It has been shown that the core energy confinement in tokamaks can be
significantly improved by modifying the plasma current profile. Plasma
regimes where the transport is reduced to its neoclassical value in t
he centre of the plasma within a region called the internal transport,
barrier (ITB) can be achieved with a zero or negative magnetic shear.
In this paper the role of the radio frequency (RF) methods: electron
cyclotron resonance, ion cyclotron resonance and lower hybrid current
drive in producing these ITBs is reviewed. Combined techniques where R
F waves are used to modify the magnetic shear together with a central
heating method (neutral beam injection or RF) are described. Applicati
on of RF methods to high fusion yield plasmas in JET with modified she
ar are presented together with a discussion on the prospects of achiev
ing steady-state high-performance plasmas. RF techniques are already p
laying an important role in these 'advanced scenarios' and are likely
to become indispensable tools for future steady-state tokamak reactors
.