Within the final focusing lens there are also two additional pairs of electro-magnet coils. Current is pulsed through these coils to produce oscillating magnetic fields that scan the beam across the experimental sample.
Some of the high-energy incoming electrons bounce back out of the sample ("backscattered electrons"). They also knock large numbers of electrons out of the sample ("secondary electrons"). Both streams are shown in pink. Off to the side, electrons from the sample are counted by two detectors.
