I often make mental models of problems I encounter. I wanted to get a rough idea of the landscape that ions travel, in so doing I came up with this model. The model was inverted to show the electrons view. I haven't accounted for ion current or electron current. Comments and corrections welcome.
Joe Sal
Landscape
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Steven Sesselmann
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Re: Landscape
Joe,
I love your model, just like the one I had in my head.
It looks correct for low voltages, with the lowest potential around the cathode wires. How does it look for more extreme voltages?
I expect that in the proton view, the slope between the anode and the cathode deepens, and that the zone inside the cathode elevates, as more and more protons are trapped in the Faraday cage.
Then at a point, when the poissor goes into star mode, a virtual cathode appears as a deep well inside the physical cathode.
Nice work..
Steven
I love your model, just like the one I had in my head.
It looks correct for low voltages, with the lowest potential around the cathode wires. How does it look for more extreme voltages?
I expect that in the proton view, the slope between the anode and the cathode deepens, and that the zone inside the cathode elevates, as more and more protons are trapped in the Faraday cage.
Then at a point, when the poissor goes into star mode, a virtual cathode appears as a deep well inside the physical cathode.
Nice work..
Steven
http://www.gammaspectacular.com - Gamma Spectrometry Systems
https://www.researchgate.net/profile/Steven_Sesselmann - Various papers and patents on RG
https://www.researchgate.net/profile/Steven_Sesselmann - Various papers and patents on RG
Re: Landscape
I left it shallow for representation. As voltage ascends it could get very deep. The center plateau is still a bit of a mystery. From what I understand it should be at neutral.
I will try to model with ion currents soon.
Joe Sal
I will try to model with ion currents soon.
Joe Sal
Re: Landscape
From simulations I have done, and a couple were posted ages ago, somewhere on here, the center of the cathode cage is slightly more POSITIVE than the cathode wires themselves. As I recall, and it varies with the amount of openness of the cathode structure, the central region is about 8 - 10% less negative than the cathode electrode wires.
Further, there are "channels" of positive potential that lead out through the openings in the cathode grid, and are probably where the so-called "star rays" are formed.
Given that the fusor operates with the central HV electrode negative and the shell at ground, the star would seem to have to be positive, not negative, since the incoming ions collide (or at least pass through) there.
The glow we see is most likely the result of an ion-electron recombination process, which shrinks as the voltage increases, because the volume over which collisions can occur diminishes as the ion velocity increases.
Dave Cooper
Further, there are "channels" of positive potential that lead out through the openings in the cathode grid, and are probably where the so-called "star rays" are formed.
Given that the fusor operates with the central HV electrode negative and the shell at ground, the star would seem to have to be positive, not negative, since the incoming ions collide (or at least pass through) there.
The glow we see is most likely the result of an ion-electron recombination process, which shrinks as the voltage increases, because the volume over which collisions can occur diminishes as the ion velocity increases.
Dave Cooper
Re: Landscape
I was having a tough time visualizing until Dave posted his simulations. In particular, I wasn't seeing the well that the electrons could occupy in the center. Thanks to Dave Cooper and many others, it is getting clearer.
I can now see the areas that could be a "recombination zone".
Here is a model with ion currents. They aren't "fanned" correctly, and do not take into account effects of electron current. Also an inverted model included.
Just looking at these, it looks as if fusions occur at glancing blows.
Joe Sal
I can now see the areas that could be a "recombination zone".
Here is a model with ion currents. They aren't "fanned" correctly, and do not take into account effects of electron current. Also an inverted model included.
Just looking at these, it looks as if fusions occur at glancing blows.
Joe Sal
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Richard Hull
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Re: Landscape
Dave re-iterated what I have noted all along. If you see a glow you are not seeing plasma. You are seeing plasma die (recombination).
The densest plasmas glow fiercely as there are more opportunities and probabilities for recombination per unit volume. The true plasma, of course, is always invisible in the normal plasma environments we are used to working with and studying.
The glow is the very thing that limits a thermal ion system, leaving the maxwellian tail of just the fewer fastest ions to do the fusion. The rest are just doing "heaty type things" and recombining.
