Trigatron

A Trigatron is a triggerable spark gap, often designed as gas-filled electron tube for switching short high-voltage pulses of high performance. This very high voltages in the range of some 10 kV and pulse currents are switched by some 1 kA with larger tubes, which corresponds to pulse powers up to several megawatts and can not be achieved by electromechanical switches. The Trigatron was developed during World War II by the British: In radars DC voltage pulses were converted by means of a magnetron in high-frequency pulses. Another application is in the Marx generator. The Trigatron is still used today in the pulse electronics.

Construction

The Trigatron has three electrodes: two unheated, mushroom-shaped main electrodes as anode and cathode as well as an ignition electrode, which usually sits in a central bore of the anode. The distance between the two main electrodes is chosen so large that it just does not come to voltage breakdown. A small spark between the ignition electrode and the anode locally generated charge carriers by ionization and ultraviolet radiation to the cathode of photo- electrons, which leads directly to the ignition of an arc between the two main electrodes. The shutdown of the Trigatrons made ​​indirectly by a pulse -shaping passive network ensures that the holding current is below and the arc is extinguished.

Small to medium-sized tubes with different gases, such as a mixture of 93 % argon and 7 % oxygen, nitrogen, or sulfur hexafluoride ( SF6) filled, and are under a pressure of from 1 to about 3.5 bar. For high performance, the gas filling is replaced by electrically non-conductive liquids such as transformer oil, a form of the pure mineral oil. Early types of Trigatrons without gas exchange are designed for up to 10,000 switching cycles. There are also older tubes which are designed to only a few switching cycles. At the end of the lifetime incidence of these historical embodiments of the destruction of the glass bulb, which is why this is surrounded to catch the splitter with a fine-mesh net. In the usual today Trigatron a number of cycles over a million of the piston consists of a solid housing in accordance with the gas filling is replaced by a corresponding power supply terminals in operation, and bursting of the casing is structurally avoided.

A further development of Trigatrons, but with rectifying property and heated cathode represents the thyratron