Let us start discrediting tokamak fusion. Wrong Shape.

Discuss ways to make polywell research more widely known or better understood. Includes education and outreach.

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jmc
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Post by jmc »

When I said power I meant heat power emitted from the neutrons. If coolant was pumped trough the blanket of ITER and if that coolant was fed into an electricity generator, then perhaps even taking all the inefficiecies of powering the neutral beams, the central solenoid and turning the resulting heat into electricity etc. then for a few minutes every day/week ITER might be able to churn a few net megawatts into the grid. The basic design of ITER is essentially that of a functional prototype reactor for a future fusion power plant, its just people haven't bothered putting coolant into the blanket in and feeding it into an electric generator for several reasons.

1) The capital costs to install such a system would be considerable

2) The length of an ITER shot would be about 15 minutes, that 15 minutes of electrical power per day so the income of selling that to the grid would not pay be the installation costs of such a generating system.

and most importantly:

3) Installing such a system would be liability, just another thing that could go wrong increasing maintenance time while decreasing valuable experimentation time for optimising plasma performance.

4) Installing such a system would take up valuable space reducing the number of viewing ports and peoples ability to diagnose and evaluate the conditions of high performance burning plasmas allowing them to be replicated.


ITER will be a machine that will occassionally and intermittently be capable of producing fusion reactor grade plasmas. Researchers need to be able to do this routinely before it will be worth their while to a an electrical generation system to the plans.

rexxam62
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Post by rexxam62 »

I think MSimon is correct on the policy front for one reason. Because Dr. Bussard himself have stated that if there is a conspiracy against IEC Polywell fusion it is comming from the Tokamak people and not the oil industry.

So lets keep cool heads till the firsts tests are done and the engineering issues are worked out. If the tests and engineering turns out to have provable merit then we can come at them with hostility.

Revenge is a dish best served cold
-Pierre Ambroise Francois Choderios de LaClos

jlumartinez
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Post by jlumartinez »

Physicists have been working since the 1950s on making better "magnetic bottles". Magnetic confinement of plasma has been described as holding jello (the plasma) with rubber bands (the magnetic field).

In Tokamaks and related machines, magnets push on the plasma from the outside, while Polywell pull on the plasma from the inside. It will pull on the plasma, just as gravity pulls down on Jell-O sitting in a bowl.

Polywell is similar in that way to the Sun, where the plasma is confined from the inside due to the gravity force, because it creates a central force to confine the ions generated by the potential well.

As confinement scheme Polywell is quite superior to Tokamak. The key is to control electron losses( in order to increase the electron lifetime in the machine). This seem to be the major finding in WB-6.

jmc
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Post by jmc »

Plasma physics is filled with ideas that have worked on paper but when you put them together in practice some new physics crawls out of the woodworks and makes the whole thing alot harder.

In actual fact when the tokamak concept was first developed neoclassical theory suggested that one a few metres in diameter (about the same size as Bussards proposed Polywell fusion reactor infact) but then turbulence kicked in and this meant the device had to be made bigger.

There's nothing to say the Polywell will not face similar problems. At presen tokamaks currently produce 10 trillion times more neutrons even than the figure which Bussard claims and Bussards figures are based on 9 neutron counts in total all from the counter closest to the device (he placed other counters further away but they did not register anything) the neutron counts which tokamaks produce on the otherhand are well-established and repeatable.

On paper the idea of concentrating plasmas to a single point looks promising and it should be explored, but a wealth of evidence suggests that tokamaks will eventually work if you make them big enough, in the case of Polywells the evidence is scant.

While the physics of the Polywell look good on paper it might be a good idea to have a repeatable experiment capable of routinely producing a detectable level of neutrons that are well above the noise before you go around the place scrapping the tokamak programme just yet.

MSimon
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Post by MSimon »

jmc,

An excellent point.

Let he who is without doubt cast the first stone. (BTW to be without doubt is unscientific).

http://www.classicalvalues.com/archives ... ot_sc.html

There is lots we don't know and lots that could go wrong and even lots that we do "know" which is wrong.

We should be humble until we have a power delivering reactor.

jlumartinez
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Post by jlumartinez »

Of course that ITER at the end will work. I am sure that a reactor 10 meter of diameter and so many facilities to fill a whole building and with last generations technologies will get breakeven.

