Fun With A Hydrogen Thyratron

There’s something oddly menacing about some vacuum tubes. The glass, the glowing filaments, the strange metal grids and wires suspended within – all those lead to a mysterious sci-fi look and the feeling that strange things are happening in there.

Add in a little high voltage and a tube that makes its own hydrogen, and you’ve got something extra scary. This hydrogen thyratron ended up being just the thing for [Kerry Wong]’s high-voltage, high-current experiments. One would normally turn to the solid-state version of the thyratron, the silicon controlled rectifier (SCR), to switch such voltages. But the devices needed to handle the 30 amps [Kerry] had in mind were exorbitant, and when the IGBTs he used as a substitute proved a little too fragile he turned to the Russian surplus market for help. There he found a TGI1-50/5 hydrogen thyratron, a tube that has a small hydrogen gas generator inside – thyratrons are actually gas-filled rather than vacuum tubes and switch heavy currents through plasma conduction. [Kerry] set up a demo circuit with a small RC network to provide the fast switching pulse preferred by the thyratron, and proceeded to run 3500 volts through a couple of 1/4-W resistors with predictable results. The video below shows the fireworks.

Can’t get enough of the thyratron’s lovely purple glow? We’ve seen it before on this beautiful old switch-mode power supply. The versatile tubes also helped rebuild the first vocal encryption system.

20 thoughts on “Fun With A Hydrogen Thyratron

  1. I was informed, in no uncertain terms, that Hydrogen Thyratrons are Export Controlled a few years back. Silly Security Officer.. I looked it up later..
    Only, Hydrogen/hydrogen-isotope thyratrons of ceramic-metal construction and rate for a peak current of 500 A or more, are under ITAR regulations. The ones I was told to pull from the old ruby lasers did not qualify.. Be careful out there.

        1. On some EC-121 radar planes they had one of these that was about 3 feet high. It was located right next to the aisle way and the adjustment pot was behind the tube where it could not be easily reached. It did have a nice purple glow.

          1. The tube itself was only about a little over a foot long. The housing, which was pressurized, was about 3 feet high. It fired off a large 325 pound magnetron that would output 5 megawatts in the lower 400 Mhz frequency range. I was a radar tech aboard those planes. It was an APS-95 radar.

        1. I think to remember there was an issue with them, as it happens they are also used in the shock-wave generator of machines to disintegrate kidney stones. So there was a classical dual-use dilemma.

    1. Sorry pressed report comment instead of replay.

      High power pulse lasers use those ceramic Thyratrons. We had thse from L3, think they are rated 30kV & ~30kA.

    2. From the Nuclear Weapons Archive (export controls, courtesy Oak Ridge National Laboratory) (a) Cold-cathode tubes (including gas krytron tubes and vacuum sprytron tubes), whether gas filled or not, operating similarly to a spark gap, containing three or more electrodes, and having all of the following characteristics: 1.Anode peak voltage rating of 2500 V or more, 2.Anode peak current rating of 100 A or more, 3.Anode delay time of 10 microsecond or less, and (b) Triggered spark-gaps having an anode delay time of 15 microsecond or less rated for a peak current of 500 A or more; (c) Modules or assemblies with a fast switching function having all of the following characteristics: 1.Anode peak voltage rating greater than 2000 V; 2.anode peak current rating of 500 A or more; and 3.turn-on time of 1 microsecond or less.

  2. I work with 45kV/9kA rated thyratrons as big as my forearm in our TEA lasers. We run ours at 36kV/7.5 kA, 270MW peak pulsed power!!! I didn’t even know what laser ablation was before I started using it to vaporize sapphire and other ceramics. All that power though, it can’t cut aluminum foil…

  3. Ahhh the purple glow. I used to work on a surface search radar that had a ceramic thyratron that by looking at how far down the purple glow had migrated I could tell about how close I was to replacement; the further down the body, the closer one was to replacement time.

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