A thyratron is a type of gas filled tube used as a high energy electrical switch and controlled rectifier. A gas-filled tube, also known as a discharge tube, is an arrangement of Electrodes in a Gas within an insulating, temperature-resistant Envelope In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός A switch is a mechanical device used to connect and disconnect an electric Circuit at will A rectifier is an electrical device that converts Alternating current (AC to Direct current (DC a process known as rectification. Triode, Tetrode and Pentode variations of the thyratron have been manufactured in the past, though most are of the triode design. A triode is an electronic amplification device having three active electrodes A tetrode is an electronic device having four active Electrodes The term most commonly applies to a two-grid Vacuum tube. A pentode is an electronic device having five active Electrodes The term most commonly applies to a three-grid Vacuum tube, which was invented by the Dutchman Gases used include mercury vapor, xenon, neon, and (in special high-voltage applications or applications requiring very short switching times) hydrogen. Mercury (ˈmɜrkjʊri also called quicksilver or hydrargyrum, is a Chemical element with the symbol Hg ( Latinized hydrargyrum Xenon (ˈzɛnɒn or) is a Chemical element represented by the symbol Xe. Neon (ˈniːɒn is the Chemical element that has the symbol Ne and Atomic number 10 Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 ^[1] Unlike a vacuum tube, a thyratron cannot be used to amplify signals linearly. This article is about the electronic device not an evacuated pipe used for experiments in Free-fall. Generally an amplifier or simply amp, is any device that changes usually increases the amplitude of a signal.

Giant GE hydrogen thyratron, used in pulsed radars, next to miniature 2D21 thyratron used to trigger relays in jukeboxes

In the 1920s Thyratrons were derived from early vacuum tubes such as the UV-200, which contained a small amount of argon gas to increase its sensitivity as a radio signal detector; and the German LRS Relay tube, which also contained argon gas. Radar is a system that uses electromagnetic waves to identify the range altitude direction or speed of both moving and fixed objects such as Aircraft, ships A relay is an electrical Switch that opens and closes under the control of another Electrical circuit. jukebox is a partially automated music-playing device usually a Coin -operated machine that can play specially selected songs from self-contained media This article is about the electronic device not an evacuated pipe used for experiments in Free-fall. Radio is the transmission of signals by Modulation of electromagnetic waves with frequencies below those of visible Light. Gas rectifiers which predated vacuum tubes, such as the argon-filled General Electric "Tungar bulb" and the Cooper-Hewitt mercury pool rectifier, also provided an influence. A rectifier is an electrical device that converts Alternating current (AC to Direct current (DC a process known as rectification. A rectifier is an electrical device that converts Alternating current (AC to Direct current (DC a process known as rectification. Peter Cooper Hewitt ( May 5, 1861 - August 25, 1921) was an American electrical engineer who demonstrated the mercury-vapor lamp A mercury arc valve ( mercury vapor rectifier) is a type of electrical Rectifier which converts alternating current into Direct current. A thyratron is basically a "controlled gas rectifier". Irving Langmuir and G. Irving Langmuir ( January 31, 1881 in Brooklyn New York – August 16, 1957 in Woods Hole Massachusetts) was an S. Meikle of GE are usually cited as the first investigators to study controlled rectification in gas tubes, about 1914. The first commercial thyratrons didn't appear until around 1928.

Construction

A typical hot-cathode thyratron uses a heated filament cathode, completely contained within a shield assembly with a control grid on one open side, which faces the plate-shaped anode. An electrical filament is a thread of Metal, usually Tungsten, which is used to convert Electricity into light in Incandescent light bulbs (as developed A cathode is an Electrode through which (positive Electric current flows out of a polarized electrical device The control grid is an Electrode used in thermionic valves (vacuum tubes used to modulate the flow of electrons in the Cathode to Anode or An anode is an Electrode through which Electric current flows into a polarized electrical device When positive voltage is applied to the anode, if the control electrode is kept at cathode potential, no current flows. Electrical tension (or voltage after its SI unit, the Volt) is the difference of electrical potential between two points of an electrical When the control electrode is made slightly positive, gas between the anode and cathode ionizes and conducts current. The shield prevents ionized current paths that might form within other parts of the tube. The gas in a thyratron is typically at a fraction of the pressure of air at sea level; 15 to 30 millibars (1. 5 to 3 kPa) is typical.

