A simple p-B11 fusor proposal - Ashok Gupta

[Ashok Gupta]

In a proposed (thought) experiment for p-B11 fusion, we create plasma consisting of ions of B11 and protons in a suitable potential well of electro (magnetic) field/s. Consider that only one proton out of a million protons oscillating in this potential well (PW) succeeds in one nano sec in a fusion reaction with a B11 nucleus, under a given set of parameters. This is imperative with the reported low values of this fusion reaction X-section.

The remaining protons keep oscillating and colliding with B11 ions inside the above PW for a long time in a quasi-steady state. A few more of these remaining millions of protons may also fuse with some more B11 nuclei in the next one sec. Some protons may leak out of the PW and get neutralized by striking the oppositely charged electrodes, giving their energy as heat or may undergo recombination with electrons, producing hydrogen atoms. In a steady-state situation, when the ‘burned and leaked out ions’ are replenished continuously, the process may continue. When the parameters are optimized, the observed rate of fusion reactions may eventually increase sufficiently to show a positive fusion energy output, net of all the energy inputs (or Q>1). One may start extracting energy (either as heat or directly as electricity, using the three alpha particles per fusion reaction, each with an average energy of ~ 2.7 MeV).

Does the above thought experiment have any fundamental flaw/s?

The above situation is similar to what is observed inside a Penning-type cold cathode discharge vacuum gauge. Let us compare two other common types of high vacuum pressure gauges, viz., B A Gauges and Orbitron-type gauges. A hot filament is used in both types to supply the electrons, to ionize the gas molecules. The ion current produced in all these gauges is a measure of the gas pressure. In the B A gauge, only an electrostatic field is used to accelerate the electrons. In the case of an Orbitron-gauge, the electrons are injected in an orbital direction. The anode is a thin wire at the axis of the gauge. This trick vastly increases the path lengths of the electrons and therefore, the probability of ionizing the gas molecules, even at very low pressures. These steps increase the sensitivity of an Orbitron gauge by a factor of x8,000 times. For the same ion current at a similar gas pressure and the electron current in an Orbitron vacuum gauge is only one micro amp as compared to 8 mA for a B A vacuum gauge (Naik P K, 2019, book on Vacuum, pg 93, pub by CRC Press). This saves a lot of energy in generating and accelerating many more electrons in a B A gauge than in an Orbitron gauge, for doing the same task. This effect is further enhanced by adding a small axial (permanent) magnetic field, as in magnetron-type cold cathode gauges.

Therefore, we need to improve the design parameters of the potential well/s in p-B11 fusion reactors for increasing the fusion probability of the p-B11 reaction. No wonder 13 private fusion energy cos, out of the total 33 existing and currently active fusion start-up cos, are exploring simpler alternative approaches of p-B11, p-Li, D-T etc. reactions with different kinds of triggers, rather than with brute force required in conventional Tokomaks or inertial confinement (source Fusion Industry Association’s ten years report, 2022).
Cheers
Ashok Gupta

[Liam David]

The short answer to your question is that yes, there are some fundamental flaws in your thinking. If it were as you describe, we would have had fusion some 60 years ago. I wish it were so. You've forgotten at least the following important processes: coulomb scattering, bremsstrahlung, space charge, and molecular processes (depending on the pressure).

Coulomb scattering causes velocity space diffusion, thermalization, and loss of confinement.

Bremsstrahlung scales as sqrt(T_e)*Z^2, which, for pB11 is ~2500x higher than that for DT for the same cross-section and plasma density.

Space charge complicates the potential structure and means that you cannot use the vacuum fields of e.g. an Orbitrap to compute particle trajectories.

Molecular processes with any remaining background gas cause velocity space diffusion, thermalization, and loss of confinement.

That is not to mention the engineering challenges. How would one go about extracting the alpha particles before they poison the reaction? There are some ideas related to special magnetic topologies, plasma rotation, and waves. In an actual power reactor, you would need some kind of divertor layer to handle the heat flux, and the physics there gets even more complicated. The bremsstrahlung heat flux to the walls alone is nontrivial... the list goes on.

Fusion is easy. Fusion power is hard.

[Richard Hull]

D-T is the prime experimental fusion fuel in all serious fusion experimental reactions. P + B11 is a distant dream of aneutronic/ 3 Alpha reactions. No one is seriously investigating this and publishing reaction rates. 80% of the D-D and D-T fusion efforts with millions of dollars behind them are not publishing current results and Q totals. This is very telling. Nothing but hype and wheel spinning with no real data for the millions spent in the high end "start-ups".

Finally, what Liam said above is the what has all fusion research locked up and constipated since 1952 when Lyman Spitzer started the whole idea of controlled fusion energy with his crude stellarator.

Fusion is the energy of the future and always will be.

Richard Hull

[Dennis P Brown]

Liam said most of what needs to be addressed towards your thoughts on fusion.

As for your comparison of electron devices to a fusion device you appear have overlooked the primary issue preventing attainment of nuclear fusion in a human made device. Besides the obvious mass difference between electrons and protons (creating issues of heating the ions and maintaining the ion temperature in a magnetic field - so comparisons are not appropriate), you need to understand that fusion requires two identically charged positive nuclei to get so close that the 'Strong Nuclear' force can act upon the nucleons and cause them to 'fuse'. The resulting electrostatic repulsion during such a close approch is enormous. Try calculating it to get a feel for what you are trying to deal with relative to fusion. Then look at ion temperatures required. Finally, look at the required densities for the plasma that meet the Lawson criteria for the various fusion fuels.

