Magneto-Inertial Fusion

[DeltaV]

So 'velocity' is spread only within a single order of magnitude for fusion, and represents no more than a table-top sized device operating at 1 to 5MHz rotation. Seems like it would be a very useful option, to me, even if it turns out not to be 'the best' or 'most powerful' of several future solutions to fusion.

Just added some Boraxo (sodium borate) to my washing machine, and now there's a strange blue glow emanating from it as it spins...

Seriously, 6 ft diameter at 5MHz rotation gives a tangential speed of 17849 mi/sec (~0.1 c). Not as bad as I thought. The rotating charges constitute a solenoidal current with resulting magnetic field. Forces on a wire solenoid are radially outward (coil bulging) and longitudinally inward (compression along axis, less toward the ends). Would there be a resulting push of ions to the outer wall, beyond that due to centrifugal force or applied E field, and a tendency for ions to move towards the mid-plane (perpendicular to axis), or would plasma dynamics and relativity conspire against this?

Several years ago I was researching Ranque-Hilsch vortex tubes for possible application to heat engines. A high pressure airflow injected tangentially at one end will, in a properly designed vortex tube, result in a (rather inefficient) "Maxwell's demon" separation of flow into a hot vortex along the tube inner wall and a reverse-flowing cold vortex along the axis. I don't have that research handy (it's in storage far from here), but one of the papers I found reported a Russian vortex tube experiment that produced a record-low cold flow and was associated with a blue glow coming from the tube, and possibly a humming sound. Wish I could remember the details...

[chrismb]

Do not worry about any ions at relativistic speeds. They will be going too fast for fusion if they get relativistic. For example, a 40Mrad/s rotation speed (6MHz) corresponds to a magnetic field of only 0.4T for protons, yet were those protons to be held in orbit at a radius of just 0.25m then they would have enough energy to even fuse in the p+15N reaction that I occasionally promote here, let alone p+11B! Getting things orbiting in bench-sized kit at unit MHz is fast enough for fusion.

I tend to look at it this way; back in the 1920's and 1930's there was a rush to get huge particle energies, essentially as a result of Rutherford's 'call' to scientists to push into MeV range for analysis of the atom. The thing is, no-one really knew of, or barely contemplated, fusion power. As a result, the line of thinking on particle accelerators at the time meant that they had no reason to consider more efficient, but lower particle energy, devices. The 'historic chance' to do that was essentially missed because no-one knew abotu fusion. Forward-wind 40 to 50 years and thermonuclear fusion looked really viable. Forward-wind a further 40 years and those particle accelerators of the 1930's seem like they are antiquity and consequently have not been given a second look to see what a 1930's particle accelerator scientist might've come up with had they been seeking fusion.

I've put myself in that thinking position, and come up with a potential option. I suspect there may be a few such options...

[rcain]

... are you suggesting some type of relativistic cyclotron fusion device? (noting coulomb force and Lorenz apply very differently at relativistic speeds - eg. http://arxiv.org/ftp/cond-mat/papers/0501/0501541.pdf).

[kcdodd]

On the original topic, there are some plans at the z-machine to apply magnetic fields to enhance confinement time in a gas target, plus laser preheating to reach fusion breakeven when they use z-pinch to drive the whole thing together. It's quite interesting, and no major changes are needed to the facility. If it works they'd hit Q>1 in a few years.

On the note of centrifugal fusion, it is very difficult to stabilize the plasma because of interchange. It's like trying to support a heavier fluid on top of a lighter one. The higher you make the centrifugal effect the more this instability works to tear the plasma apart.

[rcain]

KCDodd: i like the sound of that, pity it isnt Q>1 within the next few days however (one day, perhaps...). i mean - pragmatic 'staged' approach to cracking the problem. do you have a link?

re. interchange and other iinstabilities - so we end up with a lumpy plasma in plane rings/disks - is that a problem? replacing one problem with another perhaps. at least its now going very fast (in some general direction). what next?

[alexjrgreen]

to see what a 1930's particle accelerator scientist might've come up with had they been seeking fusion.

I've put myself in that thinking position, and come up with a potential option. I suspect there may be a few such options...

The steampunk fraternity are going to love you...

