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SQUID (superconducting quantum interference device)

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Nov25-13, 05:21 PM
P: 20
Hi all,
I am looking to do some magnetic measurements for some research (chemistry...) but I'm hoping to get an understanding of how a SQUID instrument works. I was wonder if anyone could give me a qualitative overview or if anyone know any resources without math-heavy explanations.
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Nov25-13, 08:39 PM
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PF Gold
P: 2,085
Wikipedia has a good, basic one-page description. Here's another site with good information
Since SQUID operation involves quantum mechanical concepts (electron wavefunctions, Cooper pairs and tunneling, e.g.), you can't get too deep without math.
Nov25-13, 11:36 PM
P: 20
Thanks. I've actually already taken a look at those.
I guess I just wanted some clarification on a few points since I don't have too strong of a physics background.
I understand that the squid detector has a superconducting ring with 2 Josephson junctions. The sample that the magnetic measurements are being taken for produces a magnetic field... which causes a change in magnetic flux through the superconducting ring. In response, the superconductor produces a screening current.
This (somehow??) results in the formation of a voltage across the Josephson junctions which can then be measured. What is the simplest explanation for how this happens?
Also is this voltage proportional to the magnetic field?? How exactly is information about the magnetic sample obtained from this voltage measurement.


Nov26-13, 08:41 AM
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PF Gold
ZapperZ's Avatar
P: 29,242
SQUID (superconducting quantum interference device)

This is where you need to backtrack and see if you have understood the Josephson effect, because that is something that's used in SQUIDs. It's difficult to explain this right in the middle because one needs to understand a lot of concepts that LEADS to the physics of SQUIDs.

You may want to read this article to start with:

It teaches from, in elementary form, the physics of superconductivity (especially phase coherence which is central to SQUIDs) leading to why you need Josephson junctions.


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