Richard Hull
The densest plasmas glow fiercely as there are more opportunities and probabilities for recombination per unit volume. The true plasma, of course, is always invisible in the normal plasma environments we are used to working with and studying.
The glow is the very thing that limits a thermal ion system, leaving the maxwellian tail of just the fewer fastest ions to do the fusion. The rest are just doing "heaty type things" and recombining.
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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Steven Sesselmann
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Re: Landscape
Joe,
Your modelling depicts the electrical potential, but have you concidered modelling the potential energy well. It will look similar up to the point of fusion. At the point in the centre of your fusor, where the protons collide and fuse, you have a sharp tip. I expect that there will be a sharp drop in the potential there, causing a deep hole in the middle.
What do you think?
Steven
Your modelling depicts the electrical potential, but have you concidered modelling the potential energy well. It will look similar up to the point of fusion. At the point in the centre of your fusor, where the protons collide and fuse, you have a sharp tip. I expect that there will be a sharp drop in the potential there, causing a deep hole in the middle.
What do you think?
Steven
http://www.gammaspectacular.com - Gamma Spectrometry Systems
https://www.researchgate.net/profile/Steven_Sesselmann - Various papers and patents on RG
https://www.researchgate.net/profile/Steven_Sesselmann - Various papers and patents on RG
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Alex Aitken
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Re: Landscape
The best evidence is the fusor does not work that way.
The electric potential is the potential energy well.
The electric potential is the potential energy well.
Re: Landscape
I have speculated that many of the most energetic ions pass through the center creating the small spike. The less energetic ones glance off at varied angles. Some may slow to the point that recombination occurs.
There is evidence (if true) that fusion is less focused and more evenly distibuted within the volume of the inner grid. forum Links:
viewtopic.php?f=14&t=6356#p42039
viewtopic.php?f=14&t=6690#p42373
I'm interested in how you see the PE well. I'm putting it together in my thoughts. Maybe less of a spike and more of a ring in the center?
Joe Sal
Re: Landscape
I see it now, one of those "forest for the trees" things. I think the well your considering should exist, but would be very small in proportion to the number of ions
traveling through. The probability of "collision" is very small. Parameters are leveraged hard in our favor to achieve the small amounts of fusion that occur.
Joe Sal
traveling through. The probability of "collision" is very small. Parameters are leveraged hard in our favor to achieve the small amounts of fusion that occur.
Joe Sal
Re: Landscape
Joe - A question and an observation:
Question - I probably missed it, in the discussions, here, but are you actually running a simulation program for the electron - ion trajectories?
The observation concerns the potential of the region at the fusor center - where the "poissor" is seen.
We have already noted that simulations of electrode cages suggests the internal region can be something like 8 to 10% more positive than the cathode cage wires themselves. This is without any kind of ion or electron flux.
The view promoted by Farnsworth, and furthered by Hirsch and others, argues for the virtual cathode or anode structures to form from clusters or slower moving ions/electrons.
A common approach to determining the potential of these virtual electrodes is to do some arm waving calculations that seem to assume all the charge in the fusor converges on intersecting lines toward the center. Thus, the resulting potential in joules, will be of the same magnitude as the kinetic energy of the inbound ions. In the most idealized scenario, the ions will come to a stop and reverse directions, or.... they will actually fuse.
The idea is attractive, but I think not very accurate.
Rather, the ions move towards the fusor center on paths that pass through the central region, but not the exact geometric center of the potential field.
Thus the ions get closer toegether, but not really very close, and their paths, consist of looping spirals (or simply slight curves) that take them out towards the fusor walls. Some may actually curve back in, but most will hit the wall on the first pass through the center. Hence the hot outer walls of the fusor, that we all know so well.
What does this do for the voltage in the center - at the "possior"? It may make it slightly more positive to the tune of millivolts or volts, but even that depends on the trajectory specifics. To raise the potential due to charge presence ( space charge) requires ion approaches in the range of sub nano-meters, i.e.: molecular dimensions.
Now we need to pause here for a moment to think about what it takes for two objects on exactly intersecting paths (like a street intersection, for example)... to actually collide or have " near miss" experience.
