3D_perspective.jpg|300px|thumb|right|TJ-II perspective view]]

In TJ-II, the magnetic trap is obtained by means of [[TJ-II:Coil system|various sets of coils]] that completely determine the magnetic surfaces before plasma initiation. The toroidal field is created by 32 coils. The three-dimensional twist of the central axis of the configuration is generated by means of two central coils: one circular and one helical. The horizontal position of the plasma is controlled by the vertical field coils. The combined action of these magnetic fields generate bean-shaped magnetic surfaces that guide the particles of the plasma so that they do not collide with the [[TJ-II:Vacuum system|vacuum vessel]] wall.

TJ-II discharges last around 0.25 s, with a repetition frequency of about 7 minutes.

== Goals and Research ==

The objective of the experimental program of TJ-II is to investigate the physics of a device with a helical magnetic axis having a great flexibility in its magnetic configuration, and to contribute to the international effort regarding the study of magnetic confinement devices for fusion.

Also refer to [[Plasma Physics at the LNF]].

== Operation ==

* A [[TJ-II:Vacuum system|vacuum system]] controls the pressure inside the vacuum vessel.
* The electric energy required for a TJ-II discharge is obtained from a [[TJ-II:Power supply|flywheel generator]].
* The [[TJ-II:Coil system|coils]] are cooled by means of a [[TJ-II:cooling system|cooling system]].
* An extensive set of systems is available to perform [[TJ-II:Plasma Wall Interaction|plasma wall conditioning]].
* Two movable [[TJ-II:Limiter|limiters]] can be used to limit the plasma.
* A [[TJ-II:Biasing probe|biasing probe]] can be used to apply a bias potential at the edge.
* A [[TJ-II:Paddle|mechanical paddle]] is used to suppress runaway electrons during current ramp-up and ramp-down.

== Heating and fuelling ==

In order to fuel and heat the TJ-II plasma, the following systems are used:
* [[TJ-II:Gas puff|Gas puff]]
* [[TJ-II:Electron Cyclotron Resonant Heating|Electron Cyclotron Resonant Heating]] (ECRH)
* [[TJ-II:Neutral Beam Injection|Neutral Beam Injection]] (NBI)
* [[TJ-II:Electron Bernstein Wave Heating|Electron Bernstein Wave Heating]] (EBWH)
* [[TJ-II:Pellet injector|Pellet injector]] (PI)

== Control and data acquisition ==

The [[TJ-II:Control and data acquisition systems|Control and data acquisition systems]] were designed end developed at CIEMAT.

== Diagnostics ==

[[File:TJ-II_top_view_2009.jpg|400px|thumb|right|TJ-II in 2009; front left: Thomson Scattering; left and bottom right: NBI; top: HIBP]]

TJ-II is fitted with an extensive set of diagnostic systems installed in its 96 access [[TJ-II:Ports|ports]]. For information on the magnetic coordinate system (required for cross-diagnostic comparisons), see [[TJ-II:Magnetic_coordinates|TJ-II magnetic coordinates]].

''Passive diagnostics''
* [[TJ-II:Magnetics|Magnetics]]
* [[TJ-II:Halpha monitors|Halpha monitors]]
* [[TJ-II:Electron Cyclotron Emission|Electron Cyclotron Emission]]
* [[TJ-II:Soft X-rays|Soft X-rays]]
* [[TJ-II:Multifilter electron temperature diagnostic|Multifilter electron temperature diagnostic]]
* [[TJ-II:Bolometry|Bolometry]]
* [[TJ-II:Spectroscopy|Spectroscopy]]
* [[TJ-II:Charge exchange spectroscopy|Charge exchange spectroscopy]]
* [[TJ-II:Compact Neutral Particle Analyzer|Compact Neutral Particle Analyzer]]
* [[TJ-II:Fast ion loss probe|Fast ion loss probe]]
* [[TJ-II:Fast camera|Fast camera]]

''Active diagnostics''
* [[TJ-II:Interferometry|Interferometry]]
* [[TJ-II:Reflectometry|Reflectometry]]
* [[TJ-II:Heavy Ion Beam Probe|Heavy Ion Beam Probe]]
* [[TJ-II:Langmuir Probes|Langmuir Probes]]
* [[TJ-II:Thomson Scattering|Thomson Scattering]]
* [[TJ-II:Diagnostic neutral beam|Diagnostic neutral beam]]
* [[TJ-II:Helium Beam|Helium Beam]]
* [[TJ-II:Lithium Beam|Lithium Beam]]

