Vircator
A vircator is a special electron tube for generating short, very powerful microwave pulses . The designation is a case word for English VIRtual CAthode oscillaTOR , dt. About virtual cathode oscillator . The area of application of a vircator is primarily the electronic warfare in the area of electronic countermeasures (ECM) around electronic devices by means of intense microwave impulses in the form of an electromagnetic pulse (EMP) such as disrupting radar systems or radio systems or making them permanently inoperable.
construction
As shown in the simplified figure on the right, a vircator consists of an evacuated tube, which is a cavity resonator in shape and geometry . On the left is a massive, unheated cathode and in the middle an anode made of thin metal grids . When a high-voltage pulse is applied, obtained from a pulse generator such as the Blumlein generator or the Marx generator , electrons are emitted from the cathode and accelerated towards the anode. Due to the design of the anode as a thin metal grid and the high intensity of the electron flow, a large part of the electrons fly past the anode and form a space charge cloud , also known as a virtual cathode , in the space behind the anode . With correspondingly high currents and the choice of the mechanical geometry of the cavity resonator, the movement of the charge carriers in this space charge cloud results in the formation of an electromagnetic wave which is decoupled from the resonator and passed on in a targeted manner by means of a connected waveguide and emitted as an intense shock wave via an antenna construction .
The peak power emitted by a vircator is a few 100 kW up to around 40 GW , depending on the tube type . The short-term DC voltage pulse applied to the tube differs depending on the type of tube and reaches several 100 kV, with currents of several kA flowing. The pulse duration is a few 100 ns up to a few µs. The maximum of the emitted frequency depends on the geometry of the cavity resonator as well as the distance between cathode and anode and is 1… 10 GHz.
In principle, a vircator can also be used several times, as is customary in setups in the test laboratory - when primarily used as a weapon system, however, usually only one pulse can be emitted, as the devices are destroyed due to the high load.
In the case of military use, the vircator must be brought close to the object to be affected, such as a radar or radio system, since the range of the interference pulse is limited to a few 100 m to a few km.
In the case of guided missiles as carriers, it is necessary to generate the electrical impulse in the missile. For this purpose, a flux compression generator is used, for example , which can emit a single pulse in a narrow space by compressing a magnetic field by detonating explosives. The energy comes from the detonation. The electrical energy of the flux compression generator for the vircator is adapted by a coupling network or pulse shaping network so that a microwave pulse (EMP) can be emitted to the environment for a period of a few 100 ns to a few microseconds. As a result of the detonation of the flux compression generator, the guided missile and the vircator are destroyed after the interference pulse has been emitted.
Web links
- Vircator. IEEE Global History Network, accessed March 6, 2015 .
Individual evidence
- ^ A b Libor Dražan, Roman Vrána: Axial Vircator for Electronic Warfare Applications. Department of Radar, Univerzita obrany, accessed March 6, 2015 .
- ↑ LL Altgilbers, MDJ Brown, I. Grishnaev, BM Novac, IR Smith, Y. Tkach, I. Tkach: Magnetocumulative Generators (= Shock Wave and High Pressure Phenomena ). Springer-Verlag, 2000, ISBN 978-0-387-98786-6 , doi : 10.1007 / 978-1-4612-1232-4 .