6. Conclusion

This article gives an overview of the technologies used in electron tubes. It then explains how grid tubes work, and gives an overview of the intrinsic and practical performance and limitations of these devices. The glory days of grid tubes are largely behind us, but some very high-power applications require new developments and new products. The most emblematic of these are thermonuclear fusion (ICRH heating), a field with a very promising long-term future, and certain heavy-ion gas pedals needed by physicists studying the structure of atomic nuclei. The article concludes with an overview of IOT tubes, which combine the advantages (and also some limitations) of triodes and klystrons, to enable the realization of more linear amplifiers.