Tony,
Yes the 8 sided one does look a little coarse.
I started there because it is the simplest one.
I'm more partial to the 32 sided one.
The field lines bunch at both N & S poles for both cubic WB and for my design.
The confinement must happen at both N & S poles for both cubic WB and for my design.
In a cubic WB won't the electrons come out everywhere they can? That is at coil faces and at corner cusps?
Then they would have to go back in where ever their field lines go back in.
Same for mine.
I admit don't yet have a good understanding of the actual whiffle ball confinement mechanism.
(although I think I understand (to a first approximation) the mirror confinement)
I think it has to do with electron pressure affecting B field pressure & shape and with allowed electron energies related to gyro radius and to B field energy (specifically the amount of area over which it is below a certain energy). But I can't quite put all the pieces together.
CSA? What does that TLA mean? (TLA=Three Letter Acronym)
magrid configuration brainstorming
MSimon,
I was actually referring to the integral of the magnetic flux over any closed surface being equal to zero.
I apologize if that comment sounded pointed. I was getting excited.
I'm just a geek and sometimes the finer nuances get past me.
Didn't Dr B say they achieved a whiffle ball with the MPG devices?
Why wouldn't the octahedron or 32-hedron recirculate?
It has field lines going out. It has field lines going in. It has nothing in the way to stop the electrons from completing the loop, or from falling back in along the same line they left on.
My impression was that the cusp singluarities themselves were problematical.
My main point is that the field concentrations at the corners should be thought about in the same way as the field concentrations in the coils or any other fields.
I don't think they act like diodes. Do they?
I was actually referring to the integral of the magnetic flux over any closed surface being equal to zero.
I apologize if that comment sounded pointed. I was getting excited.
I'm just a geek and sometimes the finer nuances get past me.
Didn't Dr B say they achieved a whiffle ball with the MPG devices?
Why wouldn't the octahedron or 32-hedron recirculate?
It has field lines going out. It has field lines going in. It has nothing in the way to stop the electrons from completing the loop, or from falling back in along the same line they left on.
My impression was that the cusp singluarities themselves were problematical.
My main point is that the field concentrations at the corners should be thought about in the same way as the field concentrations in the coils or any other fields.
I don't think they act like diodes. Do they?
-Tom Boydston-
"If we knew what we were doing, it wouldn’t be called research, would it?" ~Albert Einstein
"If we knew what we were doing, it wouldn’t be called research, would it?" ~Albert Einstein
Wow, this is fun! 
I like Tombo's enthusiasm!
PS:
Edit: cleaning up quotes
I like Tombo's enthusiasm! Exactly. In fact, confinement might just be improved by making the 'in' and 'out' faces uniform instead of dissimilar (like the center vs. corner cusps). I think the discussion of the CSA (whatever that is) has to do w/ how Bussard placed the electron emitters outside the corner cusps since they were 'leakier.' That was better for injection, and the injection should have helped plug the corners somewhat.Tombo wrote:My main point is that the field concentrations at the corners should be thought about in the same way as the field concentrations in the coils or any other fields.
PS:
Haha, sounds like me!Tombo wrote:10 points to the first person who figures out what I’m procrastinating from.
Edit: cleaning up quotes
Last edited by Solo on Sun Jun 01, 2008 3:39 am, edited 1 time in total.
Hello Tom,
CSA = cross sectional area (previously referenced but poorly indicated, for which I apologise).
The path of an electron is not directly along the field line. The more spin the electron has, the more its path resembles a spiral along the field line. The spiral radius is described as the electron gyri radius. If this radius is larger than the field gradient then the electron experiences total internal reflection - the wiffleball effect - and it will not follow the field line out through the cusp; it just zings around in the centre region.
However it might be that the occasional electron has a low spin for some reason; this electron will follow the field line out through the cusp and it then stands a chance of colliding with pieces of metal and thereby being lost (= bad thing).
If the electron avoids grounding itself, it will come back in through the centre of the donut, and there it ought to re-enter the centre region as it is travelling with the field line. Tom Ligon and others talked about "annealing" of electrons in which the electrons were "de-thermalised" as they went out through the cusp and then back in. This would presumably make their radius smaller and allow them to re-enter the wiffleball through the tight field lines at the centre of the donut.
