EMP device

[Arthis]

The EMP weapon is one of the most powerful tools someone can dream about, in order to put anarchy or so without causing any casualties.
End of the introduction.

I found a few link about EMP: <a href="http://www.eskimo.com/~bilb/freenrg/empweap.html" target="_blank">http://www.eskimo.com/~bilb/freenrg/empweap.html</a> ,
<a href="http://www.fas.org/irp/threat/mctl98-2/p2sec06.pdf" target="_blank">http://www.fas.org/irp/threat/mctl98-2/p2sec06.pdf</a> that may be interesting.

</font><blockquote><font size="1" face="Verdana, Arial, Helvetica">quote:</font><hr /><font size="2" face="Verdana, Arial, Helvetica"> A commercial 100 kV DC power supply was used to charge the 20-stage Marx,
where it charged its capacitors in parallel, and then via a series of
spark gaps discharged them in series. With the power supply set to 27 kV,
the Marx would output a 265 kV, 3500 ampere, 21.4-nanosecond pulse </font><hr /></blockquote><font size="2" face="Verdana, Arial, Helvetica">This seems to be a good EMP device, but then a few questions come to my mind: such a generator should deliver a very high pulse, considered that atomic bombs deliver a pulse of 100 kV (if I remember well). Later in the text, it's said that they managed to destroy computers... Considering that they made the experiments on the ground, I understand that the range of the experiment was not really wide.
A very wide range can be reached with a HEMP (High-altitude EMP), between 20-40 km. It would be able to reach, if launched in the middle of the USA, the whole North America. The curve of the Earth is reducing the range of ground-based explosions, but considering that EMP is a electromagnetic field, it should be able to "curv" itself, with interferometry for example, as the pulse produced is so fast that the source can be considered as coherent.

The fact that the pulse delivered by the marx generator is long (21.4 ns) compared to those emitted by better systems (~10ns), and very long compared to the one delivered by nuclear weapons (~a few ns, basically 1 ns) may be one point to be taken into account.

Another point I was wondering about is the physical aspect of the pulse. The pulse is a electromagnetic wave, but its generated by excited electrons hit by photons. Are the electrons also moving (I know they are not part of the pure EM wave) allowing the device to have an exponential effect in its area of detonation ?

Finally, such a device would be a really great stuff for anyone: think about what you can do with. You can destroy communications, then attack a place, or it may allow to pose bombs without being recorded by cameras, and it may turn a city into anarchy: imagine new-york without electricity: I doubt many systems are protected against EMP. (Maybe I should have seen Ocean's Eleven twice: it gives me bad ideas, though I knew the system well before).

[nbk2000]

You're not going to get nation-paralyzing EMP without exploding a multi-megaton H-bomb in the exosphere. NOTHING even comes close to matching the EMP pulse of a nuke, in either raw power, or in rise time.

[Arthis]

I know that we cannot make a nation-paralysing EMP generator, and of course it's not what I want. I first would like to understand some points, that I asked, but no matter I keep searching. And the test made in the link I gave used a commercial high voltage generator to charge the marx generator, what I, as one may guess, can't afford.

What I want is to make even a small EMP device, in order to be able to provoke even small power defficiences, or/and destroy low ranged electronic devices. I think it's possible to make that with affordable material, though I haven't checked yet all what is needed to.
It would be used for example to cut all systems of a place I want to get in: when you want to raid a deposit (is it the right word ?), you take less risks if you cut communications, even for a short while.

But anyway, no one has any answer about the theory, about what I asked ?

[Mr Cool]

Here we go again...

The output of the Marx bank will need to be coupled to some sort of electrical resonator, be it a big magnetron with big, powerful magnets to cope with the high voltage, or an LC circuit like in a tesla coil. This second one would be simplest, there are plans on the internet for producing tesla coils of many kW. Make it the bipolar type and you wouldn't need a ground connection. You'd need an output capacitance, the toroid/sphere, that was physically large with a large radius of curvature. This way you're less likely to get arcing, which would use up energy that would otherwise go into the wave.
The output of the Marx bank could also be coupled to a flux compression generator (IIRC that's what they're called), where a solenoid with a large current through it is progressively shorted by a copper cylinder that is expanded by an explosive charge.