The objects need to pass through that intersection area (or volume if we're talking about 3D) within a distance equal to their nominal radius. A D2+ ion radius is pico meters. At a distance of nano- meters, the passing of two ions, will create potentials of a few volts, at most.
To get a potential energy equal to the incoming kinetic energy (10's of KeV), they will need to approach within 0.036 pico meters! We can all do the math.... U = q/(4pi epsilon r).
The likelihood of this happening from the unfocussed stew of ions of various energies arriving inbound from the fusor outer volume, is very small. Hence little fusion takes place in this region.
Out in the volume of the fusor, any neutral D2 molecule is fair game, and more or less stationary... making it a much more likely target for the now outward bound and rapidly slowing, ion. Thus, higher pressure, which means more gas molecules per unit volume, should give more neutrons, and more kinetic energy (voltage) and more ions per second (current) all contribute to higher neutron yields.
The ion with neutral gas collisions suggest that significant over- voltages may be needed to have ions arrive with enough energy to fuse. Chilling the fusor walls with LN2 would produce a denser cold gas at the outer edges, which could raise neutron yield if the ion energy ( voltage) was high enough.
This last would be a "fairly" easy experiment to implement. It would take a reduction in absolute temperature of about half to raise the gas density locally by (1/0.5) or 2x.
Just some more thoughts to mull over.
Dave Cooper
Question - I probably missed it, in the discussions, here, but are you actually running a simulation program for the electron - ion trajectories?
The observation concerns the potential of the region at the fusor center - where the "poissor" is seen.
We have already noted that simulations of electrode cages suggests the internal region can be something like 8 to 10% more positive than the cathode cage wires themselves. This is without any kind of ion or electron flux.
The view promoted by Farnsworth, and furthered by Hirsch and others, argues for the virtual cathode or anode structures to form from clusters or slower moving ions/electrons.
A common approach to determining the potential of these virtual electrodes is to do some arm waving calculations that seem to assume all the charge in the fusor converges on intersecting lines toward the center. Thus, the resulting potential in joules, will be of the same magnitude as the kinetic energy of the inbound ions. In the most idealized scenario, the ions will come to a stop and reverse directions, or.... they will actually fuse.
The idea is attractive, but I think not very accurate.
Rather, the ions move towards the fusor center on paths that pass through the central region, but not the exact geometric center of the potential field.
Thus the ions get closer toegether, but not really very close, and their paths, consist of looping spirals (or simply slight curves) that take them out towards the fusor walls. Some may actually curve back in, but most will hit the wall on the first pass through the center. Hence the hot outer walls of the fusor, that we all know so well.
What does this do for the voltage in the center - at the "possior"? It may make it slightly more positive to the tune of millivolts or volts, but even that depends on the trajectory specifics. To raise the potential due to charge presence ( space charge) requires ion approaches in the range of sub nano-meters, i.e.: molecular dimensions.
Now we need to pause here for a moment to think about what it takes for two objects on exactly intersecting paths (like a street intersection, for example)... to actually collide or have " near miss" experience.
The objects need to pass through that intersection area (or volume if we're talking about 3D) within a distance equal to their nominal radius. A D2+ ion radius is pico meters. At a distance of nano- meters, the passing of two ions, will create potentials of a few volts, at most.
To get a potential energy equal to the incoming kinetic energy (10's of KeV), they will need to approach within 0.036 pico meters! We can all do the math.... U = q/(4pi epsilon r).
The likelihood of this happening from the unfocussed stew of ions of various energies arriving inbound from the fusor outer volume, is very small. Hence little fusion takes place in this region.
Out in the volume of the fusor, any neutral D2 molecule is fair game, and more or less stationary... making it a much more likely target for the now outward bound and rapidly slowing, ion. Thus, higher pressure, which means more gas molecules per unit volume, should give more neutrons, and more kinetic energy (voltage) and more ions per second (current) all contribute to higher neutron yields.
The ion with neutral gas collisions suggest that significant over- voltages may be needed to have ions arrive with enough energy to fuse. Chilling the fusor walls with LN2 would produce a denser cold gas at the outer edges, which could raise neutron yield if the ion energy ( voltage) was high enough.
This last would be a "fairly" easy experiment to implement. It would take a reduction in absolute temperature of about half to raise the gas density locally by (1/0.5) or 2x.
