Electron microscopes generate images by bombarding samples with electrons and then converting the results of this interaction into visual images. In order to form an image, the generated electrons need to be tightly controlled.
Electron beams come from filaments made of various materials. The most common is the tungsten hairpin gun, which is widely used in scanning electron microscopes, transmission electron microscopes, and microprobe systems. This filament is a tungsten ring that acts as a cathode. Apply voltage to the loop to heat it up. The anode, which is positive relative to the filament, forms a strong attraction to electrons. This causes electrons to be accelerated towards the anode. Some accelerate near the anode and down the column to the sample.
Tungsten wire, also known as cathode or electron emitter or electron source, is mainly made of high-quality tungsten. Of all pure metals, tungsten has the highest melting point (3422°C), the lowest vapor pressure at temperatures above 1650°C, and the highest tensile strength. Tungsten also has the lowest coefficient of thermal expansion of all pure metals. This combination of properties makes tungsten an ideal material.
Since the electrons emitted in the various types of guns are heated, their energy distribution is not a spike. Instead, they have a Boltzmann distribution that can vary widely depending on the type of filament. For a good microscope, you want ΔE/E to be as small as possible. Therefore, the filament type needs to be selected according to its own applicable needs.
Chinatungsten Online/CTIA GROUP is a professional tungsten manufacturer. The high-quality filaments we offer are manufactured to OEM specifications using special tools to guarantee the correct shape of the filament and produce the best possible electron beam. We can provide tungsten filaments and crucibles for electron beam systems.
