I'm trying to do some 'homework' regarding my 'half baked' theories on virtually eliminating neutrals from within the chamber.
I'm wondering if anyone can point me to a source where I can research the energy levels (velocities) of neutrals within the chamber.
I've read numerous posts that mention 'slow neutrals' (ie 'collisions with slow neutrals') but can find no references anywhere that quote the energy levels of these neutrals.
I don't just require 'average energy levels' or 'average velocities' but precise figures.
A graph depicting the distribution curve of velocities of neutrals would be ideal.
I appreciate there may well be other factors that come into play, but if anyone can point me to a suitable reference it would help a lot.
Thanks.
Help required re speeds/energies of neutrals within the chamber
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Linda Haile
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Re: Help required re speeds/energies of neutrals within the chamber
From the trusted wikipedia
http://en.wikipedia.org/wiki/Electron_volt
under heading
As a unit of temperature.
This describes the energy of particles at a temperature.
You measure your chamber temperature - convert to kelvin - devide by 11604
to give velocity in electron volts (roughly 0.025ev at 30c).
This will only describe the mean with no electric fields, but i guess this may represent a good percentage of the population.
The rest could be up to your applied voltage via charge exchange, depending on vacuum / mean free path , topology, ion current, electron current etc etc..
Steve.
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Linda Haile
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Re: Help required re speeds/energies of neutrals within the chamber
I appreciate that this may well have some relevance, however, my first thoughts are that this formula will give the average energy level of all particles within the chamber.
IE 'slow moving neutrals' will have much lower energies on average than 'fast ions'.
I have seen this article before, but thanks for the link.
IE 'slow moving neutrals' will have much lower energies on average than 'fast ions'.
I have seen this article before, but thanks for the link.
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John Futter
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Re: Help required re speeds/energies of neutrals within the chamber
Lyn
so why have any there at all??
This is exactly what we do at work in our ion implanters
Target chamber about 0.5 gallon of it in volume runs at a pressure of 2 x ten to the minus 8 millibar ie mean free path of many tens of meters.
to attain this the ion source is remote and @ 90 degrees to the chamber and only the right ions are selected to go round the mass selection magnet ie in this case D+ not D2+ and the beam line is differentially pumped to get from around a millitorr in the ion source to the vac quoted in the target chamber.
Nobody so far as I have seen has mass selected and removed neutrals / other ions and run 2 beams head on into each other.
The nearest to this has been Steven with the Star reactor but in this case no mass selection and D2+ and D+ are present in his beam plus of course a whole lot of neutrals not necessarily a cousin of hydrogen including D and T ie H2O and whatever Steven a couple of Wein filters would help.
I have been slowly putting kit together to attempt two D+ beams (D+only) head on with as few neutrals as possible in the flight path /collision zone.
electron suppression around the target area is a must to limit stray neutrals being given charge to queer the pitch.
Fully understand what this means before your next left field idea ---things may start to gel --and go on
so why have any there at all??
This is exactly what we do at work in our ion implanters
Target chamber about 0.5 gallon of it in volume runs at a pressure of 2 x ten to the minus 8 millibar ie mean free path of many tens of meters.
to attain this the ion source is remote and @ 90 degrees to the chamber and only the right ions are selected to go round the mass selection magnet ie in this case D+ not D2+ and the beam line is differentially pumped to get from around a millitorr in the ion source to the vac quoted in the target chamber.
Nobody so far as I have seen has mass selected and removed neutrals / other ions and run 2 beams head on into each other.
The nearest to this has been Steven with the Star reactor but in this case no mass selection and D2+ and D+ are present in his beam plus of course a whole lot of neutrals not necessarily a cousin of hydrogen including D and T ie H2O and whatever Steven a couple of Wein filters would help.
I have been slowly putting kit together to attempt two D+ beams (D+only) head on with as few neutrals as possible in the flight path /collision zone.
electron suppression around the target area is a must to limit stray neutrals being given charge to queer the pitch.
Fully understand what this means before your next left field idea ---things may start to gel --and go on
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Linda Haile
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Re: Help required re speeds/energies of neutrals within the chamber
John, Thanks for your comments, however, I have not mentioned mass selection of neutrals and I do not intend to use mass selection.
Also, I will not be running two beams head on.
I understand that fusion rate will be a function of current squared in a conventional fusor if all collisions are fast ion on fast ion.
The design I am working on will not completely eliminate neutrals but should, in theory, eliminate the vast majority.
There has been much said in the past regarding the fact that most collisions in a fusor are fast ion on slow neutral.
I merely wish to build a device where the majority of collisions are fast ion on fast ion.
The design allows for the fusor to be run in both modes of operation, thus allowing one to compare fusion rates when the majority of collisions are fast on slow with fusion rates when the majority of collisions are fast on fast.
I can not eliminate all neutrals without vaporizing the inner grid, but believe I can remove the vast majority
I also believe I have a workable design that will achieve this.
