Talk-Polywell.org

Just a random thought/question here: It occurred to me that you ought to be able to improve inertial confinement times by zapping your pellet with wiffleball-like magnetic fields just as inertial heating begins. This obviously has nothing to do with IEC, but the use of quasi-spherical B-fields was what got me curious. Has anybody studied this? Anybody got any pointers to docs?

I suspect that getting the temperature up high enough to do the following will be well-nigh to impossible, but I'd be interested to hear if somebody could do a rough estimate on just how far off we'd be:

1) Use a crystalline B-11 target pellet.

2) Pop it into the center of a grid electrode. The grid can be relatively distant from the target to avoid frying it, but you'll waste some kinetic energy if you do this.

3) Pulse proton beams through the grid so that they arrive at the pellet with enough energy to get average energy into the p-B11 cross-section sweet spot.

4) Just as the protons arrive, you zap the target with a wiffle field to enhance containment.

5) As the target turns to plasma, the wiffle field contains it for a bit longer than it would be in pure inertial confinement, allowing it to heat up more.

I would guess that the wiffle field would reduce how symmetrically you had to hit the target, which has always been awkward (and expensive) in most IC schemes. I would also guess that you'd be able to get substantially more energy into the target using particle beams than you would photons, especially when the particle beams are made from one of the reactants.

The whole thing could probably be made to work with D-T or D-D, as well.

Is this completely stupid?

No, it's not stupid. Do a web search on "proton beam inertial confinement fusion". You will get several 1000 papers on the subject. It's just not likely to be cost effective.

drmike wrote:No, it's not stupid. Do a web search on "proton beam inertial confinement fusion". You will get several 1000 papers on the subject. It's just not likely to be cost effective.

Anybody doing anything with "spherical" B-fields to enhance confinement?

Anybody doing anything with "spherical" B-fields to enhance confinement?

Google Polywell.

Magnetized Target Fusion MTF is said to be a combination of inertial and magnetic fusion.
http://wsx.lanl.gov/mtf.html

Torulf2 wrote:Magnetized Target Fusion MTF is said to be a combination of inertial and magnetic fusion.
http://wsx.lanl.gov/mtf.html

Thanks for the pointer. This is similar to what I was thinking about, but not exactly the same. First, MTF looks like it's an FRC scheme, rather than a spherical confinement. Second, MTF is getting its adiabatic heating mostly from magnetically propelling a metal liner into the plasma, where I was thinking that you'd still get most of the heating from hydrodynamic shock of the particle beam collision, but you'd slap the (quasi-spherical) B-field around the whole thing just as the particle beam hit the target to contain the explosion, thereby:

a) Enhancing the hydrodynamic shock in the center of the plasma,

b) Relaxing the stringent beam-symmetry requirements that are needed for vanilla-flavored, NIF- or HIPER-style inertial confinement, and

c) Increasing the burn time for the plasma.


Note also that the mechanical layout of this scheme is very similar to a polywell, with the following differences:

1) Much higher B-field strength in the wiffle-field (this is a big difference--I can't imagine you can do this without superconducting magnets).

2) You've got a grid to generate the potential difference and focus the proton beams instead of confined electrons.

3) You obviously have to drop the target pellets into the machine for each pulse.

The other thing that might render this impractical is the formation time for the B-field. You want to have the field applied after the proton beams have arrived at the target but before they've caused much plasma to form. I suspect that that's a timing window of a very small number of nanoseconds.

You have powerful magnetic compression in the field reversed pinch FRP.
But it’s in toroidal configuration and has no pellets.

I'm not certain how close these approches are to what you ask about, but the National Ignition Facility should be coming online next year. They hope to achive ignition and net power by explosively compressing (imploding) a pellet with lasers. And, Sandia Labs have compressed pellets with a 'Z- pinch' type collapsing magnetic field. They used to have a breif description of a power producing reacter on there site. I'm uncertain if it's still there. They essentially proposed dropping a pellet containing deuterium- tritium into the focus for a 'Z pinch ' initiated implosion ten times per second. I don't know if either approach has any asperations to go beyond DT fusion.

Would a Z pinch or other form of collapsing magnetic field coupled with a laser or particle beam have a synergistic effect? Is it doable?

Dan Tibbets