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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MSimon
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Re: NIF will change perspectives.

Postby MSimon » Sun Mar 02, 2008 1:04 am

Helius wrote:
jmc wrote:.....we should investigate all the different fusion approaches, but I certainly wouldn't advocate abandoning a high performing fusion machine until something that meassurably performed better was found.


The abandonment of other approaches should always be avoided. The highest performers should get the lion's share of the available money, but much may be gained by concurrent alternative approaches. I fear for the Tokamakers, once NIF comes on line and exceeds the metrics of all other approaches, including ITER. NIF experiments will follow so quick, that they will certainly pin down parameters for high Q and, eventually quick repeatability. IEC - polywell and Tokamaks will both be under budgetary threat. I predict good budget flows to the University of Rochester for their inertial confinement research, and also the Hiper project if NIF is as successful as it now seems it will be. Woe be to ITER, woe be to Polywell if the prespective is that only the single most promising approach gets *all* the money.


Polywell is the most promising approach for mobile reactors.
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Postby TallDave » Sun Mar 02, 2008 2:27 am

jmc wrote:Like I said before we should investigate all the different fusion approaches, but I certainly wouldn't advocate abandoning a high performing fusion machine until something that meassurably performed better was found.


I completely agree.

The problem is money. The tokamakkers are saying "we've done what we can do for $100M or $1B. Now we need $10B." I think it makes sense to give Polywell/IEC fusion a shot at the $100M - $1B range to see what it can do there, before we commit 10x that to another tokamak.

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nif fusion

Postby choff » Sun Mar 02, 2008 8:38 am

I'm willing to bet the polywell beats NIF to the development stage if we get positive results from Santa Fe between now and August. At the very least it will beat NIF on size and cost. Also from what I've read on NIF so far it has a way to go before the lasers can be fired often enough to be a worthwhile power source.
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Postby Helius » Sun Mar 02, 2008 1:16 pm

TallDave wrote:
jmc wrote:Like I said before we should investigate all the different fusion approaches, but I certainly wouldn't advocate abandoning a high performing fusion machine until something that meassurably performed better was found.


I completely agree.

The problem is money. The tokamakkers are saying "we've done what we can do for $100M or $1B. Now we need $10B." I think it makes sense to give Polywell/IEC fusion a shot at the $100M - $1B range to see what it can do there, before we commit 10x that to another tokamak.

In all fairness, ITER is primarilly a Europenan effort; We're spending >1B to keep our own US Tokamakkers involved and happy. ITER is the next tokamak to build. I think their wishful thinking is that they may learn enough about confining isotrophic plasma that DEMO reactor might be a somewhat scaled down version of ITER. Good luck on that.
That the world is only spending 10B on ITER is strong evidence that the whole area of Fusion research is grossly underfunded, with the most promising approaches involving non-Maxwellian plasmas being far to short portion of what is funded.
We should also worry that if Dr. Nebel's 1.8M gets spent without definitive evidence of a 'breakthrough' that the whole idea of IEC gets abandonded. If it doesn't work as expected, then why not? Research is still required in this very important set of experiments even if it doesn't pan out as well as we hope.

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Postby MSimon » Sun Mar 02, 2008 1:28 pm

Helius wrote: In all fairness, ITER is primarilly a Europenan effort; We're spending >1B to keep our own US Tokamakkers involved and happy. ITER is the next tokamak to build. I think their wishful thinking is that they may learn enough about confining isotrophic plasma that DEMO reactor might be a somewhat scaled down version of ITER. Good luck on that.
That the world is only spending 10B on ITER is strong evidence that the whole area of Fusion research is grossly underfunded, with the most promising approaches involving non-Maxwellian plasmas being far to short portion of what is funded.
We should also worry that if Dr. Nebel's 1.8M gets spent without definitive evidence of a 'breakthrough' that the whole idea of IEC gets abandonded. If it doesn't work as expected, then why not? Research is still required in this very important set of experiments even if it doesn't pan out as well as we hope.


