The latest price of φ0.8mm EB tungsten filament is USD 2.00/PC, EXW XIAMEN, CHINA on Dec. 8, 2022.
Tungsten filaments, also called cathodes or electron emitters or electron sources, are 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.
Tungsten can be used in both thermionic electron guns and field-emission (CFE) electron guns. 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.
An electron gun works at a high temperature, which is required for thermionic emission. For this, a filament or the cathode should be of a material that has a high melting point in order for it to continuously emit electrons. Tungsten filament is folded with various shapes to help in focusing the electron beam.
没有评论:
发表评论