A krytron is a four element (cathode, grid, anode, and keep alive) gas filled cold cathode switching tube. Example: KN22.
The control grid in these devices actually encloses the anode with a small opening at the top. Conduction occurs through this hole. The gas in the tube provides ions to neutralise the space charge allowing a high current to be obtained at a lower voltage than otherwise possible.
Krytrons contain a small amount of radioactive Ni-63 which is a beta emitter. This aids the initial glow discharge between the cathode and the keep alive electrode.
This file was last modified
15:19:36, Tuesday September 02, 2014