For these reasons I see there being a necessity for the field lines at the cusps to be tighter than the field lines at the donut centre. With this arrangement, low-spin electrons will not be lost to grounding, but will oscillate (MSimon's term) or recirculate out of and then back into the polywell.
Note that I understand this as a layman rather than a physicist, so if others think I have interpreted things incorrectly, please chime in with corrections. I did not understand the mechanism behind annealing; it sounds like refrigeration but I do not see the "sink" to dump the spin into.
Regards,
Tony Barry
CSA = cross sectional area (previously referenced but poorly indicated, for which I apologise).
The path of an electron is not directly along the field line. The more spin the electron has, the more its path resembles a spiral along the field line. The spiral radius is described as the electron gyri radius. If this radius is larger than the field gradient then the electron experiences total internal reflection - the wiffleball effect - and it will not follow the field line out through the cusp; it just zings around in the centre region.
However it might be that the occasional electron has a low spin for some reason; this electron will follow the field line out through the cusp and it then stands a chance of colliding with pieces of metal and thereby being lost (= bad thing).
If the electron avoids grounding itself, it will come back in through the centre of the donut, and there it ought to re-enter the centre region as it is travelling with the field line. Tom Ligon and others talked about "annealing" of electrons in which the electrons were "de-thermalised" as they went out through the cusp and then back in. This would presumably make their radius smaller and allow them to re-enter the wiffleball through the tight field lines at the centre of the donut.
For these reasons I see there being a necessity for the field lines at the cusps to be tighter than the field lines at the donut centre. With this arrangement, low-spin electrons will not be lost to grounding, but will oscillate (MSimon's term) or recirculate out of and then back into the polywell.
Note that I understand this as a layman rather than a physicist, so if others think I have interpreted things incorrectly, please chime in with corrections. I did not understand the mechanism behind annealing; it sounds like refrigeration but I do not see the "sink" to dump the spin into.
Regards,
Tony Barry
Thanks for the encouragement Solo.
Tony,
I think the internal reflection you describe is the mirror effect.
And I think I pretty much understand it about 3 different (compatible) ways.
We get mirror reflection whenever the electron moves toward a higher field strength region, even when the electron is headed directly toward a coil.
The hole in a mirror field is the area over which the field strength less than that required to keep the electron from passing through.
The holes are where the mirror breaks down
As it passes into the low field region the gyro radius opens up and sends it back to a high field region.
Different speed electrons see different sized holes.
The reflection is independent of the field direction.
But one of Dr. Bussard's papers [http://www.askmar.com/ConferenceNotes/2 ... 0Paper.pdf on Page 9] makes a distinction between the "mirror mode" and the "whiffle ball mode".
The mirror mode "inflates" somehow to become the whiffle ball mode as the plasma pushes the field out and distorts it.
Is the whiffle ball reflection just the mirror reflection from the modified magnetic field?
When the field is pushed by the electron pressure I can see how the arches would be compressed outward.
But does that really squeeze the field lines sideways away from the coil itself toward the coil center?
If so how?
But, what happens in the vicinity of the coil centers & cusp corners?
Is the "hole" in the field squeezed smaller?
This implies steeper gradient approaching the coil centerline approaching at constant radius from machine center. (Did that make sense? Oh, for a blackboard.)
Or is the field intensity itself increased at the coil center point?
Is the saddle point of the field (near the coil center point) pushed outward?
No I'm not expecting instant answers, but someone here might know.
I might be able to adjust the sizes of the triangles if we need to have a stronger field in some than in others.
But, it is neither obvious nor straightforward how to do it without bending the straight segments.
And I think that will just make some holes “leakier” than others.
The electrons are going to get out anywhere they can and come back in through one or the other kind of hole.
You talk as if the cusp at the corner of the cube acts like a diode and lets electrons in easier than it lets them out.
I don’t think that can be, but I could be wrong.
The mirror ratio is what determines the difficulty of passing through.
The only way it would be easier to pass through one way than the other is if the starting field is weaker on one side than the other.
