Impact of beam ions on α-particle measurements by collective Thomson scattering in ITER

摘要

Collective Thomson scattering (CTS) has been proposed as a viable diagnostic for characterizing fusion born α-distributions in ITER. However, the velocities of the planned 1 MeV deuterium heating beam ions in ITER are similar to that of fusion born α-particles and may therefore mask the measurements of the fusion products. We apply a new technique for calculating the orbit averaged source, , of beam ions for various ITER scenarios. With the known Fokker-Planck modelling is applied to characterize the beam ions during the slowing down process. Theoretical CTS signals for both beam ions and the α-particles are calculated. Our investigations show that the CTS measurements of α-particles will not be masked by the presence of the beam ions in H-mode plasmas. In lower density reversed shear plasmas, only a part of the CTS α-particle spectrum will be perturbed.