Diacrode TH628

In the 90^th, to fulfill the new performance requirements in scientific and industrial area, Thales Electron Devices, the world leading company for UHF high power tetrodes, decided to invest in a high power bench (6 MW CW) and carried out tests on tetrodes in order to find their limits. We concluded from these tests, that RF losses inside the tetrodes, leads to over heat some part of the structure and consequently to a lack of reliability for high power, high frequency conditions (lot of trips off without destruction of the tube). No more than 300 kW at 200 MHz in steady and reliable CW operating conditions could be reached with the standard tetrode technology. To overcome this limitation and drastically reduce the RF losses on grids, Thales developed a double ended tetrode configuration so called diacrode, which is discussed in this paper.