Neutral beam heating data from JET have been analysed in detail to determine what proportion of the current is driven non-inductively. It is found that in low density limiter discharges, currents of the order of 0.5 MA are driven, while in H-mode plasmas currents of the order of 0.7 MA are measured. These measured currents are found to be in reasonable agreement with theoretical predictions based on neoclassical models. In low density plasmas the beam driven current is large while the neoclassical bootstrap current dominates H-mode plasmas.

On the assumption that the distribution function of ions heated by ion cyclotron resonance absorption is essentially isotropic, analytical and semi-analytical approximations are derived for the distribution function. The result is used to evaluate the weighted velocity space averages of the distribution, which determine the fusion reactivity and the collisional power transfer to plasma background particles, and to study their scaling with RF parameters such as absorbed power and perpendicular wave number. The importance of higher order finite Larmor radius effects on the formation of RF induced high energy tails is particularly emphasized. Comparisons based on full 2-D numerical calculations show good agreement with the semi-analytical results.

An investigation is made of the effect of tuning ICRF heating to neutral-beam-injected ions in a two-component plasma. The corresponding RF-induced velocity diffusion is found to cause a significant enhancement of the high-energy tail of the beam ions. This is also shown to give rise to a subsequent increase in the fusion power multiplication factor, indicating an efficient use of the available heating power.

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Alpha-particle losses due to pitch-angle scattering into the loss cone of an open-field-line configuration are investigated. Specifically, the particle loss and the corresponding energy loss are given as explicit functions of energy during slowing-down. It is found that the alpha-particle energy loss due to pitch-angle scattering for a pure DT-plasma is of the order of 5–10%, in contrast to the 35–40% obtained in a recent paper