[Joeviocoe]

delt0r wrote: If you could get a fast opening switch with larger than 40kV standoff, we would all be using magnetic energy storage. You don’t even need superconductors. At 1T you can store 400kJ per m^3 which is *easy* (this is without magnetic materials). With materials you get much higher densities. It would be like a switched mode power supply on steroids. You can get high voltages easily and high currents with some effort.

Catch is opening switches like this just don’t exist. If we move to solid state, say diamond or SiC switches that don’t just np junctions (avoids the voltage drop problem), then perhaps something could be developed.

Could you give an example of “magnetic energy storage” in use today? Is 1 Tesla common for this?

[Joeviocoe]

asymmetric_implosion wrote: The switch problem is the materials erode leading to a plasma/vapor of that metal. When the current turns off, the plasma/vapor expand and coat all surfaces. After some number of shots, a thin metal film builds up on the insulating ceramics or plastics that normally hold off the high voltage. The finite conductivity can lead to problems with voltage hold off, excessive leakage current in the switch. These conditions can lead to pre-fire and large jitter.

That is why I mentioned a gas flow system that keeps the material vapor from coating the switch internals. The flow gas must be inert and kept hot to prevent solidification. But that should be doable.

asymmetric_implosion wrote:
Many problems in fission can be mitigated. After fuel is burned it can be reprocessed extracting the useful components and burning the other products in an accelerator. Proliferation is a concern but thorium cycles can by-pass many of those concerns. Ask the Indians about whether they are investing in fusion or thorium fission. The Chinese have a more diverse picture but they are investing in tokameks for their fusion program.

I certainly like the diverse approach to energy that the world has in general. I wish the U.S. was as bold sometimes.
LFTRs and even Travelling Wave reactors are important to fund and develop regardless of any progress on the fusion front.
I was just remarking how improper it was to regard fission as an energy silver bullet when it was the ‘new thing’ on the block.
Focus Fusion may be the holy grail, but that just means it tackles many issues at once. But it won’t save the planet without help. Different reactors for larger marine propulsion or large centralized power needs. Stacking 100 DPFs seems impractical. A 100MW polywell might serve better.

[Joeviocoe]

asymmetric_implosion wrote:
Ahhh, the cheaper than coal argument. A little history…when fission was the new thing, business models were build around the electricity being free. This was after they demonstrated an actual power generating system. I hope the day comes when fusion is cost competitive with coal. That would be a huge victory. Don’t get me wrong, I like the idea of clean fusion energy. The problem is I’ve been disappointed so many times that I try to approach fusion and other problems as a skeptic and ask questions. I think the LPP approach is as viable as any other fusion concept at this point. I hope they make the breakthrough but it will be a long road after that to a working reactor.

For that, I love this axiom:

“Chindia” price: the price at which India and China would adapt a technology for
economic reasons. “Everything’s a toy until it reaches that point” –Vinod Khosla

The over-promise of fission was fuel in, waste out. Neither of which could truly be mitigated by technology. They were bounded by the physics. Fissile material must be mined and refined, could be proliferated, and is radioactive to handle. That is costly, and is inherent in the physics of the fuel. Same with the waste. Not much can be done about it.

Fusion, aneutronic especially, may be costly to build, but technology can advance enough to cheapen the process… since fuel input is inherently cheap, clean, abundant and safe.. and waste output is just heat and helium. Delicious!

[Joeviocoe]

Right now, I think LPP is focusing on getting reliable power output from the switches and capacitors for about 1 shot per every few hours.. and getting the jitter down. I don’t think they will be focusing too hard on getting cycle rates up to 200 Hz and the cycle life up to trillions of shots before replacement… until the feasibility of the physics is established. Are the other PF devices trying to redesign switches and caps for this purpose yet?

I know Eric mentioned getting new switches from Raytheon… but I don’t know what improvements he hopes for.
Eric? and elaboration on that?

[Joeviocoe]

asymmetric_implosion wrote: How do you stop erosion and redeposition? Stopping erosion is impossible so it must be minimized.

I think the welding industry has a solution that may work. Feed wire. If you have a materials problem, sometimes mechanical engineering can solve it. Let it erode away, provide a flow of gases to carry away deposits before they solidify, and shape the electrodes so that they can be fed in at a constant rate. I am not sure of current switch design though.

There may be many design opportunities that present themselves. Solutions that were never thought of before since they have lacked any real incentives.

