I am still not sure what the issue is. From what I see, at β=1, you can have either a little VERY hot plasma, a LOT of hot plasma, or somewhere in the middle. Also, it seems folks think that the most beneficial condition for Polywell is a LOT of hot plasma.
So why does chrismb keep harping on the "little VERY hot plasma" condition as proof that Polywell won't work?
Remind me - why 10T field?
Chris is heavily invested in Polywell not working. The rest follows.So why does chrismb keep harping on the "little VERY hot plasma" condition as proof that Polywell won't work?
The MO: Pick a condition (or a set of same) where Polywell is very unlikely to work and use that as "proof" that it is a waste of effort.
From what I gather if Polywell works it will be in a narrow range of conditions where all the competing needs are balanced.
Engineering is the art of making what you want from what you can get at a profit.
I don't follow your reasoning. Why would a 10 Tesla field implies a low Beta. As you said a stronger magnetic field would better contain high energy particles away from the cusps, but this is completely irrelevant to the value of Beta obtained.chrismb wrote:Sorry, you're still missing the point. If you run a small, compact device (Polywell, tokamak, whatever...) at beta=0.01 but you *could* run it at beta=1, then you've got no means to assess the scaling law of the device whilst you're p*ssing around running it at a low beta. All you are doing is floating around in multiple variables. The only way to understand the limit of the device is to run it at its limit then change the boundary conditions. But if Polywell *can* run at beta=1, then WB8 is gonna push out megawatts, because you only need a few kG at beta=1 to confine some real hot plasma - and I mean plasma so hot that it will definitely be unsustainable due to brems.MSimon wrote: Higher density makes for smaller reactors. And for greater internal vs external density. Both useful.
So either Polywell *can do* beta=1, or it can only do what it can only do.
If you use the formula in my pervous post, it reduces to essentially:
Beta=( n (density) * T (temp)/ B (magnetic field strength) ) * constants.
So if WB6 was ~ Beta= 1 at density of ~ 10^13 / cm^3 (=10^19/ M^3) and temp of 10 Kev, then the numbers Bussard quoted for a Demo D-D reactor would also be ~ Beta= 1
Beta=1= 10^19 particles/ M^3 * 10 KeV/ 0.1 Tesla^2 *constant = 10^22 particles / M^3 * ~80-100 KeV / 10 Tesla ^2 *constant.
While the B field increases 100 X and the square of that = 10,000, the product of the density and temperature also increase 10,000 X. The ratio stays ~the same and thus Beta remains ~ 1.
You can argue that such a density could not be obtained, or that other problems would prevent the practical achievement of these conditions, but the argument about Beta conditions being different are completely inappropriate.
Dan Tibbets
To error is human... and I'm very human.
Just my opinion, but I think the value of beta is relevant to energy production.
Given a machine, Is there no way to simply measure the density? Maybe not directly, but indirectly determine density and thereby skirting the question of beta ~ 1? Seems to me that a density measure of the core could be a useful feedback control signal to maintain operation near optimum beta values.
The constants are probably machine dependent and probably need a continuously operating machine, but steady state is achieved rather quickly according to Dr. Bussard, so I bet someone could figure out how to determine density without resorting to elaborate and uncertain math models. Once you know the value of density, adjusting fuel flow and electron beam voltage should allow control of beta. Then pick the value of beta for "best" performance and operate there.
Given a machine, Is there no way to simply measure the density? Maybe not directly, but indirectly determine density and thereby skirting the question of beta ~ 1? Seems to me that a density measure of the core could be a useful feedback control signal to maintain operation near optimum beta values.
The constants are probably machine dependent and probably need a continuously operating machine, but steady state is achieved rather quickly according to Dr. Bussard, so I bet someone could figure out how to determine density without resorting to elaborate and uncertain math models. Once you know the value of density, adjusting fuel flow and electron beam voltage should allow control of beta. Then pick the value of beta for "best" performance and operate there.
Aero
I've clearly not explained what I am saying. This isn't a contest about whether or not polywell will work, it is about whether the current experiments can say anything about scaling.
If a plasma [device] is operating at beta=1 it means that the magnetic field IS balancing the tendency of the plasma to expand due to its heat and density. If it isn't balancing it, and the magnetic field is much higher in excess, then it ISNT at beta=1. A plasma is either AT beta=1, or it isn't. A plasma isn't beta=1 because it COULD BE, but because it IS.
OK, so now if tests are run on a little polywell at beta=1 but the plan is to later ramp up the mag field to a point where it WONT be at beta =1, then the scaling that is interpolated from those findings will be false.
At 10T, this means the outer edge is at 10MeV plasma temp and 1E19 density. But that's insane for the EDGE to be at those conditions. Or let's say it is at 10keV and 1E22, and with the supposed compression factors between the edge and the core, then you're trying to tell me that you are containing a plasma at 10 x atmospheric and that is at 10keV?
IF IT ISN'T IN THOSE CONDITIONS, THEN IT ISN'T BETA=1. It may well not be at beta=1, that's fine. I've no problem with that. But if your smaller test unit was running at beta=1, then all the scaling extraploations are worthless.
So if someone were to say "well, I think the experiments will run at Polywell's max beta, and I reckon that'll be around 0.01 for WB8 and for a power producing variant", well if that were so then I could see the correlation.
But at the moment it's abit like comparing two engines, one is a 8 litre V8 with 7 spark leads missing, and the other is a 4 cylinder 1 litre engine running on all cylinders.... There is no point of scaling that is particularly useful here.... you aren't comparing two scaled machines.
So, can Polywell achieve beta=1, or not? And if so, then why are the operating conditions not ALWAYS going to be at beta=1.
