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  1. #31

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    Quote Originally Posted by Struan Gray View Post
    True, but there are some interesting applications for a tunable benchtop neutron source, and that's before you get into the wilder power-source-on-a-chip dreams of the nano-technologists.
    No doubt. And that's ample reason to study these kinds of configurations.

  2. #32

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    Quote Originally Posted by Struan Gray View Post
    ... there are some interesting applications for a tunable benchtop neutron source... :-)
    There is actually a benchtop neutron source, though I don't know how tunable it is. I believe it has been commercialized by a German company.

    The device is called a "fusor". It was invented by Philo T. Farnsworth, the person largely credited with inventing television. Interestingly (for me at least) Philo was my grandmother's cousin, and I met his widow at a family party some years ago.

  3. #33

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    Some twenty years ago I worked at a company where a Cornell PhD graduate also worked. He told me that in the fusion program they scheduled their "breakthroughs". It was all part of the funding process.

    This all reminds me of the saying: "fusion is the energy source of the future. Always has been. Always will be."

  4. #34

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    If you could shorten the D-D bond length by a bit (I don't remember how much, but I did research this back when cold fusion was in the news, and as I recall it was a few tens of percent) fusion rates would become significant. In that kind of a system you don't need to have a high tunneling rate, unlike in a collisional process, because the nuclei would be close together for a long long long time, unlike in a collision where they are in proximity for picoseconds or less (probably much much much less.)

  5. #35

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    PhD's at universities publish grad student research to get more grants to hire more grad students to do more research. Its a terrific energy source that bypasses the laws of thermodynamics and economics by using those of P. T. Barnum.

  6. #36

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    Quote Originally Posted by alanrockwood View Post
    Some twenty years ago I worked at a company where a Cornell PhD graduate also worked. He told me that in the fusion program they scheduled their "breakthroughs". It was all part of the funding process.

    This all reminds me of the saying: "fusion is the energy source of the future. Always has been. Always will be."
    I have to call bull on this. A lot of people work really hard on it. Nobody schedules breakthroughs. The larger projects (10's of millions of dollars/year) do have milestones each year, and like in any large bureaucratic system, they are set conservatively so there is little chance of failure. However, at least since the late 70's/early 80's, the whole 'fusion will be here in 20-30 years' was dependent on an Apollo style funding scheme. Budgets that grew every year, as needed. Needless to say, that didn't happen, and instead large cuts happened. Even now, 25 years later, the US fusion budget is only a fraction of what it was in the early 80's (in real dollars).

    Personally, I think it's ridiculous that we only budget about $300 million a year for this kind of research. Oil won't last forever. And if you think $300 million/year sounds like a lot of money, look into to how much fission reactors cost to build now and how long they take to be built. The last plant built in the US took 23 years to build. I've also read that new plant cost estimates are in the $15 billion range.

    The rest of the world seems to have a clue. Japan has two billion dollar class projects, and they fought tooth and nail with France to host ITER, just to be able to foot 50-60% of the $10 billion in costs (ITER is the international collaboration to build a tokamak that reaches a Q of 10; 10 times the energy out that was put in). France fought back and is the host. The EU has several large devices in operation. The US on the other hand rejoined ITER late as a minor partner, after we helped start it all in the late 80's. We wanted nothing to do with hosting it. The US's most advance fusion project was initially built in the mid-80's. Though it has been upgraded... way to go USA.

  7. #37

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    An interesting, truly tabletop device is available commercially for neutron production. It is the Zetatron (http://en.wikipedia.org/wiki/Zetatron), and it was derived fron the neutron generators used in nuclear weapons. But this device is a long term laboratory tool rather than a one shot device. Some models are tunable, at least to some extent.

  8. #38
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    Not quite sure how we got onto the subject of tabletop neutron sources, but if it were me, I make up a little H2 plasma bottle, strip off electrons to get protons, accelerate the protons across whatever potential I choose, and then slam them into paraffin. Neutrons aplenty. Looking at that 'zetatron' schematic, I'd guess that the "target" is a paraffin block. As I learned form my visit yesterday, if you want gobs of neutrons but don't want a reactor, then you'd use the technique at the SNS in Oak Ridge- liquid mercury getting slammed with protons from a simple linac. A cuter and more compact technology is the DWA (dielectric wall accelerator) now under development for medical applications at Livermore in collaboration with Tomotherapy. That proton therapy device will be in every cancer hospital within 2-3 decades, mark my words.

    I am skeptical that one would want all that zetatron complication in a weapon... it's easy to generate a shower of neutrons from fission. OTOH maybe the zetatron finds application in the baby nukes that contain a net sub-critical mass. But I digress
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  9. #39

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    Quote Originally Posted by Tim Gray View Post
    I have to call bull on this... Nobody schedules breakthroughs. The larger projects (10's of millions of dollars/year) do have milestones each year, and like in any large bureaucratic system, they are set conservatively so there is little chance of failure.
    Tim,

    You could be right that nobody schedules breakthroughs. All I am doing is propagating an unsubstantiated comment from someone I knew who also had known some of the fusion guys. (I think this is what is known as spreading gossip... guilty as charged.)

    On the other hand I once worked on a US department of energy-funded project. It would not be considered a large project on the scale you proposed (10's of millions of dollars per year)... probably more along the lines of a medium sized project (around a million dollars per year.) We had an interesting mandate for the project, which was to design and build an instrument that was beyond the state of the art, and we had to do it with a zero probability of failure. (I realize that those are mutually incompatible requirements, but that was the mandate.) This wasn't exactly scheduling a breakthrough, but it would come pretty close to that characterization.

    One of the things that the project required was to acquire a superconducting magnet having a combination of field strength, bore size, and stability significantly beyond anything that had been built to date, and we had to do it with a limited budget. It turned out to be impossible using the then-current state of the art, so we had to scale back the field strength a little. I left before the project was finished, but I understand from those who stayed that the stability of the magnet was a little disappointing. However. in the end the instrument set a new standard for that type of instrument.

  10. #40

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    Many technologies weren't around 100--200-300etc years ago.
    When the people working on them were held up to ridicule.
    Today, some of those experiments and theories that were off the tradtional
    direction of then current science are now everyday things.
    I guess the point is "never say never".
    Expletive Deleted!

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