Also, I will not be running two beams head on.
I understand that fusion rate will be a function of current squared in a conventional fusor if all collisions are fast ion on fast ion.
The design I am working on will not completely eliminate neutrals but should, in theory, eliminate the vast majority.
There has been much said in the past regarding the fact that most collisions in a fusor are fast ion on slow neutral.
I merely wish to build a device where the majority of collisions are fast ion on fast ion.
The design allows for the fusor to be run in both modes of operation, thus allowing one to compare fusion rates when the majority of collisions are fast on slow with fusion rates when the majority of collisions are fast on fast.
I can not eliminate all neutrals without vaporizing the inner grid, but believe I can remove the vast majority
I also believe I have a workable design that will achieve this.
Re: Help required re speeds/energies of neutrals within the chamber
Been reading the thread with interest (and I am glad you are trying a novel approch) - but I am confused - you can not remove a neutral using a magnetic field nor electric field - it is neutral so these fields will have no effect - so I am lost how you will 'remove' these neutral particles .
Of course any very high vacuum system that uses ion guns to feed in the required 'non-neutrals' to create your plasma can be used to create such a system. But this state would exist for only very short time periods.
But the price you will pay for a ultra-high vacuum is that the probability of interaction between these nearly ‘pure’ ions will be far worse than that of a standard fusor (neutrals can undergo fusion too, when hit hard enough by ions) - also, if you suppress the number of electrons near the protons, then electric field shielding of the charges will be lessoned, and the probability of fusion collisions will drop even further.
Without giving away your main idea, I was wondering if you might address this issue?
Of course any very high vacuum system that uses ion guns to feed in the required 'non-neutrals' to create your plasma can be used to create such a system. But this state would exist for only very short time periods.
But the price you will pay for a ultra-high vacuum is that the probability of interaction between these nearly ‘pure’ ions will be far worse than that of a standard fusor (neutrals can undergo fusion too, when hit hard enough by ions) - also, if you suppress the number of electrons near the protons, then electric field shielding of the charges will be lessoned, and the probability of fusion collisions will drop even further.
Without giving away your main idea, I was wondering if you might address this issue?
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Linda Haile
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Re: Help required re speeds/energies of neutrals within the chamber
Dennis, this is very much 'work in progress'. I'm working through the theory and finding problems all the time, which I then try to 'design out'.
In it's latest form (number six, I think) I will not be able to eliminate all neutrals from the chamber. (previous designs would have resulted in vaporization of the inner grid, among other problems)
Before posting details and diagrams of my current proposed design, I'd appreciate some advice on the distribution of neutrals within a conventional fusor at normal operating pressures.
I assume no-one has actually measured this, so it will presumably be speculative theory.
In it's latest form (number six, I think) I will not be able to eliminate all neutrals from the chamber. (previous designs would have resulted in vaporization of the inner grid, among other problems)
Before posting details and diagrams of my current proposed design, I'd appreciate some advice on the distribution of neutrals within a conventional fusor at normal operating pressures.
I assume no-one has actually measured this, so it will presumably be speculative theory.
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Doug Coulter
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Re: Help required re speeds/energies of neutrals within the chamber
http://www.coultersmithing.com/forums/v ... f=26&t=114
Vacuum pump removes neutrals in that design, while ions are trapped via their own fields.
As John says, you might simply measure temperature with an insulated (or for that matter, charged repulsively compared to whatever) thermocouple that doesn't attract the ions at a distance and infer quite a lot from that.
Particularly with different net fields on the temp probe and moving it around in there.
You're going to find that the models and simulations don't account for quite a lot of stuff that actually happens -- which is obvious only in hindsight.
It might be time to get off the theory and paper junk and actually try some stuff you can report on.
Experience here says you learn faster that way -- much. Most theories oversimplify what really happens, particularly those from authors who don't do experiments.
I almost bought SIMION myself, but after a conversation with them about what I really wanted to model, they said "don't waste your money, it won't model that well" -- nice of them. The thing is, evidently a lot of people didn't get that word and believe what it says under conditions the company themselves don't think their code works for.
Vacuum pump removes neutrals in that design, while ions are trapped via their own fields.
As John says, you might simply measure temperature with an insulated (or for that matter, charged repulsively compared to whatever) thermocouple that doesn't attract the ions at a distance and infer quite a lot from that.
Particularly with different net fields on the temp probe and moving it around in there.
You're going to find that the models and simulations don't account for quite a lot of stuff that actually happens -- which is obvious only in hindsight.
It might be time to get off the theory and paper junk and actually try some stuff you can report on.
Experience here says you learn faster that way -- much. Most theories oversimplify what really happens, particularly those from authors who don't do experiments.
I almost bought SIMION myself, but after a conversation with them about what I really wanted to model, they said "don't waste your money, it won't model that well" -- nice of them. The thing is, evidently a lot of people didn't get that word and believe what it says under conditions the company themselves don't think their code works for.
