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Thread: power system idea

  1. #1 power system idea 
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    1) Could a lasing material, say nitrogen gas or artificial rubies, be placed so that it absorbs gamma radiation, then radiate that energy at a lower, more manageable, frequency? If that is possible, could the light from that lasing material be converted, via PV cells, into useful electricity? I know the main problem with PV array efficiency is that wide range of frequencies it must convert. It shouldn't be hard to convert a single frequency.
    2) could you transfer electricity via laser emitters and PV cells, say using fiberoptic cable instead of wires? How would the energy density and efficiency compare to normal power systems?


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    Gamma radiation is as far as I understand the nomenclature, non-particulate in nature, and therefore would not be "absorbed" as such. jocular


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    Nitrogen can be ionized and still work, as far as I know (UV lasers). I thought that a gem could be strong enough to not be ionized, as well, especially if you don't bombard it with huge numbers of gamma rays.
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    Quote Originally Posted by TheUnknowable View Post
    Nitrogen can be ionized and still work, as far as I know (UV lasers). I thought that a gem could be strong enough to not be ionized, as well, especially if you don't bombard it with huge numbers of gamma rays.
    Ionization thresholds for typical materials -- including gems -- are in the eV to 10eV range, as a rough order of magnitude. We're not talking keV or MeV, in any case. Gamma rays, though, have energies north of 100keV. So, you're going to break a lot of bonds, as PhDemon suggests.
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    Does that really matter when the only thing in it is N2 molecules? Sure, they'll seperate, but they can only go back together one way.
    Also, ionized particles can have the electric charge removed from them qite easily.
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    I'm not sure what the difference between ionized molecules and "excited" molecules are if the material isn't changed.
    Is it too energetic to collect energy from, say with two different metal plates?
    Could it be used to excite another lasing material by lowering the energy they are subjected to?
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    Won't the electron rejoin the ion and release light from that point on? I'm sure you could pump enough energy into it so that it would never happen, but at lower Gamma ray levels, wouldn't it stabilize itself?
    I knew how a laser worked, I was just confusing ionization with breaking the molecular bond in the chemical for some reason (probably because I haven't looked at chemistry in the last few years.)

    Could lasers, or gamma rays, be used to transfer energy more effectively (#2)? The main problem with energy transfer is the resistance of the wire to the electron flow. This makes it difficult to put a lot of energy through, as high voltage ionizes the air and high amperage heats the wire. I thought fiber optics would be far more efficient at transferring it.
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    Why does it have to strike "just right" when you only have nitrogen molecules in it? Shouldn't all of the energy you put in be re-released as photons as long as you don't put in too much gamma radiation? I'm thinking of the possibility of using it as a method of reclaiming energy from an aneutronic fusion reaction.

    If this CAN'T work, please explain why. Don't just say "you need to study it". I'm asking the question in order to learn, but if I don't get an explanation why, it doesn't do any good.
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    Won't the kinetic energy be absorbed by the nitrogen in the form heat?

    Your explanations don't make sense to anyone who hasn't studied it, and you don't want to explain further so that others CAN understand it. Do you have a source so that I can learn more? I've looked for one, but I don't know what I'm looking for.
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  11. #10  
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    In other words "you don't REALLY understand it, so giving you the answer a different way won't help". I DO know how a laser works. Knowing how it works doesn't explain why a gamma ray can't be used to excite it. It also doesn't answer my other questions about using the plasma created by gamma rays to excite a laser.

    If you don't want to answer my question, just say so. Don't keep saying "I did explain." If I tried to explain the theory of relativity to you and you still didn't get it, would it really be a worthwhile expalination? What if you asked about how sugar is metabolized and you said "the cells use it for energy"? Does that answer the question?
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    Apparently you think that any attempt to use a gamma ray to excite a medium will ionize it, despite the fact that Gamma ray lasers exist. Yes, I understand that ionized materials won't lase. That's not what I'm suggesting now, though, (see #10 and any post since then) and I have already explained that, so maybe you are the one that doesn't understand.
    Alpha, Beta, and Neutron radiation have been used to produce lasers. Other frequencies of light are routinely used to excite a material. Explain why low amounts of gamma (say from K-40) can't be used to ionize the material, which then excites another (or separate, but same material) lasing material to make a laser. Why can't the light the plasma releases be converted into electricity directly? What prevents it from being scaled up to fusion-reactor levels of gamma radiation?

    You've also ignored the second question.

    Also, there are at least two errors in your post, one spelling, a typo. When you're trying to prove you're smarter than someone, it helps to spell things correctly.

