Magnetized inertial fusion (MIF)

[Francisl]

Nuclear Fusion Simulation Shows High-Gain Energy Output. Looks like they are using some ideas from the LPP system.

[asymmetric_implosion]

MAGLIF is a far cry from Focus Fusion. It seeds a strong magnetic field (~1 T) before a 26 MA pinch implodes a metal cylinder onto the preheated, magnetized DT fuel. The concept is supposed to take advantage of limiting electron heat transport by flux compressing the initial 1 T field to something like 20 T or beyond. The physics of the components are proven but the entire concept has yet to come together. Sandia has been promoting the concept for over a year at meetings. It is about as much a path to a fusion reactor as NIF. Another piece of nice physics that cannot be engineered at a reasonable cost. The system relies on recycling the vacuum transmission lines every shot at a 0.1 Hz repetition rate. It is also a thermal process which does not play to the strengths of a pinch device.

[Matt M]

How in heck are they going to create a heat exchanger that will efficiently
pull from a fusor like that and run a turbine? Just producing heat alone is
of no real value if you cannot use that heat to create electricity.

[asymmetric_implosion]

We are talking about two very different time scales. The time scale I was discussing was the pinch time. The B-field reduces the electron thermal conductivity in the plasma allowing the plasma to reach a higher temperature for its <1 us lifetime. The ions and neutrons produced in fusion can escape the magnetic field during the pinch. I'm not sure on all the details but some discussion on the conversion involved MHD conversion of the ion energy and a thermal cycle to deal extract the neutron heat. The MHD extraction would be on the pinch time scale but containing MeV ions is not possible in this configuration. The ions run away and get converted to electricity. The neutrons are free to do as they please so they thermalize in a blanket to breed more tritium and extract the heat at high temperature.

The concept is sound in the sense of the physics is proven but the engineering is going to be costly. They are talking about a 40-60 MA machine for the power plant. The designs requires a system with over 500,000 switches operating at 6 MV or more up to 0.1 Hz. The unit modules work but it is a long road to making hundreds of unit modules work together at low jitter.

Sandia is grasping at straws since NIF has come out saying they are the only path to fusion and that was their intention from Day 1. MAGLIF is more psychological than physics driven. If you think about it, what is the first comment made by skeptics such as myself? Fusion has never produced more energy than it took in. If Sandia can show a configuration, practical or not, that can demonstrate physics gain, it will excite people about fusion again. Strong fusion supporters should embrace the potential of breakeven on any concept because it will help the politics of fusion on the large scale. In particular this is a hybrid concept and one might argue that LPP is using a hybrid concept. The argument is simple from there. LPP can do the same as Sandia at lower cost, practical repetition rates and with fewer components.

[benf]

I came across this Sandia Lab MagLIF presentation on Sandia’s website, which illustrates the magnetic field design. Perhaps the control over the magnetic field and associated maths could be of some use in the future?

“Whatever the difficulties,” said Sandia manager Daniel Sinars, “we still want to find the answer to what Slutz (and co-author Roger Vesey) propose: Can magnetically driven inertial fusion work? We owe it to the country to understand how realistic this possibility is.”

I hope this quote doesn’t lead to another boondoggle of the NIF or Solyndra type….The DOE seems enamored with some projects that show high difficulty to produce…But I agree if they show that fusion net gain can be achieved, at least by simulation or in a lab. One hopes LPP will get there way ahead of them.:-)

[asymmetric_implosion]

MAGLIF is far from a NIF boondoggle. They did the testing up to this point on a dime (in big science terms). Z is already paid for so the proof of concept experiment is all that needs to be completed. If they have the funding, ~$5M, they could probably get it working in a couple years. The real problem is shot time on Z. You need to get in line a year or more in advance and the Z operations folks don’t like neutrons. I know they have done some tests with the metal shell with hydrogen. The magnetic field coils are about ready. If they are in the queue, they could have data by end of the year showing a Q of 0.5-0.8.

Bad news though, NIF will hit breakeven first. It is dubbed too big to fail by NNSA and others in DOE.

