### Lab Book 2014_05_12 Sample Frame Design and Missing Liquid Nitrogen

Lab Book 2014_05_12     Hamilton Carter

To Do this week in no particular order:
1.       Leak detect the glass and fiberglass Dewars
2.       Check on the availability of the can crusher
3.       Make drawings for sample stage
4.       Check for existing materials that might be used for the sample stage
5.       Find 240 V 3 phase outlet for the magnet power supply
6.       Get the power cord for the magnet supply
7.       Modify lab table
8.       Move magnet
9.       Continue review of the Nikolic paper concentrating on equations 8 - 11
10.   Continue work on the Thomas precession paper
11.   Check on replacement filters for the leak detector
12.   Move and test NaI detector
13.   Characterize source in Dewar with NaI detector
14.   Magnet test YBCO sample
15.   Find a source for x-ray film and developing

Done Today
Reseated the top and bottom seals on the fiberglass Dewar.  Spent some time brainstorming how to mount the sample in the fiberglass Dewar.

Dewar Design Decision:
The Dewar will not be cut or modified to house a larger sample than can be inserted through the neck.  The sample will be situated in the tail of the Dewar.

Brainstorming sketching.  The coil will be oriented with its axis of rotation directed horizontally.  The coil will be built into a curved fiberglass sample holder that will both reinforce the bottom of the coil and hold the sample.

Dewar Filling
Filled the liquid nitrogen storage Dewar. Empty it weighs 76 pounds and full it weighs in at 173 pounds.  Strangely, I’m unable to figure out how to get the liquid nitrogen to exit the Dewar today.  Opening the liquid or the vent valves produces no results, (haven’t tried both yet).  The pressure gauge reads 0 psi.  The Dewar is still slightly cold to the touch though and feels still feels heavier.

### Cool Math Tricks: Deriving the Divergence, (Del or Nabla) into New (Cylindrical) Coordinate Systems

The following is a pretty lengthy procedure, but converting the divergence, (nabla, del) operator between coordinate systems comes up pretty often. While there are tables for converting between common coordinate systems, there seem to be fewer explanations of the procedure for deriving the conversion, so here goes!

What do we actually want?

To convert the Cartesian nabla

to the nabla for another coordinate system, say… cylindrical coordinates.

What we’ll need:

1. The Cartesian Nabla:

2. A set of equations relating the Cartesian coordinates to cylindrical coordinates:

3. A set of equations relating the Cartesian basis vectors to the basis vectors of the new coordinate system:

How to do it:

Use the chain rule for differentiation to convert the derivatives with respect to the Cartesian variables to derivatives with respect to the cylindrical variables.

The chain rule can be used to convert a differential operator in terms of one variable into a series of differential operators in terms of othe…

### Lost Phone

We were incredibly lucky to have both been in university settings when our kids were born.  When No. 1 arrived, we were both still grad students.  Not long after No. 2 arrived, (about 10 days to be exact), mom-person defended her dissertation and gained the appellation prependage Dr.

While there are lots of perks attendant to grad school, not the least of them phenomenal health insurance, that’s not the one that’s come to mind for me just now.  The one I’m most grateful for at the moment with respect to our kids was the opportunities for sheer independence.  Most days, we’d meet for lunch on the quad of whatever university we were hanging out at at the time, (physics research requires a bit of travel), to eat lunch.  During those lunches, the kids could crawl, toddle, or jog off into the distance.  There were no roads, and therefore no cars.  And, I realize now with a certain wistful bliss I had no knowledge of at the time, there were also very few people at hand that new what a baby…

### Lab Book 2014_07_10 More NaI Characterization

Summary: Much more plunking around with the NaI detector and sources today.  A Pb shield was built to eliminate cosmic ray muons as well as potassium 40 radiation from the concreted building.  The spectra are much cleaner, but still don't have the count rates or distinctive peaks that are expected.
New to the experiment?  Scroll to the bottom to see background and get caught up.
Lab Book Threshold for the QVT is currently set at -1.49 volts.  Remember to divide this by 100 to get the actual threshold voltage. A new spectrum recording the lines of all three sources, Cs 137, Co 60, and Sr 90, was started at approximately 10:55. Took data for about an hour.
Started the Cs 137 only spectrum at about 11:55 AM

Here’s the no-source background from yesterday
In comparison, here’s the 3 source spectrum from this morning.

The three source spectrum shows peak structure not exhibited by the background alone. I forgot to take scope pictures of the Cs137 run. I do however, have the printout, and…