cusps
cusps
If charged particles leaving the cusps is a problem why not just stick a highly negatively charged plate aligned to the corners to repel them back into the machine?
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kunkmiester
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Re: cusps
The way the machine is designed, an electron coming out of the cusp is supposed to circle around the magnetic fields to another cusp and go back in. Alpha particles are supposed to leave. A plate would complicate things, and since they already figure they can hold the machine in a positive power generation mode, there's no point in messing with the extra work.
Evil is evil, no matter how small
Re: cusps
A test was run with electrostatic repeller plates. Placed close to the cusps they repelled one charge and draw in the other. The WB6 form with a charged magrid inside a cage effectively places repeller plates at a distance where they can act on electrons but ions don't see them past the magrid.
The daylight is uncomfortably bright for eyes so long in the dark.
Re: cusps
Repeller plates seem to be a perpetual concept for containing charged particles, electrons specifically, from transiting a cusp. This is brought up repeatedly on this forum. This was tried and failed miserably. As stated, in WB5, repellar plates were placed just outside the cusps. They were found to repel the electrons (negatively charged plates) back into the machine. But, they attracted internal ions, presumably those which were at or near the topof their potential well near the periphery of the internal volume. This results in trading electron losses for ion losses and did not work. One of the key consequences of this was the realization that only open designs with non plugged cusps could work. The electrons have to be able to transit the cusps at high velocity. If they can be slowed and reversed well outside the cusp or follow a magnetic field line around to another cusp introduced the new (?) concept of recircuation. It serves the electron confinement requirements without the penalty of losing the dominate ion containing properties of a central potential well for the ions.
If Gauss law was absolute in this machine, repellars slightly outside the radius of the mid plane of the Magrid would work. But as demonstrated with radio wave frequency signals and Faraday cages, if there are holes, higher frequency signals can penetrate. I'm uncertain how this applies to the dynamics of a neutral or non neutral plasma within a Magrid, but experiment demonstrated that it cannot be ignored. How much details EMC2, Lockheed and perhaps others have gained in this regard is unknown. In the patent application for EMC2 it was mentioned that the E- guns (might be considered a repellar depending on design) have to be placed a certain distance beyond the Magrid radius. Close enough that cusp penitration of new electrons is not impeded to much , but far enough away that repellar plate like effects are minimized. These competing process is still an issue, perhaps the dominate issue that needs to be solved for progression of the Polywell concept.
Cusp plugging by cold electrons in the cusps near the cusp radius midplane is bad. This applies to repellar plates or slow- cold electrons due to the natural dynamics of the electrons potential well. The distintion of cold or hot electrons is key. The same number of electrons could be exiting a cusp. This is at the bottom of theit internal potential well- they are hot- fast. If they are slow- cold in this region the electrons hang around longer locally. The space charge builds up and this can repell further electrons. The collection of cold electrons grows. This is perhaps good for containing further electrons, but there are two consequences. First the ions are attracted and ion containment suffers. Secondly is the dynamics of the otherwise contained elecgrons and ions. Electrons that are contained, either by turning on the B field near the cusp or by being repelled back inside are cooled. The dynamic of hot electrons on the edge and cold electrons in the center is diminished and the net effective potential well for ion acceleration is globally suppressed. The inverse of this is that from the ions perspective there are two potential wells. The centally located one that is weakened, and the potential well at the cusps due to locally cold electrons. Inverse square laws and some factor reflecting the effectiveness of Gauss Law considerations- especially for ions that come near the Magrid radius at a cusp leads to loss of electrostatic containment of not only up mildly upscattered ions but also possibly average energy ions as they approach the magrid radius.
In WB6, with it's positively charged magrid (more positive that the comparable escaping electron negative potential) The electron starts to slow as it passes to greater radii than the magrid, stops and reverses back through the same cusp. The important point is that this slowing and reversal and reacceleration occurs at some distance past the magrid due to the elecrons inertia. This is supposed to be a great enough distance that cusp plugging with cold ions is mitigated enough. Weather this is the case is uncertain , as it seems EMC2 may have dismissed this approach in WB8 and Mini B. Now they seem to be using high voltage Electron guns where the electrons are accelerated to high speeds much further from the magrid radius. The cold electrons are thus much further away and inverse square law effects dilute effects relative to the ion containing internal potential well. Unfortionatly this may also impede new electron injection due to mirroing external to the magrid midplane.