But if we want a cheap energy source for the third world Polywell is a much feasible solution. I can not imaging to install many ITER size reactors in the heart of Africa. This is the great benefict of Polywell in comparation to Tokamaks: if Polywell works it will provide a cheaper and easier way to generate electricity and to distribute it around the whole world.

scareduck
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Post by scareduck »

I don't understand this thread at all.

jmc
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Post by jmc »

I'm sure there are plenty of ten metre fusion devices that wouldn't work if you built them from scratch. One reason ofcourse that we are so confident that the tokamak will work eventually is because it has 5 billion (or is it 50?) dollars and 50 years of research and fine tuning behind it.

That is probably a major reason why it is he most successful, reliable and highest performing fusion device to date.

I still maintain the tokamak approach should be continued until or unless another device should outstrip it in actual meassured fusion performance.

The reason fusion is in the mainstream media and even on the table when people consider the energy problem is because of the solid well meassured results that have come out of JET. I believe even Bussard saw for a while the advantages of Tokamaks as a device for producing impressive fusion results that would keep people interested in fusion as a stop-gap until a better idea came along. Even if you look at Rostocker's paper you can see he uses evidence from the transport of fast neutral beam particles in Tokamaks to support his theories.

I don't believe that tokamaks should eat up all the fusion funding at the expense of every other fusion concept but neither do I believe that the best performing fusion idea to date should be scrapped. We shouldn't trade meassured performance for projected performance, especially in an area where the science is as unpredictable and surprising as it is in plasma physics.

We should keep the tokamak programme, perhaps giving it 50% rather than 90% of the total magetic fusion budget and spend the remainder on other promising concepts like the polywell, the polywell doesn't need that much funding anyhow, so we don't need to close the tokamak programme down, we just need to stop it from strangling everything else. If anything the total fusion budget should increase rather than having the tokamak budget go down.

Whether or not ITER will solve the world's energy problems, running the first fusion reactor that can produce net energy, is likely to lift the whole fusion programme into the realms of credibilty, not just tokamaks, (perhaps in the same way the wright brother's helped helicopters as well as aeroplanes by proving heavier than air flight to be possible).

If someone can show me neutron yields that proves some other concept has a far better chance of success than tokamaks then I would gladly advocate a diversion of tokamak funding towards it. But while we're still in the realms of conjecture, discrediting rival fusion concepts will only damage the fusion programme as a whole.

If you were a layman who had didn't know a tokamak from a reversed field pinch and you saw a load of fusion scientists telling each other how their rival ideas would never work, and when they advocated their own ideas they had know experimental evidence to back them up, what would you think? Would you think fusion as a whole is a concept worth pursuing?

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Post by MSimon »

If you were a layman who had didn't know a tokamak from a reversed field pinch and you saw a load of fusion scientists telling each other how their rival ideas would never work, and when they advocated their own ideas they had know experimental evidence to back them up, what would you think? Would you think fusion as a whole is a concept worth pursuing?
Forty years
Engineering is the art of making what you want from what you can get at a profit.

jmc
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Post by jmc »

Forty years of steady progress and improving performance.

scareduck
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Post by scareduck »

In one of the other threads, Keegan quoted an excerpt from Robin Herman's wonderful Fusion: The Search For Endless Energy. In that book, the author writes that Robert Hirsch made a similar complaint, denouncing the tokamak in a 1985 speech to the American Nuclear Society. The carping from the tokamak physicists was loud and bitter:
"[Hirsch] is a man who thinks [fusion] has to be in this century," said [Hans-Otto Wuster, director of JET]. "How does he teach nature that?"

One researcher at Princeton had a typical reaction:
Hirsch took the science out of the program to begin with. Scientists cringed in the 1970s when Hirsch promised a viable reactor by the year 2000 with his Madison Avenue technicolor viewgraphs. Now he has the gall to say 'You haven't delivered on what you promised.' It's what he promised. He says put tritium in TFTR. Get it over with. It's really infuriating.
I don't see denunciations of ITER as being politically helpful. In the absence of a systemic rebuttal to Rider and Nevins, the physics of Polywell are just as suspect as those of the tokamak guys.

jmc
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Post by jmc »

Its not just that. Polywells or other fusion concepts might well turnout to be better than tokamaks eventually. Bussard's claim of getting it done in the next five years is highly suspect IMO. I'm not sure the is a quick way of getting nuclear fusion, the reason I think this is because fusion plasmas are many body systems chock-a-block full of free energy and are thus almost inherently unpredictable. We can design extremely complicated microchips on paper and when we build them they work due to the fact that every single transistor is almost totally predictable.

Plasmas on the otherhand are completely numerically intractable unless you put in somekind of simplyfying assumptions (kinetic theory MHD) etc. and even then the results are usually analytically insoluable. If you want an analytic solution to a plasma infact, you often have to incorporate so many assumptions into the formula that it no longer properly represents the system you are interested in.

