[Henning]

Henning wrote: I’m worried that coating the expensive tungsten electrodes with silver will make them worthless.

Wouldn’t it be better to mill cheaper copper electrodes and coat them? Copper is easier to handle anyway. Or any other easily millable metal.

As I understand, the surface evaporates, so the underlying material is unimportant. Or am I wrong?

Yes it will delay the experiments further, and will cost several thousand dollars.

Erm, now I remember why a non tungsten-cathode is a bad idea. Firstly the sawtooth at the inner rim next to the insulator needs to be tungsten, otherwise they will evaporate too quickly. Secondly the cathode should be monolithic. So these two factors rule out a copper cathode. With beryllium it’s another issue, as it’s melting point is higher.

[Henning]

I’m worried that coating the expensive tungsten electrodes with silver will make them worthless.

Wouldn’t it be better to mill cheaper copper electrodes and coat them? Copper is easier to handle anyway. Or any other easily millable metal.

As I understand, the surface evaporates, so the underlying material is unimportant. Or am I wrong?

Yes it will delay the experiments further, and will cost several thousand dollars.

[Henning]

Rocket Surgeon wrote:
1) How well does/would a DPF fusion device work with D-He3 fuel? I know LPP is aiming to use p-B11 and I remember reading that DPF works better for heavy fuels, BUT D-He3 has lower ignition conditions doesn’t it? Would it make sense to convert over to D-He3 if/when a good source of He3 was accessed?

The DPF now reaches consistently temperatures high enough for p11B fuel, see latest LPP report.

Rocket Surgeon wrote:
2) Can a DPF be used to create a beam of high energy/temperature Ions without fusing them? or would there be a better way to do this?

A low power DPF (actually low current DPF), or a DPF with diffuse pinch, creates a beam of high energy ions without fusing.

So the DPF was researched as an ion thruster around 2000 by Texas A&M University for NASA, but there already fusion occured. Eric Lerner was part of that team.

Rocket Surgeon wrote:
3) How well does DPF fusion scale and how do you scale it? To increase the fusion yeild/ energy of the Ion beams do you up the voltage/current? make the DPF bigger? longer? increase the cathode radius or shrink the anode? What varible do you change in order to increase the fusion yeild assuming you have no restrictions on cost?

Scaling by itself is not the problem. You can scale it linearily in size as well in power. The scaling law for the DPF seems to be I^4 (current to the fourth power). So the goal is pumping as much energy through a small device as possible.

The problem is the cooling of the anode, which probably isn’t scaleable as easily. The proposition is to have a beryllium anode through which helium gas is pumped for cooling.

[Henning]

There are already a few posts on Daily Kos about Focus Fusion, mainly by Keith Pickering:
http://cookiesandmilk.dailykos.com/story/2009/10/21/795402/-New-fusion-device-achieves-plasmoid-pinch-UPDATED
http://cookiesandmilk.dailykos.com/story/2010/05/07/864141/-Fusion-progress-in-Dense-Plasma-Focus-experiments
http://cookiesandmilk.dailykos.com/story/2009/11/05/801060/-Focus-Fusion-Unity-Close

But why not post an update?

[Henning]

Interesting read, although I’ve just skimmed it. Not that I’m qualified by any means.

They also compare their materials (2H-GaN, 4H-SiC, 6H-SiC) to diamond (page 18).

The 16 kV stated in the introduction is in the ballpark required for Focus Fusion (about 40 kV), but the current needs to be increased about a thousandfold (1.4 kA compared to about 1 MA for Focus Fusion).

And I’m not sure, if a minimum resistance of 1 Ohms isn’t too high for a 1 MA current.

Closing speed is great though: 0.1 ns to 1.0 ns.

[Henning]

How fast would the tungsten re-oxidise? It’s maybe worth to get the oxygen off, but when the electrodes get installed, the tungsten re-oxidises. But maybe the layer is thinner, and the rest can be blast off with fewer shots.

Or filling the vacuum chamber with hot hydrogen. But here the Mylar (PE) insulation wouldn’t survive.

[Henning]

I think it’s just a vacuum tube with an electron beam, where the electron beam hits a conducting plate and gets diverted when switched off. So as the Kickstarter project says, not much more than a TV tube (cathode ray tube). Nothing fancy, might have been in use since the 30s.

[Henning]

Ivy Matt wrote:

Reading the FOA, the following caught my notice:

ARPA-E requires all work under ARPA-E funding agreements to be performed in the United States – i.e., Prime Recipients must expend 100% of the Total Project Cost in the United States. However, Applicants may request a waiver of this requirement where their project would materially benefit from, or otherwise requires, certain work to be performed overseas.

Given that the tungsten cathode is being purchased from and machined in China, I wonder if this would require a waiver. I would think a waiver ought to be granted if there are no facilities in the United States capable of machining it. (Although there may be another way to get a tungsten cathode soon.) Or, if the award only covers work done using the beryllium electrodes, I suppose a waiver would not be necessary.

Stupid idea: Create a company called “LPP Import” that imports all the required stuff. 😉

[Henning]

Maybe describe the Focus Fusion technology as “dense plasma focus” in your tables, as you have put together all those polywellish devices. That’s from which it’s derived.

[Henning]

Here’s the first part of the paper, already peer reviewed:

http://www.sciencedirect.com/science/article/pii/S0370269314006686

[Henning]

Joeviocoe wrote:
3) Would the Beryllium electrodes need a thin surface plating of Tungsten (similar to how the Copper electrodes were Silver plated)… to prevent the loss of proper filaments and reduce vaporization?
Or would that thin surface absorb too much X-Rays and burn up?

No. Beryllium is chosen because it’s transparent to x-rays. Plating the electrodes with Tungsten is as if you’re painting them black.

[Henning]

rimmini: What TED video are you talking about? Can you give me a link?

Or do you mean the “Solve for X” video: https://www.solveforx.com/moonshots/aneutronic-fusion

[Henning]

Please be aware, that the discharge time is crucial. The switch has to operate 45 kV / 2.8 MA within 100 µs or better (something of this order). And the capacitors / electric sources have to supply them within that time.

I don’t have the graphs currently, but this is a steep increase in power over time.

[Henning]

The Beryllium itself will not vanish. At most it will be distributed around the vacuum chamber, vacuum pump, exhaust (where it should be filtered out). The electrodes need to be replaced because they don’t have the perfect shape anymore, so reactions don’t deliver enough energy anymore. Melting them and recasting (or re-3D-ing) is all you need.

[Henning]

Maybe the crowdfunding campaign should be synchronized with the monolithic cathode being installed. So that with every new crowdfunding day a new fusion record is obtained. This gets people more interested.

So with the crowdfunding planned in April and monolithic cathode coming in May, the interesting part is only happening after the campaign has ended.

[Author]

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