Why guess when you can know? Measure!
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Richard Hull
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Re: Help required re speeds/energies of neutrals within the chamber
Lyn,
Speed and energy are the same card for the neutrals more or less as they tend to have the same mass. The energy is anywhere from 1 electron volt (1eV) to just under the applied voltage ~ 35,000 eV (35keV). In short, they are all over the place, from creepers (relatively rare) to the highest energy (exceedingly rare). The slowest and lowest energy neutral (1eV) is moving at about 10 times faster than the speed of a high power rifle bullet, (a few miles per second). So, basically every thing is moving much, much faster than this.... (hundreds or thousands of miles every second.)
Yep, they're all, every one of 'em, zippin' right along. Thus, even the creepers cross the entire chamber in 10 millionths of one second. A tiny bit of simple math will allow for precise velocity calcs if you plug in an energy value and the mass of the neutral.
Ke= 1/2 mv ^2 is what you need.... And now the hated phrase from the text book......."The exact value of velocity for a range of energetic particles is left as an exercise for the student". We all have to suck it up and plod through even the simplest math. In doing that, we learn about units, conversions, etc. It's a nasty biz for the dilettante, but must be endured or the dilettante becomes a blind dabbler.
No matter what, even if you elimenate 100% of the neutrals and load the chamber with pure ions and succeed by some miracle to get all 100% of those D ions at fusion energy, only a tiny, microscopic fraction will fuse. You are still at the mercy of the very low probabalistic cross section for fusion. Finally, you still have electron loses and a large number of other losses as well. Doing all this on a watt spent for watt return basis is and will remain a dream for quite a while.
Like Doug, John and others note. It might be well to actually do a bit of fusion and get some experience under your belt. You may hate math, but math is the key to learning just how lousy a job you are doing and to see how many light years you are away from home plate, once you actually do some fusion that you can prove.
I have a bumper sticker over my lab door, it reads; "Research is what I am doing when I don't know what I am doing". The humor is obvious, but sadly, that is the way a lot of amateurs plod through things. They often spend both treasure and much of life's fleeting moments spinning wheels in lost or erudite causes which is their option, of course. However, spending some of those life moments in learning, at some usable base level, facts in the field of endeavor is time far better spent.
Science done without a good helping of math is like building a fabulous car without a motor. It is doomed to never go anywhere inspite of a lot of money and effort spent on the body, frame, and interior. Math helps mechanize science.
We all have to wish you luck, but most here realize that we will never see actual wheelwork from any of the ideas espoused. You do need some serious backgrounding in this fusion business. This is not to let you know what can't be done, but to let you just know what has been done and why it failed.
The fusor has not failed in a unity quest due to just a huge number of worthless neutrals, or just a lot of useless lower energy ions present, or due to electron losses, or wall based ion losses or the horridly low probabilty of fusion at the core of it, the fusor fails to hit unity because of all of them and much, much more.
Richard Hull
Speed and energy are the same card for the neutrals more or less as they tend to have the same mass. The energy is anywhere from 1 electron volt (1eV) to just under the applied voltage ~ 35,000 eV (35keV). In short, they are all over the place, from creepers (relatively rare) to the highest energy (exceedingly rare). The slowest and lowest energy neutral (1eV) is moving at about 10 times faster than the speed of a high power rifle bullet, (a few miles per second). So, basically every thing is moving much, much faster than this.... (hundreds or thousands of miles every second.)
Yep, they're all, every one of 'em, zippin' right along. Thus, even the creepers cross the entire chamber in 10 millionths of one second. A tiny bit of simple math will allow for precise velocity calcs if you plug in an energy value and the mass of the neutral.
Ke= 1/2 mv ^2 is what you need.... And now the hated phrase from the text book......."The exact value of velocity for a range of energetic particles is left as an exercise for the student". We all have to suck it up and plod through even the simplest math. In doing that, we learn about units, conversions, etc. It's a nasty biz for the dilettante, but must be endured or the dilettante becomes a blind dabbler.
No matter what, even if you elimenate 100% of the neutrals and load the chamber with pure ions and succeed by some miracle to get all 100% of those D ions at fusion energy, only a tiny, microscopic fraction will fuse. You are still at the mercy of the very low probabalistic cross section for fusion. Finally, you still have electron loses and a large number of other losses as well. Doing all this on a watt spent for watt return basis is and will remain a dream for quite a while.
Like Doug, John and others note. It might be well to actually do a bit of fusion and get some experience under your belt. You may hate math, but math is the key to learning just how lousy a job you are doing and to see how many light years you are away from home plate, once you actually do some fusion that you can prove.
I have a bumper sticker over my lab door, it reads; "Research is what I am doing when I don't know what I am doing". The humor is obvious, but sadly, that is the way a lot of amateurs plod through things. They often spend both treasure and much of life's fleeting moments spinning wheels in lost or erudite causes which is their option, of course. However, spending some of those life moments in learning, at some usable base level, facts in the field of endeavor is time far better spent.
