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
   liquid nitrogen.
* 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 with it.
* 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 window appears.
* Make sure that target sample temperature is set up to room temperature.
* Set maximum heater power to 15 . It is rather rare that higher value will be needed. Click
   “Apply ” 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 ‘ ON
* Wait until sample temperature will be close to target and decrease it for the another 5
   degree.
* 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
   Dewar.
* 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 an additional
   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
   laboratory.

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