Small update from Lawrenceville Plasma Physics

[Giorgio]

Yet another interesting update from Focus Fusion:
http://focusfusion.org/assets/lppx/LPPX_2011_11_23.pdf

On November 2, FF-1 fired five shots in a row, under the same conditions, with fusion yield varying by only plus or minus 2.6% from an average of 0.9x10^11 neutrons.

The greater repeatability, we believe, is due to our tighter control of asymmetries in the device, including the centering of the electrodes (see more below). But the axial field coil (AFC), a magnetic coil which imposes a small field along the axis, probably contributes as well. The coil’s field of only 2 gauss, just 6 times the earth’s magnetic field in the vertical direction, imparts spin to the plasma which is greatly amplified while the current sheath moves down the electrodes. As with a spinning bullet, the spin can stabilize the sheath, making the output more repeatable.

[rcain]

well caught Georgio.

how exciting!

i see also, they have their first international patent in place (Australia of all places - wonder what the strategy there is?).

these guys are so well organised (compared for example to Rossi's mad rush). and great technical detail in the bulletins - got me hooked.

good to see the 'shot-rate' going up also - that's got to be in the right direction, experimentally and design-wise.

wonder what the x-ray efficiency is looking like - that was key to his planned first applications project - and that in turn, key to him 'gearing up' for a run at a (direct) electrical generation product.

ps. sounds like 'maintenance' and physical robustness/tolerance are going to be issues in any final design though. wondering if there isn't any solid 'monolithic' alternative to those 'pins'.

[Giorgio]

ps. sounds like 'maintenance' and physical robustness/tolerance are going to be issues in any final design though. wondering if there isn't any solid 'monolithic' alternative to those 'pins'.

This was actually one of the biggest worries for FF if I remember correctly.
But I guess that once the physics is in place Engineering will take over and should not be so tough to come out with a feasible solutions. We have made giant leaps in material technology in the last 20 years.

[Skipjack]

Thinking about how gasoline engines have evolved from their humble beginnings, I am sure that once the science is solid, engineering will be able to solve the rest.

[Brian H]

...
While a Polywell might be scaled to GW sizes, from a piratical standpoint outputs of a few hundred MW will possibly be more attractive.
...
I suspect the wild card here may be photovoltaics. I constantly see claims of improvement in efficiencies. If they ever get to efficiencies of 50-60% with cheap solar panels, things will be more competitive. Of course energy storage would still be an added cost problem.
...

Dan Tibbets

Arrr! Is it talk like a pirate day yet?


Photovoltaics, even if 100% efficient, still require very large areas (= real estate), are dependent on hours and angles of sunshine (i.e., are variable due to factors which are not "dispatchable"), and require huge transmission investments (also including large real estate commitments).

All advances of society and economics depend on energy sources becoming:
1) Cheaper
2) More compact
3) More dispatchable (controllable)

than pre-existing sources.

PV is out of the running compared to conventional, NG generation, and fusion, especially FF, on all the above. So, in fact, are all "renewables".

[rcain]

ps. sounds like 'maintenance' and physical robustness/tolerance are going to be issues in any final design though. wondering if there isn't any solid 'monolithic' alternative to those 'pins'.

This was actually one of the biggest worries for FF if I remember correctly.
But I guess that once the physics is in place Engineering will take over and should not be so tough to come out with a feasible solutions. We have made giant leaps in material technology in the last 20 years.

re: (original) 'worries' - certainly the erosion factor, yes; and the precision/tolerance could be inferred from the ('sensitivity' of) theory and design as well as the lab reports.

but i get the feeling that for FoFu at present, the science and the engineering can no longer be separated so easily - ie. the science here can only proceed/advance if the design engineering in the lab is pretty much up to a 'production standard'.

re: 'monolithic' (anode) - i was thinking maybe the pins could be moulded or pressed into a ceramic insulator block (ring), having the effect of mechanically stabilising and locating the pins very precisely.

thinking that through further, does anyone know why they are using multiple anodes - apart that is from the need to get power levels up using off the shelf equipment?

would it not be possible to use a single, solid outer anode 'ring', rather than pins, and provide the 'shortest path' dimension by using gaps in the inner insulator. (ie. imagine a single outer electrode ring with 'cog teeth' pointing inwards, though 'gaps' in an inner insulating ring).

would have the additional advantage that it could generate many more 'filaments' than the existing design, whilst also being mechanically very robust and very precise. also, 'timing' between pins firing, not an issue any more (simply a matter of providing a single nice edge on a single supply).

i'm wondering also, whether increasing the number of anodes/filaments in this way would also reduce the erosion rate?

i'm presuming in the above, that somehow or other the existing 'drive' circuitry could be ganged-up to drive a single anode.

are there any reasons why it couldn't be done this way?

what do you think?