Science done without a good helping of math is like building a fabulous car without a motor. It is doomed to never go anywhere inspite of a lot of money and effort spent on the body, frame, and interior. Math helps mechanize science.
We all have to wish you luck, but most here realize that we will never see actual wheelwork from any of the ideas espoused. You do need some serious backgrounding in this fusion business. This is not to let you know what can't be done, but to let you just know what has been done and why it failed.
The fusor has not failed in a unity quest due to just a huge number of worthless neutrals, or just a lot of useless lower energy ions present, or due to electron losses, or wall based ion losses or the horridly low probabilty of fusion at the core of it, the fusor fails to hit unity because of all of them and much, much more.
Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Re: Help required re speeds/energies of neutrals within the chamber
Dennis is correct.
When the mean free path is greater than the length of the chamber,
almost all neutral interactions are with the walls.
Cover all the walls with turbo's and you can remove (almost) all the neutrals.
But I feel this will just empty your pocket for no net gain.
Who knows, the neutral / ion collisions may be a larger fraction of fusion events.
Beam on loaded target being a good example.
Steve.
When the mean free path is greater than the length of the chamber,
almost all neutral interactions are with the walls.
Cover all the walls with turbo's and you can remove (almost) all the neutrals.
But I feel this will just empty your pocket for no net gain.
Who knows, the neutral / ion collisions may be a larger fraction of fusion events.
Beam on loaded target being a good example.
Steve.
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Chris Bradley
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Re: Help required re speeds/energies of neutrals within the chamber
Richard,
This is an excellent, solid, answer to a rather nebulous posing of an unanswerable question with little background associated with it. I rather think that you've given, here, more than the question deserved, but the reason I want to comment is because if this forum continues to witness such replies to other similarly 'provisional' questions, without it getting all caught up with angst and complaint, then I think it paints a prettier picture for the forum's future than the testy interchanges of late where replies have not been as 'constructive'.
In the 'Are we it?' thread, I said that this place is special because left-fielded ideas get a reasonable airing. I am no longer convinced that this is entirely true, but yours was the type of reply I had in mind when I wrote that comment in 'Are we it?'.
I think this thread should be considered a 'model' for how the forum should respond to insubstantial 'ideas', if it is to encourage 'the 4th fusor generation'.
Lyn,
Some homework on Maxwellian distributions [ http://en.wikipedia.org/wiki/Maxwell%E2 ... stribution ] and atomic collision charge-exchange mechanisms will serve you well in regards your question. I think that if you come to know and understand these two things then you'll probably be able to answer your question for yourself better than others. I also came across this item, which may have some words/methodology of interest in it for you; http://www.chm.bris.ac.uk/pt/diamond/pa ... HPIEDs.pdf .
(If you don't like the maths in these, then that's too bad as it is about as simple an explanation as you are going to find. Some things just aren't so easy to follow, and that's why it is called 'an advanced science'. If it was easy, someone would've done it all long ago. You need to 'expect the pain' and you'll not be able to progress if you sit back and say you're no mathematician. You have to learn to be so, if you are not.)
Now that the forum has come good on answering you, can you please explain [given the presumption that this is an open-source site] what efficiency you would expect if you have pure ion-ion beams coming together? Are you thinking that this will somehow be 100% efficient, or is there more to your idea you need to share for it to make sense?
This is an excellent, solid, answer to a rather nebulous posing of an unanswerable question with little background associated with it. I rather think that you've given, here, more than the question deserved, but the reason I want to comment is because if this forum continues to witness such replies to other similarly 'provisional' questions, without it getting all caught up with angst and complaint, then I think it paints a prettier picture for the forum's future than the testy interchanges of late where replies have not been as 'constructive'.
In the 'Are we it?' thread, I said that this place is special because left-fielded ideas get a reasonable airing. I am no longer convinced that this is entirely true, but yours was the type of reply I had in mind when I wrote that comment in 'Are we it?'.
I think this thread should be considered a 'model' for how the forum should respond to insubstantial 'ideas', if it is to encourage 'the 4th fusor generation'.
Lyn,
Some homework on Maxwellian distributions [ http://en.wikipedia.org/wiki/Maxwell%E2 ... stribution ] and atomic collision charge-exchange mechanisms will serve you well in regards your question. I think that if you come to know and understand these two things then you'll probably be able to answer your question for yourself better than others. I also came across this item, which may have some words/methodology of interest in it for you; http://www.chm.bris.ac.uk/pt/diamond/pa ... HPIEDs.pdf .
(If you don't like the maths in these, then that's too bad as it is about as simple an explanation as you are going to find. Some things just aren't so easy to follow, and that's why it is called 'an advanced science'. If it was easy, someone would've done it all long ago. You need to 'expect the pain' and you'll not be able to progress if you sit back and say you're no mathematician. You have to learn to be so, if you are not.)
