Fast-ion phase-space tomography with wave–particle interactions in the ion cyclotron frequency range as prior

The fast-ion distribution function in fusion plasmas can be inferred by inverting Doppler-shifted measurements from fast-ion diagnostics. The full fast-ion distribution function can be parametrised by three constants of motion with the addition of a binary index. However, with a limited number of measurements, cogent prior information must be added to regularise the inverse problem, enabling the reconstruction of the distribution function. In this paper, we demonstrate how to incorporate wave–particle interactions in the ion cyclotron range of frequencies (ICRFs) as prior information with the future ITER tokamak as a test case. We find that the addition of ICRF physics as prior information improves the reconstruction of a test ICRF-heated fast-ion distribution function in ITER using synthetic data based on the planned collective Thomson scattering sightlines and the planned gamma-ray spectroscopy sightlines. The addition of such prior information is beneficial in the case of a limited phase-space coverage of fast-ion diagnostics.