[Joeviocoe]

asymmetric_implosion wrote:
One might argue that solid state technology could be force fit into this problem with the advantage of >1E9 shot lifetime. I believe that a 2MA, 70 kV bank can be built but the actual lifetime and the cost will likely be a problem. Solid state costs something like $1-10/Joule stored at this level. Gas switch technology is more like $0.01-0.1/Joule stored without any effort. A company called SRL built an 80 Hz, 260 kA PF device. It took a true pulse power genius (Rod Petr) to design the bank to operate a 8 kV. The next immediate question is why not operate at low voltage if it is easier? In a plasma focus there is a 10-20 mOhm loss due to the moving plasma that cannot be avoided. To overcome this impedance means a minimum of 20 kV to drive 2 MA. Account for the other losses in the switches, capacitors and bus bars and you are at 40 kV to drive 2 MA. If I am correct, FoFu-1 is at ~1 MA and 40 kV. Increasing the cap bank size does not help as you still cannot get around the 10-20 mOhm impedance in the moving plasma; it simply reduces the impedance of the bank. It will a great deal of resources to have a pulse power system that operates for 2 months at the 2 MA level without maintenance.

Okay, lets talk about solid state for a moment. Are you talking about solid-state switches or capacitors?
[em] I calculated 1 MJ stored in the capacitor bank for each shot … (50KV x 2MA = 1E11 watts for a 10 microsecond shot / 10^5 = 1 million watt-seconds / 3600 = 278 watt-hours = about 1 MegaJoule (MJ)[/em]
So that would be anywhere from $1mil to $10mil if that cost scaled linearly. *I would hope that at such high demand, manufacturers would build a lot of production capacity and drive down costs.
So that would ruin the price estimate that LPP currently has for the Focus Fusion device.

But even a $5 million dollar 1st generation 5MW fusion power generator ($1/watt) would still be hailed as a great achievement and still MUCH cheaper than the $30 billion dollar 1GW ($30/watt)…. IF THE CAPACITORS AND SWITCHES COULD LAST FOR YEARS.

Do solid state capacitors (Is there such a thing) have that potential, to last a REALLY long time?
Are there any non-capacitor methods to store electrical power that can absorb and release 100 MegaWatts of power in 10 microseconds with low jitter???

—————————————–

Okay, reading your second post. The economics certainly don’t favor any 5MW device that requires constant maintenance. Essentially, for Focus Fusion to be a viable economic venture… they will have to build a device that meets LPP’s claim of “lasting for 1 month” without any maintenance needs. And the replacement parts must be reasonable in price. Million dollar solid state switches and capacitors are not gonna cut it. There needs to be some serious development in the engineering.

If LPP can get away with only replacing electrodes every month, I think they could be much cheaper $/kilowatt-hour than even Coal.

Bottomline, this is a massive engineering problem that I look forward to seeing solutions for.. As an electrical engineering student, I might want to help tackle this myself 🙂
Hopefully, FoFu-1 will prove the feasibility of the physics and unleash some serious government funding. As LPP’s plan goes, a few hundred million dollars and maybe a thousand extra personnel, a few dozen extra engineers… let’s get it solved.

—————————————–

P.S. I asked about your background at the bottom of page 1… and would just like some context for all this knowledge you bring to these forums. Thanks.

[Joeviocoe]

asymmetric_implosion wrote: I have hope for the anode because you can use the physics of a highly directional beam to help you. The switches are the problem. I guess it is good for creating jobs and manufacturing to replace switches every few days if not every day. The switches are going to require a heavy investment to realize a 5 MW power plant operating at 200 Hz for more than a few days.

Can’t reliable switching (for greater than 2 months) be achieved by a greater number of capacitors and switch… at the sacrifice of the size of the whole system? Instead of 12, 48 capacitors for instance… or even 120, or 240 capacitors?

[Joeviocoe]

jimmarsen wrote: What about increasing the duration of a shot to increase yield? Is that feasible?

I don’t think so, the Dense Plasma Focus is basically a collapsing knot of plasma filaments. It is inherently unstable (in contrast to trying to make it stable like Tokamaks) which is good since the instability allows the plasmoid to fuse the fuel. But its “duration” is a physical, parameter really… and I think is a product of everything else. I don’t think they can change that independently.

You’ll hear them talking about nT (n tau) which is the product of density and confinement time. If by, “duration” you mean confinement time which allows for more fuel to be fused, and thus increased fusion yield… then “duration” has always been a factor that LPP has been trying to maximize. Along with density of the plasma, that makes up a critical part of attaining a net power output.

[Joeviocoe]

asymmetric_implosion wrote: My guess is that there is a mix of cost, engineering risk and possible physics limitations that will decide on how a repetition rate PF will be built. I can tell you this much, a 60 kA PF firing at 10 Hz sounds like an automatic weapon firing. A 3.5 MA Z-pinch causes the floor to move noticeably. A 20 MA Z-pinch feels like a small earthquake. Firing a 2-5 MA PF at 200 Hz will be an experience for those near by without some sort of seismic isolation. I feel for the operator.

Does the DPF produce force alone only one direction? If so, stacking 2 in opposing directions could dampen the seismic vibrations.

[Joeviocoe]

asymmetric_implosion wrote:

Does the physics of DPF prevent designing a larger device; are there engineering limitations?

