Applications
Vacuum variable capacitors are commonly used in high voltage applications 5000 volts (5kV) and above. They are used in equipment such as high powered broadcast transmitters, Amateur radio RF Amplifiers and large Antenna tuners. Industrially they are used in plasma generating equipment, for dielectric heating, and in semiconductor manufacturing. The main applications today are RF plasmas of 2 to 160MHz where the vacuum capacitor is used as the impedance variation part in an automatic matching network.
Other variations of vacuum capacitors include fixed value capacitors. Fixed value capacitors are designed very much like the variable versions with the exception of an adjustment mechanism.
Read more about this topic: Vacuum Variable Capacitor