    Edit: fixed a grammatical error, namely "'t"
    Last edited by TheUnknowable; July 28th, 2013 at 02:56 PM.
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    I don't have an attitude problem. I came on here to learn. You tell me "that won't work". I ask why, you explain, I say ok, then ask something different. Then you start on about how I don't understand anything, how you've explained everything, and how I'm just too ignorant to understand. None of that answered my questions. It only makes you, in your own eyes, look smart.
    My guess is that you don't know why my ideas won't work, but don't want to admit they they could, as you've already said that they wouldn't and that would mean that you were wrong. You therefore ignore my comments, except the parts that help your belief that I'm stupid, or ignorant, or have an attitude problem, or whatever else will make me look bad. This is especially evident when I post an explaination of exactly what my position is and what I want to know, including why I think that, and you latch onto the last sentence where I point out a few minor mistakes you made.
    I would suggest that it is YOU that has an attitude problem, as your behavior is more like that of an argumentative child than that of a teacher.
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  14. #13  
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    Quote Originally Posted by TheUnknowable View Post
    I don't have an attitude problem. I came on here to learn. You tell me "that won't work". I ask why, you explain, I say ok, then ask something different. Then you start on about how I don't understand anything, how you've explained everything, and how I'm just too ignorant to understand. None of that answered my questions. It only makes you, in your own eyes, look smart.
    My guess is that you don't know why my ideas won't work, but don't want to admit they they could, as you've already said that they wouldn't and that would mean that you were wrong. You therefore ignore my comments, except the parts that help your belief that I'm stupid, or ignorant, or have an attitude problem, or whatever else will make me look bad. This is especially evident when I post an explaination of exactly what my position is and what I want to know, including why I think that, and you latch onto the last sentence where I point out a few minor mistakes you made.
    I would suggest that it is YOU that has an attitude problem, as your behavior is more like that of an argumentative child than that of a teacher.
    I'm a little surprised at what has NOT come up in this discussion. First, surely the point is that gamma radiation arises from quantum transitions within the nucleus, which involve energy changes several orders of magnitude greater than those involved in electronic transitions, whether atomic or molecular. It is thus obvious gamma rays are far too powerful to take part in any process involving bound electrons in an atom or molecule - hence PhDemon's dismissal of the idea that a conventional "lasing material" as you call it, might be able to handle gamma rays.

    To my knowledge, no gamma ray laser has yet been built, but it were, it would depend on creating a population inversion of excited nuclear states, not electronic states.

    I am not aware of any process whereby an excited nucleus can return to the ground state via transfer of its energy to the surrounding electrons in the atom. So I do not see how you can get gamma ray photons converted to visible ones in the way you suggest. If you want to progress this idea of yours, I think this is the issue you need to address.
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  15. #14  
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    Quote Originally Posted by TheUnknowable View Post
    Apparently you think that any attempt to use a gamma ray to excite a medium will ionize it, despite the fact that Gamma ray lasers exist.
    Gamma ray laser do not exist (on earth). Where did you get this idea? In fact, x-ray lasers don't exist (I do not count the claims of the "Star Wars" researchers; I have looked at the data, and it is too weak to support such a bold claim), and x-rays are much less energetic than gamma rays (by orders of magnitude).
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  16. #15  
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    Quote Originally Posted by tk421 View Post
    Quote Originally Posted by TheUnknowable View Post
    Apparently you think that any attempt to use a gamma ray to excite a medium will ionize it, despite the fact that Gamma ray lasers exist.
    Gamma ray laser do not exist (on earth). Where did you get this idea? In fact, x-ray lasers don't exist (I do not count the claims of the "Star Wars" researchers; I have looked at the data, and it is too weak to support such a bold claim), and x-rays are much less energetic than gamma rays (by orders of magnitude).
    I saw a few papers on how they could theoretically be made and got confused, thinking they had already been made. Also, I thought this qualified (Induced gamma emission - Wikipedia, the free encyclopedia).
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  17. #16  
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    Quote Originally Posted by exchemist View Post
    Quote Originally Posted by TheUnknowable View Post
    I don't have an attitude problem. I came on here to learn. You tell me "that won't work". I ask why, you explain, I say ok, then ask something different. Then you start on about how I don't understand anything, how you've explained everything, and how I'm just too ignorant to understand. None of that answered my questions. It only makes you, in your own eyes, look smart.
    My guess is that you don't know why my ideas won't work, but don't want to admit they they could, as you've already said that they wouldn't and that would mean that you were wrong. You therefore ignore my comments, except the parts that help your belief that I'm stupid, or ignorant, or have an attitude problem, or whatever else will make me look bad. This is especially evident when I post an explaination of exactly what my position is and what I want to know, including why I think that, and you latch onto the last sentence where I point out a few minor mistakes you made.
    I would suggest that it is YOU that has an attitude problem, as your behavior is more like that of an argumentative child than that of a teacher.
    I'm a little surprised at what has NOT come up in this discussion. First, surely the point is that gamma radiation arises from quantum transitions within the nucleus, which involve energy changes several orders of magnitude greater than those involved in electronic transitions, whether atomic or molecular. It is thus obvious gamma rays are far too powerful to take part in any process involving bound electrons in an atom or molecule - hence PhDemon's dismissal of the idea that a conventional "lasing material" as you call it, might be able to handle gamma rays.