In this situation with a neutrally biased magrid, there is nothing to slow the electrons as they exit a cusp to greater radii, thus they will 'stick' to a B field line and loop around to another cusp, and possibly reenter the central space. The particulars are different, but the final result may be the same, except the cold electron in the cusps issue is ideally eliminated.
Both EMC2 and Lockheed may now be pursueing this course. How does it compare to WB6? The total electron confinement due to Wiffleball effect and recirculation may be ~ the same, or nearly so, and the ion confinement may actually be improved, perhaps significantly. Even id ion confinement is not improved, there may be other benifits- a better potential well geometrythat leads to better ion confluency/ central focus, and a deeper effective ion potential well.
Note that the external escaped electron (or mirrored injection electron) population reflects the flight times of the electrons(Voltage , KE, velocity) and current. There are ideally no ions. As such the Brillion limit precludes build up on much external pressure and thus high Beta in this region is impossible. The B field gradient is much shallower than the electron gyro radius so that there is no "sharp edge" for the electrons to reflect from. Normal gyro radius spiraling along a B field line is dominate- thus the looping along a line to enter a neighboring cusp. Because the exterior electrons are at relatively low pressure (and any ions that may be tagging along) the pressure/ ion density is low and thus fusion in this exterior region is minimal. It is all about recirculating the high energy electrons.
You could pursue the idea of adding additional layers but this introduces progessively more losses through ExB diffusion, etc. until it becomes dominate. You could not expand the system by adding layers- like an onion, though you might extend it linearly by stacking core regions end to end.
With electrons looping around field lines exterior to the magrid the magnetic lines become concave towards the plasma- primarily made up of electrons, but still plasma. This locally magnatized plasma would suffer from edge instabilities- macro instabilities . The saving grace is that the density of this electron plasma is much less than the density within the magrid core space, so the local edge instabilities are much less contributory. This does reenforce what I said above - the fusion (density dependent) is limited to the internal core. I think this distinguishes this approach from the FRC approach. Local B field reversal may apply, but not to the portion of the plasma that is contributing to fusion.
Magrid/ magrid is used as a discriptive term for the high Beta containing structure weather it is a Polywell, or a three ring linear arrangement of magnets.
Additional note: With the core concept surrounded by a combination of line and point cusps, fusion product ions would still naturally exit the system through a cusp before any significant thermalization. They are not electrostatically confined as are the fuel ions. This allows for direct conversion opportunities, and I think, precludes the possibility of ignition. The exception to this would be if the vacuum vessel wall was moved far enough away, the fusion ions might loop around and re enter the core region. Also, with stacked cores the fusion ions that escaped one core through the on axis point cusps would enter another core and bounce around for a while till another cusp was found, etc. In this case plasma heating by the fusion ions cold increase to significant levels. This could be beneficial or harmful depending on which considerations you are looking at (essentially self heating versus mono energetic preferences).
Dan Tibbets
If Gauss law was absolute in this machine, repellars slightly outside the radius of the mid plane of the Magrid would work. But as demonstrated with radio wave frequency signals and Faraday cages, if there are holes, higher frequency signals can penetrate. I'm uncertain how this applies to the dynamics of a neutral or non neutral plasma within a Magrid, but experiment demonstrated that it cannot be ignored. How much details EMC2, Lockheed and perhaps others have gained in this regard is unknown. In the patent application for EMC2 it was mentioned that the E- guns (might be considered a repellar depending on design) have to be placed a certain distance beyond the Magrid radius. Close enough that cusp penitration of new electrons is not impeded to much , but far enough away that repellar plate like effects are minimized. These competing process is still an issue, perhaps the dominate issue that needs to be solved for progression of the Polywell concept.
Cusp plugging by cold electrons in the cusps near the cusp radius midplane is bad. This applies to repellar plates or slow- cold electrons due to the natural dynamics of the electrons potential well. The distintion of cold or hot electrons is key. The same number of electrons could be exiting a cusp. This is at the bottom of theit internal potential well- they are hot- fast. If they are slow- cold in this region the electrons hang around longer locally. The space charge builds up and this can repell further electrons. The collection of cold electrons grows. This is perhaps good for containing further electrons, but there are two consequences. First the ions are attracted and ion containment suffers. Secondly is the dynamics of the otherwise contained elecgrons and ions. Electrons that are contained, either by turning on the B field near the cusp or by being repelled back inside are cooled. The dynamic of hot electrons on the edge and cold electrons in the center is diminished and the net effective potential well for ion acceleration is globally suppressed. The inverse of this is that from the ions perspective there are two potential wells. The centally located one that is weakened, and the potential well at the cusps due to locally cold electrons. Inverse square laws and some factor reflecting the effectiveness of Gauss Law considerations- especially for ions that come near the Magrid radius at a cusp leads to loss of electrostatic containment of not only up mildly upscattered ions but also possibly average energy ions as they approach the magrid radius.