In other words the mirror ratio from the outside to the coil center would have to be lower than the mirror ratio from the inside to the coil center.
In other-other words for it to be easier to pass in than out the field intensity at the point outside where it starts moving in would have to be higher than the field intensity inside the whiffle ball.
I can’t imagine how to arrange that.
Except maybe if something stops its outward progress while it is still very close to the coil and still deep in the field.
I’m not even going to try to sort out annealing at this point. I think it has to do with preferential losses of energetically undesirable electrons.
The octagonal well has 8 planes as boundaries. I has 8 faces=8 WB holes 4 field in & 4 field out.
The cubic well has 14 faces=14 WB holes: 6 field in & 8 field out.
the dodecahedron well has 32 faces=32 WB holes: 12 in & 20 out.
the 8x4 hedron well has 32 faces=32 WB holes 16 in & 16 out.
The electrons reflect from the bunched field lines just the same whether the field is north in or north out.
Also:
There is some ambiguity around the word cusp. I see at least 5 meanings in this field of study alone.
1 There is the cusp machine which is 2 coils facing each other.
2 There are the corners of the cube.
3 There is cusp confinement which seems to be a synonym for WB confinement.
4 There are point cusps
5 There are line cusps
Can anyone enlighten me as to the relationships among them?
Or should I just shut up and do some more homework?
I’m just a layman too who studied a lot of physics a loooonnng time ago.
[edited to make a few additions for clarity]
Tony,
I think the internal reflection you describe is the mirror effect.
And I think I pretty much understand it about 3 different (compatible) ways.
We get mirror reflection whenever the electron moves toward a higher field strength region, even when the electron is headed directly toward a coil.
The hole in a mirror field is the area over which the field strength less than that required to keep the electron from passing through.
The holes are where the mirror breaks down
As it passes into the low field region the gyro radius opens up and sends it back to a high field region.
Different speed electrons see different sized holes.
The reflection is independent of the field direction.
But one of Dr. Bussard's papers [http://www.askmar.com/ConferenceNotes/2 ... 0Paper.pdf on Page 9] makes a distinction between the "mirror mode" and the "whiffle ball mode".
The mirror mode "inflates" somehow to become the whiffle ball mode as the plasma pushes the field out and distorts it.
Is the whiffle ball reflection just the mirror reflection from the modified magnetic field?
When the field is pushed by the electron pressure I can see how the arches would be compressed outward.
But does that really squeeze the field lines sideways away from the coil itself toward the coil center?
If so how?
But, what happens in the vicinity of the coil centers & cusp corners?
Is the "hole" in the field squeezed smaller?
This implies steeper gradient approaching the coil centerline approaching at constant radius from machine center. (Did that make sense? Oh, for a blackboard.)
Or is the field intensity itself increased at the coil center point?
Is the saddle point of the field (near the coil center point) pushed outward?
No I'm not expecting instant answers, but someone here might know.
I might be able to adjust the sizes of the triangles if we need to have a stronger field in some than in others.
But, it is neither obvious nor straightforward how to do it without bending the straight segments.
And I think that will just make some holes “leakier” than others.
The electrons are going to get out anywhere they can and come back in through one or the other kind of hole.
You talk as if the cusp at the corner of the cube acts like a diode and lets electrons in easier than it lets them out.
I don’t think that can be, but I could be wrong.
The mirror ratio is what determines the difficulty of passing through.
The only way it would be easier to pass through one way than the other is if the starting field is weaker on one side than the other.
In other words the mirror ratio from the outside to the coil center would have to be lower than the mirror ratio from the inside to the coil center.
In other-other words for it to be easier to pass in than out the field intensity at the point outside where it starts moving in would have to be higher than the field intensity inside the whiffle ball.
I can’t imagine how to arrange that.
Except maybe if something stops its outward progress while it is still very close to the coil and still deep in the field.
I’m not even going to try to sort out annealing at this point. I think it has to do with preferential losses of energetically undesirable electrons.
The octagonal well has 8 planes as boundaries. I has 8 faces=8 WB holes 4 field in & 4 field out.
