Lawaranceville E-Newsletter

[djolds1]

New Report is out! looking good!
http://www.lawrencevilleplasmaphysics.c ... 202013.pdf

How easy would it be to scale up a successful FF to say 8-16 GW(th)? I.e. the Polywell range cited for the QED thrusters in the papers on Askmar. My impression has always been that FF is optimized for the lower end of the spectrum, ~100-300 MW(e) & 100-300 MW(th). The current FF design, assuming success, looks to be easily built to be the size of say a high-bypass turbofan.

[Skipjack]

From what I understand, it does not scale very well. It is best at the small sizes in the low MW range and you would just use multiple devices.

[zapkitty]

From what I understand, it does not scale very well. It is best at the small sizes in the low MW range and you would just use multiple devices.

Yep, as of now it looks that way.

Per LPP: if an FF unit is run at much less than 5MWe (IOW if it is run cooler) then the boron gas fuel might plate out and foul things up.

Conversely, if it's run it too much over 5MWe then the tiny FF core probably couldn't be cooled fast enough.

That's why LPP emphasizes that FF units would have both low per-unit cost and could be easily stacked.

And 20 5MWe FF units at about $6,000,000 US would still be cheaper than one 100MWe Polywell at about $100,000,000.

Of course at GWe+ levels the Polywell comes into its own.

[Skipjack]

From what I understand, it does not scale very well. It is best at the small sizes in the low MW range and you would just use multiple devices.

100MWe Polywell at about $100,000,000.

Where does that number come from? It seems a bit high. The research on a full scale Polywell might cost that much, but I dont think that a reactor will cost that much once we know how to do them.

[djolds1]

From what I understand, it does not scale very well. It is best at the small sizes in the low MW range and you would just use multiple devices.

Yep, as of now it looks that way.

Per LPP: if an FF unit is run at much less than 5MWe (IOW if it is run cooler) then the boron gas fuel might plate out and foul things up.

Conversely, if it's run it too much over 5MWe then the tiny FF core probably couldn't be cooled fast enough.

That's why LPP emphasizes that FF units would have both low per-unit cost and could be easily stacked.

And 20 5MWe FF units at about $6,000,000 US would still be cheaper than one 100MWe Polywell at about $100,000,000.

Of course at GWe+ levels the Polywell comes into its own.

Sure. But stacked FFs look to be too massive and bulky for the QED thruster approach.

[TallDave]

Are they still on track to produce power commercially in 2010?

[happyjack27]

From what I understand, it does not scale very well. It is best at the small sizes in the low MW range and you would just use multiple devices.

Yep, as of now it looks that way.

Per LPP: if an FF unit is run at much less than 5MWe (IOW if it is run cooler) then the boron gas fuel might plate out and foul things up.

Conversely, if it's run it too much over 5MWe then the tiny FF core probably couldn't be cooled fast enough.

That's why LPP emphasizes that FF units would have both low per-unit cost and could be easily stacked.

And 20 5MWe FF units at about $6,000,000 US would still be cheaper than one 100MWe Polywell at about $100,000,000.

Of course at GWe+ levels the Polywell comes into its own.

i wasn't thinking heat was the size-limiting factor. i was thinking hydromagnetodynamics. e.g. bigger means the electrodes would be farther apart, which means you'd have to give it much higher voltage to produce the same shape. and then it might be much more sensitive to inaccuracies, harder to keep stable, etc. the difficulties might scale with higher exponents than the power gain.

though the properties of materials are not going to scale with the rest of the machine - they're melting points don't get higher by adding more. so just put more space in-between them? i'm sure some scaling problems can be solved by some simple engineering. but unless _all_ of them can, you're going to reach a point of diminishing returns. i just think that issues with plasmoid geometry / stability / power, etc. are going to become limiting factors before heat does. but i'm just guessing.

[Ivy Matt]

New report for May, PDF here.

Headlines:

*Plasmoid density triples, fusion energy rises with purer plasma
*But not pure enough—LPP tracks down what disrupted the filaments
*LPP has new paper for Spain conference
*US Department of Commerce finds all in order with LPP-Iran Scientific “Fusion for Peace” Collaboration
*LPP has rendezvous with Chu as Congress sets eye on ITER costs

[Maui]

I'm happy they seem to have a good theory about the density issue, but it also looks in danger of yet another project falling into the results not matching theory refrain.

If nothing else, it sure is nice actually getting news you can follow.

[Ivy Matt]

I don't know, it looks to me more like it's in danger of the engineering not being up to the task of fully testing the theory. That's been the problem so far. It would be nice if they finally got to the point where the engineering was such that they could fully test the theory.

[Ivy Matt]

Are they still on track to produce power commercially in 2010?

We'll know in two years.

[KitemanSA]

From what I understand, it does not scale very well. It is best at the small sizes in the low MW range and you would just use multiple devices.

100MWe Polywell at about $100,000,000.

