Scattering of ion cyclotron range of frequency (ICRF) waves by plasma density perturbations in the edge has been previously studied with the help of antenna code RAPLICASOL (2020, Nucl. Fusion, 60, 096001). The further interesting question is whether the density perturbations have an effect on ion cyclotron resonance heating (ICRH) in the core. In this paper, FEM based 2D full wave code integrating the core with edge is used to study this issue. The analytical density perturbations are applied to study the influence of density perturbations on field distribution, power deposition, waves coupling and power partition among different species in the core and the fraction of energy dissipation in SOL. The influence of density perturbations becomes global and significant when the poloidal size of the density blob is comparable to the perpendicular wavelength. In addition, the amplitude and the radial size of the density blob are positively related to the strength of waves scattering. Finally, a typical experiment on EAST is chosen and the influence of realistic density perturbations on ICRH is evaluated.

Off-axis current drive is necessary for Tokamak to maintain and regulate the current profile. Helicon wave is the high order harmonic fast wave and helicon wave current drive (HCD) is one of the key issues in the China Fusion Engineering Test Reactor (CFETR). The theory of HCD is briefly introduced and the simulation results are listed. Helicon waves can realize off-axis current drive under CFETR plasma parameters when the frequency is greater than 1 GHz and drive current is insensitive to the launched value of the parallel index of refraction n||, so wave accessibility issues can be reduced. Travelling Wave Antenna was analyzed by the commercial software package-CST. Near the resonant frequency of the antenna, the Voltage Standing Wave Ratio < 1.2 is obtained for the antenna in the bandwidth of 50 MHz, which means that the antenna does not require a matching system.

Recent studies have shown that helicon waves may be an attractive option for driving an efficient off-axis current drive in order to supplement bootstrap current for steady state operation in fusion reactors. Based on the China fusion engineering test reactor parameters, the helicon wave trajectories, profiles of driven current and current driven efficiency are calculated with the ray-tracing code GENRAY. Both the peak position and the peak value of driven current profiles are dependent on the wave frequency. In the frequency range of 1.6 GHz–2.0 GHz, the peak value increases with the increase of frequency, and the peak position has a slight change (concentrate around ρ= 0.75). High electron temperature and low electron density seem to be favorable for the helicon wave absorption. A driving current of I/P > 70 kA MW−1 at the off-axis position of ρ < 0.7 can be obtained with the electron temperature at the plasma center, T e(0) < 25.4 keV and the electron density at the plasma center, n e(0) ∼ 0.7 × 7.8 × 1019m−3–0.8 × 7.8 × 1019m−3. The current drive efficiency decreases with the increase of the electron density. Peak positon of the driven current profile is insensitive to the parallel refractive index n ∥. It is found that the poloidal launch angle has some effect on the peak positon and its value.

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