The cubic well has 14 faces=14 WB holes: 6 field in & 8 field out.
the dodecahedron well has 32 faces=32 WB holes: 12 in & 20 out.
the 8x4 hedron well has 32 faces=32 WB holes 16 in & 16 out.
The electrons reflect from the bunched field lines just the same whether the field is north in or north out.
Also:
There is some ambiguity around the word cusp. I see at least 5 meanings in this field of study alone.
1 There is the cusp machine which is 2 coils facing each other.
2 There are the corners of the cube.
3 There is cusp confinement which seems to be a synonym for WB confinement.
4 There are point cusps
5 There are line cusps
Can anyone enlighten me as to the relationships among them?
Or should I just shut up and do some more homework?
I’m just a layman too who studied a lot of physics a loooonnng time ago.
[edited to make a few additions for clarity]
Last edited by tombo on Mon Jun 02, 2008 2:13 am, edited 1 time in total.
-Tom Boydston-
"If we knew what we were doing, it wouldn’t be called research, would it?" ~Albert Einstein
"If we knew what we were doing, it wouldn’t be called research, would it?" ~Albert Einstein
Tom,
To answer all your questions:
At this time there is no coherent theory of Wiffle Ball formation published.
It must have something to do with electron circulation. I tried envisioning it and the patterns of interchange between the circulations and all I got is: how could that happen?
One possibility I thought of is that you have circulating electrons oscillating radially, inducing a current in the flow. I don't see how you would get a unidirectional flow out of that. But I may be a little dense on the subject.
Oh, for a steady state machine.
There are two kinds of cusps. Line cusps between the coils and point cusps at the corners. As long as electrons recirculate/oscillate they are not lost to the process and the energy drain they cause will not prevent net power. Focusing grids might be helpful in reducing losses.
I still think that the pole facing question impinges on Wiffle Ball formation.
Our current level of ignorance is astounding.
Whatever is going on it has not yet been reduced to engineering practice.
To answer all your questions:
At this time there is no coherent theory of Wiffle Ball formation published.
It must have something to do with electron circulation. I tried envisioning it and the patterns of interchange between the circulations and all I got is: how could that happen?
One possibility I thought of is that you have circulating electrons oscillating radially, inducing a current in the flow. I don't see how you would get a unidirectional flow out of that. But I may be a little dense on the subject.
Oh, for a steady state machine.
There are two kinds of cusps. Line cusps between the coils and point cusps at the corners. As long as electrons recirculate/oscillate they are not lost to the process and the energy drain they cause will not prevent net power. Focusing grids might be helpful in reducing losses.
I still think that the pole facing question impinges on Wiffle Ball formation.
Our current level of ignorance is astounding.
Whatever is going on it has not yet been reduced to engineering practice.
Engineering is the art of making what you want from what you can get at a profit.
i found it really helpful to listen again to 'the man' himself try and explain it:
http://video.google.com/videoplay?docid ... 6673788606
from 14:14 / 1:32:37 - (spherical grids, elmore tuck, watson)
to 26.48 / 1:32:37 - (wiffle-ball inflation and cusp losses - control factors)
... all seems to make perfect sense, now, wheres my sliderule...
http://video.google.com/videoplay?docid ... 6673788606
from 14:14 / 1:32:37 - (spherical grids, elmore tuck, watson)
to 26.48 / 1:32:37 - (wiffle-ball inflation and cusp losses - control factors)
... all seems to make perfect sense, now, wheres my sliderule...
@Tombo:
About the wiffleball: yeah, what MSimon said. We (on the forum) don't really know, I guess. It's easy enough to simulate the magnetic field of the coils, but modeling how the plasma modifies/interacts with it is not.
Yeah, from what I've read a mirror presents the same confinement ability on both sides (ie, not like a diode) because the loss cone is only dependent on the ratio of the magnetic field strength from the center to the throat, and not on the gradient. (Now, this paper about RF plugging of mirror cusps suggests that this kind of behavior can be created. Basically, the RF applied gives the electrons more gyro-radius momentum component so that they are not in the loss cone. I think I read elsewhere that it can be tailored to be selective like a diode.) And of course the positive charge on the magrid should serve to pull the electrons that pass thru the mirror back in again; that seems to be the gist of the so-called 'recirculation.'
