Actual Polywell News!

Point out news stories, on the net or in mainstream media, related to polywell fusion.

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Robthebob
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Re: Actual Polywell News!

Post by Robthebob »

http://en.wikipedia.org/wiki/Helically_ ... Experiment

http://scholar.google.com/scholar?hl=en ... 1&as_sdtp=

Any donut machine (maybe more types of machines) that has a significant enough pressure gradient has bootstrap current.

you dont live in the states and arent in the in circle, so you dont know, but it's fact. It's not billions either, maybe on iter, and a lot of the fusion budget in the states is going to ITER. Currently, its around 330 million per year. It's all politics, yes they're not doing it the right way and they're spending a lot of money on it, that's how it is.

It has to do with history. When Reagan cut fusion budget to 1/4, just about everything other than toks and beam compression went away. Also issues with technology back then, they couldnt make precise enough machines, and 3D coils need precision. That was solved around the 90s, they wanted to build a stellarator at Princeton, but shit happened.

Listen, you can pretend like you're a hot shot and know all about donut machines, and I'm just gonna call you on your BS. I'm going to school for this shit, so dont even give me any nonsense. You want an response to streaming instability, I gave you one, you want an response to why toks arent good but people still build and study them, I gave you one.
Throwing my life away for this whole Fusion mess.

chrismb
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Re: Actual Polywell News!

Post by chrismb »

http://www.researchgate.net/publication ... 36255f.pdf

The impact of the bootstrap current is investigated on the equilibrium properties of a two-period quasi- axisymmetric stellarator reactor with free boundary and on the corresponding ideal magnetohydrodynamic sta- bility properties. Although the magnetic field strength B spectrum is dominated by a m/n ? 1/0 component, the discrete filamentary coils trigger some small-amplitude symmetry-breakingcomponentsthatcandisturbthequasi- symmetry of B. Finite b causes the plasma column to shift outward in the absence of bootstrap current. With a self-consistent bootstrap current in the 1/n regime, the plasma becomes more elongated and more distorted in the horizontally elongated up-down symmetric cross sec- tion. At b ? 3.25%, the plasma can be restored to its near-vacuum shape with the application of a vertical field with coil currents 20% of those of the modular coils, but at the expense of a significant mirror component in the B-field spectrum. The bootstrap current causes the rotational transform i profile to increase above the crit- ical resonant value (ic?1/2 for b?1.1%) and combines with the Pfirsch-Schlüter current to destabilize a m/n ? 2/1 external kink mode for b ? 1.8%.

Joseph Chikva
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Joined: Sat Apr 02, 2011 4:30 am

Re: Actual Polywell News!

Post by Joseph Chikva »

Robthebob wrote: but that doesnt have any ohmic current in it though, which can be wise, because ohmic current confinement cant be steady state.
And please define what do you mean saying "ohmic current"? Iduced current?
As Ohmic heat is produced by any current if there in conductor (plasma donut in our case) is a non-zero resistivity - regardless to that will that current be driven by gradient or induced field.

And does minutes order confinement time not allow us to say that TOKAMAKs are steady (stable) enough?
You need more stable? Or what do you need?

Joseph Chikva
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Joined: Sat Apr 02, 2011 4:30 am

Re: Actual Polywell News!

Post by Joseph Chikva »

chrismb wrote:http://www.researchgate.net/publication ... 36255f.pdf

The impact of the bootstrap current is investigated on the equilibrium properties of a two-period quasi- axisymmetric stellarator reactor with free boundary and on the corresponding ideal magnetohydrodynamic sta- bility properties. Although the magnetic field strength B spectrum is dominated by a m/n ? 1/0 component, the discrete filamentary coils trigger some small-amplitude symmetry-breakingcomponentsthatcandisturbthequasi- symmetry of B. Finite b causes the plasma column to shift outward in the absence of bootstrap current. With a self-consistent bootstrap current in the 1/n regime, the plasma becomes more elongated and more distorted in the horizontally elongated up-down symmetric cross sec- tion. At b ? 3.25%, the plasma can be restored to its near-vacuum shape with the application of a vertical field with coil currents 20% of those of the modular coils, but at the expense of a significant mirror component in the B-field spectrum. The bootstrap current causes the rotational transform i profile to increase above the crit- ical resonant value (ic?1/2 for b?1.1%) and combines with the Pfirsch-Schlüter current to destabilize a m/n ? 2/1 external kink mode for b ? 1.8%.
It is easy to insert in google search window two key words and then to push search button.
But this paper is only the proposal of stellarator and is not experimental results ever done.
Bootstrap currents also at first were observed in TOKAMAKs.
As beam driven current. Though RF heating also creates gradient thus also drives current.