    To my knowledge, no gamma ray laser has yet been built, but it were, it would depend on creating a population inversion of excited nuclear states, not electronic states.

    I am not aware of any process whereby an excited nucleus can return to the ground state via transfer of its energy to the surrounding electrons in the atom. So I do not see how you can get gamma ray photons converted to visible ones in the way you suggest. If you want to progress this idea of yours, I think this is the issue you need to address.
    That's why I proposed using the ionized material produced by gamma ray impacts to excite the material instead of the gamma ray itself. This would regulate the amount of energy the material has to absorb at once. (Essentially using a capacitor to store an electrical discharge, the discharging the capacitor slowly. In this case, the ionized nitrogen plasma would be a capacitor. It changes the high voltage gamma ray into many (higher amperage) low voltage ions.)
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  18. #17  
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    Quote Originally Posted by TheUnknowable View Post
    Quote Originally Posted by exchemist View Post
    Quote Originally Posted by TheUnknowable View Post
    I don't have an attitude problem. I came on here to learn. You tell me "that won't work". I ask why, you explain, I say ok, then ask something different. Then you start on about how I don't understand anything, how you've explained everything, and how I'm just too ignorant to understand. None of that answered my questions. It only makes you, in your own eyes, look smart.
    My guess is that you don't know why my ideas won't work, but don't want to admit they they could, as you've already said that they wouldn't and that would mean that you were wrong. You therefore ignore my comments, except the parts that help your belief that I'm stupid, or ignorant, or have an attitude problem, or whatever else will make me look bad. This is especially evident when I post an explaination of exactly what my position is and what I want to know, including why I think that, and you latch onto the last sentence where I point out a few minor mistakes you made.
    I would suggest that it is YOU that has an attitude problem, as your behavior is more like that of an argumentative child than that of a teacher.
    I'm a little surprised at what has NOT come up in this discussion. First, surely the point is that gamma radiation arises from quantum transitions within the nucleus, which involve energy changes several orders of magnitude greater than those involved in electronic transitions, whether atomic or molecular. It is thus obvious gamma rays are far too powerful to take part in any process involving bound electrons in an atom or molecule - hence PhDemon's dismissal of the idea that a conventional "lasing material" as you call it, might be able to handle gamma rays.

    To my knowledge, no gamma ray laser has yet been built, but it were, it would depend on creating a population inversion of excited nuclear states, not electronic states.

    I am not aware of any process whereby an excited nucleus can return to the ground state via transfer of its energy to the surrounding electrons in the atom. So I do not see how you can get gamma ray photons converted to visible ones in the way you suggest. If you want to progress this idea of yours, I think this is the issue you need to address.
    That's why I proposed using the ionized material produced by gamma ray impacts to excite the material instead of the gamma ray itself. This would regulate the amount of energy the material has to absorb at once. (Essentially using a capacitor to store an electrical discharge, the discharging the capacitor slowly. In this case, the ionized nitrogen plasma would be a capacitor. It changes the high voltage gamma ray into many (higher amperage) low voltage ions.)
    OK, I can see you could in principle accumulate a plasma of ionised material, containing some very high energy electrons. But then what? To get the laser going, you would need to somehow get these very energetic (and destructive!) species to "pump" the laser, i.e. to create the required population inversion of electronic states by exciting the "pump" transition(s) of the laser.

    How could this be made to work?
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    Quote Originally Posted by exchemist View Post
    OK, I can see you could in principle accumulate a plasma of ionised material, containing some very high energy electrons. But then what? To get the laser going, you would need to somehow get these very energetic (and destructive!) species to "pump" the laser, i.e. to create the required population inversion of electronic states by exciting the "pump" transition(s) of the laser.

    How could this be made to work?
    Not quite sure. I assumed that simply exposing the sides of it would make it pulse (or with enough energy, remain constant) as the energy built up, reached population inversion, then emit the light. I've never actually built a laser, though. I want to build a UV laser with air or a CO2 laser.
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  20. #19  
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    Quote Originally Posted by TheUnknowable View Post
    Quote Originally Posted by tk421
    Gamma ray laser do not exist (on earth). Where did you get this idea? In fact, x-ray lasers don't exist (I do not count the claims of the "Star Wars" researchers; I have looked at the data, and it is too weak to support such a bold claim), and x-rays are much less energetic than gamma rays (by orders of magnitude).
    I saw a few papers on how they could theoretically be made and got confused, thinking they had already been made. Also, I thought this qualified (Induced gamma emission - Wikipedia, the free encyclopedia).
    To make a laser, you need gain (the "a" in "laser" stands for amplification). Merely fluorescing doesn't qualify. Not by a long shot. Fluorescence was observed a good long time before lasers were even imagined, let alone constructed. That historical sequencing by itself should tell you a great deal.

