Figure 2-4B.Electron gun with buncher grids.
The manner in which the buncher produces bunches of electrons is better understood by considering
the motions of individual electrons, as illustrated in figure 2-5A.
When the voltage across the grids is negative, as shown in figure 2-5B, electron 1 crossing the gap at
that time is slowed. Figure 2-5C shows the potential across the gap at 0 volts; electron 2 is not affected.
Electron 3 enters the gap (figure 2-5D) when the voltage across the gap is positive and its velocity is
increased. The combined effect is shown in figure 2-5E. All of the electrons in the group have been
bunched closer together.
Figure 2-5A.Buncher cavity action. BUNCHER CAVITY.
Figure 2-5B.Buncher cavity action. ELECTRON #1 DECELERATED.