As a result the development in fusion research is very much based on trial and error, working on a concept gettting it slightly wrong, correcting it, fine tuning it etc., etc., the simulations describing plasma systems are also based on trial and error, make a set of simplistic assumptions, benchmark them against experiment, if they don't work add another term, benchmark against experiment etc., etc., this process can take decades, even forty years.

If the Polywell produced commercial power in fifteen years it would be a miracle, if it produced commercial power in thirty years we would be lucky. Its likely to be a slow grind getting it to work, a grind worth engaging in for the prize of fusion energy, nonetheless.

But in the meanwhile the ITER/DEMO path to fusion will provide a great incentive for people to do research into materials that can withstand neutrons and resistant material for plasma facing components whether or not the final machine will be economical or not. The kind of neutron fluences at 17MeV in a fusion reactor are unique to this planet. There is no other experiment that can produce those kind of conditions in terms of neutron flux or power flux at fusion plasma densities.

What if we abandon the tokamak programme for Polywells instead? What if we find all sorts of unanticipated problems and it takes forty years to build a Polywell that produces net power? At this point we might decide we suddenly have to do all sorts of work on materials that can withstand high plasma heat fluxes as well as neutron bombardment (assuming the Polywell is DT). At this point we'd have wished we had kept the tokamak programme going so that all the materials work had already been done.

While I don't agree with tokamaks strangling all other fusion programmes in terms of funding, I do believe that they should be continued until another kind of fusion can overtake them in measured performance.

Roger
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Post by Roger »

jmc wrote:

In actual fact when the tokamak concept was first developed neoclassical theory suggested that one a few metres in diameter (about the same size as Bussards proposed Polywell fusion reactor infact) .
I must quibble.

Image

The Russian T-3 (circa '67 to '73) is much larger than WB-6


Image

The Russian T-1, about 2/3rds size of T-3.
in the United Kingdom, where Thomson and Blackman, of the University of London, filed a patent for a fusion reactor in 1946.
http://www-fusion-magnetique.cea.fr/gb/ ... orique.htm
In 1946 Thomson and Blackman were thinking on the scale of 1.3 meters major radius. WB-6 was .3m.
I like the p-B11 resonance peak at 50 KV acceleration. In2 years we'll know.

MSimon
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Post by MSimon »

scareduck wrote:I don't see denunciations of ITER as being politically helpful. In the absence of a systemic rebuttal to Rider and Nevins, the physics of Polywell are just as suspect as those of the tokamak guys.
Depends on what you mean by systematic.

They have been rebutted and there are at least two physicists willing to put their own efforts on hold to give the BFR a shot. That should count for something.

There is no way to prove Dr. B wrong beyond a reasonable doubt without doing the experiments.

The question is: for fusion do we want to spend $200 million a year for .05 completed experiments a year or should we divide that up and do 5 small and one bigger one a year?
Engineering is the art of making what you want from what you can get at a profit.

MSimon
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Post by MSimon »

jmc wrote:What if we abandon the tokamak programme for Polywells instead? What if we find all sorts of unanticipated problems and it takes forty years to build a Polywell that produces net power? At this point we might decide we suddenly have to do all sorts of work on materials that can withstand high plasma heat fluxes as well as neutron bombardment (assuming the Polywell is DT). At this point we'd have wished we had kept the tokamak programme going so that all the materials work had already been done.

While I don't agree with tokamaks strangling all other fusion programmes in terms of funding, I do believe that they should be continued until another kind of fusion can overtake them in measured performance.
If we find out lots of unanticipated problems in BFRs, we can solve them on a small budget - say we have to build a new type WB-100 every year. That will run us $200 mil a year (assuming rush jobs and small auxiliary test reactors).

To do a new ITER every year is not even possible - let alone doing it on a budget of less than $20 bn a year.

Plasmas self organize. Do we want to build reactors that are based on enhancing that natural self organizing tendency? Or do we want to build reactors that depend on opposing that natural tendency?

As to roll out: I can imagine a program that could deliver a working reactor to a Navy ship in 4 years. If we don't mind the waste of stopping a high velocity program if we hit a serious snag.

One way to cut the time required is to run the program on a 24/7 basis. Another way is to build lots of vacuum chambers so experiments can go on while new set ups are being fitted to one of the idle chambers.

I could see a BFR industry producing 1,000 100 MW jobs a year within 7 years of the announcement of WB-7 results - if further efforts are warranted and the money is there.
Engineering is the art of making what you want from what you can get at a profit.

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