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Using 8 Mega Volts DC as electric energy source?

  1. Jun 1, 2015 #1
    If a fusion reactor could be constructed that runs on Li-7 and hydrogen, and if the energy produced by that reactor where extracted with a direct charging setup, like in a nuclear battery emitting alpha particles, the voltage produced would be the stupendous voltage of 8 mega volts. Now, how do you get that into AC? Could an electric DC engine be constructed that runs on 8 mega volts? Or some other setup be used that turns 8 mega volts into useful electricity?
     
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  3. Jun 1, 2015 #2
    It would depend a lot on the geometry of the fusion reactor. In the best case I can think of high energy gamma rays would be semi-directional due to some sort of stimulated emission. (The uncertainty principal would prevent a clean beam I think.)

    That beam could be aimed at a plasma where heat might be extracted. But I can't think of a way to directly capture an 8MeV photon. That is well above any electron binding energy. In fact it is above the electron-positron pair production of about 1MeV. Perhaps a particle physicist would know more?

    But assuming we could capture it and use it to place an electron on the "uphill" side of a pair of conductors, we could build a DC motor and run a DC motor/AC generator pair. The motor would have some problems with insulation, but I'm sure something could be worked out.
     
  4. Jun 5, 2015 #3

    Hesch

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    I think you would have to build an (electronic) inverter.

    For long distance cables, DC voltage and current is used for power transmission (AC voltage and current will not work here).

    DC voltages of say 600kV are used here, and by arrival the DC-power is inverted to AC-power. Say you can easy make a 1MV inverter, just couple 8 of them in series. Couple the outputs in parallel through some transformers.
     
  5. Jun 5, 2015 #4
    But then you would need an 8MV transformer. I'm sure it could be done. :nb)
     
  6. Jun 5, 2015 #5

    jim hardy

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    I'd long wondered if one could pulse the reaction and step down the voltage with a backward Tesla coil - like buck converter.
    I don't know of any 8 megavolt thyristors.
     
  7. Jun 5, 2015 #6

    Hesch

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    Do you mean: I'm not sure . . . ?

    Anyway: As the inverters are coupled in series, you will need a 1MV transformer.
    It's much easier to build an say 8MV transformer, than it is to build a 8MV dc-motor.
    8 inverters in series. Also the thyristors can be / are coupled in series.
     
  8. Jun 5, 2015 #7
    No, I mean it could be done. But it wouldn't be easy. I don't think air could be used for an insulator for example. Further the insulator would need to be so thick I doubt a decent core could be used. Note that leaking electrons would produce hard gamma rays, so the insulation would need to be tight.

    I don't know which would be more trouble, a rotating machine in sulfur dioxide, or windings inches apart with no core. None of it is simple. Nor would efficiency be high.

    In fact the energy losses could be so great I would look for hot solution so the waste heat could be reused as a steam generator.

    Still this is all idle speculation because the step from an 8MeV photon to an 8MV bus is hand-waving as far as I can tell.
     
  9. Jun 5, 2015 #8

    Hesch

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  10. Jun 5, 2015 #9

    nsaspook

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  11. Jun 5, 2015 #10

    anorlunda

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    Where did you get that idea? Nuclear battery? 8 mega volts? Do you have a source?

    A point radiation source doesn't create a big electric charge as far as I know.
     
  12. Jun 5, 2015 #11

    Hesch

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    I wrote it at first (SF6) but regretted it as I thought it mostly is used with circuit-breakers?
    It is used to prevent/stop a fire. ( Fluorin is a halogen ).
     
    Last edited: Jun 5, 2015
  13. Jun 5, 2015 #12

    nsaspook

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    We use it in RF Linac resonators to insulate the tuning coil. Power level is only 3kW 80kV per tank with 15 PSI of SF6.
    https://www.physicsforums.com/threads/whats-inside-the-box.813916/
     
  14. Jun 5, 2015 #13

    Hesch

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    I don't know much about RF, but maybe special considerations must be taken to dielectric constants due to higher frequencies?
     
  15. Jun 5, 2015 #14

    nsaspook

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    Last edited: Jun 5, 2015
  16. Jun 5, 2015 #15

    Hesch

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    I was told a story (from Denmark) about a gardener who was staying very close to a radio-transmitter and had a lot of glasshouses to be heated up. So he made some big antenna and a resonator that could draw energy from the transmitter. I think it was more than 3kW.

    Some people came to measure how all this energy disappeared. Then they came and knocked his door. They had some questions for him. o_O
     
  17. Jun 6, 2015 #16
    A point radiation source can create an electric charge through stimulated absorption. However for stimulated absorption (sort of the reverse of a laser) to work there needs to be a stable(ish) quantum process that matches the photon's energy level. For example the photoelectric effect can knock electrons out of atoms, but this effect tops out at about 50keV, and even at that level translating the gain to a conducting bus isn't obvious to me. At lower levels of a few electron volts this effect is used in electronics such as solar panels.

    Compton scattering is a process where a photon (gamma ray) bounces off a charged particle (usually an electron) and transfers some of its energy into motion. It allegedly tops out at 10MeV (Wikipedia). I don't know why or what constraints this would have. Still, this would be why I speculated using the beam to heat a gas plasma would work. (Which does not give direct electrical energy).

    Still, maybe the OP has discovered some way of doing this and wanted to make sure the EE community could use an 8MV bus for power. :rolleyes: If so, I think he deserves a Nobel Prize. Such an effect would be much more efficient than using heat to generate steam.

    If you still have questions, one of the physics boards could probably answer them better and in more depth.
     
  18. Jun 6, 2015 #17
    Energy can be stolen from transmission lines by similar means. It is easy enough to do. It is also easy enough to detect. :mad: And yes, power companies do keep track of their stock in trade.
     
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