Neutral particle analyser (NPA) measurements of emitted hydrogen flux, integrated along a chord through the plasma centre, have been used to infer a perpendicular tail temperature T⊥ of minority ion cyclotron range of frequencies (ICRF) heated protons in the Joint European Torus (JET). A relation is established between T⊥ and the perpendicular proton temperature T⊥(0) at the position of maximum power deposition. At energies E >> T⊥(0), the value of T⊥ inferred from the NPA is nearly equal to T⊥(0). In the opposite limit E << T⊥(0), it is shown that T⊥ << T⊥(0). Applying this model to NPA measurements from a JET pulse with varying ICRF power PRF, it is found that the scaling of T⊥(0) with PRF in the 2 to 10 MW range is almost linear, as expected. Moreover, calculated values of the ICRF heated proton energy content, based on deduced values of T⊥(0), agree with diamagnetic measurements. The NPA measurements thus give access to a fundamental property of the heated proton energy distribution, which plays a crucial role in sawtooth stabilization
Third harmonic ICRF heating in LHD hydrogen experiments