I would love to get one of Ed Sines copper/ceramic magnets to see how it holds up. I've wondered how they handle extreme heating myself. It sounds destructive. But he really packs in the copper, with very little ceramic in between.
I suspect minimum spacing may depend on insulating fibers or whiskers either around the conductors or in the ceramic material.
If you can get these things tight enough, cracks may not matter so much. If the material is all contained, where could it go? But if it pulverizes to powder, and there are no fibers to keep things from moving around, the end will no doubt be as sad as failed varnish on conventional magnet wire windings.
He seemed quite sure he could build magrid magnets capable of a Tesla or more, and I'd love to see it. I just don't want to underwrite the warranty.
Tungsten coils?
Hah-hah! 
Don't pick me, the most challenging device I ever built was a potato gun!
Hmm, I remembered MSImon having dismissed superconductors as impractical for a small machine size. Looking back, it seems like I misremembered. Apparently it didn't have to do with scale, so much as economics perhaps, and the fact that if the reactor used D-D, the neutrons would rapidly foul the magnet. I can't find out about the economics myself, but it looks like American Superconductors has a pretty decent HTS that wouldn't need helium, just LN2. So it might be an option, depending on price.
I guess one other consideration is that it'd be tough to get a continuous (not pulsed) HV power supply to charge the magrid, and there's not much point having continuous magnet capability and only pulsed power.
Don't pick me, the most challenging device I ever built was a potato gun! Hmm, I remembered MSImon having dismissed superconductors as impractical for a small machine size. Looking back, it seems like I misremembered. Apparently it didn't have to do with scale, so much as economics perhaps, and the fact that if the reactor used D-D, the neutrons would rapidly foul the magnet. I can't find out about the economics myself, but it looks like American Superconductors has a pretty decent HTS that wouldn't need helium, just LN2. So it might be an option, depending on price.
I guess one other consideration is that it'd be tough to get a continuous (not pulsed) HV power supply to charge the magrid, and there's not much point having continuous magnet capability and only pulsed power.
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ravingdave
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Tom Ligon wrote:Where are you buying your liquid helium? I think that's cheaper than we can buy liquid helium in bulk, for our big tank!
Otherwise, a clever approach. I would not discount the possibility of doing it with other superconductors over copper, or for that matter, high temperature superconducting powder IN copper tubing, with an outer tube for the LN2. You might even get away with an MPG all-tube magrid.
I've never been any good at figuring out how to flash superconducting coils, eliminating the external path. As a practical matter, how would an amateur setup do that?
I don't remeber where I found that quote but I did post the link for it in
the NasaSpaceFlight forum when I discussed this idea there.
As far as starting up a superconducting magnent, I asked that very question myself ! I believe MSimon was the one who posted the answer.
You cool your superconductor to superconducting temperature, then heat a section of the coil. Apply a current across the now resistive section, then turn off the heater allowing that section to cool to superconducting temperature and the magnent will then maintain that current flow indefinitely.
From the reading I did at the time I recall there were many services specializing in starting and quenching superconducting magnents for hospitals and researchers. Apparently the MRI magnents use some small
quantity of liquid helium daily in conjunction with a cryostat to maintain
their magnents operating for years. (or until they need to service the machine)
As near as I can tell the process is apparently routine.
David
" Sir James Dewar is a better man than you are... Which of you asses can liquify gasses ? "
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ravingdave
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I believe Tom Ligon mentioned a problem with Alumina outgassing and contaminating the vacum. Of course there are other usable ceramics, but Alumina seems to be the workhorse when it comes to ceramics.vernes wrote: I was actually thinking more of somethying a bit more solid.
That's why I mentioned the ceramic beads as a way to position the windings before casting the whole coil into a solid block of ceramic clay.
I'm not familair with the strength of a semisolid block of ceramic, but that's for another study entirely. The beads might create possible fracture-lines because they don't merge well with the casted clay.
Yeah, I was pretty enthusiastic myself, but too often life gets in the way. I do believe the project is within the grasp of amateurs, but they will have to be fairly well off or highly inventive and resourceful or both. If you want to tackle a project like this, it would seem to me that the most difficult problem is creating and maintaining a suitable vacum. From what i've been reading the necessary equipment to maintain a high vacum is very expensive, but i'm thinking it might be obtainable surplus.vernes wrote: I want to build a demonstration (found out a demo reactor is somethingactually) reactor one day.