Annealing is (IIRC) more of a concern for the ion population than the electrons: as short as electron confinement lifetimes are, the distribution doesn't spread much before the electrons are lost to the magrid. For ions, I think the idea is that they form some kind of waves or 'beam-bunching' either on their own, or with the help of an AC signal sent to the magrid. Then the waves keep the population monoenergetic.
@ cusps: take two coils and put them so the south faces are towards each other (or north, whichever). The cusp where the B-field lines come out between the two coils is a line cusp; the cusp at the center of each coil is a point cusp. A corner cusp is a special kind of point cusp.
About the wiffleball: yeah, what MSimon said. We (on the forum) don't really know, I guess. It's easy enough to simulate the magnetic field of the coils, but modeling how the plasma modifies/interacts with it is not.
Yeah, from what I've read a mirror presents the same confinement ability on both sides (ie, not like a diode) because the loss cone is only dependent on the ratio of the magnetic field strength from the center to the throat, and not on the gradient. (Now, this paper about RF plugging of mirror cusps suggests that this kind of behavior can be created. Basically, the RF applied gives the electrons more gyro-radius momentum component so that they are not in the loss cone. I think I read elsewhere that it can be tailored to be selective like a diode.) And of course the positive charge on the magrid should serve to pull the electrons that pass thru the mirror back in again; that seems to be the gist of the so-called 'recirculation.'
Annealing is (IIRC) more of a concern for the ion population than the electrons: as short as electron confinement lifetimes are, the distribution doesn't spread much before the electrons are lost to the magrid. For ions, I think the idea is that they form some kind of waves or 'beam-bunching' either on their own, or with the help of an AC signal sent to the magrid. Then the waves keep the population monoenergetic.
@ cusps: take two coils and put them so the south faces are towards each other (or north, whichever). The cusp where the B-field lines come out between the two coils is a line cusp; the cusp at the center of each coil is a point cusp. A corner cusp is a special kind of point cusp.
There's no "in" or "out" cusp - they are all equivelent. The trick to recirculation is to not lose electrons to wall or grid impacts - it is an efficiency issue. Think of the plasma as a superconductor - you want all the current to stay in the superconducting mode and not go normal or you lose power.
What I interpreted from Bussard's papers (so I could be way off base) was that the wiffle-ball effect pushed the grid field up against the coils and closed off the cusps. In effect, it adds to the field of the grid and decreases the loss cone angle. So how could you do that?
Have a current from the plasma run parallel to the coils. Here's where the geometry of the coils and understanding the plasma really is important. There may well be a weird shape that helps the plasma be self confining.
So back to tombo - If I assume that the entrance and exits are on the z axis, then the crudest coils has 4 points on the equator, the next level goes 4, 8, 4, and the next one would be 4, 8 , 16, 8, 4. It looks like you are running everything in quadrants. Does that sound right?
I'm not sure I'll get a chance to run some code today, but I will try to get something.
What I interpreted from Bussard's papers (so I could be way off base) was that the wiffle-ball effect pushed the grid field up against the coils and closed off the cusps. In effect, it adds to the field of the grid and decreases the loss cone angle. So how could you do that?
Have a current from the plasma run parallel to the coils. Here's where the geometry of the coils and understanding the plasma really is important. There may well be a weird shape that helps the plasma be self confining.
So back to tombo - If I assume that the entrance and exits are on the z axis, then the crudest coils has 4 points on the equator, the next level goes 4, 8, 4, and the next one would be 4, 8 , 16, 8, 4. It looks like you are running everything in quadrants. Does that sound right?
I'm not sure I'll get a chance to run some code today, but I will try to get something.
I was trying to imagine that (see up thread a little) and just got bogged down.drmike wrote:Have a current from the plasma run parallel to the coils. Here's where the geometry of the coils and understanding the plasma really is important. There may well be a weird shape that helps the plasma be self confining.
I still think that having all the faces N pointing in is critical to get the proper circulation for the WB effect. It is just a hunch. However, from studying his plan for WB-100 I'm convinced that the design feature was not chosen by accident.