"atomic bombs deliver a pulse of 100 kV"

Atomic bombs produce no electricity. Maybe the photons responsible for the EMP have energies of around 100keV? But this seems quite a low energy...
It's my understanding that the photons from the nuke blast hit electrons in the gas of the atmosphere, and eject them (inverse bremstrahlung radiation, sp?). The high-energy electrons produced are under the influence of the Earth's magnetic field, which causes them to bend and emit radiation, similar to synchrotron radiation (charged particles accelerating emit EM radiation).
A high altitude EMP would need massive amounts of power to do anything at the surface, due to the inverse square law. Only nukes can provide this power.
A non-nuke one could be made, but it would not be a concealable "bomb" type device. It would have to be truck/lorry sized to have a significant effect.
A rich terrorist could probably create an EM area-denial device, using lots of generators and lots and lots of modified microwave ovens, picked up at a scrap yard. Modify the ovens to work with their doors open, and make a wall of them on one side of a lorry. Turn on the generators, and anyone too close gets very hot and is forced to retreat. But gas would be more cost effective!!

[Arthis]

It's a pretty surprising difference compared to what we can find on the web, I remember having read about E-bombs for 400$ on a serious magazine, and though I never believed the information.

Thanks for the info anyway.

Another link for anyone interested despite difficulties: <a href="http://www.airpower.maxwell.af.mil/airchronicles/kopp/apjemp.html" target="_blank">http://www.airpower.maxwell.af.mil/airchronicles/kopp/apjemp.html</a>

<small>[ February 10, 2003, 11:51 AM: Message edited by: Arthis ]</small>

[controlphreak]

The magazine by the way was Popular Science and they were talking about it. If I remmeber correctly, they designed one in very gernal detail where in the end of the bomb (where the fins were) they had the propellents, and then a huge battery and then a capacitor. Then infront of that, they had a copper pipe filled with C-4 or some other explisve compund surrounded by a thick copper wire. Then in the cone, they had a warhead that created shrapnel. The theory behind it was that an instnat before detonation, allt he power in the battery would go into the capacitor and then into the copper coil, which would then create a magnetic field. The core rod would explode and create shrapnel which would act like a moving short circut.

I apologize if I am wrong, my first post on this board, and I am doing that from memory.

Controlphreak

[Tuatara]

Mr Cool has it 99% right. Sadly Tesla coils do not operate at a high enough frequency to be of any use (typically under 1 MHz).

Marx bank wont work without some form of antenna to radiate the power - and it is extremely difficult to build a really wideband antenna to handle the kind of power you want to transmit.

Best results so far have been done using BIG magnetrons, powered by a compulsator (compensated pulsed altnerator - really impressive beasties, go search;) ) or a flux compression generator, which is more along the lines of interest in this forum as it uses an explosive to generate electrical power (single use only!)

Oh, and any URL with 'freenrg' in it instantly sets off my 'pseudo-science' warning bells.

[firebreether]

If you want a reusable device for short range attacks. I'd suggest HERF- alot of that going on here: www.voltsamps.com (http://www.voltsamps.com) Itll be weak, but have a useable range, and be built from off the shelf (literally) components. Or at least, instead of bothering with a marx generator, first try a simple cap discharge bank, Then work your way up if you need to.

Non reuseable probably flux compression device. Problem is testing destroys your device so requires muchos dollars.

The electrons created in a nuclear EMP event are moving fast, and changing direction fast too, this is what causes the EM waves to form i believe. Im not sure what an exponential effect in the area of detonation means, but im assuming we arent talking nuclear anymore, which would mean that there wont be (m)any stray electrons. But with any wave taveling in a spherical path outward, the intensity will follow the inverse square law, double the distance, you get 1/4 the intensity, if that helps.

The process where electrons are excited by incident photons is called compton scattering. And I believe prompt fission gammas tend to average in the 1 MeV range.