Quantum world views - It's what make fusion happen

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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Re: Quantum world views - It's what make fusion happen

Post by Richard Hull » Thu Nov 12, 2020 2:09 pm

Nice article Dennis. Thanks. For years the lifetime was on the order of 20 minutes. Recently in some articles it was 10 minutes. Now it is heralded around 15 minutes. The snag as mentioned is that in one test two absolute measurements are required. We know that an absolute measurement of the precise number of neutrons emitted from ~10e6 fusions is just not possible. When looking for precise lifetimes of this neutral particle, the demanded two absolutes may be a bridge too far.

The neutron has captivated me since college. Protons and electrons are just there, but not one single atom beyond hydrogen can't exist without the neutron. The neutron is the key to the nucleus and all elemental atoms in our universe. Many questions, many theories, lots of experiments but the neutron's secret remains hidden. I have always and still believe the strong force is found in the neutron and the weak force is electrostatic in nature due to the hyper short sub-fermi distances in the nucleus. After all, they often call it the electro-weak force.

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Fusion is the energy of the future....and it always will be
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Dennis P Brown
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Re: Quantum world views - It's what make fusion happen

Post by Dennis P Brown » Thu Nov 12, 2020 3:04 pm

Your most welcome. And you are correct: the weak force is related to the electrostatic - at high energies, those two forces become one and the same. At lower energies, they differ as does water vapor does to water - same thing (electrostatic) but diferent phase (range of action.) So while the weak force is short range (though far stronger than the electrostatic in that region) it is, as you point out, due to its restriction to nuclear distances. Neutrons do, in fact, as I understand/recall, play a major factor in the strong nuclear force (due to gluon leakage - fall off range.)

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Re: Quantum world views - It's what make fusion happen

Post by Colin Heath » Sat Jan 23, 2021 7:43 pm

Fantastic food for thought and I wonder if my simplistic understanding is correct?

All the fusion we know of / understand occurs via quantum tunnelling. And if that’s the case, the search for much higher temperatures and more energy doesn’t really further fusion.

Is it correct the only way we will achieve break even is with a scaled version so large it won’t be practical?

Are there ways of influencing an increase in quantum tunnelling other than increasing the amount opportunities for it to occur (scale).

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Re: Quantum world views - It's what make fusion happen

Post by Liam David » Sat Jan 23, 2021 8:34 pm

The tunneling probability is directly related to the nuclear kinetic energies through the Gamow factor, which scales as P ~ exp(-sqrt(1/E)). Increasing the grid voltage increases the deuteron energies and the effective temperature (E ~ kT), thus raising the probability that a given collision will cause fusion.

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Re: Quantum world views - It's what make fusion happen

Post by Colin Heath » Sat Jan 23, 2021 10:29 pm

Thanks Liam,

Are we talking collisions in the sense of colliding or through tunnelling? I was under impression that trying to overcome Coulomb barrier was near impossible and almost all fusion is now believed to be from tunnelling.

Hence why the sun works because of sheer number of chances for tunnelling and as such, we couldn’t scale to what’s required on earth.

Very interesting subject and looking forward to being informed and trying to inform myself.

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Re: Quantum world views - It's what make fusion happen

Post by Richard Hull » Sat Jan 23, 2021 10:44 pm

The deuterons rarely collide physically. In the quantum world, the particle's barrier to the strong force overcoming the electrostatic repulsion varies. As such, a full on slam dunk hit at our energies is a game of probability more or less. At our level of operation, we are relying on a hit or even a near pass by at the same time the tunneling possibility is at a maximum for one or both particles as they approach. This goes back to energy as stated above. For targeting in our mechanical brains more energy means the quantum tunneling target size of the particles swells ever larger and larger as the kinetic energy of the particles increases.

In the Oppenheimer-Phillips reaction, there is so much energy that the deuterons are torn apart and will never fuse. So there is also such a thing as too much energy.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
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Re: Quantum world views - It's what make fusion happen

Post by Colin Heath » Sun Jan 24, 2021 6:20 pm

Thanks Richard,

That makes sense to me with your explanation along with Liam’s.

More learning to do, much more.

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Re: Quantum world views - It's what make fusion happen

Post by Richard Hull » Sun Jan 24, 2021 11:17 pm

There is the Lawson criteria....Read up on this for details. Remember energy is related to temperature. In solid matter or in a dense plasma there are constant collisions. Power fusion demands a very dense plasma, totally contained at very high particle energies. The containment is always the issue. As power fusion begins, the huge fusion energy output heats the dense plasma which wants to expand and cool. We do not want it to cool. Thus, more containment is demanded. In the real world on earth, the containment is always found to fail. The plasma expands, and this burns or otherwise damages the walls of the reactor. The debris then kills the fusion event. The power phase used to last a fraction of a second. Better containment moved this to a second or more. The latest can last a few seconds before it craps out.

Needless to say, in the production of real power for electricity we have grown use to power plants running smoothly 24-7-365 without real issues. 3 to 30 seconds of powered run time is kind of a total fail.

The fusor is a thin, totally lossy plasma where only a very few of the collisions occur at the desired fusion energy of the applied voltage. The deuterons, be they multi-pass, acceleratory recirculations or one-shot passes before ion death, only fuse with great rarity related to their number. Still there are enough fusions in the best fusors to create 1 to 6 millions fusions each second! This produces enough neutrons to make the reactor a nice experimental source of neutrons. There is no hope by any artifice where a fusor can produce power. It can only do massive power losses.

Make sure you read every FAQ in this forum if you wish to gain knowledge of how the fusor does fusion and on fusion in general. When talking fusion energy output of the fusor, this FAQ is a must see and to understand.

viewtopic.php?f=42&t=13284

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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Re: Quantum world views - It's what make fusion happen

Post by Justin Fozzard » Mon Jan 25, 2021 12:51 pm

I find it very interesting and surprising that it is possible to trap neutrons and in a variety of ways.

Here is a rather good presentation about neutron trapping and a couple of papers on the subject:

Huffman 2000 Magnetic Trapping of Neutrons.pdf
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Re: Quantum world views - It's what make fusion happen

Post by Richard Hull » Mon Jan 25, 2021 5:03 pm

Great URLs! Thanks Justin. I have always been amused that the neutron drops just like a rifle bullet in a gravitational field. Acceleration in a gravitational field for a neutron is no different from a lawn dart. The issue is how far can it go based on its velocity normal to the field. Ultra cold neutrons make good candidates, but getting them cold enough in a beam to work with is like herding cats in a violent thunderstorm.
Good controls in any experiment regarding lifetime measurements is key.

I always wondered if the decay is purely exponential with a fixed half-life the instant they are free or does their velocity relative to us in measuring them make their life times or "half-lives" a matter of relativistic time dilation. Relative to themselves the decay may be instantaneous. A single coupled proton-electron pair, extra-nuclear, would have a tremendous coulombic repulsive force.

Based on the many methods used in magnetic confinement and the many analyzed and reported systematic effects, what role in altering our perceived and measured lifetimes might these have? Just because we force collected near zero energy neutrons into a bottle under intense magnetic fields, the known electrostatically lobed neutrons may view themselves as in a friendly but very weak inter nuclear environment.

Issues abound here and might be lumped under systematic effects yet to be understood.

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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