Application of the two-electron transfer reaction to helium ion density and energy distribution measurements in JT-60

The two-electron transfer reaction was applied to the detection of helium ions in the thermal and epithermal energy range in JT-60. Using this technique, the helium ion density and the energy distribution were determined. The ion density and energy distribution obtained were consistent with the results from other diagnostics and from theory. The potential of this technique for measurements of the helium ash density and the energy distribution in fusion plasmas has been demonstrated.