[MTd2]

jamesr wrote: The 1.6MA figure is a generic limit for a single current carrying filament of plasma (a Z-pinch) regardless of its size or origin.
The particular geometrical & electrical arrangement of a DPF is the topic of Sing Lee’s paper. The Pease-Braginskii current is not a hard limit, in that is cannot be exceeded. It is just that if the current is higher than the critical value for that fill gas, the filament will be unstable and begin to collapse because the pressure is no longer balanced.

I don`t think so if I read Sing Lee`s papers. The saturation effect is a new one found in the end of 2007. Here:

“In the last 3 months of 2007 numerical experiments using the code found a new effect, the plasma focus pinch current limitation effect.”

http://www.plasmafocus.net/IPFS/Papers/IWPCAkeynote2ResultsofInternet-basedWorkshop.doc (Introduction)

According to Sing Lee, it is a general fact, and it is common to all kinds of configuration of DPF devices:

“Note that this is a general result and is independent of the actual processes involved. In the case of the plasma focus axial phase, the motion of the current sheet imparts power to the shock wave structure with consequential shock heating, Joule heating, ionization, radiation etc.”

http://www.plasmafocus.net/IPFS/Papers/09PP8APL.pdf (page 2)

And the only way to counter it is by moving to higher and higher voltages:

“If we operate a range of such high voltage machines at a fixed high voltage, say 300 kV, with ever larger E0 until the surge impedance becomes negligible due to the very large value of C0. then the saturation effect would still be there, but the level of saturation would be proportional to the voltage. In this way we can go far above presently observed levels of neutron saturation; moving the research, as it were into presently beyond-saturation regimes.”

http://www.plasmafocus.net/IPFS/Papers/09PP8APL.pdf (page 3)

It doesn`t seem LPPX is free from that unless it raises the cathode`s voltage. If Lee`s mode is used for LPPX, it will show a saturation effect….

[MTd2]

jamesr wrote: Basically this give a limit on the current a filament can carry where the radiation pressure outwards balances the pinch force inwards. For deuterium the figure is around 1.6MA.

According to Sing Lee, this limit is due the impedance of the contracting plasma not due radiation pressure.

It can be overcome by increasing the voltage between the cathodes to high values, like above 90KV:

http://www.plasmafocus.net/IPFS/2010 Papers/2010 Pp2 IJER.doc

The Las Vegas DPF can do that:

https://focusfusion.org/index.php/site/article/july_switch_update/

Unfortunately, LPPX cannot…

[MTd2]

I read the article. http://www.plasmafocus.net/IPFS/modelpackage/File2Theory.pdf

Take a look at the phase 2, using the slug model, page 6:

“The speed of the inward radial shock front (see Fig 1b)is determined by the magnetic pressure (which depends on the drive current value and CS position rp)”

So, what I meant is based on this:

http://en.wikipedia.org/wiki/Double_layer_(plasma)

I didn’t know the name of the phenomena before, but this is what I was thinking. A polar gas would give a doping of ions to the double layer of the advancing magnetic piston, which would increase the steep of the potential, accelerating the front wave even more. That would cause a faster pinch and higher end temperature.

[MTd2]

I will read it all. I guess a degree in physics cannot go wasted…

[MTd2]

Would mind then explaining what is the nature of a plasma propagating inside the LPPX device?

I think the plasma in this medium should have a shockwave component. As the plasma progresses, it compresses the gas ahead. But if the gas has a polar nature, it will tend align its charges to perpendicular slightly ahead the shock wavet. Such alignment should make the gas ahead of it work a lightining rods elongating the wave front. So, the plasma would ride behind a hot wave front. The resistance should be smaller.

[MTd2]

jamesr wrote: I’m not sure why you think this is an issue, but the polarity or lack of in the fill gas is really completely irrelevant. At the voltages involved any atom/molecule coming close to the edge at the base of the cathode where the breakdown first occurs is basically ripped apart by the strength of the E field.

The point is not where it first occurs but that there is a slight bias in the orientation of the polar molecules that follows the potential lines of the field. This molecules will be like small wires that guide the plasma and diminishes the resistance. According to the Nov. 11th report, resistance was one of the causes for the slower formation of the pinch.

[MTd2]

The idea is using polar molecules to shorten the time of ionization. Molecules would align faster and the density of the plasma would be higher since electrons would have less time to scatter from the hot zone. Why not 6Li2H? http://en.wikipedia.org/wiki/Lithium_hydride

I wasn’t thinking about using heavy water to be an end of the research. Just to see if the idea is feasible, this is why I didn’t consider the Bremsstrahlung.

[MTd2]

I must admit that the thread title is a bit misleading. I just wanted to know what possibly made it harder to achieve higher yields. I am not really asking if people are “lazy”.

[MTd2]

1.So, it is possible that right now you guys achieved 100J but no one besides you or the investors know, right?
2.If this is the case, will you publish on Nature?

[MTd2]

Well, IFS got 10^14 neutrons last week, which means on the order of 10-100J. They didn’t put on a pear review paper.

[MTd2]

Hmm. But previous records were posted on the front page, like this one:

https://focusfusion.org/index.php/site/article/new_calibration_confirms_ff-1s_high_fusion_yields/

[MTd2]

I am not trying to be a nasty guy and begging for things going as planned. I am just asking for the experimental details.

[MTd2]

But what I mean is not a proof but what was the result from the shots at those, supposedly, parameters. Was it a different curve? Did the curve inflected, did it bend? And if they were not shot, what the cause of the equipment not responding at the given conditions?

[MTd2]

There were some clear patterns on the October news’ post. Firing at 30Torr and at 1.7 (instead of 2.2)micro seconds pinch would get the yield close to 10Joules @1MA and @35KV which is just slightly better then the end of october. With 10banks, as it was done last week, 1.3MA should be achieved, and thus, about 30J. What went wrong?

[MTd2]

The budget is quite tight, you know.

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