Tuesday, May 20, 2014

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:




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