[Giorgio]

but i get the feeling that for FoFu at present, the science and the engineering can no longer be separated so easily - ie. the science here can only proceed/advance if the design engineering in the lab is pretty much up to a 'production standard'.

That will be the best solution of course, but I do not think that their finances allows them to do so at the moment. Considering on what little budget they are actually working they did miracles so far.

thinking that through further, does anyone know why they are using multiple anodes - apart that is from the need to get power levels up using off the shelf equipment?

would it not be possible to use a single, solid outer anode 'ring', rather than pins, and provide the 'shortest path' dimension by using gaps in the inner insulator. (ie. imagine a single outer electrode ring with 'cog teeth' pointing inwards, though 'gaps' in an inner insulating ring).

There was a discussion about this on FF forums one year ago if memory serves me right.
I have no time now but tomorrow I will try to find it back and post a link to it for you.

i'm wondering also, whether increasing the number of anodes/filaments in this way would also reduce the erosion rate?

It should. More filament = less energy per filament hence less erosion.

[Brian H]

Precision of positioning seems to be key. A ring was tried, but irregularities expanded exponentially. Careful height- and tilt-of-pin matching is the current mode.

[rcain]

Precision of positioning seems to be key. A ring was tried, but irregularities expanded exponentially. Careful height- and tilt-of-pin matching is the current mode.

Hi Brian, that is interesting, thanks, i didn't know that. (though it makes sense it would have occurred to Eric at the start i would imagine).

do you know if they tried an 'interior cog' form, or did they just try a 'round outer'? - in which case i can imagine why it wouldn't work.

[tomclarke]

Precision of positioning seems to be key. A ring was tried, but irregularities expanded exponentially. Careful height- and tilt-of-pin matching is the current mode.

The encouraging thing is that precise symmetry, while difficult to engineer, is not in principle impossible, even with erosion. You can imagine a sophisticated feedback system which uses data fom each shot to adjust the next.

If they got useful Q from this, with perfect symmetry, there is the motivation to try hard to make a workable repetitive system.

[rcain]

Precision of positioning seems to be key. A ring was tried, but irregularities expanded exponentially. Careful height- and tilt-of-pin matching is the current mode.

The encouraging thing is that precise symmetry, while difficult to engineer, is not in principle impossible, even with erosion. You can imagine a sophisticated feedback system which uses data fom each shot to adjust the next.

If they got useful Q from this, with perfect symmetry, there is the motivation to try hard to make a workable repetitive system.

good point also. though that is going to be a lot harder if things are 'literally' wobbling around all the time at each shot. something more rigid... i am thinking.. precision machined from solid ... and then the feedback...

[CharlesKramer]

I should also add that if the BLP reactor were to work out, it would be useful in instances where the FFR is even too large, like automobiles, robotic interplanetary probes, small general aviation aircraft

Yes!

Around 2003 Casio showed a mock up of a reformer style fuel cell -- it reformed a simple hydrocarbon (alcohol probably) into hydrogen on a semi-conductor chip scale. The reaction created high (100s of degrees) but very localized heat.

I realize plasma technology is wholly unrelated, but billion-degree plasmoids (the temp needed for p-b11) are very tiny, allowing one to imagine (at least) that a long term challenge for dense plasma focus devices is not how large they can scale up, but how small they can scale DOWN.

Close down projects like NIF that cannot ever lead to cost effective power generation, and we'd have plenty of money to fund all three and more at accelerated rates.

Of course, the funding for NiF is only partly based on fusion.

Given each of these three show even an off-hand chance of ever working, it seems pretty insane to me that the US is not investing extremely heavily in them.

Amen (although I don't understand your acronyms --FFR, BPL. I assume you refer to Polywell, dense plasma focus and reverse field configuration).

CBK