    ETA: If the specific IGE implementation you were thinking of involves hafnium, you should be aware that Carl Collins is a seriously ill crank.

    Again, given that we haven't even succeeded in making an x-ray laser (and the "Star Wars" attempt needed a fission bomb to pump it -- I am not making this up), a terrestrial gamma-ray laser is a fantasy.

    ETA: I am using a "purist's" definition of laser, which does not consider a free-electron laser to be an actual laser. We certainly do have x-ray FELs, but they would be wholly unsuitable for the problem you say you wish to solve.
    Last edited by tk421; July 30th, 2013 at 07:04 PM.
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    All I really need is the energy converted into something useful. If it can make light, I can use a PV cell to make electricity. Could some device other than a laser convert the ionization into light? Could you pull the energy from the plasma directly?
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  22. #21  
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    Quote Originally Posted by TheUnknowable View Post
    All I really need is the energy converted into something useful.
    Where are you imagining this gamma radiation to come from, in a quantity sufficient to be a useful form of energy? (Without it killing people )
    ei incumbit probatio qui dicit, non qui negat
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  23. #22  
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    Quote Originally Posted by TheUnknowable View Post
    Quote Originally Posted by exchemist View Post
    OK, I can see you could in principle accumulate a plasma of ionised material, containing some very high energy electrons. But then what? To get the laser going, you would need to somehow get these very energetic (and destructive!) species to "pump" the laser, i.e. to create the required population inversion of electronic states by exciting the "pump" transition(s) of the laser.

    How could this be made to work?
    Not quite sure. I assumed that simply exposing the sides of it would make it pulse (or with enough energy, remain constant) as the energy built up, reached population inversion, then emit the light. I've never actually built a laser, though. I want to build a UV laser with air or a CO2 laser.
    I think normally the laser is pumped using light (that is, EM radiation) of the correct frequency. Your plasma however is not radiation, it is particles. It may glow, but if it does, this will be glow of the continuum, not of any special frequency, so it seems to me hard to see how energy can be efficiently transferred to the pump transition band of the laser.
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  24. #23  
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    Quote Originally Posted by exchemist View Post
    Quote Originally Posted by TheUnknowable View Post
    Quote Originally Posted by exchemist View Post
    OK, I can see you could in principle accumulate a plasma of ionised material, containing some very high energy electrons. But then what? To get the laser going, you would need to somehow get these very energetic (and destructive!) species to "pump" the laser, i.e. to create the required population inversion of electronic states by exciting the "pump" transition(s) of the laser.

    How could this be made to work?
    Not quite sure. I assumed that simply exposing the sides of it would make it pulse (or with enough energy, remain constant) as the energy built up, reached population inversion, then emit the light. I've never actually built a laser, though. I want to build a UV laser with air or a CO2 laser.
    I think normally the laser is pumped using light (that is, EM radiation) of the correct frequency. Your plasma however is not radiation, it is particles. It may glow, but if it does, this will be glow of the continuum, not of any special frequency, so it seems to me hard to see how energy can be efficiently transferred to the pump transition band of the laser.
    Probably in a similar way to alpha and beta particles are used to drive a laser, as they are highly charged elementary particles (Okay, an alpha is a helium nucleus). I'll have to look into it.
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    Quote Originally Posted by Strange View Post
    Quote Originally Posted by TheUnknowable View Post
    All I really need is the energy converted into something useful.
    Where are you imagining this gamma radiation to come from, in a quantity sufficient to be a useful form of energy? (Without it killing people )
    One of several gamma producing radioactive materials (If I want it to be an atomic battery) or a fusion reactor (possibly anuetronic, though if you had enough material surrounding it, it could hold most of the neutrons for 10 minutes, until they undergo proton decay).
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  26. #25  
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    Quote Originally Posted by TheUnknowable View Post
    Quote Originally Posted by exchemist View Post
    Quote Originally Posted by TheUnknowable View Post
    Quote Originally Posted by exchemist View Post
    OK, I can see you could in principle accumulate a plasma of ionised material, containing some very high energy electrons. But then what? To get the laser going, you would need to somehow get these very energetic (and destructive!) species to "pump" the laser, i.e. to create the required population inversion of electronic states by exciting the "pump" transition(s) of the laser.

