The basic principle behind ITER's most powerful heating system is relatively simple: fast (>10,000 km/s) hydrogen or deuterium atoms are injected through the tokamak magnetic field cage into the plasma, where they transfer their energy to the plasma particles through collision.
A beam of roughly 1 m x 1 m is extracted out of 640 apertures of the ELISE grid system (left). Three and a half metres later, it hits the diagnostic calorimeter which measures the 2D profile of the beam power (right).
In ITER, a stable power flux (i.e., a stable ion current from the source) lasting up to 1 hour is required. Sustaining the
Behaviour of the negative ion current (green symbols) during five plasma pulses of 1200 seconds each at ELISE. During each pulse a beam lasting 10 s is extracted every 3 minutes. After the first beam extraction of each pulse the negative ion current becomes stable and reproducible; the electron current (yellow symbols), on the other hand, tends to increase up to the limit of present power supply. The new power system will allow scientists at ELISE to continue along the path of demonstrating ITER source requirements.