Monday, June 9, 2014

Lab Book 2014_06_09 Fixing the Superconducting Quench Yoke Magnet

Scroll to the bottom for background on the experiment.

Checked that the pole faces of the yoke magnet retract fully leaving enough room for the glass Dewar.  The poles do retract far enough, but there is a trick to it.  The rotator that advances and retracts the pole piece should have two metal collars associated with it.  On the side I initially tried to adjust, one of the collars was missing and the pole would not move.  When I moved the second collar to that side of the magnet, the pole piece moved after applying a little bit of force


Here's how it works  The collar the handle protudes from is threaded on the inside.  It turns on the threads that are visible and are attached to the pole piece.  If the second collar is in place, then the torque created by the handle is applied to the threads of the pole piece and it slides back and forth through the treads of the handled piece along a small rail at the bottom of the threaded pole.  A screwing motion on the handled collar creates a sliding motion of the pole piece, assuming the second collar is in place.

The magnet with the polished pole faces removed and the poles fully retracted


I subsequently removed the pole faces. I may re-install them if the poles can be retracted far enough to allow the polished pole pieces to be used with a sufficient gap still available.  Detail of pole faces.

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 

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