Sunday, July 20, 2014

Cs 137 Spectrum at Last? Lab Book 2014_07_19

Summary:  I'm still checking and re-checking the NaI detector.  I've yet to get a reliable spectrum out of it, but last night's run at least has distinguishable peaks.  The company that made our detector 50 years ago believes that we probably do have an RCA 45xx series photomultiplier tube which would mean that the 2400 V bias I have to drive the tube at to get  a signal is actually OK.  The 45xx series has a maximum bias voltage of 2500 V.

If you're new to the experiment, scroll to the bottom for background.

The Cs137 spectra that was started at 3:13 PM yesterday was ended today at about 9:50 AM.  The photo of the spectrum follows

There are a number of oddly shaped peaks that may ben been created by channel overflow now that I think about it.  The data was printed and the linear chart is shown below:

If I ‘fix’ the supposed channel overflow by adding the value of the full register back in to the count, on the first step I get:

Which fixes the two peaks to the right, but not the one to the left.
Working under the assumption that the register overflowed twice in this region, I added in two full register counts to these data points and wound up with

We may be able to assume that the two non-plateau peaks are the two peaks associated with Cs 137.  I’m running a Co60 spectrum now and should have results by the end of the day.

Here’s a picture of the Cs137 sectrum again for reference.

Hunh, Cs137 only has one noticeable peak, or at lest one peak that should be larger than all the rest.  I've been told that our detector shouldn't be able to see the 32 keV line to the left of the graph.

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!

1.  Hirsch, J. E., “Pair production and ionizing radiation from superconductors”, http

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