Magnetic lens system
Within the column the electromagnetic lenses shape the electron beam, which travels in a spiral trajectory. Each lens is constructed of a coil of copper wire through which a current runs. There is a hole in the center through which the beam travels.
The inside of the column is maintained under vacuum so that the density of molecules which can interfere with the electron beam are minimised. To achieve this, a system of vacuum pumps are attached to the TEM column.