Can a fusor explode?

It may be difficult to separate "theory" from "application," but let''s see if this helps facilitate the discussion.
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Steven Sesselmann
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Re: Can a fusor explode?

Post by Steven Sesselmann » Sun Nov 13, 2005 8:53 pm

Frank, I can't wait to hear more about your invention, because I am in the
same situation as you, and can't talk.

I hope both ideas are different and that they both work.

Mine still has to be built.

Steven
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Richard Hull
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Re: Can a fusor explode?

Post by Richard Hull » Mon Nov 14, 2005 3:21 pm

I'll have to go along with Marvin on this last idea of temperature of the plasma increasing. This is ostensibly not a thermal machine. It is not designed as one and, thus, it will not benefit from plasma heating as there is no confinement of the active heated plasma. As such, it all goes to the shell and is a complete loss mechanism. We fuse solely at the instant of collision, (pretty much near the center), we can't heat the gas in the entire vessel to fusion temps in a fusor. We might hope for boosting the efficiency of the central reaction by some artifice, but that is about it.

The fusor will destroy itself only when you put enough outside energy into it to do so. It will not dismantle itself due to any fusion process within. Long before you get decent fusion, you will feed in enough energy to heat the grid, insulator or a glass port to some failure mode unfriendly to the continuation of fusion, solely due to the input energy being converted to waste heat by particle bombardment.

The calcs are not wrong it is just the physical world will not let you get there from here. You will not tie down nature's safety valve placed on fusion.

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Steven Sesselmann
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Re: Can a fusor explode?

Post by Steven Sesselmann » Mon Nov 14, 2005 8:39 pm

Richard, yes, using Deuterium, it should be pretty unlikely to see a
cascade reaction, however I would want to do my calculations more
carefully if introducing Boron11 or Lithium6 or something like that.

Every now and then you should do a stocktake of the membership in this
group :)

Steven
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Re: Can a fusor explode?

Post by Frank Sanns » Mon Nov 14, 2005 10:46 pm

Marvin and Richard,

Your descriptions are great for option #1 of my post. More energy in equals proportionally more energy out.

For option #2 this does not and can not hold. The mechanism is not what we think for conventional hot fusion. It is not because we never come anywhere near the density to sustain fusion. If there were a runaway or if for some reason fusion would occur by another mechanism as it might in sonofusion or cold fusion or in Bose Einstein Condensates, then the criteria in which you refer will not be true in the least. If a fusor goes bang or even poof, then something else besides conventional hot plasma physics is going on in there.

My post addresses both of these scenarios so Marvin, I was not disagreeing with you but I was not totally agreeing with you either.

Frank S.

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Re: Can a fusor explode?

Post by Richard Hull » Tue Nov 15, 2005 4:48 pm

Any such "other" method would be interesting to see or hear about in an active experimental sense.

As for Steve's B-11 and Lithium 6 ideas with deuterium....Well, so far, no one has presented physical proof of that pudding in a fusor. I wonder when reactions with B-11 will die the natural death they deserve until someone puts a foot in the path and burns th' stuff, supplying proof of all the hypothetical machinations and as yet unbaked thermonuclear puddings.

Everyone who posits or rehangs the B-11 reaction thinks they can get the ultra-expensive, enriched and lethal B-11 in the chamber in some convenient fashion. The doing here is quite a task. Even less expensive, un-enriched natural B product presents the same lethal possibilities and nightmares. (if un-enriched 20% of your boron banging is waste heat.) Of course, if you survive the introduction of B-11 enriched Diborane and BF3 exhausting from the pump system, then there is always the backing pump body damage, itself, and the oil pickup of same.

All could be overcome with money time and a bit of sweat, of course. The government sponsored boys haven't even dabbled in this "wonder fuel" yet. Ever wonder why?

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Steven Sesselmann
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Re: Can a fusor explode?

Post by Steven Sesselmann » Tue Nov 15, 2005 9:18 pm

Point taken Richard, theory and practice are not the same.

In any case I don't think exotic fuels will be needed, the D+D reaction will
burn by itself, given the right conditions.

Steven
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Re: Can a fusor explode?

Post by DaveC » Wed Nov 16, 2005 8:47 am

It has always seemed most plausible to me that the so-called "runaway" episodes are really nothing more than thermally enhanced emission from the negative inner grid.

For the grids made of low melting temp wire, there is practically no chance whatever of a runaway event ocurring, since their melting temperatures are far, far below good thermionic emission temperatures.

Everyone noodling about runaways... ought to doodle with the Richardson Dushman equation using real numbers for the work functions of his particular grid material. The results will be eye opening for most people. You need, Tungsten, or Tantalum operating at about 2500K or higher, to get any significant electron emission. If you use thoriated tungsten wire, you can drop the emission temps by upwards of 1000K and see significant output in the 1400K range.

It seems to me, that if one operates with enough current to heat the grids till they approach the thermionic emission temperature, the assuming the Voltage is high enough to overcome the Space Charge Current limitations of the Child-Langmuir Eqn, then one could get an ever-increasing current and with it ever-increasing (but not Nuclear runaway) Neutron emission, as the grid emits more and more electrons, thus causing the Deuteron density to also increase.

Such a device will run up in current until the Power Supply Voltage drops and shuts things down. If you have a beast of an HV supply, then you could expect to see meltdown.. of the grids, and possibly a hole burned through the fusor shell. A few KW is likely to be enough to do it.

Dave Cooper

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Re: Can a fusor explode?

Post by Richard Hull » Wed Nov 16, 2005 6:20 pm

Dave hit the nail on the head. In most usable supplies, there is current limiting of some sort. In mine, I just have a 30k ohm 200 watt resistor in oil. So, in my system, thermal runaway so increases the desire for current that the voltage nose dives as the limter resistor voltage rises. Thus, I see a reduction of fusion at thermal emission runaway as I slide off the cross sectional curve. Beefy supplies or constant voltage supplies set to very high current limit values, as Dave notes, would see an increase in fusion up to where the supply faults out or you melt something inside the fusor.

These are all practical, real world issues that any real fusor operator sees at every operation session and guards against.

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

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