== Numerical resources ==

=== Simulation codes ===
* [[VMEC]] - 3D Plasma equilibrium, assuming nested flux surfaces
* [[PIES]] - 3D Plasma equilibrium
* [[HL]] - Field line following code
* [[ASTRA]] - Plasma transport
* [[PROCTR]] - Plasma transport
* [[EUTERPE]] - Gyrokinetic code
* [[EIRENE]] - A Monte Carlo neutral gas transport code
* [[FAFNER]]
* [[CUTIE]] - Full-tokamak fluid turbulence
* [[MOCA]] - Monte Carlo [[Neoclassical transport]] code
* [[TRECE]] - Microwave ray tracing
* [[TRUBA]]- Microwave beam/ray tracing including electron Bernstein wave calculations.

=== Data analysis ===
* [[Wave_ana]] - Linear and non-linear data analysis, spectral analysis using Fourier and Wavelets
* [[EBITA]] - Tomographic reconstruction
* [[TJ-II:Tomography|Tomography]] - Tomographic reconstruction based on mode decomposition in flux surface geometry

== References ==
<references />

TJ-II:Limiter

2011-09-12T14:10:48Z

ALF:

[[TJ-II]] has two mobile limiters, located in [[TJ-II:Sectors|sectors]] A3 and C3 (115.5º and 295.5º), with a toroidal separation of 180º.
<ref>[[doi:10.1016/S0022-3115(98)00829-0|E. de la Cal et al, ''The diagnosed mobile limiters of the TJ-II stellarator for plasma boundary studies'', J. Nucl. Mat. '''266-269''' (1999) 485]]</ref>
The limiters are fitted with Langmuir probes and gas injection ports.
<ref>[[doi:10.1016/S0022-3115(00)00525-0|E. de la Cal, B. Brañas, F.L. Tabarés, D. Tafalla, A.L. Fraguas, M.A. Pedrosa, V. Tribaldos, E. Ascasibar, J. Herranz, I. Pastor and TJ-II Team, ''Plasma boundary and SOL studies of ECH-plasmas in TJ-II stellarator with diagnosed mobile poloidal limiters'', Journal of Nuclear Materials, '''290-293''' (2001) 579-583]]</ref>
<ref>[[doi:10.1016/j.jnucmat.2004.07.055|I. García-Cortés et al, ''Fuelling efficiency of hydrocarbons in TJ-II plasmas'', J. Nucl. Mat. '''337-339''' (2005) 441-445]]</ref>
<ref>[[doi:10.1016/j.jnucmat.2007.01.061|E. de la Cal et al, ''Hydrogen recycling and puffing at a poloidal limiter of TJ-II'', J. Nucl. Mat. '''363-365''' (2007) 764-769]]</ref>
A biasing voltage can be applied.
<ref>[[doi:10.1088/0741-3335/46/1/018|C. Hidalgo et al, ''Improved confinement regimes induced by limiter biasing in the TJ-II stellarator'', Plasma Phys. Control. Fusion '''46''' (2004) 287-297]]</ref>

{| border="0"
|- valign="top"
| [[File:TJ-II_limiter.png|400px|thumb|right|TJ-II Limiter and plasma]]
| [[File:TJ-II_Limiter_photo.jpg|300px|thumb|left|TJ-II Limiter: photograph taken from [[TJ-II:Ports|port B8TANG]] (the location of the [[TJ-II:Fast camera|fast camera]])]]
|-
|}

== Liquid Lithium limiters ==

Currently (2010) a limiter upgrade is being prepared, consisting of liquid lithium limiters.
<ref>[http://www-pub.iaea.org/mtcd/meetings/PDFplus/2010/cn180/cn180_papers/ftp_p1-34.pdf A.V. Vertkov, I.E. Lyublinski, F. Tabares, E. Ascasibar, ''Development of Liquid Lithium Limiter for Stellarator TJ-II'', 23<sup>rd</sup> IAEA Fusion Energy Conference, Daejon, Korea (2010) FTP/P1-34]</ref>
<ref>[http://www-pub.iaea.org/mtcd/meetings/PDFplus/2010/cn180/cn180_papers/ftp_3-6rb.pdf I.E. Lyublinski, A.V. Vertkov, et al., ''Development and experimental study of Lithium based plasma facing elements for fusion reactor application'', 23<sup>rd</sup> IAEA Fusion Energy Conference, Daejon, Korea (2010) FTP/3-6Rb]</ref>

== References ==
<references />

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