Design of next device (WB-8)

Discuss the technical details of an "open source" community-driven design of a polywell reactor.

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TallDave
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Design of next device (WB-8)

Postby TallDave » Wed Dec 17, 2008 4:00 pm

http://cosmiclog.msnbc.msn.com/archive/ ... 18741.aspx

Despite the skepticism, Nebel and his colleagues have already drawn up a plan for the next step: an 18-month program to build and test a larger fusor prototype. "We're shopping that around inside the DOD [Department of Defense], and we'll see what happens," he said.


So, what do we think this will look like? Obviously the big question is "how much larger?" I think we can safely assume from the timeline that they are not talking about a 1.5M radius net-power device.

My guess is something with water-cooled copper magnets, and only a bit larger than WB-7, so they can get some idea of loss scaling and begin to explore continuous operation in an open reirculating machine (something Bussard was never able to do).

I also move that we begin calling this proposed next machine "WB-8."

Aero
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Postby Aero » Wed Dec 17, 2008 4:22 pm

I wonder ... Dr. Nebel is usually very careful with language.
    18 month program Build and Test
    Larger
    Prototype

An 18 month program to build and test seems to preclude any expectation of net power
A larger fusor will allow confirmation of scaling laws. Is that sufficient justification for an 18 month program?
Prototype, not an experimental device or a test bed, but a prototype. Small scale sub net power prototype, but half scale prototypes are often built. They won't fly (thinking aircraft) but they do give a lot of information.

As for naming it WB-8, no, not a good idea as we have already defined WB-8 to be a dodec configuration. Maybe WB-*

The size of the prototype is the important thing in my mind. Will it fit in the current vacuum chamber or will it demand a larger one?

Where will the work be done? Prototypes are usually done at the manufacturing facility.
Aero

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Postby TallDave » Sun Dec 21, 2008 12:01 am

As for naming it WB-8, no, not a good idea as we have already defined WB-8 to be a dodec configuration. Maybe WB


Well, as I recall we had things we called WB-7 that weren't what is now WB-7. I would move that only actual machines get the next numerical designation. I guess it's really up to Rick's team though. Who knows, maybe they are thinking dodec.

Hmm, "prototype" makes me wonder if it's a full-size device that operates in pulsed mode. That would get all the scaling issues out of the way, and just leave continuous operation.

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Postby MSimon » Sun Dec 21, 2008 12:16 am

Did you notice Rick's Saturday post at Cosmic Log?
Engineering is the art of making what you want from what you can get at a profit.

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Postby TallDave » Sun Dec 21, 2008 9:50 pm

I did not. Thank you for mentioning it.

Good to hear we have neutron counts in the expected range. "Proceeding" sounds promising as well.

Roger
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Postby Roger » Mon Dec 22, 2008 7:43 pm

Aero, you've got me really confused here.....

Aero wrote:An 18 month program to build and test seems to preclude any expectation of net power


Preclude what, why? A 1.6 meter polywell designed to run in pulse mode, just like WB-7, just might take 18 months to build and test.

Aero wrote:A larger fusor will allow confirmation of scaling laws. Is that sufficient justification for an 18 month program?


YES. Scaling is simply one of the most important issues facing Polywell. OF COURSE its sufficient justification for an 18 month program.

There are 2 major issues haunting polywell, scaling and continuous runs.
Scaling breaks down into 2 sub issues. 1) If we double the size of WB-7 will we get 128x the output? Or do we prove scaling by going for net power ? 2) Polywells have been run at the 25millisecond level, Bussard said that was steady state, never the less, building a carburetor and getting runs on the order of 100's of seconds is a big step.

I see 2 easy ways of proving scaling, 1) Build a polywell twice the size of WB-7, or, 2)Build a net power device. I vote for number 2.

Aero wrote:Prototype, not an experimental device or a test bed, but a prototype. Small scale sub net power prototype, but half scale prototypes are often built. They won't fly (thinking aircraft) but they do give a lot of information


Whoa.... Many 1/3 scale prototypes of Northrop's WW2 Flying wing Bomber were built, and flown. IIRC one is preserved at the Smithsonian. I dont think its fair to compare 1/2 scale prototype airplanes to 1/2 scale polywell's. The problem with an airplane is not, we need to make it bigger to prove scaling, just to see if it will fly. A 1/100 scale model of a plane will fly.... but a 1/100th scale polywell will not reach break even..

Aero wrote:.

As for naming it WB-8, no, not a good idea as we have already defined WB-8 to be a dodec configuration. Maybe WB-*


I feel that is a very presumptuous thing to say. We have ...... zero input in a decision of that sort.

Aero wrote:
The size of the prototype is the important thing in my mind. Will it fit in the current vacuum chamber or will it demand a larger one?


If all goes well, Nebel and crew will be buying plenty of vacuum chambers. SO I just don't care about that question.

Aero wrote:Where will the work be done? Prototypes are usually done at the manufacturing facility.


Sit back and chill out. We are yrs from that stage.

Aero, the issues are fairly clear. In no particular order
-dodec
-scaling/net power
-carburetor/continuous running
-direct conversion of alphas.
-PB-11 fuel

Dr Nebel has already started to deal with carburetor/continuous running. As well as hinting at scaling.

Lets play a game. Lets pretend DR Nebel built WB100. He just announced to the world net power results during repeated 200 milli second runs. What do we do next?