I'd still like an answer to the question [that I said I didn't think I'd get an answer to]: What are the density and temp conditions in the edge supposed to be?
If a plasma [device] is operating at beta=1 it means that the magnetic field IS balancing the tendency of the plasma to expand due to its heat and density. If it isn't balancing it, and the magnetic field is much higher in excess, then it ISNT at beta=1. A plasma is either AT beta=1, or it isn't. A plasma isn't beta=1 because it COULD BE, but because it IS.
OK, so now if tests are run on a little polywell at beta=1 but the plan is to later ramp up the mag field to a point where it WONT be at beta =1, then the scaling that is interpolated from those findings will be false.
At 10T, this means the outer edge is at 10MeV plasma temp and 1E19 density. But that's insane for the EDGE to be at those conditions. Or let's say it is at 10keV and 1E22, and with the supposed compression factors between the edge and the core, then you're trying to tell me that you are containing a plasma at 10 x atmospheric and that is at 10keV?
IF IT ISN'T IN THOSE CONDITIONS, THEN IT ISN'T BETA=1. It may well not be at beta=1, that's fine. I've no problem with that. But if your smaller test unit was running at beta=1, then all the scaling extraploations are worthless.
So if someone were to say "well, I think the experiments will run at Polywell's max beta, and I reckon that'll be around 0.01 for WB8 and for a power producing variant", well if that were so then I could see the correlation.
But at the moment it's abit like comparing two engines, one is a 8 litre V8 with 7 spark leads missing, and the other is a 4 cylinder 1 litre engine running on all cylinders.... There is no point of scaling that is particularly useful here.... you aren't comparing two scaled machines.
So, can Polywell achieve beta=1, or not? And if so, then why are the operating conditions not ALWAYS going to be at beta=1.
I'd still like an answer to the question [that I said I didn't think I'd get an answer to]: What are the density and temp conditions in the edge supposed to be?
chris,
The whole point of going to higher density is to get more reactions per unit time. So density scaling is important. And you know it is possible to apply math to the initial conditions and compare that with experiment to see if the scaling equations for power hold.
Or you could take a given machine and operate it at various field strengths and drive voltages to check.
The whole point of going to higher density is to get more reactions per unit time. So density scaling is important. And you know it is possible to apply math to the initial conditions and compare that with experiment to see if the scaling equations for power hold.
Or you could take a given machine and operate it at various field strengths and drive voltages to check.
Engineering is the art of making what you want from what you can get at a profit.
yerrrssss.... and????...MSimon wrote:chris,
The whole point of going to higher density is to get more reactions per unit time.
This is non-sequitur. this is my point. You cannot say whereabouts you are floating around this multi-fatoral map whilst you don't have a fixed beta operating condition, and 10T is gonna be waaay off that map if polywell can actually achieve beta=1, as has been claimed.MSimon wrote:So density scaling is important.
Just answer the darned question - give me some numbers, here: Outer shell; where Ti drops to zero (supposedly), what are ne, ni, Te and the mag field there.
This is an absolutely drop dead simply question, and if this isn't known then there can be no objective knowledge of this thing, it must all be plain ol' guess work and confangulabulation.
Bussard stated that there is an upper limit to density.
Above that limit the mono-energetic assumption breaks down and, even with 'annealing', the plasma essentially thermalises as there are too many 'low energy' ion collisions occurring before a fusion event (high energy collision).
If there is an upper limit for density (based on fusion conditions), there is an upper limit on pressure and thus an upper limit on edge magnetic field strength.
There's your anchor.
Above that limit the mono-energetic assumption breaks down and, even with 'annealing', the plasma essentially thermalises as there are too many 'low energy' ion collisions occurring before a fusion event (high energy collision).
If there is an upper limit for density (based on fusion conditions), there is an upper limit on pressure and thus an upper limit on edge magnetic field strength.
There's your anchor.
You cannot say whereabouts you are floating around this multi-fatoral map whilst you don't have a fixed beta operating condition,
This may surprise you but we can use mathematics to calculate equivalences. Of course extrapolation is iffy. But interpolation should be possible.
Engineering is the art of making what you want from what you can get at a profit.
Ah! A post that seems to begin to understand what I am saying!icarus wrote:Bussard stated that there is an upper limit to density.
Above that limit the mono-energetic assumption breaks down and, even with 'annealing', the plasma essentially thermalises as there are too many 'low energy' ion collisions occurring before a fusion event (high energy collision).
If there is an upper limit for density (based on fusion conditions), there is an upper limit on pressure and thus an upper limit on edge magnetic field strength.
There's your anchor.
If you remember when/where this dialogue was said, the point I am trying [failing] to push at may be embedded in that.
Tom Lignon wrote about it:
http://www.classicalvalues.com/archives ... d_u_1.html
Maybe they were misquoting Bussard?
MSimon blogged it:It is important to know that the process Dr. Bussard describes will only work over a fairly narrow range of density. If the density is raised too far, the number of collisions occurring in the wrong places in the machine will, indeed, cause it to thermalize, but if the density is too low, the reaction rate suffers.
http://www.classicalvalues.com/archives ... d_u_1.html
Maybe they were misquoting Bussard?
Isnt this the famed carburetor analogy?icarus wrote:Tom Lignon wrote about it:
Maybe they were misquoting Bussard?It is important to know that the process Dr. Bussard describes will only work over a fairly narrow range of density. If the density is raised too far, the number of collisions occurring in the wrong places in the machine will, indeed, cause it to thermalize, but if the density is too low, the reaction rate suffers.
I like the p-B11 resonance peak at 50 KV acceleration. In2 years we'll know.