We went through the same sort of thing back in 1991.
On two of our instruments, we currently use Neslab CC-65II Immersion
Coolers with the immersion probes housed in a 0.5 in id copper tube with
the gas to be cooled fed in through a T. The assembly is insulated with two
layers of Rubratek foam insulation which runs back up the tether for 6 ft.
The basic design of this heat exchanger was modified from schematics
sent us by Professor Sykes' laboratory, and the system has proven quite
satisfactory. Our units have a 9 ft. tether (non-standard unit with special
part number of 225103230602).
On our third instrument, we have a 1982 vintage FTS FC-20-84 with their
P11-S copper tube-in-tube gas flow cooling coil. In 1991, FTS stated that all
of the engineering diagrams for the P11-S were lost in a fire in the mid 80's,
and they are no longer able to supply that style cooling coil. Therefore,
they are currently offering only their XR-85 and XR-40 at quoted prices
in excess of $5,000. These units include a temperature controller on the
refrigeration system. In 1991, they also quoted an XR-40 with the extraneous
temperature controller stripped out for around $4,000.
We found the Neslab sales force to be friendly, as well as interested in our
business and in the particular problems and concerns we had. They were
the ones that told us about the use of these units in Sykes' laboratory.
On the whole, my experiences working with Neslab were much better than
my experience trying to work with FTS.
HTH
-- Bruce D. Ray bray@indyvax.iupui.edu Operations Director NMR Center IUPUI Physics Dept. 402 N. Blackford St. Indianapolis, IN 46202-3273voice: 317-274-6914 fax: 317-274-2393