Technological waves and future perspectives of vacuum electronics

Vacuum electronics (VE) have been one of the motors of industrial growth in the last 130 years. The development of VE concepts has been pushed by several technological waves/cycles, starting with incandescent lamps, continuing with the radio tube era then followed by the cathode ray tubes. Before and during these cycles also the enabling technologies for VE, especially vacuum technology and cathode technology, have been developed further improved continously. Despite the decay of the first 3 waves, vacuum electronics is still alive in the form of microwave tubes, X-ray tubes and other applications. In the case of microwave tubes their specific advantages in the high power/high frequency domain over solid state is discussed. This could open new perspectives for future applications in IC design. In this talk first the different technological waves are described and then the progress of the two main enabling technologies is elucidated, monitored by decreasing vacuum base pressure and increasing cathode emission capabilities. Finally future perspectives for VE are given.