Sunday, June 22, 2014

Meanwhile, in the lab... Dewar Moves and Leaky Vacuum Pumps

Lab Book 2014_06_20     Hamilton Carter

New to the lab book?  Scroll to the bottom for background and a summary of the experiment.

Pulling the Dewar from the Table
The spray Styrofoam was shaved off the Dewar this morning revealing that the Dewar had originally been installed on a piece of regular Styrofoam and the spray coating was added later



The plan is to peel away as much of the spray foam as is practicable, and then do a two person lift of the Dewar out of the table.  The Dewar will be immediately placed in a padded box.
The Dewar was successfully removed!  Next, I’ll remove the shelf and put the magnet in place.  There’s one cooling tube that was knocked off the magnet as it turns out, so that will have to be fixed.

Vacuum Pump Down!
The leak detector vacuum pump appears to be broken.  The reading on it is a much worse vacuum than from the auxiliary one on the lower shelf of the cart


Leak Detector Pump
Auxiliary Pump

The pump was tested using a thermocouple gauge system shown below.  The actual vacuum detector has a blue label is attached to the OCF brass flange.  The flange isn’t visible as it is enclosed in the larger black plastic clamp.




The detector cable plugs into a readout box:


The flange was attached directly to the mechanical roughing pump that was being tested by first detaching the hose between the mechanical and the diffusion pump at the diffusion pump end and then inserting the assemblage shown attached to the gauge above into the hose as shown below



I’m wondering how much work it would take to put our thermocouple vacuum meter on an Arduino data capture system, hence the digital voltmeter in the second picture to check the voltages that are available and should be somehow related to the vacuum reading on the meter.

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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