AE stability of QPS configurations using a Landau closure model*

The aim of this study is to analyze the linear stability of Alfvén Eigenmodes (AE) in QPS device using the gyro-fluid code FAR3d. AE stability is calculated for different NBI operational regimes, EP β = [0.01 – 0.1] and EP energy T_f = [2 – 180] keV, for the toroidal mode families n=1 to 5 and helical families n=1,3,5 and 2,4,6 as well as for vacuum and finite β configurations. In both configurations the modes with the largest growth rate are triggered by EP with an energy around 30 keV, having n=5 the largest. The AE EP β threshold in the vacuum case is 0.01 and 0.02 in finite β case (except for T_f = 30 keV which EP β threshold is 0.01), showing an increase (decrease) of the AE frequency (GR) with the EP energy above 30 keV. Toroidal Alfvén Eigenmodes (TAEs) have the largest growth rate, unstable in the frequency range of 100 - 230 kHz for the finite β case and 50 - 220 kHz for the vacuum case, triggered plasma periphery (normalized minor radius = [0.7-0.9]). Also, TAE eigenfunctions become slender as the toroidal mode number increases. EPs with T_f > 90 keV trigger Elliptical AE (EAEs) andNoncircular AE (NAE) with a smaller growth rate regarding the TAEs. The helical couplings analyzed are not strong enough to destabilize Helical AE (HAE), only increasing the mode GR around 10 %.