Help with a pulse circuit design

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Thread Starter

Deleted member 552872

Joined Dec 31, 1969
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I plan to build a high power pulse circuit to experiment with Townsend Avalanche in a gas tube.

I'm not sure how to build the pulse circuit input.

Background: A Townsend Avalanche is used in gas tubes, such as neon tubes, and fluorescent tubes, to get 'more bang for the buck' from input voltage. Once the gas in the tube is ionized, a chain reaction occurs where the initially freed electrons generate more electrons. Sort of like if you hooked up voltage to a circuit with a supply of N flowing electrons, then suddenly the wire produced 10N more electrons. A wire cannot do that but an ionized gas in a tube can.

Any recommendations on how to build a high power (high voltage, high current) pulsing circuit is what I need. Ideally the voltage/current level need to be adjustable and so does the time duration of the pulse. I have my own oscilloscope, a 120vdc 10 amp adjustable power supply, and a function generator.

Although I can buy, say, a fluorescent light bulb fixture, then buy a fluorescent light bulb for the fixture and connect it to house 120vac and see the Townsend Avalanche in a commercial product, that's not what I'm seeking.

I specifically want to pulse (not use alternating 120vac) the tube. I have a working familiarity with building/troubleshooting electronic circuits - 2 years military training with communications equipment (receiver/transmitters), 2 years Devry. But I don't consider myself a designer, except for very basic circuits. I have zero experience creating or troubleshooting pulse output circuits. And I'm an old guy, semi-retired, this is my hobby, and a lot of stuff - I have forgotten.

Initially, I will remove the ballast from an off-the-shelf fluorescent or neon tube fixture and apply the pulse circuit output across the tube.
 

Thread Starter

Deleted member 552872

Joined Dec 31, 1969
0
What voltage, current, pulse width, rise/fall time do you need?
The ideal would be "build once" so the upper bound of parameters would be 1 Megavolts, 100 amps, arbitrarily adjustable duty cycle (a pulse width adjustable from, say, 1% to 100% of the rise/fall time period), and sharp-edged rise/fall time, so that the pulse would have a pretty sharp square wave appearance on the oscilloscope.


That's the ideal but I'm just a hobbyist, I really have no idea what sort of design implication this ideal pulse circuit would entail. Maybe it's a small matter but I don't have any experience references in my background to know. I'm 100% comfortable working with very high voltage and high current, as I did so for many years in industry.

The "build once" would mean I'd build the pulse circuit one time and it would have enough flexibility in range available for its voltage output, its current output, and adjustable duty cycle that I wouldn't have to build another one too quickly, as I explore the Townsend Avalanche phenomena of gas tubes.
 

Papabravo

Joined Feb 24, 2006
13,939
You can get either high voltage or high current, but getting both at the same time will be an extraordinary challenge. In addition to the stringent safety precautions such an enterprise will entail how do you propose to pay for it. You are looking for 100 Megawatts, which means you are no longer a residential customer, and I'm thinking you will need considerable funds just to get the input power for such a device.
 

Thread Starter

Deleted member 552872

Joined Dec 31, 1969
0
You can get either high voltage or high current, but getting both at the same time will be an extraordinary challenge. In addition to the stringent safety precautions such an enterprise will entail how do you propose to pay for it. You are looking for 100 Megawatts, which means you are no longer a residential customer, and I'm thinking you will need considerable funds just to get the input power for such a device.
The upper range of 100 amps and 1 Megavolt was me saying "I don't want to have to build another pulse circuit if, during my experimenting with Townsend Avalanche in tubes, I discover I need more power." I have no desire to tax the local utility!

A couple of other things. First, the pulse circuit I'll use would not be a continual use of 100 Megawatts - it would be pulsed, and not pulsed continuously.

Second, I have no idea that I'd ever need to have simultaneous high current/high voltage. I think it's possible as the gas in the tube goes into conduction mode that it will momentarily pull some power but that would be after the pulse has happened - it would occur due to the Townsend Avalanche in the tube.

Also, to strike a plasma in some of the tubes I'm thinking of experimenting with, a high peak power input is required for the pulse.

As an analogy, the "1 Mvolt/100 amps/1% to 99% duty cycle" design was in the vein of buying shoes for your kids when they're young, and buying them big enough so they can grow into them a bit, rather than buy new shoes repeatedly.
 

Papabravo

Joined Feb 24, 2006
13,939
I think your approach is flawed. We learn more from our failures than from our successes. This is not an area of circuit design or operation where getting it right the first time is a given. The way you stated the requirement made it sound like you needed 100 Megawatts which is a lot even if it is pulsed. What you don't know about such current and voltage levels can and will KILL YOU. What you need to do is learn to crawl and walk in this area before you try to run a marathon. So dial things back a bit and you will get there sooner. Trust me on this.

My recommendation is to start with something like 1 kilovolt @ 100 microamperes. That should be achievable in reasonable time with available components, and it's only nine orders of magnitude away from your goal.

As another analogy, astronomers want telescopes with mirrors that have as large a diameter as possible. Grinding a large mirror to precise specifications is an arduous and exacting task. The only way to learn how to make a 20' mirror is to start with a 2' mirror. Learning the technology and perfecting your craft is the key to success.
 
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Thread Starter

Deleted member 552872

Joined Dec 31, 1969
0
I think your approach is flawed. We learn more from our failures than from our successes. This is not an area of circuit design or operation where getting it right the first time is a given. The way you stated the requirement made it sound like you needed 100 Megawatts which is a lot even if it is pulsed. What you don't know about such current and voltage levels can and will KILL YOU. What you need to do is learn to crawl and walk in this area before you try to run a marathon. So dial things back a bit and you will get there sooner. Trust me on this.

My recommendation is to start with something like 1 kilovolt @ 100 microamperes. That should be achievable in reasonable time with available components, and it's only nine orders of magnitude away from your goal.

As another analogy, astronomers want telescopes with mirrors that have as large a diameter as possible. Grinding a large mirror to precise specifications is an arduous and exacting task. The only way to learn how to make a 20' mirror is to start with a 2' mirror. Learning the technology and perfecting your craft is the key to success.
I appreciate your feedback.

However, I fully intend on building the pulse driver just one time, if possible. I prefer building it once, and having such a range of pulse output parameters available so that, if at some point during experiments with gas tubes, I decide I need it, I won't have to stop my experiments and have to build a new pulse driver circuit. To be clear, I prefer building much more than I need from the beginning.

See, my true purpose is to experiment with gas discharge tubes, and *not* experiment with lots of different pulse circuits. The pulse circuit is a means to an end, the end being the commencement of experimenting with gas discharge tubes and Townsend Avalanche.

As I mentioned previously, I'm also 100% comfortable and familiar with high voltage and high current, having worked on such equipment for several years in industry.

My goal in posting was to get pointers on high power pulse circuit design, along the lines of 'components typically used', maybe even a schematic or two, and so on. I specifically posted in this section - Forums->Hardware Design->Power Electronics precisely because of past experience with high voltage and high current machinery.
 

Papabravo

Joined Feb 24, 2006
13,939
I appreciate your feedback.

However, I fully intend on building the pulse driver just one time, if possible. I prefer building it once, and having such a range of pulse output parameters available so that, if at some point during experiments with gas tubes, I decide I need it, I won't have to stop my experiments and have to build a new pulse driver circuit. To be clear, I prefer building much more than I need from the beginning.

See, my true purpose is to experiment with gas discharge tubes, and *not* experiment with lots of different pulse circuits. The pulse circuit is a means to an end, the end being the commencement of experimenting with gas discharge tubes and Townsend Avalanche.

As I mentioned previously, I'm also 100% comfortable and familiar with high voltage and high current, having worked on such equipment for several years in industry.

My goal in posting was to get pointers on high power pulse circuit design, along the lines of 'components typically used', maybe even a schematic or two, and so on. I specifically posted in this section - Forums->Hardware Design->Power Electronics precisely because of past experience with high voltage and high current machinery.
I don't know for a fact that anybody on this board has the experience to guide you on this mission that you've chosen. In any case Good Luck with finding what you need.
 

Thread Starter

Deleted member 552872

Joined Dec 31, 1969
0
Okay, that's it for 'All About Circuits.' Reputation?
 

OBW0549

Joined Mar 2, 2015
3,454
I don't know for a fact that anybody on this board has the experience to guide you on this mission that you've chosen.
And even if they had the knowledge and experience, I'm certain they wouldn't be so foolish as to tell this guy how to build such a device.
Reputation?
I doubt our reputation is at risk for declining to tell a hobbyist with "no idea what sort of design implication this ideal pulse circuit would entail" how to build a 1 Megavolt, 100 amp pulse generator. For anyone to assist you in killing yourself would be the height of irresponsibility.
Okay, that's it for 'All About Circuits.'
Byebye... :)
 

Papabravo

Joined Feb 24, 2006
13,939
And even if they had the knowledge and experience, I'm certain they wouldn't be so foolish as to tell this guy how to build such a device.

I doubt our reputation is at risk for declining to tell a hobbyist with "no idea what sort of design implication this ideal pulse circuit would entail" how to build a 1 Megavolt, 100 amp pulse generator. For anyone to assist you in killing yourself would be the height of irresponsibility.

Byebye... :)
Thank you. I would have said the same thing, but I knew he wasn't listening to me.
 

SiCEngineer

Joined May 22, 2019
216
I think your approach is flawed. We learn more from our failures than from our successes. This is not an area of circuit design or operation where getting it right the first time is a given. The way you stated the requirement made it sound like you needed 100 Megawatts which is a lot even if it is pulsed. What you don't know about such current and voltage levels can and will KILL YOU. What you need to do is learn to crawl and walk in this area before you try to run a marathon. So dial things back a bit and you will get there sooner. Trust me on this.

My recommendation is to start with something like 1 kilovolt @ 100 microamperes. That should be achievable in reasonable time with available components, and it's only nine orders of magnitude away from your goal.

As another analogy, astronomers want telescopes with mirrors that have as large a diameter as possible. Grinding a large mirror to precise specifications is an arduous and exacting task. The only way to learn how to make a 20' mirror is to start with a 2' mirror. Learning the technology and perfecting your craft is the key to success.
I second this. As a PhD student working on high voltage converters, you ALWAYS have to build the converter on a much lower level which is considered more safe. My converter which is a -6kV converter with 660W, will most likely be needed to be tested at a maximum of 1kV with less current. I have been studying with high voltage for 2 years and you do not even begin to scratch the surface of the intricacies of this field. It is better to build safely and move on upwards rather than try and achieve such levels and as you say, one mistake with such specification will kill you.
 

Papabravo

Joined Feb 24, 2006
13,939
I just noticed the new status of the TS, Deleted member 552872. It has a definite air of...finality. No hits, no runs, one error. Is he alone by himself in that category, or are there others?
 

OBW0549

Joined Mar 2, 2015
3,454
I just noticed the new status of the TS, Deleted member 552872. It has a definite air of...finality. No hits, no runs, one error. Is he alone by himself in that category, or are there others?
I think I've seen a few others over the years. Not many, though.
 

DarthVolta

Joined Jan 27, 2015
477
1 Megavolts potenial difference, what do scientists make to actually produce such voltages ? What are the highest types of voltages big labs can make ? What happens to the materials ?
 

Papabravo

Joined Feb 24, 2006
13,939
In my original response, I said you could have high voltage or high current, but not both at the same time. These devices are ones I am familiar with. As smart friend of mine once said: "Don't put your lips on those things!"

Van de Graaff Generatos
The potential difference achieved by modern Van de Graaff generators can be as much as 5 megavolts.
https://en.wikipedia.org/wiki/Van_de_Graaff_generator

Tesla Coils
Tesla coils can produce output voltages from 50 kilovolts to several million volts for large coils.[15][17][19]
https://en.wikipedia.org/wiki/Tesla_coil

Rail Guns
This basic configuration is formed by a single loop of current and thus requires high currents (e.g., of order one million amperes) to produce sufficient accelerations (and muzzle velocities).
https://en.wikipedia.org/wiki/Railgun#:~:text=A railgun is a linear,kinetic energy to inflict damage.
 
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