David
I contacted a company in Europe a while back that was making 1 KM lengths of MgB superconductors. I did some calculations and found that if it could be made with four or five nines B11 it would have fair to poor neutron resistance. Which actually is not bad. Put a water jacket around it and a thin layer of B10 (a few mm) and it would be pretty robust against neutron flux.
Here is a nice one:
http://www.energetics.com/meetings/ohio ... tomsic.pdf
http://www.hypertechresearch.com/index.html
http://www.energetics.com/meetings/wire ... tomsic.pdf
Here is a nice one:
http://www.energetics.com/meetings/ohio ... tomsic.pdf
http://www.hypertechresearch.com/index.html
http://www.energetics.com/meetings/wire ... tomsic.pdf
Last edited by MSimon on Tue May 20, 2008 10:19 pm, edited 2 times in total.
Engineering is the art of making what you want from what you can get at a profit.
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ravingdave
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It's my understanding that High Temperature Superconductors are difficult to fabricate and do not lend themselves to being wound on a coilSolo wrote:Ok, so what's preventing the use of superconducting coils in a set-up on the scale that Dr. Nebel is working with? There are superconductors that need only LN2, not helium. In a reactor the size we are talking about, all you'd need would be a (single-turn?) superconducting coil inside a cooling jacket that would function also as the magrid's toroidal surface. No need for vacuum insulation becasue there won't be any real plasma heating on this scale. Plus, as long as it takes to cool the coils in WB-7 after a run, it seems that the coils are well-insulated thermally, so there won't be much cooling power needed. And of course, no ohmic heating from the coil! In fact, it seems to me like you'd hardly need a circulating coolant system; just do like the LDX and cool the whole thing down with a shot of LN2 and run your experiement! Heck, you could probably get several runs on power-up of the coil.
form, or if they are windable they need a large bend radius. Apart from that their current density is much less than that of the old style "conventional" Superconductor.
But yeah, everything else ought to be as you say. With a high vacum their shouldn't be a significan heat load on the coils unless fusion occurs. If sufficient fusion occurs for magnent cooling to be a problem then the experiment is a success ! I like the idea of Lead coated copper tubing and
helium because it should be very robust.
Tom Ligon mentioned using powdered High temperature superconducting material inside of copper tubing. That has the advantage of operating at liquid nitrogen temperatures but it won't attain the current density of the old fashion superconductors. However the higher temperature is a REALLY big advantage, and I bet the current density is plenty high enough.
David
ravingdave wrote:It's my understanding that High Temperature Superconductors are difficult to fabricate and do not lend themselves to being wound on a coilSolo wrote:Ok, so what's preventing the use of superconducting coils in a set-up on the scale that Dr. Nebel is working with? There are superconductors that need only LN2, not helium. In a reactor the size we are talking about, all you'd need would be a (single-turn?) superconducting coil inside a cooling jacket that would function also as the magrid's toroidal surface. No need for vacuum insulation becasue there won't be any real plasma heating on this scale. Plus, as long as it takes to cool the coils in WB-7 after a run, it seems that the coils are well-insulated thermally, so there won't be much cooling power needed. And of course, no ohmic heating from the coil! In fact, it seems to me like you'd hardly need a circulating coolant system; just do like the LDX and cool the whole thing down with a shot of LN2 and run your experiement! Heck, you could probably get several runs on power-up of the coil.
form, or if they are windable they need a large bend radius. Apart from that their current density is much less than that of the old style "conventional" Superconductor.
But yeah, everything else ought to be as you say. With a high vacum their shouldn't be a significan heat load on the coils unless fusion occurs. If sufficient fusion occurs for magnent cooling to be a problem then the experiment is a success ! I like the idea of Lead coated copper tubing and
helium because it should be very robust.
Tom Ligon mentioned using powdered High temperature superconducting material inside of copper tubing. That has the advantage of operating at liquid nitrogen temperatures but it won't attain the current density of the old fashion superconductors. However the higher temperature is a REALLY big advantage, and I bet the current density is plenty high enough.