What would be really nice is to build a series of reactors based on different configurations and see if there is some heuristic that can be applied to determine a set of functional equations for understanding of the operation.

If the BFR doesn't work it might be worth $20 million to find out exactly why.

Deeper understanding of the WB effect would be really good - i.e. what kind of electron/ion/plasma circulation makes it work?
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Postby TallDave » Sun Mar 02, 2008 6:18 pm

Yeah, for $1b you could build pretty good-sized versions of CBFR, Polywell, MIX, and Lerner's focus fusion.

That the world is only spending 10B on ITER is strong evidence that the whole area of Fusion research is grossly underfunded


Definitely.

Zubrin's book has a very interesting graph showing the correlation between oil prices and fusion funding. If that holds, we should see a flood of money pouring into fusion research over the next few years.

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Postby jmc » Wed Mar 05, 2008 2:08 pm

Sorry Helius, I might have been misunderstood. Might only point was that you shouldn't divert money away from tokamaks until a high performing alternative is found. I fully agree with MSimon that unless Nebels WB7 is a complete catastrophy it would be well worth spending up to 20 million to find out and explore its limitations. I would be of the opinion that it is unfair to expect WB-7 to be a 'breakthrough' if your only prepared to spent 1.8 million on it.

The only argument I was putting forward was against the original subject of the thread of discrediting machines whose outperformance is greater than a machine you are proposing. I advocate the approach of pursuing many different options at the same time. Approches that have show more success obvious deserve more funding, but I think the current funding climate literally strangles approaches that are even slightly outside the box and that's certainly wrong aswell. After all we don't just need fusion, we need economic fusion.

I'm pretty sure your wrong about NIF, while the q value of heat produced/Heat absorbed will be greatly in excess of 1 (maybe even over 10) The lasers used to heat the pellet have an efficiency of about 2%, in addition to this, the mechanism of converting the heat to electricity is only about 30% efficient. This means that the plug to socket efficiency of NIF is likely to still be far below 1. Hiper is a more clever device but perhaps less likely to work, if it oes though, it may bring ICF to the borders of someday becoming commercially viable.

If NIF succeeds it won't be the end for tokamaks though, there are massive repeatability issues with laser fusion, the lasers can only fire once an hour when they need to fire 5 times a second th pellets cost thousands of dollars when they need to cost a fraction of a cent. The advantage of tokamaks is ignition really does mean ignition in that the reaction waste alpas from the last pellet of gas puff can be used to heat the fuel from next pellet to be injected, this would allow the beam to be almost turned off completely this isn't the case in laser fusion. All in all tokamaks are still considerably ahead of lasers in the production of a working powerplant. NIF won't change that, though Hiper might.

Tokamaks still have plenty of problems, without superconductors the energy into the magnets will exceed the power from the plasma. Steady state is another massive challenge aswell. Disruptions are also far more catastrophic for tokamaks than would be the case in laser fusion where they don't occur.

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Postby Torulf2 » Sat Mar 08, 2008 12:57 am

There actual is one magnetic fusion with convex b-field. The Levitating dipole.
It use a ringmagnet for get the ions recycling and not hit the magnet in same way the Polywell do with the electrons.
http://psfcwww2.psfc.mit.edu/ldx/

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Postby jmc » Mon Mar 10, 2008 9:02 pm

I thought the levitating dipole had the highest density gradient in the centre and it decreased as you went outward, that bad curvature. Also how are the magnets cooled from the ion flux present in a fusion reactor if they are suspended in mid-air

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Postby MSimon » Mon Mar 10, 2008 9:24 pm

jmc wrote:I thought the levitating dipole had the highest density gradient in the centre and it decreased as you went outward, that bad curvature. Also how are the magnets cooled from the ion flux present in a fusion reactor if they are suspended in mid-air


They have a wonderful set up.

