Muon catalyzed fusion and dreams

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Pierre_Thourault
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Muon catalyzed fusion and dreams

Post by Pierre_Thourault » Sun Jul 19, 2020 10:57 am

Hello everyone

I just watched a video about muons catalyzed fusion and I wonder what are your opinion about it ? As far as I’m concerned, it looks a very pretty approach to fusion because we don’t use brute force and just the fact to use an elementary particle with a lifetime of around 2,2 us for fusion is incredible. With the simpler fusion reaction ( deuterium and tritium) we are at around 50% of breakeven which isn’t that bad because with the most advanced tokamak ( JET ) we are at around 68% of breakeven.

If this approach is viable scientifically it would be much better than tokamaks because the most complex part I think is the particles accelerator which is relatively simple in comparison to tokamak so it would be cheaper.

I know lot of you are skeptical for commercial fusion but if you have to bet for an approach what would you choose ?
( you win the bet even if it’s « only » scientific breakeven )

I would bet Tokamak for breakeven because lots of people are working on it ( ITER, China, Commonwealth fusion from MIT, Tokamak Energy in UK )

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Dennis P Brown
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Re: Muon catalyzed fusion and dreams

Post by Dennis P Brown » Sun Jul 19, 2020 11:17 am

Sorry to say but the energy required to create muons is millions of times higher than what any tokamak requires to do fusion. Its a pity (and a disservice) that these people that write these articles on muon fusion do not bother to note this critical fact. So no, it is impossible to do muon based fusion and get any net energy back.

As for what current research design has the best future chance to do net energy fusion I'd bet my money on the German Stellarator design - currently the Wendelstein 7-x (a test bed - will not do fusion); the stellarator design is far superior to the tokamak in so many aspects that it has the best chance to achieve net energy someday. Its the cost of the extremely complex magnetic super conducting coils that is the only real drawback of this approch.

Tokamaks have major design issues and the worse is that the plasma tends to burn through the containment vessel and could easily destroy the super conducting magnet leading to destruction of the entire tokamak - talk about ugly. No one has as yet figured out how to prevent this disastrous problem. Considering the vast energy stored in any given magnet, this isn't viable. ITER is hoping that a miracle will occur and they'll solve this critical issue before comming online. Let us hope. There are other issues with that design but this is the current show stopper.

Interial fusion (laser) is still a possible dark hosre and might be cheaper than a stellarator but there is no national will to pursue this design after the disaster that NIF created by using the wrong laser (infrared!) and incorrect pellet configuration (indirect drive instead of direct drive) and utterly failing in their approch just as anyone with knowledge in the field knew they would. Congress justifably no longer trusts this approch thanks to those people at Livermore.

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Re: Muon catalyzed fusion and dreams

Post by Pierre_Thourault » Sun Jul 19, 2020 12:10 pm

The problems with the muons production is all the others particles that are being produced too so we lost energy here. But a pion which decay into a muon cost only 140 MeV so we need 7 fusion reactions with this muon to breakeven. Currently we can do an average of 150 fusion reactions / muon. It’s like we are touching the dream with the edge of our fingers but cannot grap it : if we could just improve the production process ...

I hope you are right for the stellerator but those magnets looks so complex, the cost must be prohibitive !

And for the inertial confinement I think they may achieve breakeven ( I’ve heard they were close ) but for now It would be impossible to commercialize this approach because of the laser that are required. They can’t fire lots of time per day and for fusion they would need many fire per second.

The tokamak stuff seems « too big to fail » so I hope you are wrong and somehow engineers will manage to handle the disruption of the plasma.

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Re: Muon catalyzed fusion and dreams

Post by Dennis P Brown » Sun Jul 19, 2020 1:22 pm

Sorry but the total energy to create muons isn't as low as you cite; one has to generate the initial energy at a power plant (over a 60% loss just there), transmitt to the accelerator site (about 5% more loss). Then they have to convert into usable energy in said accelerator (maybe, at best, 25% efficient.) Then and only then does one use the amount of energy to create a single muon and that is the number you cite (and as you did note, even that production rate is not too efficient but I have no numbers for that.) As for any overall production efficiency of one muon needs just 7 fusion events to create, I have serious doubts its that high in practice and ramping it up for real fusion likely entails massive losses. Muon fusion has essentially zero chance to produce net energy.

