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Coercivity of Superconductor

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harmonizedmot
#1
Feb21-12, 03:02 PM
P: 2
I am modeling a magnetic coil array in Opera v15. My current project uses a CosΘ Coil inside a Metglas cylinder (Ferromagnetic) inside a Pb cylinder (Superconducting) at 4ēK. The method used to specify the a material in Opera is to specify the Coercivity and Relative Permeability.

If I had a hysteresis curve, then the coercivity would be the distance along the H axis from the origin to the leftmost intersection point of the curve. Correct? I need to define the coercivity of the Pb Shield for the program, which is superconducting. But the hysteresis plot for a superconductor doesn't really make sense to me. In my mind I see a very thin line and so I think the coercivity would be extremely small. Perhaps this question is silly (or I'm just a grad student) but I find that when I talk to Professors about it, they seem to want to avoid the topic.

I've researched for many hours online and haven't found what I am looking for.

Does this analysis seem correct? Are there any references online I could look at to help clarify this topic?
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f95toli
#2
Feb21-12, 03:38 PM
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i don't think you can ever really talk about coercivity for superconducting Pb.
Yes, you can probably make plots of something that suggest that you could define something similar, but remember that Pb is type II meaning the situation is quite tricky: the curve would look different depending on whether or not teh Pb was superconducting when the field was applied, the strength of the field compared to Bv1 etc.

In short. It is all quite messy.

I've never used Opera. Does the program explicitly allow you to defined superconducting screens?
harmonizedmot
#3
Feb21-12, 05:17 PM
P: 2
Yeah, the concept of coercivity in this situation does seem out of place.

The experiment requires a B field of around 100mG (less than the Earth's), and I'm not even sure what the plan is to achieve that, considering Flux Pinning, but that is a whole other subject. We're going to turn on the field after it is superconducting because we want tangential fields from the coil at the SC surface.

Quote Quote by f95toli View Post
Does the program explicitly allow you to defined superconducting screens?
To define a material you may set it as Linear or Non-Linear and Isotropic, Packed or Anisotropic. Then if you select Non-Linear you may define a BH curve with up to 50 points or so. And for Anisotropic materials you may use tables or functions to define values. It has a nice user variable utility and the scripting language is rather easy to use. But there isn't a "Superconductor" setting or button. I've searched it's literature thoroughly and it does have a quench simulator but that is about as much superconductor specific coding the program has.


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