Joseph Chikva
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Re: Actual Polywell News!

Post by Joseph Chikva »

Robthebob wrote:Any donut machine (maybe more types of machines) that has a significant enough pressure gradient has bootstrap current.
Right when has has a significant enough pressure gradient.
Now please inform which earlier stage (for example C-series) stellarator had and when and what machine such current was considered as confinement improvement factor?
Robthebob wrote:you dont live in the states and arent in the in circle, so you dont know, but it's fact. It's not billions either, maybe on iter, and a lot of the fusion budget in the states is going to ITER. Currently, its around 330 million per year. It's all politics, yes they're not doing it the right way and they're spending a lot of money on it, that's how it is.

It has to do with history. When Reagan cut fusion budget to 1/4,
You should understand that neither machine is ideal but when I see you are admitting that:
Robthebob wrote:Toks are easier to build, cheaper, .....
and at the same time they provide enough (acceptable) confinement, politics has nothing to do with this issue. People only count money.
All the more any really conducted experiment and not theoretical reasonings showed that at comparable parameters toks always were more stable.

chrismb
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Re: Actual Polywell News!

Post by chrismb »

http://aries.ucsd.edu/raffray/publicati ... mabadi.pdf
In a stellarator, most of the confining field is produced
by external coils (the poloidal field is generated by
the external coils as well as the bootstrap current). The
absence of a large externally driven plasma current leads
to many attractive features: Stellarators are inherently
steady state, stable against external kink and axisymmetric modes,
and resilient to plasma disruptions.
The ARIES-CS reference plasma, N3ARE (Fig. 3),
is an NCSX-like configuration with three field periods
and has a major radius of 7.75 m and a plasma aspect
ratio of 4.5. The configuration has excellent quasiaxisymmetry,
as measured by the effective helical ripple, Eeff
(Eeff , 0.6% at LCMS and ;0.1% in the core region).
The profile of the ARIES-CS rotational transform at b
5% is shown in Fig. 7. The shaping of the plasma results
in a vacuum rotational transform from ~0.4 to ~0.5. The
plasma current (bootstrap current) is 4 MA, which raises
the rotational transform to ~0.7 near the plasma edge.

Joseph Chikva
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Re: Actual Polywell News!

Post by Joseph Chikva »

The statement of the first quote:
chrismb wrote:The absence of a large externally driven plasma current leads
to many attractive features: Stellarators are inherently
steady state, stable against external kink and axisymmetric modes,
and resilient to plasma disruptions.
Wrong statement. Not yours but developers'.
Let's compare comparable sizes and field strength TOKAMAK and Stellarator.
From one side let's consider JET TOKAMAK with:
Major radius --- 2.96 m
Minor radius --- 1.25-2.1 m
On-axis field -- 3.45 T

And from another - Large Helical Device (LHD) - the largest stellarator ever built:
Major radius --- 3.5 m
Minor radius --- 0.6 m
On-axis field -- 3 T

Experimentaly proved that JET at different modes provides lifetime of plasma from 5 to 30 sec.
Now if Stellarators are more stable please find the same parameter for LHD.
I am sure that nobody will find. Instead we can read the common reasonings that stellarators provide minimum-B principle and therefore should be more stable.
If "should", so please prove experimentaly. But they cannot.
That is the naked fact.

Now the question: is ARIES-CS the actual machine?
The plasma current (bootstrap current) is 4 MA, which raises
the rotational transform to ~0.7 near the plasma edge.
The second question: is bootstrap current diven internally and what is differnce?
As below quote gives the difference:
chrismb wrote:The absence of a large externally driven plasma current leads
to many attractive features: Stellarators are inherently
steady state, stable against external kink and axisymmetric modes,
and resilient to plasma disruptions.
You would ask: what difference?
Ok.
Very new for me to get to know that bootstrap current is driven internally.
As in fact bootstrap current is driven by beam of neutrals (the most common case) or by RF heaters.
Ok let's call Neutral Beam Injector or RF Heater as "internal devices" :)
The next question is: are those two devices less revolting factor for plasma than externally applied electric field with loop voltage only 0.5-2 V? (these are real numbers)
One more question is: will not ARIES-CS be converted in TOKAMAK and so stopping being Stellarators if current there will reach 4 MA? What field such current will produce at the edge of plasma?
So, is ARIES-CS a Stellarator? Despite its external coil.

ladajo
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Re: Actual Polywell News!