Just some more thoughts to mull over.
Dave Cooper
Re: Landscape
I basically sketched a rough outline of your simulations in Autocad 2004 and extruded them negative, positive and neutral. I have tried to match gradients, but may be +\\-. Basically just a visual aid.
It'll take some time to mull on the observation, maybe a day or two.
Joe Sal
Re: Landscape
The process of "smacking" together same charged particles together to achieve fusion requires considerable "leverage". This leverage from what I understand comes from the voltage gradient to the inner grid. After an ion starts falling AWAY from the grid it slows and loses it's ability to deliver a substantial blow to anything but the fusor wall.
Your equation does show how the collision probability drops for two "high speed" inbound ions. It is more likely that a "high speed" ion smacks a neutral meandering about the intersection. This may be why we see a more uniform distribution of fusion occuring within the grid volume.
Now, if we raise the pressure by releasing more neutrals to the environment, many more neutrals are meandering about the intersection. Possibly leading to a quick increase in the neutron counts. The road gets congested though. Mean free path suffers, and soon the count should taper off.
If we increase the voltage, the "pits" we see around the wires get larger. The channels get narrower, and many would be (useful) ions fall into the pits. Only the strongest with the best trajectory survive. It does "focus" but at a high cost in number of ions.
If that isn't a tough enough situation, If we consider Schrodinger's work, there is only a probability of fusion. What if the probability is only 50%. Half of the best "collisions" may end up as changes in trajectory.
Chilling the neutrals may show some gain. They'll just meander a bit slower, making easier targets. Maybe if they are chilled and injected within the inner grid. Again one has to keep mean free path in mind when factoring temperature.
Has anybody put their lecture D2 bottle on ice before operating?
Joe Sal
Your equation does show how the collision probability drops for two "high speed" inbound ions. It is more likely that a "high speed" ion smacks a neutral meandering about the intersection. This may be why we see a more uniform distribution of fusion occuring within the grid volume.
Now, if we raise the pressure by releasing more neutrals to the environment, many more neutrals are meandering about the intersection. Possibly leading to a quick increase in the neutron counts. The road gets congested though. Mean free path suffers, and soon the count should taper off.
If we increase the voltage, the "pits" we see around the wires get larger. The channels get narrower, and many would be (useful) ions fall into the pits. Only the strongest with the best trajectory survive. It does "focus" but at a high cost in number of ions.
If that isn't a tough enough situation, If we consider Schrodinger's work, there is only a probability of fusion. What if the probability is only 50%. Half of the best "collisions" may end up as changes in trajectory.
Chilling the neutrals may show some gain. They'll just meander a bit slower, making easier targets. Maybe if they are chilled and injected within the inner grid. Again one has to keep mean free path in mind when factoring temperature.
Has anybody put their lecture D2 bottle on ice before operating?
Joe Sal
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Todd Massure
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- Real name: Todd Massure
Re: Landscape
It would be interesting to see a simulation of a small sphere rolling around on these landscapes for further visualization (beyond my CAD skills!). Thanks for these great graphic representations
Todd
Todd
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Todd Massure
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- Real name: Todd Massure
Re: Landscape
I just found this right after my last post, it's pretty cool, it lets you place point charges anywhere on the black screen by clicking the cursor, and it shows the resulting field lines.
http://www.cco.caltech.edu/~phys1/java/ ... Field.html
more fun stuff at
http://www.cco.caltech.edu/~phys1/java.html
I like the moving charge applet!
Todd M.
http://www.cco.caltech.edu/~phys1/java/ ... Field.html
more fun stuff at
http://www.cco.caltech.edu/~phys1/java.html
I like the moving charge applet!
Todd M.
Re: Landscape
I've used 3D Studio with autocad in the past for complicated animations. It takes some time, but is good fun. I'll see if I can find a copy of 3d Studio over the next few weeks, and get the ball a rolling.
Joe Sal
Joe Sal
Re: Landscape
Todd,
Thanks for the link to the applets! I worked a little with it yesterday. Good fun!
Joe Sal
Thanks for the link to the applets! I worked a little with it yesterday. Good fun!
Joe Sal