Now that the forum has come good on answering you, can you please explain [given the presumption that this is an open-source site] what efficiency you would expect if you have pure ion-ion beams coming together? Are you thinking that this will somehow be 100% efficient, or is there more to your idea you need to share for it to make sense?
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Linda Haile
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Re: Help required re speeds/energies of neutrals within the chamber
Thanks Doug Richard and Chris for your input. I'll try to address the points you raise.
Doug, I agree with the points you make regarding SIMION. I am, however, trying to keep my explanations below as simple as possible in the hope that more people will get the gist of what I'm trying to do. To this end some of it will be oversimplified.
I think it has already been suggested that your own results with contaminants in the chamber leading to an 'unexplained' increase in fusion events can be most easily explained by the fact that these heavier (more energetic) ions will collide with neutrals, ionize them, and that this will increase the ratio of ions to neutrals which will result in higher rates of fusion.
Richard, I'm sure you'll agree that good science involves designing an experiment to test a hypothesis and then analysing the results to determine whether or not they support the original hypothesis.
The hypothesis I wish to test is that an increased ratio of ions to neutrals will lead to an increase in fusion rates. It has previously been agreed by Carl, Chris and others that the maths supports this hypothesis.
I'd argue that Doug's results also support this. (see above)
Chris, One reason why I'm posting these ideas before they are complete is as an example to demonstrate how the forum can encourage development of fourth generation fusors.
I am familiar with basic kinetic theory of gases and Brownian motion, etc.
Thanks for the links, the second one certainly looks worth 'wading through' in depth later.
From the replies I've received, it appears that I can assume that neutrals will, in a normal fusor, reach the chamber walls and then bounce back. My current idea relies on this assumption.
The maths upon which my theory is based Chris, is from an old thread I came across which it appears that both you and Carl agreed could be the case if there were no neutrals in the chamber, ie if all collisions are fast ion on fast ion, (at least, that is how I read the gist of it) and is
“ the probability of fusion occuring between two fast moving ions may well be a function of ((I^2)-I)/2”
I'm merely trying to test this hypothesis. (After reading Doug's results I came to the conclusion that eliminating neutrals could lead to increased fusion rates, and then set out to do some research on this)
I will post a description of my proposed device and how I arrived at the present design in a new thread, but I'm presently unsure which forum I should post it in. Can anyone tell me which is the best forum to post proposed designs of fourth generation fusors in please?
Doug, I agree with the points you make regarding SIMION. I am, however, trying to keep my explanations below as simple as possible in the hope that more people will get the gist of what I'm trying to do. To this end some of it will be oversimplified.
I think it has already been suggested that your own results with contaminants in the chamber leading to an 'unexplained' increase in fusion events can be most easily explained by the fact that these heavier (more energetic) ions will collide with neutrals, ionize them, and that this will increase the ratio of ions to neutrals which will result in higher rates of fusion.
Richard, I'm sure you'll agree that good science involves designing an experiment to test a hypothesis and then analysing the results to determine whether or not they support the original hypothesis.
The hypothesis I wish to test is that an increased ratio of ions to neutrals will lead to an increase in fusion rates. It has previously been agreed by Carl, Chris and others that the maths supports this hypothesis.
I'd argue that Doug's results also support this. (see above)
Chris, One reason why I'm posting these ideas before they are complete is as an example to demonstrate how the forum can encourage development of fourth generation fusors.
I am familiar with basic kinetic theory of gases and Brownian motion, etc.
Thanks for the links, the second one certainly looks worth 'wading through' in depth later.
From the replies I've received, it appears that I can assume that neutrals will, in a normal fusor, reach the chamber walls and then bounce back. My current idea relies on this assumption.
The maths upon which my theory is based Chris, is from an old thread I came across which it appears that both you and Carl agreed could be the case if there were no neutrals in the chamber, ie if all collisions are fast ion on fast ion, (at least, that is how I read the gist of it) and is
“ the probability of fusion occuring between two fast moving ions may well be a function of ((I^2)-I)/2”
I'm merely trying to test this hypothesis. (After reading Doug's results I came to the conclusion that eliminating neutrals could lead to increased fusion rates, and then set out to do some research on this)
I will post a description of my proposed device and how I arrived at the present design in a new thread, but I'm presently unsure which forum I should post it in. Can anyone tell me which is the best forum to post proposed designs of fourth generation fusors in please?
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Chris Bradley
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Re: Help required re speeds/energies of neutrals within the chamber
Lyn Haile wrote:
> The hypothesis I wish to test is that an increased ratio of ions to neutrals will lead to an increase in fusion rates. It has previously been agreed by Carl, Chris and others that the maths supports this hypothesis.
I am not aware that I have said this. Can you link me to the text from which you have made this interpretation? Sounds like it may need clarification.
> The hypothesis I wish to test is that an increased ratio of ions to neutrals will lead to an increase in fusion rates. It has previously been agreed by Carl, Chris and others that the maths supports this hypothesis.
