[en] About 1.5 x 10¹² positive ions are predicted to be required to disrupt the focusing (for 0.25 cm radius and 0.2 electric neutralization fraction). Beam electron collisions are predicted to produce this number in 20 ns with 6 x 10¹⁵ water molecules/cm². Electron avalanching is predicted to be intense at time zero in a gas layer about 10^-3 cm thick with 1.4 x 10¹⁶ cm^-2. With increasing time, space charge reduces the E-field and so the avalanching decreases. With 0.25 cm radius, 1.9 x 10¹¹ are predicted in 0.6 ns and with 1 cm radius, 7.4 x 10¹¹ are predicted in 1.5 ns