Nit picking fusion - the reality

It may be difficult to separate "theory" from "application," but let''s see if this helps facilitate the discussion.
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Richard Hull
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Nit picking fusion - the reality

Post by Richard Hull »

I recently received an e-mail questioning one of my FAQ or oft repeated statements about fusion probably beginning at 10 KV, but the amateur would not detect it easily. The upshot is that why didn't I just state that fusion was going on at 10kv. My response...........

Fusion begins at 0 volts. In understanding fusion you have to realize that fusion is not a given due to a fixed rule, nor does it have a starting point. Fusion in deuterium is unavoidable due to simple quantum probability. Quantum tunneling is how fusion is done. The tunneling occurs in pure deuterium atmospheres based on pressure, (fusion fuel density), and temperature, (kinetic energy), gauged by a term called cross section and this is a fake, but workable concept of how big a given deuterium atom appears to another deuterium atom in all of these variable environments and relates to how likely fusion might be.

At zero volts and STP some almost inconceivably small amount of fusion will occur due to quatum tunneling by sheer randomness at a microscopic tiny cross section. Increase the pressure, temperature or input an acceleratory voltage to deuterium ions and the cross section grows and, thus, so does the probability of the quantum tunneling which allows fusion to take place. Fusion will be greater at 1kv than at 0 volts and greater at 5kv and greater still, at 10kv.

As amateurs looking to do fusion and being forced to prove it, The intrumentation used in detecting fusion will determine the acceleratory applied voltage where sufficient proof is in hand to make an unequivocable statement..." I have done fusion. See here, I can show you that I have done fusion."... Theoretically, a 2300psi lecture bottle on a warm summer day is doing fusion. However, can you prove it to me using an artifice of instrumentation? The answer is, of course, no, you cannot.

All such material placed in FAQs is related to only the real world act of demonstrating to a critical audience that you have done fusion at the amateur level. A median response is often necessary based on the average amateur's ability and probability of obtaining sufficient voltage coupled with adequate instrumentation to prove, at some juncture, that they have, indeed, done fusion as a private, self-funded, individual. (No mean feat for the average applicant).

Thus, nothing is set in stone so far as voltages, instrumentation or the level of detectability of D-D fusion to the amateur. There are human condition probabilities here, too. What is the probability that the amateur is ultra-rich, (unlimited instrumentation budget)? What is the probability of the amateur being able to attain fusion acceleratory kinetic energies, (highest voltage at which he can supply useful current). What is the probability that regardless of instrumentalities, the amateur will know how to apply or use them to true advantage,(competently operate the gear to obtain maximum value and confidence in the data.)

A net summation of all of these probabilities, in the case of the average amateur or would-be fusioneer, leads to a general acceptance that he will never do fusion. However, like that weak quantum tunneling, some few amateurs with the "right stuff" will squeak by and come out successful.

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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Chris Bradley
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Re: Nit picking fusion - the reality

Post by Chris Bradley »

Not wishing to be picky with the essential thrust of your point, Richard, which is fundamentally correct, there is still a myth that fusion goes on in an STP bottle. There is no justification for thinking this, although in a rather amusing way it is a self-proving myth because the argument is that neutron rates are below detectable levels, as they well are.

Just to put some numbers against this, consider the barrier 'transparency' to fusion is approximated by Gamow's tunneling factor e^(-SQRT[Eg/E]) {where E is the particle energy and Eg is the Gamow energy ~985[Z1^2].[Z2^2].Mr keV - viz. D+D has an Eg of 985keV}

So, on the basis of the Gamow approximation;

an E of 10keV gives a barrier transparency value of 5 x 10^-5 units
a room temperature E of 0.03eV gives a barrier transparency value of* 3.1 x 10^-2489

If you start with a presumption of a rate of one fusion every 100us from a fusor operating at 10kV, so if you have a 100 bar bottle that therefore carries deuterium, say, 10^7 times as dense as an operating fusor chamber then each neutron will go from averaging once every 100us to once every 100us/((3.1 x 10^-2477)= hugely more than 10^2400 times the age of the universe. That is the definition of 'not going to happen' if ever there was one.

The ratio is so huge that we're talking one fusion in a bottle of deuterium gas once every googles of googles of life-times of the universe. The theoretical half-life of a proton disintegrating into a neutron (10^14 years) is a virtually instantaneous certainty on the same time-scale of probability.

if we went for a more modest, but still 'unmeasurable' value, for example one neutron per hour, we can estimate the electrical field in a fusor that can probably achieve that: This is around 8 orders of magnitude slower than a fusor at 10kV. So the figure of merit is a transparency value of approx, 5 x 10^-13 units. This will therefore theoretically happen at 1,220 V in a fusor.

So there it is. I reckon, based on that rough calculation, that you'll get one fusion in a fusor per hour at ~1200 V applied. You will never be able to detect this neutron, as it will be completely swamped by background neutrons, but you will be fusing.
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Richard Hull
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Re: Nit picking fusion - the reality

Post by Richard Hull »

The upshot is that the there is little point in nit picking theoretical fusion at the amateur scientist, "doer" level. Doing and proving fusion at the amateur level can be nit-picked, as we force the applicant, via examination, to show a full and complete understanding of his power voltage and pressure levels coupled with his use and understanding of his instrumentality. This where it gets very, intensely specific.

There will always be some probability fusion will take place, no matter how remote. My original intent was that we are practical doers and if you expect to do and prove it, then it is instrument, pressure and voltage driven. There is no magic number where fusion can begin, theoretically. There is, however, a number where it can virtually end of course, at the extreme upper end of the scale. Fusion starts to crumble around 2-6mev for D-D as the Oppenheimer-Philips reaction starts to take over lowering the fusion rate as the voltage, (kinetic energy), climbs ever higher.

The important factor for a would-be fusioneer is that there are some hard and fast numbers that can be relied upon where fusion is going just fine and can be detected within the average budget and with various forms of instrumentality at hand. This is a practical, doers website aimed at the self directed amateur scientist and not a theoretical one. A full and complete theoretical understanding of fusion is nice and, for some folks, desirable and satisfying, but is in no way needed or required to do nuclear fusion.

Thanks for the nice mathematical treatment of the theoretical issues. it is important to realize that that most of our fusion within the amateur fusor takes placed between a kinetic energy level of 220 million and 500 million kelvins. Far in excess of collisional kinetic energy levels found in JET or ITER.... Sounds impressive don't it?

Still, it's all so much Gobble-Dee-Goop. Armed with the above figures and 3 pounds, twenty you can get a large cream mocha latte supreme at a London Starbucks and have plenty to talk about as you swill it down.

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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