Mannhart's thermionic converter principles for fusion

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ohiovr
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Mannhart's thermionic converter principles for fusion

Post by ohiovr »

For reference to this discussion:

http://publishing.aip.org/publishing/jo ... -generator

I am not sure how this beast works. The application of a uniform magnetic field to the gap allows electrons to traverse the gap while being accelerated by a few volts of dc though a grid. The grid is charged, electrons see it and move toward it, then as they go though the grid, they accelerate, then decelerate after traversing the center, then hit the anode and all is well. I had emailed Dr Mannhart about his gate (grid), and he says that it is very transparent.

What is going on here?

Isn't this the key to getting the Fusor to work, getting the particles to accelerate to a grid, then at the same time, not slam into said grid and lose all their energy, recover their energy by slinging to the other sided and passing back though again? Thoughts?
Last edited by ohiovr on Thu Nov 06, 2014 12:29 am, edited 1 time in total.

hanelyp
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Re: Mannhart's thermionic converter principles for fusion

Post by hanelyp »

Previous models of thermionic generators have proven ineffectual because of what is known as the "space-charge problem," in which the negative charges of the cloud of electrons leaving the hot plate repel other electrons from leaving it too, effectively killing the current. Mannhart, along with his former students Stefan Meir and Cyril Stephanos, and colleague Theodore Geballe of Stanford University, circumvented this problem using an electric field to pull the charge cloud away from the hot plate, which allowed electrons to fly to the cold plate.
If I'm understanding correctly, a thermoelectric triode, as opposed to diode. A grid between the cathode and anode pulls electrons away from the cathode. The electrons pass through the grid, then because they started with extra energy from heat or light they can climb to an anode negative relative to the cathode.

Grid transparency good enough for this could be several orders of magnitude short of what a Farnworth fusor needs to break even.
The daylight is uncomfortably bright for eyes so long in the dark.

ohiovr
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Re: Mannhart's thermionic converter principles for fusion

Post by ohiovr »

hanelyp wrote:
Previous models of thermionic generators have proven ineffectual because of what is known as the "space-charge problem," in which the negative charges of the cloud of electrons leaving the hot plate repel other electrons from leaving it too, effectively killing the current. Mannhart, along with his former students Stefan Meir and Cyril Stephanos, and colleague Theodore Geballe of Stanford University, circumvented this problem using an electric field to pull the charge cloud away from the hot plate, which allowed electrons to fly to the cold plate.
If I'm understanding correctly, a thermoelectric triode, as opposed to diode. A grid between the cathode and anode pulls electrons away from the cathode. The electrons pass through the grid, then because they started with extra energy from heat or light they can climb to an anode negative relative to the cathode.

Grid transparency good enough for this could be several orders of magnitude short of what a Farnworth fusor needs to break even.
What is the purpose of the magnetic field? I'm not exactly sure myself

ohiovr
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Re: Mannhart's thermionic converter principles for fusion

Post by ohiovr »

Also it should be noted that Hatsopoulos and Gyftopoulos and co tried something similar but the results were completely useless without the magnetic field (Mannhart's contribution).

ohiovr
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Re: Mannhart's thermionic converter principles for fusion

Post by ohiovr »

hanelyp wrote:
Previous models of thermionic generators have proven ineffectual because of what is known as the "space-charge problem," in which the negative charges of the cloud of electrons leaving the hot plate repel other electrons from leaving it too, effectively killing the current. Mannhart, along with his former students Stefan Meir and Cyril Stephanos, and colleague Theodore Geballe of Stanford University, circumvented this problem using an electric field to pull the charge cloud away from the hot plate, which allowed electrons to fly to the cold plate.
If I'm understanding correctly, a thermoelectric triode, as opposed to diode. A grid between the cathode and anode pulls electrons away from the cathode. The electrons pass through the grid, then because they started with extra energy from heat or light they can climb to an anode negative relative to the cathode.

Grid transparency good enough for this could be several orders of magnitude short of what a Farnworth fusor needs to break even.
Thermions leaving the cathode cannot pass to the anode if the grid is the same in terms of polarity in its respect. More negative on the gate means fewer electrons will get to the anode, more positive means more electrons make it to the anode. In this way you can control a very large current with a very small current.

hanelyp
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Re: Mannhart's thermionic converter principles for fusion

Post by hanelyp »

ohiovr wrote:More negative on the gate means fewer electrons will get to the anode, more positive means more electrons make it to the anode. In this way you can control a very large current with a very small current.
Which is the principle behind the classic triode vacuum tube. The grid produces a potential hill or a dip between cathode and anode.

I can't encourage too much the studying the basics of the old tubes for people wanting to understand the polywell.
What is the purpose of the magnetic field? I'm not exactly sure myself
The illustrations in the more technical article I found following links didn't clearly show there was a magnetic field. My best guess is a field oriented parallel to desired electron path, reducing diversion to the grid. A magnetic field any other direction would stand in the way of the electrons.
The daylight is uncomfortably bright for eyes so long in the dark.

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