I am not aware that I have said this. Can you link me to the text from which you have made this interpretation? Sounds like it may need clarification.
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Linda Haile
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Chris Bradley
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Re: Help required re speeds/energies of neutrals within the chamber
I wrote;
> "Of course, yes, an I^2 dependency would be best for fusion rate - if only that dream could be realised. I was thinking that that should be given heavy caveats as it gives succor to an excess of wishful thinking regarding fusors' likelihood of getting better than 1E-9 DD efficiencies, which are heavily fast-slow reaction weighted."
I have said that you may increase the fast-fast-reaction-rate-versus-current by removing neutrals, but that this doesn't mean your reaction rate goes up. The fast-neutral dominate by orders of magnitude. If you get rid of all the fast-neutral reactions then I would posit that you will then get a 100 fold increase in the fast-fast reaction rate. This'd take you from an unmeasurable reaction rate to.. er.. another unmeasurable rate.
But, hey, this is just my opinion. Do the experiment and get some experience under your belt [as has been the recommendation here] and along the way you might discover something completely different that takes you onto a new tangent.
> "Of course, yes, an I^2 dependency would be best for fusion rate - if only that dream could be realised. I was thinking that that should be given heavy caveats as it gives succor to an excess of wishful thinking regarding fusors' likelihood of getting better than 1E-9 DD efficiencies, which are heavily fast-slow reaction weighted."
I have said that you may increase the fast-fast-reaction-rate-versus-current by removing neutrals, but that this doesn't mean your reaction rate goes up. The fast-neutral dominate by orders of magnitude. If you get rid of all the fast-neutral reactions then I would posit that you will then get a 100 fold increase in the fast-fast reaction rate. This'd take you from an unmeasurable reaction rate to.. er.. another unmeasurable rate.
But, hey, this is just my opinion. Do the experiment and get some experience under your belt [as has been the recommendation here] and along the way you might discover something completely different that takes you onto a new tangent.
Re: Help required re speeds/energies of neutrals within the chamber
Not to be mean but when you say:
"From the replies I've received, it appears that I can assume that neutrals will, in a normal fusor, reach the chamber walls and then bounce back. My current idea relies on this assumption."
This type of answer scares me – you are making a statement so painfully obvious it almost makes me wonder if you are just pulling our chain and baiting us? If you are serious and believe this is insight, you are in very serious trouble with your theories and application of physics. Your knowledge of even the most simple kinetic gas theory is lacking in the extreme if you make statements like this relative to a complex process of ions/gases and electrons in a plasma contained by a high voltage electric field.
I hope I am wrong or misunderstanding your real insight but if not, you are wasting your time.
"From the replies I've received, it appears that I can assume that neutrals will, in a normal fusor, reach the chamber walls and then bounce back. My current idea relies on this assumption."
This type of answer scares me – you are making a statement so painfully obvious it almost makes me wonder if you are just pulling our chain and baiting us? If you are serious and believe this is insight, you are in very serious trouble with your theories and application of physics. Your knowledge of even the most simple kinetic gas theory is lacking in the extreme if you make statements like this relative to a complex process of ions/gases and electrons in a plasma contained by a high voltage electric field.
I hope I am wrong or misunderstanding your real insight but if not, you are wasting your time.
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Linda Haile
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Re: Help required re speeds/energies of neutrals within the chamber
Dennis, your certainty of this fact reassures me.
No-one has suggested either that most neutrals are within the inner grid and get ionized by electrostatic forces when they move outside of the inner grid. Also, no-one has suggested that neutrals can have sufficient energy to embed themselves in the chamber wall.
It appears that everyone here believes that neutrals behave the same in a fusor as they do in a normal gas.
I'm not trying to 'bait' anyone. What would be the point?
(I may be seeking reassurance that my design is based on 'good science' before I post details though, for obvious reasons.)
BTW, no-one has yet replied to my question regarding which forum people should post proposed designs for fourth generation fusors in.
No-one has suggested either that most neutrals are within the inner grid and get ionized by electrostatic forces when they move outside of the inner grid. Also, no-one has suggested that neutrals can have sufficient energy to embed themselves in the chamber wall.
It appears that everyone here believes that neutrals behave the same in a fusor as they do in a normal gas.
I'm not trying to 'bait' anyone. What would be the point?
(I may be seeking reassurance that my design is based on 'good science' before I post details though, for obvious reasons.)
BTW, no-one has yet replied to my question regarding which forum people should post proposed designs for fourth generation fusors in.
Re: Help required re speeds/energies of neutrals within the chamber
Lyn - build it and see.
Re: Help required re speeds/energies of neutrals within the chamber
Lyn, no disrespect and you are doing far better than I since you are not only building a real fusor but trying to do real world experiments on it.
