Propagation and stability of ion cyclotron modes in a deuterium-hydrogen-oxygen fusion plasma

The stability of ion cyclotron modes, propagating nearly perpendicular to the ambient magnetic field, has been considered in a mirror confined fusion plasma that has deuterium as the majority species, hydrogen as the minority species and multiply ionised oxygen as the impurity consituent. Two modes can exist in the plasma : one with a frequency slightly higher (the HF mode) than the deuterium gyro-frequency ΩD and the other with a frequency slightly lower (the LF mode) than ΩD. These modes have a wavelength larger than the ion gyro-radius rLD (that is ksub(perpendicular)rLD<1), the plasma itself being characterised by large ion plasma frequencies (ωpD2>>ΩD2). The necessary condition for an instability is that the loss-cone index j≥3. It is found that the growth rate is largest in a two-ion plasma and the wavelength region of instability, however, decreases with increasing charge on the oxygen ion. (author). 12 refs