As for NIF, they are five orders of magnitude below breakeven. They created a new definition and claim they are within a factor of just five or roughly at breakeven. Sorry but I read the actual work and it is five orders of magnitude below breakeven. Like their initial proposal, they create false facts to support their dead end program.

As for "hope (I) am wrong" - scientific fact is not really about hoping someone is wrong. Please try to understand science - it is not based on hope that proven results are incorrect (like some of my spelling when I am careless - lol.) Now I, for my part, do hope they find a way to fix that extremely serious issue but to date, no one has the slightest idea how too. So yes, they are trying to be too big to fail. So if they then fail after building it and unable to fix the many issues tokamaks have (besides the one I stated), more money (like NIF did) can then be poured into a useless and dead end idea.

As for a real fusion laser - that device exists (a KrF laser), can fire five times a second for three months straight (proven); has an input to energy delivered on target of 12% and, of course, is in the correct wavelength (deep UV). In direct drive mode models show ignition and energy well above breakeven- note I said models; the real world is likely very different. Yet this system is ignored thanks to NIF's complete failure. This laser does not in any way mean direct drive fusion is able to succeed but that is a system that deserves real support. But that train left the station thanks to NIF and a few others.

Aside: engineer's don't fix tokamk problems - physicist do. Besides engineer's have no training to do that type of work, and this fact partly explains why fusion is the energy of the future, and always will be. As Richard has in his posts. ;)

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Re: Muon catalyzed fusion and dreams

Post by Pierre_Thourault » Sun Jul 19, 2020 3:54 pm

I disagree with you, we must count energy loss when electricity goes into the reactor ( so at your 25 % percent loss from the accelerator) because if it works it will generate its own energy.

For the « I hope you are wrong » I mean I know you are right about the problem of tokamak but I hope physicists will find a solution. I meant the same thing as you said.

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Re: Muon catalyzed fusion and dreams

Post by Dennis P Brown » Tue Jul 21, 2020 10:27 am

In my post I said the conversion of energy into particles for an accelerator was 25% efficient - so the accelerator wastes 75% of the incomming energy (you mis-read that). Hence the total energy loss from power plant to particles is: 0.62 x 0.95 x 0.25 = 0.147 or for every 1 mega-watt needed for the particles one must provide about 1MW/0.15 = 6.7 MW of energy at the power plant. Now, what is the best muon production value that can be achieved using state of the art and a truely massive facility?

The Omega facility claims it can achieve a proton energy of 800 MeV and a current of 0.0007 amp in order to create just 10^9 muons/sec (its max output. Do note, such a facility could never handle this 24/7 but that is not the point here so I'll ignore this fact. Also, these muons are very energetic so they'd need to be cooled first resulting in a significant loss; but that is an unknown so I'll ignore that. In the real world that would seriously lower the number of muons available for fusion.)

So using these numbers it would take 1.6*10^3 KWh to produce this beam. Then one would need from the power plant about 1.1 * 10^4 KWh of power to create this beam for one second at the muon facility. These muons, at best rate (a number that is wildly optimistic of 150 fusion events per muon), will then produce 0.17 watt-sec or 4.7 * 10 ^-8 kwh from thermo-nuclear fusion from that beam.

So one needs to generate over 10,000 KWh to get back out just about 0.00000005 KWh. That isn't a good energy trade and certainly isn't anywhere close to net power. (Aside: I think a fusor might be a better generator - well, maybe not but not too different. No need to do that calculation)

The issue you need to really understand is that both scientist and people that make money from power plants aren't stupid (I know, alot of people in high office in the U.S. think scientist are mis-informed - let me correct that mis-conception. They aren't.) If such a simple and easy method did exist to produce energy it would be exploited.

