Saturday, November 15, 2014

YBCO Four Point Measurements: Lab Book 2014_11_15


I was back in the lab this morning.  I’m working on getting the four point measurement to work on the YBCO sample.  In the grand scheme of things, this is low priority, but it’s important to know that we can successfully make these measurements here before we have a large bucket of liquid helium evaporating with a sample inside.  Here’s what the four point probe measurement looked like:


There are still no conclusive results.  With any luck this is a consequence of me not being able to interpret the results more than a bad experimental setup.  The table below details the four point probe readings in ohms as the superconductor cools

Table of four point readings
Time
Resistance kohm
Comments
0
-0.35444
Negative reading is probably from swapped sense wires.
16
-0.36735
Immediately after nitrogen pour
59
-0.34466
Near minimum
101
-0.34359
Minimum immediately after new pour
280
-0.35815
Magnet in place beside superconductor in reservoir

I had expected more conclusive readings, a zero would have been nice for example. 


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