Fundamental limitations on plasma fusion systems not in thermodynamic equilibrium

[hellblazer]

I finally found an electronic source for this thesis - directly applicable to IEC fusors... The link below will direct you to GIFS of the entire thesis - you can order the PDF at the same site. Nice to see some sanity in this area.

http://theses.mit.edu/Dienst/UI/2.0/Com ... ections=13

[3l]

Thanks Hal:

I had bits and pieces of his work but not the full text.
The recirculating electron losses were highly evident when I started in this work. In pulsed fusor a plasma is created in a small shell area. When the negative pulse is created the electron path is straight to the shell reducing the energy losses thru them. Electron emitters on the central grid provide lower entropy ( read energy of the ion > than electrons) electrons to balance the charge inside the sphere. Non linear effects are not ruled out due to the fact the tensors he defined the entropic path are finite...
fast rise time phenomim might override his concerns.
A three grid pulsed system rids high velocity electrons while maintaining the maxwellian character of the ions.
We are yet to see a De-HE3 reach equillibrium as he has predicted. Stay tuned.
New***
I'm down to page 180 now.
The area I tend to be interested in are pages 143-180

Larry Leins
Fusion Tech

[hellblazer]

Interesting. I'm still learning about all this, and it was a very fun read of this thesis. What I found interesting is that he wasn't really ruling out D-D fusion being efficient, just that the neutron production was high and therefore undesirable. I think for the big, heavy and expensive Tokamak system, this becomes a real problem as eventually you'll have to scrap the machine. However for IEC, you only have the grids and some other minor components to scrap - not tons and tons of material.

So I'm still wondering about this thesis and what it really means...

[3l]

In 1995 all the rage was aneutronic....migma cell and all that jazz...I got the feeling the author was prejudiced against a neutron generating process. He tended to lean towards the D - He3 and p-B11 systems. He has good points about power and Bresstrum losses but I felt he depended too much on the Hartree - Fock a little too much. His
mathematical methods have NOT been varified by experiment. But reading the whole text has told me why the MIT boys weren't all over Maxwellian IEC fusion devices. This paper if read by a graduate student would result in no action in this area.
This paper probably killed off IEC work at the academic level which would explain the chilly reception I got at the Ole Miss physics facility.
I tend to disagree with his analysis of power recovery
in straight foward fusors.....the guy had never heard of the inverse Compton Effect that could turn xrays back into electricity with fewer losses than the author claimed. His methods allways involved boiling water to reclaim energy (always lossy).
I'm still reading this paper.
Seems like we got a green light.

Fusion is fun!
Larry Leins
Fusion Tech

[Richard Hester]

As for D-D fusion in Tokamaks, the present state of the art would only allow use of the D-T reaction to produce significant amounts of power. The neutrons off that reaction are over four times the enegy of the D-D neutrons, and wreak both mechanical and radiological havoc. Imagine a hail of tiny sledge hammers busy displacing (and transmuting) the reactor structural elements, atom by atom... It's enough to give a mechanical engineer screaming nightmares.

[3l]

Hi Richard:

I know what you mean about neutron activation.
But a small reactor using the neutron for power would be orders of magnitude less than the billion watt Tokamak Reactor Parks proposed in the mid seventies.
I think small scale is beautiful on the fusion scene.
New***
I'm now at page 196
Humm this cat only looked at 3GW only!
His more valid points are the loss mechanisms
and his few remedies with include the " nuclear wine cellar " approach to eliminating tritium from D-HE3 reactor by lithium wall shields. Simply pop it into storage for about 6 years pretty pure He3.

Larry Leins
Fusion Tech

[hellblazer]

Can you give me some pointers to processes which are more efficient than simple heat processes at converting x-rays to electricity?

[3l]

By stacking two materials of two different density you can put a circuit between them and generate power.
The higher density more secondary electrons...flows to an area where the electron numbers are less.
The photo electric effect also can be used to great effect.

Larry Leins
Fusion Tech

[hellblazer]

Any links? Sounds plausible. I'm asking for links, as some of my professional physicist friends are very skeptical about this...

[DaveC]

The issue of neutron activation of any and all hardware between the fusion region and the neutron absorbers, is not a trivial problem. In the present IEC fusor, not only would the grids be affected, wire insulation, gaskets, the shell, flanges, insulators, etc , etc would be involved. Eventually, you wili have a disposal problem. And this method probably will not reduce radiation contamination.

So it may well be, that whatever the efficiency could get to, the D-D system will not be practical.

Dave

[3l]

Hi Guys:
I did not mean to imply that activation is a trivial issue but rather reply to the views represented in Mr Ritter's paper.
On Dirrect conversion of Xrays I refer you to the the Dirrect Converion of Nuclear Energy and Nuclear Flight books. All the work was done along time before ARPA and the Internet even existed. Hence no links. ( the work started in 1957) It covers
the Alphatron , radioheated thermocouples, plasma coupled thermoelectric devices, thermoionic and photonic conversion techniques. In years gone by the railroads used switch lights that used a gamma activated flourescent element to produce visible signals for nearly two miles away. Another used a solar cell to produce electricity from light created in a stimulated phosphor by nuclear emmisions and beta rays.
A lot of this work went on in the sixties as part of the nuclear flight program in 1961. A huge number of offshoots of this program are on station running day in day out providing small but long term (10 years usually) power. RTG's and Active Shielding techniques for Spacecraft.
When the space exploration finally gets to the settlement stage the dust will be blown off these early sixties chessnuts and implimented. I'm not too surprised to hear of modern day physics people never heard of such a thing but down on the farm at DOD they were everyday stuff.

Fusion is Fun!
Larry Leins
Fusion Tech

[Richard Hull]

Even with a super amateur fusor powered to 200kev and doing 10e7 or even 10e8 neuts/second, the neutron activation would be basically zero. There are just no high cross section materials in the fusor to neutron activate with the very high energy neuts. For all intents and purposes, the fusor is as transparent to the neuts it makes as a film of cellophane. This is with D-D fusion, of course.

Richard Hull

[3l]

Thank you Richard (Hull) for pointing up the obvious...
that for activation to occur the neutrons must be moderated. All of Mr Ritter's work assumes that the inner vacuum wall would be hot due to fast neutrons .
The bulk of the activity would be in the breeding/moderating blanket area instead.

Fusion is fun!
Larry Leins
Fusion Tech

[smad]

I grabbed the whole thesis on the MIT site and made a PDF too big for this forum (45Megs -> 16Megs zipped)
People interested to the file just have to contact me
Wise people (on Linux), inspire yourself from those 2 scripts...

Hugues Langlois
A Starter Fusorist Engineer

Note: GIFs have no extension and are located in "theses.mit.edu/Dienst/Repository/2.0/Page/0018.mit.theses/1995-130/inline/"
Note2: theses.mit.edu site sometimes crash, so resume your daownload from where it fails