magnetic confinement fails due to charge transfer

[jrvz]

Bogdan Maglich presented this paper at Thorium Energy Alliance Conference #6 (TEAC6), in Chicago on May 29, 2014.

Bogdan Maglich - "Th/U233 breeding Ti above 200 KeV viable , NOT at thermonuclear ion energies"
http://www.youtube.com/watch?v=q7_Whm9yQV8

He claims charge transfer between neutral and ionized atoms has been misunderstood for 50 years. It's actually much more likely that a fast ion will be neutralized (and therefore escape confinement) than that a fast neutral atom will be ionized, unless the ion has energy greater than about 200 KeV. He has suggestions for improving tokomaks, but to me it makes a polywell look like a better bet.

Abstract:
We show that the cause of 50 years of failures to achieve, in magnetic fusion systems, ion energy confinement time required for ignition, τE , is charge transfer scattering (CT). CT destroys beams and plasmas by neutralizing ions with giant σCT = 10^9 barn. Ignoring CT existence , ITER designers overcalculated by a factor of million expected τE = 3.8 sec Vs. max possible from classical E&M physics: 10-6 sec (microsecond). CT neutralization dominance over ionization renders ITER a million fold energy sink at thermonuclear energies below ion energy threshold for magnetic confinement, Tmag ~ 200 KeV. In contrast, above Tmag, ionization overwhelms neutralization and τE= 24 s was achieved in colliding beam fusion 750 KeV. To make ITER , 100 KeV D0/To gas injection should be replaced by 1.4 MeV D2+/T+ ; non-focusing magnets with strong-focusing ones; and low vacuum pumps with UHV ones.

Paper by Bogdan Maglich, Dan Scott (deceased) & Tim Hester of CALSEC California Science & Engineering Corp., Irvine, California: http://calsecco.com

Footage captured for "Thorium Remix" an educational video series about thorium. http://ThoriumRemix.com/

Maglich refers to this book chapter:
H.B. Gilbody, w, In: Mitio Inokuti, Editor(s), Advances In Atomic, Molecular, and Optical Physics, Academic Press, 1994, Volume 33, Pages 149-182, ISSN 1049-250X, ISBN 9780120038336, http://dx.doi.org/10.1016/S1049-250X(08)60035-X.
(http://www.sciencedirect.com/science/ar ... 0X0860035X)

[hanelyp]

"He claims charge transfer between neutral and ionized atoms has been misunderstood for 50 years."
A most extraordinary claim.

The problems I keep reading about in most conventional fusion devices are some form of turbulence, not diffusion.

[D Tibbets]

I may be far off, but at least in certain respects, the claims seem strange. What is ment by a million fold sink? Certainly Jet and other Tokamaks have reached well above 0.1 Q.

Charge exchange is a well known loss mechanism. In glow discharge fusors, I have heard that neutrals outnumber ions by ~ 60 fold. With subsequent collisions a hot ion may charge exchange with a cold neutral, resulting is a cold ion and a hot neutral. The neutral can subsequently escape confinement, cooling the plasma. It is an energy drain more than a particle loss. This is certainly common in a glow discharge fusor, and in a Tokamak or other machine if there are subsantial neutrals, near the number of ions or greater than the number of ions. But, what is the ratio in Tokamaks or the Polywell? In the Polywell, the background neutrals start out at ~ 1-10 *10^17/ M^3 (Pressure of ~ 0.01 to 0.1 Microns). Subsequent neutral gas puffing, or plasma injection or ion injection and associated secondary ionizations provides ions, and also increased neutrals in some situations. What these numbers are is debatable, but as an example, the background neutral numbers are limited to ~ 10^19/M^3 due to the limits of arcing. With Wiffleball trapping the ion population may be as much as ~ 10^22/M^3. The ions so far exceed the number of aviable neutrals that charge exchange will be a relatively rare event (I think). Recombination of ions with free electrons, may be a more significant concern, though with reported ionization times of neutrals, they may not escape much before re ionization, at least in a large machine (>1 meter).

I have no idea what the ratio of neutrals to ions is in a Tokamak. I assume it is not much though. If ion confinement is measured in 100s of seconds and neutral confinement is measured in small fractions of a second, the neutrals present or created by recombination would quickly be purged from the system (or be reionized). I suppose in a Tokamk, neutrals may hang around through bouncing off the walls (and losing energy in the process) and become a problem. It depends on the vacuum background level and pumping considerations. In the Polywell there is a hard limit that can be tolerated. In A Tokamak, I suspect the neutral background limit may be similar. The difference is the ion density may be ~ 10^19/M^3 in the Tokamak, and this may be similar to the permissible limit of neutrals (~10^19/M^3- or ~ 1 Micron). From this funtional perspective neutral- ion charge exchange may be a significant energy drain- though again, if so, how are the promising Qs reached? In the Polywell the ion to neutral ratio may be closer to 100 or 1000:1 and so the charge exchange energy loss contribution would be relatively much less. The Polywell conditions reflects the background neutral density that limits the machine due to arcing, and the ion densities that are required for useful fusion levels. This is a requirement for predictions or experiment to reach if the machine works.

Dan Tibbets

[jrvz]

As I understand, his claim is about confinement time rather than Q.

[hanelyp]

In fusion, confinement time and Q are closely related. For a given plasma density and temperature, longer confinement time leads to higher Q, up to the point where the plasma is self heating from fusion products.

[D Tibbets]

In fusion, confinement time and Q are closely related. For a given plasma density and temperature, longer confinement time leads to higher Q, up to the point where the plasma is self heating from fusion products.

Ditto, and just to add complexity, in the Tokamak, the heat lost through radiative processes like bremsstruhlung contributes. In the Polywell additional factors like confluence (central focus), temperature spread, possible dillution effects, and recirculation potential can apply. The Polywell is not self heating for the most part. I'm uncertain if such is needed for FRC.

Dan Tibbets