Tokamak TJ-I

TJ-I Folleto

TJ-I tokamak. First magnetical confinement device operated in Spain.

The TJ-I tokamak was the first magnetic confinement device at CIEMAT (then JEN). Its name is an abbreviation for ‘Tokamak de la Junta’ (de Energía Nuclear, i.e., JEN) number I. It started operation in 1983, and has been operational until 1995. Ohmic heating was used.

This device has been the subject of many research programmes dedicated to the study of physical processes in tokamak plasmas:

  • basic confinement studies (transport, electric fields, isotope effect)
  • edge physics
  • turbulence studies (driving mechanisms, turbulent transport)
  • plasma-wall interaction (carbonization, boronization)
  • diagnostic development (microwave reflectometry, radiation detectors, probes, atomic beams,…)

TJ-I Parameters:
Major radius,  R0 = 0.30 m
Minur radius, a = 0.10 m
Plasma current, Ip = 30 kA
Toroidal magnetic field, BT = 1.0 – 1.4 T
Electron density, ne = 1.3*1013 cm-3


TJ-IU helocoidal field coil (yellow) and plasma (purple)

TJ-IU torsatron

The second magnetic confinement device operated at Ciemat is the torsatron TJ-IU, and it was designed and built by Ciemat scientists and engineers. In this device, a single coil generates the helicoidal magnetic field (l = 1) where the number of coil turns around the vacuum chamber is six (m = 6). Finally, a set of vertical field coils generates the vertical magnetic field.

The name ‘TJ-IU’ was given to this machine as it was considered an upgrade (‘U’) of the TJ-I device, in the sense that much of its auxiliary equipment was recycled from the TJ-I. Moreover, the main device components were fabricated in CIEMAT workshops: vacuum chamber, coil winding, etc. In 1999, the TJ-IU was transferred to Kiel, Germany where it was renamed the TJ-K, and later in 2005 it was moved to the IGVP institute in Stuttgart, Germany. In its reincarnation as TJ-K, the device is operated with a low magnetic field (about 0.07 T) and low heating powers (1-6 kW of ECRH heating). As a result the main plasma parameters are as follows (electron density: 0.5 × 1019 m-3; electron temperature: 10 eV; ion temperature: 1 eV).

TJ-IU Parameters:

TJ-IU vacuum chamber fabricated at CIEMAT workshops

Major Radius,  R0 = 0.60 m
Main plasma radius, a = 0.10 m
Minor coils radius Coils,  R0 = 0.24 m
Number of periods, m = 6
Rotational transform on axis, I0 = 0.30
Magnetic well depth = 6.9%
Magnetic ripple on axis = 7.6 %
Magnetic shear = almost zero
Helical axis elongation = 0.025 m
Toroidal magnetic field at φ=30º  BT = 0.5 T
2nd Harmonic Electron Cyclotron Heating, 28 – 37.5 GH, 200kW
Electron density, ne = 0.5*1013 cm-3


TJ-IU team (1997)