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A thyratron is a early form of electronics component, and a variation on the vacuum tubes first used in early computers. Originally conceived in 1914 and put into commercial production in 1928, the thyratron is still in use. It is a form of high energy switch and also serves as a rectifier, capable of converting alternating current (AC) into direct current (DC). Unlike standard vacuum tubes, a thyratron is a gas-filled switch, usually containing an inert gas, such as mercury vapor, neon, or xenon gases.
The gas in a thyratron has positive ions that can carry electrical current, which makes the device capable of conducting much higher levels of current than a typical vacuum tube. It is not uncommon for one to be capable of conducting 10 – 20 kilovolts(kV) of power. Applications for such devices include use in Ultra-High Frequency (UHF) television transmitters, nuclear particle accelerators, high-energy laser systems, and radar equipment.
Several variations on the thyratron also exist. Krytons, which are also a form of gas-filled tube, differ by employing an arc discharge of electrical current instead of gas discharge, and were implemented in radar transmitters that were widely used during World War II. Thyristors are a more modern version and are a hybrid between thyratron and transistor designs. Based on standard semiconductor technology used to make microprocessors, the thyristor is employed in low- and medium-power environments to also convert AC to DC. These devices are used as switches to control motor speeds and chemical operations, such as pressure and temperature changes in equipment.
One of the areas where the thyratron is beginning to be phased out is in the arena of high-energy physics research. Their replacement is the insulated-gate bipolar transistor (IGBT), another solid state semiconductor switching device like the thyristor. The first versions of IGBTs were slow and prone to failure when they came on the market in the 1980s, but IGBTs have reached a third generation of design refinement. They now have higher pulse rates for switching and are more readily available than thyratrons. Uses for the IGBT are also being seen in such products as electric cars and audio amplifiers.
Operating life for the hydrogen-based thyratron is in the range of 1,200 hours, with other models lasting up to 20,000 hours, whereas a IGBT will last for around 250,000 hours. Energy consumption is also much higher with a thyratron as opposed to an IGBT. Due to import and export restrictions imposed by several nations and increasing difficulty in obtaining thyratrons, their cost per unit also tends to be significantly higher than using an IGBT for the same application.