[jamesr]

asymmetric_implosion wrote:
Bad news though, NIF will hit breakeven first. It is dubbed too big to fail by NNSA and others in DOE.

NIF will fail – the only way they’re going to get ignition is by a clever PR redefinition of what ignition is.

They may be able to get the hot-spot at the centre of the pellet to ignite, but some new models show that if you take account of electron degeneracy properly, the alpha particles do not have sufficient stopping power to heat the compressed pellet and create a burn wave propagating outwards.

So I expect if NIF do come out with any news of having reached ignition, take it with a pinch of salt and look out for the burn-up fraction. Getting a pinpoint in the centre to ‘ignite’ is pointless unless it results in fusing of a reasonable fraction of the pellet.

[AaronB]

Maybe I’m a bit too optimistic, but I think the NIF guys will reach “real” ignition pretty soon. It is easy to be critical “based on current understanding and models”. Progress happens when we build on the past and expand into the unknown. Naturally, you can’t ignore the laws of nature, but you can look for stepping stones through them. Airplanes and space travel were impossible until we built the tools to do them. Modifying DNA was impossible until we built the tools. Elements were considered immutable until we mutated them with atom smashers. When one hundred approaches fail, the combined lessons learned plus a new idea will lead to success. It’s technological evolution, and in this case, there are intelligent designers all over the world working on it. Time, effort, money and brains will make it happen. I don’t know how, but it will.

For about four years, I was stationed at Edwards Air Force Base, which houses the Air Force’s Flight Test Center. They have a great museum that shows the history of flight development. It wasn’t a perfect process, and it had many setbacks and deaths. It takes a special kind of person to strap themselves into an untested aircraft and see what happens. You have to be willing to break things and suffer disasters when you’re involved in cutting-edge research. It just happens, but if you watch carefully and study the wreckage, you learn the limits and then find a way around them.

So, whether it is our project or NIF’s, the evolutionary curve will continue to grow, and eventually someone will figure it out. Then, over the next 50 years, we’ll probably see the same kind of development that happened in the aircraft industry.

[Brian H]

Well, james’ observation also applies to the Sandia simulation. Containment beyond an instant of the fusion plasma is the whole ball game. IMO, this is where the FF concept has such an overwhelming advantage. No hyper-complex tuning of protective magnetic/material shielding of vulnerable walls is necessary. That’s where the Devil’s Details make all other approaches “come a cropper”, to use an appropriate Briticism.

Note that the NIF is designed and appropriate for investigating fusion explosions. Adapting it to energy production is “kluges all the way down”. Same with Sandia’s Z-pinch and this variant. Note especially that excess HEAT is the desired and necessary intermediate for obtaining usable electricity. And extracting the heat from these rigs is some trick.

Note also that it is D-T fusion, meaning floods of hot neutrons trying to transmute the equipment into mischmetal. :coolcheese:

[asymmetric_implosion]

James: FF will only burn a tiny amount of fuel per shot. My guess is it will be on the same order as an optimized NIF. NIF may not be perfect and it will not be a viable fusion reactor but physics breakeven is likely. Engineering gain is another story…

Brian H: MAGLIF does not require a complex B-field. The magnetic field is the same as FoFu field (solenoid-like field). The difference is the magnitude. FF uses very weak fields while MAGLIF uses an ~1 T field. Both systems use flux compression on some level. The key difference in the SNL experiment is the B-field due to flux compression is strong enough to limit electron thermal conductivity to allow the plasma to stay hot. Flux compression is a proven method to increase B-field and gain some of the benefits described by Lerner’s theory without the formation of a plasmoid. The conversion of MAGLIF to MHD conversion is do-able. Of course people will use the neutrons to extract heat and that is less efficient theoretically than MHD conversion but MHD conversion has not been implemented on the large scale (to my knowledge). MHD pumps move liquid metals but that is a far cry from what is being proposed on FoFu-1. A simple rogowski coil may be enough to extract the beam energy which is efficient but the rest relies on photovoltaic-type technology (low efficiency) and probably thermal cycle (same old same old). I don’t think anyone can claim to know the exact ratios of these three outputs until it is tested.

