Monday, January 12, 2015

Superconductor Bound: Lab Book 01/12/2015

If you're new to the experiment and need background, scroll down.

I’m trying out the concept for the qualitative quench detector with a YBCO sample.  The prototype coils were wrapped directly on the YBCO sample. 

The coils are constructed with manget wire.  The insulation on the ends of each coil was scraped off using a razor blade.  The brown material is just dense poster-board stock that provides a mounting frame for the coils.

Without cooling the sample, (so that it remained in its normal state), an oscillating current was driven through the primary coil and read through the secondary. 

The results were the same as might be expected with air core coils since the superconducting sample is not diamagnetic or ferromagnetic. 



Tomorrow the same experiment will be run again with the sample in its superconducting state.  I expect to see a different x-y plot due to the superconducting samples expulsion of magnetic fields in its interior.  The resulting plot might not be differently shaped, but should have a different slope, and different maximal points.
It’s doubtful that the oscillator shown can generate enough current to quench the superconductor.  If it cannot, then the entire sample assembly will be placed between the poles of the H magnet.  The larger fields available there should cause the superconductor to quench.  The resulting pattern will be recorded.  Hopefully the quenched and unquenched patterns will be significantly different.  In the best case, we should be able to get a hysteresis curve using the oscillator.



Background
Hirsch's theory of hole superconductivity proposes a new BCS-compatible model of Cooper pair formation when superconducting materials phase transition from their normal to their superconducting state[1].  One of the experimentally verifiable predictions of his theory is that when a superconductor rapidly transitions, (quenches), back to its normal state, it will emit x-rays, (colloquially referred to here as H-rays because it's Hirsch's theory).

A superconductor can be rapidly transitioned back to its normal state by placing it in a strong magnetic field.  My experiment will look for H-rays emitted by both a Pb and a YBCO superconductor when it is quenched by a strong magnetic field.
This series of articles chronicles both the experimental lab work and the theory work that’s going into completing the experiment.

The lab book entries in this series detail the preparation and execution of this experiment… mostly.  I also have a few theory projects involving special relativity and quantum field theory.  Occasionally, they appear in these pages.

Call for Input
If you have any ideas, questions, or comments, they're very welcome!

References
1.  Hirsch, J. E., “Pair production and ionizing radiation from superconductors”, http://arxiv.org/abs/cond-mat/0508529

No comments: