Detection of alpha heating in JET-ILW DT plasmas by a study of the electron temperature response to ICRH modulation

In the JET DTE2 campaign a new method was successfully tested to detect the heating of bulk electrons by α-particles, using the dynamic response of the electron temperature T_e to the modulation of ion cyclotron resonance heating (ICRH). A fundamental deuterium (D) ICRH scheme was applied to a tritium-rich hybrid plasma with D-neutral beam injection (NBI). The modulation of the ion temperature T_i and of the ICRH accelerated deuterons leads to modulated α-heating with a large delay with respect to other modulated electron heating terms. A significant phase delay of ∼40° is measured between central T_e and T_i, which can only be explained by α-particle heating. Integrated modelling using different models for ICRH absorption and ICRH/NBI interaction reproduces the effect qualitatively. Best agreement with experiment is obtained with the European Transport Solver/Heating and Current Drive workflow.