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Re: Muon catalyzed fusion and dreams

Post by Pierre_Thourault » Sat Jul 25, 2020 10:28 am

Yes you are right but I wonder where the optimist numbers I’ve seen about muon catalysed fusion come from. They said that we are at around 5GeV per muon and we currently get back 2,7 GeV per muon.

But anyway thank you for putting my attention on the stellerator I know it existed but I’ve always thought Tokamaks were better which was not that wrong until supercomputer allowed physicists to design the complex magnet desired. But still why is there so many private companies trying to develop a tokamak instead of a stellerator ?

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Re: Muon catalyzed fusion and dreams

Post by Dennis P Brown » Sat Jul 25, 2020 11:17 am

I used the 150 events per muon (I think it is optimistic because it is most likely a theoretical calculation from a very limited experiment - highly unlikely anyone ever really measured that experimentally.)

You should go through the math procedures on the net energy for that process yourself and try to learn that method. It will aid you in the future getting use to converting units and checking claims. However, posting a question when you didn't bother to divide two values to answer your own question isn't ideal here - 2.7 GeV/17 MeV = 158 (events required by deuterium fusion to create 2.7 GeV of energy.) Next, look at the number of muons, and the number of fusion events for breakeven fusion in a typical tokamak.

To do the calculation of net energy vs. energy used to create the Muons you will need scientific notation. If you are not familar with scientific notation here is a link to learn: https://www.khanacademy.org/math/pre-al ... c-notation

As for why people spend billions on tokamaks - I do not think I want to endlessly answer questions on a string of topics that have nothing to do with fusors - through I did partly answer your question on tokamaks, indirectly - see miracle happens ;) By the way, read about the current Princeton Tokamak and why that new unit failed and that they are currently rebuilding it (something of the order of a few hundred million dollars thrown away.)

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Re: Muon catalyzed fusion and dreams

Post by Pierre_Thourault » Mon Jul 27, 2020 9:18 am

Thank you Dennis for your answers

I mean where the 5GeV comes from ( I’ve done some calculations with the most efficient muons facilities and I’ve done a mistake but I can’t find it )

But may I ask you just one more (dumb) question ?

How the particles in a stellerator or a tokamak fusion ? Because they are all going in (approximately) the same way so their energy compared to each other would be less than what is necessary for fusion. It perhaps have something to do with the path they follow around the line of the magnetic field ...

Ps : sorry for this thread a bit useless, I will find my mistake to put the real numbers on the problem (with the link ) at least people who ask themselves why muon catalyzed fusion isn’t use will find an answer here.

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Re: Muon catalyzed fusion and dreams

Post by Pierre_Thourault » Mon Jul 27, 2020 10:17 am

https://journals.aps.org/prab/abstract/ ... .20.030101

This is the link I used to make the following calculations :

It produces around 4.2*10^8 muons per second so the production of the negative muons is around 5*10^7 per second.

The power of the beam is 400W but with the efficiency (I guess) of 25% the power of electricity needed is 1.6KW so the energy used during 1h is 1.6KWh and the production of negative muon is now : 5*10^7 * 3600 which is equal to 1.8*10^11 per hour

So an average negative muon cost is : 1.6 / 1.8*10^11 = 8.9*10^-12 KWh/negative muon
And since 1eV is around 4.45*10^-26 KWh, the cost of a negative muon is approximately 2*10^14 eV

(Now this is where the numbers don’t add up because it is very far from the 5GeV /muon promised and I’ve used what is claimed to be the most efficient muons production device)

A muon can catalyzed a maximum of 150 fusion reactions with D + T so the energy produced per muon is : 150 * 17.6*10^6 which gives 2.64*10^9 eV

The next big problem is the number of muons required to produce for example 1MWh in 1h which is way beyond any existing technologies.

There is still a tiny hope with the migma accelerator which was originally designed to beam to beam fusion and may now be used for the production of muons :

https://www.sciencedirect.com/science/a ... 0288911473

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