Investigation of impurity behaviour in three-ion ICRF scenarios in H-D and D-T plasmas at JET

Résumé fourni par la source

Abstract This study investigates impurity behaviour during ion cyclotron resonance heating (ICRF) experiments, focusing on the application of two different three-ion heating schemes in H-D and D-T plasmas at JET. In the D-(³He)-H scenario, the phasing of the ICRF antenna straps was varied to modify the launched parallel wave number k||, enabling a systematic study of its effect on fast-ion generation, plasma dynamics and impurity transport. The results indicate dependence of impurity behaviour on antenna phasing, particularly for the nickel (Ni) in the main plasmas and for the beryllium (Be) source. Analysis of sawtooth oscillations using the symmetrised dot pattern method reveals correlations between sawtooth frequency and crash intensity, the applied ICRF power and antenna phasing. The lowest impurity levels are obtained with +90° antenna phasing, corresponding to maximised fast-ion generation. A comparative study of impurity behaviour in D-T plasmas is also presented for the three-ion T-(⁹Be)-D and hydrogen minority heating scenarios. The three-ion scheme produces the largest increases in ion temperature Ti, while hydrogen minority heating yields higher electron temperatures Te and slightly reduced impurity levels. These results suggest that impurity behaviour in three-ion ICRF scenarios depends on the chosen heating optimisation (fast-ion generation versus ion heating) and can be further controlled through appropriate selection of ICRF antenna phasing.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.