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Superconductor in RF module

Posted 05.08.2015, 12:28 GMT-4 RF & Microwave Engineering Version 4.4, Version 5.0, Version 5.1 4 Replies

Hengjiang Ren
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Hi all,

Is there a simple way to define a superconductor material and directly assign it to a boundary in emw simulations?

I saw some papers using PEC instead of a real superconductor but I'm not sure if there's any significant difference. I will simulate both in eigenfrequency and frequency domin.

If the easy way (just define a supercondutor material and assign to a boudry or just use PEC) is impossible or mot accurate, is there a hard way, maybe by add other physics?

Best,
Hengjiang
4 Replies Last Post 13.11.2015, 17:47 GMT-5
Robert Koslover Certified Consultant
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Posted: 9 years ago 05.08.2015, 20:59 GMT-4
Now that's an interesting question. If you only want to model the RF in the vicinity of a superconductor (e.g., to compute scattering) and don't really care about any material losses (e.g., you are not trying to compute the exact Q of a resonant cavity made of superconducting material), then you can probably just treat the superconductor as a PEC. But if you want to model the behavior of the superconducting material itself, perhaps even how its transition to non-superconducting depends on the frequency, amplitude, or other characteristics of the incident fields, then you'll need to include the superconducting physics in detail. As you probably already know, superconductors are not actually "perfect" at RF frequencies, even for weak applied RF fields. See, for example, en.wikipedia.org/wiki/Superconducting_radio_frequency .
Note: that link may give you some ideas about how to model the effective resistivity. Anyway, I encourage you to post more to this forum to share what you learn, if you work it all out successfully. Meanwhile, a note to others: Have you ever tried to model the detailed physics of superconductors, in the RF regime, using Comsol Multiphysics?

Now that's an interesting question. If you only want to model the RF in the vicinity of a superconductor (e.g., to compute scattering) and don't really care about any material losses (e.g., you are not trying to compute the exact Q of a resonant cavity made of superconducting material), then you can probably just treat the superconductor as a PEC. But if you want to model the behavior of the superconducting material itself, perhaps even how its transition to non-superconducting depends on the frequency, amplitude, or other characteristics of the incident fields, then you'll need to include the superconducting physics in detail. As you probably already know, superconductors are not actually "perfect" at RF frequencies, even for weak applied RF fields. See, for example, https://en.wikipedia.org/wiki/Superconducting_radio_frequency . Note: that link may give you some ideas about how to model the effective resistivity. Anyway, I encourage you to post more to this forum to share what you learn, if you work it all out successfully. Meanwhile, a note to others: Have you ever tried to model the detailed physics of superconductors, in the RF regime, using Comsol Multiphysics?
Hengjiang Ren
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Posted: 9 years ago 13.08.2015, 01:01 GMT-4
Thanks for your reply. And your guessing is right, I'm exactly trying to compute the exact Q of a resonant cavity made of superconducting material.

I read several papers and still having no idea how to model a supercondutor in EM field.

Hope someone who did this kind of simulation can give some hint.
Thanks for your reply. And your guessing is right, I'm exactly trying to compute the exact Q of a resonant cavity made of superconducting material. I read several papers and still having no idea how to model a supercondutor in EM field. Hope someone who did this kind of simulation can give some hint.
Yi Xie
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Posted: 9 years ago 13.11.2015, 17:44 GMT-5
For the exact Q of a resonant cavity (even if it's a superconducting cavity), please refer to COMSOL example "Computing Q-factors and resonant frequencies of cavity resonators". You don't need to model superconductor itself, just treat it as perfect conductor.




Thanks for your reply. And your guessing is right, I'm exactly trying to compute the exact Q of a resonant cavity made of superconducting material.

I read several papers and still having no idea how to model a supercondutor in EM field.

Hope someone who did this kind of simulation can give some hint.


For the exact Q of a resonant cavity (even if it's a superconducting cavity), please refer to COMSOL example "Computing Q-factors and resonant frequencies of cavity resonators". You don't need to model superconductor itself, just treat it as perfect conductor. [QUOTE] Thanks for your reply. And your guessing is right, I'm exactly trying to compute the exact Q of a resonant cavity made of superconducting material. I read several papers and still having no idea how to model a supercondutor in EM field. Hope someone who did this kind of simulation can give some hint. [/QUOTE]
Yi Xie
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Posted: 9 years ago 13.11.2015, 17:47 GMT-5
To model the detailed physics of superconductors, in the RF regime, using Comsol Multiphysics, we should solve time dependent Eliashberg equations.
To model the detailed physics of superconductors, in the RF regime, using Comsol Multiphysics, we should solve time dependent Eliashberg equations.

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