Fusion Discussion on Reddit

If polywell fusion is developed, in what ways will the world change for better or worse? Discuss.

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Fusion Discussion on Reddit

Post by mattman »

Hello Guys,

Anyone out there a redditor? Check this out:

http://www.reddit.com/r/askscience/comm ... ar_fusion/

Can someone from this forum please go on reddit and explain the general community about the merits of the polywell. Here is an argument you can use:


1. We may be able to reflect the x-rays back into the center - recycling the losses. Gold or lead will do it but they melt at 1337 and 600 K respectively. If the reactor temperature is to high, that idea becomes less likely. We will need a curved chamber to reflect the x-rays back in.

2. Reactor temperature: Rider made a strong case the biggest variation in temperature would be 5%. In his 95 paper, he uses general volumetric equations to do this. He never measured the actual temperature inside a Polywell. He estimated from theory. It is not clear he used the right equations.

3. Rider argues the cloud will randomize in particle energies - going to a bell curve, fine. But he never examined in randomization in space. There is a chance the plasma has some kind of structure. His idea for the cloud in the center: a core, a mantle and an edge, may be flawed. People have suggested that the electron cloud has its own magnetic field, rejecting the externally applied field, and pinching off the loss points. The electron cloud may go diamagnetic. This phenomena may generate a structure. People argue that this, forms a clump of ions in the center. The counter is that the charge separation will form a plasma instability, swirling around, destroying the structure. The relative importance of each of this phenomenon is unknown. These are all open questions.

4. The new polywell designs emphasize electron recirculation. Lots of space, no metal surfaces. Rider commented in his thesis abstract that efficient recirculation was key for this device to work. How efficient will be needed and, how efficient we can achieve, are still unknown.

5. The Polywell may have a resonance condition. It is a complex system. The parameters include: the ions in the center, the rate of ion injection, the electrons in the center, the rate of electron injection, the charge on the ion, the magnetic field strength, the energy of injection for the ions and the geometry. Raise one rate and you may get more X-rays, but more fusion. Lower another and you get a smaller plasma cloud in the center, but more efficient recirculation. The system probably has dimensionless numbers, so we can vary the variables in tandem and simplify analysis.


The hidden assumption in Rider's work is that you must go big to get fusion. If we are locked onto the big expensive machine route, we will never get there. Over the past 50 years, there have been 177 tokomaks either, built, planned or decommissioned, worldwide. If the idea was good, you would have expected success by now. The "big" assumption is also embedded in the Lawson criteria. John Lawson assumed that you had to contain plasma and heat it up for fusion. He estimated 30 million degrees for DT and 150 million for DD. The Fusor can do fusion at room temperature, with cheap equipment. Of course, the Fusor did not exist when Lawson came up with his ideas. If Lawson is right, then we are either containing for a long time (Tokomak), or compressing to a high pressure (ICF). The goal of the National Ignition Facility is to get the average plasma temperature above 10 KeV. Meanwhile the Polywell can get ions to 10 KeV, using a 10 Kv well. It would not take many electrons to reach that voltage and I bet you a million dollars that will require far less energy than firing giant lasers.

Compare this to the early attempts to fly. In his book: "Progress in Flying Machines" (1894), Chanute, shows us that modern attempts to fly went back more than 60 years before the Wright brothers. There were dozens of distinctly different designs attempted, by lots of different people. Goofy, even silly ideas, were tried. The public barely noticed this and generally assumed that it was impossible. Right now, fusion is viewed as impossible and the public barely notices our efforts. The reality is, the fusion machine must get smaller, simpler and cheaper if we are to succeed. Look at the development of the computer. The early computers were the size of whole rooms. The computer needed to get smaller, simpler and cheaper to advance. Smaller and cheaper means more people can try different ideas and innovations can happen faster. I am sorry to say, but one of those little guys is going to get there first. The big scientists will clamor over one another to shout: Hoax! Hoax! But this time, they will be wrong.

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Post by hanelyp »

The Lawson criteria is a statement relating how long energy must be contained within the reactor to plasma density for fusion output to pay back the energy invested. In this form it applies to the polywell. It can also be applied as a relation between fusion energy production and leakage, relevant to ignition.

The Rider thesis, as I understand it, is based on theory developed for devices like the tokomak, which is wholly insufficient for a device where electric potentials comparable to particle energy is a key feature.

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Post by ladajo »

Rider's biggest flaw was his distribution assumptions.
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)
What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)

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