The flexible Heliac TJII is the result of calculations performed by the team of physicists ane engineers of CIEMAT, in collaboration with the laboratory ORNL at oak Ridge (USA) and IPP at Garching (Germany). The TJII project received preferential support from Euratom on 1986 during phase I (Physics) and during 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. 60 % of the investments reverted back to Spanish companies.

In TJII, 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 meand 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. In order to heat the plasma of TJII, the following heating systems will be used: microwave heating at the electron cyclotron frequency (ECH, 400 kW) will be used, as well as the injection of beams of neutral hydrogen (NBI, up to 4 MW). The TJII discharges will last 0.5 s and will occur every 5 minutes. The control systems and the system of data acquisition were designed end developed by the CIEMAT. The objective of the experimental program of TJII is to investigate the physics of a device with a helical magnetic axis and with a great flexibility in its magnetic configurations. Physics problems of magnetically confined plasmas will be studied that are of much interest to the fusion community.