Simulation studies on stability of EBT

Stability and beta limits of the ELMO Bumpy Torus (EBT) are studied by using a 2 1/2 -D fully relativistic, electromagnetic particle code. A slab model is used which is bounded in the x direction (corresponding to the radial direction) and which is periodic in the y direction (corresponding to the poloidal direction). The imposed magnetic field is in the z direction (the ignorable coordinate) and is a function of x so that the plasma flutes in the absence of an EBT ring. The hot electron ring (layer) is shown to be effective in suppressing the Rayleigh–Taylor instability, when kyρh ≳1, where ρh is the Larmor radius of hot electrons. However, in a system where kyρh <1 for long wavelength modes, the plasma exhibits instability. One possible mode which agrees fairly well with our observations is the low-frequency hot electron interchange instability.