    How could this be made to work?
    Not quite sure. I assumed that simply exposing the sides of it would make it pulse (or with enough energy, remain constant) as the energy built up, reached population inversion, then emit the light. I've never actually built a laser, though. I want to build a UV laser with air or a CO2 laser.
    I think normally the laser is pumped using light (that is, EM radiation) of the correct frequency. Your plasma however is not radiation, it is particles. It may glow, but if it does, this will be glow of the continuum, not of any special frequency, so it seems to me hard to see how energy can be efficiently transferred to the pump transition band of the laser.
    Probably in a similar way to alpha and beta particles are used to drive a laser, as they are highly charged elementary particles (Okay, an alpha is a helium nucleus). I'll have to look into it.
    I confess I have never heard of a laser being driven by alpha or beta particles and cannot immediately see how this would be done either.

    Can you refer me to an example of either of these?
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    Quote Originally Posted by TheUnknowable View Post
    Quote Originally Posted by exchemist
    I think normally the laser is pumped using light (that is, EM radiation) of the correct frequency. Your plasma however is not radiation, it is particles. It may glow, but if it does, this will be glow of the continuum, not of any special frequency, so it seems to me hard to see how energy can be efficiently transferred to the pump transition band of the laser.
    Probably in a similar way to alpha and beta particles are used to drive a laser, as they are highly charged elementary particles (Okay, an alpha is a helium nucleus). I'll have to look into it.
    I have never heard of "alpha and beta particles" used to drive any laser, even sci-fi ones. I think you are making stuff up now. At minimum, you have demonstrated a near-total lack of knowledge of how a laser works.

    But setting all this aside, what is it, exactly, that you want to accomplish with all of this? If you could be a little clearer about what the goal is, we could avoid bogging down with possibly irrelevant minutiae. As it is, it's hard to tell if the laser stuff is important or irrelevant to what you're trying to do. Could you explain more?
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    Quote Originally Posted by PhDemon View Post
    Fantasy physics at it's best/worst from TheUnknowable. I was prepared to think I was just having a bad day when I posted earlier in this thread. Looks like I was right...
    The closest thing I could imagine would be free-electron and free-proton lasers, but no alphas are involved in any laser scheme I'd ever heard discussed. Even if that's what he might have been thinking, I don't quite get how it connects to what his thread is about. Of course, it would help if I knew what his thread is about...
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    I can't find the website I read about alpha radiation firing a laser on now. I did find one about using neutrons to fire it, though, so the alpha radiation isn't that important.

    This thread is about increasing the efficiency of nuclear reactors (and other radiation based power sources, like atomic batteries), and increasing the efficiency and power density of energy transfers, so that we don't waste power while transferring it. If we can get it high enough, we may be able to transfer power to other countries around the world.
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    Quote Originally Posted by TheUnknowable View Post
    I can't find the website I read about alpha radiation firing a laser on now. I did find one about using neutrons to fire it, though, so the alpha radiation isn't that important.
    A "neutron-fired" laser makes even less sense. Provide a reference, please. It is getting progressively harder to take you seriously, as you make wild claims without any support. It really does seem -- to me, at least -- as if you're just throwing together some buzzwords you encountered in sci-fi stories and pop-sci articles. In short, I can't distinguish much of what you write from made-up nonsense. Providing citations of peer-reviewed references would go a long way toward establishing credibility.

    This thread is about increasing the efficiency of nuclear reactors ...
    Nuclear reactors are pretty efficient, actually, and are Carnot-limited (to values like 40-50%) by the boiling points of the water used in commercial designs. I don't see how anything you've talked about acknowledges this fact, let alone addresses it.


    ...(and other radiation based power sources, like atomic batteries),
    Atomic batteries are indeed pathetically inefficient. But I'm mystified as to why you would introduce lasers into the discussion at all, if effiiciency were the problem you are really trying to solve. What property of lasers makes you think that efficiency of atomic batteries would be improved by using a laser? And do you include RTGs in your working definition of atomic "battery?"


    ...and increasing the efficiency and power density of energy transfers, so that we don't waste power while transferring it. If we can get it high enough, we may be able to transfer power to other countries around the world.
    If you are working your way toward proposing the use of lasers to beam power over long distances, I invite you to present your calculations of projected efficiency. Compare with competing alternatives (e.g., local generation of power; solar-powered microwave emitters in orbit; etc.).
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    http://en.wikipedia.org/wiki/Nuclear_pumped_laser
    Says they use both neutrons and alpha particles

    Patent US4091336 - Direct nuclear pumped laser - Google Patents
    Patent for one

    I thought that if you converted the energy of the radiation into light at a set frequency (or narrow range), the light could then be converted using PV cells built to absorb that frequency. Lasers convert a range of frequencies into one frequency.
    RTGs are pathetically inefficient atomic batteries, but they are about the best that exist (maybe 8% efficient).

    Question #2 (which no one has said anything about yet) covered using it to transfer power.
    Last edited by TheUnknowable; July 30th, 2013 at 07:51 PM.
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    Quote Originally Posted by TheUnknowable View Post
    http://en.wikipedia.org/wiki/Nuclear_pumped_laser\
    Says they use both neutrons and alpha particles
    That link leads to a "no such article" notice when I click on it.