In WB6, with it's positively charged magrid (more positive that the comparable escaping electron negative potential) The electron starts to slow as it passes to greater radii than the magrid, stops and reverses back through the same cusp. The important point is that this slowing and reversal and reacceleration occurs at some distance past the magrid due to the elecrons inertia. This is supposed to be a great enough distance that cusp plugging with cold ions is mitigated enough. Weather this is the case is uncertain , as it seems EMC2 may have dismissed this approach in WB8 and Mini B. Now they seem to be using high voltage Electron guns where the electrons are accelerated to high speeds much further from the magrid radius. The cold electrons are thus much further away and inverse square law effects dilute effects relative to the ion containing internal potential well. Unfortionatly this may also impede new electron injection due to mirroing external to the magrid midplane.
In this situation with a neutrally biased magrid, there is nothing to slow the electrons as they exit a cusp to greater radii, thus they will 'stick' to a B field line and loop around to another cusp, and possibly reenter the central space. The particulars are different, but the final result may be the same, except the cold electron in the cusps issue is ideally eliminated.
Both EMC2 and Lockheed may now be pursueing this course. How does it compare to WB6? The total electron confinement due to Wiffleball effect and recirculation may be ~ the same, or nearly so, and the ion confinement may actually be improved, perhaps significantly. Even id ion confinement is not improved, there may be other benifits- a better potential well geometrythat leads to better ion confluency/ central focus, and a deeper effective ion potential well.
Note that the external escaped electron (or mirrored injection electron) population reflects the flight times of the electrons(Voltage , KE, velocity) and current. There are ideally no ions. As such the Brillion limit precludes build up on much external pressure and thus high Beta in this region is impossible. The B field gradient is much shallower than the electron gyro radius so that there is no "sharp edge" for the electrons to reflect from. Normal gyro radius spiraling along a B field line is dominate- thus the looping along a line to enter a neighboring cusp. Because the exterior electrons are at relatively low pressure (and any ions that may be tagging along) the pressure/ ion density is low and thus fusion in this exterior region is minimal. It is all about recirculating the high energy electrons.
You could pursue the idea of adding additional layers but this introduces progessively more losses through ExB diffusion, etc. until it becomes dominate. You could not expand the system by adding layers- like an onion, though you might extend it linearly by stacking core regions end to end.
With electrons looping around field lines exterior to the magrid the magnetic lines become concave towards the plasma- primarily made up of electrons, but still plasma. This locally magnatized plasma would suffer from edge instabilities- macro instabilities . The saving grace is that the density of this electron plasma is much less than the density within the magrid core space, so the local edge instabilities are much less contributory. This does reenforce what I said above - the fusion (density dependent) is limited to the internal core. I think this distinguishes this approach from the FRC approach. Local B field reversal may apply, but not to the portion of the plasma that is contributing to fusion.
Magrid/ magrid is used as a discriptive term for the high Beta containing structure weather it is a Polywell, or a three ring linear arrangement of magnets.
Additional note: With the core concept surrounded by a combination of line and point cusps, fusion product ions would still naturally exit the system through a cusp before any significant thermalization. They are not electrostatically confined as are the fuel ions. This allows for direct conversion opportunities, and I think, precludes the possibility of ignition. The exception to this would be if the vacuum vessel wall was moved far enough away, the fusion ions might loop around and re enter the core region. Also, with stacked cores the fusion ions that escaped one core through the on axis point cusps would enter another core and bounce around for a while till another cusp was found, etc. In this case plasma heating by the fusion ions cold increase to significant levels. This could be beneficial or harmful depending on which considerations you are looking at (essentially self heating versus mono energetic preferences).
Dan Tibbets
To error is human... and I'm very human.
Re: cusps
Any plate that would repel the electrons would attract the ions. Recirc is the way to go. Indeed, they tried repeller plates on one EMC2 design (WB5?) but it didn't work for that exact reason.ohiovr wrote:If charged particles leaving the cusps is a problem why not just stick a highly negatively charged plate aligned to the corners to repel them back into the machine?
Re: cusps
Thanks. Sorry this has been posted before. I should have looked around.