Thursday, July 24, 2014

PMT Rebuild and Can Crusher Code Progress: Lab Book 2014_07_24

The workbench before starting this morning.

Lab Book 2014_07_24     Hamilton Carter

Most of the day was spent building a new base for the PMT on the NaI detector.  I found almost all the necessary capacitors and was able to get the only size I couldn’t find by combining two other capacitors in parallel.  Only the connections to the coaxial connectors remain to be done.  The can crusher code port is progressing.  The initial implement of the function that models the movement of the can is complete.  There’s a bug in it that needs to be fixed.

Rebuilding the PMT
Found all the capacitors that will be required to build up the new base.
Should you want to rebuild the socket again, look for a box like this.

This is the portion of the circuit that has capacitors.  The capacitors that are going to be used have been laid out on the schematic as a visual check.

Here’s the schematic for the suggested PMT base circuit from the RCA tube manual[1].

These are all ceramic disc capacitors.  The older ones actually feel scratchy between my fingers, just like ceramic.  Go figure.  It’s cool that they don’t have the plasticized coating that’s on the others.
This is the new base with only a few resistors installed. the light brown insert in the middle is the base of the PMT tube.  This is a test fit to see how low components can be placed without interfering with the PMT tube.

Here’s the new base with all the parts installed.  All that remains is attaching the last few leads to the coaxial connectors.

Can Crusher Code[2]
The move_can function was implemented.  At the moment, it conks out after 210 steps or so.  The velocity of the imploding can wall doesn’t ever seem to change.  The error occurs in the mutual inductance function  I’m guessing there’s a bug in move_can and the mutual inductance function is giving up because the can has moved to an unphysical configuration, something like having a negative radius. A quick check has revealed that some of the can radii are going negative and others are getting huge on the order of ten to the eighteenth power.
1.  RCA 45xx PMT manaual

2.  Can crushe code on github

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”, 

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