[AMMRL] Prodigy: Very slow cooldown after refill of dewar - Solved

From: Kenneth Sharp-Knott <kknott_at_vt.edu>
Date: Mon, 22 Apr 2024 18:35:22 +0000

One of our Prodigy probes began to take 60-90 minutes to cooldown after a LN2
refill. Standard time previously was about 25 minutes.

Turns out this is a symptom of a slow leak in the dewar. I'm not sure exactly
where the leak was, but the following instructions were provided.

Problem is that the N2 gas pressurized loop (including the dewar ) has a small
leak . Leak is small enough manifesting itself at higher pressures ( 150 mBar)

Start with the LN2 dewar FILL port neck , peel sticker back with a sharp blade
and inspect the screws for tightness.

NOTE: These screws are small and soft and easily stripped.

I also cleaned and reseated the O-rings at the dewar neck.


In any case, after this, the cooldown was completed in 25 minutes are previously.


Some may be wondering when this question was posed to the list. This is a
very rare example of an issue I solved without requiring the collective genius
of the AMMRL userbase.

Ken Sharp-Knott
Manager of Analytical Services and the NMR Facility
Department of Chemistry
Virginia Tech

(540)267-6502 (Cell)
(540)231-0885 (Office)


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Received on Mon Apr 22 2024 - 11:37:33 MST