The problem is that it is difficult to terminate a VT run if
there is liquid nitrogen present in the delivery dewar. The
dewar must be vented, and simultaneously, the connection to the
probe must be opened. This is not trivial on the EPR probe; as
the heater assembly is very delicate, and the transfer line is
best manipulated by two people. My staff is unanimous in
the opinion that a user will break the quartz-ware in the probe
soon. We are looking at a modification that would adapt a Varian
type heat exchanger to the Bruker electronics. This modification
is a fairly extensive project.
Has anyone out there found a less far-reaching hardware
modification and/or operating procedure that would resolve this
problem?
Thanks,
Robert Santini
Department of Chemistry
Purdue University