Time will tell who gets there first but if I’m betting NIF is first. FoFu may beat Sandia but I could see SNL getting their next for one reason: resources. MAGLIF could produce an intense neutron source that NNSA (folks funding NIF as well) would like to have.

[jamesr]

asymmetric_implosion wrote: James: FF will only burn a tiny amount of fuel per shot. My guess is it will be on the same order as an optimized NIF. NIF may not be perfect and it will not be a viable fusion reactor but physics breakeven is likely. Engineering gain is another story…

Obviously if you include all the fuel in the DPF chamber only a tiny fraction is burnt, but of that confined in the plasmoid(s) then maybe upto 70% could be fused.

For NIF I think they’re hoping for ~40% (of the DT gas and ice shell – not including ablative layer), but if they don’t get a burn wave then I guess it’ll be more like 2%

[Brian H]

a_s;
“probably thermal cycle (same old same old).” Not a watt, unless you count such possible applications as heating nearby buildings with warm air, etc. The ancillary equipment to extract heat and convert it to electricity is not a) present, b) economic, or c) usable with the low-grade (low-temp) output of the FoFu.

As for the photovoltaic “inefficiency”, examine the “onion” design. It has perhaps thousands of layers/stages to extract a very high percentage of the X-ray energy.

And as with Z-pinches, sacrificing wires or metal cylinders or pellets etc. with every shot is, IMO, a complexity bridge way too far for continuous output. Murphy’s power grows exponentially with number of components.

[asymmetric_implosion]

Brian H wrote: a_s;
“probably thermal cycle (same old same old).” Not a watt, unless you count such possible applications as heating nearby buildings with warm air, etc. The ancillary equipment to extract heat and convert it to electricity is not a) present, b) economic, or c) usable with the low-grade (low-temp) output of the FoFu.

As for the photovoltaic “inefficiency”, examine the “onion” design. It has perhaps thousands of layers/stages to extract a very high percentage of the X-ray energy.

And as with Z-pinches, sacrificing wires or metal cylinders or pellets etc. with every shot is, IMO, a complexity bridge way too far for continuous output. Murphy’s power grows exponentially with number of components.

Low temp? I’ve seen numbers of 1000C floating around this site. That is a pretty good temperature for a thermal cycle with modest efficiency (~40%). I’ve looked at the onion. It will absorb x-rays but how much will turn into useful electrons? That is where the efficiency typically comes in. You can absorb 100% of the sunlight but only about 10% is converted to useful electrons. X-rays may convert more efficiently as they are well above the band gap but you are still limited on efficiency. I hope it is greater than 40%. I know heat will be generated by a FoFu power plant so the question is why not use it? Turbines on the 5 MW scale are small and efficient. A helium turbine in particular is very compact and efficient. It adds more electrons to the grid. Some cooling is going to be required of FoFu-1 so why not put that heat to good use rather than dump it into the air needlessly.

Z-pinches: I’m not saying that MAGLIF will ever be a viable power plant. I don’t think NIF is viable either. I’m simply saying that NIF and MAGLIF will reach breakeven. It will be a demonstration and nothing more. FoFu will demonstrate Q>1 well before a power plant is built if economically feasible. Using best guesses for numbers, NIF is producing something like 10 kJ of fusion energy per shot (DD) using 4 MJ of laser energy (I believe the bank is 400 MJ with 1% conversion to photons). MAGLIF will use 20 MJ of pulse power to get something like 10 kJ of fusion energy in the near term. FoFu uses more like 56 kJ to get ~1J of DD. So the math suggests that NIF has a physics Q of 0.0025, MAGLIF will couple no more than 33% of the stored energy to the load so MAGLIF is 0.015 and FoFu using the same 33% coupling to the pinch as MAGLIF has a Q of 5.4E-5. If all things were equal MAGLIF would get there first but NIF has more funding and they are running “bad loads” right now to test the models. When they get serious later this year I expect they will get to Q=0.5 pretty quickly (yes, physics Q). Q=0.5 puts NIF on par with JET which has demonstrated a Q=0.7 some time ago. MAGLIF will suffer from something like 10 shots per year so unless the models are spot on, it will take some time. FoFu, the smallest project with the least funding, will come in third on this list. One can argue with the exact numbers but they should be order of magnitude correct. Resources are likely to shape the results and NIF has the most resources by far. The first gate will be the physics Q>1 followed by the engineering Q>1. FoFu has the most straightforward road to get from physics Q>1 to engineering Q>1. NIF and MAGLIF have some serious hurdles after they show physics Q>1. The big question is whether a plasma focus (a two stage Z-pinch) can be made to show Q>1. I look forward to the answer over the next year or so.

