Extension of the energy range of the moveable fast ion probe on TFTR

The range of detectable energies of the moveable fast ion probe on TFTR has been extended by the removal of a 3‐μm Al foil across its entrance aperture. This foil formerly stopped hydrogenic ions with energies below 300 keV, and helium ions with energies below 900 keV. The new arrangement allows detection of neutral beam ions (100‐keV D+) at toroidal fields between 1 and 5 T. Data typical of the probe’s enhanced performance are shown.