This is how one starts to understand the issues facing making a net power reactor.

In a fusor, it is far easier because 'tunneling' allows a 'short cut' to get around the enormous energy required to have two protons approch close enough for the Strong Force to act. The trouble with tunneling via a fusor is it is a purely quantum (probabilistic) effect and extremely rare. No way to enhance it - period.

As for conventual fusion via the Strong Force, the electro-static force (again, what you have overlooked) causes even greater repulsion as one adds more protons. Hence boron fusion is vastly more difficult than DT fusion - do the calculations. So, all those companies and their devices attempting to use boron as a fuel are going to fail and badly.

[Ashok Gupta]

This is in reply to Mr Liam David's comments.

Please refer to the recent paper by Kurilenkov et al:

https://www.hindawi.com/journals/lpb/2023/9563197/

I hope it will answer your observations. This group of researchers has been working on this for a long time & has published many papers in reputed journals. A lot of related references are found in the above papers. I have seen many of those, starting from the famous 1933 paper by Oliphant & Rutherford for pB11 fusion.

regards
Ashok Gupta

[Liam David]

I've heard of this group before but am largely unfamiliar with their work. I'll have to read through their papers when I have some time, but doing a quick skim read, I don't doubt that they've done pB11 fusion. I'm not exactly convinced by their simulations, however. As I said, fusion is easy but fusion power is hard.

[Ashok Gupta]

Thanks a lot for such a prompt revert. This group has been on this track for > 15 years.

So many pvt Cos have committed their own money on pB11 start-ups.

If they don't succeed, only God can save us from the impact of global warming.
Because I am personally not convinced that the classical approaches of tokamaks, Stellarators & ICF with massive infrastructures will reach Q>1. Also, I don't see any other alternative source of green energy on the horizon.

regads,
ashok gupta

[Frank Sanns]

The cross section of B11+P1 is not 1 or 2! The neutron cross section of B10+n is that high but not the fusion cross section.

So the question becomes, why even consider boron as a fuel if the cross section is not as high as the other lighter fusion fuels? If it cannot be done with the easiest to do and at the lowest energies 30 KeV instead to 150 KeV then why work on it? Extracting electricity or to have neutrons or not is not the issue. It is fusion itself that needs to be solved before all else.

[Ashok Gupta]

Dear Frank,
pl ref to "A New Evaluation of the 11B(p,aÞaa Reaction Rates"
M. H. Sikora1,2
• H. R. Weller1,2"
in
J Fusion Energ (2016) 35:538–543
DOI 10.1007/s10894-016-0069-y

This shows X-sec between 100 to 1,400 milli barn for energies below 666 kev. This is not too low. Further, i have suggested that each energetic proton goes in orbits, travelling thousands of times before being captured by the anode. We spend energy only once on each proton to bring it up from thermal energy to 666 keV. Finally, if it survives a fusion reaction with a B11 nucleus, the proton delivers its energy as heat. It may be partly recovered and reused.
Secondly, the reactants, boron and hydrogen, are cheaply & abundantly available. This is why the aneutronic pB11 fusion is particularly attracting so much interest.
Reg. Ashok Gupta

[Richard Hull]

The current fusion effort revolves around D-T fusion which only needs 80kev energy to do fusion where it peaks versus PB11 at 600kev. The poor bastards using D-T at 80kev can't do power ready fusion! If you think you or anyone will do better where 600kev is demanded to get max value via cross section, have at it. Please, no putt-putt boat fusion like NIF and where other pulsed systems want to do business. Terra watt pulses do not deliver fusion at net energy gain as seen in the much heralded supposed energy gain reported by NIF. NIF lied to the public! When all energy in versus energy out is figured, we see NIF did their fusion at a huge net energy loss.

Richard Hull

[Dennis P Brown]

That a fusion fuel is cheap or available is irrelevant to the process if net energy is viable. Fusion is not fission - the energy it can produce makes that issue unimportant relative to fuel sources.

Having your protons circulating in an electric field is not ever going to work at ion densities that would produce any significant energy (the author suggests a magnetic field - which currently, can't even handle ion temps an order of magnitude lower still.) Do the calculation - the number of parasitic collisions would be overwhelming. Robbing the ions of the needed energy before likely proper collisions ever occurred. No, they cannot be harnessed for 'heat'. These are 660 keV ions - not gonna work. As for getting enough ions to the required energies at all is something no laser or power supply system could ever do for a dense enough plasma to return break even levels of power - until this question and the circulation problem are addressed (through there are far more) would be a good start for you to explain if you want people to start to believe that this reaction is remotely possible.

The authors of the article you site point out the concept will not work for real power production but hope a pollywell design would make the process more viable. Well, pollywells don't work for breakeven DT, so the chance of using boron and hydrogen is far more unlikely still. So, not sure why I should discount the authors who acknowledge that the process won't be suitable for net power and their speculation is that somehow (no reason given) a pollywell will solve the issues (which as they and we here know polywell fusion confinement has failed for vastly more likely fusion reactions (DT.))

[Ashok Gupta]

Dear Dr Hull and Dr Dennis,
Thanks for a lot of homework.
I will try some back-of-the-envelope math now.
Regards
Ashok Gupta

[Dennis P Brown]

Remember, boron fusion is possible the issue is doing it here on Earth. So, I am glad you are looking into the details and learning. That is both what this site encourages and enables you to expand your knowledge. Good luck and certainly have fun doing this project.