Electrode Degradation Solution?

[dash]

Somewhere I read that there was a concern about electrode degradation in focus fusion. Ah, here’s the link:

http://talk-polywell.org/bb/viewtopic.php?t=1382

MSimon wrote “They do have a little problem with electrode erosion.”

I wonder if you could stop the current by having a rotating insulator like a fan-blade, maybe made out of glass. Maybe the electrode erodes because of the very high current spike when the magnetic field collapses? An insulator moving in front of the electrode to cut off the current could maybe protect the electrode?

Just an idea.

-Dave

[Aeronaut]

dash wrote: Somewhere I read that there was a concern about electrode degradation in focus fusion. Ah, here’s the link:

http://talk-polywell.org/bb/viewtopic.php?t=1382

MSimon wrote “They do have a little problem with electrode erosion.”

I wonder if you could stop the current by having a rotating insulator like a fan-blade, maybe made out of glass. Maybe the electrode erodes because of the very high current spike when the magnetic field collapses? An insulator moving in front of the electrode to cut off the current could maybe protect the electrode?

Just an idea.

-Dave

Msimon knows his stuff. I believe he learned it as a Navy reactor operator. Art Carlson is a practicing, licensed fission engineer, so I pay close attention to what they say. Including the problems with focusing six electromagnets that we don’t have to buy or try to shrink.

I began understanding FF as a series of electromagnets that culminate in (hopefully) around 12 GG, stronger than any other fusion reactor’s field. But the only way to get there is to dump around 2-3MA into the anode for that brief 10pS(?) of every cycle. More input current means more energy gets transferred into the plasmoid.

The main challenges for anode life are the input current peak and how well we can cool the anode, which in turn will determine how fast it will be pulsed (how much power it produces).

[dash]

Aeronaut wrote: I began understanding FF as a series of electromagnets that culminate in (hopefully) around 12 GG, stronger than any other fusion reactor’s field. But the only way to get there is to dump around 2-3MA into the anode for that brief 10pS(?) of every cycle. More input current means more energy gets transferred into the plasmoid.

I’m hearing that the period of current flow is so brief that no physical spinning fan-type insulator could actually serve.

However I want to make sure I’m understanding this. Are you saying 10pS (10 picoseconds) of current must flow each cycle? Let’s examine that.

1 picosecond is 1/1000th of a nanosecond. According to wikipedia http://en.wikipedia.org/wiki/Picosecond light travels 1mm in 3.3 picoseconds (but it’s a simple calculation anyway). So in 10pS light can travel 3mm. Is this the size of the focus fusion pinching involved?

It’s like the whole thing can fit inside an almond.

-Dave

[Aeronaut]

dash wrote:

I began understanding FF as a series of electromagnets that culminate in (hopefully) around 12 GG, stronger than any other fusion reactor’s field. But the only way to get there is to dump around 2-3MA into the anode for that brief 10pS(?) of every cycle. More input current means more energy gets transferred into the plasmoid.

I’m hearing that the period of current flow is so brief that no physical spinning fan-type insulator could actually serve.

However I want to make sure I’m understanding this. Are you saying 10pS (10 picoseconds) of current must flow each cycle? Let’s examine that.

1 picosecond is 1/1000th of a nanosecond. According to wikipedia http://en.wikipedia.org/wiki/Picosecond light travels 1mm in 3.3 picoseconds (but it’s a simple calculation anyway). So in 10pS light can travel 3mm. Is this the size of the focus fusion pinching involved?

It’s like the whole thing can fit inside an almond.

-Dave

Dave, I’m guessing at the runout timeframe (the plasma sheaths traveling up the anode). That’s sure to be studied and maybe tweaked in the next year or so.

What’s really easy to miss in this machine is how fast everything happens and that the plasmoid is measured in microns. (!) When you stop to think about it, a smaller plasmoid is easier to compress. As long as it encapsulates enough fuel to get the desired energy output per pulse, we should be good(er) to go. A large, low density plasma (and electromagnets) are some of ITER’s major challenges.

