Though it will cut your conductance, the thermal load on your LN2 trap would be
reduced by the insertion of an Al foil radiation shield.  Trouble might be the
proximity of the hot top of the diff stack and the cooled baffles.  Radiative
heating will tax your cryo unnecessarily.

Regards,

Jim Russell
Sr. Scientist / Boeing
206-544-9924


-----Original Message-----
From: mems-talk-bounces+james.c.russell2=boeing.com@memsnet.org [mailto:mems-
talk-bounces+james.c.russell2=boeing.com@memsnet.org] On Behalf Of Mike Whitson
Sent: Tuesday, July 06, 2010 8:01 AM
To: General MEMS discussion
Subject: [mems-talk] Vacuum system help - voracious cold trap?

Hoping there are some more experienced vacuum engineers around this list who can
help advise regarding some antique hardware.

I'm working on an old NRC 3114 evaporator, which uses an oil diffusion pump with
an LN2 cryo trap between the diff stack and the belljar.  My problem is that the
cryo trap is being a truly monstrous consumer of LN2 - a single fill isn't
lasting more than about 30-45 minutes at most.  Does anyone have any thoughts on
1) is this "normal" behavior, and 2) what might I consider doing to increase the
run time on a single LN2 fill?

Thanks,
Mike