We Will Know In Two Years

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

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PolyGirl
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Re: WB8 Considerations

Postby PolyGirl » Sat Jun 20, 2009 12:57 am

PolyGirl wrote:The only question is, whether this larger size Polywell is going to be continuous or pulsed?

The answer is from the current solicitation is Pulsed (WB8).

Which leaves the following question of course. Will WB9 be continuous or pulsed?

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Polygirl
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TallDave
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Postby TallDave » Sat Jun 20, 2009 1:32 am

I think we can safely say a reactor will not be pulsed.

As I understand it, the physics are so fast the "pulse" as it sweeps through beta is long enough to tell us what we need to know to get to a reactor (and whether that is possible). Moving from pulsed to continuous should just be engineering.

I always thought a continuous non-reactor machine would be neat, but in retrospect that was a bit too whimsical a wish. From a practical perspective varying the magnet strength probably makes a lot more sense since the loss scaling with B is the biggest issue.

Roger
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Postby Roger » Sun Jun 21, 2009 3:55 pm

TallDave wrote:
As I understand it, the physics are so fast the "pulse" as it sweeps through beta is long enough to tell us what we need to know to get to a reactor (and whether that is possible).


The "pulse" or "sweep" gives us a good idea of whats going on in the 30cm WB-6&7 size. And no doubt, real good reason to keep building WB's.

Scale it up, doesnt the sweep take a lot longer in a larger vessel? Such that the 4 or so milli seconds involved in running WB-7, wont do in a larger machine. The "sweep", on larger WB's will be much longer. And dont we expect a very different plasma in a 3 meter Polywell, than in a 30cm Polywell?
I like the p-B11 resonance peak at 50 KV acceleration. In2 years we'll know.

TallDave
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Postby TallDave » Sun Jun 21, 2009 5:11 pm

Yes, that longer sweep might be what Dr. Nebel was referring to with his "greater dynamic range" comment (I've been trying to puzzle out exactly what that meant).

My understanding is that the basic physics should still be fast enough that a WB-8 pulse will tell us enough about the scaling that we could conceivably build WB-100 with some reasonable expectation it would work as hoped. The magnets are almost an order of magnitude stronger in WB-8 versus WB-7 (.8T versus .1T). The plasma would be 8^4= 4096 times more powerful and produce something resembling 8W (all else being equal to WB-6). How it behaves is the big question I suppose, esp regarding confinement.

(In fact, come to think of it, the proportion of magnet strength between WB-7 and WB-8 might actually be bigger than the difference between WB-8 and WB-100. At similar proportions, we'd be looking at 6.4T magnets in WB-100, and I think the EMC2 guys have been thinking around 5T.)

I did my little BOE calc of 8W for WB-8, but I didn't make any adjustments for size because I don't know the new dimensions. If it's also twice as large, we might be looking at something around 64W.

Bussard did make at least one continuous machine in that 30cm size, iirc.

Torulf2
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Postby Torulf2 » Sun Jun 21, 2009 5:43 pm

I still have some doubt. Most criticism against the pollywel have been excellent refute on this site. But there is one simple exception. The pumps for maintain the vacuum. Here have I not find many good arguments. Only arguments based on authority and guess: “ Bussard must have find some solution”. Or “it’s an engendering problem”. An engineering problem can be a show stopper. Because the problem is so simple and basic it may have been ignored.
Will we know this in two year, or then they actually are building the first power producing reactor.

cuddihy
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Postby cuddihy » Sun Jun 21, 2009 11:34 pm

Torulf2 wrote:I still have some doubt. Most criticism against the pollywel have been excellent refute on this site. But there is one simple exception. The pumps for maintain the vacuum. Here have I not find many good arguments. Only arguments based on authority and guess: “ Bussard must have find some solution”. Or “it’s an engendering problem”. An engineering problem can be a show stopper. Because the problem is so simple and basic it may have been ignored.
Will we know this in two year, or then they actually are building the first power producing reactor.


Torulf2,

There's quite a long thread on problems with maintaining vacuum in an operating polywell, but I can't figure out which specific criticism are you referring to?

Is there one aspect of maintaining vacuum that you think is particularly hard, and what are you basing that inference on?

Tom
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kunkmiester
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Postby kunkmiester » Mon Jun 22, 2009 2:08 am

If a machine is designed for pulse work at a specified power level, how much of that can it manage sustained?
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TallDave
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Postby TallDave » Mon Jun 22, 2009 3:38 am

kunkmiester wrote:If a machine is designed for pulse work at a specified power level, how much of that can it manage sustained?


Not very long. I get the impression they just sweep through beta over the course of a few milliseconds (anyone who knows better feel free to contradict me) and for the fraction of a millisecond that approximates beta=1 they get the data of interest (and maybe some fusions if they're running deuterium rather than helium plasma). IIRC they were running WB-7 a couple shots a day.

As I understand it, the major difference between continuous and pulsed operation is the former involves cooling the magnets, which is considerably more expensive.

MSimon
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Postby MSimon » Mon Jun 22, 2009 9:13 am

TallDave wrote:
kunkmiester wrote:If a machine is designed for pulse work at a specified power level, how much of that can it manage sustained?


Not very long. I get the impression they just sweep through beta over the course of a few milliseconds (anyone who knows better feel free to contradict me) and for the fraction of a millisecond that approximates beta=1 they get the data of interest (and maybe some fusions if they're running deuterium rather than helium plasma). IIRC they were running WB-7 a couple shots a day.

As I understand it, the major difference between continuous and pulsed operation is the former involves cooling the magnets, which is considerably more expensive.


I'm fairly confident that a 3T 1 m coil dia WB-7 style machine can be built for $10 million including pwr supplies, shield bldg, instruments, etc. Operation in the 1 second to 10 second range.
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