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Thyratrons


By Radu Motisan Posted on March 17th, 2011 , 12518 Views (Rate 11.06)



A thyratron is a type of gas filled tube used as a high energy electrical switch and controlled rectifier. Triode, tetrode and pentode variations of the thyratron have been manufactured in the past, though most are of the triode design. Because of the gas fill, thyratrons can handle much greater currents than similar hard vacuum valves/tubes since the positive ions carry considerable current. Gases used include mercury vapor, xenon, neon, and (in special high-voltage applications or applications requiring very short switching times) hydrogen.[1] Unlike a vacuum tube, a thyratron cannot be used to amplify signals linearly. Source Wiki.

The movie shows 3 of my thyratrons, while being energized. The 714 (Mercury Vapor and Gas), the 309CE/FG-17 and the 3C31/ELC1B. Here are the datasheets:
714_7021
309CE/FG17
3C31/ELC1B-A
The first two contain mercury. If stored or unused for a long period, the mercury can deposit on the internal walls and components. Extra care must be taken when warming such a tube, to avoid short circuits inside it. Also it is a must to first power the filament and then apply the switching voltage .

The thyratron is a gas-filled discharge chamber that contains a cathode filament, an anode plate, and one or more grids. An inert gas or metal vapour fills the discharge chamber. The grid controls only the starting of a current and thus provides a trigger effect. The normal grid potential is negative with respect to the cathode and prevents electrons from flowing to the plate and exciting a discharge. To cause a discharge, the grid potential is raised enough to start electrons flowing from the cathode. As free electrons stream toward the plate, they collide with gas molecules, freeing other electrons and ionizing the gas within the discharge chamber. When a sufficient number of ions and electrons are present, a “short” occurs, and a large current flows from the cathode to the plate, causing a discharge. The discharge can take place in a few hundred-millionths of a second. The discharge stops when the anode voltage has been sufficiently lowered. The grid can be used to initiate a discharge but can't be used to terminate one. After a discharge, a thyratron has a deionization time, needed for the ions to revert back to the neutral state. While ionized the Thyratron is conductive, so it will trigger even without a grid potential. For Mercury vapor thyratrons, this time is around 1mili-second, and for hydrogen thyratrons this gets a lot lower. Only by removing the plate potential or reducing it to the point where the electrons do not have enough energy to produce ionization will tube conduction and the production of positive ions stop. Only after the production of positive ions is stopped will the grid be able to regain control.

Thyratron tubes are used typically in radar pulse modulators, particle accelerators, lasers, and high-voltage medical equipment.

Here is a Radar Modulator schematic, using a Hydrogen Thyratron:

More details available here.



It is also possible to use a Thyratron as an oscillator in a Tesla Coil:

This is only a test Thyratron Tesla coil device and needs further improvements. I used the following:
- high voltage DC supply (using a 100W flyback transformer, and a Royer push and pull oscillator), providing 8KV 10mA.
- rewound mot supply , for tube filament
- a ferrite choke for charging the PFN
- a pulse forming network, as presented here.
- a hydrogen thyratron, TGI2 400/16
- a 200V pulse generator, more details here.
The oscillator itself is described here.

Here is another Tesla coil switched by a Thyratron, actually this is the first design I've ever seen on the Internet. Mine would be the second :)

Construction details (in german) here.

Some pictures showing a the 714 being energized:



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18 Responses to “Thyratrons”

  1. 1
    Joey:

    Awesomeness! I want to do what you do, I play with electronics as a hobby and what you do is awesome! Please keep up the good work

  2. 2
    Radu Motisan:

    thanks Joey

  3. 3
    Ronert:

    Domnule Radu un videoclip exceptional foarte bine realizat, cu ce program ati creat acest videoclip? Cum se numeste soundtrack-ul?

  4. 4
    Radu Motisan:

    Multumesc , Robert!

  5. 5
    Casian Tact:

    Felicitari, domnule Radu! Ati facut o treaba foarte buna!

  6. 6
    venki:

    hi
    i want to know how 2d21 model thyratron works. actually it consists of two grids.i want to know how they function.

  7. 7
    Cuningan:

    hello, i am impressed !! how beautiful is a thyratron working.
    I have a nixie clock, a tube amplifier and other “old fashioned” electronics, only for decorative purpose.
    I am thinking to make one thyratron “driver” for decorative purpose also, but is hard to find information about.
    ¿Do you think that is possible to make a design to maintain the thyratron working all the day without damaging it ?.
    I think that i must have a high DC source but a really low consumption, in the border of the thyratron shutdown.

  8. 8
    Radu Motisan:

    Yes, I think your idea would work!

  9. 9
    Cuningan:

    Ok !! i will try to make it, when i finished i will post here the result, i hope the result will be positive ;D

  10. 10
    Radu Motisan:

    Sounds good, looking forward to see it!

  11. 11
    Andy Gray:

    Do you know where I can get an older glass thyratron tube that was used in a modulator for an/GPS-20 type radar. These were about 12″ tall. Wanting for display only. I was a radar technician in the USAF and remember these getting turned into neat displays back-lit.

    Thanks. Andy

  12. 12
    Radu Motisan:

    @Andy, wish I knew..

  13. 13
    Alex L.:

    Am si eu o intrebare nevinovata…de unde ai facut rost de toate tuburile din colectia ta absolut fabuloasa? btw…genial videoclip, iti admir munca si tine-o tot asa.

  14. 14
    Radu Motisan:

    Multumesc Alex. Tuburile tiratron prezentate aici, le-am prins pe ebay la un pret bun. Dar stii cum e, cand ai o anumita pasiune, strangi diverse lucruri care au legatura. Partea grea e sa le si folosim, ca timpul parca nu e niciodata destul.

  15. 15
    Tube: TGI2 400/16 (ТГИ2-400/16), Russian hydrogen thyratron « PocketMagic:

    [...] already presented a few words on Thyratrons in one of my previous articles on this topic. Now I want to show you a new addition to my collection, a hydrogen thyratron [...]

  16. 16
    mario:

    me gusta la electronica,para crear cosas raras para los demas que desconocen,

  17. 17
    gabi:

    imi trimiti si mie schema te rog? e scumpa o lampa dinaia si produce radiatii nu?

  18. 18
    Radu Motisan:

    @gabi, produce lumina si lumina e si ea o forma de radiatie electromagnetica.
    Dar probabil te referi la radiatie ionizanta ca si cea produsa in procesele nucleare. Aceste tuburi NU produc astfel de radiatii.

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