Post by ladajo »

chrismb wrote:
ladajo wrote:Show me your numbers that you can not attract enough fuel ions to have a fusion event with a 15KV electron well using what we publically know about (e-) density in the polywell. You say Brillion limit, I say show me.
Consider Brillouin Limit:
Electron density/m^3, Ne = (e0)B^2 / 2(me) = 8.85E-12 x B^2 / 2(9.1E-31) = ~5E18 x B^2
Say, B=10 T
Ne = ~5E22

Consider an equivalent mass of deuterium being electrostatically confined by those electrons, Nd = Ne/3600 = 1.4E19

Consider the MFP for a 15 keV deuteron of ~s=5 millibarn (5E-31 m^2) fusion-cross section, in collision with Nd = 1.4E19/m^3:
MFP to a fusion event = 1/(s.Nd) = ~1.5E11 m

Consider the speed of a 15 keV deuteron = v = ~1.2E6 m/s [This is a very generous assumption - it is presuming the deuteron keeps up at fusible potential all the time, whereas in reality it is probably only fast enough to fuse for 10% of its reciprocating motion.]

Therefore, average time, t, for each deuteron to fuse = MFP/v = 1.5E11/1.2E6 m/s = ~120,000 s

Fusion power, Pf', for an average of a deuteron pair = ~5 MeV / 120000 = ~6E-18 W

Fusion power, Pf, per cubic meter of deuterons AT 15 keV (viz. the number of deuterons in a 'core' of a reaction space) = Pf = Pf' x Nd = 6E-18 W x (1.4E19/2) = ~47 W / m^3
(note – divide density by two as it takes two particles to fuse, so if all were counted, it'd be double-counting the probability of a fusion.)

So the question remaining is whether the electrical power required to maintain a 10T field across a space big enough to include within it a 1 m^3 sized reaction core, plus the power the electron injection system would need to maintain the electron population at that full Brillouin density enough to maintain a 15keV well depth, is likely to be less than the 47 W (thermal) output of this reactor?
Chris,
Check these out:

http://pop.aip.org/resource/1/phpaen/v4 ... orized=yes

http://prl.aps.org/abstract/PRL/v70/i6/p798_1

Also:

I agree net usefulness at 15KeV is not possible. I also say this is a non-maxwellian machine. My point was that fusion occurs, and it is not limited by conventional magnetic confinement theory. Your calculation process is based on maxwellian devices operating as ignited plasmas. Personally, I do not see net power possible at 15KEV using standar theory. For Polywell this is a an RDT&E regime. Testing to our knowledge to date has been in the 10-12KeV range. Running the device at 50KeV is another matter (and is a net power goal and requirement). The D cross section goes up like 2 magnitudes (but other factors tend to limit it. Speaking of which I make 15KeV more like 1E-4, and 50KeV at 1E-2. (http://www.kayelaby.npl.co.uk/atomic_an ... 4_7_4.html) The resuting increase in output, using standard magnetic confinement ignited plasma theory calculation is about double.

For your D density, I accept your estimate for this discussion, but would offer that it (3600) is a handwave due to our simplified understanding of the dynamics at hand in the operating device. I refer you to the above papers and the potential ramifications to D densities.

For power produced, I also note that you make no consideration for secondary and follow-on chains adding to the mix. 50% of the D-D will make T, and some of that T will react as D-T IMO.

So, in closing, operating the machine in an RDT&E non-net power regime like 15KeV is not going to produce useful output to input given classic modeling and assumptions that the equations remain valid for Density, both (e-) and D. But again, that is using classic assumption. Some would argue that the machine provides the ability to exceed the limit, as it operates in a method not applicable to the theory behind the limit. Running it higher on the cross section curve looks like it will help, but still not enough for D-D. Seeking Net Power, one would have to go for a lower cross section and higher energy/reaction fuel like D-T or P-B11.