I do think you are biting off more than you should with this theory work on neutrals. Kinetic theory is not applicable to plasma's or even neutrals at all with energies most fusors operate. The calculations you need are beyond those far too simple treatments (even for most real gases at normal pres/temp) and I am worried when you say you understand kinetic gas theory relative to these discussions – it is not relevant to a gases in fusors. Don't get side tracked using such simple theory for systems that require rather nasty and never easy to make more simple plasma physics (that theory is not even taught at the undergraduate physics level at all.)
As mentioned by the previous poster, just try the experiment – there is great need for that approach too. Theory can help (but incorrect or inappropriate theory will do far more harm than good) but experiments are the gold standard in all the science's. Good luck!
I do think you are biting off more than you should with this theory work on neutrals. Kinetic theory is not applicable to plasma's or even neutrals at all with energies most fusors operate. The calculations you need are beyond those far too simple treatments (even for most real gases at normal pres/temp) and I am worried when you say you understand kinetic gas theory relative to these discussions – it is not relevant to a gases in fusors. Don't get side tracked using such simple theory for systems that require rather nasty and never easy to make more simple plasma physics (that theory is not even taught at the undergraduate physics level at all.)
As mentioned by the previous poster, just try the experiment – there is great need for that approach too. Theory can help (but incorrect or inappropriate theory will do far more harm than good) but experiments are the gold standard in all the science's. Good luck!
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Linda Haile
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Re: Help required re speeds/energies of neutrals within the chamber
Dennis, all I really need to know at this point is the approximate mean free path of a neutral in an average fusor.
Are you able to answer this for me?
Are you able to answer this for me?
Re: Help required re speeds/energies of neutrals within the chamber
The free path is purely a function of the pressure - why? Because a neutral is exactly that and does not see the electric field created by the grids at all and unless an ion gets pass shielding by the free electrons in the plasma, the neutral see's little of the electric field produced by the ions that pass near. So, to very close first order, the mean free path is exactly what you find for the given pressure. I can calculate or give you that equation (yes, based on standard gas theory and assumes no ionization)
the mean free path length before a collision is x
The diameter of the atom is d
Pi is 3.14159
n* is the number of collisons occuring in a standard cc (cubic centimeter) volume!
The equation is:
x = 1/[sqr(2) Pi n* d (exp) 2 (ie d squared)]
to get n* = [(pressure in torr/760)(Vol. in cm cubed)/(molar gas const 82.05)(temp in K )] * avogadro #
For your application I guess you use the 30 KeV average for the neutrals (a big number) and 1 micron for pressure. From the wiki: temp is given by this relation: 1 eV/Boltzman const or
1.60 *10 (exp) 19 J/(1.38 10 (exp) -23 J/K) = about = 1 *10 (exp) 4 K/eV
so @ 30 KeV we just have:
3 *10 (exp) 4 eV * 1 * 10 exp 4 = 3 *10 (exp) 8 K if I didn't screw up.
Sooooo,
n* = {[(0.001)/760)(1000)]/[(82.05)(3 *10 to 8)]} * (6 *10 to 23 power) = 3.2 (exp) +10 inverse cc
So, for a distance x traveled before collision (this is hard to write on this stupid screen so check my math; also, I will just assume a 'd' of 1 A or 1 * 10 (exp) -8 cm and Pi times square root of two is the product about 4.4 ):
x = 1/[(4.4) (1 * 10 exp -8) squared * 3.2 *10 (exp) 10)] = 7.1 *10 (exp) 4 cm very approx. but unless I did a math error, should be close. Hope this helps. Considering the rather large value of the free path by neutrals and small size of chambers, the # of collisons by neutrals with the wall is a big, big number and would dominate any process by many orders of magitude.
the mean free path length before a collision is x
The diameter of the atom is d
Pi is 3.14159
n* is the number of collisons occuring in a standard cc (cubic centimeter) volume!
The equation is:
x = 1/[sqr(2) Pi n* d (exp) 2 (ie d squared)]
to get n* = [(pressure in torr/760)(Vol. in cm cubed)/(molar gas const 82.05)(temp in K )] * avogadro #
For your application I guess you use the 30 KeV average for the neutrals (a big number) and 1 micron for pressure. From the wiki: temp is given by this relation: 1 eV/Boltzman const or
1.60 *10 (exp) 19 J/(1.38 10 (exp) -23 J/K) = about = 1 *10 (exp) 4 K/eV
so @ 30 KeV we just have:
3 *10 (exp) 4 eV * 1 * 10 exp 4 = 3 *10 (exp) 8 K if I didn't screw up.
Sooooo,
n* = {[(0.001)/760)(1000)]/[(82.05)(3 *10 to 8)]} * (6 *10 to 23 power) = 3.2 (exp) +10 inverse cc
So, for a distance x traveled before collision (this is hard to write on this stupid screen so check my math; also, I will just assume a 'd' of 1 A or 1 * 10 (exp) -8 cm and Pi times square root of two is the product about 4.4 ):
x = 1/[(4.4) (1 * 10 exp -8) squared * 3.2 *10 (exp) 10)] = 7.1 *10 (exp) 4 cm very approx. but unless I did a math error, should be close. Hope this helps. Considering the rather large value of the free path by neutrals and small size of chambers, the # of collisons by neutrals with the wall is a big, big number and would dominate any process by many orders of magitude.
