How do you charge a tokamak anyhow?

mdeminico · Post by **mdeminico** » Wed Nov 09, 2011 5:20 pm

If you wanted to charge a tokamak, how would you do it?

Here's what I'm envisioning...

You've got say 20 superconducting rings. That's all they are, rings. You attach them in a circular pattern so that if they were charged, the magnetic field would go around in the circle infintely (like any tokamak fusion reactor is designed).

Now, you've got 20 rings, all shaped to form a much larger ring.

Question is, how the *ahem* do you charge it? Besides running & jumping through the rings with a gigantic magnet, any ideas?

krenshala · Post by **krenshala** » Wed Nov 09, 2011 7:33 pm

Like any other superconducting ring -- external connections that can be isolated/disconnected once the main ring is brought up to the level you need it at.

mdeminico · Post by **mdeminico** » Wed Nov 09, 2011 8:34 pm

Yeah but external connections to what? Two wires running to each ring? That doesn't seem right to me, I'm not sure.

D Tibbets · Post by **D Tibbets** » Wed Nov 09, 2011 9:17 pm

The superconducting magnets are "charged" like any other electromagnet. Current is passed through the wires from a power source to ground. While powered, the leads are somehow quicky disconnected in a synchronized fashion. The elecrons then circulate without significant heating for very long times. There is no resistance and there is no place for the electrons to go except round and round through the wires/ ribbons.I recal someone said that a supermagnet may take ~ 100,000 years to drain provided it is kept cold enough.
I don't know if just hooking up a power supply will push the electrons (current)around the superconductor without a ground being temporarily connected. A capacitor would charge in this way, but this is a static charge. I think the current actually has to be flowing in a super conductor/ or regular copper electromagnet for the magnetic field to form.

Dan Tibbets

KitemanSA · Post by **KitemanSA** » Wed Nov 09, 2011 9:50 pm

If my sources are correct, superconducting magnets are "charged" by having a pair of non-superconducting leads to the superconducting coils with a shunt of uncooled superconductive material across them. When the current is at the desired level, the shunt is cooled to become a superconducting pathway between the leads and the current takes the path of least (in this case ZERO) resistance following the shunt bact to the incoming wire. And around and around and around it goes!

Neat, hinh?

ladajo · Post by **ladajo** » Wed Nov 09, 2011 10:05 pm

Yep, that is how it works. I had not posted on this earlier because I wasn't sure he was seriously asking this. Seemed like a JV question. Sorry.
Also, Famulus has even posted on doing so in his efforts, nice pictures and all.
A simple google of "superconducting shunt" should do the trick.

ladajo · Post by **ladajo** » Wed Nov 09, 2011 10:06 pm

Just for fun, I just googled "superconducting shunt" and it did do the trick.

Diogenes · Post by **Diogenes** » Thu Nov 10, 2011 2:47 am

I believe MSimon gets the prize for mentioning it first.

MSimon wrote:Tom I often wondered that too. Then I found out how. You have a shorted superconducting turn (or many turns) . You wrap a heater around a small section (doesn't need to be a big heater) an then feed in current on either side of the heater. Slowly ramp up the current. When it reaches the desired level turn off the heater. And now you have a charged up coil.

viewtopic.php?p=5523&highlight=ramp#5523

mdeminico · Post by **mdeminico** » Thu Nov 10, 2011 3:08 pm

Lajado, is it really that unbelievable that I would ask it? Maybe I'm missing something.

The reason I asked is because, like I said, connecting two non-superconducting (or heck, superconducting) wires to a ring at 2 different spots isn't necessarily going to make the current flow.

In the case of a toroidal SMES then, they do the same whenever they need power? Or is there another method? It just seems odd to me that that would be the method.

Wrapping a non-superconducting wire around the superconducting ring would (well, should) generate a magnetic field within the superconducting ring, except superconductors repel magnetic fields, so where does that field go? In theory, that magnetic field should also induce an eddy current within the ring, shouldn't it? Does that current induce and then stay within the ring?

KitemanSA · Post by **KitemanSA** » Thu Nov 10, 2011 3:36 pm

Diogenes wrote:I believe MSimon gets the prize for mentioning it first.

MSimon wrote:Tom I often wondered that too. Then I found out how. You have a shorted superconducting turn (or many turns) . You wrap a heater around a small section (doesn't need to be a big heater) an then feed in current on either side of the heater. Slowly ramp up the current. When it reaches the desired level turn off the heater. And now you have a charged up coil.

viewtopic.php?p=5523&highlight=ramp#5523

Hah! He has identified my source.

ladajo · Post by **ladajo** » Thu Nov 10, 2011 3:57 pm

mdeminico wrote:Lajado, is it really that unbelievable that I would ask it? Maybe I'm missing something.

The reason I asked is because, like I said, connecting two non-superconducting (or heck, superconducting) wires to a ring at 2 different spots isn't necessarily going to make the current flow.

In the case of a toroidal SMES then, they do the same whenever they need power? Or is there another method? It just seems odd to me that that would be the method.

Wrapping a non-superconducting wire around the superconducting ring would (well, should) generate a magnetic field within the superconducting ring, except superconductors repel magnetic fields, so where does that field go? In theory, that magnetic field should also induce an eddy current within the ring, shouldn't it? Does that current induce and then stay within the ring?

http://prometheusfusionperfection.com/2 ... t-success/