Yes and no. The primary limitation encountered to date is the insulator between the anode and cathode in vacuum. Experiments have demonstrated a system without an insulator at 5 MA but the experiments were focused on soft x-ray production. Is the insulator the show stopper to scale up??? I don’t know for sure. Some experiments at 2 MA suggest a solution to the problem but it might drive the fusion yield away from optimum. This is a pressing point in PF physics that is actively researched because scaling up a PF to high current should cost less than a Z-pinch. The problem to date is that PF devices seem to show decreased fusion yield with currents above 1 MA. Z-pinch devices show a fall off at something like 300 kA. See the attached figure with PF devices and radial implosion Z-pinch devices as an example. This is data I’ve compiled from the 1970’s to present from peer-reviewed published lit including data from LPP. If you can scale up the device along the alpha=0.25 curve, you can get more fusion yield per shot. If the fusion yield (DD neutron yield) falls off at 2 MA or more, it seems that a smaller and high rep rate PF is the better option.

I thought that it was higher voltages that brokedown the insulator, not higher current. And that higher current, with higher cycle rates, causes the skin effect to heat the cathode unevenly causing damage.

And that the DPF fusion yields scale higher with increased current ( I^4.7 ) but that 3 MA would be optimal.

Am I completely wrong here?

[Joeviocoe]

jimmarsen wrote: Does the physics of DPF prevent designing a larger device; are there engineering limitations?

That question has been asked by many, me included. And from what I gather.. there are limitations that make larger devices a problem. 5MW was chosen for many good reasons.

But luckily, these devices will be small enough that you can stack 10, 20, or more in a single area. And as long as you can get rid of the waste heat (or use it separately), then it should be a very efficient use of space.
Still not as good as Gas Turbines or Diesel Generators for MW per sq. meter … but much better than Solar and wind even (and those are intermittently producing power). And when you account for the fuel needed for conventional power plants, fusion devices like these are so much better.

The main point LPP likes to focus on, is the fact that smaller generators can be place closer to the load. So instead of central power plants pushing power over hundreds of miles through transmission lines that waste energy, a single 5 WM DPF could be placed in several locations throughout the city, taking up a small space in existing electrical substations (where High Voltage power lines meet transformers on the ground to step down to neighborhood level voltages).
For large ships (cargo and cruise liners) and locations that require 50 MW – 100 MW in a centralized location, I’m not sure DPF is practical. Perhaps if Polywell works with pB11, that would be a great solution.

[Joeviocoe]

jimmarsen wrote: What about scaling up the yield per shot? Is that feasible?

That is the first thing they are trying to do. But there are many limits to that too. Yield scales to the 4.7th power of Current (I^4.7). But current is limited by MANY parts of the device. Capacitors, switches (low jitter needed), the electrodes especially need to handle the higher current. Once yield per shot is maximized, they can take it to the next limit of cycle rate… which have their own limitations too.

So they are estimating 132 kJ output from the plasmoid for each shot. After conversion losses and recycling 100 kJ for the next shot… that is 24.7 kJ net output for each shot. And they estimate that a production reactor could function at a cycle rate of 200 times per second and only need maintenance once a month.

These are bold claims that they will spend the next few years proving.

[Joeviocoe]

asymmetric_implosion,

I’m quite new to this forum, but have seen many posts describing the experiments you’re doing. But since you have so many posts, I cannot pin down the basics of your experiment. Do you actually have a DPF? Or is it something similar? What have you built, and for what purpose? This would help me understand the context of your knowledge here. Thanks.

[Joeviocoe]

vansig wrote: let’s imagine that if there’s even a single atomic layer of erosion per shot, that it would be in nanometer scale thicknesses; then a million shots later, we’re up to millimeter scale, and that could be quite significant.

1) Would a beryllium anode erode faster or slower than a copper anode?

2) Why can’t engineers use a secondary magnetic field localized to move the electron beam in a random direction, so it would take several thousands (if not millions) of shots before the beam hit the anode on the same spot twice?

3) How much reduction in the electron beam energy does the quantitative theory say will occur when using pB11 that absorbs most of the electrons to reheat the plasma? What percentage of electron energy compared to current levels of erosion using DD?

[Joeviocoe]

Lerner wrote: To be more exact, we expect that with higher plasmoid density, msot of the energy of the electron beam willbe absorbed before the elctrosn leave the plasmoid. Andoe erosion is still a major concern as the anode must be kept cool. Cooling is one of the three main engineering challenges.

What are the physical principles that allow the electron beam to be absorbed so well? Is it by shear density that prevents the electrons from leaving the plasmoid? Or is it because the + charge of Boron is 5 times greater than the Deuterium and thus 25 times (squaring law) greater at braking those electrons and converting their energy to bremsstrahlung?

[Author]

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