Illuminating a Thyratron (mercury gas discharge)

In summary, the thyratron tube is an old technology that can be used to heat the filament and illuminate the mercury vapor for purposes of building a novelty lamp. The load resistor will be a 10K rheostat in series with a 2.4k Ohm resistor, and the lamp will be able to stay lit at low current if the anode resistor is high enough.
  • #1
bwinter
27
1
I found a thyratron tube at a yard sale recently and I want to build a circuit to heat the filament and illuminate the mercury vapor for purposes of building a novelty lamp.

The filament is just 2.5VDC at 7 amps and I have a transformer for that.

To light the vapor I will apply DC rectified and smoothed from the AC mains.

The illumination is related to current, and to achieve maximum illumination of the electrode I want to achieve something on the order of milliamps, above the current for Townsend discharge but below that of arc discharge. I don't know what those values will be so let's say, between .01 and .5 amps.

So V = IR
120 = 0.01R
12000 Ohm = R1

120 = .5R
2400 Ohm = R2

So my load resistor in series with the thyratron will be a 10K rheostat in series with a 2.4k Ohm resistor.

Hoping for any input from someone with tube experience, if this might work.
 
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  • #4
I'll be interested to see if you can hold off the avalanche after initiating the glow. I've only used 2D21 , fifty years ago.

Try severely limiting anode current , ie higher anode resistor ?

Keep us posted ?
 
  • #5
Good to know. Do you think 120V DC rectified is enough? What would be the benefit if any of transforming to a higher voltage?
 
  • #6
I don't see why you'd nee more voltage.

Cleaner copy of datasheet here

http://www.datasheetarchive.com/dl/7a2e304da0ac6860531847f5de30f97df76ae6/O/3C23
 
  • #7
Maybe you could use it like a regulator tube in a power supply like the one I built. Also I've uploaded the GE Glow Tube application sheet.

tubesupply A+B.jpg
GE_Glow_Tubes_ETI-176.pdf
 

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  • #8
dlgoff said:
Also I've uploaded the GE Glow Tube application sheet.

What a great find !

That thing just might stay lit at low enough current.

If not, perhaps make it into a relaxation oscillator at a few hundred hz, fast enough to appear continuous.
upload_2017-1-17_22-11-40.png


We used to do that ^^^^ with NE2's and a 90 volt B battery. I found that some resistance in series with the lamp prolonged its life.
 
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  • #9
I did it!
HLm9cVl.jpg

Funny operation though. Sometimes it will stay on without the heating filament and sometimes not, even if the current is the same. I have it connected through 168VDC and a series resistor (~2k).
 
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1. What is a Thyratron?

A Thyratron is a type of gas-filled tube that is used to switch electrical currents on and off. It contains a small amount of mercury vapor and can handle high voltages and currents, making it useful in various applications such as radar systems, radio transmitters, and particle accelerators.

2. How does a Thyratron work?

A Thyratron works by controlling the flow of electrons between two electrodes using the ionization of mercury vapor. When a high voltage is applied to the tube, the mercury vapor breaks down into a plasma, allowing a current to flow between the electrodes. When the voltage is removed, the plasma dissipates, and the current stops flowing.

3. What is the purpose of illuminating a Thyratron?

Illuminating a Thyratron refers to the process of turning it on and allowing it to reach its operating temperature. This is necessary because the mercury vapor inside the tube needs to be ionized for the Thyratron to function properly. The illumination process typically takes a few minutes, and once completed, the Thyratron is ready to switch currents on and off.

4. What are the advantages of using a Thyratron?

Thyratrons have several advantages, including their ability to handle high voltages and currents, fast switching speeds, and high reliability. They are also compact in size and can operate in a wide range of temperatures and environments, making them suitable for various industrial and scientific applications.

5. How do you properly maintain a Thyratron?

To ensure the proper functioning of a Thyratron, it is essential to regularly clean the electrodes and replace any damaged parts. It is also crucial to monitor the tube's operating conditions, such as temperature and voltage, and make any necessary adjustments. Additionally, following the manufacturer's recommended maintenance schedule can help prolong the Thyratron's lifespan and prevent malfunctions.

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