### Lab Book 2014_05_20 Dewars and Outlets

Lab Book 2014_05_20     Hamilton Carter
Summary
The fiberglass Dewar vacuum held.  The vacuum inlet was plugged to prevent any possible leaks there, and it was stored.  A 480 V three phase outlet for the magnet power supply was located.

4:30 AM Liquid Nitrogen Trap Refilling

Refilled the liquid nitrogen trap that prevents oil vapor from the diffusion pump from migrating opposite the intended vacuum flow into the Dewar’s vacuum jacket.  The liquid nitrogen condenses the oil vapor in the bottom of the small container, (the trap), that it cools.

The trap took two and a half cups of liquid nitrogen to refill.  The vacuum and leak detector readings before and after the fill are shown below.
There was no noticeable improvement in the vacuum and leak readings before and after the Dewar refill.  This makes sense because the Dewar still had liquid nitrogen and was performing its intended function.

Vacuum and leak readings throughout the day
 Time Vacuum Leak 4:40 4:46 11:09 12:40 15:44

NOTE:  The glass Dewar is at room pressure and can be safely moved.
It’s not possible to check that the vacuum inlet valve doesn’t leak.  To prevent a possible lek even when the valve is shut, a plug was inserted over the inlet valve.

I located a three phase 208 v plug for the magnet power supply.  I need to find a plug that will fit this:

### 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…

### The Valentine's Day Magnetic Monopole

There's an assymetry to the form of the two Maxwell's equations shown in picture 1.  While the divergence of the electric field is proportional to the electric charge density at a given point, the divergence of the magnetic field is equal to zero.  This is typically explained in the following way.  While we know that electrons, the fundamental electric charge carriers exist, evidence seems to indicate that magnetic monopoles, the particles that would carry magnetic 'charge', either don't exist, or, the energies required to create them are so high that they are exceedingly rare.  That doesn't stop us from looking for them though!

Keeping with the theme of Fairbank[1] and his academic progeny over the semester break, today's post is about the discovery of a magnetic monopole candidate event by one of the Fairbank's graduate students, Blas Cabrera[2].  Cabrera was utilizing a loop type of magnetic monopole detector.  Its operation is in concept very simpl…