[dash]

Aeronaut wrote: What’s really easy to miss in this machine is how fast everything happens and that the plasmoid is measured in microns. (!) When you stop to think about it, a smaller plasmoid is easier to compress. As long as it encapsulates enough fuel to get the desired energy output per pulse, we should be good(er) to go. A large, low density plasma (and electromagnets) are some of ITER’s major challenges.

Thanks for your response, it does make more sense now.

I remember in Big Bang Never Happened Eric talks about a power company in Sweden or somewhere that called in some plasma experts because their DC power switch or whatever was failing and a massive electrical spike was blowing out circuits. The problem turned out to be some widget had too low ion pressure so all the ions were forced to one side of the chamber and this killed the current flow, which collapsed the magnetic field that had built up, causing the massive voltage spike.

I wonder if such a mechanism could be used intentionally to pulse the high current.

-Dave

[Aeronaut]

Even if I had read BBNH, I wouldn’t be able to follow most of it.

Two things we don’t want to do with FF is interrupt electrical or magnetic flows. Those are the machine.

[dash]

Aeronaut wrote: Even if I had read BBNH, I wouldn’t be able to follow most of it.

Two things we don’t want to do with FF is interrupt electrical or magnetic flows. Those are the machine.

Why wouldn’t you be able to follow most of it?

Anyway the principle of focus fusion is to start a big current flowing, which gives rise to a magnetic field, then cut off the current, which causes a collapse in the magnetic field, which causes the pinching effect which creates the fusion. The whole thing is pulsed, isn’t it?

Maybe my understanding is completely wrong — sorry!

-Dave

[Aeronaut]

dash wrote:

Even if I had read BBNH, I wouldn’t be able to follow most of it.

Two things we don’t want to do with FF is interrupt electrical or magnetic flows. Those are the machine.

Why wouldn’t you be able to follow most of it?

Anyway the principle of focus fusion is to start a big current flowing, which gives rise to a magnetic field, then cut off the current, which causes a collapse in the magnetic field, which causes the pinching effect which creates the fusion. The whole thing is pulsed, isn’t it?

Maybe my understanding is completely wrong — sorry!

-Dave

I seem to be one of the few around here without formal physics and higher math training, lol.

Yes, Eric’s estimating 330 pulses per second to produce 5MW of net electric energy. (Don’t tell Brian I told you this, but that should also produce ~17 MBTU/hr of “waste” heat available where co-generation is desirable). The pulsed nature makes it immune to runaway chain reactions and meltdowns.

You have to look close to see this sometimes, but there is a string of instabilities, each flowing smoothly into the next, so it can be easily mistaken for a single field charging and discharging. Other than that, you’re on the right track. You dump a lot of energy into the “spark plug” from the input capacitor bank, which will be recharged at the end of the cycle. All other electricity- the profit- ends up in the output cap bank, so the machine begins and ends in an equilibrium state, more or less, ignoring maybe some stray heat.

One of the things making pB11 the ideal fuel is that its far more stringent ignition requirements make it inherently safer than any other fusion fuel currently being considered.

[Brian H]

Aeronaut wrote:

Even if I had read BBNH, I wouldn’t be able to follow most of it.

Two things we don’t want to do with FF is interrupt electrical or magnetic flows. Those are the machine.

Why wouldn’t you be able to follow most of it?

Anyway the principle of focus fusion is to start a big current flowing, which gives rise to a magnetic field, then cut off the current, which causes a collapse in the magnetic field, which causes the pinching effect which creates the fusion. The whole thing is pulsed, isn’t it?

Maybe my understanding is completely wrong — sorry!

-Dave

I seem to be one of the few around here without formal physics and higher math training, lol.

Yes, Eric’s estimating 330 pulses per second to produce 5MW of net electric energy. (Don’t tell Brian I told you this, but that should also produce ~17 MBTU/hr of “waste” heat available where co-generation is desirable). …..
But of course it’s never desirable because the co-generation equipment would cost way more than just adding another FF generator or two to make the heat from the current directly. With resistance coils. Also called hotplates. See your electric range and oven for examples. 😛

[jamesr]

I would think a lot will be learned from the ITER like wall experiments due to take place in JET soon

I know the plasma conditions are somewhat different in a tokamak, but the fundamentals of high energy ions colliding with the wall/electrode are similar.
They are looking at tungsten coated carbon fibre componsites for the divertor plates which take the brunt of the ion flux, and berylium on inconel (a nickel alloy) for the rest of the wall.

