Introduction to the structure of the electron microscope
Electron microscope consists of three parts: lens barrel, vacuum system and power supply cabinet. The lens barrel mainly includes electron guns, electron lenses, sample holders, fluorescent screens, and camera mechanisms. These components are usually assembled into a column from top to bottom; the vacuum system is composed of mechanical vacuum pumps, diffusion pumps, and vacuum valves. The gas pipeline is connected with the lens barrel, and the power cabinet is composed of a high-voltage generator, an excitation current stabilizer and various adjustment control units.
◆Electronic lens
The electron lens is the most important part of the electron microscope lens barrel. It uses a space electric field or magnetic field symmetrical to the axis of the lens barrel to bend the electron track to the axis to form a focus. Its function is similar to that of a glass convex lens to focus the beam, so it is called electron. lens. Most modern electron microscopes use electromagnetic lenses, which focus electrons through a strong magnetic field generated by a very stable DC excitation current passing through a coil with pole shoes.
◆Electron gun
The electron gun is a component consisting of a tungsten filament hot cathode, a grid and a cathode. It can emit and form an electron beam with a uniform speed, so the stability of the accelerating voltage is required to be no less than one ten-thousandth.
