RF Waveguide Vacuum Valve

This device enables maintenance to be carried out on a Radio Frequency (RF) waveguide system while keeping, at the same time, part of it under vacuum.

In order to maintain one part of a RF system evacuated while doing installation and maintenance on the other part, dielectric windows are normally used. However, high-power RF can often breakdown this window, leading to loss of vacuum and increased maintenance costs overall.

The technology disclosed here is a valve which can create a vacuum on one side and atmospheric pressure on the other. When the valve is in the open position, RF transmission can take place across the gap with only minimal loss of power. When the valve is in the closed position, maintenance work can be carried out on the atmospheric pressure side, whilst retaining the vacuum on the other. This enables a flexible and reliable maintenance system — without significant loss of waveguide performance.

The RF waveguide vacuum valve was developed for CERN’s Compact Linear Collider test facility.

Advantages & Applications


  • The possibility to use a commercially available vacuum valve in waveguides where high-power – high-frequency is used.
  • Low loss.
  • There are no limitations on the frequency range of the technology. This technology can be used from the lowest frequencies under which vacuum waveguides are used up to quasi-optical transmission lines.
  • The technology can be a clean environmental friendly alternative to the use of SF6, a highly potent green house gas.


  • Waveguide systems - Medical and Industrial field and Scientific accelerator.
  • Satellite & Space Research - The technology may be used to evacuate RF satellite systems using vacuum, in space.



A 30 GHz dual-mode vacuum valve with an overall length of 100 mm and a diameter of the central waveguide section, that contains the TE01+TE02 mode mixture, of 30 mm the transmission measurements show losses of about -0.1dB. These losses consist of two contributions: diffraction losses of -0.033dB and ohmic losses of -0.049dB.

Innovative features

  • No surface electric field in the waveguide section because of TE0n mode conversion, which increases the potential of high power RF transmission because of low loss.
  • In closed position, a vacuum is maintained on one side and atmospheric pressure on the other.
  • In open position, it provides low-loss transmission of RF power.
The technology has been proven by simulations of different frequencies (from 3 to 30 GHz) and a prototype for 30 GHz has been built.
An international patent application is filed and the technology is ready for licensing.