    Patents don't constitute a peer-reviewed reference. Too many patented ideas don't actually work.

    I thought that if you converted the energy of the radiation into light at a set frequency (or narrow range), the light could then be converted using PV cells built to absorb that frequency.
    The problem is much broader than simply one of absorption. Efficiency isn't so much about absorption as it is about not converting it into waste heat before you can do something with it. If you blast a silicon PV cell with x-rays, there will be plenty of absorption, but you won't get much output power. You will, however, get a damaged cell.

    Lasers convert a range of frequencies into one frequency.
    It's not the "one frequency" part that matters. For a PV cell, there is a sweet range of wavelengths over which efficiency is high. A pure, monochromatic source is not a strict requirement.

    RTGs are pathetically inefficient atomic batteries, but they are about the best that exist (maybe 8% efficient).
    Still, as pathetic as they are, their efficiency is within a factor of two or three of PV cells. And if you illuminate PV cells with x-rays or gamma rays, RTGs will win handily in any comparison.

    Question #2 (which no one has said anything about yet) covered using it to transfer power.
    I did in fact bring it up. I asked you to present your calculations.
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    Quote Originally Posted by tk421 View Post
    Quote Originally Posted by TheUnknowable View Post
    http://en.wikipedia.org/wiki/Nuclear_pumped_laser\
    Says they use both neutrons and alpha particles
    That link leads to a "no such article" notice when I click on it.

    Patents don't constitute a peer-reviewed reference. Too many patented ideas don't actually work.

    I thought that if you converted the energy of the radiation into light at a set frequency (or narrow range), the light could then be converted using PV cells built to absorb that frequency.
    The problem is much broader than simply one of absorption. Efficiency isn't so much about absorption as it is about not converting it into waste heat before you can do something with it. If you blast a silicon PV cell with x-rays, there will be plenty of absorption, but you won't get much output voltage. You will, however, get a damaged cell.

    Lasers convert a range of frequencies into one frequency.
    It's not the "one frequency" part that matters. For a PV cell, there is a sweet range of wavelengths over which efficiency is high. A pure, monochromatic source is not a strict requirement.

    RTGs are pathetically inefficient atomic batteries, but they are about the best that exist (maybe 8% efficient).
    Still, as pathetic as they are, their efficiency is within a factor of two or three of PV cells. And if you illuminate PV cells with x-rays or gamma rays, RTGs will win handily in any comparison.

    Question #2 (which no one has said anything about yet) covered using it to transfer power.
    I did in fact bring it up. I asked you to present your calculations.
    1) delete the \ that somehow got there. I fixed the post.
    2) ok
    3) But converting the radiation into electricity, instead of into heat, then electricity, like a standard reactor, could increase the efficiency. This is my idea on how to do that. If you have a better idea on how to convert energy from alpha, beta, gamma, or neutron radiation into electricity, then post it, and we will discuss it instead.
    4) A range would work, but I don't know of a device that can efficiently convert one wavelength (at least one at that high of a frequency) into another, or one range into another range (at that energy level). I wasn't sure if lasers would work. Theoretically, I suppose an ultra fine wire mesh could do it (if it works how I think it does, and will "short out" the waves like a peice of aluminum foil in the microwave), but you'd need nanites to build it.
    5) Which is why I'm trying to adjust the frequency of the photons.
    6) No calculations yet, I was just wondering if anyone else thought it would work. I've seen laser emmiters that were up to 65% efficient. It appears that loss per kilometer is also pretty high (on a logarythmic scale in which 99% signal loss was described as -20db, the best cable on the list I found was .22db loss per Km and .01 per splice). No idea how efficient a PV cell could convert it back into electricity. Transformers used in power lines is around 98% efficient.
    With those stats, it looks like the only use for it would be short, intense, power transfer (maybe on the order of TW) as line loss of wire would be extremely high even for a million volt transfer.
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    Quote Originally Posted by TheUnknowable View Post
    1) delete the \ that somehow got there. I fixed the post.
    Thanks -- that helps quite a bit. The article is mainly about the "Star Wars" x-ray laser I've already mentioned. First, it never worked (as the Wiki article mentions, the researchers were accused of falsifying the data). Even if it had worked according to expectation, the efficiency would have been well below 1%. The measured efficiency could well have been zero, depending on how you read the (very noisy) data.

    The article also confused by mentioning neutrons and alphas, sort of in the context of a He-Ar system. Neither neutrons nor alphas are actually involved in the lasing.

