evacuation system

The evacuation system of a TEM is composed of the electron gun chamber, the column, the specimen chamber and the camera chamber, and various pumps, valves, and exhaust tubes. In the normal TEM, the electron gun chamber and the column are evacuated by the (oil) rotary pump-the (oil) diffusion pump-the ion pump system, whereas the camera chamber is evacuated by the (oil) rotary pump-the (oil) diffusion pump system. When the electron gun is of the field-emission type, an independent ion pump is used for the electron gun chamber to obtain a high vacuum. Recently, due to increasing requirements for oil-free evacuation system, a system using scroll pump-turbo molecular pump is becoming popular for the evacuation of the camera chamber and the column.