Only the Gemini 200 in room 38 of
building 65 has the capability variable temperature (VT) capability.
The Unity 400 also has VT capability. The following precaution
should be taken when working with high temperatures. The probe
can not be used above 200°C.
-150°C. Liquid nitrogen is not required to operate
at temperatures below room temperature. Instructions are also
found in Varian manuals for Gemini System Operations on page 215
and in Gemini Accessory Installation manual beginning on page
1. The following instruction are intended to be brief instructions
for work above ambient temperatures.
CAUTION: Remember the boiling point of the common solvents
used for NMR are around 60° C, e.g. CDCl3.
If your sample is in a sealed tube around the boiling point of
the solvent the glass may shatter and contaminate the probe with
solvent, your sample, and broken glass. If the sample is not in
a sealed tube vapors from the solvent could cause damage. Plan
your VT experiments carefully. Also think about how long you
want to keep the sample at the test temperature, i.e. during
lock and shim.
1. Turn on the variable temperature controller power by pushing
the red button on the Gemini console. The VT unit should be
left off when it is not being used. When the unit is turned
on it will perform some diagnostic checks and say PASS and then
indicate the room temperature. The normal temperature is about
20.9° C. The readout will show +020.9 or whatever the values
is for current room temperature. If the reading is extremely high
or low the reading is an indication of a broken thermocouple wire
or poor connection, e.g. a reading of +209.9
2. Type CONFIG and set VTYPE to VXRSTYLE and exit
the configuration screen.
3. Load=Y SU Load=N
4. Use VTC? to make certain the transition temperature
is below room temperature, e.g 19°C.
5. Type DG to observe the temperature being set then type TEMP=25 or your selected value.
6. When you type GO or GA to begin acquisition you will
hear a click in the magnet leg and the green status light will
flash on and off and the temperature will begin to climb. We have
NMR temperature calibration standards.
7. To shut down the system go to DG and type TEMP=N and even though it probably is not necessary go to CONFIG and set VTYPE to NONE. Depress the RED power
switch on the console to turn of the VT unit and log off.
8. Repeat: Load=Y SU Load=N
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