Possibly go back and build a dodec the size of WB-7, or go for WB-7 sized LN2 cooling and 10 minute run times, and trying the PB-11 fuel. Regardless, net power becomes the game changer, just as PB-11 is also a game changer.

Bussards passing, or good results from WB-7, does nothing to change the logic of what steps to take next. They have remained the same from my point of view, since I found out about Polywell fusion.
I like the p-B11 resonance peak at 50 KV acceleration. In2 years we'll know.

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Postby Aero » Mon Dec 22, 2008 9:35 pm

Roger wrote:
Aero, the issues are fairly clear. In no particular order

-dodec
-scaling/net power
-carburetor/continuous running
-direct conversion of alphas.
-PB-11 fuel

Question - Isn't PB-11 fuel a requirement for direct conversions of alphas?

I have pointed out elsewhere that the keep alive funding includes the delivery of an ion injection gun. I would be very surprised if it is not sized to work with the larger device Dr. Nebel is shopping around now. To me, that implies longer runs, and ideally, continuous run capability. Of course, continuous running is a much more difficult issue than 5 to 10 second runs with regard to cooling.

I know there are expected benefits, but do we foresee any fundamental problems introduced by changing the geometry to that of a dodec?

Is it practical to consider archiving useful data with a 1.5 meter radius machine with lower power magnets? That is, copper magnets first, sub net power, then superconducting magnets going for net power when they are justified and finished.

I know that a problem with copper magnets and high power testing is the cooling time needed between runs. Couldn't a cooling water line be built into the magnets, not used during the test, but used to speed up the cooling (shorten the time required) between runs?
Dr Nebel has already started to deal with carburetor/continuous running. As well as hinting at scaling.

Lets play a game. Lets pretend DR Nebel built WB100. He just announced to the world net power results during repeated 200 milli second runs. What do we do next?
Well, I don't think the physics community would accept "Net Power" at face value under the circumstance of an uncontrolled run of only 200 milliseconds duration, but using an ion injection gun, controlled runs of several seconds should be possible, shouldn't they? A 2 second controlled run is orders of magnitude more convincing than a 200 millisecond uncontrolled run, IMO.
Possibly go back and build a dodec the size of WB-7, or go for WB-7 sized LN2 cooling and 10 minute run times, and trying the PB-11 fuel. Regardless, net power becomes the game changer, just as PB-11 is also a game changer.

You are right that net power is a game changer. Once it is accepted that net power has been achieved, money will flow, a good number of excellent physicists and engineers will be brought on board and many experiments will be done in parallel. I have personally experienced this phenomenon. Once the perceived risk is reduced or eliminated, enough money becomes available to properly work the remaining problems and evaluate the promising options. Unfortunately, at that point, every company and laboratory in the nation with any capability will start clamoring for a competitive bid, and the navy will be hard pressed to deny it, unless it is a black program.
Aero

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Postby MSimon » Mon Dec 22, 2008 11:01 pm

I have pointed out elsewhere that the keep alive funding includes the delivery of an ion injection gun.


I thought it was an electron injection gun. Nope. Ion Gun:

http://www.fbodaily.com/archive/2008/10 ... 696540.htm

and

http://www.talk-polywell.org/bb/viewtop ... sc&start=0
Engineering is the art of making what you want from what you can get at a profit.

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Postby Roger » Tue Dec 23, 2008 12:23 am

Then you will be very surprised.

Aero wrote: I would be very surprised if it is not sized to work with the larger device Dr. Nebel is shopping around now. To me, that implies longer runs, and ideally, continuous run capability.


Yup Nebel is done with WB-7... in fact Nebel has started collecting parts for WB-8, starting with an ion gun. Hat tip to Aero.

When you are trying to invent a carburetor... I suggest waiting until you have built the engine.
I like the p-B11 resonance peak at 50 KV acceleration. In2 years we'll know.

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Postby TallDave » Tue Dec 23, 2008 5:09 am

Preclude what, why? A 1.6 meter polywell designed to run in pulse mode, just like WB-7, just might take 18 months to build and test.


That'd be nice, but I don't know if that's actually possible. A net power strength magnet (~5T) will probably need to be superconducting (someone more knowledgable correct me if I'm wrong) which means cooling and etc., similar headaches to continuously operating machine.

Also, a pulsed machine implies they are sweeping through beta rather than holding it, so it can't really be "net power" for more than a millisecond or so. There would no doubt be considerable scoffing at the idea such a machine was producing "net power."

Still, they could learn a lot about loss scaling from a 1T uncooled copper device at some size quite a bit larger than WB-7, and probably fairly cheaply in the grand scheme of things. I think 1T about the limit they could get from uncooled copper at reasonable expense/effort (although, see above parenthetical).

Of coourse, any bigger badder Polywell will be fun to study.

I know there are expected benefits, but do we foresee any fundamental problems introduced by changing the geometry to that of a dodec?


It's a bit harder from an engineering standpoint -- more twists and turns and etc. I'd be surprised if they were fooling with higher-order polygons at this point given the benefits don't even amount to an order of magnitude (and there are many, many orders of magnitude between Wb-7 and net power), but I've been wrong before.

s it practical to consider archiving useful data with a 1.5 meter radius machine with lower power magnets?


To some extent. But ultimately it's B^4 * r^3 scaling, so in the end they'll need the big guns to prove this can work.


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