Fusion grid / ac

It may be difficult to separate "theory" from "application," but let''s see if this helps facilitate the discussion.
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Fusion grid / ac

Post by guest »

I have a question. What would happen if you used an ac grid combined with the dc grid in a stainless steel system? Think of a regular grid except at the top or bottom a partial grid charged with something like a plasma globe electrode. Would this cause ionization of air or deutrium? Could you combine a plasma globe with a fusor to produce more plasma and increased efficency?

Lee Jarett
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Re: Fusion grid / ac

Post by Richard Hull »

The beauty of the fusor and one of the normal requirements within its interior, is perfect spherical geometry with no other conductors spoiling this. Other spheres or partial spheres would influence the field in ways that would alter the fields.

Only experiment would determine if, and to what degree, the addition of such components would be helpful or detremental.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: Fusion grid / ac

Post by guest »

In theory would ac work better than dc in creating plasma, not holding the field together as IEC does?
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Re: Fusion grid / ac

Post by Richard Hull »

AC as in sinusoidial?.....No, it just would not work out. There has always been talk of pulsed DC to get the currents up and increase fusion in bursts, but no amateur has attempted it yet.

Such a pulsed system would most likely use a hydrogen thyratron like a 5C22 or a ceramic H2 thyratron of higher voltage rating with the fusor on an elevated deck running a lethal shell voltage during pulse times. The ideal would be to maybe run the fusor in a non-threatening regime in the 25kv region where neutron production is moderate and then lift the case for some number of microseconds to an additional 15 KV by switching in a pulse capacitor with the thyratron.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: Fusion grid / ac

Post by DaveC »

On pulsed operation vs AC operation -

Tthe basic problem with using AC is the present electrode configuration consisting of concentric spherical shells, as Richard Hull as already noted. When the polarity changes, ions and electrons no longer form the virtual cathodes and anodes and the fields disappear which cause the ions to concentrate in the center... and fusion does not happen.

However, from the field models I have made so far, (and they are only 2-D representations, yet) it doesn't seem to make a lot of difference how assymetrical the area is "external" to the wire cage electrodes. Therefore.... it seems to me that an AC version COULD be made, if it had two sets of spherical cage electrodes, one for each polarity - side by side separated by some distance, say about two or three cage diameters, and with the AC applied between the cages.

Clearly this is a bigger construction... lends itself to a bell jar enclosure and but it might work. My own setup would allow my to try that... and it had also occurred to me to try it, but I haven't, yet.

Although it seems very simple - the actual process of propelling ions to a central region for collision at a KeV energies with the wire cage electrodes is rather intriguing. But, I am rather new to new this concept and probably missing something... The electric field plots -( which I do promise to post , once I figure out how to export them) - provide only hints at what is going on.

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Re: Fusion grid / ac

Post by DaveC »

Just a bit more on the pulsed mode itself...
Richard - couldn't we use a pulsed flyback transformer outputting through a HV blocking diode to over drive the basic DC supply ? For that matter, the pulsed supply could be the only supply. Most fly back cores, are good for a few hundred watts before they saturate and the actual cutoff frequencies (recovery times actually) are usually determined by the rectifiers specs. So it might not be too hard to implement.

I have driven the Phillips cores up over 1 MHz at low power, without significant distortion, so a thyristor, or some such, primary drive shouldn't be all that tough to do.

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Re: Fusion grid / ac

Post by Richard Hull »

Good thinking and nice idea on the flyback, BUT........

Those who have looked long and hard at the physics of plasmas or who have simply gazed into a demo device while raising and lowering the voltage will realize that raising an accelerating voltage rapidly on a happily working fusor is not going to require an additional couple of hundred watts.

For a sudden (microsecond) lift of the supply voltage to, say, almost double a fixed run voltage, the peak pulse currents are in the thousand amp or more range meaning megawatts of peak pulse power! This, in theory translates into an incredible burst of fusion, but not the destruction of the device. This is why the Miley team is off in this direction. This requires a charged capacitor connected by a fast megawatt switch (like a hydrogen thyratron). Still, If one wishes to try the flyback approach, that is what all this hands on stuff is about.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: Fusion grid / ac

Post by DaveC »

Good point... With the fusor on, I'd expect the plasma to look like a resistive load. The pulse would cause the moving ions to be the "displacement current" in the fusor. The velocity of a 10Kev Deuteron would be about 2.2 x10^6 m/sec, so a microsecond long pulse could loop it around the fusor a couple times. For pulses in the nanosecond range, (not too hard to get with a triggered spark gap - two doorknobs with a spark coil for the trigger, a cap of a few nF is the most you would need. You COULD use a length of coax as a transmission line surge source. The pulse width in nsec would be approximately 1.5 x length in ft.
Just have to terminate it nicely so there's no flashover.

Dave
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Re: Fusion grid / ac

Post by guest »

An idea just came to mind, after reading this thread and remembering sonething from another thread about the U of Wisconsin's fusor and findings that the fusion was ocurring in the mid region between the inner and outer grid.

Has anyone tried a balanced DC Bias AC system? I don't have the capability of working out the exact numbers at the moment, but run something like 40Kev DC bias and on top of that run 20Kev AC at a frequency resonant with the motion of the deuterium ions, to keep the major ion cloud outside the inner grid...

Common sense says this would thwart ion collision by restricting motion/producing an exponentially larger area for the ion cloud and therefore les density, but I'm going to play devil's advocate here and say, if the frequency of the AC signal were high enough, and the amplitude high enough, it would compress the ion cloud into a thin shell around the outside of the inner grid, and eddy currents from the inherent imbalances applied from the construction of the grids would produce enough motion for fusion?

I'm a beginner at this... and so would like very much for anyone and everyone to shoot this idea down simply so I can understand the IEC process better.
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Re: Fusion grid / ac

Post by guest »

I'm not going to shoot it down. I've had the same thought.

Unfortunately, my next purchase will be wood for a workbench to put my fusor on.
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Re: Fusion grid / ac

Post by Richard Hull »

Fusion seems to occur throughout the fusor, but due to deuteron collisions and neutral recombination the zone just outside of the central grid is favored. This region, with its large volume, is often where a lot of hot ion collisions occur. Them deuterons or them plasmas just don't like their own theoretical roles and won't behave to suit.
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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