The most interesting thing to me about the WB-100 design is that it is at the normal engineering limit for heat load. That shows that the 100 MW size was no accident. Thus I believe the magnetic facing of the magnets was no accident.
Think of a particle surfing on the N fields (facing in). They will all be bending in the same direction.
It will be really nice to get some experimental data about electron movement.
Engineering is the art of making what you want from what you can get at a profit.
Since nobody really knows how the WB effect occurs I will feel free to flail around here verbally grasping for straws that float.
I seem to detect disagreement on what the cusp means.
Does the line cusp run radially from the device center out through the coil center?
Or is that the point cusp where that radial line intersects the plane of the coil?
If the line cusp is in the corner where exactly is it?
Is it a straight line? Is it a curved line? Where does it run from and to?
I was thinking in terms of octants (each octant is a module) and of triangles and of triangles within triangles.
And I was thinking how I might make that coarse octahedron structure finer and more spherical and give it more turns (in a sense).
It reminds me of a Sierpinski gasket.
And if we need some coils larger than others for some reason then it is really easy to leave out the coil filling in the center triangles at 8x4x4 and above.
This would really make it as a Sierpinski triangle.
Getting that last triangle in the center of each triangle was kind of tough.
OH Now if get it. Yes the physical parts are quadrants yes.
That current should be within the outer few Debye lengths of the plasma.
I think the current direction will be opposite to the current in the coil due to Lenz’s law. (?)
This will decrease the field between it and the coil.
This “pushes back” the coil’s original field arches.
[This pushing of the fields visualization is easier for my primate brain to grasp but I don’t quite trust it to really work with magnetic fields unless I can see a mechanism to back it up.]
The ring shaped current induced in the outer layer of the plasma may itself induce a ring current deeper into the plasma where it can’t see the original coil (It’s a conductor like a Faraday cage.) but it can see the induced coil.
These echoes will continue some unknown distance into the plasma before the effect gets fuzzy.
There may be concentric layers of mirrors and WBs within the plasma.
Wouldn’t that be sweet!
I wonder if there is a way to optimize the coils to increase the effect.
But, back to the outer level:
How can that induced current “push” the holes in the coil centers closed? (This action is stated or implied somewhere.)
I don’t get it!
I think it would only be able to decrease the field strength anywhere between it and the real coil.
Sometime I need to get ephi running and try to put a conductive plane (or several) in front of a coil to see if it shows anything.
Then as they cross the regions where the field goes out (and these regions must be there) they reverse and go clockwise.
(If I’m using the right hand rule correctly.)
I’m not sure what I am supposed to be seeing with this surfing action.
I must be being dense.
25:20 thru 26:40 “the man” says (more or less):
“With enough electrons there is a pressure balance between magnetic field pressure and electron kinetic pressure.” OK sure of course.
“As they inject electrons it pushes the magnetic field out (I can see this from the rationale above) which causes the mirror confinement scaling to become cusp confinement scaling.”
What exactly is cusp confinement scaling??? He does not really describe it, only the result.
“As they add more and more electrons this makes the holes smaller and smaller.” WHY? HOW?
What is the mechanism? I don’t get it!
What effect strengthens the magnetic field at the coil centerline?
THIS IS WHERE I AM STUCK.
Annealing:
My take on it is this:
Different energy electrons see different size holes.
The faster ones have a bigger gyro radius so they see a smaller hole and fewer escape.
The slower ones have a smaller gyro radius so they see a larger hole and more escape.
So we keep the hotter electrons which are nearer the fusion energy, and we lose the colder electrons raising the temperature of the electron population closer to the fusion energy.
It is counter-intuitive that the low energy electrons would escape preferentially.
I would expect the higher energy ones to escape more readily.
Does it a really work that way?
I seem to detect disagreement on what the cusp means.
Does the line cusp run radially from the device center out through the coil center?
Or is that the point cusp where that radial line intersects the plane of the coil?
If the line cusp is in the corner where exactly is it?
Is it a straight line? Is it a curved line? Where does it run from and to?
You can think of it that way.So back to tombo - If I assume that the entrance and exits are on the z axis, then the crudest coils has 4 points on the equator, the next level goes 4, 8, 4, and the next one would be 4, 8 , 16, 8, 4. It looks like you are running everything in quadrants. Does that sound right?
