electronics The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons using electronic devices. Electronics uses active devices to control electron flow by amplification ...

, a micropup is a style of triode

vacuum tube A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied. The type known as ...

(valve) developed during World War II for use at very high frequencies such as those used in

radar Radar is a detection system that uses radio waves to determine the distance ('' ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, we ...

. They are characterized by an external

anode An anode is an electrode of a polarized electrical device through which conventional current enters the device. This contrasts with a cathode, an electrode of the device through which conventional current leaves the device. A common mnemonic ...

block, which allows better heat dissipation. These tubes could deliver radio frequency power on the order of kilowatts at wavelengths as short as 25 cm, and on the order of 100 kW at 200 MHz in pulses. Micropup tubes used very high voltages to minimize the transit time of electrons between anode and cathode. The micropup vacuum tube was made possible by the development of vacuum-tight joining of copper to glass, around 1939. The designs used a cylindrical anode and a concentric cylindrical grid electrode; the cathode was directly heated thoriated tungsten wires, which after the first types were all oxide coated to improve electron emission. One type, the NT99 developed by GEC could produce up to 200 kW peak output (for a pair of tubes) when used in 600 MHz radar sets. A 50 cm radar set using micropup triodes was used by HMS Suffolk to track movements of the Bismarck. Although widely used in "metre-band" radar systems, the

cavity magnetron The cavity magnetron is a high-power vacuum tube used in early radar systems and currently in microwave ovens and linear particle accelerators. It generates microwaves using the interaction of a stream of electrons with a magnetic field whi ...

was able to produce significant power at much higher frequencies, as radar systems developed during the war.F.A. Kingsley (ed.), ''The Development of Radar Equipments for the Royal Navy, 1935–45'' Springer, 2016, , pages 110–111

References

Vacuum tubes Radar {{electronics-stub