Edited for content.
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)

chrismb
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Re: Actual Polywell News!

Post by chrismb »

ladajo wrote:Some would argue that the machine provides the ability to exceed the limit, as it operates in a method not applicable to the theory behind the limit. Running it higher on the cross section curve looks like it will help, but still not enough for D-D. Seeking Net Power, one would have to go for a lower cross section and higher energy/reaction fuel like D-T or P-B11.
Known physics/numbers/cross-sections, etc., have to be followed in the first instance, else the results could wave around one way or the other in the eye-of-the beholder.

Going up the reaction cross-section curve would go to a maximum of 0.2 barns for p11B, which is an adjustment of x40 on the calculation shown above. = 2000 W.

In regards time-to-fusion, where p11B is peak in the CoM, the proton has a speed of around 10Mm/s, x3 on the calculation above. = 6000 W.

The reaction p11B produces 8.68 MeV, ~ x 2 on DD. So that adjusts the above calculation by a further x2.

The net mass adjustment, sticking to the assumption of total confined mass = total mass of electrons, goes from DD's 4 units mass to p11B's 12 units of mass. Adjustment = divide by 3.

Total adjustments = 4000 W. Still not much power output for all the effort of a 10T field across a device of metres across, and maintaining a 650keV electron potential well by pumping with electrons from an electron gun?

ladajo
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Re: Actual Polywell News!

Post by ladajo »

So three things remain outstanding:

Maxwellian or not?

Fuel Density and Distribution (Dependant on (e-) densities and distributions)?

Brillouin Limit Applicability for a non-ignited non-maxwellian non-magnetically confined plasma?

No comment on the papers?
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)

chrismb
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Re: Actual Polywell News!

Post by chrismb »

Maxwellian or not?
The electrons would definitely be Maxwellian, or strongly thermalising at least. But that is immaterial as they would be relatively cold.

The fuel ions should be definitely non Maxwellian. The back-of-envelope estimate above presumes the best of all possible outcomes - that the fuel ions are at their full KE for fusion ALL of the time. A very generous assumption towards a 'good' power figure. (Reality would more likely be an oom lower.)
Fuel Density and Distribution (Dependant on (e-) densities and distributions)?
Again, the calculation above is as generous as it could possibly be - it assumes the full Brillouin density everywhere that the fuel ions pass through at their full KE. It can't be a 'better' assumption towards encouraging the biggest power output figure. (More likely an oom or two lower.)
Brillouin Limit Applicability for a non-ignited non-maxwellian non-magnetically confined plasma?
No comment on the papers?
All guess-work as to how the fields would work. Take a x35 limit if desired, does it really make the figures look better - 120kW? How much power does it take to maintain a 10T field over several metres?

But it could equally be worse than Brillouin. Check out the following:

http://sites.apam.columbia.edu/CNT/publ ... ylimit.pdf

So on the balance of not knowing, the power output assuming;
- the most optimistic possible interpretation of ion speeds (always at full well-depth, fusible KE), and
- the most optimistic possible density (maximum Brillouin limit everywhere), and
- the most optimistic over-Brillouin measurement seen (in a completely different magnetic configuration, but 'whatever'), then

you still end up with only 120kW (thermal) whilst needing to run a 10T field across metres of space.

....The vacuum pumps alone would probably consume that much power, let alone the 10T magnetic coils and 650keV electron injectors....

93143
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Re: Actual Polywell News!

Post by 93143 »

The Brillouin limit doesn't apply to the total electron density; only to the net electron density (and even that's dubious). Ion and electron counts in a fully-formed wiffleball are supposed to be roughly equal; the potential well is created by a slight excess of electrons.

The electrons are fast where the ions are slow, and vice versa, which is one reason why the plasma doesn't neutralize.

Electron confinement is accomplished with the magnetic field. It doesn't have to completely prevent electrons from coming out the cusps, because the magrid's external electric field recycles them when they do. It just has to keep the interior/exterior density ratio high.

Ions are confined by the net negative electric charge of the wiffleball plasma. They are low-energy at the edge and thus put relatively little pressure on the magnetic field, and do not escape the cusps very fast (I don't accept Art Carlson's ambipolarity argument; it seems invalid for the same reason Debye theory doesn't apply in a Polywell - the nature of the energy distribution and its relationship to the plasma potential don't match the theory's underlying assumptions).