David
Actually MgB is very "metalic" and can make tight bends. At 20K you can do 2T coils and at 10K about 5T to 8 T.
Its main advantage is that it can handle about 1E18 or 2E18 n/cm^2 total flux before it becomes useless. Better than most other superconductors.
Engineering is the art of making what you want from what you can get at a profit.
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ravingdave
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Why would it be tough to get a continuous high voltage supply ? MSimon came up with a multiphase triac controled (modulated) variable supplySolo wrote:Hah-hah!
Hmm, I remembered MSImon having dismissed superconductors as impractical for a small machine size. Looking back, it seems like I misremembered. Apparently it didn't have to do with scale, so much as economics perhaps, and the fact that if the reactor used D-D, the neutrons would rapidly foul the magnet. I can't find out about the economics myself, but it looks like American Superconductors has a pretty decent HTS that wouldn't need helium, just LN2. So it might be an option, depending on price.
I guess one other consideration is that it'd be tough to get a continuous (not pulsed) HV power supply to charge the magrid, and there's not much point having continuous magnet capability and only pulsed power.
the design of which ought to be scalable to whatever voltage and current are required. Of course you might have to move the operation next to a substation to get the input voltage you want, but i'm pretty sure 12 kv is readily available .
Even if you had to work with 4800, you could use voltage multipliers
to scale the voltage up high enough, and with enough phases, ripple wouldn't be that big of a problem.
If I recall properly, when Tom Ligon was working on PXL1 I believe he was using up to 12 KV with a 2 amp surge of drive current on the electron gun.
I think a high powered continuous power supply is achievable for a reasonable cost to build, but I would be nervous playing with it.
David
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ravingdave
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Awsome ! How much does it cost ?MSimon wrote:ravingdave wrote:
It's my understanding that High Temperature Superconductors are difficult to fabricate and do not lend themselves to being wound on a coil
form, or if they are windable they need a large bend radius. Apart from that their current density is much less than that of the old style "conventional" Superconductor.
But yeah, everything else ought to be as you say. With a high vacum their shouldn't be a significan heat load on the coils unless fusion occurs. If sufficient fusion occurs for magnent cooling to be a problem then the experiment is a success ! I like the idea of Lead coated copper tubing and
helium because it should be very robust.
Tom Ligon mentioned using powdered High temperature superconducting material inside of copper tubing. That has the advantage of operating at liquid nitrogen temperatures but it won't attain the current density of the old fashion superconductors. However the higher temperature is a REALLY big advantage, and I bet the current density is plenty high enough.
David
Actually MgB is very "metalic" and can make tight bends. At 20K you can do 2T coils and at 10K about 5T to 8 T.
Its main advantage is that it can handle about 1E18 or 2E18 n/cm^2 total flux before it becomes useless. Better than most other superconductors.
David
Dave,
With typical semiconductors these days operating voltage would be 500 to 600 V. SCR based converters to go from 3 ph AC to DC at around 2 MW are not uncommon.
10 KW / converter seems optimum in terms of losses you might be able to push that to 20 KW without too much strain.
"Primaries" in parallel. Secondaries in series for a single string. Parallel strings for more secondary current.
Run the converters at 30 KHz with the switch on time staggered and with an 80 converter string your input and output ripple looks like 2.4 MHz give or take. Easy (relatively) to filter.
With typical semiconductors these days operating voltage would be 500 to 600 V. SCR based converters to go from 3 ph AC to DC at around 2 MW are not uncommon.
10 KW / converter seems optimum in terms of losses you might be able to push that to 20 KW without too much strain.
"Primaries" in parallel. Secondaries in series for a single string. Parallel strings for more secondary current.
Run the converters at 30 KHz with the switch on time staggered and with an 80 converter string your input and output ripple looks like 2.4 MHz give or take. Easy (relatively) to filter.
