Flute instability and the associated radial transport in the tandem mirror with a divertor mirror cell

The flute instability and the associated radial transport are investigated in the tandem mirror with a divertor mirror cell (the GAMMA10 A-divertor) with help of computer simulation, where GAMMA10 is introduced [ Inutake et al., Phys. Rev. Lett. 55, 939 (1985) ]. The basic equations used in the simulation were derived on the assumption of an axisymmetric magnetic field. So the high plasma pressure in a nonaxisymmetric minimum-B anchor mirror cell, which is important for the flute mode stability, is taken into account by redefining the specific volume of a magnetic field line. It is found that the flute modes are stabilized by the minimum-B magnetic field even with a divertor mirror although its stabilizing effects are weaker than that without the divertor mirror. The flute instability enhances the radial transport by intermittently repeating the growing up and down of the Fourier amplitude of the flute instability in time