The goal in the tokamak is to stop high Z (atomic number) materials being sputtered or boiled off the surface and polluting the plasma. High Z ions in the plasma will result in higher bremstrahlung radiation losses and cool the plasma.

see Overview of the ITER-like wall project G F Matthews et al (2007)

[Aeronaut]

jamesr wrote: I would think a lot will be learned from the ITER like wall experiments due to take place in JET soon

I know the plasma conditions are somewhat different in a tokamak, but the fundamentals of high energy ions colliding with the wall/electrode are similar.
They are looking at tungsten coated carbon fibre componsites for the divertor plates which take the brunt of the ion flux, and berylium on inconel (a nickel alloy) for the rest of the wall.

The goal in the tokamak is to stop high Z (atomic number) materials being sputtered or boiled off the surface and polluting the plasma. High Z ions in the plasma will result in higher bremstrahlung radiation losses and cool the plasma.

see Overview of the ITER-like wall project G F Matthews et al (2007)

Brian, the reason I keep bringing up the co-generation is that the thermal energy is over 50% of the energy produced by the reaction. Also, at this point, FF is a lot more useful for making cheap(er) heat than cheap(er) electricity. The higher we get above unity, the more valid your viewpoint becomes.

Jamesr, Focus Fusion is a Dense Plasma Focus designed to burn pB-11 to harvest ions and X-rays in seperate direct conversion processes. ITER is a low density plasma designed to burn Dueterium to create neutrons that will make steam like in a conventional fission plant. The two design philosophies and resulting machinery reflects this. ITER is useful for studying plasma confinement and long-duration burns, not for producing cheap or safe electricity.

[Brian H]

I think James is suggesting that some date related to materials degradation and plasma contamination might be applicable, considering that both have solid surfaces exposed to plasma. But the high temperatures and fluxes in the FF model are miniscule, and confined to microscopic plasmoids.

[Aeronaut]

Agreed.

[jamesr]

I’m fully aware of what DPF & ITER are. As Brian said, I was trying to suggest that although some may regard the large scale & expensive tokamak projects as ‘the enemy’, there is a lot of valuable research going on in that field to do with materials properties and the interactions of plasmas with solid interfacing components.

Some of this may be applicable to the plasma/solid boundaries in a DPF. We need to take advantage of all the modelling and experimental results they get.

I should disclose my interest – I have just finished a Masters in nuclear physics, and will be starting a PhD in a few weeks modelling edge turbulence and instabilities in tokamaks and stellarators. Initially using data from the Mega Amp Spherical Tokamak (MAST) at Culham, UK and the Large Helical Device (LHD) in Japan.

Although my research may be from the mainstream side (I needed funding), I hope to be able to apply it different scenarios like focus fusion.

James

[Brian H]

jamesr wrote: I’m fully aware of what DPF & ITER are. As Brian said, I was trying to suggest that although some may regard the large scale & expensive tokamak projects as ‘the enemy’, there is a lot of valuable research going on in that field to do with materials properties and the interactions of plasmas with solid interfacing components.

Some of this may be applicable to the plasma/solid boundaries in a DPF. We need to take advantage of all the modelling and experimental results they get.

I should disclose my interest – I have just finished a Masters in nuclear physics, and will be starting a PhD in a few weeks modelling edge turbulence and instabilities in tokamaks and stellarators. Initially using data from the Mega Amp Spherical Tokamak (MAST) at Culham, UK and the Large Helical Device (LHD) in Japan.

Although my research may be from the mainstream side (I needed funding), I hope to be able to apply it different scenarios like focus fusion.

James

Did you throw in a reference to global warming implications, just to multiply your funding? 😉 :cheese: Sorry! Just kidding!

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