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In the picture you attach, I don’t see how you accelerate the plasma to the speeds of ~100 km/s required of the axial phase of the plasma focus and the even faster speeds for the radial implosion. In the configuration you show, the plasma collides in the axial direction which is parallel to the magnetic field. The plasma density is so low that the particles will fly past each other and never meet the conditions of fusion.

The electrodes are a problem in a production scale machine but heating is only one problem. There are other plasma focus like configurations that have different problems but the electrodes are possibly more agreeable to thermal management. There are concepts of imploding plasma using other plasma current being pursued by a company called HyperV. Take a look. This concept looks something like the HyperV idea.

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Materials are likely to plague fusion long after the Q>1 condition is met. X-rays are a problem for the anode but it’s erosion from other aspects like hot plasma (potentially chemically corrosive) and particle beams are also important. A number of researchers have looked at some of the lifetime problems of electrodes. Admittedly, x-rays were not the problem they could be in the LPP pinch but the other lifetime limiting issues are a problem for Be. I suspect a compromise will be required before it’s over. It might be a materials compromise or a lifetime compromise.

I know in our machines that SS304 works well at low current (~100kA), refractory metals work better at modest current (~0.5MA) but you can get by with SS304. Metals like Aluminum are miserable even at low currents. Although Copper works OK, it is inferior to SS304. We aren’t the only ones to observe it. Groups in India, Pakistan and Singapore have published similar conclusions.

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MEMs are less than 100 um features and smaller. It is usually about repeating a pattern like a microchip in lithography.

Electrodes vary from machine to machine, but I would say they are macroscopic objects (>1 mm). At the ~2MA level the anodes tends to be 5-10 cm in diameter with lengths over 20 cm in some cases. It is perfect territory for CNC and other approaches. 3D printing might make it easier to install cooling channels and other features in an anode that are difficult to do with conventional machining.

I’ve been told for tungsten MEMS techniques that molds are sometimes used to hold the powder in place. It is a two step process. A plastic-type material comes out of a 3D printer. The powder is poured in and a laser is used to locally melt the tungsten around the mold in a way that doesn’t damage the mold. Powder can be added as the process moves forward in a layer by layer approach to add more material. The second step is like 3D printing but I’m not sure it is technically 3D printing.

If “highly packed powder” is used, it probably means 80% of theoretical density. Typical tungsten vendors like McMaster-Carr sell rods at ~80% theoretical density.

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Huh. I know that 3D printing is used for making some MEMs devices at lower cost and faster than say lithography. I’m sure it will take time to get to full scale stuff up but I thought it was closer to real macroscopic items. I’m sure it will be difficult to compete with CNC technology for some time to come.

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I agree with Joe’s comment up to point of “eliminating most concerns”. As with fission, fusion could find unexpected and unintended consequences that drive up costs. I agree that radioactive consequences are far less likely with the 11B-p reaction depending upon the choice of materials around the pinch, other concerns could crop up. I don’t have a crystal ball but I can tell you from operating PF devices and other pulse power devices that something always seems to come up that was unexpected or unintended. I admit that some unintended and unexpected things were quite wonderful while others were very disappointing. For example, high repetition rate devices tend to very loud and can shake the ground. Probably fine for a boat but on a truck it might require extra resources in excess of radiation shielding. On the upside we’ve noticed that operating at higher temperatures improves the fusion yield so increasing the repetition rate might lead to lower currents and the same fusion yield per shot.

If you are investing in this technology do it because you believe the problems can be solved. If you believe the problems are solved, I think you will be disappointed with the lack of return on investment.

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The one that I am aware of is reactions of the alpha particles with Beryllium (Be). The reaction combines an alpha particle and the Be-9 to make Carbon-12 (C-12) and a neutron. The alpha+Be-9 reaction is commonly used to make small neutron sources. Common sources rely on ~4 MeV alpha particles but I believe the reaction is exothermic other than that pesky Coulomb barrier problem. Other reactions would depend upon the specific materials that make up the first wall the system and the electrodes. I know Be has come up often in the discussions of the FoFu anode. The usual data bases did not have a reaction cross section but it has to be reasonable if the reaction is used in commercial neutron sources. This reaction alone might be enough to produce a significant neutron flux. The Beryllium will not be radioactive because the product is C-12.

