rd  - 1962 - ENC Conference

"T~L PROBE INSERT ASSEMBLY MODIFICATIONS FOR VARIAN V-4340 VARIABLE
TEMPERATURE ACCESSORY"
R. H. Elsken
Western Regional Research Laboratory, l_/ Albany, California
ABSTRACT
In our wide-line NMRwork, we need to obtain spectra of solids prepared
in sealed containers. For convenience of handling, these sealed con-
tainers should also be the NMR sample tubes.
We have modified extensively the ~.KLprobe insert for the VarianModel
V-4340 Variable Temperature NMR Probe Accessory to accept sealed samples
and, in t~e process, have also increased the filling factor by approxi-
mately h.
In brief, the supplied combination dewar probe insert and sample holders
were discarded, and techniques suggested by S. Brownstein (Can. J. Chem.,
B7, 1119, 1939) and Paul Shafer (Mellon NMR Letters, #30, April 1961)
w--~re followed to obtain a compatible system. As shown in the attached
illustration, a two-component dewar and coil insert replaces the Varian
dewar probe insert, and a 9 x 30 mm shell vial replaces the Varian sam-
ple holder. The sample tube assembly is designed to minimize vibration
with high gas flow rates.
In operation, tank nitrogen flows down between the walls of the coil
insert and dewar insert, through holes in the lower section of the coil
insert, up past the sample tube, and out the upper end of the coil insert
tubing. We have used this system primarily for low temperature work.
Average stability is + 0.5 ° C when tank nitrogen flows through a con-
stant flow regulator and copper coil -- liquid nitrogen type heat ex-
changer. Maximum flow rate is approximately 16 liters per minute for
-195 ° C sample temperature.
~/A laboratory of the Western Utilization Research and Development
Division, Agric itural Research Service, U. S. Department of Agriculture.
Reference to a company or product by name does not imply approval or recam-
mendation of the product by the Department of Agriculture to the exclusion
of others which may also be suitable.