Recovery.Gov Project Tracker

[Skipjack]

Any management that doesn't expect problems doing R&D is incompetent.

That is true, but then we dont really know much to base optimism on. So I choose to be prepared for the worst, to not be disappointed later.

[MSimon]

I'll defer to Tom when he posts, but in the mean time, if I may walk out on a limb, let me say this.

It looks to me like the time required to form a Wiffleball is greater than the desired time between pulses and cool-down time is less than Wiffleball formation time. So they want to pulse the machine more rapidly to see if they can get some significant energy out. That's all good at first glance and I never stare at information.

It makes you go blind.

[MSimon]

100A power supply for 10 Kvolt electron guns. Now they're playing with power!

So they're needing a megawatt of input power on the electron guns alone, not mentioning the ion guns.

Does THAT number tell anyone anything about how well things are working?

Yes. A LOT of power. Energy? Well that depends. I have seen curves that show high current input for small machines and low current for large ones. Which might mean large currents on start up. Something not unlikely in any case (populating the device in a short time). Once the device is populated cut back the current. A capacitor bank fed by a constant current supply (voltage limited to x KV) might be a good start up/run device if the start up pulse is well understood. Or maybe a delay line (rather than just a capacitor bank) ala radar.

And suppose they decided to do a little advanced work on WB-D (formerly WB-100) by designing in bigger guns than they actually need?

Speculation is fun (its main value being entertainment).

[MSimon]

I was alwys a fan of big guns. Although small ones can be handy in a pinch.

[ladajo]

I think I have a solution for Electron Injection and Plasma Heating:

[happyjack27]

A couple of comments on the two posts preceding mine.

Boron can be delivered as a gas, decoboranes, etc. Basically a compound of a bunch of hydreogens stuck on a few borons. Issues of deposition of the boron/ boron compounds may be an issue. The decaboranes are also (moderately?) toxic. Deuterium is almost nontoxic. All you have to worry about is smothering yourself or blowing yourself up.

Ionization of neutral gas can supply a lot of secondary electrons, especially boron with a Z of 5. The 2007 pattent application mentions the consequences of this, even mentioning that it might be a problem of too many electrons. The alpha fusion ions may carry away more positive charges than the electron losses can balance against- it would be a run away increase in the electron to ion ratio, at least in theory. The building coulomb charge would of course limit this, but it illustrates another relationship that may need to be adjusted for .
As far as injection of energetic electrons, the the secondary electrons start their lives at low energy (ionization cross section peaks at ~ 100 eV) They contribute little to the depth of the potential well. They have to be heated by further collisions with the hot electrons, I once was uncertain how they were heated , as I thought that the secondary electron numbers might be similar to the injected electron numbers. But, actually the secondary electrons are ~= to the number of created ions (adjusted for Z). And as the ion lifetimes are perhaps 100 times greater than the electron lifetimes, the injected (or recirculated) electrons outnumber the secondary electrons by ~ 100 to 1. Thus the average temperature of the injected and secondary (from ionization) electrons will be close to the temperature of the injected electrons.

Dan Tibbets

good point. pellets or dust might be better than gas. one'd just have to do the calculus t o make sure it dissolves before it exits the other side of the wiffleball.

[mvanwink5]

Death Valley Days, those that remember the show with Ronald Reagan and 20 Mule Team Borax advertisements, and now, aboard the USS Ronald Reagan....

"COB, where do you want this fuel stored?"
"Next to the Laundry room, of course."

[D Tibbets]

....
Thus the average temperature of the injected and secondary (from ionization) electrons will be close to the temperature of the injected electrons.

Dan Tibbets

good point. pellets or dust might be better than gas. one'd just have to do the calculus t o make sure it dissolves before it exits the other side of the wiffleball.

Pellets or dust evaporating and ionizing before transiting the machine is only a partial solution. You also want the neutral gas (injected as gas or condensed particles) to ionize near the Wiffleball border., so that the ions are born near the peak of the potential well. Allowing ionization closer to the center compromises the near monoenergetic energy distribution of the ions.
The larger machines are more forgiving because the ionization of neutral gas is time dependent. Larger radius machines mean that the relative distance traveled before ionization is less compared to the radius of the machine. Arcing concerns are met so long as the gas ionizes sufficiently before transiting the entire machine, but mono energetic conditions are optimized if ionization occurs closer to the edge based on a total radius percentage.