It’s not at all clear to me that a Be anode can survive in FoFu-1 given that significant quantities of SS304 were observed to be eroded on smaller machines by Bures et al (DOI: 10.1109/TPS.2012.2183648). That is a bigger picture issue about x-ray absorption and electrode lifetime.

Another source that could contribute is D-D. If the fuel gas is isotopically pure, this reaction should not take place. More details of the vacuum chamber and electrodes are required to address any other reactions that might produce neutrons.

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Pretty cool stuff. I can’t speak for tungsten, but Molybdenum and Niobium are easy enough to machine that it only takes a couple weeks to get parts made. If you have an experiment planned in advance like different electrode lengths or diameters, the parts can be made in parallel.

It is not clear to me that 3D printing is producing “bulk” properties quoted for materials like tensile strength and conductivity. If 3D printing is as good a bulk it could be an interesting path forward.

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The alpha particles are directional if they travel with the ion beam. However, directed alpha particles do not guarantee directed neutrons. For neutron collimation, you typically require that the kinetic energy of the particle driving the reaction is greater than the energy released in the neutron producing reaction. LLNL had shown how you get directed neutrons using specific reactions with unique properties. However, directed neutron scatter and become isotropic neutrons.

I agree that neutron energy is important in terms of the neutron population, but the neutrons are likely to be reasonably energetic (>500 keV) which means activation of most common materials that make up capacitors and current carrying components. Thermal neutrons react very well with most materials so you could have a significant activation. 10 kW of heat in the context of more than 100 kW of heat is not a big deal.

The number came from a discussion on the site. I don’t know the source. I wouldn’t be shocked if it came from Eric or someone close to the project. He has been working on this concept for a long while. I’m sure he’s thought through the system and potential down falls.

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FF is probably going to need some neutron shielding. The alpha particles will generate some neutrons and there isn’t much to stop it. I don’t remember the number but I know Zapkitty commented on it a while back. I think the number was something like 0.2% of the energy output. If my memory is even so-so, that is 10 kW of neutrons is a big deal. The neutron yield is enough to be a concern from a regulatory stand point. I’m sure the activation decay is fast depending on the surrounding materials. No energy source is perfect but some are far better than others….if they work.

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I view the problem as one of v, velocity, in the . If the ion distribution is Maxwellian, the problem is pretty straightforward as you described. The real problem is when the ion distribution must be calculated. If you know you have a Maxwellian distribution, you can go forth with relative ease. The problem in Tokamek, Z-pinches fusion and other plasma based systems is the ions can have bumps on the tail of the distribution. I am not familiar with Sonoluminescence based fusion techniques but my guess is they have a thermal distribution due to a large collision frequency and the absence of a magnetic field. The laser, if powerful (>1 TW), could lead to fast ions but you need to do some calculations on the thermalization time of the ions. If the thermalization time is short compared to other time scales like the applied power pulse or some characteristic lifetime, you can assume a Maxwellian distribution with reasonable accuracy. Other sources of fusion are not so lucky in a computational sense.

One could argue that the fusion cross section is not taken in fine enough increments but that is the typical problem of cross section data. More could be done but the gains are viewed as small at this time.

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Best of luck with the arcing.

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zapkitty wrote:

A Q>1 PF could be filled with D2 or DT and produce a large burst of neutrons coupled with a 200 Hz drive.

… and what happens to the DPF structure in that 200 Hz neutronic environment?

Key word is illusion. It would be a difficult conversion (Eric said it already) in practical terms but the idea of “bad” is all it takes for some folks. Unfortunately some of those folks are in positions of power.

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I’m happy to hear you have open minded investors.