[chrismb]

The steampunk fraternity are going to love you...

The prototype is made out of bakelite and glass and the metal bits look like the insides of a tetrode. It even looks 1930's.

Good Luck!

... your skills might be in demand either way.

Thanks. Appreciated. On the skills - not sure I have many, I'm more of a bodger with an idea. *I* am the risk in my experiment!

...sorry, I realise this thread was meant to have been about something else... I'll update on this in due course in its own thread.

[kcdodd]

No link sorry. A guy gave a talk here.

Mark Herrmann, Sandia National Laboratory, "Magnetized
Liner Inertial Fusion on the Z facility,"

You might do a search on it.

[alexjrgreen]

Was this it? Science with High-Power Lasers and Pulsed Power Workshop

[kcdodd]

hmm, no it was in late September. but it's the same project, at SNL. He talked a lot about the problem of rayleigh taylor instability of the solid liner. Interestingly, simulations seemed to show that an applied magnetic field can also help stabilize these, at least on the inside of the target. Basically it adds vertical structure internally, perpendicular to the azimuthal external field (countering the "sausage" effect). Their current research is to see if they can successfully z-pinch such a solid, thin-walled target to the required ratio for ignition.

[Stoney3K]

Do not worry about any ions at relativistic speeds. They will be going too fast for fusion if they get relativistic. For example, a 40Mrad/s rotation speed (6MHz) corresponds to a magnetic field of only 0.4T for protons, yet were those protons to be held in orbit at a radius of just 0.25m then they would have enough energy to even fuse in the p+15N reaction that I occasionally promote here, let alone p+11B! Getting things orbiting in bench-sized kit at unit MHz is fast enough for fusion.

I tend to look at it this way; back in the 1920's and 1930's there was a rush to get huge particle energies, essentially as a result of Rutherford's 'call' to scientists to push into MeV range for analysis of the atom. The thing is, no-one really knew of, or barely contemplated, fusion power. As a result, the line of thinking on particle accelerators at the time meant that they had no reason to consider more efficient, but lower particle energy, devices. The 'historic chance' to do that was essentially missed because no-one knew abotu fusion. Forward-wind 40 to 50 years and thermonuclear fusion looked really viable. Forward-wind a further 40 years and those particle accelerators of the 1930's seem like they are antiquity and consequently have not been given a second look to see what a 1930's particle accelerator scientist might've come up with had they been seeking fusion.

I've put myself in that thinking position, and come up with a potential option. I suspect there may be a few such options...

I actually postulated that idea in this thread. We've got quite a few multi-million-dollar cyclotrons and synchrotrons doing basically nothing except some local university research projects, and any decent sized synchrotron should be able to generate energies high enough for fusion. Might not be benchtop-sized, but almost. (The LHC is, obviously, too big.)

[chrismb]

and any decent sized synchrotron should be able to generate energies high enough for fusion. Might not be benchtop-sized, but almost. (The LHC is, obviously, too big.)

[I'll say it just once more!] ] Any tiny cyclotron should be able to generate energies high enough for fusion. A synchrotron would put too much energy onto an ion.

Remember - 10Mm/s is the fastest velocities you will need for fusion, and cycltrons are often tuned to run around the industrial 13MHz frequencies - viz the total orbit needs be only <1m (<15cm radius). Any faster or bigger and you'll be knocking off nuclear chunks and no longer fusing.

[Tom Ligon]

How tiny a cyclotron, Chris? I have a couple of papers (DARPA funded, of course), by a friend who was interested in biological transmutation as an energy source. There are four elements that a few people over the years (either nitwits or visionaries, I'm not absolutely certain which) say can pick up a proton in some biological systems, becoming a new element. p-Sodium was one such reaction. I'm sure all arguements against p-B11 apply to these heavier nuclei as well.

Sol looked at the structure of an ATP molecule and decided it looked like a cyclotron and could potentially operate as one.

Good for science fiction. I'm not counting on it powering my car anytime soon.

[rcain]

... so, i'm assuming the reason it (tiny cyclotron fusor) hasn't aready been done, is because of efficiency constraints, no, or Brem, or...? or why not?

[alexjrgreen]

Try fashion...