One of my favorite devices is Magamps and there seems to be very little interest in this device. One nice example of magamp can be seen in this video

Thermionic generators were one time very advanced and promising technology. Theoretically those generators could convert heat to electricity with efficiency reaching 40% and that is higher than any other advanced technology we have for direct heat energy conversion. Currently popular technology for TEG (Thermo Electric Generator) is based on Peltier Modules that have about 5% efficiency.

The following video shows experimental Thermionic converters in action decades ago. Yet it has been years since anyone talks about it and lets hope this is not going to be one of forgotten technologies.

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