Lawaranceville E-Newsletter

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

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Ivy Matt
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Post by Ivy Matt »

That just means Talk-Polywell is relatively more popular.

Back on topic, Brian Wang at Next Big Future also picks up on the success (?) of the new switches and explains the significance better than I have.
Temperature, density, confinement time: pick any two.

Skipjack
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Post by Skipjack »

I think that this is BS. There are plenty of papers on FRC and Slough is not the only one doing research with it. Basically an FRC is a stretched out Tok. There is lots of research on that.

MSimon
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Post by MSimon »

Skipjack wrote:I think that this is BS. There are plenty of papers on FRC and Slough is not the only one doing research with it. Basically an FRC is a stretched out Tok. There is lots of research on that.
Don't forget the "mirrors" on the ends.
Engineering is the art of making what you want from what you can get at a profit.

Skipjack
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Post by Skipjack »

Don't forget the "mirrors" on the ends.
http://www.google.at/#q=field+reversed+ ... 7c11ae09c2


Btw:
http://www.google.at/#hl=de&source=hp&b ... 7c11ae09c2

With this search TP does not come up until page 4.

Skipjack
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Post by Skipjack »

To get back to the original topic of the thread. There have been 3 updates on the LPP website today:
http://www.lawrencevilleplasmaphysics.c ... &Itemid=90

http://www.lawrencevilleplasmaphysics.c ... &Itemid=90

http://www.lawrencevilleplasmaphysics.c ... &Itemid=90

Still having some problems with their switches. Other parts of the project are improving nicely though.

chrismb
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Post by chrismb »

The graph is still up there [from last year]. Wonder when it might get 'changed' for an updated plot, 'cos I don't think they did end up hitting 30kJ neutron yield per shot by the end of the year, did they?!...?

Image

Maybe without a 'year' date on it, they can use it every year? Kinda like taking a lead out of tokamak's history? :lol:

MSimon
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Post by MSimon »

chrismb wrote:The graph is still up there [from last year]. Wonder when it might get 'changed' for an updated plot, 'cos I don't think they did end up hitting 30kJ neutron yield per shot by the end of the year, did they?!...?

Image

Maybe without a 'year' date on it, they can use it every year? Kinda like taking a lead out of tokamak's history? :lol:
What is amusing is that their research shows a flattening of the curve (red line) and yet they posit an acceleration of results with a linear extrapolation to great results - very soon.

What it looks like to me is that larger devices have other loss mechanisms. i.e. the results curve flattens.

And by larger I mean size or input power. Now if it is just input power maybe a larger size will lower the losses. Fine. But from where they are on the curve by any reasonable scaling laws it is going to have to be a LOT larger. i.e linear or r^3 doesn't make a lot of difference given the starting point.

And given the device is area based rather than volumetric r^2 is most likely i.e. double power = 1.4X linear dimensions. Even r^3 = 1.25 not too bad - except when you need to go up 8 or 9 orders of magnitude. 10 doublings = 3 orders of magnitude. 30 doublings = 9 orders.

30 X 1.4 = 42 times larger. if they start at 3" they wind up at 126" - 10 ft. And that is just the throat.

30 X 1.25 = 37.5 - 112" at the throat.

Any one have a number for current throat dimensions?
Engineering is the art of making what you want from what you can get at a profit.

Wittgenstein
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Post by Wittgenstein »

MSimon wrote:
chrismb wrote:The graph is still up there [from last year]. Wonder when it might get 'changed' for an updated plot, 'cos I don't think they did end up hitting 30kJ neutron yield per shot by the end of the year, did they?!...?

Image

Maybe without a 'year' date on it, they can use it every year? Kinda like taking a lead out of tokamak's history? :lol:
What is amusing is that their research shows a flattening of the curve (red line) and yet they posit an acceleration of results with a linear extrapolation to great results - very soon.

What it looks like to me is that larger devices have other loss mechanisms. i.e. the results curve flattens.
Yes, but this graph shows results as a function of time, not of anything else. Also, I think the future line is meant as a game plan, certainly not an extrapolation of the red actual results.

So it shows that they've not been able to maintain hoped for (log)linear progress as a function of time. If their progress has been hampered by specific issues that are now resolved, it's not unreasonable to think there could be a leap forward in results.

I don't see how a flattening curve as a function of time tells much at all about the science. It only tells you that they are not maintaining the pace they had hoped for -- which, while not encouraging, is hardly a surprise on any project.

ladajo
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Post by ladajo »

I have to agree that it is a bad graph. I almost posted about it when I saw it, then decided to leave it be, as I was sure someone else would pick up on it.

It does "imply" that they will get great results, but does not account for the actual data flattening.

I think they should revamp it to show full goal curve from left to right, and plot progress as achieved. Not delete the lower part of the goal curve. It makes it suspect.

If they want to add a third curve showing "predicted results" based on experiment equipment upgrades, etc, then do so.

MSimon
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Post by MSimon »

It only tells you that they are not maintaining the pace they had hoped for
True that.

But there is still the scaling problem. If the scaling is r^3 can they keep doubling the size of the device ~10X power every month? For 10 months? A doubling in size every 3 months would still be very good. Where is the progress?
Engineering is the art of making what you want from what you can get at a profit.

Skipjack
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Post by Skipjack »

While it is good to be sceptical, Msimon, I believe that you are getting ahead of yourself here. The graph does not show any scaling laws, but as Wittgenstein has mentioned correctly, shows the progress that they have made in this timeframe, versus the progress they are planning to make. Drawing conclusions from a lack of progress (which could be due to all sorts of issues, like the switches) to the validity of scaling laws seems to be a far stretch to me.

MSimon
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Post by MSimon »

Skipjack wrote:While it is good to be sceptical, Msimon, I believe that you are getting ahead of yourself here. The graph does not show any scaling laws, but as Wittgenstein has mentioned correctly, shows the progress that they have made in this timeframe, versus the progress they are planning to make. Drawing conclusions from a lack of progress (which could be due to all sorts of issues, like the switches) to the validity of scaling laws seems to be a far stretch to me.
I'm making some assumptions of course. I assume the B field is maxed out and all they have to get more power is size.

To keep the field the same every linear doubling requires a doubling of current. If they can't keep increasing current with size....
Engineering is the art of making what you want from what you can get at a profit.

Skipjack
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Post by Skipjack »

I'm making some assumptions of course. I assume the B field is maxed out and all they have to get more power is size.
Not having followed everything they are doing in to much detail, I believe that they are still a long shot from having the machine working at design specifications. They still have not completely overcome the problems with the switches yet and they still have issues with the electrodes too, I believe. I dont think that they are planning to scale the machine up at the current point in time, but they still want to go for PB11 later this year.
I dont think they have even achieved simultaneous firing yet.

MSimon
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Post by MSimon »

Yeah. Electrode erosion is going to be a b****. Now imagine the current per unit of circumference has to go up 40X to keep the field constant at max size. Polywell can do that (within limits) because they have volume to work with.

In fact (within limits) Polywell output goes up as the device gets smaller. That is some unusual scaling.

How does Polywell do it? Current per turn and turns are constant. Output goes up linearly with a reduction in size i.e. B^4 vs r^3.
Engineering is the art of making what you want from what you can get at a profit.

Skipjack
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Post by Skipjack »

Yeah. Electrode erosion is going to be a b****.
Now that I can fully agree with and I am sure they are aware of that too.
My guess is that they are simply going to treat the electrodes as expendable parts and hope that somone will come up with a solution for the problem some other day (basically, not "their" problem).

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