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What is the grid loss problem for fusion?

  1. Jan 15, 2017 #1
    Hello, I would like to ask for a definition the grid loss problem for fusion in inertial confinement fusion methods using fusors, and what it involves. Also, it was to ask what the main solutions being currently researched are, as it is very difficult to find papers on this field.

    Many thanks for the help. If you are aware of key publications on this subject, could you please send me a link as well.
     
  2. jcsd
  3. Jan 15, 2017 #2
    I believe a fusor is a kind of inertial electrostatic confinement to I might have something that could help you.


    Edit: attachments won't work.brb.
     
  4. Jan 15, 2017 #3
    Yes, that is the case. However, it was more to ask if the grid was the electrode of the fusor, or if the grid was the just the general containment of the plasma. Therefore, would the grid loss mean the deterioration of the electrode, or the loss of the control of the plasma.
     
  5. Jan 15, 2017 #4
    I believe the grid is the electrode. From what I have read it seems to result in loss of plasma. Dont quote me on this, I shall keep researching.

    And I cant do attachments for some reason to. Google inertial confinement fusion using fusors pdf
     
  6. Jan 15, 2017 #5
    Thank you very much for the help
     
  7. Jan 15, 2017 #6
    I don't know if you need to know but this type of fusion seems to be considered quite inefficient but that might be just in what I've read.
     
  8. Jan 15, 2017 #7
    The inertial electrostatic confinement (IEC) concept uses electric fields to accelerate ions into a core plasma. The inertia of these ions is used to heat and confine the plasma. To create the electric fields some IEC devices use a wire mesh that is immersed in the edge of plasma. Some of the ions collide with this mesh as they are accelerated into the core plasma. These collisions have a number of adverse effects, but simply put these collisions severely degrade the quality of confinement.

    I'll also point out that inertial confinement and and inertial electrostatic confinement are two very different confinement concepts. The grid problem only applies to IEC, and limited to IEC devices that uses a material grid to generate the electric field.
     
    Last edited: Jan 15, 2017
  9. Jan 16, 2017 #8

    Drakkith

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    Staff: Mentor

    The only solutions being researched that I know of is the Polywell device and perhaps a handful of other approaches that I don't have links for at the moment.
     
  10. Jan 16, 2017 #9
    There are several IEC concepts that use a virtual cathode. Of these concepts the Polywell has had the most success to date, but it's not the only idea. I think Lockheed Martian's high beta reactor is another example of an IEC concept that uses a virtual cathode that has received a lot of press. (I could be wrong. Lockheed is intentionally very vague about the details of their reactor).
     
  11. Jan 24, 2017 #10

    mheslep

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    Per wiki, Lockheed's design is a magnetic mirror concept, which is decades old. No IEC. The high beta aspect appears new, as is the small rector size.
     
  12. Jan 25, 2017 #11

    mheslep

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    T. Rider[/PLAIN] [Broken] detailed the several loss mechanisms for IEC fusion in the 90s. For a centimeter scale electrostatic device, 60kV, with grid transparency of 99%, the ratio of grid power loss to fusion power generated could be 3000:1. As the author indicates, heat dissipation alone from the grid is an intractable problem.
     
    Last edited by a moderator: May 8, 2017
  13. Jan 25, 2017 #12
    I'm not sure if Lockheed's design is a pure magnetic mirror or if it's a magnetic mirror IEC hybrid. Skunk Works is intentionally vague in many of the details surrounding their device. Skunk Works is a secretive branch of Lockheed Martin, so this isn't really that surprising. In my experience they have been particularly secretive on their intent to use a virtual cathode or not to. The wikipedia article doesn't really tell you enough to figure out if Lockheed Martin's design is a cusp confinement concept with a virtual cathode (making it IEC) or a cusp confinement concept without a virtual cathode (not IEC).

    I suspect that they plan to use a virtual cathode based on the following:

    Dr. T McGuire's , the lead scientist on the Lockheed Reactor, background is in IEC.

    Arguably the most promising IEC devices use a virtual cathode. All devices that use a virtual cathode need some way to confine the cathode to it's center. Cusp magnetic field configurations have traditionally been used to this end (the Polywell for example). For this reason cusps are popular in the IEC community.

    The cusp as a pure magnetic confinement concept has a number of flaws related to end losses. You need to address these flaws in order for it to be a viable fusion reactor.

    I argue that if someone with a background in IEC is proposing a reactor that uses cusp confinement, then there is a good chance that they are going to use a virtual cathode unless they specifically say otherwise. Of course this isn't proof. Do you know of any instance where they have directly addressed this question? If so I'd be interested to hear what they said.

    High beta is a reference to a theory by Harold Grad that dates back to the early days of fusion research. The theory suggests that the confinement of a cusp should improve at high beta. It's certainly not a new idea, and it is not unique to the Lockheed's design. The Polywell will also benefit from this effect. In fact the improved confinement was recently observed on a Polywell.

    Sorry, this is one of my peeves. The small reactor size idea also isn't new. Almost everyone in the fusion community recognizes the benefits that a small reactor would provide. However, there really isn't any data that suggests Lockheed Martin's design will achieve that goal, and there is decades of research into a variety of different concepts that suggests that it is a lot harder to build a compact fusion reactor than advertised. Lockheed isn't the only ones considering a small reactor concept. Many of the venture capital funded firms are promoting some sort of small reactor design. As a fusion scientist I wish them all luck, and I think it's good that they're trying out some alternative concepts. But the models that these "small" reactor designs are based on ignore turbulence. Turbulence is the dominate transport mechanism in every mature magnetic confinement concept to date. If it wasn't for turbulence we would have likely solved fusion decadesago. Turbulence is the reason why we can't build a small tokamak reactor with existing technology. If you want to make a compelling argument that a small reactor can ignite, then you need a realistic turbulence model.
     
  14. Feb 2, 2017 #13
    The Lockheed-Martin scam is one of the greatest fusion frauds since Ronald Richter at Huemel Island ca. 1950.

    It ranks right up there with cold fusion.
     
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