I was thinking in terms of octants (each octant is a module) and of triangles and of triangles within triangles.
And I was thinking how I might make that coarse octahedron structure finer and more spherical and give it more turns (in a sense).
It reminds me of a Sierpinski gasket.
And if we need some coils larger than others for some reason then it is really easy to leave out the coil filling in the center triangles at 8x4x4 and above.
This would really make it as a Sierpinski triangle.
Getting that last triangle in the center of each triangle was kind of tough.
OH Now if get it. Yes the physical parts are quadrants yes.
Yes each coil will induce a current in the conductive plasma next to it.Have a current from the plasma run parallel to the coils. Here's where the geometry of the coils and understanding the plasma really is important. There may well be a weird shape that helps the plasma be self confining.
That current should be within the outer few Debye lengths of the plasma.
I think the current direction will be opposite to the current in the coil due to Lenz’s law. (?)
This will decrease the field between it and the coil.
This “pushes back” the coil’s original field arches.
[This pushing of the fields visualization is easier for my primate brain to grasp but I don’t quite trust it to really work with magnetic fields unless I can see a mechanism to back it up.]
The ring shaped current induced in the outer layer of the plasma may itself induce a ring current deeper into the plasma where it can’t see the original coil (It’s a conductor like a Faraday cage.) but it can see the induced coil.
These echoes will continue some unknown distance into the plasma before the effect gets fuzzy.
There may be concentric layers of mirrors and WBs within the plasma.
Wouldn’t that be sweet!
I wonder if there is a way to optimize the coils to increase the effect.
But, back to the outer level:
How can that induced current “push” the holes in the coil centers closed? (This action is stated or implied somewhere.)
I don’t get it!
I think it would only be able to decrease the field strength anywhere between it and the real coil.
Sometime I need to get ephi running and try to put a conductive plane (or several) in front of a coil to see if it shows anything.
You mean like counterclockwise looking from the device center out at the coil?Think of a particle surfing on the N fields (facing in). They will all be bending in the same direction.
Then as they cross the regions where the field goes out (and these regions must be there) they reverse and go clockwise.
(If I’m using the right hand rule correctly.)
I’m not sure what I am supposed to be seeing with this surfing action.
I must be being dense.
25:20 thru 26:40 “the man” says (more or less):
“With enough electrons there is a pressure balance between magnetic field pressure and electron kinetic pressure.” OK sure of course.
“As they inject electrons it pushes the magnetic field out (I can see this from the rationale above) which causes the mirror confinement scaling to become cusp confinement scaling.”
What exactly is cusp confinement scaling??? He does not really describe it, only the result.
“As they add more and more electrons this makes the holes smaller and smaller.” WHY? HOW?
What is the mechanism? I don’t get it!
What effect strengthens the magnetic field at the coil centerline?
THIS IS WHERE I AM STUCK.
Annealing:
My take on it is this:
Different energy electrons see different size holes.
The faster ones have a bigger gyro radius so they see a smaller hole and fewer escape.
The slower ones have a smaller gyro radius so they see a larger hole and more escape.
So we keep the hotter electrons which are nearer the fusion energy, and we lose the colder electrons raising the temperature of the electron population closer to the fusion energy.
It is counter-intuitive that the low energy electrons would escape preferentially.
I would expect the higher energy ones to escape more readily.
Does it a really work that way?
-Tom Boydston-
"If we knew what we were doing, it wouldn’t be called research, would it?" ~Albert Einstein
"If we knew what we were doing, it wouldn’t be called research, would it?" ~Albert Einstein
Grasping at straws while shooting in the dark:
Suppose it is not a real physical tightening of the holes. i.e. increased field. Suppose instead it is a reduced probability cause by particles surfing on the N fields don't line up properly to escape on the S fields?
Suppose the whole Wiffle Ball effect is a function of the fact that most of the electrons are located away from the field holes.
Suppose it is not a real physical tightening of the holes. i.e. increased field. Suppose instead it is a reduced probability cause by particles surfing on the N fields don't line up properly to escape on the S fields?