Glad to hear there aren’t any glitches with DoD and DHS. Some of those folks might be crazy but they can’t just come and take you in the night. You get a visit to warn you that your activities have been reclassified and the consequences. All these issues can be negotiated but it is a resource game. The gov’t strategy I’ve run up against is the attempt to exhaust resources of small companies by asking you to prove everything is fine. I hope it doesn’t come to that.

AaronB, fusion energy is not the issue I’m worried about. Neutron based interrogation systems are a touchy technology with DoD and DHS. Both have funded PF research as an active interrogation source to find all sorts of “bad” stuff. A Q>1 PF could be filled with D2 or DT and produce a large burst of neutrons coupled with a 200 Hz drive. An intense neutron source is also a concern for sub-critical fission systems that could convert 238U to 239Pu without enriched fuel. You suddenly find your technology in the isotope production world without ever meaning to be. Probably an inefficient way to produce Pu. DD could also be used to produce T. 5 MW at 200 Hz is 25 kJ net per shot so something like 100 kJ produced in the burst so ~1E17 Tritrons per burst from DD (of course this assumes DD is as good a p-11B which is close enough for back of envelope) or 2E19 tritons per second or 0.5 Curie per second. I won’t claim it is a scary number in itself but the implications are a bit concerning considering you don’t need a fission reactor and special fuel loading to produce the T. I can think of a few folks in the US and beyond that have an interest in such a system. The other isotope of interest from DD is 3He. An alternative source of 3He is badly needed. These production rates might be interesting as 3He and T are produced at the same rate. Four hours to produce enough 3He to fill a detector is pretty interesting.

My intention is not to be negative but to point out that the noble intention of clean fusion energy can be converted into the illusion of weapon’s tech without much thought.

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It makes me sad to see that international collaboration has to be between so called friendly nations. Expanding a network of scientists is almost always a good idea.

From a business side I would be worried about the feelings of investors and potential investors. I agree that the US attitude toward Iran is deplorable, but how do the folks with the cash feel? Can Q>1 put aside concerns about foreign collaborations? I don’t know the answer. I hope there are some open minded folks with big wallets.

My concern from a political side is not Dept of State or Treasury. Worry about DoD and DHS. If Q>1 happens, the technology will likely show up on a military restricted technology list. Once that happens all the publications will be clamped under International Trafficking of Arms Restrictions. If you run afoul of those, you end up in jail. Anyone who knows about plasma flow control has heard about J. Reece Roth formerly of U. of Tennessee. Instead of living out his golden years at home, he’s rotting in a jail for taking the wrong laptop to China. I hope it doesn’t come to an ITAR classification but if it does, publishing gets a lot harder. I’ve had to use very careful language to get my PF publications past ITAR reviewers. A collaboration is more than a strike against you with people like that. I was lucky to have folks that supported the work and wanted it published. God forbid you run across someone that knows nothing about the science and sees terrorists everywhere. If anyone is an APS member, check out the story in last month’s Physic’s Today about secrecy and the atom bomb for a flavor.

Best of luck navigating the choppy seas of science, business and politics.

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andrewmdodson wrote: http://www.evincetechnology.com/tech_overview.html

possibility of diamond switches evolving soon into something useful for the focus fusion project?

The website is very vague. My comment on using field emission electron sources is the limited current in the trigger. One should note that diamond is not a tickle trigger like Si. It usually takes a substantial trigger to turn diamond on and the trigger needs to stay on to keep the switch conducting due to the short carrier lifetime (~1ns). Laser triggered diamond switches have this problem as the necessary laser intensity is difficult to maintain for more than a few ns. It seems they are targeting power grids which is a very different beast than pulse power. I know diamond has come a long way due to work by groups like Diamond Detectors Limited, but the trigger is still the weakness. This is the reason diamond is a radiation detector right now. Last I checked and it has been a while, these type of switches are limited to ~1 kA. Going to a 3 MA system will take many components in parallel. The missing piece is the voltage hold off. Ideally, you do not want to have switches in series. Switches in parallel are not a much of a problem. The switch is going to have to hold ~60 kV. Again, it’s been a while but diamond has been tested successfully to 50 kV in photo conducting configurations.

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