Several kinds of tungsten thermonic cathode were introduced.Moreover, the advances in the cathode with a monoatomic layer on the molybdenum substrate were reviewed.
Brazing quality and product reliability are both increased as using high frequency pulse microplasma arc heating process for assembly brazing of cathode and photoetching grid of electron tube.
In 1904, English physicist John Ambrose Fleming developed a new electrical component called a thermionic valve, which housed two electrodes inside an airtight glass bulb - this was the first vacuum tube.