Results achieved on JET during the 1997-1999 experimental campaigns in
the physics of energetic ions and runaway electrons are reviewed.
Heating of deuterium-tritium (DT) plasmas by fusion born alpha particles
is found to be similar to that achieved by comparable ICRF heating of
deuterium plasmas. The stability of alpha particle driven Alfvén
eigenmodes (AEs) in the highest fusion power ELM-free H mode discharges
is shown to be consistent with the existing theoretical analysis for
AEs. Direct measurements of the trapped alpha particle and knock-on
deuteron distribution functions by a neutral particle analyser (NPA) are
described. New ICRF heating scenarios tested in JET DT plasmas are
presented in view of the possible use of the ICRF heating of ITER-like
DT plasmas on route to ignition. The energetic ion pinch in the presence
of toroidally asymmetric ICRF waves is studied experimentally on JET.
Recent experimentally observed effects of ICRF accelerated ions on
sawteeth in JET are reviewed. Detailed time and space resolved X ray
images of the electron runaway beam in flight spontaneously generated by
disruptions on JET are described.