Sodium and potassium silica glasses were irradiated with a 50 keV elec
tron beam and the migration of alkalis was studied on cross-sectioned
specimens. Alkaline ions moved from the grounded (i.e. electrically co
nnected with the ground) surface deeper into the sample even at low te
mperatures due to the electric field and at about half the electron ra
nge colloidal particles with a diameter in the range from 10 to 200 nm
were created. Near the surface alkali depleted layers with modified s
tructure were formed.