Where does that number come from? It seems a bit high. The research on a full scale Polywell might cost that much, but I dont think that a reactor will cost that much once we know how to do them.

My recollect (fuzzy) was that Dr. Bussard proposed a 5 year, $200M project that included building and testing two more small scale units to test out SHAPE issues, then build a demo unit (sans power extraction system) at about 100MW.

If the $100M for 100MW were full system price, that would be amazingly low. Current large fission plants are about 10 times that, and fully burdened "green" systems 2 to 5 times that.

[mvanwink5]

200 million? Now that would take some guts. I wonder if the Navy will ever find the 200 million. I also wonder what criteria they will use to say they should build it? After all, the small machines have issues with electron injection that the larger machines are not supposed to have, which is why Bussard said the next step was the large machine. Further, scaling is supposed to have been shown over a year ago (from what we know). And here we are, still testing with the small difficult to make work, WB-8 machine. Bussard also didn't say the geometry testing was necessary, and there are some who wonder given the expected scaling power why it would be important. But that is just the old MSimon-KitemanSA debate.

Focus fusion has similar shoe string issues, always dealing with problems that seem associated with how they are making the device. It puts doubt in their approach that might not be there otherwise. Catch 22.

[KitemanSA]

200 million? Now that would take some guts. I wonder if the Navy will ever find the 200 million. I also wonder what criteria they will use to say they should build it? After all, the small machines have issues with electron injection that the larger machines are not supposed to have, which is why Bussard said the next step was the large machine.

My recollection was that the problem with the small machines was that too many neutrals escaped the MaGrid before they could be ionized which left a lot of them outside the MaGrid leading to early Paschen arcing.

Further, scaling is supposed to have been shown over a year ago (from what we know). And here we are, still testing with the small difficult to make work, WB-8 machine.

The thing to remember about WB8 was that it was NOT a scale-up of WB7. Though the physical size may have been twice as big, the magnets are 8 times as powerful. We don't know what the MaGrid voltage is. Perhaps the mixed scaling made it MORE difficult to stuff electrons through a smaller magnetic hole.

Bussard also didn't say the geometry testing was necessary,

All I see is in the Valencia paper where he defines the basic project, including checking out two different geometries.

and there are some who wonder given the expected scaling power why it would be important. But that is just the old MSimon-KitemanSA debate.

All else being equal, getting 5 times the power should be considered a good thing.

[mvanwink5]

KitemanSA wrote:

My recollection was that the problem with the small machines was that too many neutrals escaped the MaGrid before they could be ionized which left a lot of them outside the MaGrid leading to early Paschen arcing.

Yes, your recollection is spot on, but there is more to it as one tries to work around it.
From Results and Final Conclusions:

In small machines this is difficult, as time scales for neutral transport to the exterior are measured in fractions of a millisecond, and dimensions within the machines are not sufficient to allow rapid ionization at the limited electron currents and densities attainable.

Thus EMC2's WB-8 project's need for higher power (in electron gun terminology, higher heating) electron guns? Remember EMC2 bought higher heating electron guns, independently controlled (as Bussard said would be needed) to reach higher densities, and the long project delays as a result? Surprise, surprise!? and,

Thus, in small systems there is a big incentive to attempt to fuel the machine with ions injected from ion guns placed on cusp axes. This, however, poses the problem that the ion guns must be at machine voltage, thus constitute very visible and attractive potential sinks for electrons, as they can not be fully magnetically shielded, as can the magnets themselves. In this situation, it appears that the only way to test these principles in small machines is to try to use capacitor discharge drives, timed precisely so that neutral gas injection is started with the cap drives, and the electron well drives are also started simultaneously. This requires very precise timing, which is difficult but has been achieved in such tests, however, this entire problem goes away in machine sizes for net power production.

The point is small machines are tough to succeed with, not big machines. And the final point is at what point does the Navy pony up with the money? What could possibly be the criteria that hasn't been met if scaling is known and it is easier to make a large machine work? In fact, for steady state, Bussard argues that small machines smaller than 1 to 1.5M radius won't work due to thermal limits or construction limits. (However, with recent, improved superconductors, maybe that has changed.)

Geometry factors are straight forward inferences from the larger diameter WB that one gets from better spherically conforming magnets. With high B field I have doubts that coil shape optimization will yield significant benefit. Certainly, I have doubts that small, hard to run pulsed machines will believably prove polywell will work for large steady state machines with 100% certainty. Moreover, I would posit the catch 22 here is that no one sees enough with small pulsed machines to be certain the results will translate to large machines. It is the shoe string project dilemma. Too many CMB's standing around ready to say I told you so if an unforeseen snag appears that a small hard to run pulsed machine won't catch.

So, it looks like we will shoestring science project this effort for decades, OCD (obsessive-compulsive disorder) optimizing so as to avoid large risks. Of course, keeping the data secret is necessary to make it less likely someone else will do it and achieve success, and make the risk adverse look like foolish cowards.

In short, government shoestring career making science project, the solution bureaucrat's most prefer.