Engineering is the art of making what you want from what you can get at a profit.
http://outgassing.nasa.gov/ravingdave wrote:I believe Tom Ligon mentioned a problem with Alumina outgassing and contaminating the vacum. Of course there are other usable ceramics, but Alumina seems to be the workhorse when it comes to ceramics.
http://www.ee.ualberta.ca/~schmaus/vacf/outgas.html
http://esmat.esa.int/Services/outgassin ... _data.html
Now I know where to find the data, I now have to learn how to interpret it.
Actually, the getting there I find fun and entertaining.If you want to tackle a project like this, ...
...From what i've been reading the necessary equipment to maintain a high vacum is very expensive, but i'm thinking it might be obtainable surplus.
And the vacuum chamber part, wouldn't a university be willing to stick a test-ready contraption into a vacuum chamber for a decent price?
They bought the thing, and if it's doing nothing, it's actually eating money just by taking in space.
The vast majority of ceramics contain no ferrous material, so there is no magnetic interaction between ceramics and magnets. Ceramics are mostly insulators as well, so there is little interaction (other than normal dielectric effects) with electric fields.vernes wrote:Does anyone know if ceramics has a blocking effect on magnetic fields?
Someone told me concrete is used to block radiation, which makes me wonder what ceramics does with magnetic fields.
However, when you lower the temperature of some specific ceramics, they become superconductors. Then they have a lot of ability to interact with both electric and magnetic fields.
Dave,
Its current cost is less than copper for equivalent current carrying capacity.
And that is in low volume production. Once the production rates get up it will cost much less.
For our purposes it is an ideal material. You extract the B10 and use it as part of the shielding - plus a B11 only MgB SC should add another order of magnitude or more to dose toleration. It does require dropping the operating temp 1 or 2 deg K.
Its current cost is less than copper for equivalent current carrying capacity.
And that is in low volume production. Once the production rates get up it will cost much less.
For our purposes it is an ideal material. You extract the B10 and use it as part of the shielding - plus a B11 only MgB SC should add another order of magnitude or more to dose toleration. It does require dropping the operating temp 1 or 2 deg K.
Engineering is the art of making what you want from what you can get at a profit.
Hi, I'm the Frog. I'm new too.
I have never posted anything anywhere before so please excuse my clumbsy style here. I have been intrigued by the idea of incorporating ceremics in this design.
The thought has occured to me that the use of non-ferous ceramic cladding mounted on independent suspensions acting as the coil housings could provide some answers and many possabilities. Housing the coils and suspending them independently from oneanother reduces arching potential, provides thermol shielding and the possabilities for coolant pathways and power supply routing without structural interface between the coils.
Let me illustrate by using the TALK-POLYWELL logo. Imagine the coils, as they are shown, clad in enough high-strength thermol ceramic to just fill the space between the coils. Now imagine each cerammic clad coil suspended, or supported, by its own external suspension mechanism. Such a system could provide the protection against buffeting, thermol and dynamic, as well as potential for a system for energy recovery, coolant transport, and power supply.
For WB7 I'm sure that these ideas wouldn't be practical. But for future design considerations I believe that this is an option with potential. Advanced Ceramics Research has done work for NASA in this area and may be a helpful resourse.
Well I hope my blather is somthing more than just taking up this space and time. What do you think? Anything to this?
I have never posted anything anywhere before so please excuse my clumbsy style here. I have been intrigued by the idea of incorporating ceremics in this design.
The thought has occured to me that the use of non-ferous ceramic cladding mounted on independent suspensions acting as the coil housings could provide some answers and many possabilities. Housing the coils and suspending them independently from oneanother reduces arching potential, provides thermol shielding and the possabilities for coolant pathways and power supply routing without structural interface between the coils.
Let me illustrate by using the TALK-POLYWELL logo. Imagine the coils, as they are shown, clad in enough high-strength thermol ceramic to just fill the space between the coils. Now imagine each cerammic clad coil suspended, or supported, by its own external suspension mechanism. Such a system could provide the protection against buffeting, thermol and dynamic, as well as potential for a system for energy recovery, coolant transport, and power supply.
For WB7 I'm sure that these ideas wouldn't be practical. But for future design considerations I believe that this is an option with potential. Advanced Ceramics Research has done work for NASA in this area and may be a helpful resourse.
Well I hope my blather is somthing more than just taking up this space and time. What do you think? Anything to this?