Dan Tibbets

[D Tibbets]

100A power supply for 10 Kvolt electron guns. Now they're playing with power!

So they're needing a megawatt of input power on the electron guns alone, not mentioning the ion guns.

Does THAT number tell anyone anything about how well things are working?

Yes. A LOT of power. Energy? Well that depends. I have seen curves that show high current input for small machines and low current for large ones. Which might mean large currents on start up. Something not unlikely in any case (populating the device in a short time). Once the device is populated cut back the current. A capacitor bank fed by a constant current supply (voltage limited to x KV) might be a good start up/run device if the start up pulse is well understood. Or maybe a delay line (rather than just a capacitor bank) ala radar.

And suppose they decided to do a little advanced work on WB-D (formerly WB-100) by designing in bigger guns than they actually need?

Speculation is fun (its main value being entertainment).

If they are aiming for 1 MW ( 10,000 V at 100A) the implications are confusing (how many times have I said that? ). WB6 needed ~ 500,000W . Adusting the voltage down from 12,000 to 10,000 Volts would result in ~ 400-450,000 Watts of input electron power. If WB8.0 is twice the diameter, then input power should scale to > 1.6 MW.
This would suggest that their target for the current power supply is insufficient (and earlier WB8 efforts were even more insufficient). Perhaps WB7.0 and/ or WB7.1 (nubless?) performed substantially better than WB6 from a input power requirement, so the baseline is lower. This could be very good news.
But why the under performing power supply specs. Was it a money issue, is it an evolution of the understanding of start up requirements on larger/ stronger machines? Is it just to allow finesse in testing various parameters?

With capacitors. Thy may have had sufficient power (~1.5 to 2.5 MW)but only till the capacitors drained- end of test. With a stronger input power supply, the capacitors would not drain as fast and longer tests may be possible (this assumes that arcing is better controlled- this is what ended the WB6 test runs). Or as M. Simon said, capacitors for start up and power supply for steady state., though based on WB6 results steady state requirements would be well above 1 MW, unless above considerationsapply (?).

So many possibilities...

Dan Tibbets

[Skipjack]

With capacitors. Thy may have had sufficient power (~1.5 to 2.5 MW)but only till the capacitors drained- end of test.

I thought they were all pulsed until now anyway?

[happyjack27]

....
Thus the average temperature of the injected and secondary (from ionization) electrons will be close to the temperature of the injected electrons.

Dan Tibbets

good point. pellets or dust might be better than gas. one'd just have to do the calculus t o make sure it dissolves before it exits the other side of the wiffleball.

Pellets or dust evaporating and ionizing before transiting the machine is only a partial solution. You also want the neutral gas (injected as gas or condensed particles) to ionize near the Wiffleball border., so that the ions are born near the peak of the potential well. Allowing ionization closer to the center compromises the near monoenergetic energy distribution of the ions.
The larger machines are more forgiving because the ionization of neutral gas is time dependent. Larger radius machines mean that the relative distance traveled before ionization is less compared to the radius of the machine. Arcing concerns are met so long as the gas ionizes sufficiently before transiting the entire machine, but mono energetic conditions are optimized if ionization occurs closer to the edge based on a total radius percentage.

Dan Tibbets

yes, of course - if it ionizes near the center that means the ions will have low energy. so yeah you want it to ionize just at the wiffleball border. but actually, the ions are 8000 times heavier so at the same speed, they're going to have 8000 times more inertia. so even if it ionizes at the center, the ions will still have high energy. another factor to take into account when optimizing... oh, and i don't think the ions are mon-energetic. like planets around a solar system, they orbit at many different radii. and they tend to spread out like that - their aggregate orbit becomes a superposition of all possible orbits. so anyways you're optimizing the grain size and the speed, taking into accounts the ions will mantain their inertia while the electrons will latch on to the mag fields. introducing electrons closer to the center of the wb border is fine, they just contribute to the electrostatic pressure, helping it slowly puff out like a balloon. and again, the ions have their initial inertia contributing to their energy levels. you just have to make sure its not enough to make it to the magrid or the e-field inflection surface.

