Andrew,

I think you may be speaking of a miesner trap.  You only put LN2 in it
after you are under high vacuum to gather water out of your system.  It
does not provide pumping, but will lower you pressure a bit.  It must be
completely warmed up before venting you system.

I hope you are not talking about a cold trap needed on a system with a
diffusion pump.  That needs to be filled before opening you high vac valve
to prevent oil vapor from getting into your chamber.

Brent

Andrew Xiang wrote:
> Anyone used cryocoil to speed up the vacuum pump down?
> Do I just fill it up with LN2? Never used it and don't have experience.
> I guess it will consume a lot of LN2.