Kraytron - gas-filled lamp with a cold cathode, used as a very fast key (switch)

KN2 "Krytron" key manufactured by EG & G - approximately 25 mm high

Chraytron is a cold cathode gas filled lamp, used as a very fast key (switch). One of the early developments of the company EG & G Corporation.

Unlike most other gas-discharge devices, kraytrony use an arc discharge to control very large currents and voltages (several kV and a few kA per pulse), much more than the usual low-current glow discharge. The Kraytron is a combination of controlled spark gaps and thyratrons, originally developed for radar transmitters during World War II.

Device

Kraytron scheme.

The Kraytron has 4 electrodes: an anode, cathode, grid and “pre-ignition” (“Keep-alive” in the figure). The pre-ignition electrode is located near the cathode; A small positive voltage is applied to it so that the gas region near the cathode is ionized. High switching voltage is applied to the anode, but the discharge does not occur until a positive pulse is applied to the grid (“Grid” in the figure). Once started, the arc discharge creates a significant current between the cathode and the anode. Instead of or in addition to the pre-ignition electrode to facilitate ionization, some kraytrons may contain a small amount of β ⁺ radioactive material (usually nickel-63). The kraytron radioactivity is very small and not dangerous to health.

Kraytron, which was developed in the second half of the 1940s, still has better impulse characteristics than a modern semiconductor device for a number of parameters. And the vacuum type of the device ( en: Sprytron (Eng.)) Works even with a high level of radiation, at which the gas-filled Karatron could spontaneously turn on, and semiconductor devices generally do not work properly.

Application

Kraytrony and their modifications are still manufactured by Perkin-Elmer Components and used in a variety of industrial and military devices. It is best known to use them to control detonators in nuclear weapons (en: exploding-bridgewire detonator and en: slapper detonator, this is their initial use) directly or under the control of powerful spark gaps. They are also used to turn on high-power xenon lamps in copiers, lasers, and to control electrical detonators in industrial pyrotechnics.

Export Restrictions in the USA

Due to the possibility of using kraytronov in the control schemes for the detonation of nuclear weapons, export restrictions were introduced, their export from the United States is strictly controlled. There have been cases of smuggling or attempts to smuggle Kraytrons into countries developing nuclear weapons and looking for sources of Kraytron supply to control the weapons they produce.

In popular culture

Kraytron and the hunt for him appear in the 1988 film by Polanski “Frantic” (“Frantic”).