I wonder if it is a good idea during production. We don't normally use LN2.
I think LN2 loses couple Liters a day in storage. So it might be too
wasteful.

I wonder if there is some way using the cryopump and compressor? instead of
LN2.

-Andrew

> Once the cold trap cools down it should have significant hold times -
> after all, the majority of the ln2 is within the vacuum vessel, so
> losses are limited to the heat content of the condensed species (a small
> contribution) and conduction through the connections - which attempt to
> minimize such loss.  So I'd expect several hours easily.