Has it really been so long that you've all forgotten how this is supposed to work? Or is there more data that I've missed somehow?

Potential well formation in Polywells is shown experimentally to occur, and to reach at least 80% of the drive voltage even in relatively primitive machines. Wiffleball formation was apparent from numerous tests, including both PXL-1 and WB-6, and is implied by Nebel's comments on the subject combined with the continued Navy funding.

ladajo
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Re: Actual Polywell News!

Post by ladajo »

Chris,
If you also adjust the fuel density more in relation to charge vice mass, that will also improve the output. But here is where some hand waving occurs, because we do not have good models in public venue regarding Ne relationship to Nd. You assume 1/3600, where as many believe that Nd will be close to Ne due to a.) availability, and b.) equal charge. Another point to consider regarding power needed is that in a full scale machine, introducing the fuel as H2 gas provides a handy source of (e-) to provided makeup as the H2 is stripped upon injection, and becomes D. Again, a tad more hand waving as this has yet to be seen in practice, since no full scale machine exists that we know of.
So, as I said earlier the 1/3600 may well be well off.

In any event, your argument for fusion density is tied directly to (e-) charge (and density) as that is what attracts the little buggers. As for velocity, D certainly runs the range, but in the core the idea is that the primary reaction mechanism will come from sufficiently low angle collisions between front aspect Ds. What the angle is, and what average speed is are a function of analyzed perspective. Taking the Hot Core verses the entire transited volume certainly changes the numbers. This also leads one to consider that cross section calculations are conceptually for a uniform group of particles moving through a "pipe" at speed, and percentage collision with stationary victims. It is not a beam cross section at a focused target point like the Polywell would provide. Think along the lines of parking a single bullet in a pipe, and then randomly shooting another through it. The stationary target bullet and fired bullet both have magical protective fields that require a sufficient velocity to overcome. Eventually you will hit it and it will stick. But the fired bullet must arrive with enough speed as well as hit. Now consider putting two guns at either end of the pipe. You aim them both at the same point and start firing. The speed issue is automatically cut in half, and the odds of collision also rise as you are aiming at the same point from either end. You will hit and stick sooner and more often. The wiffleball adds the effect that you are not just a beam to beam, but a volumetric attack against an effective single point in space. All those bullets coming from all those directions towards the same theoretical center, while at steady state, can be averaged to a particles/unit time in the zone. This physical construct is completely divergent from the conceptual concept that cross section was conceived for. It is not a maxwellian volume at uniform pressure where particles randomly and uniformly bounce around until they stick. It is a non-maxwellian volume where all the particles inherently attack each other in the geometric center and attempt collisions at all angles, and corrosponding variant speeds die to angles of approach. Given the geometric convergence, not anticipated in conventional cross section models, there is a higher incidence of probability for collisions. Which means the Barn is really big, and easier to hit.

In short, you are more than likely thin on your (e-) to D density relationship. And the cross sectional data (probability of collision) is probably not valid, and falls short to some degree given the Polywell converges its highest speed particles in the geometric center, vice the random uniform distribution of particles in a volume bouncing around until they hit. This means that the MFP for a Polywell is more than likely different from traditional constructs. After all, we only care that the D slows, and then turns around and comes back again for another try in the volumetric center if it misses another D transiting the center, don't we?

I like some of the work done here by Dan Chicea in this paper. I think the methodology has some application to Polywell.

www.lenr-canr.org/acrobat/ChiceaDelectroncl.pdf
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)

KitemanSA
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Re: Actual Polywell News!

Post by KitemanSA »

Assuming that Nd = number of deuterons and Ne = number of electrons, then in operation, Nd~Ne. The system is quasi-neutral. It was once stated that Ne<1.000001*Nd, IIRC (a difference of less than 1PPM I think were the words).

Joseph Chikva
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Re: Actual Polywell News!

Post by Joseph Chikva »

93143 wrote:The Brillouin limit doesn't apply to the total electron density; only to the net electron density (and even that's dubious).
Correct.
93143 wrote:The electrons are fast where the ions are slow, and vice versa, which is one reason why the plasma doesn't neutralize.
Dubious too.

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