Voltage multiplier inside vacuum chamber

[DaveC]

Josh -

On the concept of building an HV multiplier inside a vacuum chamber -
The short answer is "YES" is can be done. A more specific answer is that practically speaking, it depends on the pressure you intend to have in the chamber.

The key to understanding the answer to the question you've asked, is the behavior of the Paschen Curve for the gases of either atmosphere or those in the Fusor - mainly Deuterium. Use the Search function here and/or check out Google for more info.

The Paschen curve plots breakdown voltage between two electrodes vs the product of inter-electrode spacing and pressure. The curves are different for each gas and to some extent, the families of curves will differ depending on electrode shape and material. That said, all the curves exhibit a concave upward shape, although they are by no means either symmetrical or any regular curve.

As to what voltage your internal circuitry could safely withstand without suffering a flashover, it depends on gas type, electrode shapes and pressure, mainly.

At the pressures within a normally operating fusor - 10 to 20 mTorr - breakdown voltages in D2 are obviously in the range of few tens of kV, since those voltages can be sustained across the internal electrodes, with their typical separation and geometries.

An HV multiplier, with its closely spaced electrodes, has a different value for the pressure-separating distance product and hence a different breakdown voltage. This breakdown voltage could be lower than the fusor's breakdown voltage.. because of the higihly curved wires and electrode, or it could be higher because of the close spacing. So, it might work or the multiplier might go into glow discharge be limited to some lower output voltage.

At high vacuum conditions, below 1E-5 Torr, the concept will definitely work well. It has been considered before (reference not available) for high vacuum conditions.

However, construction will be of paramount importance - since outgassing, component failure, overheating and related issues are important but solvable problems. Not trivial, however.

As to the lightning powered fusor.... it IS a way to go out in grand style.. Mostly it's useful for reducing the gene pool... and COULD be a candidate for a DARWIN award, perhaps in some scientific category.

Edit: Removing the "vestigial" Darwin....

Dave Cooper

[Jeroen Vriesman]

I have given the idea of a voltage multiplier inside the vacuum chamber some thougts in the past.

I had the idea of putting capacitors and diodes in a glass tube, and fill it with heat conducting epoxy, exposing only a minimal area of epoxy on the vacuum side.

The components should be small, so the only way to make it work would be to use a high frequency, the idea was to use a big output transformer from an old audio power tube amplifier and use it at 4kHz (which is already a bit high for a tube amplifier audio transformer, I don't know if the output power is still enough at 4kHz).

The secondary windings (these are primary in the tube amplifier) should be disconnected from each other in order to use one winding for ripple rejection. (make two leads from what was originally the center tap).

The simulation still shows a ripple of about 400V, but that could be compensated by disconnecting the lower secondary winding from ground and using "active ripple rejection" (see http://nuclearfusionreactor.blogspot.co ... ltage.html for an example of active ripple rejection)

For the GI250-4 (any 4kV diode which can handle the current would do) I used:
.model GI250-4 D(Is=5u Rs=3 N=1.2 EG=1.11 XTI=3 BV=4200 IBV=1e-04 Cjo=3p Vj=3.5 M=.5 tt=30n Iave=.25 Vpk=4200 mfg=VISHAY type=silicon)

A transformer with dual 2kV output which works at 4kHz might be a bit hard to find.

But the ceramic 2kV capacitors are small and so are the diodes, they would fit in a not-too-big glass tube.

[DaveC]

Audio power transformers can have a rather high frequency capability. Some of the old high quality tube amplifiers were nearly linear to 100 kHz. (thinking about a McIntosh Professional Audio amplifier, so the output transformers had to be equal to the task. Transformer-less transistor amps, though, sidestepped that issue.

So your idea is certainly viable...since even the low priced equipment was good to 15kHZ or so. HV multipliers typically operate below 50 kHZ because of diode limitations, although some high end gear works at much higher freqs.

Dave Cooper

[JonathanH13]

>Lightening packs an incredible amount of high voltage electrical power

The 'average' single lightning stroke (100 MV @ 30 kA), has a peak power output of somewhere between one and three trillion watts, but measured estimates have been made as high as 1 GV @ 120 kA.

>a bit Frankenstein-bonkers, really, isn't it?

Yes, definitely.

>practical experiments, not wishful fanatasies.

Not fantasy, and not outside the realm of practical experiments:

I did a series of lightning experiments in South Africa when I was 24. I started with huge meteorological balloons filled with hydrogen. A balloon was attached to a large reel of copper wire (several kilometres in length, 0.2mm diameter). I would wait for the storm to be overhead, and then release the balloon. It would climb rapidly to a few hundred meters, but then the weight of the wire would start to drag it down, and the surface area of the balloon resulted in it being pushed sideways by the storm-front. The balloon does not have to get very high to become the highest point in the area, and at about 100 meters up, the local ground charge profile changes radically, as electrons start to leave the area en masse. This coincides with a 'serious amount' of induced charge in the wire, and the unravelling wire reel literally turns into a ball of blue fire, all your hair stands up on end and you will receive a serious shock off anything metal in the area. This is a good indication that you are standing at ground-zero during leader formation, that you have seconds left to live, and that you should think about being somewhere else.

After several such experiments I switched to large home-made rockets. These are faster and more expensive; they cannot lift as much wire as a balloon, but they have a smaller surface area, so they tend to go straight up into the thundercloud, often breaking the wire on take-off

I initiated several 'controlled strikes', and have had lightning strike as close as 2 meters away from me - knocking me off me feet and leaving a blue glow in the air around me.

>Total cost, about $30

More like $300 per controlled strike.

Using this as a power source for a fusor? Isn't the ultimate aim of a fusor to produce electrical power? So you are converting electrons to neutrons so you can somehow convert them back into electrons?

Seriously though, what you want is to NOT have an actual lightning strike (which destroys everything), but the induced charge off a suitably high (100m) antenna could generate a sufficiently high potential to operate a fusor. You would need to discriminate polarity; lightning can be positive or negative (positive strikes are about 1 out of 10).

>ludicrous and dangerous...Stupid, stupid, stupid.

Experiments involving lightning are always risky and frequently fatal.

One of the most well-known deaths during the spate of Franklin imitators was that of Professor Georg Richmann of Saint Petersburg, Russia. (Wikipedia)

http://www.guardian.co.uk/world/picture ... MP=twt_ipd

[Richard Hull]

What makes fusion happen in useful, measurable amounts is ion populations (current) and not specific charge or potential alone. Antenna systems in high fields can't warrant, in general, the 20 ma or more continuous currents at fusor potentials.

This factor would be a surface area issue of the isotropic antenna (net capacitance).

A thunderstorm and local ground referenced, collected electrostatic potential energy is not a fun, stable or safe power source for any fusion device.

Most folks will have enough high adventure trying not to kill themselves with a precision, ultra stable, custom engineered, 60kv mains supply.

Richard Hull