2. Electronic tube technologies

All electron tubes are made up of universal building blocks: the cathode supplies the electrons, the electron optics accelerate and focus them, the interaction between the beam and the electromagnetic wave forces the electrons to give up a significant part of their energy to the RF signal (kinetic energy for linear 'O' tubes, potential energy for crossed-field 'M' tubes), the collector recovers them at the end of the path, and the vacuum envelope contains the whole assembly and ensures its cooling (figure 2 ). In some tubes (magnetrons, grating tubes), the anode of the electron optics and the collector are merged, and only the interaction between the beam and the electromagnetic wave is really specific to each family of devices.