[mvanwink5]

You could synchronize firing a laser to ionize the pellet at the right place. Just a thought.

[ladajo]

I was looking at this again, and wonder how it relates to the current contract mod.

http://www.physics.usyd.edu.au/~khachan ... ersall.pdf

[happyjack27]

You could synchronize firing a laser to ionize the pellet at the right place. Just a thought.

sounds like an excellent idea to me. i would think "the right place" would be at the point inside the wiffleball boundary where the ions will have just enough momentum to be reflect just at the edge of the electrostatic well, with a safe margin. sort of like shuffle-ball.

[D Tibbets]

. Arcing concerns are met so long as the gas ionizes sufficiently before transiting the entire machine, but mono energetic conditions are optimized if ionization occurs closer to the edge based on a total radius percentage.

Dan Tibbets

yes, of course - if it ionizes near the center that means the ions will have low energy. so yeah you want it to ionize just at the wiffleball border. but actually, the ions are 8000 times heavier so at the same speed, they're going to have 8000 times more inertia. so even if it ionizes at the center, the ions will still have high energy. another factor to take into account when optimizing... oh, and i don't think the ions are mon-energetic. like planets around a solar system, they orbit at many different radii. and they tend to spread out like that - their aggregate orbit becomes a superposition of all possible orbits. so anyways you're optimizing the grain size and the speed, taking into accounts the ions will mantain their inertia while the electrons will latch on to the mag fields. introducing electrons closer to the center of the wb border is fine, they just contribute to the electrostatic pressure, helping it slowly puff out like a balloon. and again, the ions have their initial inertia contributing to their energy levels. you just have to make sure its not enough to make it to the magrid or the e-field inflection surface.

Not quite. The electrons and ions have about the same average energy KE. It is the velocity that is different. In WB6 the electrons were moving at ~ 10 million meters per second. If they hit something they will impart the same amount of energy. The ions, due to the difference in mass are traveling at a few hundred thousand meters per second. In WB 6, the injected neutral gas had a significant velocity, tiny compared to the charged particles, but high enough to pass from one side of the magrid to the other in a tiny fraction of a second. In WB6 enough transited the magrid and accumulated outside the machine so that arcing started within a few milliseconds.

The solar system analogy is similar to a thermalized plasma, except that it is a collisionless system(hopefully). A fusion plasma is a far different beast. And, you want all of the ions/ planets in the same orbit. Not only so that they can collide, but collide frequently with the best temperature (orbit ) that optimises the fusion crossection. In a thermalised plasma/ lower energy particles / lower orbit planets do not result in much fusion when they collide. Only the higher orbit planets do anything useful when they collide. This is a tremendous advantage for near mono energetic plasma. Almost all of the planets can participate in fusion (as opposed to perhaps 5 -10% in a Tokamak thermalised plasma) You can raize the orbits of the lower planets so that participate in fusions, but these means the up shifted higher orbit planets are still fusing, though perhaps at a slower rate, depending on the fusion cross section curve. The bigger problem though is the confinement issues, and especially the Bremsstrulung issues. That is why the claimed monoenergetic plasma in the Polywell can usefully fuse P-B11, or D-He3 fuel while thermalised machines like Tokamaks are limited to D-T fusion, or possibly D-D fusion if they are greatly improved.

I should mention that the Polywell may operated successfully with a thermalised plasma, but only for D-D or possibly D-He3 fuel. In a thermalised Polywell, the advantage over Tokamaks would primarily be the density/ confinement time issues.


And, ions born deep in the potential well have low energy/ velocity. The only way they can speed up is through collisions with other ions. This thermalization process is undesirable. Aside from thermal spread, it would effectively decrease the potential well's effect. An ion traveling at 10,000 eV, transferring KE to an ion at 1,000 eV would result in an energy of ~5,500 eV for each. That not only reduces the fusion cross section, it increases the further thermalization spread (Coulomb collision cross section increases as the KE drops), perhaps such that annealing cannot keep up.

Dan Tibbets