We discuss MHD stability of the plasma in the completely axisymmetric end s
ystem of AMBAL-M and suggest a physical model to interpret the experimental
results. Measurement of the radial plasma pressure profile in the semicusp
using a local magnetic probe allowed estimation of the stability safety fa
ctor of the end system plasma which occurred to be greater than 3 divided b
y 4. Gas puffing into the semicusp increases the plasma pressure in this re
gion and hence enhances stability. To explain the observed MI-ID stability
of the end mirror plasma when the MI-ID stabilizer - semicusp was switched
off and the average field line curvature was unfavorable, a model was propo
sed which assumes that the plasma at the periphery had an electric contact
with a limiter. As a result, the potential of flute perturbations vanishes
at the plasma periphery. In this case finite Larmor radius effects may stab
ilize the most dangerous first (global) azimuthal mode because of nonlinear
dependence of plasma perturbations on radius.