[zapkitty]

asymmetric_implosion wrote:

a_s;
“probably thermal cycle (same old same old).” Not a watt, unless you count such possible applications as heating nearby buildings with warm air, etc. The ancillary equipment to extract heat and convert it to electricity is not a) present, b) economic, or c) usable with the low-grade (low-temp) output of the FoFu.

As for the photovoltaic “inefficiency”, examine the “onion” design. It has perhaps thousands of layers/stages to extract a very high percentage of the X-ray energy.

And as with Z-pinches, sacrificing wires or metal cylinders or pellets etc. with every shot is, IMO, a complexity bridge way too far for continuous output. Murphy’s power grows exponentially with number of components.

Low temp? I’ve seen numbers of 1000C floating around this site. That is a pretty good temperature for a thermal cycle with modest efficiency (~40%).

errr…. no. That’s way too close to the melting point of beryllium at 1278 °C.

A variety of estimates for cooling systems have them handling temps of ~400 to ~600 some odd °C.

My dream would be for tests to find that the core can run at 700 °C without excessive wear… because that would make spacecraft fusion radiator arrays a lot smaller.

But the temps foreseen are no good for any type of efficient steam turbine.

asymmetric_implosion wrote: I’ve looked at the onion. It will absorb x-rays but how much will turn into useful electrons? That is where the efficiency typically comes in. You can absorb 100% of the sunlight but only about 10% is converted to useful electrons. X-rays may convert more efficiently as they are well above the band gap but you are still limited on efficiency.

Yes, estimates are that we’ll just have to live with about… 80% efficiency. It’s a tough burden to bear but someone has to do it.

asymmetric_implosion wrote: I hope it is greater than 40%. I know heat will be generated by a FoFu power plant so the question is why not use it? Turbines on the 5 MW scale are small and efficient.

Actually, they are inefficient at FF temps and are expensive to boot. The major cost of any current thermal power plant is the turbines and their maintenance.

If FF pans out then it will be cheaper and more efficient to simply add another FF unit than it would be to add and maintain an expensive turbine and all of its auxiliary gear and costs.

asymmetric_implosion wrote: A helium turbine in particular is very compact and efficient.

… and [em]very[/em] expensive.

asymmetric_implosion wrote: It adds more electrons to the grid.

You can get more power quicker and cheaper by adding another FF core.

asymmetric_implosion wrote: Some cooling is going to be required of FoFu-1 so why not put that heat to good use rather than dump it into the air needlessly.

Needlessly? Who would do that? No one here, that’s for sure 🙂

Industry uses vast amounts of heat for a vast number of processes and some processes need cooling as well. Buildings and, indeed, entire communities need heating and cooling.

Locally distributed FF units can provide both heating and cooling (via heat-powered absorption chiller systems.)

Simply substituting FF units for fossil power sources [em]lowers[/em] total industrial and habitation waste heat.

[asymmetric_implosion]

I hope the photovoltaics work as described. Is there test data to support the 80% efficiency or are these theoretical calculations? If they do work why aren’t they deployed on every nuclear power plant? Tons of gamma rays are produced and could be converted to useful electrons.

I hadn’t considered using the heat for buildings and such. The loss seems significant but probably better than a turbine. The Russians have some data on this since they used fission plants to heat towns.

I guess the big question is will a power conversion cycle be needed at all?

[Author]

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