Suppose the whole Wiffle Ball effect is a function of the fact that most of the electrons are located away from the field holes.
Engineering is the art of making what you want from what you can get at a profit.
A "cusp" is any where that magnetic fields from the same pole meet. So put 2 north poles facing each other, the "cusp" is a circle that goes all the way around both magnets. If you draw the cube with a magnet on each face, there is a cusp on all the cube edges as well as in the center of each face.
I uploaded really poor pictures of the math for tombo's coil idea, I'm going to have to figure out a better way to do that. This is simple enough I can write it up in pdf pretty quickly so I'll do that when I get a chance.
The zeroth order estimate I'll put up will not have gaps in the corners. That's not very realistic. I think the reason Bussard chose round coils was to reduce the electron impact in those corners. But I also think it will be really good to build the fields and look at them.
I looked at the SciRun again. It would be a lot of work to make it happen on my present home machine. I can generate the field data easily, and I'll be happy to work with people to convert the data into something that SciRun or other visualization programs can read.
We'll see how far I get this week on it....
I uploaded really poor pictures of the math for tombo's coil idea, I'm going to have to figure out a better way to do that. This is simple enough I can write it up in pdf pretty quickly so I'll do that when I get a chance.
The zeroth order estimate I'll put up will not have gaps in the corners. That's not very realistic. I think the reason Bussard chose round coils was to reduce the electron impact in those corners. But I also think it will be really good to build the fields and look at them.
I looked at the SciRun again. It would be a lot of work to make it happen on my present home machine. I can generate the field data easily, and I'll be happy to work with people to convert the data into something that SciRun or other visualization programs can read.
We'll see how far I get this week on it....
Yeah, the writing can't be read because it's blurry. Not complaining. I've had plenty of challenges along the same lines.drmike wrote:I uploaded really poor pictures of the math for tombo's coil idea, I'm going to have to figure out a better way to do that. This is simple enough I can write it up in pdf pretty quickly so I'll do that when I get a chance.
http://www.askmar.com/ConferenceNotes/2 ... 0Paper.pdfDoes the line cusp run radially from the device center out through the coil center?
Finally, a larger version of the closed box device (PXL-1)
was built as WB-5 (2004-2005), to test improvements in
magnetic insulation by use of external surface and cusp coils
at high fields. Figure 10 shows this system. Its test results
showed 1000-fold improvement (in ability to reach deep
fractional well depth at given starting pressures; early work
was limited to 3E-9 torr, while WB-5 ran at 3E-6 torr) from
early work (1989-91) on a larger closed-box machine (Ref.
6) but its inability to be driven beyond this increase
illuminated the critical and dominating effect of unshielded
surface losses of electrons, on overall system performance.
From the picture, it appears the "cusps" as Bussard meant them are the corners of the Magrid and also the center of each square; basically, all the places where several magnetic fields meet at a point (all the places in Fig 10 where you see a little coil with wires attached), as drmike described above.
One way to look at this is that in WB-6, Bussard sort of went back towards the original concept of a fusor. Like a fusor, the grid is open, but unlike a fusor the grid is protected from electron loss by the magnetic field.
I think the reason Bussard chose round coils was to reduce the electron impact in those corners.
Yes.
5. In these systems electron loss phenomena are solely
to (metal) surfaces of the machine system. Cross-field
losses are well understood and can be controlled. However,
losses to poorly shielded (by fields) or unshielded surfaces
can constitute major loss channels. From WB-5 and WB-6 it
has been proven that that the fractional area of unshielded
surfaces must be kept below 1E-4 to 1E-5 of the total surface
area, if electron losses are to be kept sufficiently small so
that net power can be achieved. And, further, that no B
fields can be allowed to intersect any such internal surfaces
of the machine.
6. This requirement has two main consequences: (a) All
coil containers/casings must be of a shape conformal to the
B fields produced by their internal current conductors, and;
(b) The finite size of real coils forces design so that no
coils/containers can ever be allowed to touch each other, but
all corners MUST be spaced at some distance from the
adjacent coils, to avoid B field intercept.
....
--The need for magnetic field coil containing structures
to be conformal with the B fields they produce, to
avoid excessive electron impact losses (as above).