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Richard Hull
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Re: Help required re speeds/energies of neutrals within the chamber
A very large number of neutrals will embed in the walls.
This is not like a baseball hitting hard metal and bouncing off. These are molecules slamming into a network of metal molecules in a lattice. They will embed!
In general, the higher energy ones will embed easier and deeper. Some will embed forever. Some of the weaker embeded deuterium atoms will pop back out as the chamber heats. This process is where the term "hydrogen embrittlement" comes from in materials science and metallurgy. These molecules can slowly work their way into the metal lattice, insinuatiing themselves ever deeper with continued molecular bombardment.
It might be likened to firing grains of wheat at varying speeds at a section of deep pile carpet some will embed so deep, they will never fall out. Others will fill the shag to a lesser degree and some already lightly stuck will be knocked out by an incoming grain. Ultimately the outer regions of the carpet will become clogged with wheat grains and will have zero energy embeded grains pop out on an almost one to one correspondence with incoming grains but with only a fraction of the energy. The lost energy being used to hammer lower grains ever deeper into the shag. The probability of complete bounce off by a specific incoming grain are very low while the probability of the "loaded surface" popping another molecule of deuterium out at greatly reduced energy is high.
Most metal lattices readily welcome hydrogen atoms into there structure. Many here have observed severe hydrogen embrittlement in various metal central grids, mostly due to there thin cross section and high bombardment rate.
Please do not get the idea that any specific neutral whether of high or low speed will just bounce off the walls. This is just not the case. It is a complex issue and just can't be simplified.
Richard Hull
This is not like a baseball hitting hard metal and bouncing off. These are molecules slamming into a network of metal molecules in a lattice. They will embed!
In general, the higher energy ones will embed easier and deeper. Some will embed forever. Some of the weaker embeded deuterium atoms will pop back out as the chamber heats. This process is where the term "hydrogen embrittlement" comes from in materials science and metallurgy. These molecules can slowly work their way into the metal lattice, insinuatiing themselves ever deeper with continued molecular bombardment.
It might be likened to firing grains of wheat at varying speeds at a section of deep pile carpet some will embed so deep, they will never fall out. Others will fill the shag to a lesser degree and some already lightly stuck will be knocked out by an incoming grain. Ultimately the outer regions of the carpet will become clogged with wheat grains and will have zero energy embeded grains pop out on an almost one to one correspondence with incoming grains but with only a fraction of the energy. The lost energy being used to hammer lower grains ever deeper into the shag. The probability of complete bounce off by a specific incoming grain are very low while the probability of the "loaded surface" popping another molecule of deuterium out at greatly reduced energy is high.
Most metal lattices readily welcome hydrogen atoms into there structure. Many here have observed severe hydrogen embrittlement in various metal central grids, mostly due to there thin cross section and high bombardment rate.
Please do not get the idea that any specific neutral whether of high or low speed will just bounce off the walls. This is just not the case. It is a complex issue and just can't be simplified.
Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Linda Haile
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Re: Help required re speeds/energies of neutrals within the chamber
I suspected this would be the case Richard. That is why I asked the question.
I also previously posted:
' Also, no-one has suggested that neutrals can have sufficient energy to embed themselves in the chamber wall.'
Which no-one else has. Everyone else who has replied has stated that they will bounce off.
Hydrogen embrittlement was what prompted me to consider this and to ask the question.
Thanks for your detailed reply.
I also previously posted:
' Also, no-one has suggested that neutrals can have sufficient energy to embed themselves in the chamber wall.'
Which no-one else has. Everyone else who has replied has stated that they will bounce off.
Hydrogen embrittlement was what prompted me to consider this and to ask the question.
Thanks for your detailed reply.
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Linda Haile
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Re: Help required re speeds/energies of neutrals within the chamber
Dennis, I assume you mean 71 metres.(7.1X10^4cm) We have had the discussion about the incorrect usage of the term exp here before.
One thing that does puzzle me though is that you consider that neutrals will have an average energy of 30KeV.
I understood that a proton, accelerated by an electrostatic field of 30KV (typical for most fusors) would have an energy of 30Kev, a D+ ion would achieve half the velocity of a proton in the same electric field and that neutrals in a fusor are very slow compared to ions.
Are you able to clear up this confusion?
One thing that does puzzle me though is that you consider that neutrals will have an average energy of 30KeV.
I understood that a proton, accelerated by an electrostatic field of 30KV (typical for most fusors) would have an energy of 30Kev, a D+ ion would achieve half the velocity of a proton in the same electric field and that neutrals in a fusor are very slow compared to ions.
Are you able to clear up this confusion?