Laboratorio Nacional de Fusion

The TJII Project: Heating systems

Stage I: ECH system
  • consisting of 2 gyrotrons working at second harmonic 53.2 GHz
  • injected power <= 1 MW.

Stage II: Neutral Beam Injection system

  • two co/counter NBI lines
  • injected power <= 3 MW.

Stage III: Consists of 3 MW additional power.

The choice of heating method is left open depending on results of Stage II and experience in other stellarators.


Stage I: ECH

Girotron GSM-4.

During this phase the expected plasma parameters are in the range:

ne(0) ~ 1.7 x 1019 m-3, Te (0) ~ 1.0 - 1.5 keV, Ti (0) ~ 300 eV, tauE ~ 4 ms.

Two quasioptical transmission line QTL1, and QTL2 have been designed to get maximum flexibility in ECRH and current drive experiments. The lines are located at two toroidal symmetric positions, launching microwaves through side windows B3 and A6, from the low field side. In both cases the microwave power is launched on movable mirror located inside the vacuum vessel, which focuses the beam on the resonant magnetic surface. Each mirror can rotate from -10° to 10° in the toroidal direction and from 21° to 35° in the poloidal direction.

Stage II: NBI system consisting of two co/counter NBI lines.


Web page of NBI Control

Accel Voltage 40 kV
Accel Current 100 A
Decel Voltage 1.5 kV
Decel Current 10 A
Arc Voltage 170 V
Arc Current 1200 - 1400 A
Pulse Width 300 ms
Gas Throughput 22 Torr.l/sec

The expected plasma parameters are in the range: ne (0) ~ 1020 m-3, beta(0) ~ 3 %, tauE ~ 6 ms.

Two neutral beam injectors formerly op-erational at the Advanced Toroidal Facility experiment in the Fusion Laboratory of ORNL will be redeployed at CIEMAT, for its use on TJ-II. The suitability of the ATF injectors on TJ-II has been established by extended studies, ranging from theoretical calculations of plasma heating and transport in order to ascertain the energy and power of the beams, to numerical calculations of beam transport and thermal loads onto TJ-II walls and drift duct, and optimization of the extraction-acceleration system.

Stage III:

The experimental goal will be to push the device towards its beta limit. The possibility to access second stability regimes will be also considered.