A kind of hot-cathode tube that is so highly exhausted that the residual gas plays no part in the production of the cathode stream, and that is regulated by variable heating of the cathode filament.
Wm. D. Coolidge, in 1913, ingeniously crafted a cutting-edge x-ray tube known as the hot cathode variant. This remarkable invention housed a filament that emanated fervent electrons, alongside a formidable tungsten target anode, all encapsulated within a vacuum-sealed glass envelope. It is worth noting that the fundamental tenets of this tube’s construction reverberate through the contemporary x-ray tubes of today.