Essential components of all SEMs include the following:
Electron Source ("Gun")
Electron Lenses
Sample Stage
Detectors for all signals of interest
Display / Data output devices
Infrastructure Requirements:
Power Supply
Vacuum System
Cooling system
Vibration-free floor
Room free of ambient magnetic and electric fields
SEMs always have at least one detector (usually a secondary electron detector), and most have additional detectors. The specific capabilities of a particular instrument are critically dependent on which detectors it accommodates.