Performing VT experiments using
400MHz DRX spectrometers
The case of lower than ambient temperature.
* Fill up the Dewar with liquid nitrogen outside of NMR laboratory.
Do not bring
any magnetic Dewars to NMR area. Follow the safety
rules with handling of
* Using gloves and eye protection insert carefully and slowly
the heater into Dewar.
Insertion should be slow enough that is no spray
of liquid nitrogen occurred outside of
Dewar. Make sure that O-ring is in proper place.
Install the clamp that connects the
heater to Dewar.
* Hook up the VT nitrogen hose to the glass Dewar in the probe.
The glass Dewar is very
fragile, please take extremely cautions while working
* Use the proper spinner turbine for VT experiments. Actually,
the gray fiber glass spinners
are design for such experiments.
* While in xwinnmr software type ‘
EDTE’ command and EDTE main
* Make sure that target sample temperature is set up to room
* Set maximum heater power to 15
. It is rather rare that higher value will be needed. Click
” and “ OK”.
* Turn “ON
” cooling. Set maximum cooling power to 35.
It is rather rare that higher value
will be needed.
* Make sure that your target temperature does not exceed the
limit of the probe
specifications. Exceeding the probe’s limit temperature
will damage the probe. Magnet
might also be damaged.
* Set the temperature 5 degree lower
than ambient and click the heater button ‘
* Wait until sample temperature will be close to target and decrease
it for the another 5
* To get to the final required temperature, proceed in the steps
of no more than 5 degree to
avoid thermal and current shock of hardware.
* While in the required temperature wait certain period of time
before you start to perform
NMR experiment to equalize the temperature across
the sample. The 20 –30 minute
period of time is usually needed. However, you may
like to find out your own waiting
ime for temperature equalization. Do not move Dewar
or touch the hose connecting it
with probe. The hose is cold and stiff and applying
force might break the probe’s glass
* After experiment is finished, decrease the cooling to
10 % and increase the temperature
in the 5degree intervals
until the room temperature is achieved. Never introduce the
thermal shock to the system by changing the temperature
with too large intervals.
* Turn off the heater by clicking heater button “
Off” in the EDTE menu.
* Turn off the cooling by clicking button “
Off ” in the EDTE menu.
* Very carefully unhook the hose from probe (first remove the
small clamp before you
touch the hose) and remove the heater from Dewar.
Remember that heater is very cold
and safety precautions for handling of liquid nitrogen
need to be observe.
* Exit the EDTE menu.
* To warm up probe’s electronic and shims to the ambient conditions
time between 30-120
minutes is needed. This depend on how long experiment
took place and what was the final temperature. Mark
your VT experiment in logbook so a next user will
be aware about previous conditions.
Consider those limitation while signing up so the
sign up policy will be obeyed.
* To find out more details, please refer to the Bruker manual
that is available in NMR