They cool the magnets by conduction for 8 hours and run the machine for a few minutes.

Obviously an experimental device. Quite useful for that since you don't have to consider supporting stalks in your design or simulations.
Engineering is the art of making what you want from what you can get at a profit.

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Postby pstudier » Mon Mar 10, 2008 11:28 pm

jmc wrote:I thought the levitating dipole had the highest density gradient in the centre and it decreased as you went outward, that bad curvature. Also how are the magnets cooled from the ion flux present in a fusion reactor if they are suspended in mid-air


The levitated dipole is similar to the Van Allan radiation belts around the earth with the earth's dipole field to confine it. No plasma in the center of the earth, and very little in the center of the levitated dipole.
Fusion is easy, but break even is horrendous.

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Postby hanelyp » Thu Mar 13, 2008 1:24 am

Torulf2 wrote:There actual is one magnetic fusion with convex b-field. The Levitating dipole.

I'd expect a similar magnetic field from a toroidal discharge, if it could be stabilized. Modified, of course, by the external field that drives the discharge.

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Postby TallDave » Thu Mar 13, 2008 7:30 pm

Helius wrote:ITER is the next tokamak to build. I think their wishful thinking is that they may learn enough about confining isotrophic plasma that DEMO reactor might be a somewhat scaled down version of ITER. Good luck on that.


Yeah, I was somewhat shocked to read that they planned for DEMO to only be 15% larger (linearly speaking) than ITER, yet function continuously at Q=25 and send power to the grid.

http://en.wikipedia.org/wiki/DEMO

Tokamak physics tends to dictate that things get more efficient as they get bigger. Maybe that Q=25, 2GW thermal output is after the expansion noted in the plan.

And of course, that estimate was from 2004, before we knew about things like the edge localized mode problem and God knows what else.

http://www.talk-polywell.org/bb/viewtopic.php?t=427

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Postby jmc » Fri Mar 14, 2008 1:34 pm

Moving from Q=10 to Q=25, is not as large a step as you might think, once alpha particle heating kicks in (at Q =5 it supplies half the heat) you get a rapid increase of Q with only a slight increase in confinement time. If ITER works a tokamak powerplant probably won't have to be very much larger.

The issue with DEMO won't be how much bigger than ITER it will have to be as much as whether the combined actions of the searing plasma, the neutrons, the ELMS and the magnetic stresses simply break it before it runs continously for even a month (let alone ten years). Additionally continous operations using bootstrap current for a fusion grade tokamak plasma is still very much hypothetical and 'long pulse' neutral beams today only last ten seconds or so.



With regards to the levitating dipole experiment, I still don't get how its good curvature everywhere or how you could possibly keep the levitated coils cool in a hypothetical powerplant.

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Postby TallDave » Fri Mar 14, 2008 3:54 pm

jmc wrote:Moving from Q=10 to Q=25, is not as large a step as you might think, once alpha particle heating kicks in (at Q =5 it supplies half the heat) you get a rapid increase of Q with only a slight increase in confinement time. If ITER works a tokamak powerplant probably won't have to be very much larger.

The issue with DEMO won't be how much bigger than ITER it will have to be as much as whether the combined actions of the searing plasma, the neutrons, the ELMS and the magnetic stresses simply break it before it runs continously for even a month (let alone ten years). Additionally continous operations using bootstrap current for a fusion grade tokamak plasma is still very much hypothetical and 'long pulse' neutral beams today only last ten seconds or so.


Yeah, it's not so much the Q=25 that surprised me as much as the 2GW continuous operation (esp as the power out is mostly neutrons). One of the ways to get around those reliability problems is by making it bigger. I suspect they're sugarcoating the estimate a bit there, due to the fact that the expense rises as something like the cube of the size. And of course the estimate's 4 years old now.

They keep finding more problems, so I have to doubt a continously operating net power plant can be close to ITER-sized without some radical advances. It would not surprise me if they come back and say it needs to be 2-4x larger.


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