ECRH power deposition studies in ASDEX Upgrade

In this paper the calculated ECRH power deposition profiles p ECRH (ρ) are compared with the experimentally derived ones in ASDEX Upgrade. ECRH power deposition is calculated by the beamtracing code and with its help the p ECRH (ρ) behaviour at different ECRH scenarios is investigated. Experimentally, power deposition can be obtained from electron temperature differences dT e after switching on/off ECRH or from the perturbed electron temperature e when modulated ECRH is applied. The complete experimental recovery of the p ECRH (ρ) requires the determination of its maximum, centre ρ 0 and width w 0 . The centre of the deposition ρ 0 is determined experimentally from the temperature response, from dT e after switching on/off ECRH or alternatively from e in modulated ECRH experiments. The measured width is broadened quickly by perpendicular heat transport, which makes the experimental determination of w 0 very difficult. A scheme in which off-axis cw ECRH is applied in order to reduce the transport in the core plasma, where the modulated ECRH is deposited, is used in the determination of w 0 . We estimate the ECRH deposition width w 0 in an indirect way, in which e (ρ) profiles determined experimentally from FFT are compared to those calculated with the transport code ASTRA. Finally, the total absorbed ECRH power is obtained experimentally by using a self-consistent power balance scheme.