Energy measurement of fast ions trapped in the toroidal magnetic field ripple of Tore Supra during ICRF heating

Direct losses of ions trapped in the toroidal field ripple of Tore Supra were studied, using two techniques. The first (DRIPPLE I) correlates the ion loss current measured by an electric probe with the ion loss power measured by a calorimeter. As the calorimeter integrates over all particle energies and time, it yields only the averaged lost ion energy. The second technique (DRIPPLE II), still under development, uses a Faraday cup positioned and filtered so as to select ions by their Larmor radius. Preliminary results are useful but the currents measured are small (1-100 nA), and improvements in instrumentation are needed to take full advantage of the data. During ICRH (hydrogen minority regime, resonance on-axis), a direct correlation between the lost ion mean energy and the density of hydrogen (n(H)) is observed. The energy increases when the hydrogen minority density decreases. Moreover, the line integrated density and the lower hybrid (LH) heating also affect the fast ion losses.