Both hot- and cold-cathode versions are encountered. Hot cathode is also a name for a Hot filament ionization gauge, a vacuum measuring device A cold cathode is an element used within some Nixie tubes Gas discharge lamps Gas filled tubes and Vacuum tubes Cold cathodes do not A hot cathode is an advantage, as ionization of the gas is made easier; thus, the tube's control electrode is more sensitive. Once turned on, the thyratron will remain on (conducting) as long as there is a significant current flowing through it. When the anode voltage or current falls to zero, the device switches off.

Applications

Small thyratrons were manufactured in the past for controlling electromechanical relays and for industrial applications such as motor and arc-welding controllers. Large thyratrons are still manufactured, and are capable of operation up to tens of kiloamperes (kA) and tens of kilovolts (kV). The ampere, in practice often shortened to amp, (symbol A is a unit of Electric current, or amount of Electric charge per second The volt (symbol V) is the SI derived unit of electric Potential difference or Electromotive force.

Modern applications include pulse drivers for pulsed radar equipment, high-energy gas lasers, radiotherapy devices, particle accelerators and in Tesla coils and similar devices. Radar is a system that uses electromagnetic waves to identify the range altitude direction or speed of both moving and fixed objects such as Aircraft, ships A gas laser is a Laser in which an Electric current is discharged through a Gas to produce light Radiation therapy (or radiotherapy) is the medical use of Ionizing radiation as part of Cancer treatment to control Malignant A Tesla coil is a type of resonant transformer circuit invented by Serbian-American scientist Nikola Tesla around 1891 Thyratrons are also used in high-power UHF television transmitters, to protect inductive output tubes from internal shorts, by grounding the incoming high-voltage supply during the time it takes for a circuit breaker to open and reactive components to drain their stored charges. Television ( TV) is a widely used Telecommunication medium for sending ( Broadcasting) and receiving moving Images, either monochromatic For biologic transmitters see Transmitter substance. A transmitter is an electronic device which usually with the aid of an antenna The inductive output tube or IOT is a variety of Vacuum tube which evolved in the 1980s to meet increasing efficiency requirements for high-power RF Short Circuit is a 1986 comedy Science fiction film starring Ally Sheedy and Steve Guttenberg and directed by A circuit breaker is an automatically-operated electrical Switch designed to protect an electrical circuit from damage caused by overload or This is commonly called a "crowbar" circuit. A crowbar, active crowbar or crowbar circuit is an Electrical circuit used to prevent an overvoltage condition of a Power supply unit from damaging

Thyratrons have been replaced in most low and medium-power applications by corresponding semiconductor devices known as thyristors (sometimes called silicon-controlled rectifiers, or SCRs) and triacs. The thyristor is a solid-state Semiconductor device with four layers of alternating N and P-type material A silicon-controlled rectifier (or semiconductor-controlled rectifier) is a four-layer solid state device that controls current. A TRIAC, or TRIode for Alternating Current is an electronic component approximately equivalent to two Silicon-controlled rectifiers ( SCRs However, switching service requiring voltages above 20 kV and involving very short risetimes remains within the domain of the thyratron. Variations of the thyratron idea are the krytron, the sprytron, the ignitron, and the triggered spark gap, all still used today in special applications. The Krytron is a cold-cathode Gas filled tube intended for use as a very high-speed switch and was one of the earliest developments of the EG&G Corporation. The Krytron is a cold-cathode Gas filled tube intended for use as a very high-speed switch and was one of the earliest developments of the EG&G Corporation. An ignitron is a type of controlled Rectifier dating from the 1930s A spark gap consists of an arrangement of two conducting Electrodes separated by a gap usually filled with a Gas such as Air.

References

• Stokes, John, 70 Years of Radio Tubes and Valves, Vestal Press, NY, 1982, pp. 111-115.
• Thrower, Keith, History of the British Radio Valve to 1940, MMA International, 1982, p. 30, 31, 81.
• Hull, A. W. , "Gas-Filled Thermionic Valves", Trans. AIEE, 47, 1928, pp. 753-763.

1. ^ L. W. Turner,(ed), Electronics Engineer's Reference Book, 4th ed. Newnes-Butterworth, London 1976 ISBN 0 408 00168 2, pages 7-177 and 7-180

See also

• Ignitron
• Krytron
• Thyristor
• IGBT

External links

• tpub.com
• Detailed description of hydrogen Thyratrons (PDF document)
• Article about switch tubes by John Pasley
• Thyratron collection at the Virtual Valve Museum