Experiments were conducted using a barium plasma in a simple axisymmetric mirror machine that was stabilized against the magnetic curvature‐driven interchange mode by surface line tying. Ion cyclotron resonance heating was applied to heat ions, producing a mirror‐trapped ion population. The ion‐velocity distribution function was diagnosed nonperturbatively by using laser‐induced fluorescence techniques. The rf heated distribution was a non‐Maxwellian infI(v⊥), and a sloshing distribution infI(v∥). When the plasma source was cut off, the plasma decay was studied to determine the confinement properties of the plasma afterglow and the effects of the stabilizing blanket. Mirror‐trapped ions were lost axially at the classical ion–ion collision rate. Analysis of the temporal evolution of radial profiles of ion‐energy density, in the afterglow, indicates that axial loss rates dominanted over radial losses.