    3) But converting the radiation into electricity, instead of into heat, then electricity, like a standard reactor, could increase the efficiency. This is my idea on how to do that. If you have a better idea on how to convert energy from alpha, beta, gamma, or neutron radiation into electricity, then post it, and we will discuss it instead.
    The reason current practice is...current practice, is that the alternatives all have more serious problems. Nuclear to heat to steam to electricity actually works pretty well. A Carnot efficiency of 50% is not to be sneezed at. Note that there's only a factor of two improvement that one could even hope to achieve.

    Your idea, to the extent I'm able to discern it, is to convert gammas into lower-frequency photons, then use those lower-frequency photons to illuminate a PV cell. That last step alone has a worse efficiency than the total efficiency of a conventional fission plant. The world's record for a PV cell in the laboratory is below 50%. The PV cells currently on the market have efficiencies of below 20% under the best of circumstances, and degrade over time.

    Next, conversion of gammas into visible light, e.g., is even more inefficient. There are various types, but scintillators are perhaps sufficiently representative to give you a rough idea. In approximate numbers, they're perhaps 10% efficient.

    Finally -- and this is fatal -- most of the energy coming from a nuclear reaction isn't in the form of gammas. You haven't been specific about the particular reaction you've been thinking of, so I'm forced to make assumptions. A typical fission reactor gives off only a tiny amount of energy in the form of gammas. The number I remember for uranium reactors is south of 10% (the number 6% sticks in my mind, but you should check that). That number is too small to give you hope of superiority over a standard reactor. It's large enough to worry about in the design of shielding, but that's about it.

    Multiply all the efficiencies together and you get nothing. That's the problem.

    4) A range would work, but I don't know of a device that can efficiently convert one wavelength (at least one at that high of a frequency) into another, or one range into another range (at that energy level). I wasn't sure if lasers would work. Theoretically, I suppose an ultra fine wire mesh could do it (if it works how I think it does, and will "short out" the waves like a peice of aluminum foil in the microwave), but you'd need nanites to build it.
    Wire mesh? Huh? To get a frequency conversion requires either a nonlinearity or a time-varying structure. You've mentioned nothing about how a wire mesh would satisfy either requirement. But no matter; frequency conversion is a fundamentally inefficient process. The Manley-Rowe relations from the theory of nonlinear optics deliver bad news for anyone trying to implement wavelength converters. The efficiencies are terrible.

    5) Which is why I'm trying to adjust the frequency of the photons.
    As noted above, that merely replaces one bad problem with another.

    6) No calculations yet, I was just wondering if anyone else thought it would work. I've seen laser emmiters that were up to 65% efficient.
    Sure. But again, you have to multiply that 0.65 by all the other sub-unity factors in the system.

    It appears that loss per kilometer is also pretty high (on a logarythmic scale in which 99% signal loss was described as -20db, the best cable on the list I found was .22db loss per Km and .01 per splice).
    I'm not sure what "list" you are referring to, but that value seems to be for a very good optical fiber operating at the magic wavelength of 1.55um, not copper. Or maybe that's a DC value of some gigantic copper cable?

    No idea how efficient a PV cell could convert it back into electricity.
    As I mention above, you should assume values in the neighborhood of 10-20% if you wish to be realistic.

    Transformers used in power lines is around 98% efficient.
    That sounds about right.

    With those stats, it looks like the only use for it would be short, intense, power transfer (maybe on the order of TW) as line loss of wire would be extremely high even for a million volt transfer.
    I don't know what "it" you're referring to. The optical part doesn't have a voltage.

    In any case, I think you've gotten answers to all of your questions. In brief, lasers offer no advantage (and only large disadvantages) as far as efficiency is concerned. Converting gammas into a longer-wavelength emission will have lousy efficiency, which ultimately is irrelevant because gammas don't dominate the energy output of the common nuclear reactions (you never specified what your assumptions were). Space-borne lasers powered by photovoltaics might be a practical way to deliver power to remote parts of the world, but efficiency won't be the motivating factor.
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    PV cells have such a low operating efficiency because they absorb so little of the sun's spectrum. If you limit it to a narrow range of frequencies, the efficiencies increase drastically.

    Absorption Coefficient | PVEducation

    Many CPV systems (which convert light at several hundred suns in intensity) can have efficiencies of 34% or more. Some theoretical ones have even better ratings.
    Low material methods and high efficiency to push CPV demand | PV Insider
    Sharp Hits Record 44.4% Efficiency for Triple-Junction Solar Cell : Greentech Media
    These are more realistic, as the intensity of the "light" will likely be much higher than a few suns.
    CPVs are more efficient because they absorb more of the spectrum.
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    Quote Originally Posted by TheUnknowable View Post
    PV cells have such a low operating efficiency because they absorb so little of the sun's spectrum. If you limit it to a narrow range of frequencies, the efficiencies increase drastically.
    Actually, PV cells do a damn fine job of absorbing the bulk of the sun's spectrum (the plot you show is a semi-log plot).

