If the glass is exposed by fast electrons the ionized alkali cations can be
released from their original sites and are driven by the electric field de
eper inside to the glass. The decay curves were measured and two migration
regimes have been revealed for alkali ions in the glass. The first regime,
the incubation period, is characterised by the individual ion migration, an
d by the linear-like decay in the decay curve. If the number of released al
kali ions achieves the percolation point the first regime bursts into the r
egime of spontaneous,migration that is characterised by the cooperative tra
nsport of alkalis and by the rapid exponential decay in the decay curve.