Krytron

The Krytron is a gas- filled electron tube that mid-20th century has been found as a switch tube application. The special design of very short switching times and high currents can be switched.

This tube development dates back to the late 1940s. Krytrons are a further triggerable spark gaps. They possess such as this one triggering electrode between cathode and anode and an auxiliary electrode near the cathode maintains a sustain discharge, causing a pre-ionization. Some of them include, in addition or alternatively to the auxiliary electrode a weak beta-emitters, usually with the isotope nickel Ni- 63, the pre-ionized gas filling.

Krytrons have cold cathodes, they differ from the cold cathode thyratron (relay tube ) by its shorter switching times and much higher currents, which is not a glow discharge, but a spark discharge effect like those.

Krytrons were in radar equipment, used to control flash lamps to ignite stronger spark gap, the ignition of conventional explosives and nuclear bombs by means of an exploding wire, and for other applications where sharp pulse currents and high voltages are required. They have been completely replaced in these applications by semiconductor switches.

The vacuum version of a Krytrons is the Sprytron. Another triggerable high power switch is the thyratron.