Charge Transfer Collisions.

[Justin Fozzard]

Here's a paper from 2015 with an interesting conclusion; the detrimental role of charge transfer collisions in fusion plasmas has been overlooked and we should be aiming for far higher plasma temperatures than those in current fusion experiments:

"We prove here the existence of critical ion energy, Ec ~200 KeV, above which ion magnetic confinement is classically stable; and below Ec, ions are de-confined by their neutralization via atomic charge transfer collisions with giant cross-section, 10^9 barns, 100 times greater than that for ionization collisions that counters neutralization.
Below Ec, neutralization sets limit to classical ion confinement time τE < 10-6 s vs. > 1 s required for thermonuclear ignition.
This may explain why past experimental fusion reactors, operating at thermonuclear energies 10 - 30 KeV, did not ignite.
In contrast, at energies above Ec, ionization prevails; stable confinement of 20 s was routinely observed with charged injection near ~1 MeV. To render a reactor viable, e.g. ITER, ion energy must be increased to ≥ 1 MeV"

Maglich 2015 REVIEW OF INDUSTRIAL ISOTOPE PRODUCTION IN FIRST COLLIDING BEAM FUSION BREEDER REACTOR
Transactions of the American Nuclear Society, Vol. 112, San Antonio, Texas, June 7–11, 2015

Maglich 2015 REVIEW OF INDUSTRIAL ISOTOPE PRODUCTION IN FIRST COLLIDING BEAM FUSION BREEDER REACTOR.pdf

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[Richard Hull]

Wow! This seems to shine a new light on fusion and its failure over the years, if this is true. Fusion is being attempted in the frigid 10-30kv range!? 300 million kelvins is impossibly chilly according to this paper.

At the same moment, we see fusion collisional cross sections for D-T become on the downhill slide after 100 kev energy in the idealized uniform plasma. D-D falls off at 1mev. Is D-D the ideal fusion fuel??

This will really get the old gears turning in the head.

All of this depends on the accuracy and tenets in the paper being correct, of course.

Richard Hull

[Jim Kovalchick]

Careful... exploring these ideas could get one lumped in and ridiculed with those who pondered the electric theory of the universe aka plasma cosmology.

I for one believe that Paschen's Law should be pointing us toward managing fusion plasma in productive ways. The imperical nature of the law should be telling us there is more to know here and it's relation to plasma ignition makes it important.

[David Kunkle]

Wouldn't the bremsstrahlung losses be absolutely enormous at 1 MeV, as well as the magnetic field required to contain particles flying around at 1 MeV? Or are neither an issue since the plasma is more and more stable above 200 KeV?

Using deuterium would give "rise to compact aneutronic reactor with direct conversion into RF power." ? He didn't elaborate- am I reading that wrong or how would that happen?

[David Kunkle]

Also, the fact that this was presented to the DOE (and the world) 10 yrs. ago makes me think something is seriously wrong with all this.

Or will it take another 10 yrs. before anyone takes it seriously?

What? Fusion might actually work at 1 MeV? We can't be bothered with that- all our funding and our careers revolve around making 30 KeV reactors work.

[Frank Sanns]

There are a few things that seem to not make sense in that paper. The coulomb barrier is the fusion barrier. Like charges repel with that force. That is the limiting factor for fusion to occur.

In the non-Maxwellian fusor, the fusion cross sections are well described. While this is different than the Lawson criterial for self sustaining fusion, it is still relevant. Heat capacity, density, mass, etc, are important for fusion to sustain. For a fusor, that is not the criteria that is important. Maybe not even for many of the large machines.

It is a battle between rarified plasmas to get to the required energies for fusion and enough fuel in the right place and in the right condition to self propagate fusion. Electrons are small and while they have opposite charges, they are more energy loss mechanisms than anything else. Yes, that is what the paper is stating, that recombination of electrons with atoms or ions sucks more than 100 times the energy out that what goes into producing fusion.

But fusion is WAY tougher than that so even totally removing electrons in outer space and only having deuterium ions to deal with still presents that pesky problem of the Coulomb barrier. That is the barrier to overcome. The electrons are only sponges of the last modicum of energy. Sure it is important for propagation but you have to get there and at high enough densities to keep things going. That is a long way off.

[Rich Gorski]

Interesting paper.

However with the thousands of high level physics people working on fusion all over the world why has no one considered this. I guess they just realize that no Tokamak style reactor will ever reach a Maxwellian T = 200keV, that's billions of degrees. However I can see the point of the paper, 100X greater chance of charged ions remaining in the plasma might help with confinement as opposed to losing so many when they become neutral. But as David indicated Bremsstrahlung increases with electron energy so the power loss due to X-ray emission may overcome any beneficial effects.

Rich G.

Ps. When did the DD reaction become aneutronic??

[Richard Hull]

This got us all thinking, but Jim is correct to not go to far afield with it. Others mentioned this older paper seems to have not changed any direction in the fusion world of big money.

Even startups are sort of big money today. As Jimmy Durante used to say, "Everybody wants ta' get into da' act!"

Richard Hull

[Justin Fozzard]

In reply to David's earlier post, a paper by Menasian from 1988 described methods for direct conversion.
He also noted how phase bunching the ion orbits would improve the conversion: interestingly, Rider suggested a similar method in his 1995 doctoral thesis that should have the mitigating effect of reducing Bremsstrahlung losses.

Menasian 1988 Radio frequency direct conversion of migma power.pdf

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[Joe Gayo]

100kV
1MW
20-200MHz
Transmission Line

These items together are a tall order

[Justin Fozzard]

Not too onerous Joe, how about using techniques similar to those for high power ICRF:
>40kV RF, ~1.5kV/mm, ~1.2kA
20MW
50MHz
>10m transmission line

Nightingale 2008 RF and Mechanical Design of the ITER Ion Cyclotron Resonance Frequency Antenna.pdf

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[Joe Gayo]

Apples and oranges.

That's into a plasma ... done all the time. Show me an example where it's transformed into power that could be connected to a DC or AC grid.

... and ITER isn't an example of economic viability.