TJ-II
TJ-II is a flexible Heliac installed at Spain's National Fusion Laboratory. It is currently operational.
History
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 (ORNL, USA) and the Institut für PlasmaPhysik at Garching (IPP, Germany). The TJ-II project received preferential support from Euratom for phase I (Physics) in 1986 and for phase II (Engineering) in 1990. The 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.
Precedents
TJ-II is the third fusion 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 University of Stuttgart in Germany under the name of TJ-K.
Description
In TJ-II, the magnetic trap is obtained by means of various sets of coils that completely determine the magnetic surfaces before plasma initiation. The toroidal field is created by 32 coils. The tree-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 vacuum vessel wall.
TJ-II discharges last 0.5 s and have a repetition frequency of about 5 minutes.
Goals
The objective of the experimental program of TJ-II is to investigate the physics of a device with a helical magnetic axis with a great flexibility in its magnetic configurations.
Operation
The electric energy required for a TJ-II discharge is obtained from a flywheel generator. The coils are cooled by means of a cooling system.
Heating
In order to heat (and fuel) the TJ-II plasma, the following heating systems are used:
- Electron Cyclotron Resonant Heating (ECH, 2 injection beamlines, 600 kW)
- Neutral Beam Injection (NBI, two injectors, up to 4 MW).
Control and data acquisition
The control and data acquisition systems were designed end developed at CIEMAT.
Diagnostics
TJ-II is fitted with an extensive set of diagnostic systems: