405nm jacobs ladder

first i want to say is,
ive been here about a year as a member and this is by far the coolest ,smartest most professional site ive ever had the oppurtunity to be a member of.good job to whoevers in charge.

ok in physics,50% ionization of air is 0 resistence to electricity.
so couldnt two uv lasers be used to make a jacobs ladder.to replace the two wires.
for those who dont know,a jacobs ladder is the thing with two parrallel wires that have a spark run between and up.usually mad scientist and dr.frankenstein have them.sometimes they may have a slight v shape to the two wires.
any thoughts?

That sounds awesome! Let me think about it a bit.

Something inside me says no, but I would love to see what people who know things about stuff like this say.

if we take it a step further and mount a tazer on to two insulated handheld lasers.then when the tazer is fired,the positive voltage runs down one beam and negative down another beam.when these beams hit a person.they short out and so basically it would be a long distance tazer.

robomont said:

if we take it a step further and mount a tazer on to two insulated handheld lasers.then when the tazer is fired,the positive voltage runs down one beam and negative down another beam.when these beams hit a person.they short out and so beasically it would be a long distance tazer.

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...............You just blew my mind..

Out in town so can't write a fully reply in detail; the short answer is no; the irradiance level needed for air ionization with >300nm isn't available outside of high intensity pulsed lab lasers.

I'll reply in detail if someone bumps this thread or I remember to come back, lol.

no problem sig.i would love to have a more detailed description when you have time.also is it possible to build hand held pulse lasers in the correct frequency that would give the needed ionization ?

Back home now.

The problem isn't frequency per se. Granted, frequency (actually pulse width) has a lot to do with the energy deposition amplitude in pulsed systems, but it isn't a matter of finding the right frequency, it is a matter of having enough joules in a single pulse.

A better way to explain it is this; pulsing a CW laser does not a "pulse laser" make. In other words you can pulse your 5W 450nm diode as fast as you want, but it will NEVER cause induced air ionization.

There are a few ways to generate laser induced plasma breakdown of air, all of them involve Q switched lasers. The typical lasers are Nd:YAG (pure (IR), doubled (532), tripled (355), and quadrupled (266)), CO2, N2 (not TEA), Ti-Saph, and Ruby. These lasers deliver many joules of energy per pulse. If these were to operate CW or QCW you'd be talking about kilowatts of power. Handheld technology cannot even store enough pump energy to power one of these lasers. We can get close with Nd:YAG by using a backpack based power and cooling system, but it would be an engineering feat.

An important thing to note is that these lasers do not induce a plasma channel the entire length of the beam, but only at a single focal point where the laser is focused.

Mechanics: air ionization (of a theoretical source, not from laser light) would result in a plasma channel forming along the axis of ionization not perpendicular to it. In other words if you have two plasma-inducing-fictional-laser beams facing vertically with a distance between the two parallel beams and placed an electrode at each beam's ionization spot nothing would happen (other than two loud bangs). No current would flow as electrically it is the same thing as having slightly longer electrodes. There is no path for the current to flow since the ionization points are parallel and the voltage isn't enough to break down the gap between points. If you have the two points on lines that intersect at some point then you could have a current flow provided the charge voltage is set so that it doesn't break down the gap until the gap is slightly shortened by the ionization of the focal point.

It wouldn't be a continuous flow though, it would just be a momentary pulse of electricity. High current discharge would allow for thermal energy from the discharge to extend the life of the plasma, but only for a short period before convection kicks in. Convection draws the ionized air up and out of the plasma channel, and nonionized air replaces it from below. This regular air presents a higher resistance, which restricts current, increases the voltage drop across the arc, and soon the arc extinguishes. You wouldn't get a traveling arc as in a jacob's ladder, as the ladder electrodes form a new jumping off point for the vertically rising stream of ionized air. If you film a ladder in high speed it is actually a series of individual air breakdowns that follows the initially ionized air upward. Also, the voltage has to exceed the air breakdown potential of nonionized air to initiate the process. In the laser induced ionization example the voltage is less than the nonionized breakdown potential so after the ionized air moves upward and the arc extinguishes there is nothing left to initiate another arc. You could use another pulse from the laser but there's not much point, raising the voltage would allow repeated arc formations without the need of expensive, fragile, and overly complex laser systems.

thankyou sig.that is a very detailed explanation and i understood all of it.:wave:

i had forgotton about the jacobs ladder needing to be vertical for the ioniz

thankyou sig.that is a very detailed explanation and i understood all of it.:wave:

i had forgotton about the jacobs ladder needing to be vertical for the ionized smoke to rise within the two wires.
i sent you an email also..again,thankyou for your time and input.

No problem at all, glad to help. Questions like these are what promote intellectual growth. Never stop dreaming things up, just remember to equally temper dreaming and curiosity with due diligence and research. To wonder about everything does a philosophical man make, but to invest one's self in learning about all he wonders a wise man does make.

That would be really cool and will probably be possible 50 years from now because of something we overlooked but I do not think that is possible as I do believe that the wires vary in resistance(to allow the electricity to climb) while a laser simply can't do that. I am not an expert on that sort of stuff though so I can't be sure.

Yes, good explanation, sig. To create more than a small "point" of ionized air would require a tremendous
amount of energy because the instability acts as a lens to defocus the laser. Even the most powerful
lasers aren't powerful enough.

The Lightning Stalker said:

Yes, good explanation, sig. To create more than a small "point" of ionized air would require a tremendous
amount of energy because the instability acts as a lens to defocus the laser. Even the most powerful
lasers aren't powerful enough.

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Correct, I couldn't agree more with the above statement.

Sigurthr said:

An important thing to note is that these lasers do not induce a plasma channel the entire length of the beam, but only at a single focal point where the laser is focused.

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Recently a paper was presented where two laser beams propagated collinear in a way that the second beam pumped the first, and the first generated a very long channel. I think it was in Laser Focus World.

lazeristasUVISIR said:

Recently a paper was presented where two laser beams propagated collinear in a way that the second beam pumped the first, and the first generated a very long channel. I think it was in Laser Focus World.

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Dual Laser Beam Creates Plasma Channel

But much earlier research has already been done:
This paper in 2011 - University of Arizona
And this paper in 2008 - Journal of Applied Physics 103, 103111