    But that doesn't really matter very much, does it? You can't just assume that we can convert a broadband spectrum into a monochromatic one at 100% efficiency.

    You have to acknowledge practical constraints if you want to accomplish real things. I've articulated the problem statement for you as well and as realistically as I can. You can't just wave away the hard bits. Unless you have a credible way to overcome the challenges I've identified for you, there's not much to do.

    Wishing only gets you so far. I wish it were otherwise.
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    Yes, I know there are problems. I was just showing that PV cell efficiency wasn't a major one.

    Maybe letting the plasma heat up would work better. Then it would radiate IR light or visible light. You could then design a PV cell to work with it instead of trying to adjust the frequency of the light to work with the PV cell. It wouldn't be as efficient as the present "steam" system, but it's better. and it would work on the small scale like an RTG, as there are moving parts to deal with.

    Is there a way to convert plasma into electricity since it is ionized already? Or would it require you to separate the positive and negative ions (maybe with magnets) and connect them via metal plates and a circuit?
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    Quote Originally Posted by TheUnknowable View Post
    Yes, I know there are problems. I was just showing that PV cell efficiency wasn't a major one.
    It's odd that you would propose a solution to what you now acknowledge is not a major problem. That's what I was pointing out. Glad you now seem to agree that improving absorption in a PV cell wouldn't alter things in any significant way here.

    Maybe letting the plasma heat up would work better. Then it would radiate IR light or visible light. You could then design a PV cell to work with it instead of trying to adjust the frequency of the light to work with the PV cell. It wouldn't be as efficient as the present "steam" system, but it's better. and it would work on the small scale like an RTG, as there are moving parts to deal with.

    Is there a way to convert plasma into electricity since it is ionized already? Or would it require you to separate the positive and negative ions (maybe with magnets) and connect them via metal plates and a circuit?
    I see that this conversation is in danger of never terminating. I'm afraid that I'll have to resort to recommending that you first learn enoujgh physics to the point where you can perform actual calculations yourself. Otherwise, you'll just chase after one sci-fi idea after another. To constrain the search space, you can't avoid performing actual calculations.

    Here are a few things you'd need to calculate: How much light would you expect from a plasma? What percentage of that light could you expect to convert to electricity? How much energy would it take for you to separate charges in a plasma, with or without a magnet? Etc. When all is said and done, how do the total efficiency numbers compare with that of technologies already in use?

    Things like that.
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    ok, just trying to get an opinion. I'll have to look into it.
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    Quote Originally Posted by TheUnknowable View Post
    http://en.wikipedia.org/wiki/Nuclear_pumped_laser
    Says they use both neutrons and alpha particles

    Patent US4091336 - Direct nuclear pumped laser - Google Patents
    Patent for one

    I thought that if you converted the energy of the radiation into light at a set frequency (or narrow range), the light could then be converted using PV cells built to absorb that frequency. Lasers convert a range of frequencies into one frequency.
    RTGs are pathetically inefficient atomic batteries, but they are about the best that exist (maybe 8% efficient).

    Question #2 (which no one has said anything about yet) covered using it to transfer power.
    Thanks very much for the patent reference. I had no idea this was possible.

    From a cursory 1st reading, it looks as if what this device does is to use ionising radiation to ionise the major component of a 2 gas mixture, and have these ions collisionally activate (i.e. without ionising them) dissociated atoms of the minor component gas (nitrogen). Some of this activation would be to an energy level from which laser action can occur in a correctly set up laser cavity. Clever - if it works.

    However it rather looks as if the concern was to get a low weight power source for space use. Efficiency would barely come into the picture in such a case. As tk421 explains elsewhere on this thread, if you then convert light from this laser action photovoltaically, the low efficiencies of the various steps have to be multiplied, almost certainly leading to a very, very inefficient way to extract power from radioactivity.

    It's interesting, actually, that although one instinctively tends to feel the Carnot efficiency limitations of a heat engine should make other forms of energy conversion more attractive, when you come to look at the practicalities of those conversion processes, Carnot efficiency comes out pretty well!
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    At this point, I'm more interested in making a small, light reactor. The efficiency of RTGs are so low that it should be much easier to improve on it than on a 40% efficient large reactor.
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    Quote Originally Posted by TheUnknowable View Post
    At this point, I'm more interested in making a small, light reactor. The efficiency of RTGs are so low that it should be much easier to improve on it than on a 40% efficient large reactor.
    Hmm. I see from Wiki that RTGs have conversion efficiency from about 5 to 20%. I rather doubt this multi-step, ionisation/collisional activation & laser/photovoltaic setup will get anywhere near this, merely from the number of low efficiency steps, the efficiency of each of which has to be multiplied. 10% of 10% of 10% is 0.1% - and my guess would be that the first 2 steps will actually convert <10% of the energy input into the required form for the next.
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