Fusors LIVE AGAIN!

[Zixinus]

A new idea to solve a mayor problem of IEC fusion is found a possible solution.

IEC fusion, for those who don't know and can't be bothered to research, is the use of electrons to confine highly-energetic ions and thus induce fusion.

The most commonly used device, called "fusors", have been commonly used as a neutron source, and have won science fair projects.

A video of such a device working:

http://www.youtube.com/watch?v=eeMd5LCu7Ag

To note: Hirch-Farnsworth devices can operate for minutes, are small and relatively cheap to do. They do not, however, produce breakeven.

One of the main reasons for this, is that the ions collide with the grid, another is that non-fusion collisions cause radiation which also melts the grid.

The proposed solution is called "Periodically Oscillating Plasma Sphere (POPS)".

Science paper regarding it here, on Physical Review Letters:
http://scitation.aip.org/getabs/servlet ... s&gifs=yes
(you have to buy it)

Abstract reads:

The periodically oscillating plasma sphere (POPS) [D. C. Barnes and R. A. Nebel, Phys. Plasmas 5, 2498 (1998).] oscillation has been observed in a gridded inertial electrostatic confinement device. In these experiments, ions in the virtual cathode exhibit resonant behavior when driven at the POPS frequency. Excellent agreement between the observed POPS resonance frequency and theoretical predictions has been observed for a wide range of potential well depths and for three different ion species. The results provide the first experimental validation of the POPS concept proposed by Barnes and Nebel [R. A. Nebel and D. C. Barnes, Fusion Technol. 34, 28 (1998).].

Another paper in "Physics of Plasmas":
http://scitation.aip.org/getabs/servlet ... s&gifs=yes

The problem of large-amplitude spherical oscillations of an ion cloud in an Inertial Electrostatic Confinement (IEC) device is examined. It is shown that ion fluctuations of a Gaussian profile in a spherical, harmonic well are stable to all hydrodynamic modes, and stable oscillations about the oscillating equilibrium state may be damped by continuum damping. It is also shown that the ion state forms a thermal equilibrium, in spite of the orders of magnitude, density, and temperature changes during the oscillation cycle. Finally, a brief discussion of how to experimentally realize the required electron distributions for these oscillations is presented.

Another paper in "Physics of Plasmas":
http://scitation.aip.org/getabs/servlet ... s&gifs=yes

A major issue for electron injected inertial electrostatic confinement (IEC) devices is space charge neutralization. A new formalism is developed that will allow this neutralization to occur for both oscillating and steady-state IEC plasmas. Results indicate that there are limits on the amount of compression that can be achieved by oscillating plasmas while simultaneously maintaining space charge neutralization and parabolic background potential. For steady-state plasmas, there are no such limits and space charge neutralization can be achieved even when the plasma becomes quasineutral.

This removes a mayor hurdle in the progress of IEC fusion. With such a mayor inprovment, D-T breakeven is almost certain, D-D is highly possible and advanced fuels too, could be done.

Schematic of such a device:



There was the other problem mentioned, the one with ions colliding with the grid. This too, can be solved by a formation of a "virtual grid", made entirely of electrons (the negative grid that is, the positive grid is still solid) and can be reformed within normal process.

One such scheme is Dr.Bussard's "Polywell" concept. Currently, there is very little material avalaible due to the Doctor's health problems and the amount of work involved (over a decade). Also, there has been an embargo on previous progress, due to the nature of the funding. You may still get some theory papers regarding losses and such over at DTIC (=http://www.dtic.mil/) with the keyword "Polywell". There is also a forum with the very aim to discuss, publicize and analyse Polywell, here: http://www.talk-polywell.org/bb/index.php

The material, which is not very technical but available can be found at the Doc's lame-ass homepage (what? It IS lame, and was done on quick notice, and the Doc has so far not answered any invitations to spice it up):
http://www.emc2fusion.org/

There is no reason why the two concepts cannot be combined.

Curiously, the experiments proposed are much more cheaper then the giant, magnetic doughnut that are currently funded internationally and have a time line of over half a century and a history just as old.

[Starglider]

Curiously, the experiments proposed are much more cheaper then the giant, magnetic doughnut that are currently funded internationally and have a time line of over half a century and a history just as old.

I don't see why this is 'curious'. Electrostatic confinement was the early big hope, but it quickly became obvious that the obvious techniques didn't scale and would never be power generators. Magnetic confinement did scale and indeed has been slowly scaled up, at a rate limited by funding and the fact that burning plasmas are complicated and there were a lot of surprises that had to be understood and allowed for along the way. Inertial confinement has not shown the same degree of smooth progress, but the US throws lots of money at it anyway for other reasons.

The newer electrostatic confinement schemes (which rely on clever tricks rather than 'brute force') are certainly worth serious investigation and it's a shame that they aren't better funded. But they are far from proven and even if they do work there are probability some surprises ahead in scaling them as there were with magnetic confinement (though fortunately some of the plasma physics research is transferable). Furthermore many of the same challenges apply (e.g. finding materials that can stand up to the neutron flux) in creating power stations based on them. So while this work is promising, even if electrostatic confinement can be made to work it isn't likely to form the basis of the first generation of fusion stations. That said the relatively low mass and volume and potentially much lower minimum practical power output would make it great for mobile applications. Unfortunately elements of the 'free energy' and 'anti-big-science' fringe have attached themselves to this subfield (probably because fusors are within the reach of moderately funded non-experts) and given it something of a crankish reputation.

[Zixinus]

I don't see why this is 'curious'.

When people think of fusion, those that know what it is at least, think of tokamaks. Which are big and very expensive. ITER will cost, what? 30 billion dollars worth? I find it curious that IEC devices need millions and not billions.

Electrostatic confinement was the early big hope, but it quickly became obvious that the obvious techniques didn't scale and would never be power generators.

I hold the same (mostly emotional, I admit) view regarding magnetic confinement. As for scaling, there is a joke among the fusor crowd:

Of course there is virtue in scaling. If you have one stellar mass worth of fuel, you can get a practical fusion device.

Furthermore, the reasons why IEC won't scale are the problems mentioned. The problems POPS system and other ideas aim to solve.

But they are far from proven and even if they do work there are probability some surprises ahead in scaling them as there were with magnetic confinement (though fortunately some of the plasma physics research is transferable).

I've linked a paper about IEC in "Physical Review Letters" which has data on experiments done with POPS system.

They are just as proven as magconf is.

Also, IEC devices don't have ignition (when there is enough fusion to go around that the plasma does not need to be heated externally). Which, from what I understanding, only exists on paper.

So while this work is promising, even if electrostatic confinement can be made to work it isn't likely to form the basis of the first generation of fusion stations.

Considering that ITER, the most serious magconf project, will require 20 years to be even built, I won't hold out my breath for that. Some IEC research timelines can would build a prototype plant by the time ITER is built, counting a few years extra time.

Unfortunately elements of the 'free energy' and 'anti-big-science' fringe have attached themselves to this subfield (probably because fusors are within the reach of moderately funded non-experts) and given it something of a crankish reputation.

Would it be unknown to the history of science that a new discovery or a new concept or possibility didn't attract crackish claims around itself?

[Zixinus]

Oh and I forgot to mention: Polywell does scale well. The bigger you build it, the more power it will produce, and it will reach the point where it will do breakeven, bigger and it will do much more then that. Maximum size gives something like 1-3 gigawatt continuous output. This not counting POPS system.