Re: High temperature superconductors and radiation screening effect?


conundrum wrote:

I was reading the latest article about the latest research on magnesium
diboride with the possibility of using similar materials to achieve Tcs
of above 200K, and suddenly had a thought.

It has been well established that superconductors exclude a magnetic
field, an effect which extends into the realm of radio waves and
visible/infrared light.

Yes, it's called 'diamagnetism' and in addition to superconductors,
it is common to all conducting materials at high frequencies.

So it occurs to me that a simple method of detecting candidate
materials in a bulk sample would be to affix said sample to a Peltier
module with a temperature sensor, with a radio emitter (possibly as
simple as a Gunn diode) and detector assembly to detect changes in
transmission and/or reflection as well as interference patterns.

The extension of diamagnetism to low frequencies (and DC) is uniquely
strong
in superconductors; at RF, the superconductor behavior is not unique.
The history of TTF-TCNQ is a case example that might be worth looking
into;
as long as folk were making AC measurements, it looked like a
superconductor.
It wasn't one. That was around the early 1970s, as I recall.

.

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